CA2201048C - Broadband nonhomogeneous multi-segmented dielectric resonator antenna system - Google Patents
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
- H01Q9/04—Resonant antennas
- H01Q9/0485—Dielectric resonator antennas
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Abstract
Abstract of the Disclosure A dielectric resonator antenna system is disclosed wherein a dielectric material having a high dielectric constant is placed between a dielectric resonator antenna (DRA) and the antenna feed. Preferably the dielectric material having a high dielectric constant is either in the form of an insert within a cavity of the DRA or alternatively is in the form of a thin layer between the feed and the DRA for enhancing coupling therebetween. It is preferred that the high dielectric constant material be at least twice the value of the dielectric resonator antenna.
Description
Doc. No 18-5 Patent Broadband Nonhomogeneous Multi-Segmented Dielectric Resonator Antenna System Field of the Invention S
This invention relates generally to dielectric resonator antennas and more particularly to an antenna having a high dielectric; material disposed between an antenna feed and a dielectric resonator.
Background of the Invention The rapid growth of information technology has been the main thrust for many advances in communication system developments such as satellite, wireless/mobile, and personal communications. Systems have been envisioned which will allow the communication from any time and place. In many of these systems the final point of contact is usually a wireless loop where antennas will play a crucial role. This puts a high demand on the antenna performance.
Ensuring efficient system operation requires an increased level of antenna integration into the system design right from the inception stage. The demand for high efficiency, compact size, low profile, and conformal construction is increasing. It is also very desirable for the antenna to be amenable to various arrangements of device integration as well as being capable of accommodating various operational requirements.
Presently, these requirements are likely achieved by arrays of antenna candidates, which currently are mostly limited to printed structures. The most popular candidate is a microstrip antenna due to fabrication simplicity, low profile, and ease of integration with many devices. It is widely used for applications requiring frequencies ranging from L-Band to millimeter-waves. However, conventional microstrip antennas are known to suffer from a number of disadvantages such as narrow bandwidth, low efficiencies, and higher loss at millimeter-wave frequencies. Recently, a relatively new approach to building microwave antennas based on the use of a dielectric resonator (DR) as the radiating element has been Doc. No 18-5 Patent proposed by S.A. Long, M. McAllister, and L.C. Shen, in a paper entitled 'The resonant cylindrical dielectric cavity antenna', IEEE Trans. Antennas Prvpagat., Vol.
AP-31, pp.
406-412,1983. Dielectric resonators (DRs) have been in use for a long time in microwave circuits mainly as energy storage devices. However, since DR boundaries are not conductors, there exists a 'loss' mechanism which forms the basis of their use as radiating elements. DRs have been found to overcome some disadvantages of microstrip antennas.
They also posses:> the attractive features of microstrip patches but offer superior performance, particularly, in terms of bandwidth and radiation efficiency.
Dielectric Resonator Antennas (DRAs) are antennas fabricated entirely from low loss dielectric materials and are typically mounted on ground planes. Their radiation characteristics are a function of the mode of operation excited in the DRA.
The mode is generally chosen based upon the operational requirement, however, the mode with the lowest Q is typically chosen. Various shapes of DRAB can also be used, including rectangular, disk, triangular, and cylindrical ring to obtain different radiation patterns suitable for a wide variety of applications. R.K. Mongia, A. Ittipiboon, Y.M.M. Antar, P.
Bhartia, and M. Cuhaci, describe such an application in a paper entitled 'A
half split cylindrical dielectric resonator antenna using slot coupling', IEEE Microwave and Guided Wave Letters, Vol. 3, pp. 38-39, 1993. In another paper by A. Ittipiboon, R.K.
Mongia, Y.M.M. Antar, P. Bhartia, and M. Cuhaci, entitled 'Aperture fed rectangular and triangular dielectric resonators for use as magnetic dipole antennas', Electron. Lett., Vol.
29, pp. 2001-2002, 1993 and yet another paper relating to DRAs is disclosed by A.
Ittipiboon, D. Roscoe, R. Mongia, ~u~d M. Cuhaci, and is entitled, 'A
circularly polarized dielectric guide antenna with a single slot feed', ibid., pp. 427-430.
Various feeding schemes can also be utilized to excite these modes. DRAB have been designed to produce either linear polarization with low cross-polarization levels or circular polarization with very good axial ratio performance over a broader bandwidth than obtainable from microstrip antennas. The reported performance of DRAB up to this point is impressive, ihowever, in accordance with this invention is still further improved.
This invention relates generally to dielectric resonator antennas and more particularly to an antenna having a high dielectric; material disposed between an antenna feed and a dielectric resonator.
Background of the Invention The rapid growth of information technology has been the main thrust for many advances in communication system developments such as satellite, wireless/mobile, and personal communications. Systems have been envisioned which will allow the communication from any time and place. In many of these systems the final point of contact is usually a wireless loop where antennas will play a crucial role. This puts a high demand on the antenna performance.
Ensuring efficient system operation requires an increased level of antenna integration into the system design right from the inception stage. The demand for high efficiency, compact size, low profile, and conformal construction is increasing. It is also very desirable for the antenna to be amenable to various arrangements of device integration as well as being capable of accommodating various operational requirements.
