GB2396745A

GB2396745A - Miniaturised dielectric resonator antennas with increased bandwidth

Info

Publication number: GB2396745A
Application number: GB0228633A
Authority: GB
Inventors: Zhipeng Wu
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-12-07
Filing date: 2002-12-07
Publication date: 2004-06-30
Anticipated expiration: 2022-12-07
Also published as: GB2396745B; GB0228633D0

Abstract

This invention relates to miniaturised dielectric resonator antennas of increased bandwidth. This is achieved by introducing a metal strip 3 on the top surface of a miniaturised dielectric resonator antenna 1 coupled by a microstrip line 4, an on-surface strip, a ground backed coplanar waveguide, a slot, a probe, dielectric guide or other wave guiding structures. The dielectric resonator antenna is made of ceramic or other low-loss high permittivity materials. The metal strip can be in different shapes and sizes, and it can be printed or stuck onto the top surface of the dielectric resonator antenna at different positions. The metal strip causes the lowest mode of the dielectric resonator antenna to degenerate. It may also introduce additional modes. These degenerated and additional modes are well matched to the impedance of planar or non-planar feed line, which gives rise to increased impedance bandwidth.

Description

MlNlATURlSED DlF,LF,CTRIC RESONATOR ANTF,NNAS WITH INCREASED BANDWIDTH

FIELD OF TIIE INVENTION

This invention relates to minialurised dielectric resonator antennas of increased bandwidth, and more particularly to a dicicctric r esonator antenna having a metal strip on the top surface of the dielectric resonator.

BACKGROUND OF THE INVENTION

Dicicctric resonator antennas (DRAB) are known as antennas made ol low loss ceramics or other high pennittivity dicicciric materials. The dielectric material forms a resonator hi rectangular, cylindrical, hemispilcrical or other geometries. Thc dielectric resonator has a nunbcr ol resonant modes with corresponding r esonance frequencies. Thc resonant modes which have cicctromagnetic Acids not entirely confined in the resonator arc used for electromagnetic radiation. Thc mode which has the lowest resonance frequency is the lowest mode of the resonator. The lowest. mode is preferred for antenna application as a resonator operating at this lowest node has the smallest physical dimensions for a given opcra.ting Irequcncy. I he lowest modes ol rectangular and cylindrical dielectric resonators arc 1 LO and HE modes respectively. These modes can be excited using a proUc, microstrip line, slot, dielectric guide, dielectric hilage guide and coplanar waveguide. Thc dielectric resonator is positioned h1 the teed structrrc so that good impedance matchhig can be obtained at the resonance frequency so as to produce efficient radiation. A DRA opcrathg at the lowest mode has broadside radiation with directivity weakly dependent on the dielectric constant of the material and resonator dimensions.

Thc resonance frequency of the lowest mode of the DRA is a function ol the dimensions of the resonator and it is inversely proportional lo the square root. of the relative dielectric constant ol the material, r:,.. Tl1c impedance bandwidth of the DRA is diversely proportional to pal i, and it also dclcnds on the dimensions of the resonator, particularly on the lengt}l-to-hcigilt aspect ratio.

The bandwidth at V5WR-2 can vary front over 10% for.:,=10 to 3 /O for s-40, and further to I A, for E-=90, but it generally increases with the Icngill-to-lleigilt aspect ratio. 'lhc properties ol DRAs have been reviewed in the article "Dicicctric Resonator Antennas A review and general design relations lor resonant frequency and bandwidth", by R. K. Mongia and 1'. Barthia, h

International Journal of Microwave and Millimeter-wave Computer-aidcd Engineering, Vol.4, No.3, 1994, pp230-247.

