Rob Vincent -- Distributed Load Monopole Antenna


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**Rob VINCENT**

**Distributed Load Monopole ( DLM ) Antenna**

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![](robvincent.gif)

**Robert Vincent**

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[**http://www.wirelessnetdesignline.com/showArticle.jhtml?articleID=163103803**](http://www.wirelessnetdesignline.com/showArticle.jhtml?articleID=163103803)  
[**http://www.eetimes.com/;jsessionid=X2ETTT3FGOTKMQSNDLRCKHSCJUNN2JVN**](http://www.eetimes.com/;jsessionid=X2ETTT3FGOTKMQSNDLRCKHSCJUNN2JVN)

**Tweak to Inductive Loading Shrinks Antenna**

**By**

**R. Colin Johnson**

PORTLAND, Ore.  Independent tests appear to support an
inventor's claim that his skunk-works antenna design can shrink
antenna size by up to 70 percent while maintaining equivalent
sensitivity and increasing bandwidth.

**The four-part antenna cancels out the normal inductive
loading in traditional antenna designs, thereby linearizing
the energy radiation along its mast and enabling its
diminutive size.**

"When we announced my smaller antenna design last year, I got
lots of doubting Thomases worldwide. Now, with the help of the
Naval Undersea Warfare Center and its antenna test range on
Fishers Island, N.Y., we have independent test results to back
up our claims," said inventor Rob Vincent, a research engineer
in the University of Rhode Island's physics department.

Vincent calls his invention a distributed-load monopole (DLM)
antenna. The novel design uses a helix plus a load coil to
shrink the size of a normal quarter-wave monopole. According to
Vincent, his design can shrink the size of every antenna in use
today, from the tiny gigahertz units inside cell phones to
giant, kilohertz AM antennas. For instance, a 3-inch-long
gigahertz antenna could be shrunk to an inch, and a
300-foot-tall AM band antenna could be reduced to 80 feet high.

In the tests, various DLM antennas from Vincent's portfolio
were tested from 7 to 27 MHz. The results indicated that
equivalent performance was achieved with antennas 30 to 70
percent shorter than an ideal quarter-wave antenna.

"Basically I am utilizing the distributed capacitance around
the antenna to reduce the normally required inductive loading,"
Vincent said.

Vincent spent almost 30 years at Raytheon Co. and at KVH
Industries (Middletown, R.I.), before becoming a research
engineer at the University of Rhode Island (Kingston). He began
experimenting with antennas there as a skunk-works project.

Vincent chose the Navy's Fishers Island Antenna Complex to test
his design because it is located in a low-lying, remote coastal
area free from radiation obstructions and man-made
electromagnetic interference. The complex offers a 1-mile range
over seawater between two sites for testing antennas ranging in
frequency from 2 to 30 megahertz. All gain measurements were
done relative to an ideal quarter-wave monopole antenna.

Vincent's antenna designs were tested using the official regime
the Navy uses to certify its antennas. Vincent's Plano Spiral
Top Hat antenna, at 7 MHz, was shown to have equal sensitivity
to a normal quarter-wave antenna but at 50 percent the
quarter-wave unit's size. In addition, bandwidth of the Vincent
design was nearly twice as wide as that of the quarter-wave
unit.

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[**http://lists.contesting.com/pipermail/topband/2005-August/022116.html**](http://lists.contesting.com/pipermail/topband/2005-August/022116.html)

**Topband: May 2005 EET article about the DLM**

**Tom Rauch w8ji at contesting.com**

( Aug 20 07 )

The test antenna was a 7MHz monopole, 50% of the normal 
quarter-wave size. Now one thing from an illustration that begs
more information was the ground system. It shows 150' radials,
which appear to terminate at the sea water's edge. There is
about a mile of seawater between the test antenna and the
calibrated receive antenna.

The article concludes; "Vincent's antenna designs were tested
using the official regime the Navy uses to certify antennas.
Vincent's Plano Spiral Top Hat antenna, at 7MHz, was shown to
have equal sensitivity to a normal quarter-wave antenna but at
50% the quarter-wave unit's size. In addition, bandwidth of the
Vincent design was nearly twice as wide as that of the
quarter-wave unit."

The initial Vincent claim read almost like CFA, CTHA, Fractal,
and E-H antenna claims. A very short antenna with makeshift
construction was claimed to produce better than full size
performance. The claims have evolved now to 50% shortening over
a nearly perfect ground produces equal FS.

The difference in FS between a conventional 1/4 wl tall antenna
and a 1/8th wl tall antenna is within measurement error when the
antenna is over a very good ground system and when it uses a
good loading inductor regardless of where loading is placed.
Brown, Lewis, and Epstein knew that in the 1930's.

As a matter of fact even with a loading coil Q as low as 250
(typically like air core #16 wire) and using base loading there
is less than 1dB difference between a 1/8th wave and quarter
wave antenna!

The apparent endorsement of the DLM antenna by the U of RI does
prove one thing....we need to work on our  educational
system and stop the backslide in science. The U of RI and
Vincent are now at the level of early 20th century antenna   
technology.

73 Tom

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[**http://www.ieee.org/portal/pages/products/whats-new/wncomm/wncomm0605.html**](http://www.ieee.org/portal/pages/products/whats-new/wncomm/wncomm0605.html)

**ENGINEER DRASTICALLY SHRINKS ANTENNA, MAINTAINS
SENSITIVITY AND BANDWIDTH**

A research engineer at the University of Rhode Island has
invented an antenna 70 percent smaller than conventional
designs, but which has comparable sensitivity and increased
bandwidth. The antenna, called a distributed-load monopole
(DLM), uses a helix and a load coil to shrink the size of a
normal quarter-wave monopole. In testing research engineer Rob
Vincent's antenna design, which cancels out the normal inductive
loading, the U.S. Navy found that the antenna achieved
equivalent performance with antennas 30 to 70 percent shorter
than an ideal quarter-wave design. Read more:

[**http://****www.wirelessnetdesignline.com/showArticle.jhtml?articleID=163103803**](http://www.wirelessnetdesignline.com/showArticle.jhtml?articleID=163103803)

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[**http://www.eetimes.com/showArticle.jhtml?articleID=21600147**](http://www.eetimes.com/showArticle.jhtml?articleID=21600147)

**Antenna design boosts efficiency per given
size**

**R. Colin Johnson**   
EE Times   
(06/14/2004 9:00 AM EST)

Portland, Ore. - A four-year skunk works effort at the
University of Rhode Island in Kingston has cut the size of an
antenna by as much as one-third for any frequency from the kHz
to the GHz range. Using conventional components, the four-part
antenna design cancels out normal inductive loading, thereby
linearizing the energy radiation along its mast and enabling the
smaller size.

"The DLM [distributed load monopole] antenna is based on a lot
of things that currently exist," said the researcher who
invented the smaller antenna, Robert Vincent of the university's
physics department, "but I've been able to put a combination of
them together to create a revolutionary way of building
antennas. It uses basically a helix plus a load coil."

The patent-pending design could transform every antenna-from
the GHz models for cell phones to the giant, kHz AM antennas
that stud the high ground of metropolitan areas-Vincent said.

For cell phones, for example, Vincent said he has a completely
planar design that is less than a third the size of today's cell
phone antennas. And those 300-foot tall antennas for the 900-kHz
AM band that dominate skylines would have to be only 80 feet
high, with no compromise in performance, using Vincent's design,
he said.