Presently, these requirements are likely achieved by arrays of antenna candidates, which currently are mostly limited to printed structures. The most popular candidate is a microstrip antenna due to fabrication simplicity, low profile, and ease of integration with many devices. It is widely used for applications requiring frequencies ranging from L-Band to millimeter-waves. However, conventional microstrip antennas are known to suffer from a number of disadvantages such as narrow bandwidth, low efficiencies, and higher loss at millimeter-wave frequencies. Recently, a relatively new approach to building microwave antennas based on the use of a dielectric resonator (DR) as the radiating element has been Doc. No 18-5 Patent proposed by S.A. Long, M. McAllister, and L.C. Shen, in a paper entitled 'The resonant cylindrical dielectric cavity antenna', IEEE Trans. Antennas Prvpagat., Vol.
AP-31, pp.
406-412,1983. Dielectric resonators (DRs) have been in use for a long time in microwave circuits mainly as energy storage devices. However, since DR boundaries are not conductors, there exists a 'loss' mechanism which forms the basis of their use as radiating elements. DRs have been found to overcome some disadvantages of microstrip antennas.
They also posses:> the attractive features of microstrip patches but offer superior performance, particularly, in terms of bandwidth and radiation efficiency.
Dielectric Resonator Antennas (DRAs) are antennas fabricated entirely from low loss dielectric materials and are typically mounted on ground planes. Their radiation characteristics are a function of the mode of operation excited in the DRA.
The mode is generally chosen based upon the operational requirement, however, the mode with the lowest Q is typically chosen. Various shapes of DRAB can also be used, including rectangular, disk, triangular, and cylindrical ring to obtain different radiation patterns suitable for a wide variety of applications. R.K. Mongia, A. Ittipiboon, Y.M.M. Antar, P.
Bhartia, and M. Cuhaci, describe such an application in a paper entitled 'A
half split cylindrical dielectric resonator antenna using slot coupling', IEEE Microwave and Guided Wave Letters, Vol. 3, pp. 38-39, 1993. In another paper by A. Ittipiboon, R.K.
Mongia, Y.M.M. Antar, P. Bhartia, and M. Cuhaci, entitled 'Aperture fed rectangular and triangular dielectric resonators for use as magnetic dipole antennas', Electron. Lett., Vol.
29, pp. 2001-2002, 1993 and yet another paper relating to DRAs is disclosed by A.
Ittipiboon, D. Roscoe, R. Mongia, ~u~d M. Cuhaci, and is entitled, 'A
circularly polarized dielectric guide antenna with a single slot feed', ibid., pp. 427-430.
Various feeding schemes can also be utilized to excite these modes. DRAB have been designed to produce either linear polarization with low cross-polarization levels or circular polarization with very good axial ratio performance over a broader bandwidth than obtainable from microstrip antennas. The reported performance of DRAB up to this point is impressive, ihowever, in accordance with this invention is still further improved.
Doc. No 18-5 Patent Another prior art dielectric resonator antenna is disclosed by A.A. Kishk, B.
Ahn, and D.
Kajfez in a paper "Broadband Stacked Dielectric Resonator Antennas," (IEE
Electronic Letters, Vol. 25, No. 18, Aug. 31, 1989); they have shown that the operational bandwidth of DRAs can be increased by stacking two dielectric resonators. In their configuration, a DRA of higher permittivity is stacked above a D RA of lower permittivity. The lower DRA was fed with a probe. The lower permittivity DR.A is designed to operate near but at a slightly different resonant frequency than the higher permittivity DR.A. The combination of the two thus resulted in a broader bandwidth. The stacked DRA
configuration resulted in a bandwidth of about 25%, while the bandwidth of the single DRA was about 10%. This increase in bandwidth, however, comes at the expense of increased size since the stacked DRAB are more than double the size of the single DRA.
It is an object of the invention to provide an antetma with improved coupling efficiency and bandwidth by utilizing a high dielectric material between the ground plane and the DRA.
It is yet a further object of the invention to provide a novel method for increasing the coupling efficiency using a thin high dielectric constant strip.
Statement of the Invention In accordance with the invention a dielectric resonator antenna system is provided comprising a grounded substrate; a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate; feed means for transferring energy into and from said dielectric resonator; and a thin dielectric substrate having a thickness of less than approximately x,/10 and, having a dielectric constant of approximately 2k or greater, the thin dielectric substrate being disposed between the feed means and the dielectric resonator fir enhancing coupling therebetween.
In accordance with the invention, a dielectric resonator antenna system is further provided comprising a plurality of resonator antenna elements each comprising:
a Doc. No 18-5 Patent grounded substrate,; a dielectric :resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate; feed means for transferring energy into and from said dielectric resonator; and, a thin dielectric substrate having a thickness of less than 7110 and, having a dielectric constant of approximately 2k or greater, the thin dielectric substrate being disposed between the feed means and the dielectric resonator for enhancing coupling therebetwec;n.
In accordance with yet another aspect of the invention there is provided a dielectric resonator antenna system comprising: a grounded substrate; a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
feed means for transferring energy into and from said dielectric resonator;
and, a dielectric material having a dielectric constant of approximately 2k or greater disposed between the feed means and the dielectric resonator for enhancing coupling therebetween, the dielectric material being substantially non-resonant at a resonance of the dielectric resonator antenna.
