GB2245429A

GB2245429A - Plane patch antenna

Info

Publication number: GB2245429A
Application number: GB9106379A
Authority: GB
Inventors: Tsuyoshi Mizuno; Motoki Hirano; Masanori Saito
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 1990-03-27
Filing date: 1991-03-26
Publication date: 1992-01-02
Also published as: JP2630007B2; JPH03276904A; GB9106379D0; DE4110156A1

Description

1 PLANE PATCH ANTENNA This invention relates to a plane patch antenna

having two conductive plates maintained in spaced-parallel relation to each other.

For example, Japanese Patent Kokai Nos. 59-200503 and 59-207705 disclose plane patch antennas having two metal disc plates maintained in spacedparallel relation to each other by means of a plurality of metal pins. With such prior art plane antenna, however, its usefulness is limited in land mobile radio telephone applications, particularly where it is used in the rain. This stems from the fact that the prior art plane patch antenna has an available frequency band width which is too narrow to absorb variations in its frequency characteristic which may occur in the rain.

Therefore, it would be desirable to be able to provide an improved plane patch antenna having an increased available frequency band width.

It would also be desirable to be able to provide a plane patch antenna which consumes less space.

The invention provides a plane patch antenna as set forth in claim 1. 1 In one aspect the invention provides a plane patch antenna comprising a rhombic conductive patch plate member, a conductive earth plate member, a plurality of short pins extending between the patch and earth plate members to maintain the patch and earth plate members in spaced-parallel relation to each other and to make electric connection between the patch and earth plate members, and a feeder shaft extending from the patch plate member for 2 electrical connection of the patch plate member to a lead wire. The feeder shaft has a tapered portion extending a length from the patch plate member toward the earth plate member. The tapered portion has a cross-sectional area decreasing as going away from the patch plate member.

In another aspect of the invention, there is provided a plane patch antenna comprising a hexagonal patch conductive plate member,, an earth conductive plate member, a plurality of short pins extending between the patch and earth plate members to maintain the patch and earth plate members in spaced-parallel relation to each other and to make electric connection between the patch and earth plate members, and a feeder shdft extending from the.patch plate member for electrical connection of the patch plate member to a lead wire. The feeder shaft has a tapered portion extending a length from the patch plate member toward the earth plate member. The tapered portion has a cross-sectional area decreasing as going away from the patch plate member.

In still another aspect of the invention, there is provided a plane patch antenna comprising an octagonal patch conductive plate member, an earth conductive plate member, a plurality of short pins extending between the patch and earth plate members to maintain the patch and earth plate members in spacedparallel relation to each other and to make electric connection between the patch and earth plate members, and a feeder shaft extending from the patch plate member for electrical connection of the patch plate member to a lead wire. The feeder shaft has a tapered portion extending a length from the patch plate member 0 3 toward the earth plate member. The tapered portion has a cross-sectional area decreasing as going away from the patch plate member.

This invention will be described in greater detail by reference to the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is a sectional view of a prior art plane patch antenna;

Fig. 2 is a graph plotting fraction band width (Af/fo) with respect to given distances (p) between the short pins and the feeder shaft; Fig. 3 is a graph used in explaining the h r> available frequency band width of the prior art plan.e patch antenna at a return loss of -11.7 dB;

Fig. 4 is a graph used in explaining the effect of precipitation on the antenna frequency characteristic; Fig. 5A is a plan view showing one embodiment of a plane patch antenna made in accordance with the invention; Fig. 5B is a sectional view of the plane patch antenna of Fig. 5A; Figs. 6 and 7 are graphs used in explaining the effect of the plane patch antenna of Figs. 5A and 5B:

Fig. 8A is a plan view of an antenna casing for receiving the plan patch antennas of Figs. 5A and 5B; Fig. 8B is an elevational view of the antenna casing of Fig. 8A; Fig. 8C is a plan view of an antenna casing for receiving the conventional plan patch antennas of Fig. 1; 4 Fig. 8D is an elevational view of the antenna casing of Fig. 8C; Figs. 9 and 10 are graphs used in explaining the effect of the plane patch antenna of the invention housed in the antenna easing; Fig. 11 is a plan view showing a modified form of the plane patch antenna of the invention; Figs. 12 through 15 are graphs used in explaining the effect of the plane patch antenna of Fig. 11; Fig. 16 is a plan view showing another modified form of the plane patch antenna of the invention; and Figs. 17 and 18 are graphs used in explaining the effect of the plane patch antenna of Ficr. 16.

C) Prior to the description of the preferred embodiment of the present invention, the prior art plane patch antenna of Fig. 1 is briefly described in order to specifically point out the difficulties attendant thereon.

The prior art plane patch antenna comprises a disc-shaped patch plate member A and a disc-shaped earth plate member B having a diameter greater than that of the patch plate member A. These plate members A and B are made of a conductive material and rigidly maintained coaxially in spacedparallel relation to each other by a plurality of short pins C secured thereto. The short pins C are conductive pins for providing an electrical connection between the plate members A and B. A feeder shaft D extends from the center 0 of the patch plate member A through a through-hole E formed centrally in the earth plate member B. The feeder shaft D is taken in the form of a coaxial cable having center threads covered by a braided sheath. The braided sheath is connected to the earth plate member B and the center threads are connected to a lead wire for connection to a transmitter/receiver unit associated with the plate patch antenna. In Fig. 19 the character p indicates the distance at which the short pins C are spaced from the feed shaft D and the character t indicates the distance between the patch and earth plates A and B. However, such a prior art patch antenna has an available frequency band width which is too narrow to absorb variances in its frequency characteristic resulting from antenna manufacturing and mounting tolerances and other factors including waterdrops deposited on the plane patch-antenna. For this reason, the prior art patch antenna cannot be used in the rain with its loest efficiency. In addition, the antenna manufacturing and mounting tolerances are of critical importance.

Fig. 2 is a graph plotting fractional band width (Af/fo) with respect to given distances (p) between the short pins C and the feeder shaft D for a return loss of -10 dB. As will be observed from Fig. 2, the fractional band width of the prior art patch antenna is 10% at the most even at a return loss of -10 dB. Where the patch antenna is used for a land mobile radiotelephone, however, the Japanese telegram and telephone standards (VSWRI.7) require a fractional band width of 8% to 10% at a return loss of -11.7 dB, as shown in Fig. 3. The term "fractional band width" means the ratio of the available frequency band width (Af) to the frequency (fo).

Fig. 4 is a graph plotting return loss with C.

6 respect to given frequencies for different amounts of waterdrops deposited on the patch antenna. The solid curve relates to no waterdrop deposited on the plane patch antenna. As can be seen from a study of Fig. 4, the available frequency band shifts to a greater extent toward the low frequency side as the amount of waterdrop deposited on the plane patch antenna increases.

Referring to Figs. 5A and 5B, there is shown a plane patch antenna embodying the invention. The plane patch antenna, generally designated by the numeral 10, includes patch and earth plate members 12 and 14 maintained rigidly in coaxial and spaced-parallel relation to each other by a plurality of (in the illustrated case four) short pins 16 extending in parallel with each other. Opposite short pins 16 are symmetric with respect to the center of the rhombic patch plate member 12. The patch and earth plate members 12 and 14 are made of a conductive material. Alternatively, each of the patch and earth plate members 12 and 14 may be taken in the form of a conductive metal film disposed on one of the opposite surfaces of a synthetic resin plate member. The patch plate member 12 has a rhombic shape and the earth plate member 14 has a rectangular shape, as best shown in Fig. 5A. The earth plate member 14 has a size greater than that of the patch plate member 12. The short pins 16 are conductive pins for providing an electrical connection between the plate members 12 and 14.

In Fig. SA, the character A indicates the length of the rhombic patch plate member 12; that is, the length of the longer diagonal line of the rhombic 7 patch plate member 12, the character B indicates the width of the rhombic patch plate member 12; that is, the length of the shorter diagonal line of the rhombic patch plate member 12, the character z indicates the maximum diameter of the feeder shaft 20, the character t indicates the antenna height; that is, the distance between the patch and earth plate members 12 and 14, the character E indicates the distance between the short pins 16 arranged on lines extending in the direction of the length of the rhombic patch plate member 12, the character F indicates the distance between the short pins 16 arranged on lines extending in the direction of the width of the rhombic patch plate member 12, the character S indicates the diameter of the short pins 16, and the character D indicates the distance between the opposite sides of the rhombic patch plate member 12; that is, the length of the perpendicular from one vertex to the opposite side.

A feeder shaft 20 extends from the center of the patch plate member 12 through a through-hole 18 centrally formed in the earth plate member 14 for connection to a lead wire. The feeder shaft 20 is insulated electrically from the earth plate member 14. The feeder shaft 20 has a tapered portion 22 extending from the the patch plate member 12 toward the earth plate member 14. The tapered portion 22 has a crosssectional area which has a maximum value at its bottom and a minimum value at its top. The tapered portion 22 may be of a cone shape, a hollow cone shape, a pyramid shape, or other shapes having a cross-sectional area decreasing in a stepped or stepless fashion - 9 o i n,,.1, away from the its base. The tapered portion 22 may be 2 made of copper, aluminium or other conductive materials. The tapered portion 22 may be formed by a conductive metal film disposed on the outer surface of a synthetic resin taper. The base of the tapered portion 22 is coaxially secured to the patch plate member 12. The apex of the tapered member 20 is connected to a shaf t member 24 which f orms a part of the feeder shaft 20. The shaft member 24 may taken in the form of a coaxial cable having center threads covered by a braided sheath. The braided sheath is connected to the earth plate member 14 and the center threads are connected to a transmitter/receiver unit associatedwith the plate patch antenna 10.

A test was conducted to show the effect of the plane patch antenna of the invention on the frequency band width. The tested plan patch antenna had dimensions listed in Table 1.

TABLE 1

UNIT mm A A1 A 224 0.767 0.673 B 112 0.384 0.336 z 55 0.188 0.165 t 15 0.0514 0.045 E 90 0.308 0.270 F 37.5 0.128 0.113 S 4 0.0137 0.012 D 100.18 0.343 0.301 In the first column of Table 1, A is the length of the rhombic patch plate member 12, B is the width of the rhombic patch plate member 12, z is the maximum diameter of the feeder shaft 20, t is the antenna 9 height, E is the distance between the short pins 16 arranged on lines extending in the direction of the length of the rhombic patch plate member 12, F is the distance between the short pins 16 arranged on lines extending in the direction of the width of the rhombic patch plate member 12, S is the diameter of the short pins 16, and D is the distance between the opposite sides of the rhombic patch plate member 12, as shown in Fig. 5A. These dimensions are expressed in millimeters in the second column of Table 1, in a unit of the resonance wave length (A) in the third column of Table 1, and in a unit of the minimum available wave length (Ai) in the fourth column of Table 1. The area of the patch plate member 12 was 12,544 MM2 (0. 14 7,k2, 0. 113A12) and the volume of the plane patch antenna 10 was 188,160 MM2 (0.00756A3, 0.005JOA13).

The test results are shown in Figs. 6 and 7. Fig. 6 is a graph showing frequency (MHz) versus return loss (dB) provided by the tested plane patch antenna. It is to be noted that the used resonance frequency (fo) is a value intermediate between the two values (indicated by Markers 2 and 3) at which the return loss is - 11. 7 dB rather than a value (indicated by Marker 1) at which the return loss is at minimum. Fig. 7 is a Smith chart which indicates an antenna impedance at each of frequencies. The Smith chart has a solid outer circle representing 5OC2 and a broken center circle representing -11.7 dB. Normally, mobile radio telephone systems employ a cable having an impedance of 50f) to connect the transmitter/receiver unit to the associated antenna. If the antenna is completely matched with the cable, the return loss will be minimum at the matched frequency so that the energy from the transmitter is emitted at the matched frequency from the antenna with maximum efficiency. In practice, however, the antenna serves as a f ilter and the energy is emitted in a predetermined range of frequencies rather than at the matched frequency. The closer to the circle representing 50Q an antenna frequency exists, the smaller the return loss. However, the available frequency range cannot be determined by the antenna frequency. For this reason, the available frequencies are determined in a range where the return loss is below a predetermined value, for example, -11.7 dB (VSWR1.7). The frequencies enclosed by the circle representin,g a return loss of -11.7 dB in the Smith chart are. available since the corresponding return losses are less than -11.7 dB.

It was found from the test results that the tested plane patch antenna had a resonance wave length (A) of 292 mm, a minimum available wave length Q,) of 333 mm, a resonance frequency (fo) of 1026 MHz, a band width (f) of 252 MHz and a fraction band width of 24.6% at a return loss of -11.7 dB.

Another test was conducted for a conventional plane patch antenna having a circular patch plate member. The diameter of the circular patch plate member was 156 mm (0.466A), the area of the circular patch plate member was 19,104 mm 2 (0.17 0A2), and the antenna height of the conventional plane patch antenna was 11 mm (0.0318A). The conventional plane patch antenna had a fraction band width of 12% or less at a return loss of -10 dB. It is, therefore, apparent that the plane patch antenna of the invention has a fraction band width much greater than that of the 11 conventional plane patch antenna in spite of the fact that the rhombic patch plate member of the plane patch antenna of the invention has an area 65% smaller than the area of the circular patch plate member of the the conventional plane patch antenna.

Although the tested plane patch antenna of the invention had an A/B ratio of 2: 1, where A is the length of the longer diagonal line of the rhombic patch plate member 12 and B is the length of the shorter diagonal line of the rhombic patch plate member 12, it is to be noted that the plane patch antenna has a similar effect as long as the A/B ratio is in a range from 4:1 to 3:2.

Still another test was conducted to show the effect of the plane patch antenna of the invention on the-frequency band width obtainable when it was placed in a synthetic resin casing. Two plane patch antennas 10 having a rhombic patch plate member 12, as shown in Fig. 5A, were placed in a casing 32 formed integrally with a high-mount stop lamp 34 having a number of LEDs arranged in the direction of the width W of the stop lamp 34, as shown in Figs. 8A and 8B. The tested plane patch antennas 10 have dimensions listed in Table 1. The casing 32 is made of a synthetic resin or other material which does not cause radio wave interference. It is to be noted that the values expressed in a unit of the resonance wave length (A) are different from the respective values listed in the third column of Table 1 and the values expressed in a unit of the minimum available wave length (A1) are different from the corresponding values listed in the fourth column of Table 1 since the resonance wave length (A) changes from 292 mm to 313 mm and the minimum available wave 12- length (A1) changes from 333 mm to 353 mm when the plane patch antennas 10 are placed in the casing 32.

The test results are shown in Figs. 9 and 10.

Fig. 9 is a graph showing frequency (MHz) versus return loss (dB) provided by the tested plane patch antenna. It is to be noted that the used resonance frequency (fo) is a value intermediate between the two values (indicated by Markers 2 and 3) at which the return loss is -11.7 dB rather than a value (indicated by Marker 1) at which the return loss is at minimum.

Fig. 10 is a Smith chart. It was found from the test results that the tested plane patch antenna had a resonance wave length (A) of 313 mm, a minimum available wave length (A1) of 353 mm, a resonance frequency (fo) of 960 MHz, a band width (,Lf) of 220 MHz and a fraction band width of 22.9% at a return loss of -11.7 dB.

Similarly, two conventional plane patch antennas 40 having a circular patch plate member, as shown in Fig. 1, were placed in a casing 42 formed integrally with a high-position stop lamp 44, as shown in Figs. 8C and 8D. The casing 42 is made of a synthetic resin or other material which does not cause radio wave interference.

In order to provide a good view from the successive vehicle, the highmount stop lamps 34 and 44 are mounted above a predetermined height. The highmount stop lamps 34 and 44 have a relatively long width W required to meet the standards. When the plane patch antennas are installed in a space such as a rear parcel or the like having a short depth, it is required for the plane patch antennas to have a short depth. The plane patch antenna of the invention having 1 13 a fraction band width of 22.9% has a width D of about 100 mm (0.321A), whereas the conventional patch antenna having a fraction band width of 7% has a width D1 of 156 mm (0.466A). It is) therefore, apparent that the casing 32 for receiving the plane patch antennas of the invention is required to have a depth Q much smaller than the depth Q1 of the casing 42 in which the conventional plane patch antennas are placed. In fact, the casing 32 in which the plane patch antennas of the invention are placed had a width W of 430 mmand depth Q of 145 mm.

