JPH09232865A - Multi-beam antenna feeding circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the control mechanism by providing a pre-stage circuit for beam scanning to a pre-stage of a Batler matrix so as to attain beam scanning between directions of adjacent antenna beams. SOLUTION: This circuit is constituted of a pre-stage circuit section 120 and a Batler matrix section 116. The pre-stage circuit section 120 is a circuit provided with in general (N-1) input ports 112a1 -112aN and N output ports 115a1 -115aN, where N is the number of input or output ports of the Batler matrix 116 connected to the post-stage. Furthermore, the pre-stage circuit section 120 is constituted of (N-1) variable power distributers 1181 -118N and power combiners 1191 -119N. Then a high frequency signal fed to a k-th input port of the pre-stage circuit section 120 is given to a k-th variable power distributer 118k . Each variable power distributer is a circuit of one input and two-outputs and takes an optional branch ratio for its output and the two signals of the output are set in phase independently of the branch ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-beam antenna feeding circuit, and more particularly to a feeding circuit for a phased array antenna for transmitting or receiving multi-beams.

[0002]

2. Description of the Related Art An array antenna is composed of a plurality of element antennas and is used as if it were one antenna by simultaneously applying a high frequency signal to the element antennas. The phased array antenna can control the amplitude and phase (excitation amplitude phase distribution) of the high frequency signal applied to the element antenna, and variously change the direction and shape of the antenna beam. Particularly, in order to change the direction of the antenna beam, the phase of the high frequency signal given to the element antenna is controlled.

FIG. 1 shows an example of an N-element linear array antenna in which element antennas are arranged one-dimensionally at equal intervals, and shows that the antenna beam can be scanned by controlling the amplitude / phase distribution. Is. Description will be given assuming a transmission antenna. The output of the high frequency signal source 101 is input to the 1: N power divider 102 and is divided into N signals. The respective outputs of the 1: N power divider 102 are connected to the variable phase shifters 103 _{1 to} 103 _N and then to the element antennas 104 _{1 to} 104 _N. The phase (delay) of the high frequency signal applied to the element antennas 104 _{1 to} 104 _N is φ, φ + Δφ, φ + 2Δφ, ..., φ + (N−, by the variable phase shifters 103 _{1 to} 103 _N.
1) Set to Δφ. That is, each element antenna is given a phase delay represented by the tolerance Δφ arithmetic progression. Therefore, when the equiphase surface of the radio wave radiated from the array antenna is drawn, it becomes an equiphase surface 105 of the radio wave, and the traveling direction 106 of the radio wave is a direction inclined by an angle θ from the direction 107 in front of the antenna. Radio waves are emitted at the maximum level in the direction of angle θ. The angle θ satisfies the condition that radio waves radiated from N element antennas are added in phase,

Kdsin θ = Δφ (1)

[0005] Here, k is the wave number, d is the distance between the element antennas, and Δφ is the phase difference between adjacent elements.
From equation (1), the direction of the antenna beam θ when Δφ = 0
Becomes zero, and the traveling direction 106 of the radio wave coincides with the front direction 107 of the antenna. It can be seen that as the absolute value of Δφ increases, φ moves away from the front direction 107 of the antenna. Further, when Δφ> 0, the antenna beam faces downward in the plane of the drawing, and when Δφ <0, it faces upward. As described above, in the phased array antenna, the direction of the main beam is determined by the inclination of the phase distribution of the high frequency signal that excites the element antenna. In the above description, the transmission antenna is used as an example, but since the traveling direction of the signal is reversible in this circuit, the principle of antenna beam scanning described here is also applicable to the reception antenna.

An antenna capable of transmitting or receiving with a plurality of beams at the same time is called a multi-beam antenna. FIG.
Shows a configuration example of a phased array antenna that simultaneously generates M antenna beams using an N element array antenna. In the following description, an antenna for transmitting or receiving with multi-beam is called a multi-beam phased array antenna.

The circuit includes M independent high frequency signal sources 101a.
_{1 to} 101a _M , M 1: N power dividers 102a ₁ to
102a _M , an array of M variable phase shifters (number of arrays N)
103a _{1 to} 103a _M , M variable attenuator arrays (number N of arrays) 108a _{1 to} 108a _M , (M × N) input (M × N) output interconnection circuits 109, N
M: 1 power combiners 110a _{1 to} 110a _N , N power amplifiers 111 _{1 to} 111 _N , N element antennas 1
04a _{1 to} 104a _N.

For example, the output of the high frequency signal source 101a ₁ is input to the 1: N power distribution circuit 102a ₁ and distributed to N pieces. The N distributed outputs are respectively connected to an array 103a ₁ of variable phase shifters and an array 108 ₁ of variable attenuators, each of which has a phase and an amplitude so as to form an antenna beam having a desired direction and pattern. The value is set. The principle of setting the phase value is the same as that of the single beam phased array antenna described above. The variable attenuator is used to shape the beam pattern.
For the remaining high-frequency signal sources 101a _{2 to} 101a _M , respectively, similarly, 1: N power distributors 102a ₂ to 1
02a _M, the variable attenuator array 108a ₂ ~108a
_M, is connected to the array 103a ₂ ~103a _M variable phase shifter so as to form an antenna beam of interest, the value of the phase and amplitude of the RF signal is set.

The sum of the outputs of the variable phase shifter and the attenuator (N
The (× M) high frequency signals are input to the interconnection circuit 109 having (N × M) input / output terminals. In the subsequent stage of the interconnection circuit 109, N M: 1
The power combiner circuits 110 _{1 to} 110 _M are connected. For the i-th variable attenuator array 108i (1 ≦ i ≦ M), the interconnection circuit 109 outputs the first output to the M: 1 power combiner 110 ₁ and the second output to M: The 1-power combiner 110 ₂ has the role of connecting the N-th output to the N-th M: 1 power combiner 110 _N, and so on. The M: 1 power combiners 110 _{1 to} 110 _M combine the signals of M systems corresponding to the respective beams into one. M: 1
The respective outputs of the power combiners 110 _{1 to} 110 _M are amplified by the power amplifiers 111 _{1 to} 111 _{N and} fed to the element antennas 104a _{1 to} 104a _N. The radio waves radiated into space from the element antenna form M independent beams.

In the circuit of FIG. 2, there is a degree of freedom in which the _M beam directions and shapes can be arbitrarily set by the variable attenuator arrays 108 _{1 to} 108 _M and the variable phase shifter arrays 103a _{1 to} 103a _M. . However, the M beam N-element feeding circuit requires N × M variable phase shifters and variable attenuators, and the number becomes extremely large when the number of beams and the number of antenna elements are large. In addition, the configuration of the interconnection circuit 109 becomes complicated accordingly. Furthermore, M:
Another problem is the composite loss of high-frequency signals in the 1-power combiners 110 _{1 to} 110 _N. Even if an M: 1 power combiner with ideal characteristics is used, the output level for each input signal level is 1 / M, and signal attenuation is a major obstacle to signal transmission when the number of beams is large. .

In the multi-beam phased array antenna, when the beam arrangement may be fixed, it is conceivable to use a Butler Matrices for the feeding circuit. The Butler matrix is described in Reference J. Butler an
d R. Lowe, "Beam-Forming Ma"
trix Simplicities Design of
Electronically Scanned A
ntennas ”, Electronic Design
n, Vol. 9, pp. 170-173, Apr. 1
961. Is a high frequency matrix circuit proposed in. The Butler matrix has a plurality of (powers of 2) input ports and output ports, and is configured by connecting hybrid circuits and fixed phase shifters in multiple stages. A high frequency signal applied to a particular input port is distributed to all output ports with equal signal strength, and they have a phase relationship represented by an arithmetic progression. Each of the output ports is connected to an element antenna, the signal is radiated into space, and a beam in a specific direction corresponding to a given phase distribution is formed. Since a high frequency signal having a phase relationship with a different tolerance appears at each output port at each output port, a beam emitted in different directions is formed by inputting the signal at different input ports of the Butler matrix.

