GB2244381A - Microstrip patch antenna - Google Patents
Microstrip patch antenna Download PDFInfo
- Publication number
- GB2244381A GB2244381A GB9011508A GB9011508A GB2244381A GB 2244381 A GB2244381 A GB 2244381A GB 9011508 A GB9011508 A GB 9011508A GB 9011508 A GB9011508 A GB 9011508A GB 2244381 A GB2244381 A GB 2244381A
- Authority
- GB
- United Kingdom
- Prior art keywords
- patch
- antenna
- elements
- array
- patch element
- 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.)
- Withdrawn
Links
Classifications
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/061—Two dimensional planar arrays
- H01Q21/065—Patch antenna array
Landscapes
- Waveguide Aerials (AREA)
- Aerials With Secondary Devices (AREA)
Abstract
A microstrip patch antenna comprises a substrate (1) supporting at least one patch element (2). A spatial variation is obtained in the radiation pattern of the patch element (2) by tapering the width (W1 to W2) of the element. This provides a further degree of freedom for adjusting and controlling the radiation pattern from a small array of patch elements (2). In one example, a 2 x 2 array of tapering element shapes is symmetrically arranged on the substance (1) as a feed for a prime aperture such as a lens or a reflector. The ends of the patch element(s) (2) may be laterally displaced to skew the radiation pattern. <IMAGE>
Description
DESCRIPTION
MICROSTRIP PATCH ANTENNA
This invention relates to microstrip patch antennae, particularly but not exclusively for use at millimetre wavelengths in microwave equipment. Such an antenna may comprise at least one patch element (or a small number of patch elements) designed to feed a prime aperture such as a reflector or a lens, or it may comprise a large array of patch elements which itself forms the antenna aperture.
Mi cros trip patch antennae comprise a substrate supporting at least one patch element. The paper entitled "Microstrip Array for
Reflector Feed Applications" by P.S. Hall and C.J. Prior (published on pages 631 to 636 of the Conference Proceedings of the 14th
European Microwave Conference, September 1984, Liege, Belgium) investigates the use of a small (2x2) array of such patch elements as a reflector feed, where significant system advantages may be obtained due to their compact nature and low cost, together with the possibility of direct integration with a low noise amplifier.
The whole contents of this Hall and Prior paper are hereby incorporated herein as reference material. Each patch element has a length which determines its resonant frequency and hence the antenna wavelength A (i.e. the length is approximately A/2) and a width which determines the impedance. Each patch element of the 2x2 array is of the same rectangular shape and size and is in a symmetrical arrangement on the substrate.
The construction of a 2x2 array as taught by Hall and Prior provides a narrower and better defined radiation pattern than can be obtained from simply using a single patch element. The 2x2 array has a radiation pattern that allows a reasonable ratio of focal length to aperture diameter to be used for a reflector or lens fed system. In order to provide an effective feed at the focus of a prime reflector or lens, it is necessary to control the radiation pattern from the array, and in particular to obtain a well-defined main lobe with reduced sidelobes. Radiation patterns from the Hall and Prior 2x2 arrays are shown in polar coordinates in said conference paper. The spacing of the patch elements in the two dimensions of the array provide the designer of the array with a degree of freedom which has a principal effect on the radiation pattern.Hall and Prior chose this spacing to give 720 10dB beamwidths in both H and E planes. A secondary effect on the radiation pattern is that of uncontrolled radiation from the feed line structure of the array, and Hall and Prior describe various design measures to limit this effect and so optimise the radiation pattern.
It is an aim of the present invention to provide the designer of a micros trip patch antenna with a further degree of freedom for adjusting and controlling the radiation pattern.
According to the present invention a micros trip patch antenna comprising a substrate supporting at least one patch element is characterised in that the patch element is of tapering shape having different widths adjacent to its opposite ends. By varying the width of the patch element, especially at its radiating end areas, a spatial variation can be obtained in the radiation pattern of the patch element itself.
Thus, the present invention is based on a recognition by the present inventors that each patch element itself has radiating apertures in the vicinity of its ends and that by varying their width the radiation impedance of these apertures can be made unequal so that different amounts of radiation will emanate from each end. Thus, a spatial variation in amplitude of the radiation profile emitted by each patch element can be obtained in the direction of length of the patch element.