For a given operating frequency, the dielectric resonator can be miniaturized by using a high pcrmittivity material with ú,=30 or higher. This leads to a smaller, miniaturized DRA. I-lowever, t]JC USC of high pennittivity material also leads to smaller impedance bandwidth, which can restrict the benefit of size reduction. 'I'he reduction in bandwidth of a niniaturised DRA can be compensated by increasing the length-to- height aspect ratio of the DRA. This leads to a low profile miniaturized DRA as described in, for example, the article "Low profile dielectric resonator antennas using a very high permittivity material", by R K Mongia, A Ittipiboon, M Cwhaci, in Electronics Letters, Vol.3O, No.17, 1994, ppl362-1363. However, a rniniaturised BRA generally has a narrow impedance bandwidth. A technique for improving the impedance bandwidth is to use stacked DRAB, as described in the article "Broadband stacked dielectric resonator antennas", by A A Kishk, B Ahn and D KajI'ez, in Electronics Letters, Vol.25, No.18, 1989, ppl232-1233. This technique however increases the overall size ol' the antenna. Other techniques by combining with a microstrip patch antenna, or by introducing a notch or multi-

segments have been described in patents US 5,453,754 and EP ()8()143(jA2 These techniques however complicate the fabrication of antenna.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a novel method, which can be easily implemented, for increasing the impedance bandwidth of miniaturized rectangular and cylindrical DRAs for wireless communications at microwave and millirnetre wave frequencies.

According to this invention, the bandwidth of a miniaturized rectangular or cylindrical DRA is greatly increased by introducing a metal strip on the top surface of the miniaturized DRA fed or coupled by a microstrip line, an on-surface strip, a ground backed coplanar wavequide, a slot, a probe, dielectric guide or other wave guiding structures.

The mirliattrised rectangular or cylindrical DRA is made of ceramic or other materials with relative dielectric constant, c,, of 30 or higher.

The metal strip can be in different, regular or irregular, long-thin or short-fat shapes, and in different sizes. It can be printed or stuck onto the top surface of the DRA at different positions and in different orientations. The optimal shape, size, position and orientation depend on the dimensions and dielectric properties of the DRA and on the feed mechanism employed. Two or more metal strips of the same or different shapes can also be used. The metal strip causes the lowest mode to degenerate. The metal strip may also lead to reduced resonance frequencies of the degenerated modes. It may also introduce other modes in addition to the degenerated modes.

These degenerated and additional modes are well matched to the impedance of planar or non-

planar feed line, which gives rise to increased impedance bandwidth.

These and other aspects of the invention, preferred embodiments and variants thereof, and advantages will become appreciated and understood by those skilled in the art from the following detailed description and drawings.

BRIEF DECSRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of examples only, with reference to the accompanying drawings, in which: FIG.la is a top view of a microstrip line side-coupled rectangular DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.lb is a side view of a microstrip line side-coupled rectangular DRA with a metal strip on the top surface of the DRA shown in FIG. la; FlG.2a is a top view of a microstrip line side-coupled cylindrical DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.2b is a side view of a microstrip line side-coupled cylindrical DRA with a metal strip on the top surface of the DRA shown in FIG.2a;

FIG.3a is a top view of a microstrip line end-coupled rectangular DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.3b is a side view of a microstrip line end-coupled rectangular DRA with a metal strip on the top surface of the DRA shown in FIG.3a; FIG.4a is a top view of a microstrip line end-coupled cylindrical DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.4b is a side view of a microstrip line end-coupled cylindrical DRA with a metal strip on the top surface of the DRA shown in FIG.4a; FlG.5a is a top view of an on-surface-strip coupled rectangular DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.5b is a side view of a on-surface-strip coupled rectangular DRA with a metal strip on the top surface of the DRA shown in FIG.5a when the height of the DRAis greater than the thickness of the substrate; FIG. 5c is a side view of a on-surface-strip coupled rectangular DRA with a metal strip on the top surface of the DRA shown in FlG.5a when the height of the DRAis the same as the thickness of the substrate; FIG.6a is a top view of an on-surface-strip coupled cylindrical DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FlG.6b is a side view of a on-surfacestrip coupled cylindrical DRA with a metal strip on the top surface of the DRA shown in FlG.6a when the height of the DRAis greater than the thickness of the substrate;