"When looking at these antennas, you pretty much have to forget
everything you ever knew about antennas and keep an open mind,
because some of the things I have done are very radical," said
Vincent. "With my technique, I reduce the inductive loading that
is normally required to resonate the antenna by as much as 75
percent . . . by utilizing the distributed capacitance around
the antenna."   
NIMBY factor   
Vincent, an amateur radio operator, embarked on his project
after he moved to a new neighborhood and his neighbors objected
to the 140-foot tall antenna he planned to erect for a
quarter-wave 1.8-MHz transmitter. So he surveyed the literature,
took the best of the best designs and combined them into a
21-MHz test antenna that was 18 inches high, as opposed to the
12- to 24-foot height of the antennas normally used for that
band. Building on that work, he eventually devised a
46-foot-tall 1.8-MHz antenna his neighbors could accept.

"I looked at all the different approaches used to make antennas
smaller, and there seemed to be good and bad aspects" to each,
Vincent said. "A helix antenna is normally known to be a core
radiator, because the current profile drops off rapidly; they
are just an inductor, and inductance does not like to see
changes in current, so it's going to buck that. "But what I
found was that for any smaller antenna, if you place a load coil
in the middle you can normalize and make the current through the
helix unity; that is, you can maximize it and linearize it."

Vincent has verified designs from 1.8 MHz to 200 MHz by
measuring and characterizing the behavior of his DLM antenna
compared with a normal quarter-wave antenna of the same
frequency. He found that many of the disadvantages of
traditional antennas were not problems for the much lighter
inductive loading in a DLM.

"For instance, in a normal quarter-wave antenna the current
continually drops off in a sinusoidal shape, but these antennas
don't do that," said Vincent. "The current at the top of the
antenna is 80 percent of the current at the base."

The reason more current can be pumped into a DLM design than in
a conventional equivalent at the same size, Vincent theorized,
is that the DLM distributes energy more evenly along the
antenna's length. Using a DLM antenna one-third to one-ninth the
size of standard quarter-wave antenna, he measured nearly 80
percent efficiency, when conventional wisdom would dictate that
an antenna the size of a DLM should be only 8 to 15 percent
efficient.

To check his theory, Vincent analyzed and compared the current
profiles, output power and a score of other standard tests for
measuring antenna performance. All measurements were in
reference to comparative measurements made on a quarter-wave
vertical antenna for the same frequency, on the same ground
system and same power input.

"I was able to increase the current profile of the antenna over
a quarter-wave by as much as two to 2.5 times," said Vincent.
"That is, the magnitude of the current in these antennas is two
to 2.5 times larger than for a normal quarter-wave antenna.

"However, if you measure the current profiles for both antennas
and integrate the area under the curves, you come out with the
same volume, indicating that the much smaller antenna is filling
the airwaves with the same amount of radio energy."

Vincent plans to publish the results in a scientific journal
soon, but with a patent decision imminent, he couldn't hold off
a preliminary announcement that his theories regarding DLM
antennas were being supported by the experimental results.
According to the researcher, the DLM antenna profiles look just
like the theoretically ideal antenna profile-operating on a
single frequency with very high efficiency, while not producing
any interfering frequencies or wasting thermal energy.

"The phase and amplitude of this antenna are a perfect mimic of
the universal resonance curve," said Vincent. "This makes the
antenna completely predictable well beyond its bandwidth.
Another unique feature is that these antennas have no harmonic
response whatsoever; as a matter of fact, to a certain extent I
used filter synthesis to design the antennas."   
Nondescript   
To the naked eye, the DLM antenna looks unremarkable, said
Vincent, who jokes that you could put a flag on his antennas and
they would look like flagpoles. But under the skin are four main
sections to the antenna (from bottom to top): an inductive
helix, a capacitive midsection, an inductive load coil and a
capacitive top section. The different lengths of the mid- and
top sections give them different resonant frequencies, which,
together with the exact values of inductance and capacitance,
define the antennas design specifications for any desired
frequency.

"The technology is completely scalable: Take the component
values and divide them by two, and you get twice the frequency;
take all the component values and multiply them by two, and you
are at half the frequency," said Vincent. "There are two poles
in the antenna, and where I place the poles in relation to one
another-how much I bring the two resonant frequencies together
or spread them apart-enables me to emulate different antennas,
from a quarter-wave to a five-eighths wave."

Vincent said no existing modeling software could adequately
model his antenna design. So he rolled his own simulation with
Mathcad, making use of some of Mathcad's filter design
algorithms for the inductive/capacitive-canceling effect.

"Eight years ago, antenna design was 90 percent black magic and
10 percent theory," said Vincent. "But now, with my design, they
are 10 percent black magic and 90 percent theory."

The antennas are also well-behaved, with wide bandwidth and
easy to connect to standard equipment, according to Vincent. For
instance, they can directly connect to standard 50-ohm antenna
inputs without any adapters.

"All I have to do is tap the helix at its base, and you get a
perfect 50-ohm match with out any lossy networks [as are
required for other advanced antenna designs]," said Vincent.

For the future, Vincent is moving up into the GHz bands for use
with cell phones and radio-frequency ID equipment. A problem in
the past has been that as components are downsized, they become
too small to utilize standard antenna materials. At 1 GHz, for
example, the helix is only eight-thousandths of an inch in
diameter and requires more than 100 turns of wire.

"So I came up with a new way of developing a helix for high
frequencies that is a fully planar design; it's a
two-dimensional helix," said Vincent.

With the new helix design, Vincent has built a prototype 7-GHz
antenna that he claims is indistinguishable from a quarter-wave
antenna in all but its size. "Because the new design is
completely planar, we could crank these out using thin-film
technologies," Vincent said.

Vincent received the 2004 Outstanding Intellectual Property
Award from the University of Rhode Island's Research Office,
joint applicant for the patent.

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[**http://www.newswise.com/articles/view/511437/**](http://www.newswise.com/articles/view/511437/)

**Navy Gives Small Antenna Big Results**

Newswise  The news last June that Rob Vincent, an employee in
the Physics Department at the University of Rhode Island, had
shrunk the antenna size without shrinking its effectiveness,
produced a large group of Doubting Thomases worldwide. Prove it,
they demanded.

Vincent and URI, with the help of the Naval Undersea Warfare
Center and its antenna test range on Fishers Island, N. Y., have
done just that.

On March 31, 14 versions of Vincents Distributed Load Monopole
(DLM) antennas were put through a battery of validation tests.
The results exceeded Vincents and URIs expectations. Smaller
is better.

The Navy center responds to a wide variety of military and
commercial requests for testing antennas at its Fishers Island
over water range, the only such range of its kind in the world.
Water provides a better path for transmission and reception than
land. The site is located on a low-lying, remote coastal area,
free of local interference.

The Fishers Island range is a far-field ground wave antenna
test range capable of measuring the performance of antennas
ranging in frequency from 2 to 30 megahertz. Gain measurements
are done relative to an ideal quarter wave monopole antenna. The
URI antennas were tested using the same methods and
instrumentation as those used to test and certify Navy antenna
systems.

Industry regards such testing as dependable as science permits
and often includes the centers data with products to assure
customers of its performance specifications.

Vincents Plano Spiral Top Hat antenna at 7 megahertz is half
the size of a normal quarter-wave antenna operating at that
frequency. The URI antenna gain matched the performance of the
ideal quarter-wave antenna, and its bandwidth was nearly twice
as wide. This type of antenna has multiple uses, including
military, marine, amateur radio communications and AM
broadcasting.   
In addition, the gain of Vincents capacity Top Hat DLM antenna,
which incorporates a helix, a load coil, a capacitive top hat
utilizing radial spokes at the top of the antenna and a
horizontal plane was nearly identical to the ideal quarter wave
antenna. Its bandwidth was greater than 5 percent of the
operating frequency and the antenna is more than 70 percent
shorter than an ideal quarter wave antenna.

Vincents standard DLM antennas with a standard helix and load
coil were also tested at various frequencies. All exhibited
gains nearly equal to the ideal antenna with bandwidths of 3 to
10 percent. The antennas were 33 to 40 percent shorter.