This design feature may be adopted for a microstrip patch antenna having a single patch element of tapering shape, and it may also be adopted for an antenna comprising a large array of such patch elements. However, it is particularly advantageous for an antenna comprising a small number of patch elements because this permits the antenna designer to exploit more fully the interaction of the radiation profiles from the individual patch elements.
Thus, an antenna in accordance with the invention may be further characterised by comprising at least one pair of the patch elements connected with the same phase, and the tapering shape of one element may be arranged symmetrically on the substrate with respect to the tapering shape of the other element in the pair. This symmetrical arrangement of the tapering shape permits the realisation of a symmetrical radiation pattern from the pair of elements. At least when the patch antenna is designed to feed a prime aperture, each patch element in the pair would normally be designed to be of smallest width at its end remote from the other opposed element of the pair to reduce the radiating power at these remote ends so that the radiation amplitude is concentrated towards the middle of the pair.In order to achieve a more symmetrical polar diagram, the patch elements are preferably connected in an array of 2x2 elements, similar to the array described by Hall and
Prior but with a symmetrical arrangement in accordance with the present invention of the tapering shapes of the elements in the array.
The patch element or elements of tapering shape in accordance with the invention may have curved or other non-linear sides.
However, in order to avoid creating undesirable complex modes of resonance, each patch element may be of quadrilateral shape but having two non-parallel sides along its length.
Various forms and arrangements are known for feeding power to patch elements and may be used in micros trip patch antennae in accordance with the present invention. Good linear polarization of the radiation is obtained when a feed line is connected to one end of the patch element at substantially the middle of that one end.
Such a feed line may be formed in microstrip on the same substrate as the patch element and with the patch element as a coplanar area longitudinally extending from the feed line. The Hall and Prior paper describe an alternative feed on a second substrate with electromagnetic coupling to overlaid patch elements, and such a connection between the patch element(s) and a feed line may be adopted in an antenna in accordance with the present invention. A coaxial feed line which extends through the patch substrate to the patch element(s) may also be adopted.
The widths of the patch element adjacent to its opposite ends provide a main design variable in adjusting the radiation pattern from the element itself. Another dimensional variable results from the relative positioning of the ends of the tapered element. Thus, in an antenna in accordance with the present invention in which the patch element has a first end to which a feed line is connected and a second end remote from the first end, the middle of the first end may be displaced laterally with respect to the middle of the second end, in a direction perpendicular to the length of the patch element. In this situation the radiation pattern from the patch element is skewed in the direction perpendicular to the length.
This also provides some further control over the radiation pattern emitted by an array of such patch elements and may be used to concentrate the radiation amplitude towards the middle of the array.
These and other features in accordance with the invention are illustrated specifically in embodiments of the invention now to be described, by way of example, with reference to the accompanying diagrammatic drawing, in which:
Figure 1 is a silhouette plan view of a micros trip patch array suitable for feeding a microwave reflector or lens.
The micros trip array of Figure 1 comprises a dielectric substrate 1 supporting four conductive areas 2 forming patch elements arranged in a 2x2 array. The elements 2 are fed by striplines 3 in a manner which may be the same as those described in said Hall and Prior conference paper. The feed network of the striplines 3 is organised so that the signals transmitted to the patch elements 2 travel equal distances from an input line 4 to each patch element 2 so as to minimize phase differences between the different patch elements 2.
The substrate 1 may be of any suitable low loss dielectric material for microwave applications, for example PTFE as described by Hall and Prior, or a PTFE-fibreglass material available under the trade name RT/duroid, or quartz, or even for example a semi-insulating semiconductor-based material such as semi-insulating gallium arsenide. The back face of the dielectric substrate 1 is metallised to form a ground-plane (not shown in
Figure 1) whose size may be adjusted in the manner taught by Hall and Prior in order to reduce radiation distortion due to edge diffraction effects. The patch elements 2 (and possibly also the striplines 3 and 4) are formed by a metallisation pattern on the front face of the dielectric substrate 1. The back and front metallisations may be formed in known manner and may comprise, for example, plated copper or gold.However, the striplines 3 and 4 may be formed on a second dielectric substrate (which may be, for example, a GaAs microwave integrated circuit) overlaying the first substrate 1 so that the striplines 3 are connected to the patch elements 2 by an electromagnetic coupling in this case, as described in the Hall and Prior conference paper. As indicated schematically by the wider parts of the lines 3 and 4, the transmission lines 3 and 4 may be designed to include some impedance transformation to facilitate the impedance matching of the lines 3 and 4 to the patch elements 2.