FIG.6c is a side view of a on-surface-strip coupled cylindrical DRA with a metal strip on the top surface of the DRA shown in FIG.6a when the height of the DRAis the same as the thickness of the substrate; FIG.7a is a top view of a coplanar waveguide end-coupled rectangular DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.7b is a side view of a coplanar waveguide end-coupled rectangular DRA with a metal strip on the top surface of the DRA shown in FIG.7a; FIG.8a is a top view of a coplanar waveguide end-coupled cylindrical DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FlG.8b is a side view of a coplanar waveguide end-coupled cylindrical DRA with a metal strip on the top surface ofthe DRA shown in FIG.8a; FIG.9a is a top view of a slot coupled rectangular DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.9b is a side view of a slot coupled rectangular DRA with a metal strip on the top surface of the DRA shown in FIG.9a; FlG.lOa is a top view of a slot coupled cylindrical DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.lOb is a side view of a slot coupled cylindrical DRA with a metal strip on the top surface ofthe DRA shown in FlG.IOa; FIG.1 la is a top view of a probe coupled rectangular DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention;

lFIG.I Ib is a side view of a probe coupled rectangular DRA with a metal strip on the top surface of the DRA shown in FIG.11 a; FIG.12a is a top view of a probe coupled cylindrical DRA with a metal strip on the top surface of the DRA which provides increased impedance bandwidth in accordance with the invention; FIG.12b is a side view of a probe coupled cylindrical DRA with a metal strip on the top surface of the DRA shown in FIG.12a; FIG.13 is a plot of the measured reflection coefficient, lS l in dB against frequency, of a microstrip side coupled rectangular DRA of the size 12mm (length) x 12mm(width) x 4mm (height), and or =37 with a 4mm x 4mm metal strip placed towards the top-left corner of the top surface of the DRA (see FIGl.a) where the microstrip line is printed on a substrate of or =2.2 and thickness of 0.79mm, and has a width of 2.4mm.

FIG.14 is a plot of the measured reflection coefficient, lS l in dB against frequency, of a microstrip end coupled rectangular DRA of the size 12mm (length) x 12mm(width) x 4mn1 (height), and Or =37 with a 7.5mm x 1.2mm metal strip placed at an angle at the centre of the top surface of the DRA (see FIG3.a) where the microstrip line is printed on a substrate of or =2.2 and thickness of 0.79mm, and has a width of 2.4mm.

FIG.15 is a plot of the measured reflection coefficient, lS l in dB against frequency, of an on-surface-strip coupled rectangular DRA of the size 7mm (length) x 7mm(width) x 1.5mm (height), and or =92 with a 3mm x 1 mm metal strip placed at an angle on the bottom-right corner of the top surface of the DRA (see FIG5.a) where the on surface-strip is connected to a microstrip line of width 1.8mm printed on a substrate of sr = 10.5 and thickness of 1.6mm.

FIG.16 is a plot of the measured reflection coefficient, USA al in dB against frequency, of a ground backed coplanar waveguide coupled rectangular DRA of the size 12mm (length) x 12mm(width) x 4mm (height), and or =37 with a 8mm x 2.5mm metal strip placed at an angle on the bottom-left corner of the top surface of the DRA

(see FIG7.a) where the central coplanar strip is printed on a substrate of or =2.2 and thickness of 0.79mm, and has a width of 2.4mm.

DETAILED DESCRIPTION OF THE INVENTION

FIG.la shows a top view of a microstrip side-coupled rectangular DRA I with a metal strip 3 on the top surface of the DRA 1. The rectangular DRA 1 is positioned on top of the microstrip 4 printed on a substrate 5 with a ground plane 6, and along the side of the microstrip 4 with a small area of overlapping. The front and back sides of the rectangular DRA 1 are shown to be parallel to the microstrip line, but the DRA 1 can be rotated slightly so that the front and back sides form an acute angle with respect to the microstrip line 4. The metal strip 3 causes the lowest mode TEA to degenerate. It may also introduce other modes in addition to the degenerated modes.

