EP2351149A1

EP2351149A1 - Wideband radiating elements

Info

Publication number: EP2351149A1
Application number: EP09820095A
Authority: EP
Inventors: Bevan Beresford Jones; Peter John Liversidge
Original assignee: Argus Technologies Australia Pty Ltd
Current assignee: Commscope Technologies LLC
Priority date: 2008-10-15
Filing date: 2009-10-12
Publication date: 2011-08-03
Also published as: WO2010042976A1; CN102224637A; EP2351149A4

Abstract

Wideband radiating elements (100, 200, 300, 400), methods of transmitting and receiving signals using a wideband radiating element (100, 200, 300, 400), standalone antennas, and array antennas are disclosed. The wideband radiating element (antenna) (100, 200, 300, 400) has wide bandwidth for a relatively constant beamwidth and comprises a section of waveguide (130, 230, 330, 430), a patch radiator (110, 210, 310, 410), and one or more tuned loops (128, 228, 328, 428). The waveguide section (130, 230, 330, 430) is a quarter of a guide wavelength long or thereabouts, short circuited at one end (132, 232, 332, 432), and open circuited at the other end (134). The patch radiator (110, 210, 310, 410) is disposed within the waveguide section (130, 230, 330, 430). The tuned loops (128, 228, 328, 428) are coupled to the patch radiator (110, 210, 310, 410) as a feed for the patch radiator (110, 210, 310, 410) in a plane normal to the patch radiator (110, 210, 310, 410). The width of the waveguide section (130, 230, 330, 430) may be between about 0.7 wavelengths and about 1.3 wavelengths and the patch (110, 210, 310, 410) may be located at a height of 0.125 wavelengths or thereabouts above the short-circuited end (132, 232, 332, 432) of the waveguide section (130, 230, 330, 430).

Description

WIDEBAND RADIATING ELEMENTS

RELATED APPLICATION

The present application claims the benefit of the earlier filing date of Australian Provisional Patent Application No. 2008905334, which is incorporated by reference herein in its entirety, filed on 15 October 2008 in the name of Argus Technologies (Australia) Pty Ltd.

TECHNICAL FIELD The present invention relates generally to antennas and in particular to patch antennas.

BACKGROUND

International (PCT) Patent Publication No. WO 2006/135956 published on 28 December 2006 (International Patent Application No. PCT/AU2006/000814 filed on 15 June 2006 filed in the name of Argus Technologies (Australia) Pty Ltd et al) discloses dual-polarized patch antennas having reduced beamwidths. Such a patch antenna comprises a ground plane, a patch radiator, and a feed. The patch radiator is suspended above the ground plane and fed by a central symmetrical loop or by two loops symmetrically disposed about the centre of the patch in a plane normal to the patch between the patch and the groundplane. The feed excites opposite sides of the patch radiator in antiphase.

A need exists for an improved patch-radiator antenna having wider bandwidth.

SUMMARY

In accordance with an aspect of the invention, there is provided a wideband radiating element. The wideband radiating element is a wideband patch- fed cavity radiator (antenna) that has wide bandwidth for a relatively constant beamwidth. The wideband radiating element comprises a section of waveguide, a patch radiator, and one or more tuned loops. The waveguide section has a length that is a quarter of a guide wavelength or about a quarter of the guide wavelength, short circuited at one end, and open circuited at the other end to provide a waveguide aperture. The patch radiator is disposed within the waveguide section as a feed for the waveguide section.

The one or more tuned loops are coupled to the patch radiator as a feed for the patch radiator in a plane normal to the patch radiator. The width of the waveguide section may be configured to be between about 0.7 wavelengths and about 1.3 wavelengths.

Further, the patch radiator is located at a height of 0.125 wavelengths or thereabouts above the short-circuited end of the waveguide section.

The waveguide section may have a cross-section along the longitudinal extent of the waveguide section that is square, rectangular, or circular in form.

