EP0174068B1 - Improvements in or relating to microstrip antennas - Google Patents
Improvements in or relating to microstrip antennas Download PDFInfo
- Publication number
- EP0174068B1 EP0174068B1 EP19850304623 EP85304623A EP0174068B1 EP 0174068 B1 EP0174068 B1 EP 0174068B1 EP 19850304623 EP19850304623 EP 19850304623 EP 85304623 A EP85304623 A EP 85304623A EP 0174068 B1 EP0174068 B1 EP 0174068B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- antenna
- disc
- reflector
- radiator
- circular
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
- H01Q13/10—Resonant slot antennas
- H01Q13/18—Resonant slot antennas the slot being backed by, or formed in boundary wall of, a resonant cavity ; Open cavity antennas
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
- H01Q19/005—Patch antenna using one or more coplanar parasitic elements
-
- 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
- H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
- H01Q9/0464—Annular ring patch
Definitions
- This invention relates to microstrip antennas comprising a dielectric substrate having a conducting ground-plane on one face and a conducting sheet radiator on its other face coupled to a feeding arrangement.
- the invention has a principal application to such antennas where the radiator is a circular patch or disc approximately half a wavelength in diameter at its resonant frequency, enabling the bandwidth thereof to be substantially increased.
- F/D focal-length/diameter
- a further advantage in such applications is the low axial ratio obtained, ie the maximum variation in signal amplitude over 360° polar co-ordinates, which is important where circular polarisation is used.
- the invention provides a microstrip antenna as defined in the preamble of claim 1 and known from IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. AP-29, no. 1, January 1981, pages 3-24, New York, US; K. R. CARVER et al. "Microstrip Antenna Technology", Figure 9 and page 10, column 2, lines 29 to 41, characterised by the features of the characterising portion of Claim 1.
- the invention also provides a reflector antenna comprising a circular reflector, preferably of parabolic form, having the microstrip antenna as claimed in claim 1 located substantially at its focus to provide a feed.
- Figs 1 and 2 show an antenna comprising a circular disc 1 of metallisation located centrally on a disc 2 of dielectric material backed by a conducting ground-plane 3. Separated by a uniform gap 5 from disc 1 is an annular ring 6 of metallisation whose outer edge extends round the edge of disc 2 to join the ground-plane.
- the disc 1 is connected to a coaxial feeder whose inner conductor 7 extends through disc 2, and whose outer conductor 8 is connected to the ground-plane 3. It is not essential for the outer edge of ring 6 to make continuous contact with the ground-plane 3 as shown, eg a ring of spaced pins extending through the dielectric material can be used, as will be apparent to those familiar with microstrip antennas.
- the diameter of the disc 1 is approximately ⁇ m/2 at the operating frequency (where Am is the wavelength in the microstrip structure thus formed) so that the disc functions as a resonant radiator in a known manner, and the position of connection of conductor 7 to disc 1 is adjusted to match the antenna and feeder impedances at this frequency, as likewise known.
- the width of ring 6 is made approximately ⁇ m/4, this width and the width of gap 5 being adjusted experimentally to give the structure optimum bandwidth.
- Figs 3-6 show results obtained with an antenna having the following dimensions etc:
- Fig 3 shows the return loss of the antenna in the absence of ring 6, ie ring 1 alone, and Fig 4 shows the effect of adding the ring.
- the substantial increase in bandwidth (at -10 dB) in the latter case is clearly seen.
- Fig 5 shows the co-polar radiation pattern in both the E- and H-planes about boresight (0°).
- the antenna is seen to have equal beam-widths in both planes at very wide angles from boresight (eg ⁇ 60°).
- the low levels of cross-polarisation obtained ( ⁇ -20dB) are also shown.
- the width of the gap 5 is not critical and the optimum width is readily found by experiment. In the above example it was found that the stated width could be considerably increased without serious deterioration in performance, but could not be much reduced.
- the foregoing dimensions were unchanged except that the ring 6 width was 9 mm and the gap 5 width 2.25 mm.
- the centre frequency was 5.21 GHz.
- the coaxial feeder 7,8 was offset 0.33 of disc 1 diameter from its centre to obtain a 50 ohm match at resonance as opposed to 0.2 of disc diameter for the disc in isolation, ie without the ring 6.
- Measurements of the antenna amplitude and phase patterns were made in the principal (E- and H-) and diagonal (45°) planes at band-edge and centre frequencies, using improved measuring techniques.