In yet another aspect of the invention there is provided, a dielectric resonator antenna system comprising an array of antenna elements, each element comprising: a grounded substrate; a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate; feed means for transferring energy into and from said dielectric resonator; and, a dielectric material having a dielectric constant of approximately 2k or greater disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
Brief Description of the Drawings Exemplary embodiments of the invention will now be described in conjunction with the drawings, in which:
Fig. 1 a is a top view of a notched dielectric resonator in accordance with the invention;
Fig. 1b is a side view of a notched dielectric resonator in accordance with the invention;
Fig. 2a is an illustration of notched dielectric resonator antenna with a high dielectric insert fed by a slot;
Ahn, and D.
Kajfez in a paper "Broadband Stacked Dielectric Resonator Antennas," (IEE
Electronic Letters, Vol. 25, No. 18, Aug. 31, 1989); they have shown that the operational bandwidth of DRAs can be increased by stacking two dielectric resonators. In their configuration, a DRA of higher permittivity is stacked above a D RA of lower permittivity. The lower DRA was fed with a probe. The lower permittivity DR.A is designed to operate near but at a slightly different resonant frequency than the higher permittivity DR.A. The combination of the two thus resulted in a broader bandwidth. The stacked DRA
configuration resulted in a bandwidth of about 25%, while the bandwidth of the single DRA was about 10%. This increase in bandwidth, however, comes at the expense of increased size since the stacked DRAB are more than double the size of the single DRA.
It is an object of the invention to provide an antetma with improved coupling efficiency and bandwidth by utilizing a high dielectric material between the ground plane and the DRA.
It is yet a further object of the invention to provide a novel method for increasing the coupling efficiency using a thin high dielectric constant strip.
Statement of the Invention In accordance with the invention a dielectric resonator antenna system is provided comprising a grounded substrate; a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate; feed means for transferring energy into and from said dielectric resonator; and a thin dielectric substrate having a thickness of less than approximately x,/10 and, having a dielectric constant of approximately 2k or greater, the thin dielectric substrate being disposed between the feed means and the dielectric resonator fir enhancing coupling therebetween.
In accordance with the invention, a dielectric resonator antenna system is further provided comprising a plurality of resonator antenna elements each comprising:
a Doc. No 18-5 Patent grounded substrate,; a dielectric :resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate; feed means for transferring energy into and from said dielectric resonator; and, a thin dielectric substrate having a thickness of less than 7110 and, having a dielectric constant of approximately 2k or greater, the thin dielectric substrate being disposed between the feed means and the dielectric resonator for enhancing coupling therebetwec;n.
In accordance with yet another aspect of the invention there is provided a dielectric resonator antenna system comprising: a grounded substrate; a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
feed means for transferring energy into and from said dielectric resonator;
and, a dielectric material having a dielectric constant of approximately 2k or greater disposed between the feed means and the dielectric resonator for enhancing coupling therebetween, the dielectric material being substantially non-resonant at a resonance of the dielectric resonator antenna.
In yet another aspect of the invention there is provided, a dielectric resonator antenna system comprising an array of antenna elements, each element comprising: a grounded substrate; a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate; feed means for transferring energy into and from said dielectric resonator; and, a dielectric material having a dielectric constant of approximately 2k or greater disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
Brief Description of the Drawings Exemplary embodiments of the invention will now be described in conjunction with the drawings, in which:
Fig. 1 a is a top view of a notched dielectric resonator in accordance with the invention;
Fig. 1b is a side view of a notched dielectric resonator in accordance with the invention;
Fig. 2a is an illustration of notched dielectric resonator antenna with a high dielectric insert fed by a slot;
Doc. No 18-5 Patent Fig. 2b is an illustration of a solid dielectric resonator antenna with high dielectric insert fed by a microstrip line;
Fig. 2c is an illustration of a dielecaric resonator antenna having a high dielectric constant insert within a notched portion of the resonator;
Fig. 2d is an illustration similar to that of Fig. 2c having inserted segments of different permittivities including a high dielectric constant;
Fig. 3 is a graph depicting return loss of 3 notched dielectric resonator antennas as a function of frequency;
Figs 4a and 4b shown measured radiation patterns for the notched DRA shown in Fig. la, with L1/L2=10/5;
Fig. 5 is a graph depicting measured return loss of DRA with high dielectric insert, fed by a SOS2 mierostrip line;
Fig. 6a is a diagram in top view depicting the geometry of an active phased array dielectric antenna in accordance with the invention;
Fig. 6b is diagram in side view of the active phase array antenna shown in Fig. 6b;
Fig. 7a is a top view of a column sub-array of multi-segment DRAB fed by a multi-layer microstrip network:;
Fig. 7b is a side view of the column sub-array of DRAs shown in Fig. 7a;
Fig. 8 is a graph depicting measured elevation pattern of a 320 element DRA
array;
Fig. 9 is a graph depicting measured azimuth pattern of the 320 element DRA
array; and, Fig. 10 is a graph of active gain versus normalized frequency for the 320 element DRA
array.