These modes are well matched to the impedance of microstrip feed line 4, leading to an increased antenna impedance bandwidth. A side view of the microstrip side-coupled rectangular DRA l with a metal strip 3 on the top surface of the DRA 1 is shown in FIG. lb. FIG.2a shows a top view of a microstrip side-coupled cylindrical DRA 2 with a metal strip 3 on the top surface of the DRA 2. The structure is the same as that in FIG.la, except that the dielectric resonator is in cylindrical geometry. The metal strip 3 causes the lowest mode HE to degenerate. It may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of microstrip feed line 4, leading to an increased antenna impedance bandwidth. A side view of the microstrip side-coupled cylindrical DRA 2 with a metal strip 3 on the top surface of the DRA l is shown in FIG.2b.

FIG.3a shows a top view of a microstrip end-coupled rectangular DRA I with a metal strip 3 on the top surface of the DRA 1. The rectangular DRA I is positioned on top of the microstrip 4 printed on a substrate 5 with a ground plane 6, and to the end of the microstrip 4 with a small overlapping section. The metal strip 3 causes the lowest mode TEA to degenerate and it may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of microstrip feed line 4, leading to an increased antenna impedance bandwidth. A side view of the microstrip end-coupled rectangular DRA 1 with a metal strip 3 on the top surface of the DRA 1 is shown in FlG.3b.

FIG.4a shows a top view of a microstrip end-coupled cylindrical DRA2 with a metal strip 3 on the top surface of the DRA2. The structure is the same as that in FIG.3a, except that the dielectric resonator is in cylindrical geometry. The metal strip 3 causes the lowest mode HE to degenerate. It may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of microstrip feed line 4, leading to an increased antenna impedance bandwidth. A side view of the microstrip end-coupled cylindrical DRA2 with a metal strip 3 on the top surface of the DRAlis shown in FIG.4b.

FlG.5a shows a top view of an on-surface-strip coupled rectangular DRAI with a metal strip 3 on the top surface of the DRAI. The rectangular DRAlis positioned on top of the ground plane 6, and is partly or fully embedded in a substrate 5. The on-surface-strip is attached to the one or two surfaces of the DRAI. It may consist of one vertical strip 7 on one side surface of the DRA I and one connected horizontal strip 8 on the top surface of the DRA1. The on-surface-strip is connected to a microstrip feed line 4 printed on the substrate 5. The substrate beyond the end of the microstrip line may also be removed, leaving a ground plane to support the DRAI. The metal strip 3 on the top surface of the DRA1 causes the lowest mode TEN to degenerate and it may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of microstrip line 4, leading to an increased antenna impedance bandwidth. A side view of on-surface-strip coupled rectangular DRAI with a metal strip 3 on the top surface of the DRAlis shown in FIG.5b for a resonator with a height greater then the thickness of the substrate 5, and in FIG.5c for a resonator with a height equal or comparable to the thickness of the substrate 5.

FIG.6a shows a top view of an on-surface-strip coupled cylindrical DRA2 with a metal strip 3 on the top surface of the DRA2. The structure is the same as that in FIG.5a, except that the dielectric resonator is in cylindrical geometry. The metal strip 3 causes the lowest mode HE to degenerate. It may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of microstrip line 4, leading to an increased antenna impedance bandwidth. A side view of the on-surface-strip coupled cylindrical DRA2 with a metal strip 3 on the top surface of the DRAlis shown in FIG.6b for a resonator with a height greater than the thickness of the substrate 5, and in FIG. 6c for a resonator with a height equal or comparable to the thickness of the substrate 5.