- the antenna was not mounted on a large ground-plane conventionally used for microstrip patch antenna measurements.
- 8 is again the conventional polar co-ordinate.
- the minimum variation in phase occurred for a phase centre located on-axis 4 mm from the centre of disc 1.
- the maximum phase error at this position was ⁇ 15°, with most of the error occurring at the edge of the reflector arc.
- Table 1 also compares the cross-polarisation level of the present antenna with that of an isolated disc 1 operating at the same frequency and on a ground-plane equal to the ring 6 outer diameter.
- the radiation patterns for the isolated disc showed good circular symmetry for small ground-plane sizes, but with H-plane cross-polarisation >-20 dB for angles >25° from boresight (0°) which arises from diffraction from the edges of the ground-plane and overmoding in the disc.
- Table 1 indicates that the addition of ring 6 exerts considerable control of the sources of cross-polarisation, giving reduced levels within the arc subtended by the reflector.
- Table 2 shows the results of bandwidth and approximate gain fall-off for different values of gap 5 width.
- the gap 5 widths were achieved by changing the disc 1 diameter which resulted in a 10% variation in frequency, but the latter was not considered to affect significantly the bandwidth and gain results.
- the accuracy of gain measurement was approximately ⁇ 0.5 dB.
- Bandwidths up to and greater than 10% were obtainable, but with some reduction in input return loss (not shown in Table 2) and a significant fall-off in gain at the upper band-edge frequency.
- the input return loss could not be greatly improved by repositioning the coaxial feeder.
- the increase in bandwidth is due to an additional resonance mode close to the fundamental mode, and it is considered that losses in this mode account for the reduction in gain at the higher frequency.
- the A m/4 ring can also be applied to circularly polarised circular resonant radiators, eg energised with a 90° phase difference at points on two orthogonal radii, where, as stated, the low axial ratio obtained is particularly valuable.
- the invention may also be applicable to other than circular half-wave resonant sheet radiators, eg to those of elliptical shape.
Landscapes
- Waveguide Aerials (AREA)
Description
- This invention relates to microstrip antennas comprising a dielectric substrate having a conducting ground-plane on one face and a conducting sheet radiator on its other face coupled to a feeding arrangement.
- The invention has a principal application to such antennas where the radiator is a circular patch or disc approximately half a wavelength in diameter at its resonant frequency, enabling the bandwidth thereof to be substantially increased. The antenna thus formed is particularly suitable for feeding circular reflectors having small focal-length/diameter (F/D) ratios, eg F/D = 0.3, and which require a low-cost, lightweight, low-profile, simple feed structure, instead of using eg horn feeds. A further advantage in such applications is the low axial ratio obtained, ie the maximum variation in signal amplitude over 360° polar co-ordinates, which is important where circular polarisation is used.
- The invention provides a microstrip antenna as defined in the preamble of claim 1 and known from IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, vol. AP-29, no. 1, January 1981, pages 3-24, New York, US; K. R. CARVER et al. "Microstrip Antenna Technology", Figure 9 and
page 10,column 2, lines 29 to 41, characterised by the features of the characterising portion of Claim 1. - The invention also provides a reflector antenna comprising a circular reflector, preferably of parabolic form, having the microstrip antenna as claimed in claim 1 located substantially at its focus to provide a feed.
- To enable the nature of the present invention to be more readily understood, attention is directed, by way of example, to the accompanying drawings, wherein:
- Fig 1 is a sectional elevation of an antenna embodying the present invention.
- Fig 2 is plan view of the antenna of Fig. 1.
- Fig 3 is a graph showing the return loss of a simple circular microstrip antenna.
- Fig 4 is a graph showing the effect of modifying the antenna of Fig 3 in accordance with the present invention.
- Fig 5 is a graph showing the co-polar and cross-polar radiation patterns of the embodiment of Fig 4 in the E- and H- planes.
- Fig 6 is a graph showing the co-polar and cross-polar radiation patterns of a further example of the embodiment of Figs 1 and 2 in the E- and H- planes.
- Fig 7 is a graph showing patterns as in Fig 6 but for the two diagonal (45°) planes.
