Plane Antenna Assembly

This invention relates to a plane antenna assembly which can remarkably increase its output.

The plane antenna of the type referred to is effectively utilizable in receiving waves and the like which are transmitted as carried on SHF band, in particular, 12 GHz band from a geostationary broadcasting satellite launched into cosmic space to be 36,000 Km high from the earth.

Antennas generally used for receiving circularly polarized waves from a geostationary broadcasting satellite are parabolic antennas erected on the roof or the like position of buildings. However, the parabolic antenna is susceptible to strong wind to easily fall due to its bulky structure so that an additional means for stably supporting the antenna will be necessary, and the supporting means further requires such troublesome work as a fixing to the antenna of reinforcing pole members forming a major part of the supporting means, which work may happen to result even in a higher cost than that of the antenna itself.

In attempt to eliminate these problems of the parabolic antenna, there has been suggested in Japanese Patent Appln. Laid-Open Publication No. 99803/1982 (corresponding to U.S. Pat. No. 4,475,107 or to German Offenlegungsschrift No. 3149200) is a plane antenna which is flattened in the entire configuration. This plane antenna comprises a plurality of cranked microstrip lines arranged in pairs on the upper surface of an antenna body of an insulating substrate of a Teflon glass fiber, polyethylene or the like an earthing conductor provided over the entire lower surface of the antenna body. The pairs of the microstrip lines are connected respectively at one end with each of branched strip line conductors of a power supply circuit provided on the antenna body in a tournament connection so that a travelling wave current can be supplied parallel to the respective paired microstrip lines at the same amplitude and phase. In such plane antenna, the travelling wave current is utilized to achieve a favourable antenna gain, and thus it is necessary to restrain any reflection of signal energy at the other terminating ends of the respective pairs of microstrip lines. For this purpose, the paired microstrip lines have been provided at the terminating ends respectively with such termination resistor as a chip resistor, so that any residual signal energy at the terminating ends of the respective paired microstrip lines can be absorbed by the resistors and any undesirable radiation phenomenon due to reflected signal energy can be prevented from occurring.

The foregoing plane antenna has simplified antenna structure to reduce its cost and the expense of repair work because the antenna can be mounted directly on an outdoor wall of buildings without requiring any additional supporting means. However, this plane antenna has been still defective in that, though the reflection of the signal evergy may be prevented, the signal energy is to be consumed at the resistors as Joule heat, which results in a large power loss and in a reduction in the antenna gain.

For resolving this problem, there has eeen proposed in U.S. patent application Ser. No. 819,610 (or German Patent Application No. 3601649.1) the arrangement of pairs of microstrip lines are provided at the terminating ends respectively with impedance-matched patch antenna means so that all the signal energy having reached the patch antenna means is radiated from the patch antenna means or, in other words, such signal evergy reached the patch antenna means is effectively utilized as radiation evergy. In this case, the power loss can be eliminated to some extent as compared with using the termination resistor.

To obtain a higher gain with the above arrangement, however, it becomes necessary to employ a plurality of the plane antennas having the patch antenna means, but this results in a larger power loss occurring at required power supply system, and it has been impossible to increase the antenna output to a level that the employed number of such plane antennas could naturally afford.

A primary object of the present invention is, therefore, to provide a plane antenna assembly which comprises a plurality of plane antenna bases and still ensures that a composite antenna output corresponding to the number of the antenna bases is obtained at a high gain and S/N ratio.

According to the present invention, the above object is attained by providing a plane antenna assembly which comprises a plurality of antenna bases and means connected to output ports of the respective antenna bases for combining outputs of the antenna bases into a composite antenna output. The output combining means includes a plurality of amplifiers each connected to the output port of the respective antenna bases for amplifying the output thereof, and means connected to the amplifiers for combining signals of the amplified antenna outputs into a composite antenna output signal.

Other objects and advantages of the present invention shall be made clear in the following description of the invention detailed with reference to preferred embodiments shown in accompanying drawings.