The wideband radiating element may further comprise an additional tuning element. The additional tuning element may comprise a dielectric sheet coupled to the waveguide section. The dielectric sheet may be disposed across at least a portion of the waveguide aperture of the waveguide section, or within the waveguide section. The waveguide section, the patch radiator, and the at least one tuned loop may be configured to radiate over a fifty percent (50%) bandwidth with return loss in excess of 15 dB.

The waveguide section, the patch radiator, and the at least one tuned loop coupled together may provide an equal ripple band-pass filter. One tuned loop configured as a feed can be used radiate a single polarization, or two tuned loops orthogonally configured as dual polarization feeds can be used to radiate orthogonal polarizations.

The wideband radiating element may further comprise at least one printed circuit board, where a tuned loop is formed on each printed circuit board. Each tuned loop comprises at least one metalised loop, a feed line, and a capacitor coupled in series to the feed line. The feed line may be a microstrip line. The capacitor comprises a section of microstrip or a portion of a coaxial cable.

A stand-alone antenna comprising a wideband radiating element can be implemented, or an array antenna comprising a number of wideband radiating elements can be implemented. The array antenna may be configured as a wideband, cellular base-station antenna array. In accordance with a further aspect of the invention, there is provided a method of transmitting a signal using a wideband radiating element. The method comprises the steps of: radiating the signal from at least one tuned loop to a patch radiator, the at least one tuned loop in a plane normal to the patch radiator being a feed for the patch radiator; and radiating the signal from the patch radiator disposed within a section of waveguide section as a feed for the waveguide section, the waveguide section having a length that is a quarter of a guide wavelength or about a quarter of the guide wavelength, the waveguide section being short circuited at one end and open circuited at the other end to provide a waveguide aperture. In accordance with a further aspect of the invention, there is provided a method of receiving a signal using a wideband radiating element. The method comprises the steps of: receiving the signal at the patch radiator disposed within a section of waveguide section, the waveguide section having a length that is a quarter of a guide wavelength or about a quarter of the guide wavelength, the waveguide section being short circuited at one end and open circuited at the other end to provide a waveguide aperture; and receiving the signal at at least one tuned loop from a patch radiator, the at least one tuned loop in a plane normal to the patch radiator.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention are described hereinafter with reference to the drawings, in which:

Fig. IA is a perspective view of a wideband radiating element in accordance with an embodiment of the invention;

Fig. IB is a perspective view of tuned loops for exciting dual linear polarization using microstrip loops in the wideband radiating element of Fig. IA;

Fig. 2 is a side elevation view of a wideband radiating element, with a portion of waveguide hidden (shown in cross-section), in accordance with another embodiment of the invention;

Fig. 3 is a side elevation view of a wideband radiating element, with a portion of waveguide hidden (shown in cross-section), in accordance with a further embodiment of the invention; and -A-

Fig. 4 is a side elevation view of a wideband radiating element, with a portion of waveguide hidden (shown in cross-section), in accordance with still another embodiment of the invention.

DETAILED DESCRIPTION

Wideband radiating elements, methods of transmitting and receiving signals using a wideband radiating element, standalone antennas, and array antennas are described hereinafter. In the following description, numerous specific details, including frequency ranges, cables, dielectric materials, conductive materials, waveguide cross-sectional shapes, and the like are set forth. However, from this disclosure, it will be apparent to those skilled in the art that modifications and/or substitutions may be made without departing from the scope and spirit of the invention. In other circumstances, specific details may be omitted so as not to obscure the invention. International (PCT) Patent Publication No. WO 2006/135956 published on 28

December 2006 (International Patent Application No. PCT/AU2006/000814 filed on 15 June 2006 filed in the name of Argus Technologies (Australia) Pty Ltd et al), in its entirety, is incorporated herein by reference.