FIG. 3 shows a circuit configuration of a Butler matrix of 8 inputs and 8 outputs. The signal is fed to an 8-element array antenna and the beam can be formed in eight different directions by selecting the input port. The circuit is
High frequency signal input ports 112 _{1 to} 112 ₈ (4L, 3
A L, 2L, 1L, 1R, 2R, 3R, 4R) and a high-frequency signal output port 115 ₁ to 115 ₈ (A to H), 1
It is composed of two 90 ° hybrids 113 _{1 to} 113 ₁₂ and fixed phase shifters 114 _{1 to} 114 ₁₆ . When a high frequency signal is applied to one of the input ports 112 _{1 to} 112 ₈ , the signal is split into two by one of the 90 ° hybrids 113 _{1 to} 113 ₄ and the fixed phase shifter 114 ₁ to
Two of 114 ₈ provide the phase delay. Two signals will four further second distribution becomes the input to the next stage of the 90 ° hybrid 113 _{5-113 8.} The four signals are given a phase delay by four of the fixed phase shifters 114 _{9 to} 114 _{16 in} the next stage. These signals are further inputted to the next stage of the 90 ° hybrid 113 _{9-113 12} 2 dispensed, is ultimately 8 dispensed. By repeating the signal distribution by the 90 ° hybrid and the setting of the phase delay by the fixed phase shifter, a signal having a phase relationship represented by another arithmetic sequence for each input port appears at the output port.

FIG. 4 shows a multi-beam antenna beam pattern formed by the 8-element Butler matrix of FIG. The pattern shown is obtained by calculation. In the calculation, the directional characteristics of the element antennas are omnidirectional, and the element spacing is half a wavelength. High frequency signal input port 11
_{2 1 ~112 8 (4L, 3L} , 2L, 1L, 1R, 2
R, 3R, 4R), respectively, -61
°, -38.7 °, -22 °, -7.2 °, 7.2 °,
It can be seen that eight independent beams are formed in the 22 °, 38.7 ° and 61 ° directions. In the figure,
4L, 3L, 2L, 1L, 1R, 2R, 3R, 4R beams are named.

In the multi-beam forming circuit using the Butler matrix, there are restrictions such that the beam direction and the space that can be formed are fixed, the number of input ports and the number of output ports are equal, and the numbers are powers of 2. . However, when the number of input or output ports is M, the number of components that make up the circuit is on the order of 0 (M x log M), and even with a multi-beam multi-element array antenna, the scale of the circuit explosively increases. do not do. In the circuit of FIG. 2, the power loss in the power combiner 110 is a problem,
The Butler matrix also has the advantage that it is lossless in principle.

[0015]

The Butler matrix described in the preceding paragraph is compared with the feeding circuit of the multi-beam phased array antenna having the general structure shown in FIG.
The number of elements that make up the circuit is very small. The advantage is that the circuit is lossless.

However, there is a limitation that the formed beams have a fixed interval with respect to the direction. The multi-beam feeding circuit having the general configuration shown in FIG. 2 can form a beam having an arbitrary direction and shape in principle, but the number of variable phase shifters and the variable attenuation are proportional to the product of the number of beams and the number of elements. Circuit is large-scale, and it is necessary to control a huge number of these elements in order to scan the beam.

It is an object of the present invention to provide a beam forming circuit for a multi-beam phased array antenna having the following conditions. (1) The beam scanning property is given to the circuit to some extent without increasing the circuit scale or the power loss in the circuit so much. (2) The control for beam scanning is simplified, and one beam scanning is performed by one control element. (3) Side lobe level characteristics are not deteriorated by beam scanning.

[0018]

In the present invention, the most main feature is to realize a feed circuit for a multi-beam phased array antenna by combining a "front circuit" and a Butler matrix. The front-end circuit is an array of electric distributors (variable power distributors) whose coupling ratio is variable, and applies signals to a plurality of input ports of the Butler matrix at the same time. The pre-circuit has a function of scanning the antenna beam by adjusting the coupling ratio of the power divider and weighting the signal given to the Butler matrix. In the conventional Butler matrix, the directions and intervals of the antenna beams that can be formed are fixed, but the present invention is different in that they can be changed. Since the entire circuit has a configuration in which only a front circuit is added to the Butler matrix, the circuit does not become complicated in proportion to the product of the number of beams and the number of array elements, and the simplification of the circuit configuration is maintained. .

In the section of the prior art, it is explained in FIG. 1 that the direction of the main beam of the antenna can be changed by changing the inclination of the excitation phase distribution in each element antenna of the array antenna as represented by the arithmetic progression. did.

In the Butler matrix, different slopes of the phase distribution are obtained for each input port. FIG. 5 shows the phase value of the high-frequency signal appearing in each element antenna when a signal is applied to each input port of the 8-input 8-output Butler matrix, that is, the excitation phase distribution. However, FIG. 6 shows the Butler matrix shown in FIG. 3 in order to perform the phase adjustment so that the absolute values of all phases match at the center of the aperture plane of the array antenna (the center of the fourth and fifth element antennas). To improve. FIG. 6 shows an 8-element Butler matrix in which a fixed-phase array is added to the input section in order to obtain the result of FIG. The difference from the Butler matrix of FIG. 3 is that the high frequency signal input ports and 112 _{1 to} 11
2 ₈ and is to newly provided an array of fixed phase shifters 114 _{17-114 24} between 90 ° hybrid 113 _{1-113 4.} From FIG. 5, when a high frequency signal is input to each input port of FIG. 6, between the elements in the order of −157.5 °, −112.5 °, −6 in the antenna aperture plane.
7.5 °, -22.5 °, 22.5 °, 67.5 °, 1
It can be seen that signals having a phase difference of 12.5 ° and 157.5 ° can be obtained. The signal strength appearing at each output port is constant regardless of the element. Due to the difference in the excitation distribution described above, antenna beams in different directions are formed. That is, when a signal is applied to a certain input port, a beam in a specific direction is formed, and the input port and the formed beam have a one-to-one relationship.

It is assumed that the signal of one high-frequency signal source is divided into two and is given to the input ports forming adjacent beams in the Butler matrix while keeping the in-phase relationship between the signals. Of the two input ports, a signal is applied to the first input port to obtain a first excitation distribution, and a signal to the second input port is obtained to obtain another second excitation distribution. . If signals are simultaneously applied to these two input ports, it can be expected that a signal having an intermediate slope will be obtained at the output ports. Further, the slope of the phase of the output port can be adjusted between the slope of the first excitation distribution and the slope of the second excitation distribution by changing the branching ratio of the signals given to the two input ports. Excitation distribution and antenna beam are 1: 1
Therefore, by applying signals simultaneously to the two input ports, a beam having an intermediate direction between the beam corresponding to the first input port and the beam corresponding to the second input port can be formed. By weighting the signals input at the same time, the beam direction can be scanned in the range between the first beam direction and the second beam direction. This is the basic principle of the present invention.

The above idea is that the output of a certain high-frequency signal source is divided into N pieces, the signals are simultaneously input to N input ports forming adjacent beams in the Butler matrix, and the signals of the N ports are weighted. Can be expanded to a circuit for scanning a beam.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION In the following, a feeding circuit that enables beam scanning between directions of two adjacent beams of a Butler matrix by simultaneously applying signals to input ports forming the two adjacent beams. explain.

FIG. 7 shows the configuration of the entire circuit when an 8-element Butler matrix is used in the first embodiment of the present invention. The circuit is a "pre-circuit" section 120 and a "Butler matrix". It is composed of a section 116.