This micros trip patch array 2 is designed to feed a prime focus of a microwave reflector or lens. It is therefore designed to emit a radiation pattern with a well-defined main lobe appropriate to the focal length of the reflector or lens. This is achieved by a symmetrical arrangement of the elements 2 on the substrate 1 and by appropriately choosing the spacings D1 and D2 of the elements 2 in the array, the widths W1 and W2 of opposite ends of each element 2, and the lateral displacement d (if any) of the middles of these opposite ends of each element 2. Thus, each element 2 is of tapering shape having different widths W1 and W2 adjacent to its opposite ends.In the specific form illustrated by way of example in Figure 1, each patch element 2 is of a simple quadrilateral shape having two non-parallel sides which extend along its length L between parallel opposite ends, and the widths
W1 and W2 occur at these opposite ends. Such a simple shape is known by the English expression "trapezium" and by the American expression "trapezoid". The feed-lines 3 are connected to one end of each patch element 2, the connection shown in the Figure 1 example being at the mid-point of this end.
The length L of each element 2 is approximately A/2, where A is the wavelength of the radiation emitted by the array and corresponds to the resonant frequency for the patch element 2. It should be noted that L is not chosen to be precisely \/2 because some reduction in length is necessary to compensate for capacitance effects at the ends of the element 2.
The electrical impedance of each patch element 2 and its radiating resistance is inversely proportional to the width of the element 2, which varies from W2 to W1 in accordance with the present invention. The average width is chosen to provide an appropriate impedance for matching with the feed-line network 3 and 4, whereas the width adjacent to each end is chosen in accordance with the desired amplitude of radiation to be emitted at these ends.
Thus, with the longitudinal feed of the element 2 by a feed-line at one end, the radiation does not emanate from a single area of the patch element 2 but from the areas at each of the opposite ends (of widths W1 and W2) of the element 2, and these areas appear in parallel at the feed point 3. By making these radiating areas of unequal widths W1 and W2, unequal amounts of radiation emanate from these areas. Thus, the amplitude of radiation emanating from the wider end W2 is higher than that from the narrower end W1. In this manner a spatial variation in amplitude of the radiation profile emitted by each element 2 is obtained. The upper elements 2 are connected with the same electrical phase as the lower elements 2 in the array drawing of
Figure 1, but they are arranged in the opposite geometric sense.
Thus, the smallest width W1 of the elements 2 of these opposite pairs is orientated at its end remote from the other opposed element, whereas the largest width W2 is adjacent the ends facing each other. In this situation the maximum amplitude of radiation emitted by the 2x2 array is concentrated around the middle of the array so that a taper in the radiation pattern from the array is obtained. This amplitude taper from the centre of the array to its edges can provide a more effective feed for illuminating a prime aperture reflector or lens, by reducing the side-lobe levels and by providing a degree of freedom over the illumination profile.
A further degree of adjustment of the tapering radiation profile from the array is possible by varying the position of the mid-point of one end of each patch element 2 with respect to its opposite end and the position of the feed from line 3 with respect to the mid-point(s) of one or both ends of the element 2. Thus, one end may be displaced laterally with respect to the other end by a distance d as shown in Figure 1 and the feed point from line 3 may be displaced laterally with respect to the mid-point of its end of the patch element 2 (not shown in Figure 1) and/or with respect to the opposite end as shown in Figure 1. The effect of the displacement d in the symmetrical arrangement of Figure 1 is to concentrate further the taper of the radiation profile towards the middle of the array by a lateral shift of the outer radiating areas of each patch element 2. However, large lateral displacements of this nature may produce complex modes of resonance in the patch elements 2 and so it is usually desirable to keep such lateral displacements small (especially of the feed line 3) in order to maintain linear polarization of the radiation emitted by the array. For the same reason it is usually desirable to keep the opposite ends of each element 2 parallel to each other, or at least approximately parallel. However, some departure from exactly parallel ends may be used to compensate for cross-polarized components which may occur otherwise in the radiation from some laterally-displaced tapering shapes.