FIG.7a shows a top view of a ground backed coplanar waveguide coupled rectangular DRAI with a metal strip 3 on the top surface of the DRAI. The rectangular DRAlis positioned partly

on top of the upper ground plane 9 which is connected to the lower ground plane 6 via conducting pins l O through the substrate 5 or via metal surfaces, and partly on top of the central strip 4 of the coplanar waveguidc. There exists a gap between the end of the central strip 4 and the upper ground plane 9. The metal strip 3 on the top surface of the DRAI causes the lowest mode TEA to degenerate and it may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of feed line, leading to an increased antenna impedance bandwidth. A side view of ground backed coplanar waveguide coupled rectangular DRAI with a metal strip 3 on the top surface of the DRAlis shown in FIG.7b.

FIG.8a shows a top view of a ground backed coplanar waveguide coupled cylindrical DRA2 with a metal strip 3 on the top surface of the DRA2. The structure is the same as that in FIG.7a, except that the dielectric resonator is in cylindrical geometry. The metal strip 3 causes the lowest mode HEMPS to degenerate. It may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of feed line, leading to an increased antenna impedance bandwidth. A side view of the ground backed coplanar waveguide coupled cylindrical DRA2 with a metal strip 3 on the top surface of the DRAlis shown in FIG.8b.

FlG.9a shows a top view of a slot coupled rectangular DRAI with a metal strip 3 on the top surface of the DRA1. The slot 11 is located on the ground plane 6, and it is further coupled by a microstrip line 4 printed on a substrate 5, sharing the same ground plane 6. The microstrip line 4 extends beyond the position of the slot l l by a short length, typically a quarter wavelength or less. The rectangular DRAlis positioned on top of the ground plane 6, covering the whole area of the slot 11. The metal strip 3 on the top surface of the DRA1 causes the lowest mode TEN to degenerate and it may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of microstrip line 4, leading to an increased antenna impedance bandwidth. A side view of slot coupled rectangular DRA1 with a metal strip 3 on the top surface of the DRAlis shown in FIG.9b.

FIG.IOa shows a top view of a slot coupled cylindrical DRA2 with a metal strip 3 on the top surface of the DRA2. The structure is the same as that in FlG.9a, except that the dielectric resonator is in cylindrical geometry. The metal strip 3 causes the lowest mode HEIR to degenerate. It may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of microstrip line 4, leading to an increased antenna impedance bandwidth. A side view of the slot coupled cylindrical DRA2 with a metal strip 3 on the top surface of the DRAlis shown in FIG. 1 Ob.

FlGlla shows a top view of a probe-fed rectangular DRAI with a metal strip 3 on the top surface of the DRAI. The probe 13 is mounted a ground plane 12 with a dielectric spacer 14.

The probe is further connected to a planar or coaxial feed line. The rectangular DRAlis positioned on top of the ground plane 12, and is attached to the probe 13 on one side surface. The metal strip 3 on the top surface of the DRAI causes the lowest mode TEN to degenerate and it may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of feed line, leading to an increased antenna impedance bandwidth. A side view of probe-fed rectangular DRA1 with a metal strip 3 on the top surface of the DRAlis shown in FIG. I 1 b.

FIG.12a shows a top view of a probe-fed cylindrical DRA 2 with a metal strip 3 on the top surface of the DRA 2. The structure is the same as that in FlG.9a, except that the dielectric resonator is in cylindrical geometry. The metal strip 3 causes the lowest mode HE to degenerate. It may also introduce other modes in addition to the degenerated modes. These modes are well matched to the impedance of feed line, leading to an increased antenna impedance bandwidth. A side view of the probe-fed cylindrical DRA 2 with a metal strip 3 on the top surface of the DRAlis shown in FIG. 1 2b.

In addition to the feed or coupling mechanism shown in FIGs.1-12, the rectangular DRA1 or cylindrical DRA 2 with a metal strip 3 on the top surface of the DRA can be fed by using a dielectric guide. The metal strip 3 causes the lowest modes, TEN or HE As, to degenerate. These degenerated modes are well matched to the impedance of the feed line, leading to an increased antenna impedance bandwidth.