In accordance with the embodiments of the invention, the wideband radiating element is a wideband patch-fed cavity radiator (i.e., an antenna) that comprises a short section of waveguide that is short circuited at one end and open circuited at the other end. The section of waveguide is fed by a patch radiator disposed within the waveguide; in turn, the patch radiator is fed by at least one tuned loop. The tuned loop is disposed in a plane normal to the patch radiator. In this manner, the patch feeds an open waveguide radiator, i.e. the waveguide section. The wideband radiating element can be used to transmit and/or receive signals. The signal can be fed to the tuned loop and radiated from the patch radiator. In turn, the patch radiator is a feed for the waveguide section, which radiates the signal from the wideband radiating element to transmit the signal. Similarly, a signal can be received by the wideband radiating element. The wideband patch-fed cavity radiator can radiate single or dual linear polarization and is a suitable radiating element for wideband, cellular base-station antenna arrays. Patch radiators are commonly used as radiating elements in cellular base station antennas. Arrays covering UMTS and WiMax/LTE bands (1990MHz - 2750 MHz) have been successfully designed using these radiating elements, but the embodiments of the invention are not limited in application to these particular bands. The resulting radiating element, i.e. the wideband patch-fed cavity radiator, is capable of operating over a fifty percent (50%) bandwidth with return loss in excess of 15 dB. The variation in radiation pattern across this band is relatively small. For example, a cellular base-station panel antenna designed to have a 65° horizontal beamwidth varies in 3 dB beamwidth by less than ±7° over a 46% bandwidth. In the tuned loop, a capacitor or a section of transmission line can be coupled in series to a metalised loop to form a resonating element. One or two tuned loops can be used to obtain a symmetrical feed. With optimum selection of dimensions, the configuration of the wideband radiating element becomes a three or more resonator filter that can be designed to match the impedance of the input transmission line of a feed to the impedance at the open waveguide radiator. The waveguide section has a length that is a quarter of a guide wavelength or about a quarter of the guide wavelength. The width of the waveguide is typically between 0.7 wavelengths and 1.3 wavelengths. The bandwidth of the resulting radiating element is significantly increased by the waveguide section. The waveguide, suitably dimensioned, also stabilises the radiation pattern, so that there is minimal variation in radiation pattern across the impedance bandwidth. Optionally, a dielectric body of suitable thickness, physical characteristics, and dielectric constant can be located within the waveguide as a tuning element to provide adjustment of the Q of the open waveguide radiator and can be used to optimise the impedance characteristics across the band of operation.

Dual linear polarization can be achieved by means of two orthogonal crossed loops. An equi-ripple impedance response can be achieved by suitably adjusting the resonant frequencies and couplings between the three resonators, namely the tuned loop, the patch and the waveguide section. The wideband radiating element(s) can be used to implement a stand-alone antenna, or an array antenna comprising a number (e.g., 10) of wideband radiating elements as a cellular base-station antenna array. The wideband radiating element provides a relatively constant beamwidth and wide bandwidth. These and other aspects are described hereinafter in greater detail with reference to the embodiments shown in Figs. 1 to 4.

Fig. IA is a perspective view of a wideband radiating element, or wideband patch- fed cavity radiator, 100 configured with two orthogonal feeds in accordance with an embodiment of the invention. The wideband radiating element 100 comprises a patch radiator 110, two tuned- loop feeds 128, and a section of waveguide 130. To enable viewing of components of the tuned loops 128 in Fig. IA, portions of the patch 110 and a wall of the waveguide section 130 are removed in the drawing.

Fig. IB illustrates, in isolation from other components of the wideband radiating element 100, the two tuned- loop feeds 128(A), 128(B) for exciting dual linear polarization. The printed circuit boards 120 are orthogonally configured relative to each other in a cross- or X-shape when viewed in plan from above. In Fig. IB, the two tuned loops 128 are differentiated by the parenthetical designations A and B. Each tuned loop 128 comprises a pair of metalised loops 124 formed on one planar surface of the printed circuit board 120 and microstrip lines 122 and series capacitors 126 are formed on the opposite planar surface of the printed circuit board 120. The microstrip lines 122 and series capacitors 126 are implemented by sections of microstrip in this embodiment. For each tuned loop 128, the microstrip line feeds 122 are configured in antiphase, as best seen on printed circuit board 120(A) in Fig. IB.