Many other modifications and variations are possible within the scope of the present invention. Thus, although the tapering of the sides of each element 2 is shown as extending to the very ends of the elements in Figure 1, designs are also possible in which the width W2 and/or the width W1 is substantially constant over the length of an end portion of the total length L. Although Figure 1 illustrates rectilinear tapering sides of the patch elements 2, designs are also possible in which the angle of taper varies along the length L, and the tapering sides of the elements 2 may even be curved.
Figure 1 illustrates an embodiment of the invention in a 2x2 patch antenna array for feeding a prime reflector or lens.
However, the invention may also be employed in other contexts, for example in a 3x3 array or a 4x4 array of patch elements, either all of which or at least some of which are of tapering shape with different widths W1 and W2 at their opposite ends. The invention may also be incorporated in larger arrays of elements without any prime reflector or lens, although the effect of the different widths W1 and W2 may then become very subordinate to the power weighting of the different elements 2 in the large array. A tapering shape with different end widths W1 and W2 may also be used for small numbers of patch elements 2, for example a simple pair of opposed tapering elements 2 which may have their tapers symmetrically arranged on the substrate 1.An antenna may even be formed with a single patch element 2 shaped to have different widths W1 and W2 for its opposed radiating areas.
The theory of reciprocity applies to antennae, i.e. they give the same performance whether receiving or transmitting. Thus, although the embodiments have been described so far in terms of radiating antennae, patch elements in accordance with the invention may also be used in receiving antenna, for example at the focus of a reflector or lens which receives incident microwave signals.
In the embodiments so far described, the patch elements and microstrip antenna arrays have been unshielded. However, if desired, a slotted conducting shield (for example using so-called "triplate" technology with a further dielectric layer) may be included in order to reduce emission of unwanted radiation, for example radiation from the feedlines 3 and 4 and/or radiation components not linearly polarized with a desired orientation.
From reading the present disclosure, other variations will be apparent to persons skilled in the art. Such variations may involve other features which are already known in the design, manufacture and use of antennae and of micros trip and other microwave technology components and which may be used instead of or in addition to features already described herein. Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation thereof, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention. The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.
Claims (8)
1. A microstrip patch antenna comprising a substrate supporting at least one patch element, characterised in that the patch element is of tapering shape having different widths adjacent to its opposite ends.
2. An antenna as claimed in Claim 1, further characterized by comprising at least one pair of the patch elements connected with the same phase1 and in that the tapering shape of one element is arranged symmetrically on the substrate with respect to the tapering shape of the other element in the pair.
3. An antenna as claimed in Claim 2, further characterized in that each patch element in the pair is of smallest width at its end remote from the other opposed element of the pair.
4. An antenna as claimed in Claim 2 or Claim 3, further characterized in that the patch elements are connected in an array of 2 by 2 elements with a symmetrical arrangement of the tapering shapes of the elements in the array.
5. An antenna as claimed in anyone of the preceding claims, further characterized in that each patch element is of quadrilateral shape having two non-parallel sides along its length.
6. An antenna as claimed in any one of the preceding claims, further characterised in that a feed line is connected to one end of the patch area of the radiating element at substantially the middle of said one end.
7. An antenna as claimed in any one of the preceding claims, further characterised in that the patch element has a first end to which a feed line is connected and a second end remote from the first end, and in that the middle of the first end is displaced laterally with respect to the middle of the second end, in a direction perpendicular to the length of the patch element.
