GB2219143A - Planar antenna - Google Patents

Description

2219143 1 - PLANAR ANTENNA %t This invention relates generally to planar

antennas andi more particularly, to a planar antenna which has first and second power supply circuits for realizing power supplies with respect to two different polarized waves of mutually different directivities, and is improved in the antenna characteristics.

The -planar antennas of the kind referred to are effectively utilized in receiving the polarized waves transmitted as carried on SHF band, in particular, a band of 12 GHz or more from a geostationary broadcasting satellite launched into cosmic space to be 36,000' Km high from the earth.

While parabolic antennas erected on the roof or the like positions of house buildings have been generally utilized as the antenna for receiving the electric waves from the geostationary satellite, the parabolic antennas have been defective in that they are susceptible to strong wind to easily fall down due to their bulky three dimensional structure so that additional means for stably supporting them will have to be employed, and that such supporting means further requires high mounting costs and still troublesome installation labor.

In attempt to eliminate these problems of the parabolic antennas, there has been suggested in Japanese t.

3 - Patent Application Laid-Open Publication No. 99803/1982 (corresponding to U.S. Patent No. 4,475,107 or German Patent Offenlegungsschrift No. 314900. 2) a planar antenna which is flattened in the entire configuration, according to which the structure can be much simplified and it is made possible to directly mount the antenna on an outdoor wall or the like position of the house buildings so as to be made inexpensive.

Further, the planar antenna has been demanded to be of a high gain, for which purpose various attempts have been made to reduce- insertion loss. Disclosed in, for example, U.S. Patent Application Serial No. 15,009 of K. Tsukamoto et al (to which U.K. Patent Application No. 87 03640, German Patent Application P 37 06 051.1 or Frenc,h Patent Application No. 87 02421 corresponds) prior to the present invention is a planar antenna, in which power supply circuit and radiation circuit are not connected directly to each other but are electromagnetically coupled for supplying a power from the power supply circuit to the radiation circuit, while both circuits as well as an earthing conductor are respectively carried on each of insulating plates which are separated from one another by means of a space retaining means. With this arrangement, therefore, the power supply circuit can be also disposed in the space thus retained so as to minimize the loss to improve the assembling ability, and the insertion loss can be effectively lowered.

Further prior to the present invention, there has been 4 suggested in U.S. Patent Application Serial No. 88,265 of T. Abiko et al (to which U.K. Patent Application No. 87 19750, German Patent Application P 37 29 750, or French Patent Application No. 87 12274 corresponds) another planar antenna in which a radiation circuit is provided with many slots in respective which each of patch elements is disposed, and such radiation circuit is electromagnetically coupled at the Datch elements in the slots to opposed power supply terminals of a power supply circuit, so as to further decrease the loss while incrementally improving the assembling ability.

According to the foregoing two prior art, it is possible to reduce the insertion loss and to improve the assembling ability for rendering the antenna to b'e highly mass-produce able, but it is still demanded that a higher gain can be obtained. Further, while satellitic broadcasting has steadily come up to a stage of practical use, there is a limit in allowable number by which the geostationary satellites can be launched, and it is required to employ signals of the same frequency but different in the mode of the polarized wave for elevating signal utilization efficiency more than ever. In this case, it is required to have the planar antenna provided with two different type power supply circuits, and B. Dietmer suggests in German Patent Offenlegungsschrift No. 35 14 880 an arrangement for improving the utilization efficiency with a provision of two power supply circuits with respect to a radiation circuit, but this arrangement 16 11 still has been unable to simultaneously and efficiently receive, in particular, linear polarized waves.

A primary aim of the present invention is, therefore, to provide a planar antenna which can sufficiently maintain high gain property of the antenna with its loss minimized, and can receive two different directional linear polarized waves simultaneously and at an extremely high efficiency.

According to the present invention, this aim can be 10 attained by a planar antenna in which respective plates of earthing conductor, first power supply circuit, first radiation circuit, second power supply circuit and second radiation circuit are sequentially arranged with a predetermined space interposed so as to be independent of one another, the first and second power supply circuit plates are provided with power supply conductor ends while the first and second radiation circuit plates are provided with radiation elements corresponding respectively to each of the power supply ends, and the power supply ends and radiation elements are mutually electromagnetically coupled for receiving polarized waves returned from a satellite with SHF band utilized, characterized in that the radiation elements in the first radiation circuit plate comprise respectively a pair of slender or flat-rectangular shaped slots, the radiation elements in the second radiation circuit plate comprise respectively an annular slot formed by disposing a rectangular patch 6 element within a square opening made in a conductor layer, the slots being disposed to be below the annular slots.

The invention will now be described, by way of example, with reference to the drawings, in which:- FIGURE 1 is a perspective view as disassembled into respective constituent plates with part of them removed in an embodiment of the planar antenna according to the present inventlon; FIG. 2 is a fragmentary perspective view as magnified of the planar antenna of FIG. 1; FIG. 3 is a fragmentary sectioned view as magnified of the planar antenna of FIG. 1; FIG. 4 is a fragmentary plan view of the antenna of FIG. 1 for explaining relationship between one of the p,-.)wer supply conductor ends in the first power supply circuit plate and a pair of the radiation elements in the first radiation circuit plate; FIG. 5 is a fragmentary plan view of the antenna of FIG. 1 for explaining relationship between one of the power supply conductor ends in the second power supply circuit plate and one of the radiation elements in the second radiation circuit plate; FIG. 6 is a fragmentary plan view of the antenna of FIG. 1 for showing relationship between the power supply conductor ends in the first and second power supply 1 circuit plates and the radiation elements in the first and second radiation circuit plates of the antenna of FIG. 1; FIG. 7 is a diagram showing the gain property in an aspect of the planar antenna of FIG. 1; and FIG. 8 is a diagram showing the gain property in another aspect of the planar antenna of FIG. 1.

While the present invention shall now be explained with reference to the embodiment shown in the accompanying drawings, it should be appreciated that the intention is not to limit the invention only to the embodiment shown, but rather to. include all alterations, modifications and equivalent arrangements possible within the scope of appended claims.

Referring now to FIGS. 1 to 3, a planar antenna 10 according to the present invention generally comprises an earthing conductor plate 11, first power supply circu-it plate 12, first radiation circuit plate 13, second power supply circuit plate 14 and second radiation circuit plate 15, and these plates 11-15 are sequentially stacked with a predetermined space interposed between them so as to be independent of one another. The earthing conductor plate 11 is formed by such a conductive member as aluminum, copper, silver, astatine, iron, gold or the like. The first and second power supply circuit plates 12 and 14 are respectively formed with a power supply network 16 or 17 made by the same conductive member as the earthing conductor plate 11, that is, aluminum, copper, silver, astatine, iron, gold or the like and attached onto a synthetic resin sheet of, for example, polyethylene, polypropylene, polyester, acrylics, polycarbonate, ABS resin and PVC resin alone or in a mixture of at least two of them. The first and second radiation circuits 13 and are also formed respectively by attaching a radiation network 18 or 19 of the same conductive material as the power supply networks 16 and 17 onto a synthetic resin sheet of, for example, the same material as in the above.

The power supply networks 16 and 17 of the f irst and second power -supply circuit plates 12 and 14 are respectively formed in a pattern including a large number of power supply conductor ends 16a or 17a, and these power supply conductor ends 16a of the power supply network 16 are all disposed to extend in a direction transversing at right angles a direction in which the power supply conductor ends 17a of the power supply network 17 extend, as seen in wave receiving direction, that is, in plan view of the antenna, so that both networks 16 and 17 can receive two different directional linear polarized waves.

On the other hand, the radiation networks 18 and 19 of the first and second radiation circuit plates 13 and 15 are respectively formed in a pattern including a large number of radiation elements 18a or 19a, in which each radiation element 18a in the radiation network 18 forming the first radiation circuit plate 13 is formed in a pair of slender or flat-rectangular shaped slots l8b, whereas each radiation element 19a in the radiation network 19 forming 9 the second radiation circuit plate 15 is provided as an annular slot 19b formed with a square opening 19c made in the conductive material on the resin sheet rectangular patch element 19d and a of the conductive material disposed within the opening 19c. The power supply conductor ends 16a in the first power supply circuit plate 12 and the radiation elements 18a of the first radiation circuit plate 13 are respectively disposed to be in alignment with one another in plan view as spaced and electromagnetically coupled to one another (see also FIG.

4), and a first antenna is thereby formed. At the same time, the power supply conductor ends 17a of the second power supply circuit plate 14 and the radiation elements 19a of the second radiation circuit plate 15 are aligned with each other as spaced and electromagnetically coupled (see also FIG. 5), and a second antenna is thereby provided. As will be clear when FIG. 6 is referred to in conjunction with FIGS. 1-5, the slots l8b are disposed in alignment with and to be below the annular slots 19b in plan view, so that the two antennas aligned with each other in the plan view will allow two different linear polarized waves mutually transversing at right angles (for example, horizontal and vertical linear polarized waves) to be smoothly received without any mutual interference.

In stacking the respective conductor and circuit plates 11-15, it is preferable to assemble them with a spacer made of a foamed synthetic resin interposed between the respective plates. For the first radiation circuit plate 13, for example, a metal plate having theradial slots made by a punching may be employed in place of the foregoing circuit plate of the radiation network of the conductive material attached onto the synthetic resin sheet and, when such metal plate is employed as the first radiation circuit plate 13, the particular plate 13 will act as an earthing conductor with respect to the second power supply circuit plate 14.

More practically, the radiation elements 18a of the first radiation circuit plate 13 are respectively formed with a pair of the slots 18b as one element, each of which bei ng 15 mm long and 3 mm wide and the pair being spaced by 15 mm, and the first radiation circuit plate 13 is made by arranging 256 of such radiation elements 18a in a matrix shape. Here, it has been found that the ctossed polarized wave characteristics can be improved by setting the length of the paired slots 18b forming the radiation element 18a to be substantially xg/2. Further, the radiation elements 19a of the second radiation circuit plate 15 are respectively formed with the square opening 19c of a side length of 15 mm and the patch element 19d. of a rectangular shape of 10 x 4 mm as one element, and the second radiation circuit plate 15 is made by arranging 256 of such radiation elements 19a in a matrix shape.