- Figs 1 and 2 show an antenna comprising a circular disc 1 of metallisation located centrally on a
disc 2 of dielectric material backed by a conducting ground-plane 3. Separated by auniform gap 5 from disc 1 is anannular ring 6 of metallisation whose outer edge extends round the edge ofdisc 2 to join the ground-plane. The disc 1 is connected to a coaxial feeder whoseinner conductor 7 extends throughdisc 2, and whoseouter conductor 8 is connected to the ground-plane 3. It is not essential for the outer edge ofring 6 to make continuous contact with the ground-plane 3 as shown, eg a ring of spaced pins extending through the dielectric material can be used, as will be apparent to those familiar with microstrip antennas. - The diameter of the disc 1 is approximately λm/2 at the operating frequency (where Am is the wavelength in the microstrip structure thus formed) so that the disc functions as a resonant radiator in a known manner, and the position of connection of
conductor 7 to disc 1 is adjusted to match the antenna and feeder impedances at this frequency, as likewise known. The width ofring 6 is made approximately λm/4, this width and the width ofgap 5 being adjusted experimentally to give the structure optimum bandwidth. - Figs 3-6 show results obtained with an antenna having the following dimensions etc:
- Disc 1 diameter 19.5 mm
-
Ring 6 width 10.0 mm -
Gap 5 width 2.75 mm -
Disc 2 thickness 3.18 mm -
Disc 2 relative permittivity 2.52 -
Feeder - Operating frequency - 5 GHz
- Fig 3 shows the return loss of the antenna in the absence of
ring 6, ie ring 1 alone, and Fig 4 shows the effect of adding the ring. The substantial increase in bandwidth (at -10 dB) in the latter case is clearly seen. - Fig 5 shows the co-polar radiation pattern in both the E- and H-planes about boresight (0°). The antenna is seen to have equal beam-widths in both planes at very wide angles from boresight (eg ± 60°). The low levels of cross-polarisation obtained (<-20dB) are also shown.
- The width of the
gap 5 is not critical and the optimum width is readily found by experiment. In the above example it was found that the stated width could be considerably increased without serious deterioration in performance, but could not be much reduced. - In a further example of the invention, the foregoing dimensions were unchanged except that the
ring 6 width was 9 mm and thegap 5 width 2.25 mm. The centre frequency was 5.21 GHz. Thecoaxial feeder ring 6. Measurements of the antenna amplitude and phase patterns were made in the principal (E- and H-) and diagonal (45°) planes at band-edge and centre frequencies, using improved measuring techniques. As in the earlier-described measurements, the antenna was not mounted on a large ground-plane conventionally used for microstrip patch antenna measurements. - Figs 6 and 7 show the measured amplitude patterns at band centre, in the principal and diagonal planes respectively, for an antenna suitable for feeding a prime focus fed reflector (ie having its feed located on-axis at its focal point) with F/D = 0.3. This corresponds to a beamwidth at the standard -10 dB level of 160°. 8 is again the conventional polar co-ordinate. The patterns show good circular symmetry and cross-polarisation generally below -25 dB within the arc subtended by the reflector, although a maximum cross-polarisation of -22 dB occurs at the edge of the reflector arc. Good circular symmetry is also observed for patterns obtained at the band-edge frequencies with cross-polarisation levels below -21 dB as shown in Table 1, which is a comparison of maximum cross-polarisation levels in both principal and diagonal planes within
arc 8 = ± 80°. - The minimum variation in phase occurred for a phase centre located on-
axis 4 mm from the centre of disc 1. The maximum phase error at this position was <15°, with most of the error occurring at the edge of the reflector arc. - Table 1 also compares the cross-polarisation level of the present antenna with that of an isolated disc 1 operating at the same frequency and on a ground-plane equal to the
ring 6 outer diameter. The radiation patterns for the isolated disc showed good circular symmetry for small ground-plane sizes, but with H-plane cross-polarisation >-20 dB for angles >25° from boresight (0°) which arises from diffraction from the edges of the ground-plane and overmoding in the disc. Table 1 indicates that the addition ofring 6 exerts considerable control of the sources of cross-polarisation, giving reduced levels within the arc subtended by the reflector. - Table 2 shows the results of bandwidth and approximate gain fall-off for different values of
gap 5 width. For convenience thegap 5 widths were achieved by changing the disc 1 diameter which resulted in a 10% variation in frequency, but the latter was not considered to affect significantly the bandwidth and gain results. The accuracy of gain measurement was approximately ±0.5 dB. Bandwidths up to and greater than 10% were obtainable, but with some reduction in input return loss (not shown in Table 2) and a significant fall-off in gain at the upper band-edge frequency. The input return loss could not be greatly improved by repositioning the coaxial feeder. The increase in bandwidth is due to an additional resonance mode close to the fundamental mode, and it is considered that losses in this mode account for the reduction in gain at the higher frequency. - These results obtained with the further example confirm the improved performance over that of an isolated disc and its particular suitability, as stated, for feeding reflectors, with small F/D, which require a low-cost, lightweight, low-profile simple feed structure.