In additional to causing the lowest mode of the DRA1 or 2 to degenerate, the metal strip 3 in FlGs.1-12 may also lead to reduced resonance frequencies of the degenerated modes. The frequency reduction implies a smaller dielectric resonator for a given operating frequency.

The metal strip 3 in FIGs.l-12 can be in different, regular or irregular, long-thin or short-fat shapes, and in different sizes. It can be printed or stuck onto the top surface of the DRAI or 2 at different positions and in different orientations. The optimal shape, size, position and orientation depend on the dimensions and dielectric properties of the DRA and the feed mechanism employed. Some have already been illustrated in FIGs.1-12. Instead of one, two or more metal

strips of the same or different shapes may also be used to obtain an increased impedance bandwidth, based on the same principle.

The part of the bottom surface of the DRAI or 2 overlapping the metal strip 4 or ground plane 6, 9 or 12 can be metallised, and soldered onto the metal strip or ground plane to gain mechanical support. In addition, one or more small metal patches can be printed on the substrate 5, and the corresponding areas on the bottom surface of the DRA1 or 2 can be metallised and soldered onto the metal patches to gain mechanical support.

The single substrate structures shown in FIGs. 1-10 can be equivalently replaced by multi-layered structures having multiple substrates and conductor layers.

FIG. 13 shows an example of the measured reflection coefficient, lS l in dB against frequency, of a microstrip side-coupled rectangular DRA with a metal strip on the top surface of the DRA in FlG.la. The rectangular DRA has the size of 12mm (length) x 12mm(width) x 4mm (height), and ' =37. A metal strip of 4mm x 4mm in size is placed towards the top-left corner on the top surface of the DRA. The microstrip feed line is printed on a substrate of Or =2.2 and thickness of 0.79mm, and has a width of 2.4mm. The rectangular DRA has a central frequency of 5.1GHz, and -lOdB bandwidth of 13%. In accordance with this invention, by introducing the metal strip on the top surface of the DRA, the bandwidth is increased by 5.2 times compared with the same DRA coupled by a slot. Two degenerated modes with good impedance matching can be observed from the response in FIG. 13.

FIG.14 shows an examples of the measured reflection coefficient, USA in dB against frequency, of a microstrip end-coupled rectangular DRA with a metal strip on the top surface of the DRA in FIG.3a. The rectangular DRA has the size of 12mm (length) x 12mm(width) x 4mm (height), and or =37. A metal strip of 7.5mm x 1.2mm in size is placed at an angle at the centre of the top surface of the DRA, as illustrated in FIG.3a. The microstrip line is printed on a substrate of Cr =2.2 and thickness of 0.79mm, and has a width of 2.4mm. The rectangular DRA has a central frequency of 5. 25GHz, and -lOdB bandwidth of 8.6%. In accordance with this invention, by introducing the metal strip on the top surface of the DRA, the bandwidth is increased by 3.5 times compared with the same DRA coupled by a slot. Two degenerated modes and an additional mode with good impedance matching can be observed from the response in FIG.14.

FTG.15 shows an example ofthe measured reflection coefficient, lSl in dB against frequency, of an on-surface-strip coupled rectangular DRA with a metal strip on the top surface of the DRA in FIG.Sa. The rectangular DRA has the size of 7mm (length) x 7mm(width) x 1.5mm (height), and Or =92. A metal strip of 3mm x lmm in size is placed at an angle at the bottomright corner of the top surface of the DRA as illustrated in FIG5.a. The on-surface-strip of width 1.8mm is connected to a microstrip dine of the same width printed on a substrate of Or = 10.5 and thickness of 1.6mm. The rectangular DRA has a central frequency of 6.97GHz, and --lOdB bandwidth of 3.6%. In accordance with this invention, by introducing the metal strip on the top surface of the DRA, the bandwidth is increased by 2.4 times compared with that without the strip or that coupled by a slot. Two degenerated modes with good impedance matching can be observed from the response in FIG. 15.