Further, the first and second power supply circuit plates 12 and 14 as well as the first and second radiation circuit plates 13 and 15 can be formed by means of an etching process to form a predetermined circuit pattern on is a printed substrate of, for example, a polyester film having a copper foil laminated on the film, and these circuit plates 12-15 are sequentially stacked on the for example, aluminum plate of 2 mm thick, with a foamed styrene sheet of 2 mm. thick interposed as the spacer between the respective plates.

In respect of theforegoing planar antenna according to the present invention, it has been found that, when the polarized waves are of a frequency of 11.7 to 12.5 GHz, there have been obtained a gain of 32.5 dBi with respect to the horizontal linear polarized waves received by the first antenna of the first power supply circuit plate 12 and first radiation circuit plate 13, a gain of 32 dBi with respect to the vertical linear polarized -waves received through the second antenna of the second power supply circuit plate 14 and second radiation circuit plate 15, and the crossed polarized wave characteristics of more than 30 dB for the both type polarized waves. Further, substantially the same level of the antenna characteristics as above could be obtained under the same the f oamed 11-15 was to be in respective to present or by a interposed earthing conductor plate 11 of frequency condition even when the spacer of styrene sheet between the respective plates replaced by such a mounting frame provided engagement only with peripheral edges of the plates 11-15 so as to allow only air space between substantial body parts of the plates honeycomb- shaped spacer of foamed styrene - 12 between the respective plates (see FIG radiation platE 1). The gain with respect to the horizontal linear polarized waves could be improved by 0.2 dB when each side length of the square opening 19c of the radiation element 19a in the second was varied to 18 mm. When the dimension of the rectangular patch element 19d was varied to be 10 x 0.2 mm, the crossed polarized wave characteristics were improved by 2 dB.

In the foregoing structure in practice, further, it is preferable that the first power supply network 16 is formed on the upper surface of the first power supply circuit plate 12, the first radiation network 18 is on the lower surface of the first radiation circuit plate 13, the second power supply network 17 is on the upper sirface of the second power supply circuit plate 14, and the -second radiation network 19 is on the lower surface of the second radiation circuit plate 15, so that the networks 16 and 18 in the f irst antenna and the networks 17 and 19 in the second antenna will directly oppose each other. With this structure, the gain of the f irst antenna, that is, at bottom part of the entire planar antenna, and the gain of the second antenna at top part will be as shown by curves Bl and T1 in FIG. 7, respectively, and they are generally satisfactory. When the gain at the second antenna is intended to be further improved, it has been found that a replacement of the first radiation circuit plate 13 of the printed substrate having the etched circuit pattern by the aluminum plate having many punched radial slots renders the bottom part gain B2 to approach the top part gain T2 as shown in FIG. 8, so as to be substantially at the same level.

Claims (6)

1. CLAIMS comprising a to each said 1. A planar antenna comprising an

   earthing conductor plate, a first power supply circuit plate disposed as spaced from said earthing conductor plate and carrying powe r supply conductor ends, a first radiation circuit plate disposed as spaced from said first power supply circuit plate and carrying radiation elements respectively 1Dair of slots and electromagnetically coupled power supply conductor end of said first power supply circuit plate, a second power supply circuit plate disposed as spaced from said first radiation circuit plate and carrying power supply conductor ends, and a second radiation circuit plate disposed as spaced from said second power supply circuit plate and carrying radiation elements respectively comprising an annulax slot formed by disposing a rectangular patch. element within a square opening made in a conductor layer, said radiation elements of said second radiation circuit plate being disposed above said radiation elements of said first radiation circuit plate and electromagnetically coupled to said power supply conductor ends of said second power supply circuit plate.

   Z
2. 2. A planar antenna according to claim 1 wherein said first radiation circuit plate is formed a metal plate.
3. 3. A planar antenna according to claim 1 wherein said first power supply circuit plate and said first radiation circuit plate are forming a first antenna while said second power supply circuit plate and said second radiation circuit plate are forming a second antenna, said first and second antennas being arranged respectively for receiving each of two different directional linear polarized waves mutually transversing at right angles.
4. 4. A planar antenna according to claim 1 wherein said slots forming said radiation elements of said first radiation circuit plate and said annular slots forming said radiation elements of said second radiation circuit plate are substantially aligned with each other in a direction in which polarized waves are received, and said slots are disposed below said annular slots.
5. 5. A planar antenna according to claim 1 wherein said slots of said radiation circuit plate are set to be of a length substantially of xg/2.

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6. 6. A planar antenna substantially as described herein with reference to the drawings.

   Published 1989 atThePatentofELc:e,StateHouse.65,171 High HolboMLondorLWClR4TP.PuithereopiesmaybeobtainedfromTheP&tentOlnee. Wes Branch, St Mary Cray Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1/87 Y 41