- The A m/4 ring can also be applied to circularly polarised circular resonant radiators, eg energised with a 90° phase difference at points on two orthogonal radii, where, as stated, the low axial ratio obtained is particularly valuable. The invention may also be applicable to other than circular half-wave resonant sheet radiators, eg to those of elliptical shape.
Claims (3)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB848417502A GB8417502D0 (en) | 1984-07-09 | 1984-07-09 | Microstrip antennas |
GB8417502 | 1984-07-09 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0174068A1 EP0174068A1 (en) | 1986-03-12 |
EP0174068B1 true EP0174068B1 (en) | 1991-01-02 |
Family
ID=10563642
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19850304623 Expired EP0174068B1 (en) | 1984-07-09 | 1985-06-28 | Improvements in or relating to microstrip antennas |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0174068B1 (en) |
DE (1) | DE3581020D1 (en) |
GB (1) | GB8417502D0 (en) |
Families Citing this family (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA1263745A (en) * | 1985-12-03 | 1989-12-05 | Nippon Telegraph & Telephone Corporation | Shorted microstrip antenna |
JPS6365703A (en) * | 1986-09-05 | 1988-03-24 | Matsushita Electric Works Ltd | Planar antenna |
US4821040A (en) * | 1986-12-23 | 1989-04-11 | Ball Corporation | Circular microstrip vehicular rf antenna |
US4835541A (en) * | 1986-12-29 | 1989-05-30 | Ball Corporation | Near-isotropic low-profile microstrip radiator especially suited for use as a mobile vehicle antenna |
US6181277B1 (en) * | 1987-04-08 | 2001-01-30 | Raytheon Company | Microstrip antenna |
DE4002899A1 (en) * | 1990-02-01 | 1991-08-08 | Bosch Gmbh Robert | Roof incorporated vehicle aerial - has coaxial cable passing through base of cup-shaped element below ring shaped gap in roof |
GB2274548B (en) * | 1993-01-25 | 1996-07-24 | Securicor Datatrak Ltd | Dual purpose, low profile antenna |
DE10259833A1 (en) * | 2002-01-03 | 2003-07-24 | Harris Corp | Mutual coupling reduction method for phased array antenna system, involves providing circumferential conductor exclusively around each planar antenna element, and connecting conductor to ground reflector through ground posts |
GB2399949B (en) * | 2002-03-26 | 2004-11-24 | Ngk Spark Plug Co | Dielectric antenna |
US6801167B2 (en) | 2002-03-26 | 2004-10-05 | Ngk Spark Plug Co., Ltd. | Dielectric antenna |
CN104269616B (en) * | 2014-09-17 | 2017-10-17 | 电子科技大学 | The rectangular microstrip antenna of higher mode is worked in Mobile solution |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4291311A (en) * | 1977-09-28 | 1981-09-22 | The United States Of America As Represented By The Secretary Of The Navy | Dual ground plane microstrip antennas |
US4142190A (en) * | 1977-09-29 | 1979-02-27 | The United States Of America As Represented By The Secretary Of The Army | Microstrip feed with reduced aperture blockage |
US4460894A (en) * | 1982-08-11 | 1984-07-17 | Sensor Systems, Inc. | Laterally isolated microstrip antenna |
EP0117017A1 (en) * | 1983-01-20 | 1984-08-29 | Hazeltine Corporation | Low-profile omni-antenna |
-
1984
- 1984-07-09 GB GB848417502A patent/GB8417502D0/en active Pending
-
1985
- 1985-06-28 EP EP19850304623 patent/EP0174068B1/en not_active Expired
- 1985-06-28 DE DE8585304623T patent/DE3581020D1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
DE3581020D1 (en) | 1991-02-07 |
EP0174068A1 (en) | 1986-03-12 |
GB8417502D0 (en) | 1984-08-15 |
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