Detailed Description The basic concept for obtaining a wider operational impedance bandwidth of a dielectric resonator antenna is to lower its (~~-factor. The design approach is based on the studies reported by M. Velplanken and 1. Van Bladel, in a paper entitled 'The magnetic-dipole resonances of ring resonators of very high permittivity', in IEEE Trans.
Microwave Theory Tech., Vol. MTT-27, pp. 328-333, 1979. Verplanken and Bladel showed that increasing the ratio of the inner to outer radii can reduce the Q-factor of dielectric ring s Doc. No 18-5 Patent resonators, thus lowering the amount of stored energy. It is expected that by removing the centre portion of the DRA, its bandwidth can be increased.
Referring now to Figs. 1 a and 1 b, a slot-fed rectangular dielectric resonator antenna is shown with the centre portion removed, forming a rectangular notch 12. The antenna is fabricated from medium to high dielectric constant material disposed on a ground metalized substrate. The bottom layer of the substrate is a microstrip line feed layer 14. A
signal is coupled to the antenna through a narrow rectangular slot 16, perpendicular to the feed line, in the common ground plane 18 between the antenna and the microstrip line 14.
In operation, the antenna behaves like a short magnetic dipole aligned along the axis of the slot 16 with the maximum radiation in the boresight direction. In instances where the efficiency of coupling is low, the coupling efficiency can be improved by increasing the magnetic field intensity arvound the slot through the use of a thin strip 23 of high dielectric constant shown in Fig. 2a. In Fig. 2a a high dielectric constant insert 23 placed over the slot 16 in the central portion of a rectangular DRA 24 thereby being disposed between the feed means and the; dielectric resonator, is first coupled thus creating a strong magnetic field in its vicinity. This in turn strongly excites the required mode of the rectangular DRA 24. It is preferable that the high dielectric constant substrate 22 or insert 23 has a dielectric value of at least twice that of the DRA 24, and in a preferred embodiment, the value of the dielectric constant of the substrate 22 has shown in Fig. 2b), or insert 23, is 4 times that of the DRA 24. It is :further preferred that high dielectric 22 or 23 be substantially non-rf;sonant at a resc,~nance of the first dielectric resonator; it serves to concentrate the field in to upper dielectric resonator and to match the feed to the resonator. The dimension of the thin high dielectric constant strip 23 is experimentally optimized. The dielectric strip i;> much thinner than the DRA so that the major contribution to the radiation is from the DRA. Preferably the thickness of the dielectric substrate 22 is less than n,/10. The high dielectric strip can also be used to enhance the coupling to the DRA from a microstrip line 14 as well as a slot 16, as shown in Fig. 2b.
Fig. 2c shown an embodiment similar to that of Fig 2a, wherein a high dielectric insert material 23 fills the; entire notched portion or cavity defined within the DRA. Also, the Doc. No 18-5 Patent DRA need not have a notch, rectangular or otherwise, in order for the high dielectric constant insert to enhance the coupling. In Figs. 2b and 2d, the dielectric resonator antenna is shown having a mic.rostrip ground plane on the bottom face of a substrate having a microstrip feed line on top o:f the substrate. The high dielectric insert layer 23 is disposed between the microstrip ground plane and the solid DRA. The embodiment shown in Fig. 2d includes a plurality of layers 23a and 23b of different permittivities.
Experimental Results Several notched DRAB of different L1/L2 ratios were fabricated from RT/Duroid with dielectric constant of 10.8. At present, the theory to determine the resonant frequency for this DRA structure is not yet known. Thus, their dimensions were determined using the theory of a sc>lid rectangular DRA. From perturbation theory, it was expected that the resonant frequency of the notched DRA would be slightly higher than the solid rectangular DRA. This was confirmed by the measured results. It should be noted that the operating frequency in this study was arbitrarily chosen for the convenience of the measurement. In the following experiment, the slot dimensions and the matching stub length I~3 (shown in Fig. 1 b) were optimized so that one of the samples had a good match to the feed line. rClzis same slot was then used to feed the other samples so that the effects o:f Ll/Lz could be studied.
The measured return loss of notched DRAs having different ratios of L1/L2 is shown in Fig. 3. The results show the characteristic of a double tuned resonant circuit. The ratio L~/LZ can be used to control the location of the upper and the lower resonating frequencies, which increase with L~/ L2. When the two frequencies are located closer to each other, the antenna has a broad operating bandwidth. When the two frequencies are farther apart, the antenna can be utilized in a dual band mode of operation.
For the samples studied, it is found that the bandwidth of the notched DRA can be increased to 28% as compared to 10% for its solid counterpart. The measured radiation patterns of this antenna varied only slightly over this broad impedance bandwidth, (as shown in Fig. 4).
Hence, it is clear that the operating bandwidth of this notched dielectric antenna is 28%, Doc. No 18-5 Patent which is a significant improvement over its solid counterpart and the single microstrip patch element (a few per cent bandwidth). It should be noted that the cross-polarization level of this antenna is 20 dB lower than the peak co-polarization level over the same frequency band.
The DRAs above when redesignf:d for the operation at half of the original operating frequencies, were i:abricated from material with a dielectric constant of 10.