More than 200 businesses, companies, and government agencies
have contacted URI seeking information for automotive, marine,
and military applications, among others, since the antenna
announcement last year. A patent is pending on Vincent's
technology. The inventor has made the University of Rhode Island
and its Physics Department partners that will benefit from any
revenue his invention earns.

URI is close to securing several license agreements. In
addition, prototypes have been developed for numerous
applications.

View the test data on URIs antenna technology online. Visit
the U.S. Navys testing facility online for more information.

---

[**http://www.electronicproducts.com/ShowPage.asp?FileName=olrr01.aug2005.html**](http://www.electronicproducts.com/ShowPage.asp?FileName=olrr01.aug2005.html)

**Antenna Technology Shrinks Size, Not
Effectiveness**

by

**Ralph Raiola**

Tests at the Naval Undersea Warfare Center's antenna test range
have shown that a new antenna technology, dubbed Distributed
Load Monopole (DLM), can shrink antenna sizes without loss of
performance. Developed last year by Rob Vincent, a technician in
the University of Rhode Island's physics department, the
technology could produce chip-mountable cell-phone antennas that
can be applied to WLAN applications, and promises to at least
double the range of walkie-talkies used by police, fire, and
other municipal personnel.

The DLM antenna technology promises antennas up to 70% shorter
than an ideal quarter-wave antenna.

Several versions have been developed, including the Plano
Spiral Top Hat, a 7-MHz version that is half the size of normal
quarter-wave devices operating at that frequency. The device's
gain matched the performance of the ideal quarter-wave antenna,
and its bandwidth was nearly twice as wide.

The Top Hat DLM antenna incorporates a helix, load coil, and
capacitive top hat using radial spokes at the top. More than 70%
shorter than an ideal quarter-wave antenna, its bandwidth is
greater than 5% of the operating frequency.

Standard versions featuring a standard helix and load coil were
also tested at various frequencies, all exhibiting gains nearly
equal to the ideal antenna with bandwidths of 3% to 10%. The
antennas were 33% to 40% shorter.

The technology is also being focused toward applications such
as naval ships, baby monitors, RFID, and portable antennas for
military equipment. The university is close to securing several
license agreements and prototypes have been developed for
numerous applications. For more information, call Rob Vincent of
the University of Rhode Island at 401-874-2063 or visit  **<http://www.uri.edu/news/vincent/report05>**

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[**http://www.uri.edu/news/vincent/report05**](http://www.uri.edu/news/vincent/report05)

**Table of Contents:** Test Report --  **<http://www.uri.edu/news/vincent/report05/testreport.pdf>**
  
NUWC Report  --  **<http://www.amta.org/StaticFiles/PDF/amta_2002/session%2013/a2002-13-02-072.pdf>**
  
Antenna Test Data (.zip) --  **<http://www.uri.edu/news/vincent/report05/data.zip>**

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**US Patent # 7,187,335**

**System and Method for Providing a
Distributed Loaded Monopole Antenna**

**Robert J. Vincent**

**( March 6, 2007 )**

**Abstract --** A distributed loaded antenna system
including a monopole antenna is disclosed. The antenna system
includes a radiation resistance unit coupled to a transmitter
base, a current enhancing unit for enhancing current through the
radiation resistance unit, and a conductive mid-section
intermediate the radiation resistance unit and the current
enhancing unit. The conductive mid-section has a length that
provides that a sufficient average current is provided over the
length of the antenna.

US Cl. **343/722** ; 343/749; 343/841   
Intl. Cl. **343/722** ; 343/749; 343/841

**References Cited:**   
**U.S. Patent Documents:** 3984839 // 4095229 // 4229743 //
4442436 // 4564843 // 4734703 // 5016021 // 5065164 // 5134419
// 5406296 // 5521607 // 5856808 // 5955996 // 6054958 //
6208306 //   
6437756 // 6791504

**Other References:**

Harrison, Jr., "Monopole with Inductive Loading," IEEE
Transactions on Antennas and Propagation, Sandia Corporation,
Albuquerque, NM, Dec. 26, 1962, pp. 394-400. cited by other .   
Fujimoto et al., "Small Antennas," Research Studies Press Ltd.,
Letchworth, Hertfordshire, England & John Wiley & Sons
Inc., New York, 1987, pp. 59-75. cited by other .   
"Now You're Talking!: All You Need to Get Your First Ham Radio
License," The American Radio Relay League, Inc., Second Edition,
Apr. 1996, Chapter 7, pp. 16-17. cited by other .   
"The Offset Multiband Trapless Antenna (OMTA)," QST, vol. 79,
No. 10, American Radio Relay League, Inc., 1996, pp. 1-11. cited
by other .   
"Mounting Tips for the Stealth II Series HF Mobile Antennas,"
Version 3.32, Aug. 2002, pp. 1-9. cited by other .   
Nakano et al., "A Monofilar Spiral Antenna Excited Through a
Helical Wire," IEEE Transactions of Antennas and Propagation,
vol. 51, No. 3, Mar. 2003, pp. 661-664. cited by other .   
"Helix Antenna,"
http://library.kmitnb.ac.th/projects/eng/EE/ee0003e.html, no
dated?. cited by other .   
T. Simpson, "The Dick Loaded Monopole Antenna," IEEE
Transactions of Antennas and Propagation, vol. 52, No. 2, Feb.
2004, pp. 542-545. cited by other.

***Description***

**BACKGROUND**

The present invention generally relates to antennas, and
relates in particular to antenna systems that include one or
more monopole antennas.

Monopole antennas typically include a single pole that may
include additional elements with the pole. Non-monopole antennas
generally include antenna structures that form two or three
dimensional shapes such as diamonds, squares, circles etc.

As wireless communication systems (such as wireless telephones
and wireless networks) become more ubiquitous, the need for
smaller and more efficient antennas such as monopole antennas
(both large and small) increases. Many monopole antennas operate
at very low efficiency yet provide satisfactory results. In
order to meet the demand for smaller and more efficient
antennas, the efficiency of such antennas must improve.

There is a need, therefore, for more efficient and cost
effective implementation of a monopole antenna, as well as other
types of antennas and antenna systems.

SUMMARY OF THE INVENTION

In accordance with an embodiment, the invention provides a
distributed loaded antenna system including a monopole antenna.
The antenna system includes a radiation resistance unit coupled
to a transmitter base, a current enhancing unit for enhancing
current through the radiation resistance unit, and a conductive
mid-section intermediate the radiation resistance unit and the
current enhancing unit. The conductive mid-section has a length
that provides that a sufficient average current is provided over
the length of the antenna.

**BRIEF DESCRIPTION OF THE DRAWINGS**

The following description may be further understood with
reference to the accompanying drawings in which:

**FIG. 1** shows a diagrammatic illustrative electrical
schematic view of a distributed loaded monopole antenna in
accordance with an embodiment of the invention;

![](fig1.jpg)

**FIG. 2** shows a diagrammatic illustrative side view of a
distributed loaded monopole antenna in accordance with an
embodiment of the invention;

![](fig2.jpg)

**FIG. 3** shows a diagrammatic illustrative graphical view
of average current distribution over length of an antenna in
accordance with an embodiment of the invention;

![](fig3.jpg)

**FIG. 4** shows a diagrammatic illustrative top view of a
top unit for use in accordance with an embodiment of the
invention;

![](fig4.jpg)

**FIG. 5** shows a diagrammatic illustrative side view of an
antenna in accordance with an embodiment of the invention
employing a top unit as shown in FIG. 5;

![](fig5.jpg)

**FIG. 6** shows a diagrammatic illustrative top view of
another top unit for use in an antenna in accordance with a
further embodiment of the invention;

![](fig6.jpg)

**FIG. 7** shows a diagrammatic illustrative side view of a
radiation resistance unit for use in an antenna in accordance
with an embodiment of the invention;