If the number of input or output ports of the Butler matrix connected to the subsequent stage is N (here, N = 8), the front-end circuit 120 generally has (N-1) input ports 112a _{1 to} 112a _N. And N output ports 115a
A circuit having a _{1 ~115a N.} The high frequency signal applied to the k-th (1≤k≤ (N-1)) input port of the pre-circuit appears at the k-th and (k + 1) -th output ports of the pre-circuit. With respect to the high-frequency signal applied to the k-th input port, the high-frequency signal appearing at the k-th and (k + 1) -th output ports has a constant total power, and the branching ratio can be set arbitrarily. With the characteristics of. The phases of the two high frequency signals are always in phase.

The front-end circuit includes (N-1) variable power distributors 118 _{1 to} 118 _N and power combiners 119 _{1 to} 119 _N.
It is composed of The high frequency signal applied to the k-th input port of the pre-circuit is the k-th variable power distributor 118 _k.
Is input to

The variable power distributor is a circuit with one input and two outputs,
The output can have any branching ratio, and the two signals at the output are in phase regardless of the branching ratio. 8a and 8b show two examples of the configuration of a single variable power distributor, and FIG. 8c shows the characteristics obtained by calculation.

The variable power distributor of FIG. 8a comprises 90 ° hybrids 113a ₁ and 113a ₂ , a variable phase shifter 113b.
And a terminating resistor 121. The high frequency signal is input to the 90 ° hybrid 113a ₁ . 90
The hybrid is a four-terminal network, and the signal input to the first port in the figure is output to the third and fourth ports with equal signal strength. However, when comparing the phases of the signals of the third port and the fourth port, the output signal of the fourth port has a phase delay of 90 degrees with respect to the output signal of the third port. Since the second port is not used, a terminating resistor is connected. 90 °
The third port of the hybrid 113a ₁ is connected to the first port of the 90 ° hybrid 113a ₂ via the variable phase shifter 103b, and the fourth port of the 90 ° hybrid 113a ₁ is connected to the second port of the 90 ° hybrid 113a ₂ . And the distributed signal is 90 ° hybrid 1
It is synthesized again at 13a ₂ .

Third phase of 90 ° hybrid 113a _1- variable phase shifter 103b-90 ° hybrid 1 when the phase delay provided by variable phase shifter 103b is zero.
A signal from the first port of 13a ₂ to the third port,
The fourth port of the 90 ° hybrid 113a _1- The signals reaching the third port via the second port of the 90 ° hybrid 113a ₂ have a phase difference of exactly 180 degrees and cancel each other out, resulting in the third port of the hybrid. There is no signal output. On the other hand, 90 ° hybrid 113a ₁ of the third port - a signal leading to the fourth port via the first port of the variable phase shifter 103b-90 ° hybrid 113a _2, 90 ° fourth port -90 hybrid 113a ₁
° The signals from the second port of the hybrid 113a ₂ to the fourth port will be in phase and will strengthen each other, and all the input signals will be 90 ° hybrid 113a ₂
Output to the 4th port of.

When the phase delay provided by the variable phase shifter 103b is 180 degrees, the 90 ° hybrid 113a ₁ has the third port-variable phase shifter 103b-90 degrees.
The signal reaching the third port via the first port of the hybrid 113a ₂ and the fourth port of the 90 ° hybrid 113a ₁ -the signal reaching the third port of the 90 ° hybrid 113a ₂ via the fourth port are in phase, and the input signal Output to the third port of the 90 ° hybrid 113a ₂ . On the other hand, the third port of the 90 ° hybrid 113a _1- the variable phase shifter 103b-the signal appearing at the 4th port of the 90 ° hybrid 113a ₂ via the 1st port of the 90 ° hybrid and the 4th port of the 90 ° hybrid 113a _1- The phase difference of the signal appearing at the fourth port through the second port of the 90 ° hybrid 113a ₂ becomes 180 degrees,
The output of the fourth port of the second hybrid 113a ₂ becomes zero.