The feed line was constructed from the same substrate as in the previous cases. Using the above design it was found that it was not possible to achieve the efficient coupling without making the slot size too big. This is not a desirable solution due to increasing radiation loss from the slot.
In accordance with this invention, by introducing a material with a high dielectric constant, in the farm of an insert (Fig. 2a), the coupling efficiency was significantly increased without increasing the radiation loss from the slot. The achieved operational bandwidth was found to be 30%.
Tests were also carried out using the configuration shown in Fig. 2b, where a solid DRA
was placed on top of a microstrip Mine. Using a DRA of dielectric constant 10, there was only a limited amount of coupling; when the DRA was placed on a open-ended 50 microstrip line, achieving a maxirrmm of 5 dB return loss. When a thin dielectric insert (dielectric constant of 40) was added (Fig. 2b), the amount of coupling increased substantially, achieving a maximum return loss of 24 dB and a 10 dB return loss bandwidth of 16% as shown in Fig 5. Thus there is significant improvement in using a thin dielectric insert having a higT;h dielectric constant between the feed line and the dielectric resonator.
In another embodiment of the invention, a high gain, low profile active phased array antenna is provided with electronic beam steering capability in the azimuth plane. The radiating elements comprise the nrulti-segment dielectric resonator antennas described heretofore optionally and preferably, of rectangular cross-section, and fed by a microstrip Doc. No 18-5 Patent line. Providing the thin dielectric insert 22 having a high dielectric constant, between the feed line and the dielectric resonators enhances the operation of the DRAB.
The array combines DRA technology with mufti-layer printed technology and offers high gain, wide pattern bandwidths, and electronic beam steering capability.
Diagrams of the geometry of the array are shown in Figs. 6a and 6b. The array has a mufti-layer architecture having a radiating board 66, and feed distribution board 68. The radiating antenna includes 16 linear column arrays of mufti-segment DRA
elements 64.
Each linear column comprises two collinear sub-arrays formed of branched microstrip lines 63 feeding 10 DRA elements; the 10-element sub-array is shown in Figs 7a and 7b.
These branched lines are in turn fed by aperture coupling to the power distribution network, located on a second layer beneath the radiating board. The power distribution network includes a printed corporate feed, incorporating phase shifters for electronic beam steering in the azimuth plane. Low noise amplifiers (LNAs) are also integrated into each column to reduce the adverse effects of transmission line loss with respect to noise temperature.
Several prototype arrays have beers fabricated and tested. The first array to be fabricated was a passive antenna containing fi4 elements. The next iteration, which has recently been completed and tested, was an active antenna containing 320 DRAs and 16 integrated LNAs (15 dB gain stage). The measured patterns are shown in Figs. 8 and 9 while the boresight gain versus normalized frequency is shown in Fig. 10. A peak active gain (antenna gain including LNAs) of 39 dBi was measured with a 3 dB gain bandwidth of 15%. Good cross-polarization was also achieved, with levels on the order of 20 dB below the peak co-polarizf:d gain on boresight.
Of course, numerous other embod:irnents may be envisaged without departing from the spirit and scope of the invention.
Fig. 2c is an illustration of a dielecaric resonator antenna having a high dielectric constant insert within a notched portion of the resonator;
Fig. 2d is an illustration similar to that of Fig. 2c having inserted segments of different permittivities including a high dielectric constant;
Fig. 3 is a graph depicting return loss of 3 notched dielectric resonator antennas as a function of frequency;
Figs 4a and 4b shown measured radiation patterns for the notched DRA shown in Fig. la, with L1/L2=10/5;
Fig. 5 is a graph depicting measured return loss of DRA with high dielectric insert, fed by a SOS2 mierostrip line;
Fig. 6a is a diagram in top view depicting the geometry of an active phased array dielectric antenna in accordance with the invention;
Fig. 6b is diagram in side view of the active phase array antenna shown in Fig. 6b;
Fig. 7a is a top view of a column sub-array of multi-segment DRAB fed by a multi-layer microstrip network:;
Fig. 7b is a side view of the column sub-array of DRAs shown in Fig. 7a;
Fig. 8 is a graph depicting measured elevation pattern of a 320 element DRA
array;
Fig. 9 is a graph depicting measured azimuth pattern of the 320 element DRA
array; and, Fig. 10 is a graph of active gain versus normalized frequency for the 320 element DRA
array.
Detailed Description The basic concept for obtaining a wider operational impedance bandwidth of a dielectric resonator antenna is to lower its (~~-factor. The design approach is based on the studies reported by M. Velplanken and 1. Van Bladel, in a paper entitled 'The magnetic-dipole resonances of ring resonators of very high permittivity', in IEEE Trans.
Microwave Theory Tech., Vol. MTT-27, pp. 328-333, 1979. Verplanken and Bladel showed that increasing the ratio of the inner to outer radii can reduce the Q-factor of dielectric ring s Doc. No 18-5 Patent resonators, thus lowering the amount of stored energy. It is expected that by removing the centre portion of the DRA, its bandwidth can be increased.