![](fig7.jpg)

**FIG. 8** shows a diagrammatic illustrative side view of an
adjustment unit for use in an antenna in accordance with an
embodiment of the invention;

![](fig8-10.jpg)

**FIG. 9** shows a diagrammatic illustrative side view of
the slotted tube shown in FIG. 8;

**FIGS. 10A and 10B** show diagrammatic illustrative side
views of the tapered sleeve shown in FIG. 8;

**FIG. 11** shows a diagrammatic illustrative side view of
another adjustment unit for use in an antenna in accordance with
an embodiment of the invention;

![](fig11-13.jpg)

**FIG. 12** shows a diagrammatic illustrative side view of
the slotted tube shown in FIG. 11;

**FIG. 13** shows a diagrammatic illustrative side view of
the sleeve shown in FIG. 11;

**FIG. 14** shows a diagrammatic illustrative isometric view
of a radiation resistance unit for use in an antenna in
accordance with an embodiment of the invention;

![](fig14.jpg)

**FIGS. 15A, 15B and 15C** shows diagrammatic illustrative
isometric, front and side views of a current enhancing unit for
an antenna in accordance with an embodiment of the invention;

![](fig15.jpg)

**FIGS. 16 and 17** show diagrammatic illustrative side
views of antennas in accordance with further embodiments of the
invention employing the radiation resistance unit shown in FIG.
14;

![](fig16-17.jpg)

**FIG. 18** shows a diagrammatic illustrative isometric view
of a plurality of monopole antennas in accordance with the
invention being used together in a multi-frequency system;

![](fig18-19.jpg)

**FIG. 19** shows a diagrammatic illustrative electrical
schematic of a portion of the system shown in FIG. 18;

**FIG. 20** shows a diagrammatic illustrative side view of
an antenna in accordance with an embodiment of the invention
that forms a loop antenna system;

![](fig20.jpg)

**FIG. 21** shows a diagrammatic illustrative side view of
an antenna in accordance with an embodiment of the invention
that forms a dipole antenna system;

![](fig21.jpg)

**FIG. 22** shows a diagrammatic illustrative electrical
schematic of an antenna in accordance with an embodiment of the
invention;

![](fig22.jpg)

**FIG. 23** shows a diagrammatic illustrative side view of
an antenna in accordance with an embodiment of the invention;
and

![](fig23.jpg)

**FIGS. 24, 25 and 26** show diagrammatic illustrative side
views of antennas in accordance with further embodiments of the
invention;

![](fig24-26.jpg)

The drawings are shown for illustrative purposes only.

**DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS**

A distributed loaded monopole antenna in accordance with an
embodiment of the invention includes a radiation resistance unit
for providing significant radiation resistance, and a current
enhancing unit for enhancing the current through the radiation
enhancing unit. In certain embodiments, the radiation resistance
unit may include a coil in the shape of a helix, and the current
enhancing unit may include load coil and/or a top unit formed as
a coil or hub and spoke arrangement. The radiation resistance
unit is positioned between the current enhancing unit and a base
(e.g., ground), and may, for example, be separated from the
current enhancing unit by a distance of
2.5316.times.10.sup.-2.lamda. of the operating frequency of the
antenna to provide a desired current distribution over the
length of the antenna.

As shown in FIG. 1, an electrical schematic diagram of an
antenna 10 in accordance with an embodiment of the invention
includes a radiation resistance unit 12 and a current enhancing
unit 14. The radiation resistance unit 12 (such as, for example,
a helix) may be formed in a variety of shapes, including but not
limited to round, rectangular, flat and triangular. The
radiation resistance unit 12 may be wound with wire, copper
braid or copper strap or other conductive material around the
form and is such that it's length is very much longer than it's
width or diameter.

The current enhancing unit 14 may also be formed of a variety
of conductive materials and may be formed in a variety of
shapes. The unit 14 is positioned above the unit 12 and is
separated a distance above the unit 12 and supported by a
mid-section 16 (e.g., aluminum tubing). The current enhancing
unit 14 when placed a distance above the radiation resistance
unit 12 performs several important functions. These functions
include raising the radiation resistance of the helix and the
overall antenna.

The above antenna provides continuous electrical continuity
from the base of the helix to the top of the antenna. The base
of the antenna is grounded as shown at 18, and the signal to be
transmitted may be provided at any point along the radiation
resistance unit 12 (e.g., near but not at the bottom of the unit
12). The signal may also be optionally passed through a
capacitor 22 in certain embodiments to tune out excessive
inductive reactance as discussed further below.

FIG. 2 shows an implementation of the above antenna system in
which the radiation resistance unit is formed as a helix 30, and
the current enhancing unit is formed as a load coil 32. The
helix 30 is formed as a conductive coil that is wrapped around a
non-conductive cylinder wherein the coil windings are mutually
spaced from one another by a distance of approximately the
thickness of the coil. The bottom of the helix coil is connected
to ground as shown at 34, and the top of the helix coil is
connected to a conductive mid-section 36 between the helix 30
and the load coil 32. The load coil is formed as a tightly
wrapped spiral, the base of which is connected to the
mid-section 36 and the top of which is connected to a
top-section 38. The mid-section 36 may separate the helix 30 and
load coil 32 by a distance as indicated at A. The signal to be
transmitted is coupled to the antenna by a coaxial cable 40
whose signal conductor is coupled to one of the lower helix coil
windings near the base as shown at 42, and whose outer ground
conductor is coupled to ground as shown.

The choice of the distance A of the load coil above the helix
impacts the average current distribution along the length of the
antenna. As shown in FIG. 3, the average current distribution
over the length of the antenna varies as a function of the
mid-section distance for a 7 MHz distributed loaded monopole
antenna. The mid-section distance is shown along the horizontal
axis in inches, and the percent of average current over the
antenna length is shown along the vertical axis. The
relationship between the mid-section distance and the percent of
average current is shown at 50 for this antenna. The current
distribution for this antenna peaks at about 42 inches as shown
at 52. The conductive mid-section has a length that provides
that a sufficient average current is provided over the length of
the antenna and provides for increasing radiation resistance to
that of 2 to nearly 3 times greater than a 1/4.lamda. antenna
(i.e., from for example, 36.5 Ohms to about 72 100 Ohms or
more).

The inductance of the load coil should be larger than the
inductance of the helix. For example, the ratio of load coil
inductance to helix inductance may be in the range of about 1.1
to about 2.0, and may preferably by about 1.4 to about 1.7. In
addition to providing an improvement in radiation efficiency of
a helix and the antenna as a whole, placing the load coil above
the helix for any given location improves the bandwidth of the
antenna as well as improving the radiation current profile. The
helix and load coil combination are responsible for decreasing
the size of the antenna while improving the efficiency and
bandwidth of the overall antenna.

In further embodiments, a top unit 60 may also be provided that
includes eight conductive spokes 62 that extend from a
conductive hub 64 as shown in FIG. 4. The spokes 62 may be held
within small holes by set screws through which they are
electrically connected to the conductive top-section 38 of the
antenna. As shown in FIG. 5, the top unit 60 may be placed atop
an antenna such as the antenna shown in FIG. 2. This may further
reduce the inductive loading of the helix and load coil to allow
even wider bandwidth and greater efficiency. The top unit is
included as part of the current enhancing unit. In further
embodiments, the top unit may be used in place of the load coil
as the current enhancing unit.

A current profile for a 12 foot antenna employing a helix and
load coil (starting at 7.5 feet) was found to show 100 percent
current up to an elevation of about 7 feet, while a similar 9.5
foot antenna using an additional top unit was found to show 100
percent current up to an elevation of about 8 feet. The
structure provides electrical continuity from the base of the
helix to the top of the top section. The top unit may, in
further embodiments, include a planar spiral winding that
extends radially from, and in a transverse direction with
respect to, the antenna as discussed below in connection with
FIG. 6.

There is an electrical connection from the bottom of the helix
up through the helix and through the midsection and continues
through the load coil to the top section. The helix at the
bottom has provisions for tapping the turns of the helix. This
allows connection from a source of radio frequency energy and
proper matching by selecting the appropriate tap to facilitate
maximum power transfer from the radio frequency source to the
antenna. The placement of the load coil provides linear phase
and amplitude responses through the bandwidth of the antenna and
even beyond the normally usable bandwidth of the antenna. It has
also been found that such an antenna has no harmonic response,
and that its response is similar to that of a low Q band pass
filter.

The antenna shown in FIG. 2 may be mounted by clamping the base
of the helix to a mounting pole that has been driven into the
ground. Clamps may be used to affix the antenna sufficiently to
the ground mounting post. In this embodiment the antenna is
shown grounded to earth through a grounding rod, ground wire and
connected to the base of the antenna and electrically connected
using a ground clamp. Radial wires extending above ground or
buried in the ground are electrically connected to the antenna
using the ground wire and the ground rod and extend out from the
antenna base for a uniform distance but not limited to any
specific length. This grounding system comprised of a ground rod
and radial wires may also take on many forms such as a large
piece of copper or other conductor screen of any given geometric
shape. This grounding system may also take on the form of a
metal plane such as a ship, automobile, or a metal roof of a
building among others. The antenna may also be elevated above
ground on a conductive post with radial wires extended as guy
wires to support and keep antenna in the upward erect position.
These guy wires serve as an elevated ground poise or radial
system.

The feed for the antenna from a radio frequency source is
tapped a few turns from the base of the helix driven by a radio
frequency source and connected by a coax cable. The shield of
the coax cable is connected to the base of the helix which is
grounded to the ground rod. The radio frequency source is used
to excite the antenna and cause a radio frequency current to
flow which causes the distributed loaded monopole antenna to
radiate.

As indicated above, the design of the helix and interaction of
the load coil are such that the antenna exhibits a large and
uniform current distribution for various lengths along the
antenna. The length and uniformity of this current profile is
dependent upon the ratios of inductance between the load coil
and the helix as well as location of placement of the load coil
above the helix. In addition, the placement of the load coil
allows larger than normal bandwidth measured as deviation from
resonant frequency either side of resonance in which sufficient
match between the source of radio frequency energy and the
antenna can be maintained to allow the antenna to radiate with
reasonable efficiency. In addition, the interaction of the helix
and load coil allows reduction of the physical height of the
overall antenna without reducing electrical height and provides
for an increase in radiation resistance. This increase in
radiation resistance reduces the effect of losses associated
with short antennas. These losses include resistance in the
wires of the helix and load coil and Ohmic resistance of the
antenna conductors and that of the ground system. All or any of
these has a pronounced effect on antenna radiating efficiency,
reduction of antenna bandwidth and overall performance in
shortened antennas. The design of the distributed loaded
monopole antenna with a helix and load coil above the helix
overcomes those losses and provides a high level of radiating
efficiency with excellent bandwidth in a small compact easily
implemented antenna.

The physical structure of an antenna and the interaction of the
components as described above allow for maximum use of
distributed capacity along the antenna to ground to reduce
inductive loading required to resonate the antenna to a given
desired radio frequency. This increases efficiency, raises
radiation resistance and improves bandwidth. This also allows
the antenna to have amplitude and phase response through
resonance that resembles a universal resonance response curve
with linear deviations in amplitude and phase for bandwidths far
exceeding the normal half power bandwidth of the antenna.

The antenna of FIG. 5 may be formed as follows. A helix is
formed by wrapping a conductive material around a tubular
non-conductive form, such as fiberglass, PVC or other suitable
tubular insulator. In further embodiments, any form may be used
such as those that are also square, rectangle or triangular in
cross section. Attached to the top of the helix is a top fitting
that is formed of a conductive material such as aluminum or
other suitable conductive material. In this embodiment these are
machined but can also be cast from aluminum or other suitable
conductive material. Slots are cut in the top fitting to allow
clamping on to a aluminum tubing of such diameter that they form
a tight mechanical fit when such tubing is inserted. This
fitting is inserted into the helix tube and in this embodiment
is epoxy bonded together with the helix and fitting. It may also
be fastened with machine screws provided the helix form is
drilled and the fitting has been drilled and threaded. Likewise
a bottom helix fitting is machined or cast of aluminum or other
conductive material is attached to bottom of helix. This fitting
is solid aluminum and has mounting rod. A helix insertion rod
has been epoxy bonded to the helix form. The main section forms
a conductive mounting point for this lug and helix winding. A
helix winding is attached at the base fitting with a solder lug
or other conductive connecting material and fastened
electrically and mechanically to the helix end fitting with a
machine screw. The helix is wound with copper strap but not
limited to this material but can be wire or copper braid wound
in a circular manner over the entire length of the helix form
and attached to the helix top fitting using, for example, a
solder lug. Other conductive connecting devices may be used to
allow electrical and mechanical assembly with a machine screw
into the drilled and threaded hole. The helix at the bottom has
machine nuts or similar connecting devices soldered to the
winding for attachment of the center conductor of a coax cable.

Inserted into the top of the helix fitting is a tubing that is
held rigidly in the helix top fitting using a clamp. The load
coil includes a section of fiberglass tubing that is attached
with end fittings that are epoxy bonded to form a strong
mechanical connection with both the mid-section and the
top-section. The load coil end fittings are machined or cast
aluminum. Each of these fittings is slotted and formed, or
machined to accept mid-section tubing or top section tubing,
which are electrically connected to the load coil itself. The
load coil form is wound with heavy copper wire but may be any
other heavy conductive material that is closely wound as shown
to form a solenoid. Each end is connected to the load coil end
fitting with a lug on each end, and attached electrically and
mechanically with machine screws that are screwed into holes
that have been drilled and threaded into load coil end fittings.
Two pieces of tubing form the top section. The lower tube
section at the top has been slotted to allow the upper tubing
section to be inserted in a telescoping manner into tubing
section to permit adjustment of the overall top section length
to tune the antenna. Once adjusted, the tubing sections are
secured with a clamp to form a rigid mechanical and electrical
connection. There is now an electrical connection from the
bottom of the helix winding from the helix bottom fitting to the
top of the top section.

The completed distributed loaded monopole antenna consisting of
the helix 30, the mid-section 36, the load coil 32 and the top
section 38 is shown in FIG. 5 mounted on a ground mounting pipe
of conductive material using clamps. The coax cable with a
center conductor is shown connected to one of the tap points at
bottom of helix. The coax shield is electrically connected to
the helix base fitting with an electrical clamp. The ground wire
34 is connected to the electrical clamp (and therefore to the
ground base of helix) and to a ground rod 44 in the ground.
Attached to the ground rod 44 and ground wire are radials 46
that are either buried or lying on the ground. The radials 46
may be of sufficient length and number to provide an adequate
counterpoise for operation of the distributed loaded monopole
antenna.

The hub 64 of the hub and spoke top unit 60 shown in FIG. 4 may
be fabricated from an aluminum disk of sufficient size to
accommodate the eight radial aluminum conductors or spokes 62.
To use the top unit 60, the normal antenna design inductance for
the helix and load coil must be decreased by 1/2 in order to
resonate the antenna to the same frequency. The overall antenna
height decreases by about 25%. The bandwidth of the antenna
increases by a factor of 2.5 times or more over that of a normal
design. In addition the antenna increases in efficiency by more
than 10% as compared to a normal distributed loaded monopole
design.