The depicted waveguide section 130 is square in cross-section (viewed from above in plan) and is made of conductive material(s), e.g. metal. The waveguide section 130 can alternatively have a cross-section along the longitudinal extent of the section that is rectangular or circular in form, for example. The waveguide section 130 has a length (L) that is a quarter of a guide wavelength or approximately that length (in a vertical direction as depicted in Fig. IA). The waveguide section 130 is short circuited at one end 132 (bottom surface) and open circuited at the other end 134 where radiation of the wideband radiating element 100 occurs. The printed circuit boards 120 are fastened or connected to the short circuited portion 132 of the waveguide section 130. As seen best in Fig. IB, the printed circuit boards have tabs 150 formed on opposite sides of the boards 120. The bottom tabs can be used for interlocking engagement with holes (not shown) formed in the shorted section 132 of the waveguide section 130 and for electrical interconnection with the waveguide section 130. The tabs 150 should be connected to (soldered to) the patch radiator 110 and the shorted section 132 of the waveguide section 130.

The patch radiator 110 is a thin, circular plate or disc made of a conductive material, e.g. metal, but other shapes can be practiced. In this embodiment, the patch radiator 110 is connected to the printed circuit boards 120 on which the loops 124 are formed by interlocking engagement of the tabs 150 shown in Fig. IB with corresponding holes (not shown) in the patch radiator 110. Electrical interconnection between the loops 124 and the patch radiator 110 is also formed. The patch radiator 110 may be soldered to the printed circuit boards 120. However, in an alternative configuration, the patch radiator 110 may be separately supported for example by plastic posts (not shown). Thus, the patch radiator 110 is suspended above the shorted portion 132 of the waveguide section 130 and is in concentric alignment with the waveguide aperture provided by the open circuited portion 134 of the waveguide section 130. The shorted portion 132 of the waveguide section 130 functions as a groundplane.

The patch radiator is fed by a tuned loop in a plane normal to the patch. In the embodiment of Fig. 1, the patch radiator 110 is fed by two tuned loops 128(A), 128(B) formed on respective printed circuit boards 120 in planes normal to the patch 110. Series resonant circuits are formed by the inductances of the metalised loops 124 with series capacitances implemented as sections of microstrip lines 126. The series capacitance can be implemented in a variety of ways, including as a lumped capacitor or a short section of transmission line, such as coaxial cable or microstrip line. The tuned loop 128(B) is coupled to a coaxial cable 160 in Fig. IB and comprises microstrip line feeds 122, the pair of metalised loops 124(B), and the series capacitances 126. For ease of illustration only, the coaxial cable is not depicted in Fig. IA. The feeds 122 and series capacitances 126 for the tuned loop 128(B) are not shown in Fig. IB, because those components of the tuned loop 128(B) are on the opposite side of printed circuit board 120(B), which is not visible in Fig. IB. The counterpart parts 122(A), 126(A) of the other tuned loop 128(A) are visible. Another coaxial cable feed behind the printed circuit board 120(A) is not visible in Fig. IB. The coaxial cable 160 is used to make an external connection to the radiating element 100. A portion of the outer plastic sheath of the cable 160 is removed to expose the inner conductive shield of the coaxial cable, which is attached (soldered) to the metalisation of the loop 124(B). The centre conductor of the coaxial cable 160 is connected to the microstrip lines 122 (not visible) of the tuned loop 128B on the opposite side through the printed circuit board 120(B). The patch 110 and the tuned loop(s) 128 form a pair of coupled resonators.

This configuration (without the waveguide section 130) can be used as a radiating element. By suitably selecting the characteristics of these resonators and their coupling, a two-resonator filter can be designed to obtain a double-tuned return loss response. The two orthogonal loops 128(A), 128(B) are used to provide a dual- polarised antenna. The two polarizations are radiated across the two diagonals defined by the corners of the square waveguide. Typically a 25 - 30% impedance bandwidth at 18 dB return loss can be obtained in this way with a patch 110 located at a height of 0.125 wavelengths above a groundplane. Increased height of the patch 110, while increasing bandwidth leads to variation and degradation in the radiation pattern.