Referring now to Figs. 1 a and 1 b, a slot-fed rectangular dielectric resonator antenna is shown with the centre portion removed, forming a rectangular notch 12. The antenna is fabricated from medium to high dielectric constant material disposed on a ground metalized substrate. The bottom layer of the substrate is a microstrip line feed layer 14. A
signal is coupled to the antenna through a narrow rectangular slot 16, perpendicular to the feed line, in the common ground plane 18 between the antenna and the microstrip line 14.
In operation, the antenna behaves like a short magnetic dipole aligned along the axis of the slot 16 with the maximum radiation in the boresight direction. In instances where the efficiency of coupling is low, the coupling efficiency can be improved by increasing the magnetic field intensity arvound the slot through the use of a thin strip 23 of high dielectric constant shown in Fig. 2a. In Fig. 2a a high dielectric constant insert 23 placed over the slot 16 in the central portion of a rectangular DRA 24 thereby being disposed between the feed means and the; dielectric resonator, is first coupled thus creating a strong magnetic field in its vicinity. This in turn strongly excites the required mode of the rectangular DRA 24. It is preferable that the high dielectric constant substrate 22 or insert 23 has a dielectric value of at least twice that of the DRA 24, and in a preferred embodiment, the value of the dielectric constant of the substrate 22 has shown in Fig. 2b), or insert 23, is 4 times that of the DRA 24. It is :further preferred that high dielectric 22 or 23 be substantially non-rf;sonant at a resc,~nance of the first dielectric resonator; it serves to concentrate the field in to upper dielectric resonator and to match the feed to the resonator. The dimension of the thin high dielectric constant strip 23 is experimentally optimized. The dielectric strip i;> much thinner than the DRA so that the major contribution to the radiation is from the DRA. Preferably the thickness of the dielectric substrate 22 is less than n,/10. The high dielectric strip can also be used to enhance the coupling to the DRA from a microstrip line 14 as well as a slot 16, as shown in Fig. 2b.
Fig. 2c shown an embodiment similar to that of Fig 2a, wherein a high dielectric insert material 23 fills the; entire notched portion or cavity defined within the DRA. Also, the Doc. No 18-5 Patent DRA need not have a notch, rectangular or otherwise, in order for the high dielectric constant insert to enhance the coupling. In Figs. 2b and 2d, the dielectric resonator antenna is shown having a mic.rostrip ground plane on the bottom face of a substrate having a microstrip feed line on top o:f the substrate. The high dielectric insert layer 23 is disposed between the microstrip ground plane and the solid DRA. The embodiment shown in Fig. 2d includes a plurality of layers 23a and 23b of different permittivities.
Experimental Results Several notched DRAB of different L1/L2 ratios were fabricated from RT/Duroid with dielectric constant of 10.8. At present, the theory to determine the resonant frequency for this DRA structure is not yet known. Thus, their dimensions were determined using the theory of a sc>lid rectangular DRA. From perturbation theory, it was expected that the resonant frequency of the notched DRA would be slightly higher than the solid rectangular DRA. This was confirmed by the measured results. It should be noted that the operating frequency in this study was arbitrarily chosen for the convenience of the measurement. In the following experiment, the slot dimensions and the matching stub length I~3 (shown in Fig. 1 b) were optimized so that one of the samples had a good match to the feed line. rClzis same slot was then used to feed the other samples so that the effects o:f Ll/Lz could be studied.
The measured return loss of notched DRAs having different ratios of L1/L2 is shown in Fig. 3. The results show the characteristic of a double tuned resonant circuit. The ratio L~/LZ can be used to control the location of the upper and the lower resonating frequencies, which increase with L~/ L2. When the two frequencies are located closer to each other, the antenna has a broad operating bandwidth. When the two frequencies are farther apart, the antenna can be utilized in a dual band mode of operation.
For the samples studied, it is found that the bandwidth of the notched DRA can be increased to 28% as compared to 10% for its solid counterpart. The measured radiation patterns of this antenna varied only slightly over this broad impedance bandwidth, (as shown in Fig. 4).
Hence, it is clear that the operating bandwidth of this notched dielectric antenna is 28%, Doc. No 18-5 Patent which is a significant improvement over its solid counterpart and the single microstrip patch element (a few per cent bandwidth). It should be noted that the cross-polarization level of this antenna is 20 dB lower than the peak co-polarization level over the same frequency band.
The DRAs above when redesignf:d for the operation at half of the original operating frequencies, were i:abricated from material with a dielectric constant of 10.
The feed line was constructed from the same substrate as in the previous cases. Using the above design it was found that it was not possible to achieve the efficient coupling without making the slot size too big. This is not a desirable solution due to increasing radiation loss from the slot.
In accordance with this invention, by introducing a material with a high dielectric constant, in the farm of an insert (Fig. 2a), the coupling efficiency was significantly increased without increasing the radiation loss from the slot. The achieved operational bandwidth was found to be 30%.
Tests were also carried out using the configuration shown in Fig. 2b, where a solid DRA
was placed on top of a microstrip Mine. Using a DRA of dielectric constant 10, there was only a limited amount of coupling; when the DRA was placed on a open-ended 50 microstrip line, achieving a maxirrmm of 5 dB return loss. When a thin dielectric insert (dielectric constant of 40) was added (Fig. 2b), the amount of coupling increased substantially, achieving a maximum return loss of 24 dB and a 10 dB return loss bandwidth of 16% as shown in Fig 5. Thus there is significant improvement in using a thin dielectric insert having a higT;h dielectric constant between the feed line and the dielectric resonator.