8. An antenna having any one of the novel features substantially as described with reference to and/or as illustrated in any one of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9011508A GB2244381A (en) | 1990-05-23 | 1990-05-23 | Microstrip patch antenna |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9011508A GB2244381A (en) | 1990-05-23 | 1990-05-23 | Microstrip patch antenna |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9011508D0 GB9011508D0 (en) | 1990-07-11 |
| GB2244381A true GB2244381A (en) | 1991-11-27 |
Family
ID=10676409
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9011508A Withdrawn GB2244381A (en) | 1990-05-23 | 1990-05-23 | Microstrip patch antenna |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2244381A (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0661773A1 (en) * | 1993-12-31 | 1995-07-05 | AEROSPATIALE Société Nationale Industrielle | Conically shaped microstrip patch antenna prepared on a planar substrate and method of its manufacturing |
| GB2316233A (en) * | 1990-12-14 | 1998-02-18 | Dassault Electronique | Wide band radiating device capable of several polarizations |
| US5999090A (en) * | 1997-02-04 | 1999-12-07 | Mitel Semiconductor Limited | Alarm sensor and antenna arrangement |
| EP1450437A1 (en) * | 2003-02-24 | 2004-08-25 | Ascom Systec AG | Ring-shaped embedded antenna |
| CN104009288A (en) * | 2014-05-14 | 2014-08-27 | 上海交通大学 | Millimeter-wave wide-beam and high-gain lens antenna |
| CN107706540A (en) * | 2017-08-30 | 2018-02-16 | 西安普腾电子科技有限公司 | A kind of rectangle high efficiency tightens radiation field of aerial and target scattering test system |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4012741A (en) * | 1975-10-07 | 1977-03-15 | Ball Corporation | Microstrip antenna structure |
| US4191959A (en) * | 1978-07-17 | 1980-03-04 | The United States Of America As Represented By The Secretary Of The Army | Microstrip antenna with circular polarization |
| EP0209156A2 (en) * | 1985-07-19 | 1987-01-21 | Kabushiki Kaisha Toshiba | Planar antenna with patch radiators |
| GB2211025A (en) * | 1987-10-15 | 1989-06-21 | Matsushita Electric Works Ltd | Planar antenna |
-
1990
- 1990-05-23 GB GB9011508A patent/GB2244381A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4012741A (en) * | 1975-10-07 | 1977-03-15 | Ball Corporation | Microstrip antenna structure |
| US4191959A (en) * | 1978-07-17 | 1980-03-04 | The United States Of America As Represented By The Secretary Of The Army | Microstrip antenna with circular polarization |
| EP0209156A2 (en) * | 1985-07-19 | 1987-01-21 | Kabushiki Kaisha Toshiba | Planar antenna with patch radiators |
| GB2211025A (en) * | 1987-10-15 | 1989-06-21 | Matsushita Electric Works Ltd | Planar antenna |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2316233A (en) * | 1990-12-14 | 1998-02-18 | Dassault Electronique | Wide band radiating device capable of several polarizations |
| GB2316233B (en) * | 1990-12-14 | 1998-07-01 | Dassault Electronique | Wide band radiating device capable of several polarizations |
| EP0661773A1 (en) * | 1993-12-31 | 1995-07-05 | AEROSPATIALE Société Nationale Industrielle | Conically shaped microstrip patch antenna prepared on a planar substrate and method of its manufacturing |
| FR2714769A1 (en) * | 1993-12-31 | 1995-07-07 | Aerospatiale | Conical microstrip antenna prepared on a flat substrate, and process for its preparation. |
| US5600331A (en) * | 1993-12-31 | 1997-02-04 | Aerospatiale Societe Nationale Industrielle | Conical microstrip antenna prepared on flat substrate and method for its preparation |
| US5999090A (en) * | 1997-02-04 | 1999-12-07 | Mitel Semiconductor Limited | Alarm sensor and antenna arrangement |
| EP1450437A1 (en) * | 2003-02-24 | 2004-08-25 | Ascom Systec AG | Ring-shaped embedded antenna |
| CN104009288A (en) * | 2014-05-14 | 2014-08-27 | 上海交通大学 | Millimeter-wave wide-beam and high-gain lens antenna |
| CN107706540A (en) * | 2017-08-30 | 2018-02-16 | 西安普腾电子科技有限公司 | A kind of rectangle high efficiency tightens radiation field of aerial and target scattering test system |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9011508D0 (en) | 1990-07-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |