[![](0logo.gif)](http://rexresearch.com/index.htm) [rexresearch.com](http://rexresearch.com/index.htm) --- Manos TENTZERIS Ambient Energy Antenna --- Combine this with the [TATE AMBIENT POWER MODULE](http://rexresearch.com/tate/tate.htm) ( w/ Zener diodes ? ) 7 July 2011 Power from the Air: Device Captures Ambient Electromagnetic Energy to Drive Small Electronic Devices Researchers have discovered a way to capture and harness energy transmitted by such sources as radio and television transmitters, cell phone networks and satellite communications systems. By scavenging this ambient energy from the air around us, the technique could provide a new way to power networks of wireless sensors, microprocessors and communications chips. "There is a large amount of electromagnetic energy all around us, but nobody has been able to tap into it," said Manos Tentzeris, a professor in the Georgia Tech School of Electrical and Computer Engineering who is leading the research. "We are using an ultra-wideband antenna that lets us exploit a variety of signals in different frequency ranges, giving us greatly increased power-gathering capability." Tentzeris and his team are using inkjet printers to combine sensors, antennas and energy scavenging capabilities on paper or flexible polymers. The resulting self powered wireless sensors could be used for chemical, biological, heat and stress sensing for defense and industry; radio frequency identification (RFID) tagging for manufacturing and shipping, and monitoring tasks in many fields including communications and power usage. A presentation on this energy scavenging technology was given July 6 at the IEEE Antennas and Propagation Symposium in Spokane, Wash. The discovery is based on research supported by multiple sponsors, including the National Science Foundation, the Federal Highway Administration and Japan's New Energy and Industrial Technology Development Organization (NEDO). Communications devices transmit energy in many different frequency ranges, or bands. The team's scavenging devices can capture this energy, convert it from AC to DC, and then store it in capacitors and batteries. The scavenging technology can take advantage presently of frequencies from FM radio to radar, a range spanning 100 megahertz (MHz) to 15 gigahertz (GHz) or higher. Scavenging experiments utilizing TV bands have already yielded power amounting to hundreds of microwatts, and multi-band systems are expected to generate one milliwatt or more. That amount of power is enough to operate many small electronic devices, including a variety of sensors and microprocessors. And by combining energy scavenging technology with supercapacitors and cycled operation, the Georgia Tech team expects to power devices requiring above 50 milliwatts. In this approach, energy builds up in a battery-like supercapacitor and is utilized when the required power level is reached. The researchers have already successfully operated a temperature sensor using electromagnetic energy captured from a television station that was half a kilometer distant. They are preparing another demonstration in which a microprocessor-based microcontroller would be activated simply by holding it in the air. Exploiting a range of electromagnetic bands increases the dependability of energy scavenging devices, explained Tentzeris, who is also a faculty researcher in the Georgia Electronic Design Center at Georgia Tech. If one frequency range fades temporarily due to usage variations, the system can still exploit other frequencies. The scavenging device could be used by itself or in tandem with other generating technologies. For example, scavenged energy could assist a solar element to charge a battery during the day. At night, when solar cells don't provide power, scavenged energy would continue to increase the battery charge or would prevent discharging. Utilizing ambient electromagnetic energy could also provide a form of system backup. If a battery or a solar-collector/battery package failed completely, scavenged energy could allow the system to transmit a wireless distress signal while also potentially maintaining critical functionalities. The researchers are utilizing inkjet technology to print these energy scavenging devices on paper or flexible paper-like polymers -- a technique they already using to produce sensors and antennas. The result would be paper-based wireless sensors that are self powered, low cost and able to function independently almost anywhere. To print electrical components and circuits, the Georgia Tech researchers use a standard materials inkjet printer. However, they add what Tentzeris calls "a unique in house recipe" containing silver nanoparticles and/or other nanoparticles in an emulsion. This approach enables the team to print not only RF components and circuits, but also novel sensing devices based on such nanomaterials as carbon nanotubes. When Tentzeris and his research group began inkjet printing of antennas in 2006, the paper-based circuits only functioned at frequencies of 100 or 200 MHz, recalled Rushi Vyas, a graduate student who is working with Tentzeris and graduate student Vasileios Lakafosis on several projects. "We can now print circuits that are capable of functioning at up to 15 GHz -- 60 GHz if we print on a polymer," Vyas said. "So we have seen a frequency operation improvement of two orders of magnitude." The researchers believe that self-powered, wireless paper-based sensors will soon be widely available at very low cost. The resulting proliferation of autonomous, inexpensive sensors could be used for applications that include: Airport security: Airports have both multiple security concerns and vast amounts of available ambient energy from radar and communications sources. These dual factors make them a natural environment for large numbers of wireless sensors capable of detecting potential threats such as explosives or smuggled nuclear material. Energy savings: Self-powered wireless sensing devices placed throughout a home could provide continuous monitoring of temperature and humidity conditions, leading to highly significant savings on heating and air conditioning costs. And unlike many of today's sensing devices, environmentally friendly paper-based sensors would degrade quickly in landfills. Structural integrity: Paper or polymer-based sensors could be placed throughout various types of structures to monitor stress. Self powered sensors on buildings, bridges or aircraft could quietly watch for problems, perhaps for many years, and then transmit a signal when they detected an unusual condition. Food and perishable material storage and quality monitoring: Inexpensive sensors on foods could scan for chemicals that indicate spoilage and send out an early warning if they encountered problems. Wearable bio-monitoring devices: This emerging wireless technology could become widely used for autonomous observation of patient medical issues. --- USP 6917339 Multi-band broadband planar antennas Inventor(s): LI RONGLIN [US]; TENTZERIS EMMANOUIL M [US]; LASKAR JOY [US] + (LI RONGLIN, ; TENTZERIS EMMANOUIL M, ; LASKAR JOY) Classification: - international: H01Q1/24; H01Q11/12; H01Q21/30; H01Q5/00; H01Q7/00; H01Q9/30; H01Q9/42; (IPC1-7): H01Q11/12; H01Q7/00 - European: H01Q21/30; H01Q5/00B; H01Q9/30; H01Q9/42 Antennas of broadband and multi-band operation are presented. A broadband planar antenna includes two inverted-L antennas (ILAs) facing each other across a gap. One of the ILAs is input fed, and the other is electromagnetically coupled. The positioning of the gap affects the bandwidth. A dual-band planar antenna includes two ILAs facing each other across a gap with one of the ILAs being input fed, and the other being coupled. This dual-band planar antenna also includes a monopole antenna disposed between the two ILAs. A triple-band planar antenna includes two ILAs facing each other across a gap with one of the ILAs being input fed and the other IPA being coupled. This triple-band antenna also includes a monopole antenna disposed between the two ILAs, and a conductor extending horizontally from the monopole antenna towards, but not reaching the coupled ILA.; Another dual-band antenna includes an inner cut loop antenna encompassed by an outer cut loop antenna. Each of the cut loop antennas includes two ILAs with one of the ILAs being input fed and the other being coupled. Description RELATED APPLICATION [0001] This application claims priority to and the benefit of the prior filed co-pending and commonly owned provisional patent application, which has been assigned U.S. Patent Application Ser. No. 60/413,327, entitled "Multi-band broadband planar wire antennas for wireless communication handheld terminals," filed on Sep. 25, 2002, and incorporated herein by this reference. FIELD OF THE INVENTIONS [0002] The inventions relate generally to antennas, and more particularly to planar antennas with multi-band and broadband functionalities such as may be used with mobile communication devices and in other compact antenna applications. BACKGROUND OF THE INVENTIONS [0003] In recent years, there has been a tremendous increase in the use of wireless communication devices. The increased use has filled or nearly filled existing frequency bands. As a result, new wireless frequency band standards are emerging throughout the world. For example, the existing 1 (1G) and 2 (2G) generation cellular mobile communication systems operate at: the AMPS (824-894 MHz) and PCS (1850-1990 MHz) bands in North America; the GSM (880-960 MHz) and DCS (1710-1880 MHz) bands in Europe; and the PDC (810-915 MHz) and PHS (1895-1918 MHz) bands in Japan. For future wireless communication systems, such as the emerging 3rd generation (3G) systems or beyond, new spectrum may be allocated around 2 GHz (e.g., already identified 1920-2170 MHz band for UMTS or IMT2000). [0008] Like cellular mobile communications systems, Wireless Local Area Networks (WLANs) also use various frequency bands. IEEE 802.11b, Bluetooth, and HomeRF operate in the 2.4 GHz ISM band (2.400-2.485 GHz). IEEE802.11a and HiperLAN (in Europe) will use the 5 GHz ISM band (5.15-5.35 GHz and 5.725-5.825 GHz for IEEE802.11a, 5.15-5.25 GHz for HiperLAN1 and 5.15-5.35 GHz for HiperLAN2). Japan has started the development of standards for WLAN devices in the 5 GHz band. [0009] As the frequency standards throughout the world change and evolve, wireless devices that can operate at the old and the new frequency standards are needed. [0010] Increased functionality is another factor that drives the need for wireless devices that can operate at multiple frequencies. New wireless devices may provide multiple functions, but one or more of the functionalities may only be available at a respective one or more different frequencies from the base operating frequency. Thus, there is a need for wireless devices that can operate and implement functionalities at more than one frequency. [0011] Yet another factor that drives the need for wireless devices that can operate at multiple frequencies is the desire of users for multi-functional services that operate at high data speeds including voice, video, and data transmissions. A wireless device may provide such services with automatic access and seamless roaming if the device can operate across multiple frequency bands. [0012] The antenna is a key component in the realization of such a multi-mode wireless device. It is desirable for an antenna used in a multi-mode wireless device to include broadband performance for use in successive bands. It is also desirable for such an antenna to have multi-band performance for separated bands including far-separated bands. In addition to broadband and multi-band performance, it is desirable for such an antenna to be of a small size, a simple structure, and be of lightweight materials so as to be easily mounted in a handheld terminal with relatively low cost. Further, the radiation patterns in all service bands of such an antenna should be omni-directional and polarization-mixed to adapt to land-mobile propagation environments. [0013] In recent years, a great number of new antenna structures have been developed for dual-band or triple-band operations in wireless communication handsets. A simple way to realize dual-band operation is to directly feed two antenna elements, each of which has a separate resonant frequency. For example, a combination of a monopole and a helical antenna, where the monopole is placed through the middle of the helix in the axial position and is simply connected to the end of the helix, has been successfully applied in GSM/DCS bands. Directly feeding two monopoles with different lengths can also result in two resonant frequencies. Another dual-band operation includes electromagnetically coupling two separate radiating elements. A coupling dual-band dipole antenna has been developed for WLAN applications in the 2.4 and 5.2 GHz bands. By coupling a rectangular element at the high frequency and an L-shaped element at the lower frequency, a dual-band operation was achieved for a planar inverted-F antenna (PIFA). The triple-band operation of the PIFA was implemented by adding one more L-shaped radiator. [0014] Usually, a dual-band or triple-band antenna has a narrow bandwidth at each band. In order to achieve a broadband multi-band operation, some specific techniques or additional structures have to be incorporated. For instance, a broadband dual-band operation could be realized by properly notching a rectangular patch. The bandwidth of the higher band for a dual-band PIFA was increased by adding one more resonator. By introducing a stacked element, by making the longer and shorter dipoles resonate, respectively, at slightly below and slightly above the center frequency, or by adding some parasitic structures, the bandwidth at one of the two bands of a dual-band antenna may be increased. Yet, broadband performance is desired at every band of a multi-band antenna. [0015] Accordingly, there is a need for multi-band broadband antennas. In particular, there is a need for multi-band broadband antennas that are of small size, simple structure, and lightweight materials so as to be easily mounted in a handheld terminal with relatively low cost. SUMMARY OF THE INVENTIONS [0016] The inventions satisfy the need for multi-band broadband antennas such as may be used in wireless communication devices. Examples are presented of a broadband planar antenna, of two dual-band antennas, and or a triple-band antenna pursuant to the inventions. The antennas of the inventions have the advantages of being of simple structures such that they may be implemented in a small size, of lightweight materials, and at a relatively low cost. [0017] The inventions include an antenna made up of two inverted-L antennas (ILAs) facing each other across a gap. This antenna may be referred to as a loop antenna with a gap. One of the ILAs is fed by an input, and may be directly fed by a coaxial cable input. The other ILA is electromagnetically coupled with respect to the fed ILA. The coupled ILA faces the fed ILA, but is separated from the fed ILA by a gap. The length of the coupled ILA is longer than the fed ILA. In particular, the fed ILA, the coupled ILA, and the gap may be positioned with respect to each other to form three sides of a square, and may include a ground plane forming the fourth side of the square. Even more particularly, each of the ILAs may include a vertical leg of the same length that are parallel with respect to each other. Each of the ILAs also may include a horizontal leg, but the horizontal leg of the fed ILA may be shorter than the coupled ILA. In other words, the horizontal leg of the coupled ILA may be longer than the horizontal leg of the fed ILA. [0018] The inventions also include a dual-band antenna. An exemplary dual-band antenna may include an inverted-L antenna (ILA) referred to as the "first" ILA and another ILA referred to as the "second" ILA. In this example, the second ILA is electromagnetically coupled with respect to the first ILA, faces the first ILA, and is separated from the first ILA by a gap. The second ILA may be longer than the first ILA. In addition to the two ILAs, the exemplary dual-band antenna includes a monopole antenna disposed between the first ILA and the second ILA, and operative to receive input. Further, a connection exists between the monopole antenna and the first ILA to feed input to the first ILA. The connection may connect to the monopole antenna near its base and to the first ILA at its base. Each of the ILAs has a horizontal leg with the horizontal leg of the first ILA being shorter than the horizontal leg of the second ILA. The monopole antenna may be shorter than the vertical leg of the second ILA. [0019] In addition, the inventions include a triple-band antenna. An exemplary triple-band antenna may include an inverted-L antenna (ILA) referred to as the "first" ILA and another ILA referred to as the "second" ILA. In this example, the second ILA is electromagnetically coupled with respect to the first ILA, faces the first ILA, and is separated from the first ILA by a gap. The second ILA may be longer than the first ILA. In addition to the two ILAs, the exemplary triple-band antenna includes a monopole antenna disposed between the first ILA and the second ILA, and operative to receive input through a feed probe. Further, a connection exists between the monopole antenna and the first ILA to feed input to the first ILA. The connection may connect to the monopole antenna near its base and to the first ILA at its base. A conductor is connected to the monopole antenna opposite to the connection. The conductor extends horizontally from the monopole antenna towards, but not reaching, the second ILA. The conductor and the feed probe combine to form a third ILA in this antenna. [0020] Further, the inventions include another dual-band antenna. An exemplary dual-band antenna may include an inner cut loop antenna encompassed by an outer cut loop antenna. The inner cut loop antenna may include a "first" inverted-L antenna (ILA) facing a "second" ILA across a "first" gap. The first ILA is fed input while the second ILA is electromagnetically coupled at least to the first ILA. The outer cut loop antenna includes a "third" ILA facing a "fourth" ILA across a "second" gap. The third ILA is fed input via a feed probe and a connection connected to the first ILA of the inner cut loop antenna while the fourth ILA is electromagnetically coupled at least to the third ILA. a BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an exemplary loop antenna with a gap for bandwidth enhancement according to the inventions. FIG. 2 is a graph of the Voltage Standing Wave Ratio (VSWR) for the exemplary antenna of FIG. 1. FIG. 3 illustrates an exemplary planar dual-band loop-monopole antenna according to the inventions. FIG. 4 is a graph of the VSWR for the exemplary antenna of FIG. 3. FIG. 5 illustrates an exemplary planar triple-band loop-monopole antenna according to the inventions FIG. 6 is a graph of the VSWR for the exemplary antenna of FIG. 5. FIG. 7 illustrates an exemplary planar dual-band loop-loop antenna according to the inventions. FIG. 8 is a graph of the VSWR for the exemplary antenna of FIG. 7. DETAILED DESCRIPTION [0028] The inventions include multi-band broadband planar antennas such as may be used with mobile communication devices and in other compact antenna applications. Advantageously, the inventions provide multi-band broadband antennas that may be of small size, simple structure, and lightweight materials so as to be easily mounted in a handheld terminal with relatively low cost. FIGS. 1-2-Loop Antenna with a Gap [0030] FIG. 1 illustrates an exemplary broadband planar antenna 10 according to the inventions. In particular, the exemplary broadband planar antenna 10 may be considered a square wire loop antenna on a ground plane 11 with a gap 12, and may be referred to as a loop antenna with a gap. As explained below, the position of the gap 12 in the loop affects the bandwidth of the antenna 10. [0031] The antenna 10 illustrated in FIG. 1 may also be considered to be comprised of two Inverted-L Antennas (ILAs) 14, 16. In the exemplary embodiment, ILA 14 has a vertical leg 15 of height H connected at its top at a right angle to the right to a horizontal leg 18 of length L1. ILA 14 is directly fed by an input 17 such as a coaxial cable input. [0032] The other ILA, ILA 16, may be said to face the directly fed ILA 14. ILA 16 has a vertical leg 22 of height H parallel to the vertical leg 15 of ILA 14. ILA 16, like ILA 14, has a horizontal leg 22 connected to the top of its vertical leg 20 at a right angle. But the horizontal leg 22 of ILA 16 is connected at a right angle to the left of its vertical leg 20, and the horizontal leg 22 of ILA 16 is of length L2. In effect, the horizontal leg 18 of ILA 14 faces the horizontal leg 22 of ILA 16 across the gap 12 of the antenna 10. ILA 16 further differs from ILA 14 in that ILA 16 is excited by electromagnetic coupling with respect to the directly fed ILA 14. [0033] Advantageously, the broadband design of antenna 10 is achieved by making the length of the coupled ILA 16 longer than the directly fed ILA 14. Given that the heights of the vertical legs 15, 20 of the respective ILAs 14, 16 are the same (as noted, the antenna 10 may be considered a square loop antenna with a gap), the longer length of the coupled ILA 16 is achieved by making its horizontal leg 22 longer than the horizontal leg 18 of the directly fed ILA 14. In other words, L2 is greater than L1 as illustrated in FIG. 1. [0034] The relative lengths of the horizontal legs 18, 22 define the position of the gap 12 in the antenna 10. Thus, a change in the relative lengths causes an adjustment in the position of the gap 12 in the antenna 10. The shorter the horizontal leg 18 of the directly fed ILA 14, the closer the gap 12 in the antenna 10 is to the vertical leg 15 of ILA 14. Conversely, the longer the horizontal leg 18 of the directly fed ILA 14, the closer the gap 12 is to the vertical leg 20 of the coupled ILA 16. The position of the gap 12 affects the bandwidth of the antenna 10. [0035] FIG. 2 is a graph 24 of frequency (GHz) vs. simulated Voltage Standing Wave Ratio (VSWR) for the exemplary antenna 10 of FIG. 1 with different gap positions. The simulation was carried out using the MoM (Method of Moment) based Numerical Electromagnetics Code (NEC V1.1) and under the assumption of an infinite ground plane 11. Graph 24 includes a table 26 with three entries relating to the respective lengths of the horizontal legs 18, 22 of the ILAs 14, 16 used in the simulation. Each entry includes a measured length of the horizontal leg 18 of the directly fed ILA 14 and a measured length of the horizontal leg 22 of the coupled ILA 16. Each entry relates to the simulation and is plotted on the graph 24. Note, in this example, the gap 12=2 mm. [0036] FIG. 2 illustrates that as the difference between the length L2 of the horizontal leg 22 of the coupled ILA 16 and the length L1 of the horizontal leg 18 of the directly fed ILA 14 (e.g., L2-L1) decreases, the respective resonant frequencies for the ILAs 14, 16 (FHI for ILA 14 and FLO for ILA 16) move closer to each other. The maximum bandwidth for a certain criterion of VSWR is obtained when all the VSWR within this frequency band is below the VSWR threshold. For this example, the bandwidth for a VSWR criterion=2 is calculated to be 35%. Therefore, the optimum VSWR of 2 or less is achieved for a very wide bandwidth. FIGS. 3-4-Dual-Band Antenna [0038] FIG. 3 illustrates an exemplary dual-band broadband planar antenna 30 according to the inventions. The antenna 30 of FIG. 3 is similar to the antenna 10 of FIG. 1 in that each may be considered a square wire loop antenna on a ground plane 11 with a gap 12. The antenna 30 of FIG. 3 differs and provides dual-band operation by the addition of a monopole antenna 32 in the middle of the antenna 30 plus some adjustments. A monopole antenna may also be referred to as a monopole herein. [0039] More particularly, like the antenna 10 of FIG. 1, the antenna 30 of FIG. 3 may be considered to be comprised of two Inverted-L antennas (ILAs) 34, 36 that face each other across a gap 12. One of the ILAs 34 is fed input (as explained below), and the other ILA 36 is electromagnetically coupled to the fed ILA 34 and/or coupled with respect to the other parts of the antenna 30. Each of the ILAs 34, 36 includes a vertical leg, respectively 35, 40. [0040] The antenna 30, however, differs from the antenna 10 because the antenna 30 has a vertical monopole 32 rising from the ground plane 11 and centered between vertical legs 25, 30 of the ILAs 34, 36 of the antenna 30. The monopole 32 has a length less than the length (or height) of the vertical legs 25, 30 of the ILAs 34, 36. The monopole 32 is fed from an input 33, such as by a coaxial cable input, which also feeds ILA 34 through a connection 37 from the monopole 32 to the vertical leg 35 of the ILA 34. For example, as illustrated in FIG. 3, the input 33 may be centered between the vertical legs 35, 40 of the ILAs 34, 35 to directly feed the monopole 32 and to feed the ILA 34 through the connection 37 between the monopole 32 and the vertical leg 35 of the ILA 34. [0041] In particular, the connection 37 is disposed between the monopole 32 and the leg 35 of the fed ILA 34 such that the connection 37 connects near the base or input end of the monopole 32, runs above and parallel to the ground plane 11, and connects to the end closest to the ground plane 11 of the vertical leg 35 of the fed ILA 34. Thus, the fed ILA 34 does not connect to the ground plane 11 in antenna 30. As illustrated in FIG. 3, the distance between the ground plane 11 and the connection 37 is h1, which may also be referred to as the height of the connection 37. The length of the vertical leg 35 of ILA 34 is H2. The length of the vertical leg 40 of the coupled ILA 36 is h1+H2. [0042] The introduction of the monopole 32 as part of the antenna 30 causes additional differences with respect to the antenna 10 of FIG. 1. For example, the fed ILA 34 of antenna 30 includes a horizontal leg 38 of length L3. The coupled ILA 36 of antenna 30 includes a horizontal leg 42 of length L4. The respective lengths of L3 and L4 may need adjustment (as compared to their analogous parts in antenna 10) due to the connection 37. The monopole 32 is designed for resonance at a higher frequency than the ILAs. The height (h1) of the connection 37 is optimized for an optimal VSWR. Note that the connection 37 (which may be a wire) has a negligible contribution to the radiation fields due to its proximity (h<rad-s<-1 >is obtained from [beta]L1=/4[pi]. A decrease in h2 is equivalent to an increase in the coupling capacitance between the upper and lower patches, thus eventually leading to a decrease in the resonant frequency. [0053] Equation 11 suggests an alternate embodiment for the FSP antenna 504 (FIG. 5A), wherein the resonant frequency can be reduced using a lumped capacitive load (e.g., a lumped capacitor between the radiating edge of the lower patch 505 and the ground plane 502 of the FSP antenna 504 of FIG. 5A, as described above). The simulated results for input impedance versus frequency are shown in FIG. 13, wherein the resistance is shown with a sold line and the reactance is shown with a dashed line. As expected, the resonant frequency decreases with an increase in the loaded capacitance. Comparing FIGS. 12 and 13, it is noted that the proportional relationship of the resonant frequencies among C=0.3, 0.6, and 1.2 picofarad (pf) is very similar to that (about 3:4:5) read from the graphical solutions of equation 11 when C=(Y01/[omega]0)/2, C=Y01/[omega]0, and C=2Y01/[omega]0. This demonstrates agreement between the numerical investigation and theoretical analysis described above. [0054] As one example implementation, a test FSP antenna was integrated in the package of a Bluetooth chip operating in the Bluetooth ISM band (2.4-2.483 GHz). The test FSP antenna was fabricated with a brass sheet with a thickness of 0.254 mm. The following FSP antenna dimensions were chosen: 15 mm\*15 mm ( [lambda]0/8\*[lambda]0/8). To achieve the bandwidth (near 4%) required by the Bluetooth specifications, the total thickness of the antenna was selected to be 6 mm. By adjusting the height (h1) of the lower patch to 2.85 mm, the resonant frequency can be tuned to approximately 2.44 GHz. The simulated and measured results for the return loss are plotted in FIG. 14. As shown, good performance agreement is obtained, and both of the simulated and measured 10-dB return-loss bandwidths cover the Bluetooth band. The radiation patterns simulated and measured in the xz- and yz-planes at 2.44 GHz were compared, as shown in FIGS. 15A-15B, and good agreement was again noted. There is a nearly omni-directional pattern for the co-polarized component, which is desirable for Bluetooth applications. [0055] It should be emphasized that the above-described embodiments of the present invention, particularly, any "preferred" embodiments, are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the invention. Many variations and modifications may be made to the above-described embodiments of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of this disclosure and the present invention and protected by the following claims. ---