In another embodiment of the invention, a high gain, low profile active phased array antenna is provided with electronic beam steering capability in the azimuth plane. The radiating elements comprise the nrulti-segment dielectric resonator antennas described heretofore optionally and preferably, of rectangular cross-section, and fed by a microstrip Doc. No 18-5 Patent line. Providing the thin dielectric insert 22 having a high dielectric constant, between the feed line and the dielectric resonators enhances the operation of the DRAB.
The array combines DRA technology with mufti-layer printed technology and offers high gain, wide pattern bandwidths, and electronic beam steering capability.
Diagrams of the geometry of the array are shown in Figs. 6a and 6b. The array has a mufti-layer architecture having a radiating board 66, and feed distribution board 68. The radiating antenna includes 16 linear column arrays of mufti-segment DRA
elements 64.
Each linear column comprises two collinear sub-arrays formed of branched microstrip lines 63 feeding 10 DRA elements; the 10-element sub-array is shown in Figs 7a and 7b.
These branched lines are in turn fed by aperture coupling to the power distribution network, located on a second layer beneath the radiating board. The power distribution network includes a printed corporate feed, incorporating phase shifters for electronic beam steering in the azimuth plane. Low noise amplifiers (LNAs) are also integrated into each column to reduce the adverse effects of transmission line loss with respect to noise temperature.
Several prototype arrays have beers fabricated and tested. The first array to be fabricated was a passive antenna containing fi4 elements. The next iteration, which has recently been completed and tested, was an active antenna containing 320 DRAs and 16 integrated LNAs (15 dB gain stage). The measured patterns are shown in Figs. 8 and 9 while the boresight gain versus normalized frequency is shown in Fig. 10. A peak active gain (antenna gain including LNAs) of 39 dBi was measured with a 3 dB gain bandwidth of 15%. Good cross-polarization was also achieved, with levels on the order of 20 dB below the peak co-polarizf:d gain on boresight.
Of course, numerous other embod:irnents may be envisaged without departing from the spirit and scope of the invention.
Claims (13)
1. A dielectric resonator antenna system comprising:
a) grounded substrate;
h) a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
c) feed means for transferring energy into and from said dielectric resonator;
and, d) a thin dielectric substrate having a thickness of less than approximately .lambda./10 and, having a dielectric constant of approximately 2k or greater, the thin dielectric substrate being disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
a) grounded substrate;
h) a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
c) feed means for transferring energy into and from said dielectric resonator;
and, d) a thin dielectric substrate having a thickness of less than approximately .lambda./10 and, having a dielectric constant of approximately 2k or greater, the thin dielectric substrate being disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
2. A dielectric resonator antenna system as defined in claim 1, wherein the feed means comprises a microstrip line.
3. A dielectric resonator antenna system as defined in claim 1, wherein the dielectric resonator includes an opening in the form of a cavity.
4. The dielectric resonator antenna system as defined in claim 1, including a slot within the ground plane for accommodating said feed means.
5. The dielectric resonator antenna system as defined in claim 3, including a slot within the ground plane for accommodating the feed means.
6. The dielectric resonator antenna system as defined in claim 5, wherein the cavity is rectangular.
7. A dielectric resonator antenna system comprising a plurality of resonator antenna elements each comprising:
a) a grounded substrate;
b) a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
c) feed means for transferring energy into and from said dielectric resonator;
and, d) a thin dielectric substrate having a thickness of less than .lambda./10 and, having a dielectric constant of approximately 2k or greater the thin dielectric substrate being disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
a) a grounded substrate;
b) a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
c) feed means for transferring energy into and from said dielectric resonator;
and, d) a thin dielectric substrate having a thickness of less than .lambda./10 and, having a dielectric constant of approximately 2k or greater the thin dielectric substrate being disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
8. A radiating antenna system as defined in claim 7, wherein the plurality of resonator antenna elements have a common grounded substrate.
9. A radiating antenna system as defined in claim 1 wherein the thin dielectric substrate has a thickness of approximately .lambda./30 or less.
10. A radiating antenna system as defined in claim 1 wherein the dielectric constant of the thin dielectric substrate is approximately 3k or greater.
11. A dielectric resonator antenna system comprising:
a) a grounded substrate;
b) a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
c) feed means for transferring energy into and from said dielectric resonator;
and, d) a first dielectric material having a dielectric constant of approximately 2k or greater being substantially non-resonant at a resonance oh the dielectric resonator, said first dielectric material being disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
a) a grounded substrate;
b) a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
c) feed means for transferring energy into and from said dielectric resonator;
and, d) a first dielectric material having a dielectric constant of approximately 2k or greater being substantially non-resonant at a resonance oh the dielectric resonator, said first dielectric material being disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
12. A dielectric resonator antenna system as defined in claim 11 wherein the dielectric resonator includes an opening in the form of a resonant cavity.
l3. The dielectric resonator antenna system as defined in claim 11 including a slot within the ground plane for accommodating said iced means.