The top unit hub 64 is drilled with eight holes spaced every 45
degrees around the circumference of sufficient diameter and
depth to accept the conductive radial spokes 62. Eight holes are
also drilled in the top of the hub along the outer rim and are
aligned over the eight holes previously drilled and are threaded
to accept set screws that secure the radial conductive spokes
62. All the spokes 62 are of the same length and of sufficient
diameter and strength to be self-supporting extending
horizontally out from the hub as shown in FIG. 5. The complete
top unit with hub and spokes is slipped over the top section of
the distributed loaded monopole antenna and horizontally extends
in all directions as shown in FIG. 5. The antenna is tuned by
decreasing or extending the height of the top unit above the
load coil of the antenna. The top unit is provided to maximize
and make uniform the current profile of the antenna from the
base to as high along the antenna length as possible while
providing improved bandwidth and efficiency.

In other embodiments, the top unit 70 may include a
non-conductive hub 72 with eight non-conductive rods 74
extending from the center-insulated hub 72 as shown in FIG. 6.
These rods may be formed of an insulating material that may be
used for radio frequencies. The top section extends through the
hub 72 and is then connected to a large conductor or wire 76 at
a first end 78 of the wire. The other end 80 of the wire is not
electrically connected to any conductive material. This wire 76
is wound in a spiral form from the center in an increasing
diameter. This forms a large spiral conductor at the very top of
the antenna as well as provides capacitive loading. The function
of this configuration is to maximize and make uniform the
current profile from the base of the antenna extending all the
way to the top of the antenna.

When using the top unit 70 with a load coil and helix of the
antenna shown in FIG. 2, the inductance for the helix and the
load coil must be reduced by about 1/2(50%). This will allow the
antenna to resonate at the same frequency.

For the combined capacitive top unit and load coil of FIG. 5,
the load coil and helix inductance is also reduced by about 50%.
The overall antenna height decreases by about 25% for the
capacitive top unit antenna and for the combined load inductor
and top unit combination the antenna height remains the same or
in some cases may be slightly larger.

In further embodiments, the bandwidth of the antenna may be
enhanced by including an additional coiled wire 82 in a top unit
as also shown in FIG. 6. The additional wire 82 includes first
and second ends 84 and 86 that are each not electrically
connected to any conductive material. It has been found that
interlacing a false winding into a current enhancing unit (such
as the top unit winding shown in FIG. 6) or a radiation
resistance unit (such as a helix as shown in FIG. 7) enhances
the bandwidth of the top unit as well as improves the current
profile along the antenna. The interlaced false winding has
little effect on the resonant frequency of the antenna system.

Similarly, a false winding may be provided in a helix of an
antenna in accordance with an embodiment of the invention as
shown in FIG. 7 to enhance the bandwidth of the helix. In this
embodiment, a radiation resistance unit 90 includes a helix
winding 92 that is wound around a non-conductive tube and
electrically connected at each end to electrical couplings. An
additional winding 94 is interlaced within the helix winding but
is not connected electrically to any point within the helix or
at the ends of the winding 94. The winding 94 is merely
suspended within the helix winding 92 as shown in FIG. 7. This
false winding 94 has been found to enhance the bandwidth of an
antenna by as much as 100% (i.e., doubling it). The effect of
this false winding is to reduce the capacitance between helix
and load coil windings, which has been found to be a bandwidth
limiting mechanism in helix coils and load coils.

In further embodiments, the resonance of an antenna of the
invention that includes a helix may be changed by adding to or
removing from the helix, a turn of winding turns of the helix to
change coil inductance. This may be accomplished by employing a
coil adjustment unit such as units 100 or 110 as shown in FIGS.
8 and 11 respectively. The coil adjustment unit 100 shown in
FIG. 8 includes an electrically conductive slotted tubing 102
(shown in FIG. 9) that is received within the tubing of the
helix, i.e., the tubing around which the helix coil (not shown)
is wrapped. An electrically conductive tapered sleeve 104 is
then inserted within the tubing 102. The slotted tubing 102 may
be made from aluminum or any other non-ferrous conductive
material. The slot 106 in the tubing 102 is cut lengthwise as
shown and may be any convenient width but not greater than 1/6
of the tubing circumference. The top of this tubing should have
slots cut to allow a clamp to securely fasten telescoping tubing
to be inserted into tubing (102). The total length of this
tubing should be such that the portion slotted will fit into the
helix tubing and locked into the helix top fitting clamp
assembly using a clamp as discussed above.

A portion of the tubing 102 should also protrude from the helix
for the additional non-ferrous sleeve 104 to easily slide inside
and be secured using a clamp. This sleeve 104 is cut lengthwise
as shown to create a long angled section 108. This sleeve 104
when fitted into the slotted tubing 102 provides variations in
opening or closing the slot responsive to turning the sleeve 104
with respect to the tubing 102. This permits eddy currents to
circulate within this tubing combination where the slot has been
closed by the twisting action of tubing. The effect of the
slotted tubing when the slot is open is minimal on the helix
inductance. When the slot is filled or closed by the rotation of
the sleeve 104, eddy currents will be allowed to flow and
electrically short out turns of the helix therefore allowing
variations of the helix inductance. This same technique may be
used for solenoid coils of any length thereby allowing
adjustment of the inductance. The number of windings and/or the
length of a load coil may also be adjusted using such an
adjustment unit.

Similarly, the coil adjustment unit 110 shown in FIG. 11
includes an electrically conductive slotted tubing 112 having a
slot 114, and a conductive sleeve 116. In this case the sleeve
116 does not include a tapered edge, and the unit 110 is
adjusted by varying the distance to which the sleeve 116 is
inserted within the slotted tubing 112. In both cases, once the
adjustment has been made to satisfaction the adjusting tubing is
clamped securely.

In addition to these embodiments, the distributed loaded
monopole antenna may take on other forms. These include reducing
the height of the antenna and inductance of the helix and load
coil, and affixing at the top of the top section a horizontal
series of electrical conductors extending out from the center in
the form of spokes for a given distance. These conductors may be
any arbitrary number and are arranged as spokes from a hub as
discussed above. In accordance with further embodiments, a plain
sheet of metal or conductive screen may also be used. Other such
embodiments may also be employed where they provide for a large
capacitance from the top of the antenna to ground. This
capacitance provides for further uniform distribution of current
for an even greater distance along the antenna height or length.
This further allows for wider bandwidth operation and higher
efficiency.

Further embodiments provide that a helix may be constructed as
a lattice network of wider width than thickness as discussed
below with reference to FIGS. 14 17. This embodiment may take on
the form of a latticework constructed of insulating material
that is adequately braced along its height or length. The ends
of the latticework consist of fabricated aluminum pieces so
shaped to support the lattice structure at each end. Winding
suitable conductors as described above around the structure from
the base to the top forms a helix. The winding is such that the
number of turns per unit length is higher at the bottom than at
the top. The top of this helix winding is electrically
terminated to the conductive lattice termination. These aluminum
pieces or suitable conductors provide for affixing additional
conductors in the form of tubing, rod or pipe. In this manner,
the antenna may be extended in length or height and provide for
electrical connection of the helix winding. This extends the
electrical connection from ground up through the helix to the
top of the antenna through the load coil. The aluminum or any
conductive material at the top of the helix structure allows for
terminating the helix winding and provides electrical connection
to the above mentioned upper structures of the antenna. These
upper structures include a mid-section as discussed above. A
load coil of any of a variety of geometric shapes may also be
employed as further discussed below. To allow connection and
proper matching between a radio frequency source and the antenna
this above-described helix provision is allowed for tapping the
helix conductor anywhere along its length from the bottom of the
antenna. The rectangular helix geometry and various load coil
geometry allow further reduction of required loading in the form
of inductance and enhance further the distributed loading affect
of capacity along the length of the antenna to ground. This
allows even further improved bandwidth and radiation efficiency.
This embodiment may also be used with variations in load coil
inductance and helix length and helix inductance, together with
a series capacitor match between helix tap and the source of
radio frequency energy. These variations allow equivalent
performance to a conventional antenna as much as 9 times larger
in size.