FIG. 1 shows schematically an arrangement in an embodiment of a plane antenna assembly according to the present invention;

FIG. 2 is a diagram of a signal compositer in the assembly of FIG. 1;

FIG. 3 is a fragmentary cross-sectional view of the signal compositer of FIG. 2;

FIG. 4 is a diagram of the signal receiving operation of the assembly of FI.. 5;

FIG. 5 shows schematically an arrangement in another embodiment of the plane antenna assembly according to the present invention;

FIG. 6 to 8 are circuit diagrams showing different amplifiers respectively used in the assembly of FIG. 5;

FIG. 9 shows schematically an arrangement in still another embodiment of the assembly according to the present invention;

FIG. 10 is a fragmentary cross-sectional view of the assembly of FIG. 9;

FIGS. 11 and 12 are schematic diagrams each showing the assembly in yet another embodiment of the present invention;

FIG. 13 is a schematic diagram showing an antenna base used in yet another embodiment of the present invention;

FIGS. 14 and 15 show schematically different side views the assembly using the antenna base of FIG. 13;

FIG. 16 is a circuit diagram of still another embodiment of the present invention;

FIG. 17 is a schematic perspective view of an embodiment of a supporting structure for the antenna bases to be used in the assembly of the present invention;

FIG. 18 is a schematic perspective view of another embodiment of the supporting structure;

FIG. 19 is a fragmentary cross-sectional view of the supporting structure of FIG. 18;

FIG. 20 is a diagram for explaining the supporting structure of FIG. 18; and

FIG. 21 is a fragmentary cross-sectional view of yet another embodiment of the supporting structure.

While the present invention shall now be described with reference to the preferred embodiments shown in the drawings, it should be understood that the intention is not to limit the invention only to the particular embodiments shown but rather to cover all alterations, modifications and equivalent arrangements possible within the scope of appended claims.

Referring to FIG. 1, a plane antenna assembly of the invention includes a plurality of plane antenna bases 11 and 11a (only two of which are illustrated in the drawing) which are each provided with a plurality of pairs of, for example, cranked microstrip lines connected respectively at one end with each of branched microstrip line conductors of a power supply circuit in a tournament connection so that a travelling wave current can be supplied in parallel to the respective pairs of the cranked microstrip lines at the same amplitude and phase. In this case, the paired microstrip lines of the plane antenna bases 11 and 11a may be provided in any other form than the cranked one. The antenna bases 11 and 11a are connected at their output ends with amplifiers 12 and 12a which form part of an output combining or composing means and which amplify antenna outputs. The amplifiers 12 and 12a comprise preferably a low-noise amplifiers.

Connected to the amplifiers 12 and 12a is a signal combiner means which forms a major part of the output combiner means. The signal composing means includes semi-ragid cables 13 and 13a, phase shifters 14 and 14a, and a combiner 15 comprising such a directional coupler made up of such microstrip lines as shown in FIG. 2. In the present case, a possible deviation in phase of received electromagnetic waves due to inherent difference in the wave-line propagation length is to be eliminated with means for adjusting the lengths of the cables 13 and 13a, and this adjusting means is to form an electrical length correcting means. Any phase deviation still not corrected by the length adjusting means can be corrected by the phase shifters 14 and 14a. The semi-rigid cables may be replaced by other power supply lines of which electrical power loss can be compensated for by the amplifiers 12 and 12a. Further, the combiner 15 should preferably be provided with an isolator.

The combiner 15 comprising the directional coupler should preferably be a so-called 3-dB coupler in which, as shown in FIGS. 2 and 3, a dielectric substrate 21 is provided on its rear side with an earthing conductor 20 and at its front side with a predetermined pattern of microstrip lines 22, the pattern of which has a basic length of 1/2 of .lambda.g including an equivalent wavelength contracting rate and is formed to have input terminals 23 and 23a for receiving amplified antenna output signals Sa and Sb, respectively, and output terminals 24 and 24a for outputting in-phase components and anti-phase components of the both signals, respectively, while a termination resistor 25 is usually connected to the output terminal 24. As the compositer, a Wilkinson type compositer may similarly be used, with which arrangement, too, the isolation effect can be attained between the both input terminals.