FIG. 8c shows the third port of the 90 ° hybrid 113a ₂ (the output port of the first high frequency signal) when the value of the phase delay provided by the variable phase shifter 103b is changed from 0 to 360 degrees. 115b ₁ ) and the fourth signal (output port 115b ₂ of the second high-frequency signal), the intensities of the two signals and their relative phases are plotted. It is understood that the branching ratio of the outputs of the two ports can be set to an arbitrary value by changing the value of the variable phase shifter 103b. Moreover, it can be read that the relative phase of the signal between the two output ports is constant at zero between 0 and 180 degrees of the phase delay due to the variable phase shifter, regardless of the value.

In the variable power distributor shown in FIG. 8a, 9
It is also possible to replace the 0 ° hybrid 113a ₁ with a Wilkinson power divider. The circuit configuration is shown in FIG. 8b. The Wilkinson power distributor 122 is a one-input, two-output circuit, and the circuit outputs two signals in equal phase and in phase with the input high frequency signal. The circuits of FIGS. 8a and 8b are completely interchangeable, and the circuit configuration shown in FIG.
The characteristic shown in c is obtained.

(N-1) variable power distributors 118 ₁ to
Next to the array of 118 _N-1 are N power combiners 11
9 ₁ ~119 _N is located. First output of k-th variable power distributor 118 _k (output from second port)
Is added as it is to the second input port (third port) of the k-th power combiner 119 _k . In addition, the second output of the _kth variable power distributor 118 _k (the output from the third port) is the (k + 1) th power combiner 119.
_{k + 1} is added to the first input port (second port).
In addition, the input terminal of the _first power combiner 119 ₁ (second
Port) and the second input terminal (second port) of the _Nth power combiner 119 _N are terminated because there is no signal input.

With the circuit configuration described above, the signal applied to the k-th input port 112a _k of the pre-circuit 120 is the k-th and (k + 1) -th output port 115 _k , 115 of the pre-circuit 120. Appear in an arbitrary distribution ratio while maintaining the in-phase relationship at _{k + 1} . The branching ratio is variable power divider 118 _k
It is variable according to the value of the variable phase shifter inside.

The output of the k-th power combiner 119 _k (the output of the first port) is the array 1 of the fixed phase shifter, respectively.
Butler matrix 11 through 14a _{1 to} 114a _N
6 is connected.

Array of fixed phase shifters 114a _{1 to} 114a
The combination of _N and the Butler matrix 116 corresponds to the Butler matrix 117 shown in FIG.
The role of the array of fixed phase shifters is to match the absolute phase of the center of the array antenna aperture to all input ports.

Fixed phase shifters 114a _{1 to} 11 in FIG.
The value set to 4a _N was examined. The values for the Butler matrix of 4, 8, and 16 elements are shown in FIG.
However, the input ports of the Butler matrix are 2L, 1L, 1R, 2R beams for 4 elements, 4L, 3L, 2L, 1L, 1R, 2R, 3R, 4R beams for 8 elements, and 16 elements. 8L, 7L, 6L, 5L, 4L,
3L, 2L, 1L, 1R, 2R, 3R, 4R, 5R, 6
It is assumed that they are aligned so as to sequentially form R, 7R, and 8R beams. However, the beam numbers are 1, 2, 3, ... From the one closest to the antenna front direction 106 defined in FIG. 1, and the radio wave traveling direction (corresponding to the antenna main beam direction) 106 is shown. Is shown according to the rule that L is upward and downward is R.