Current profiles have been developed for various such
embodiments of 1/2 wave and 5/8 wave distributed loaded monopole
antennas. The manipulation of helix length and inductance as
well as the ratio of load coil to helix inductance may achieve a
wide variety of suitable antennas.

In addition to the above embodiments, providing a remotely
controlled top section length may yield a distributed loaded
monopole antenna that is continuously tunable over a large
frequency range. This may be achieved utilizing a motor driven
worm gear or any other method of varying remotely the adjustment
of the top section length. Similarly the antenna may be tuned by
varying the helix inductance. This may be accomplished by
varying the electrical length of the helix but without changing
the mid-section length between the helix top and load coil.

In particular, an antenna in accordance with further
embodiments may include a radiation resistance unit 120 having a
non-electrically conductive structure 122 around which is
wrapped a conductive material 124 in the form of a helix as
shown in FIG. 14. The structure 122 may be provided by four
elongated edge elements 126 that are each connected to internal
non-conductive bridges 128. The end portions 130, 132 are
conductive and are electrically connected to each of the ends
134, 136 respectively of the conductive material 124. Each of
the bridge portions 128 includes a central hole through which a
non-conductive tube may pass, and the conductive end portions
130, 132 also include such an opening as well as a clamp for
attaching the unit 120 to the conductive mid-section of an
antenna at the upper end of the unit 120 and to ground at the
lower end of the unit 120. The mid-section may further include a
reinforcing fiberglass rod.

The conductive material 124 may be any suitable conductor such
as copper strips (that are thin in depth and wide in width) or
copper braid, wire or similar material. The bottom of the
winding is fastened and electrically connected to the aluminum
or similar conductive bottom plate. The end of the helix winding
material is fastened using suitable wire connecting lug or
conductive strip and soldered to provide a low loss electrical
connection. The lug or connecting strip is fastened with a
machine screw to a hole drilled into bottom plate which has been
threaded to accept a machine screw. This provides a secured
electrical connection. A similar fastener may be used to connect
the top end of the helix winding to the helix top plate.

The antenna shown in FIG. 16 may provide near 1/2 wave vertical
antenna performance. The mid-section may be lengthened or
shortened as discussed above to tune the resonance of the
antenna. Similarly, the antenna shown in FIG. 17 may provide
improved performance with additional bandwidth, The current
enhancing unit 140 of FIG. 17 may be formed using a conductive
planosprial coil 142 that is sandwiched between two
non-conductive discs 144 and mounted to a non-conductive tube
section 146 as shown in FIGS. 15A, 15B and 15C. The ends of the
coil 142 are passed through two openings 148 and 150 in the
inner disc and connected to the conductive mid-section and
top-section of the antenna. Adjustment of the length of the
top-section (as discussed above) may further be used to tune the
antenna to resonance. In either antenna, various ratios of load
coil to helix inductance may permit various performance levels
of the antenna to be optimized.

When a flat antenna is designed for resonance much lower than
normal, it will give 5/8 wave performance. The embodiment shown
in FIG. 14 uses the flat helix but this helix is a little longer
by about 10%. This allows a slightly higher inductance in the
helix.

The embodiment shown may be ground mounted as discussed above
using a base mounting rod. Attached to this base mounting rod
may be an enclosure housing a capacitor (e.g., 22 as shown in
FIG. 1) and a standard coax receptacle. The center conductor of
this coax receptacle is connected to one side of the series
capacitor using a short wire. The coax shield is connected
electrically through the enclosure box mounting plate and clamps
to the base of the antenna, mounting post and the radial/ground
system. The other side of the capacitor is connected to a feed
through also using a short wire from the capacitor, and this
short wire exits outside the box for connection of an additional
wire that is used to tap the helix base a few turns from the
bottom. Also connected to the base mounting rod is a grounding
wire that is connected to a ground rod. The base mounting rod is
a conductive material and is driven into the ground. This rod is
securely connected to the helix base plate which is also
conductive. This allows grounding the base of the helix and the
beginning of helix winding to the ground using the ground wire
and the ground rod.

Radials are run on top of or in the ground by burying them
under the surface. The radials are extended out from the base in
a circular manner like the spokes extending from the hub of a
wheel (similar to the hub and spoke structure of the top unit
shown in FIG. 4). The radials are electrically connected to the
base of the antenna through the ground rod and wire. This allows
including the radials as part of the antenna ground system and
serves as an electrical counterpoise.

The antenna shown in FIG. 17 may be made for 1/4 wave
performance using suitable values of helix and load coil,
together with proper dimensions of the top and bottom sections.
This provides extended bandwidth performance and improved
efficiency. The antenna may utilize either load coil (32 or
140), and the helix length is reduced slightly to permit the
antenna to resonate just below the lower frequency of operation.
In this antenna, there is no need for the capacitor coupling (22
of FIG. 1) to tune out the added inductance.

In further embodiments, antennas of the invention may be
combined to form other antenna systems such as dipoles where two
antennas are placed back to back and their helixes electrically
connected at a mutual base. The method of connecting the radio
frequency source is to tap the helix from the middle and extend
to each side till a suitable match between source and load can
be achieved. A balanced matching transformer or BALUN can be
used to drive the feed point. In addition, the antenna may be
arranged in vertical positions along the ground and formed into
arrays of antenna elements providing directional transmission.
Distributed loaded monopole elements combined into dipoles may
be further combined to form horizontally or vertically polarized
arrays such as yagis or phase driven arrays of any number of
elements. Such elements may also be combined into loops
providing directional characteristic with improved sensitivity
compared to other loop forms.

For example, as shown in FIG. 18 multiple antennas 150, 152,
154 of different resonant frequencies resulting in different
physical sizes may be used together to provide a multi-frequency
system on a common, electrically conductive, mounting stage 156.
An equivalent electrical schematic diagram of three such
antennas sharing the common mounting stage is shown in FIG. 19.
This mounting stage (which may be elevated from ground) may be
any conductive surface such as a vehicle or a ship or a large
metal sheet such as a roof of a building. When mounting in an
elevated manner using a long pole such that the antennas and the
mounting surface are some height above ground, the ground
radials may be used to as a counterpoise as well to stabilize
the structure. It is not required that any counterpoise or
radial system be resonant

As shown in FIG. 19, a single coaxial feed line 160 is used
from the source of radio frequency excitation. All three
antennas are connected to the coaxial feed in a parallel manner.
The proper selection of antenna is provided by the series tuned
circuits connecting to the proper tap point on each helix 162,
164, 166. At the frequency of operation and resonance of the
particular antennas selected the series resonant coupling
circuits will be of sufficiently low impedance to couple the
coaxial feed to the proper antenna. The series coupling elements
not in use will be sufficiently de-coupled by virtue of their
relatively high impedance. This configuration by virtue of this
operation will provide efficient operation for each antenna to
be automatically selected.

Antennas used in accordance with further embodiments of the
invention may provide a pair of distributed loaded monopole
antennas as a half wave loop or two pairs may be used form a
full wave loop. FIG. 20 shows two such antennas used as a half
wave loop. A first antenna 170 includes a helix 172 and a load
coil 174, and a second antenna 180 includes a helix 182 and a
load coil 184. A variable capacitor may be coupled between the
upper ends 176 and 186 of the antennas 170 and 180. The taps
near the lower ends 178 and 188 of the antennas 170 and 180 may
be coupled to a first balanced transformer winding while a
second transformer winding is coupled to a coaxial connector
port 190. In other embodiments, the end 192 of the one antenna
170 may be coupled to the first conductor of the coaxial
connector 190, while the second conductor of the coaxial
connector is coupled to a tap near the lower end 188 of the
antenna 180.