Addition of the waveguide section 130 adds bandwidth, and the additional resonator broadens the bandwidth further. The wideband radiating element 100 may also incorporate one or more tuning elements. The additional tuning element may be, for example, a dielectric sheet (not shown in Fig. 1) coupled to the waveguide section, across at least a portion of the waveguide aperture 134 or within the waveguide section 130. For example, the dielectric sheet may be a solid plastic body, or a plastic body with patterned apertures formed in the body, adapted to fit within the waveguide section or across the waveguide aperture as a cover.

Alternatively, pieces of metal may be located in the waveguide for example as etched shapes on printed circuit boards placed in the waveguide. Holes can be formed in the waveguide section 130 (e.g., in the shorted section 132) for external connection to the microstrip line 122 feeding the loops 124. Changes can be made to the embodiment depicted in Fig. 1 to provide additional embodiments of the invention as shown in

Figs. 2 to 4 hereinafter.

Fig. 2 illustrates another wideband radiating element 200, i.e. a wideband patch- fed cavity radiator, with a single tuned- loop feed 128 implemented using a single loop 224 and a transmission line or a coaxial cable 226 (e.g., 50 ohm cable) in accordance with a further embodiment of the invention.

The configurations and details of the patch radiator 210 and the waveguide section 230 are the same as those of the patch radiator 110 and the waveguide section 130 of Fig. 1. The patch radiator 210 may be suspended above the tuned loop 228 by plastic posts (not shown), for example. The tuned loop 228 is formed again in a plane orthogonal to that of the patch radiator 210.

The loop 224 may be implemented as etched cladding on a printed circuit board 220 and is similar in function but different in configuration to the loops 124 of Fig. 1. The printed circuit board 220 is connected or fastened to the shorted section of the waveguide section 230. A portion of the loop 224 is formed using the shorted section 232 of the waveguide 230, and the remainder of the loop 224 is formed by the cladding on the same side of the printed circuit board 220 (facing the viewer in Fig.

2). A small gap 229 is formed in the loop 224. Small tabs 250 are optionally formed in the loop 224. The tabs 250 are useful for adjusting the coupling of the tuned-loop

228 to the patch 210.

The loop 224 is excited across the gap 229. A piece of coaxial cable 260 used to feed the radiating element 200 is brought up one side of the loop 224 (left side in

Fig. 2), with the exposed conductive shield connected to that side of the loop 224. This may be done by soldering, for example. The exposed centre conductor 240 of the coaxial cable 260 spans the gap 229 in the loop 224 and is connected to the other side of the loop 224 through a capacitor. The capacitor is implemented as a short open-circuit section 242 of the same cable 260 with its conductive shield connected to the other side of the loop 224. The length of this short section of coaxial cable 242 is selected to resonate with the inductance of the loop 224. The cable 260 is introduced through a hole in the shorted section 232 of the waveguide section230. A portion of the external insulator cladding of the cable 260 is shown as white body in Fig. 2.

A single-tuned loop 228 is formed on the printed circuit board 220 for a single polarisation in the embodiment of Fig. 2. However, the wideband radiating element 200 of Fig. 2 can be modified for dual polarisation by the provision of another tuned loop similarly configured on another printed circuit, which can be orthogonally configured relative to the depicted printed circuit board 220.

Fig. 3 illustrates a wideband radiating element 300, i.e. a wideband patch-fed cavity radiator, with a microstrip implementation of a single-tuned loop feed 328 in accordance with yet another embodiment of the invention. This configuration of the wideband radiating element 300 is similar to that of Fig. 2, with the principal difference being the use of microstrip 322, 326 in place of the coaxial cable 260, 242 in Fig. 2.