Next, the operation of the plane antenna assembly of FIGS. 1 to 3 will be explained. Now, the antenna outputs of the antenna bases 11 and 11a are amplified by the amplifiers 12 and 12a and then sent to the compositer 15 through the cables 13 and 13a and the phase shifters 14 and 14a, respectively. When the S/N ratio of the signals provided to the compositer 15 is assumed to be Sa/Na and Sb/Nb, a composite antenna output of the compositer 15 has an S/N ratio

which is improved by 3 dB. Since Sa=Sb=S, Na=Nb=N and Sa and Sb are of the same signal source, their composite signal output will simply be 2S but, as Na and Nb have no correlationship to each other, they will be the same N even when composed together. Therefore, it will be appreciated that, since the outputs of the antenna bases 11 and 11a are amplified by the low-noise amplifiers 12 and 12a and then provided to the output composing means, a sufficient gain security at the amplifiers 12 and 12a assures a sufficient compensation for the power loss in the power supply system, so that a large composite antenna output which is also improved in the S/N ratio can be obtained.

Referring here to FIG. 4, the electromagnetic waves sent from a broadcasting satellite BS will reach the respective antenna bases 11 and 11a through slightly different propagation lengths and the outputs of the antenna bases 11 and 11a will involve a deviation in their phase by an amount corresponding to a difference .DELTA.l between the spatial distances from the antenna bases to the satellite. This phase deviation is corrected to be zero by the cable-length adjusting means or electrical-length correcting means and the phase shifters 14 and 14a. This correction in effect is carried out on the basis of following equations, with an assumption that the antenna output signals Sa and Sb as amplified by the amplifiers 12 and 12a and provided to the compositer 15 are the simplest signals:

If .phi.a=.phi.b, then

whereas, if the phase is reversed to be .phi.a=.phi.b-.pi., then

Therefore, the signal level of the composite antenna output can be made maximum, with the S/N ratio also improved, by so adjusting the cable-length adjusting means and phase shifters 14 and 14a as to compose together the in-phase antenna output signals of a zero phase deviation.

Thus produced output of the compositer 15 is sent to an external circuit through a BS converter 16 and a cable 17.

Referring to FIG. 5, there is shown another ambodiment of the present invention in which the same constituent elements as those in the foregoing embodiment of FIG. 1 are denoted by the same reference numerals but added by 20. The present embodiment is arranged so that the composite antenna output of a compositer 35 is sent to a BS tuner 38 forming an external circuit through a BS converter 36 and a signal cable 37, and is featured in that the power supply is carried out from the tuner 38 through the cable 37 to antenna bases 31 and 31a. On the cable 37, generally, a direct current of 15 V is superimposed as fed from the side of the BS tuner 38 as a voltage fed to the BS converter 36. In this case, a separation unit 39 having a coil 39a for eliminating high frequency signals is attached to the signal cable 37, and a power unit 40 which generates at its output terminals +Vc, -Vc and GND positive and negative voltages to be supplied as stabilized, if required, to amplifiers 32 and 32a is connected to the separation unit 39.

A source voltage can be processed on the side of the amplifiers 32 and 32a. That is, the amplifiers 32 and 32a are so arranged that, in an aspect shown in FIG. 6, a DC voltage is superimposed on the amplified signals of the waves received at the antenna bases 31 and 31a and provided to the semi-rigid cables 33 and 33a, a positive voltage stabilized by a Zener diode ZDl is applied between the source and drain of an amplifying element Q of a GaAs-FET and a load voltage generated by a constant voltage circuit VR is applied to the gate of the amplifying element Q to amplify the antenna base outputs. In another aspect of the amplifiers 32 and 32a as shown in FIG. 7, the positive and negative voltages +Vc and -Vc from the power unit 40 are applied to the amplifying element Q so as to amplify the antenna base outputs. In still another aspect of FIG. 8, an AC voltage (a sinusoidal or a square wave voltage of a commercial source power) is superimposed on the semi-rigid cables 33 and 33a, in which event the AC voltage is rectified by diodes D1 and D2 connected to be opposite in the polarity to obtain the positive and negative voltages.

Other arrangement and operation of the embodiment of FIG. 5 are substantially the same as those in FIGS. 1 to 4.