During operation, the loop may be resonant at a higher
operating frequency, and the loop may be tuned to resonance
using the variable capacitor between the ends 176 and 186 of the
antennas 170 and 180. If the loop is used for transmitting, the
variable capacitor must be of sufficiently high voltage rating
so as not to be broken down by the very large high radio
frequency voltages generated across this capacitor. To implement
the configuration or embodiment as shown, the midsections of
each monopole element are bent into a 90-degree right angle. The
bottoms of the helixes are joined using a conductive coupling.
The entire loop is mounted on an insulated pole and may be
rotated. The loop is feed with an unbalanced coax feed line and
the transformer may be used to balance the loop. A virtual
ground exists where the helix bases are joined. Because of this
virtual ground the loop may be fed unbalanced while the coax
shield is grounded at the helix joining point. To match the loop
to the source in either case, it is only necessary to select the
proper tap of the helix.

Antennas in accordance with various embodiments of the
invention may also be coupled as a distributed loaded dipole as
shown at 200 in FIG. 21. The dipole antenna 200 includes two
load coils 202 and 204 that are each mutually spaced from an
intermediate (double length) helix 206, which is formed by
joining two helixes together at their ends. Taps taken from
either side near the center of the helix are coupled to either
side of a first winding of a balanced transformer 208. The
second winding of the transformer is coupled to each of the two
conductors of a coaxial connector 210 as shown. The transformer
may be mounted in an enclosure. Selection of the proper tap
points from the middle to each side of the helix winding should
provide a sufficient impedance match to the radio frequency
source. The transformer enclosure may be mounted a short
distance from the dipole antenna and connected with short wires
as indicated.

Antennas in accordance with further embodiments of the
invention may include a current enhancing unit 210 and a
radiation resistance unit 212 wherein the radiation resistance
unit 212 is not formed as a helix or even a spiral that rotates
about the longitudinal axis of the antenna, but rather as a
planospiral that rotates about an axis that is orthogonal to the
longitudinal axis of the antenna as shown in FIG. 22. The coil
of the unit 212, therefore, is formed as a coil that extends
back and forth along a length of the unit 212. The antenna may
be driven by a transmission signal (as indicated at 214) by
tapping onto a portion of the coil of the unit 212 near but not
at the ground end of the coil in unit 212.

For example, as shown in FIG. 23, the current enhancing unit
may comprise a load coil 32 as discussed above with reference to
FIG. 2. The radiation resistance unit 220, however, includes a
coil 222 that extends from one end 224 (at ground) to a second
end 226 by wrapping up and down the length of the unit 220 as
shown in FIG. 23. The antenna includes four main parts similar
to the antenna shown in FIG. 2. The current enhancing unit shown
in FIG. 23 includes a central support element 228, the coil of
wire 222, and coil wire stringers 230 and 232 at the top and
bottom of the center support element.

Inserted into the center support element (which consists of a
1-inch square fiberglass pole) is an aluminum mounting rod 234
and a mid-section attachment rod 236. The coil wires 222 are
strung vertically along the support element 228 to form an
elongated spiral loop. This loop is fastened to the mid-section
236 using solder lugs and bolted to the mid-section attachment
rod. The mid-section is attached by slipping this mid section
tubing over the attachment rod and clamping them together using
clamps. The lower part of the loop is attached to the aluminum
mounting post 234 using wire lugs that arc screwed into the
mounting post through the fiberglass main support holding the
wire coil 222. The ground wire is clamped to the ground rod
using a ground damp. In further embodiments, a false winding may
also be added to the unit 220 as discussed above with reference
to FIGS. 6 and 7.

The performance of this antenna as shown in FIG. 2 at 7 MHz has
been measured and it compared well with a 1/4 wave antenna. This
full size antenna is 33 feet in height and this antenna with a
plano spiral radiation resistance unit is 1/3 this size or
approximately 11 feet in height. Both antennas were mounted on
the same ground system and fed with the same power as measured
at the base of each antenna. A driving power of 1 watt was used.
Measured levels of radiating signal strength were so close to a
1/4 wave measured signal strength that the two antennas appear
to be equal in radiating performance.

The current profile was measured using an indirect current
sensor, and it compared well with a current profile for the
antenna of FIG. 2 employing a three dimensional helix. The
antenna of FIG. 23 appeared to provide uniform current
distribution.

One feature of the design of an antenna such as that shown in
FIG. 2, is that normally an antenna of such a size as discussed
above requires 25 .mu.H of combined helix and load coil
inductance to resonate at 7 MHz. This also requires considerable
lengths of wire (about 42 feet for the helix and 20 feet or so
for the load coil). The planospiral design uses 10% less wire
and is resonant at 7 MHz using 10% less inductance. The
planospiral helix appears to make better use of distributed
capacity loading to ground than does the standard DLM. This has
also been noticed in the three dimensional flat board-like frame
helix used with planospiral load coils. Due to better
utilization of distributed loading techniques by the piano
spiral antenna, it may achieve better efficiency and wider
bandwidth especially when utilizing the false helix winding. The
system of FIG. 23 also appears to provide excellent linearity of
the amplitude and phase and the relative linear progression of
reactive to non reactive changeover in the antenna through the
bandwidth.

Certain of the above distributed loaded monopole antennas
utilizes a helix with a load coil to improve the radiated
efficiency of the helix and antenna overall. The addition of the
load coil raises the radiation resistance of the antenna,
increases and makes uniform the current distribution along the
antenna, and increases the useful bandwidth of the antenna.
These structures, though practical and useful for many ranges of
frequency applications (such as very low, low, medium, high and
very high frequency systems), present practical limitations for
ultra high frequency and microwave radio frequency applications.
For example, a 1000 MHz system might require a helix that is
eight thousandths of an inch in diameter and 0.3 inches in
length of which upwards of 100 turns of very fine wire must be
wound.

Applicant has further discovered that a plano-spiral antenna
may be created in accordance with a further embodiment of the
invention that provides coils fabricated in two planes. In
further embodiments, such an antenna may be scaled to provide
operation at ultra high frequencies and microwave radio
frequencies by providing a similarly planar load coil 240 and
radiation resistance unit coil 242 on a printed circuit board as
shown in FIG. 24. The coil 242 may also include a plurality of
tap points 244 for easy matching to a standard feed line. The
circuit provides a continuous conductive path through the pass
through holes shown at 246 and 248 as is well known in the art.
In further embodiments, fewer windings on the load coil 250 and
radiation resistance coil 252 with taps 254 may be used as shown
in FIG. 25, and the load coil 260 and radiation resistance coil
262 with taps 264 may be formed in many difference shapes such
as circular spirals as shown in FIG. 26.

Such antennas may be suitable for applications such as radio
frequency identification tags (RFID) at high frequencies. It is
expected that these may be implemented on a silicon substrate of
a very small scale, providing for example a 1/4 wave antenna up
to or above 4.2 GHz.

For example, the helix inductance for an antenna at 100 200 MHz
may be 0.131 .mu.H or 131 nH, and the load coil inductance may
be 0.211 or 211 nH. The helix to load coil ratio for inductance
is 1.61. To be a true 1/4 wave distributed loaded monopole
antenna the load coil to helix inductance ratio should be 1.4
1.7.

Another such antenna that is 1/2 the physical size was also
measured, and the helix inductance for the antenna may be 0.088
.mu.H or 88 nH, and the load coil inductance may be 0.135 or 135
nH. The helix to load coil ratio for inductance is 1.56. This
resulted in an antenna with a resonance around about 400 500 mH.

Those skilled in the art will appreciate that numerous
modifications and variations may be made to the above disclosed
embodiments without departing from the spirit and scope of the
invention.

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