It is, therefore, apparent from the foregoing that the invention provides an improved plane patch antenna having an increased available frequency band width. The plane patch antenna of the invention can be used in the rain with its est efficiency even when the antenna manufacturing and mounting tolerances are not critical. This is achieved by a combination of (1) patch plate member formed in a rhombic shape and (2) feeder shaft provided with a tapered portion extending from the patch plate member toward the earth plate member, the tapered portion having a crosssectional area decreasing as going away from the patch plate member. The reasons why the combination can increase the available frequency band width of the plane patch antenna are not fully understood, but some general observations for the reason why ---- the tapered portion can increase the available frequency band width of the plane patch antenna may be made. The tapered portion of the feeder shaft has a crosssectional area which is at maximum in the area of attachment to the patch plate member and decreasing as going away from the patch plate member. This structure i+ provides a smooth mechanical continuation between the patch plate member and the coaxial cable center threads which forms a part of the feeder shaft, thereby improving the matching between the patch plate member and the feeder shaft. Furthermore, the plane patch antenna of the invention consumes less space. This permits the plane patch antenna to be installed in a space such as a rear parcel or the like having a short depth.

Referring to Fig. 11, there is shown a modified form of the plane patch antenna of the invention which is generally the same as shown in Figs. 5A and 5B except that the plane patch antenna has a patch plate member 121 formed in a hexagonal shape. Accordingly like part are designated by like reference numerals.

The hexagonal patch p late member 121 has three pairs of opposite sides parallel with each other and symmetric with respect to the center of the hexagonal patch plate member 121. The hexagonal patch plate member 121 may be made by cutting the rhombic patch plate member 12 of Fig. 5A along respective lines normal to its longer diagonal line so as to shorten the length (A) by a value on its one side and by the same value on the other opposite side thereof, as shown in Fig. 11, or by cutting the rhombic patch plate member 12 of Fig. 5A along respective lines normal to its shorter diagonal line so as to shorten the width (B) by a value on its upper side and -by the same value on its lower side.

In Fig. 11, the character A indicates the,length of the hexagonal patch plate member 121, the character B is the width of the hexagonal patch plate member 121, the character E indicates the distance between the short pins 16 arranged on lines extending in the direction of the length of the hexagonal patch plate member 121, the character F indicates the distance between the short pins 16 arranged on lines extending in the direction of the width of the hexagonal patch plate member 121, and the character z indicates the maximum diameter of the feeder shaft 20.

Tests were conducted to show comparative performances of three plane patch antennas, one (X1) equipped with 'a rhombic patch plate member having a length (A) of 200 mm (0.772A), one (X2) equipped with a hexagonal patch plate member having a length (A) of 180 mm (0.750)made by cutting the rhombic patch plate member by 10 mm on each of the opposite sides (cut percentage = 10%), and one (X3) equipped with a hexagonal patch plate member having a length (A) of 170 mm (0.752A) made by cutting the rhombic patch plate member by 15 mm on each of the opposite sides (cut percentage = 15%). The other dimensions of these plane patch antennas are the same and listed in Table 2.

TABLE 2 xl X2 X3 B 100.0 mm 0. 386A 0.417A 0.442A z 55.0 mm 0.212,k 0.229A 0.243A t 13.0 mm 0.0502A 0.0542A 0.0575A E 81.0 mm 0.313A 0.338A 0.358A F 34.0 mm 0. 131 A 0.142A 0.150A S 3.2 mm 0.0124A 0.0133A 0.0142A In the first column of Table 1, B is the width of the patch plate member, z is the maximum diameter 16 of the feeder shaft 20, t is the antenna height, E is the distance between the short pins 16 arranged in lines extending in the direction of the length of the patch plate member, F is the distance between the short pins 16 arranged in lines extending in the direction of the width of the patch plate member, and S is the diameter of the short pins 16. These dimensions are expressed in millimeters in the second column of Table 2, and in a unit of the resonance wave length (A) in the second, third,and fourth column of Table 2 for the respective plane patch antennas X1, X2 and X3.

The test results are shown in Figs. 12 and 13 and listed on Table 3. Fig. 12 is a graph showing frequf,-ncy.(MHz) versus return loss (dB) provided by the tested plane patch antennas X1, X2, and X3. Curve (C,) relates to the plane patch antenna X1, curve (a) relates to the plane patch antenna X2, and curve (Y) relates to the plane patch antenna X3. It is to be noted that the used resonance frequency (fo) is a value intermediate between the two values (indicated by Markers 2 and 3) at which the return loss is -11.7 dB rather than a value (indicated by Marker 1) at which the return loss is at minimum. Fig. 13 is a Smith chart provided by the plane patch antenna X2.

TABLE 3 xl X2 X3 259 mm 240 mm 226 mm 1 301 mm 294 mm 288 mm fo 1157 MHz 1250 MHz 1330 MHz ,f 325 MHz 460 MHz 580 MHz Af/fo 28.0 % 36.8 43.6 % 17 It is, therefore, apparent that the plane patch antennas having a hexagonal patch plate member can provide a sufficient available frequency band width. The resonance wave length decreases as the cut percentage increases.

Another test was conducted for a plate patch antenna having a hexagonal patch plate member. The hexagonal patch plate member was made by cutting the rhombic patch plate member (Fig. 5A), which has a length (A) of 200 mm and a width (B) of 100 mm, along respective lines normal to its longer diagonal line so as to shorten the length (A) by 30 mm. (cut percentage 30%),on each of the opposite sides thereof.

The test results are shown in Figs. 14 and 15. Fig. 14 is a graph showing 'frequency (MHz) versus return loss (dB) provided by the tested plane patch antenna. It is to be noted that the used resonance frequency (fo) is a value intermediate between the two values (indicated by Markers 2 and 3) at which the return loss is -11.7 dB rather than a value (indicated by Marker 1) at which the return loss is at minimum. Fig. 15 is a Smith chart. It was found from the test results that the tested plane patch antenna had a resonance wave length (A) of 178 mm, a minimum available wave length (A1) of 199 mm, a resonance frequency (fo) of 1687 MHz3 a band width (4sf) of 365 MHz and a fraction band width (,Lf/fo) of 21.6%.

It is, therefore, apparent that the plane patch antenna can provide a sufficient available frequency band width. A similar effect can be obtained by a plane patch antenna having a hexagonal patch plate member made by cutting the rhombic patch plate member (Fig. 5A) along respective lines normal to its shorter 18 diagonal line so as to shorten the width (B) by 30% on each of the opposite sides thereof.

Referring to Fig. 16, there is shown another modified form of the plane patch antenna of the invention which is generally the same as shown in Figs. 5A and 5B except that the plane patch antenna has a patch plate member 122 formed in an octagonal shape. Accordingly like parts are designated by like reference numerals.

The octagonal patch plate member 122 has four pairs of opposite sides parallel with each other and symmetric with respect to the center of the octagonal patch plate member 122. The octagonal patch plate member 122 may be made by cutting the rhombic patch plate member 12 of Fig. 5A along respective lines -normal to its longer diagonal line so as to shorten the length (A) by a value on its one side and by the same value on the other opposite side thereof and by cutting the rhombic patch plate member along respective lines normal to the shorter diagonal line so as to shorten the width (B) by a value on its upper side and by the same value on its lower side.

In Fig. 16, the character A indicates the length of the octagonal patch plate member 122, the character B is the width of the octagonal patch plate member 122, the character E indicates the distance between the short pins 16 arranged on lines extending in the direction of the length of the octagonal patch plate member 122, the character F indicates the distance between the short pins 16 arranged on lines extending in the direction of the width of the octagonal patch plate member 122, and the character z indicates the maximum diameter of the feeder shaft 20.

im 19 Tests were conducted to show comparative performances of three plane patch antennas, one (Y1) equipped with a hexagonal patch plate memberhaving a width (B) of 100 mm (0.417A), one (Y2) equipped with an octagonal patch plate member having a width (B) of 90 mm (0.378A) made by cutting the hexagonal patch plate member by 5 mm (cut percentage = 10%) on each"of the opposite sides, and one (Y3) equipped with an octagonal patch plate member having a width (B) of 80 mm (0.336A) made by cutting the hexagonal patch plate member by 10 mm (cut percentage = 20%), The other dimensions of these plane patch antennas are the same and listed in Table 4.

TABLE 4

Y1 Y2 Y3 A 180.0 mm 0.750A 0.756A 0.756A z 55.0 mm 0.229A 0.231 A 0,231A t 13.0 mm 0.0542A 0.0546 A 0.0546A E 81.0 mm 0.338A 0.340 A 0.340A F 34.0 mm 0.142A 0.143 A 0.143A S 3.2 mm 0.0133A 0.0134A 0.013 In the first column of Table 4, A is the length of the patch plate member, z is the maximum diameter of the feeder shaft 20, t is the antenna height, E is the distance between the short pins 16 arranged on lines extending in the direction of the length of the patch plate member, F is the distance between the short pins 16 arranged in lines extending in the direction of the width of the patch plate member, and S is the diameter of the short pins 16, as shown in Fig. 16. These dimensions are expressed in millimeters ZO in the second column of Table 4, and in a unit of the resonance wave length (A) in the second, third, and fourth column of Table 4 for the respective plane patch antennas Y1, Y2 and Y3.

The test results are shown in Figs. 17 and 18 and listed in Table 5. Fig. 17 is a graph showing frequency (MHz) versus return loss (dB) provided by the tested plane patch antennas Y1, Y2 and Y3. Curve (0k) relates to the plane patch antenna Y1, curve (p) relates to the plane patch antenna Y2, and curve (V) relates to the plane patch antenna Y3. It is to be noted that the used resonance frequency (fo) is a value intermediate between the two values (indicated by Markers 2 and 3) at which the return loss is -11.7 dB rather than a value.(indicated by Marker 1) at which the return loss is at minimum. Fig. 18 is a Smith chart provided by the plane patch antenna Y3.

TABLE 5

Y1 Y2 Y3 240 mm 238 mm 238 mm 294 mm 289 mm 286 mm fo 1250 MHz 1258 MHz 1260 MHz Af 460 MHz 443 MHz 425 MHz Af/fo 36.8 % 35.2 % 33.7 % It is, therefore, apparent that the plane patch antennas having an octagonal patch plate member can provide a sufficient available frequency band width.

21

Claims

1. A plane patch antenna comprising: a conductive patch plate member having the shape of a rhomb, a hexagon, or an octagon; a conductive earth plate member; means for maintain the patch and earth plate members in spaced-parallel relation to each other and for making electrical connection between the patch and earth plate members; and a feeder shaft extending from the patch plate member, for electrical connection of the patch plate member to a lead wire, the feeder shaft having a tapered portion extending from the patch plate member toward the earth plate member, the tapered portion having a cross-sectional area which decreases going away from the patch plate member.

2. A plane patch antenna as claimed in claim 1, wherein the hexagon is made from a rhomb cut along two lines normal to a major diagonal of the rhomb and symmetric with respect to a minor diagonal of the rhomb.

3. A plane patch antenna as claimed in claim 1, wherein the hexagon is made from a rhomb cut along two lines normal to a minor diagonal of the rhomb and symmetric with respect to a major diagonal of the rhomb. 1 22

4. A plane patch antenna as claimed in claim 1, wherein the octagon is made from a rhomb cut along two lines parallel to a first diagonal of the rhomb and symmetric with respect to the first diagonal and along two lines parallel to a second diagonal of the rhomb and symmetric with respect to the second diagonal.

5. A plane patch antenna as claimed in claim 1, 2, 3, or 4, wherein the ratio of the diagonals of the rhomb is in a range from 1:4 to 2:3.

6. A plane patch antenna as claimed in any preceding claim wherein the tapered portion has a cone shape having a maximum diameter in its area of attachment to the patch plate member.

7. A plane patch antenna as claimed in any preceding claim, in which the said means comprises pins extending between the patch and earth plate members.

8. A plane patch antenna substantially as described with reference to, and as shown in, Figures SA and 5B or Figure 11 or Figure 16 of the accompanying drawings.

Published 1991 aQeMatentinOff 'P I 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.

lie I N po t =t H use. Cardffr Road. Newport. Gwent NP9 1RH. Further copies may be obtained from I Sales Branch. Unit 6., a. ach, Cross Keys. Newport. N