Again, the configurations of the patch radiator 310 and the waveguide section 330 are the same as those of the patch radiator 110, 210 and the waveguide section 130, 230 of Figs. 1 and 2. The patch radiator 310 is suspended above a single printed circuit board 320, which can be done using plastic posts (not shown), for example. The tuned loop 328 is formed in a plane orthogonal to that of the patch radiator 310. A printed circuit board 320 is connected or fastened to the shorted section 332 of the waveguide section 330. hi this embodiment, the metalised loop 324 is formed on the rear surface (indicated by dashed lines) of a printed circuit board 320 and has the same function and a similar configuration to the loop 224 of Fig. 2. The optional tabs 250 of Fig. 2 are omitted in this embodiment. A portion of the loop 324 is formed using the shorted section 332 of the waveguide 330. A small gap 329 is formed in the loop 324. A microstrip track 322 (facing the viewer) is formed on the printed circuit board 320 and is used to feed the loop 324 implemented on the opposite side of the board 320 in Fig.3. The microstrip track 322 overlays the corresponding portion of the loop 328 formed on the opposite side of the printed circuit board. A short length 340 of the microstrip track 322 extends across the gap 329 in the loop 324. The capacitor 326 is formed of microstrip track on the other side of the loop 324. The microstrip line 322 may be fed from another printed circuit board below the waveguide section 330 through a hole in the shorted section 332 of the waveguide section 330, or alternatively by means of a coaxial cable through a hole in the shorted section 332 of the waveguide section 330, for example. Again, the section 326 of microstrip track 322 to implement the capacitor is selected to resonate with the inductance of the loop 324. Again, while wideband radiating element 300 of Fig. 3 implements a single polarization, this embodiment can be readily modified to implement dual polarization. Fig. 4 illustrates a wideband radiating element 400 with a different microstrip implementation having two loops 424 fed in antiphase in accordance with a further embodiment of the invention. Again, the configurations of the patch radiator 410 and the waveguide section 430 are the same as those of the patch radiator 110 and the waveguide section 130 of Fig. 1. In this embodiment, the patch radiator 410 is mounted onto a single printed circuit board 420, which is connected or fastened to the shorted section of the waveguide section 430. This configuration is basically the same as that shown in Fig. 1, but has a single tuned-loop 428 for a single polarization rather than two tuned loops 128(A), 128(B) for dual polarisation.

Two microstrip circuits 422are formed in antiphase on a planar surface of the printed circuit board 420 to provide the two tuned loops 428, each comprising an inductance and capacitance in series. Two loops 424 with gaps 429 (shown with dotted lines in Fig. 4) are implemented as metallisation on the reverse side of the board 420. Again, short lengths of track 440 extend across the gaps 429 in the loops 424. Series capacitors 426 implemented with microstrip are formed on the other sides of the loops 424. A black dot in Fig. 4 indicates where an external connection (not shown) is made to the microstrip lines 422. Wideband radiating elements, methods of transmitting and receiving signals using a wideband radiating element, standalone antennas, and array antennas have been described. In view of this disclosure, it will be apparent to one skilled in the art that modifications and/or substitutions may be made without departing from the scope and spirit of the invention.

Claims

CLAIMS:

1. A wideband radiating element, comprising: a section of waveguide having a length that is a quarter of a guide wavelength or about a quarter of the guide wavelength, said waveguide section being short circuited at one end and open circuited at the other end to provide a waveguide aperture; a patch radiator disposed within said waveguide section as a feed for said waveguide section; and at least one tuned loop coupled to said patch radiator as a feed for said patch radiator in a plane normal to said patch radiator.

2. The wideband radiating element as claimed in claim 1, wherein the width of said waveguide section is between about 0.7 wavelengths and about 1.3 wavelength.

3. The wideband radiating element as claimed in claim 1 or 2, wherein said patch radiator is located at a height of 0.125 wavelengths or thereabouts above said short-circuited end of said waveguide section.

4. The wideband radiating element as claimed in any one of claims 1 to 3, wherein said waveguide section has a cross-section along the longitudinal extent of the waveguide section that is square, rectangular, or circular in form.

5. The wideband radiating element as claimed as claimed in any one of the preceding claims, further comprising an additional tuning element.