14. The dielectric resonator antenna system as defined in claim 12, including a slot within the ground plane for accommodating the feed means.
15. The dielectric resonator antenna system as defined in claim 14, wherein the cavity is rectangular.
16. The dielectric resonator antenna system as defined in claim 12, wherein the dielectric material having a dielectric constant of approximately 2k or greater is in the form of an insert disposed within the resonant cavity.
17. The dielectric resonator antenna system as defined in claim 16 wherein the insert is a rectangular block of material.
18. A radiating antenna system as defined in claim 8, wherein the feed means comprises a microstrip line.
19. A dielectric resonator antenna system comprising an array of antenna elements, each element comprising:
a) a grounded substrate;
b) a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
c) feed means for transferring energy into and from said dielectric resonator;
and, d) a dielectric material having a dielectric constant of approximately 2k or greater being substantially non-resonant at a resonance of the dielectric resonator, said dielectric material being disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
20. A dielectric resonator antenna system as defined in claim 8, wherein the grounded substrate is common to a plurality of the elements and including a slot within the grounded substrate.
21. A dielectric resonator antenna system as defined in claim 8, wherein the feed means comprises a microstrip branched feed line for feeding a plurality of the dielectric resonators 22. A radiating antenna system as defined in claim 7, wherein the thin dielectric substrate is substantially non-resonant at a resonance of the dielectric resonator.
l3. The dielectric resonator antenna system as defined in claim 11 including a slot within the ground plane for accommodating said iced means.
14. The dielectric resonator antenna system as defined in claim 12, including a slot within the ground plane for accommodating the feed means.
15. The dielectric resonator antenna system as defined in claim 14, wherein the cavity is rectangular.
16. The dielectric resonator antenna system as defined in claim 12, wherein the dielectric material having a dielectric constant of approximately 2k or greater is in the form of an insert disposed within the resonant cavity.
17. The dielectric resonator antenna system as defined in claim 16 wherein the insert is a rectangular block of material.
18. A radiating antenna system as defined in claim 8, wherein the feed means comprises a microstrip line.
19. A dielectric resonator antenna system comprising an array of antenna elements, each element comprising:
a) a grounded substrate;
b) a dielectric resonator having a dielectric constant k disposed a predetermined distance from the grounded substrate;
c) feed means for transferring energy into and from said dielectric resonator;
and, d) a dielectric material having a dielectric constant of approximately 2k or greater being substantially non-resonant at a resonance of the dielectric resonator, said dielectric material being disposed between the feed means and the dielectric resonator for enhancing coupling therebetween.
20. A dielectric resonator antenna system as defined in claim 8, wherein the grounded substrate is common to a plurality of the elements and including a slot within the grounded substrate.
21. A dielectric resonator antenna system as defined in claim 8, wherein the feed means comprises a microstrip branched feed line for feeding a plurality of the dielectric resonators 22. A radiating antenna system as defined in claim 7, wherein the thin dielectric substrate is substantially non-resonant at a resonance of the dielectric resonator.
13
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2201048 CA2201048C (en) | 1997-03-26 | 1997-03-26 | Broadband nonhomogeneous multi-segmented dielectric resonator antenna system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2201048 CA2201048C (en) | 1997-03-26 | 1997-03-26 | Broadband nonhomogeneous multi-segmented dielectric resonator antenna system |
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| Publication Number | Publication Date |
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| CA2201048A1 CA2201048A1 (en) | 1998-09-26 |
| CA2201048C true CA2201048C (en) | 2003-10-28 |
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| CA 2201048 Expired - Fee Related CA2201048C (en) | 1997-03-26 | 1997-03-26 | Broadband nonhomogeneous multi-segmented dielectric resonator antenna system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| GB0207052D0 (en) | 2002-03-26 | 2002-05-08 | Antenova Ltd | Novel dielectric resonator antenna resonance modes |
| CN104269650A (en) * | 2014-09-17 | 2015-01-07 | 电子科技大学 | High-gain rectangular dielectric resonator antenna working in high-order mode |
| CN104617395B (en) * | 2014-12-23 | 2018-05-15 | 北京邮电大学 | A kind of multiband dielectric resonance mobile phone terminal antenna |
| CN109616751A (en) * | 2019-01-14 | 2019-04-12 | 南通至晟微电子技术有限公司 | A kind of low section broadband medium resonant aerial |
| CN112928448B (en) * | 2021-01-20 | 2023-05-26 | 维沃移动通信有限公司 | Antenna structure and electronic equipment |
| CN113346245A (en) * | 2021-05-18 | 2021-09-03 | 深圳市信维通信股份有限公司 | Dielectric resonator antenna based on low dielectric constant medium and electronic equipment |
| CN113328236B (en) * | 2021-05-24 | 2022-07-29 | 电子科技大学 | Card-inserted end-fire broadband dielectric resonator antenna |
| CN114094301B (en) * | 2021-10-28 | 2023-03-24 | 西安理工大学 | Preparation method of magnetic-dielectric composite material dielectric resonator and miniaturized antenna |
| CN114824809B (en) * | 2022-04-02 | 2023-07-18 | 中山大学 | Dielectric resonator antenna with flat-top directional pattern characteristic |
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1997
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