In yet another embodiment shown in FIGS. 9 and 10, a plurality of antenna bases 51, 51a, 51b . . . (only four of which are illustrated in FIG. 9) are arranged on a single substrate. More specifically, a plurality of groups of microstrip lines for the antenna bases 51, 51a, 51b . . . are provided on a front side of a dielectric substrate 61 carrying on its rear side an earthing conductor 60, to each of which groups of the microstrip lines such amplifiers 52, 52a, 52b . . . as GaAs-FET's are respectively connected also on the substrate. With such arrangement, the electric power loss at interconnecting parts of the amplifiers 52, 52a, 52b . . . and at a power supply system can be minimized, a composite antenna output obtainable at an output terminal 64 of a compositer 55 connected to the respective amplifiers can be enlarged with an improved S/N ratio, while mounting cost of the amplifiers 52, 52a, 52b . . . is also reduced. Other arrangement and operation of this embodiment are substantially the safe as those in FIGS. 1 to 4.

Referring to FIG. 11 of a further embodiment, there are provided three antenna bases 71, 71a and 71b to output end of respective which each of amplifiers 72, 72a and 72b is coupled, a compositer 75 is connected to the amplifier 72 of the antenna base 71 and a further compositer 75a is connected commonly to the amplifiers 72a and 72b of the antenna bases 71a and 71b, while the both compositers 75 and 75a are interconnected with a 3-dB attenuator 76 interposed between them for equalizing the levels of input signals to the both compositers. Other arrangement and operation of the present embodiment are substantially the same as those in FIGS. 1 to 4.

Referring to yet another embodiment shown in FIG. 12, the antenna assembly comprises an antenna base 91 arranged to be capable of receiving both of left-handed and right-handed circularly polarized waves. In this example of the arrangement, amplifiers 92 and 92a for right-handed circularly polarized wave as well as amplifers 92b and 92c for left-handed circularly polarized wave are connected to both ends of the microstrip lines on the antenna base 91, and compositers 95 and 95a are arranged to respectively compose together outputs of the amplifiers 92 and 92a and outputs of the amplifiers 92b and 92c. Therefore, two power supply systems are thereby provided, and the assembly is made capable of dealing with both of the left-handed and right-handed circularly polarized waves. Other arrangement and operation of the present embodiment are substantially the same as those in FIGS. 1 to 4.

In a further embodiment shown in FIGS. 13 to 15, a plurality of antenna bases 111, 111a, 111b, 111c . . . corresponding in number to the desired gain are installed in a unit on a base board 118 through rotatable supports 117, 117a, 117b, 117c . . . respectively including each of angle adjusting means 116, 116a, 116b, 116c . . . for adjusting installation angle of the respective antenna bases with respect to the base board 118 by rotating them in direction of an arrow x in a side view of FIG. 13, so that the orientation of the respective antenna bases 111 . . . is made variable to provide to the antenna assembly an optimum wave-receiving directivity. In this embodiment, a cover 119 may be mounted over the antenna bases, if necessary. In this connection, the height h of the cover 119 from the base board 118 must be large enough for allowing the antenna bases to be fully rotated as desired, but the height h may be still kept not unduly large by, for example, reducing the length l of the respective antenna bases in their rotating direction. Other arrangement and operation of the present embodiment are substantially the same as those in FIGS. 1 to 4.

Still another embodiment shown in FIG. 16 is a plane antenna assembly, which comprises a signal switching circuit 140 provided for the purpose of allowing the assembly to be used for both of signal transmission and reception. That is, when a first switching member S1 is turned ON, a signal received at an antenna base 131 is provided through a diode D1 to an amplifier 132, whereas, when a second switching member S2 is turned ON, a transmission signal generated by a transmission circuit 141 is provided through a diode D2 to the antenna base 131 for transmission therethrough, so that the assembly can be selectively used either for transmitting or receiving the signal. Other arrangement and operation of the present embodiment are substantially the same as those of FIGS. 1 to 4.