FIG. 16 shows an example of the measured reflection coefficient, lS l in dB against frequency, of a ground backed coplanar waveguide coupled rectangular DRA with a metal strip on the top surface of the DRA in FIG. 7a. The rectangular DRA has the size of 12mm (length) x 12mm(width) x 4mm (height), and Or =37. A metal strip of 8mm x 2.5mm in size is placed at an angle on the bottom-left corner of the top surface of the DRA as illustrated in FlG7.a. The central coplanar strip is printed on a substrate of Or =2.2 and thickness of 0.79mm, and has a width of 2.4mm. The rectangular DRA has a central frequency of 4.25GTlz, and -lOdB bandwidth of 8.4%. In accordance with this invention, by introducing the metal strip on the top surface of the DRA, the bandwidth is increased by 3.4 times compared with the same DRA coupled by a slot. Two degenerated modes with good impedance matching can be observed from the response in FIG. 16.

Claims

A miniaturised dielectric resonator antenna with increased impedance bandwidth comprising (a) a dielectric resonator made of a high permittivity material; (b) a metal strip placed on the top surface of the said dielectric resonator; and (c) feed means for transferring energy into or from the said dielectric resonator as an antenna.
2. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 1 wherein the dielectric resonator can be in rectangular, cylindrical or other geometries.
3. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 1 wherein the metal strip can be in different shapes, dimensions, and orientations.
4. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 1 wherein the metal strip can be placed at different positions on the top surface of the said dielectric resonator.
5. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim I wherein the metal strip has optimal shapes, sizes, positions and orientations determined by the dimensions and dielectric properties of the said dielectric resonator and by the feed means employed.
6. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 1 wherein the metal strip includes two or more equivalent metal strips.
7. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 1 wherein the feed means includes an open-ended microstrip line transferring energy to or from the said dielectric resonator.
8. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 7 wherein the said dielectric resonator is positioned towards the end of the said

microstrip line and along one side edge of the said microstrip line with a small area of overlapping.
9. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 7 wherein the said dielectric resonator is positioned at the end of and on the said microstrip line with an area of overlapping.
10. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 7 wherein the said microstrip line is printed on a dielectric substrate of low dielectric constant.
The miniaturised dielectric resonator antenna with increased impedance bandwidth of claims 7 wherein the single substrate microstrip structure includes multi-layered structures of multiple substrate and conductor layers.
]2. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim l wherein the feed means includes an onsurface-strip on one or more surfaces of the said dielectric resonator transferring energy to or from the said dielectric resonator.
13. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 12 wherein the said dielectric resonator is placed on top of a ground plane.
14. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim l wherein the feed means includes a ground backed coplanar waveguide transferring energy to or from the said dielectric resonator.
15. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 14 wherein the said dielectric resonator is placed towards the end of the coplanar strip and on top of the upper ground plane.
16. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claims 14 wherein the single substrate coplanar waveguide structure includes multi layered structures of multiple substrate and conductor layers.
17. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 1 wherein the feed means includes a slot on a large ground plane transferring energy to or from the said dielectric resonator.
18. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 17 wherein the said slot is further coupled by a microstrip line printed on a substrate, sharing the same ground plane.
19. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 17 wherein the said dielectric resonator is placed on and above the said slot.
20. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claims 18 wherein the single substrate microstrip structure includes multi-layered structures of multiple substrate and conductor layers.
21. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 1 wherein the feed means includes a probe on otherwise a ground plane transferring energy to or from the said dielectric resonator.
22. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 21 wherein the said dielectric resonator is placed on the said ground plane, and is in contact with the probe.
23. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 1 wherein the feed means includes a dielectric guide or wave guiding structure transferring energy to or from the said dielectric resonator.
24. The miniaturised dielectric resonator antenna with increased impedance bandwidth of claim 23 wherein the said dielectric resonator is placed on or along the said dielectric guide or wave guiding structure.