6. The wideband radiating element as claimed in claim 5, wherein said additional tuning element comprises a dielectric sheet coupled to said waveguide section.

7. The wideband radiating element as claimed in claim 6, wherein said dielectric sheet is disposed across at least a portion of the waveguide aperture of said waveguide section.

8. The wideband radiating element as claimed in claim 6, wherein said dielectric sheet is disposed within said waveguide section.

9. The wideband radiating element as claimed in any one of the preceding claims, wherein said waveguide section, said patch radiator, and said at least one tuned loop are configured to radiate over a fifty percent (50%) bandwidth with return loss in excess of 15 dB.

10. The wideband radiating element as claimed in any one of the preceding claims, wherein said waveguide section, said patch radiator, and said at least one tuned loop coupled together provide an equal ripple band-pass filter.

11. The wideband radiating element as claimed in any one of the preceding claims, comprising one tuned loop configured as a feed to radiate a single polarization.

12. The wideband radiating element as claimed in any one of claims 1 to 10, comprising two tuned loops orthogonally configured as dual polarization feeds to radiate orthogonal polarizations.

13. The wideband radiating element as claimed in any one of the preceding claims, further comprising at least one printed circuit board, a tuned loop formed on each printed circuit board.

14. The wideband radiating element as claimed in any one of the preceding claims, wherein each tuned loop comprises at least one metalised loop.

15. The wideband radiating element as claimed in claim 14, wherein each tuned loop further comprises a feed line.

16. The wideband radiating element as claimed in claim 14 or 15, wherein said feed line is a microstrip line.

17. The wideband radiating element as claimed in any one of claims 15 or 16, wherein each tuned loop further comprises a capacitor coupled in series to said feed line.

18. The wideband radiating element as claimed in claim 17, wherein said capacitor comprises a section of microstrip or a portion of a coaxial cable.

19. A stand-alone antenna, comprising a wideband radiating element as claimed in any one of the preceding claims.

20. An array antenna comprising a plurality of wideband radiating elements, each radiating element as claimed in any one of the preceding claims.

21. The array antenna as claimed in claim 20 configured as a wideband, cellular base-station antenna array.

22. A method of transmitting a signal using a wideband radiating element, said method comprising the steps of: radiating said signal from at least one tuned loop to a patch radiator, said at least one tuned loop in a plane normal to said patch radiator being a feed for said patch radiator; and radiating said signal from said patch radiator disposed within a section of waveguide section as a feed for said waveguide section, said waveguide section having a length that is a quarter of a guide wavelength or about a quarter of the guide wavelength, said waveguide section being short circuited at one end and open circuited at the other end to provide a waveguide aperture.

23. A method of receiving a signal using a wideband radiating element, said method comprising the steps of: receiving said signal at said patch radiator disposed within a section of waveguide section, said waveguide section having a length that is a quarter of a guide wavelength or about a quarter of the guide wavelength, said waveguide section being short circuited at one end and open circuited at the other end to provide a waveguide aperture; and receiving said signal at at least one tuned loop from a patch radiator, said at least one tuned loop in a plane normal to said patch radiator.

24. The method as claimed in claim 22 or 23, wherein said waveguide section has a cross-section along the longitudinal extent of the section that is square, rectangular, or circular in form.

25. The method as claimed in claim 22 or 23, wherein the width of said waveguide section is between about 0.7 wavelengths and about 1.0 wavelength.

26. The method as claimed in any one of claims 22 to 25, wherein said patch radiator is located at a height of 0.125 wavelengths or thereabouts above said short circuited end of said waveguide section.

27. The method as claimed in any one of claims 22 to 26, wherein said waveguide section, said patch radiator, and said at least one tuned loop are configured to radiate over a fifty percent (50%) bandwidth with return loss in excess of 15 dB.

28. The method as claimed in any one of claims 22 to 27, wherein said waveguide section, said patch radiator, and said at least one tuned loop are configured to radiate single or dual linear polarization.