According the still another feature of the present invention, means is provided for adjusting relative angle and position of the plurality of antenna bases to one another for easy phase shift adjustment between the respective antenna bases, without requiring any phase shifter, so as to eliminate any inherent loss at the phase shifter and to lower the manufacturing costs. Referring to FIG. 17 of an example of two antenna bases which are shown by chain-lines for brevity, one antenna base 151 is secured to an H-shaped stationary frame 156 which in turn is pivotably mounted through pivot pins 159 and 159a to vertically extending parallel beams 158 and 158a of a substantially .pi.-shaped base frame 157. The stationary frame 156 is provided with a depending piece 160 to which one end of a turn buckle 161 is pivotably secured while the other end of this turn buckle 161 is pivotably secured to one beam 158. A slide board 162 is vertically slidably mounted across lower parts of the both beams 158 and 158a by means of slidable engagement of pins in vertically extended slots made in the beams. Another antenna base 151a is also fixed to an H-shaped stationary frame 156a to which a depending piece 160a is attached, and another turn buckle 161 is pivotably secured at one end to the beam 158 and at the other end to the depending piece 160a. Fixedly provided between the beams 158 and 158a is a guide plate 163 in which an adjusting bolt 164 is axially rotatably held to extend vertical. The adjusting bolt 164 is screwed at its lower part into a threaded piece 165 secured to one side of the slide board 162. Attached also onto one side of the parallel beams 158 and 158a are a compositer 166 which is connected to power supply ends of the both antenna bases 151 and 151a so as to compose together outputs of the bases 151 and 151a as well as a converter 167 which converts a frequency of a reception signal of the compositer 166 in a 12 GHz band into 1 GHz.

In the present embodiment, the elevation angle of the antenna bases 151 and 151a can be adjusted by properly extending or shortening the turn buckles 161 and 161a relative to the antenna bases 151 and 151a, while the vertical position of the antenna base 151a with respect to the base 151 can be adjusted by properly turning the adjusting bolt 164 bacause the turning causes the slide board 162 and eventually the lower antenna base 151a to be moved upward or downward depending on the axial turning direction of the bolt 164. As a result, a phase shift between a plurality of antenna bases can be adjusted as desired. Other arrangement and operation of the present embodiment are substantially the same as those in FIGS. 1 to 4.

In another example shown in FIGS. 18 and 19 of the angle and position adjusting means, substantially the same members as those in the foregoing example of FIG. 17 are denoted by the same reference numerals but added by 20. In the present instance, the parallel beams of a substantially .pi.-shaped base frame 177 are divided into upper and lower sections 178, 178a and 178', 178a' respectively for supporting each of two antenna bases 171 and 171a, while these upper and lower beam sections are slidably coupled to each other at mutually joining parts. The lower beam section 178' has a cross section of saw tooth steps 188, while the upper beam section 178 is provided with a hook 190 having a finger projection 191 which is resiliently locked to one of the saw tooth steps 188 as biased by a spring 189, so that a relative position of the antenna bases 171 and 171a to each other can be suitably adjusted and set by lifting the hook 190 against the spring load, sliding the lower beam sections 178' and 178a' and engaging the finger 191 to another one of the steps 188. When the antenna assembly is to be installed in, for example, Osaka district of Japan, the elevation angle of the antenna assembly toward the broadcasting satellite is set to be 41 degrees and the antenna sidelook angle (90.degree.-.theta.) is set to be 26 degrees as shown in FIG. 20, wherein x represents a distance between the antenna bases 71 and 171a and y denotes a phase shift between them. In this case, the allowable range of the phase shift can be set to be .+-.12 degrees. Further, it is preferable that the lower beam sections 178' and 178a' are provided at their lower ends with pins 192 and 192a and, for example, a casing in which the plane antenna assembly is housed is provided with vertical slots 193 and 193a for receiving the pins 192 and 192' so as to provide a guiding function to the slide of the lower beam sections 178' and 178a'. Other arrangement and operation of the present embodiment are substantially the same as those in the embodiments of FIGS. 1 to 4 and FIG. 17.

In yet another example shown in FIG. 21, the parallel beams of the .pi.-shaped frame are also divided into two sections as in the case of FIGS. 18 and 19, but, in place of the saw tooth steps and hook arrangement, a lower beam section 198' is provided with resilient projections 208 and an upper beam section 198 is provided with opposing raws of holes 209 for receiving the projections 208, so that relative position of antenna bases to each other can be properly adjusted and set by engaging the projections 208 in suitable ones of the holes 209. Other arrangement and operation of the present embodiment are substantially the same as those in the embodiments of FIGS. 1 to 4, FIG. 17 and FIGS. 18 to 20.