The signal input to a certain port of the Butler matrix is distributed in the circuit by the number of array elements,
They satisfy the phase relationship for forming a beam in a particular direction. When the signal is applied only to the kth input port, the kth beam is formed. The (k +
When a signal is applied only to the 1) th input port, the (k + 1) th beam adjacent to the kth beam is formed. In this case, since the same signal is input to the kth and (k + 1) th input ports, a beam is formed in the intermediate direction. The beam direction depends on the signal splitting ratio. For example, when the branching ratio is 1: 1, the kth
Beams are formed at the centers of the th and (k + 1) th positions. If the signal at the kth port is stronger, the beam is at the kth port.
The beam approaches the direction of the kth beam, and if the (k + 1) th port is stronger, the beam approaches the direction of the kth beam. As a special case, the signal power may be concentrated on the k-th or (k + 1) -th port (when the value of the variable phase shifter in the variable power distributor 119 _k is 0 or 180 °). Beams are formed in their respective directions.

FIGS. 9a to 9d show antenna beam patterns formed by the above-mentioned 7-input / 8-output beam forming circuit. The antenna beam pattern is obtained by calculation, and the element antenna directivity is omnidirectional, and the installation intervals are half wavelength. 9a, 9b, 9c, and 9d, depending on the value of the set point of the variable phase shifter,
0 variable power distributors 118 ₁ , 118 ₂ , 118 ₃ , 1
The setting value β of the variable phase shifter in 18 ₄ is used as a parameter,
The beam pattern is plotted. When the set value β of the variable phase shifter changes from 0 to 180 °, the main beam direction is −38.7 ° to −61 ° in FIG. 9a, and the main beam direction is −22 ° to −38. 7 °, Figure 9c
It can be seen that there is a change from −7.2 ° to −22 °, and in FIG. 9d from + 7.2 ° to −7.2 °. Beam scanning can be performed independently at each port. The front circuit 12
The characteristics for the remaining 0 input ports are shown in FIGS.
b, it is considered to be symmetrical with the case of FIG.

FIGS. 10a and 10b are a summary of the formed antenna beam shown in FIGS. 9a-9d, where the beam direction, gain, first side lobe level,
The four beam half widths are plotted using the set value β of the variable phase shifter as a parameter. From FIG. 10a, it is clear that the beam direction is variable depending on the value of the variable phase shifter. Also, there is a slight variation in antenna gain with changes in beam direction. The variation of the antenna gain is the same regardless of the input port, and the branching ratio is 1: 1.
= 90 °, the antenna gain becomes the lowest, and the level becomes relatively −0.85 dB smaller. The antenna gain is reduced by adding the front circuit, that is, the power loss of the circuit is 3
Is about 3.86 dB. Further, from FIG. 10b, the level of the first side lobe with respect to the main beam is −12.8 dB at β = 0 ° or 180 °, but β = 9.
Minimum value of -24 dB when 0 °, that is, distribution ratio of 1: 1
You can read that. The state of change is the same regardless of the input port (beam). It can be seen that in the present invention in which the pre-circuit is connected to the Butler matrix, the side lobe level does not deteriorate. Further, the beam half width also changes as the value of the variable phase shifter changes.

The configuration and circuit characteristics of the multi-beam forming circuit for the (N-1) beam N element using the Butler matrix capable of beam scanning have been described above. In the description, the transmission system was assumed, but this circuit can also be applied as a multi-beam forming circuit for a receiving antenna.

FIG. 12 is a diagram showing the configuration of the entire circuit in the second embodiment of the present invention. Circuit is (N-2)
Input N output matrix circuit, front circuit 120, second
The front circuit 123 and the Butler matrix 116 are included. The front circuit 120 is (N-2)
Input (N-1) output, second pre-circuit 123 (N-
1) A matrix circuit having N inputs and N outputs. However, N is the number of input ports or output parts of the Butler matrix. FIG. 12 shows the case where N = 8.

In FIG. 12, the high frequency signal input port 1
The high frequency signal of the front circuit 120 is input from 12a _{1 to} 112a _N-2 . The front-end circuit of FIG. 12 has one less input / output port and one less variable power distributor and one power combiner than in the case of the first embodiment, but the circuit configuration and The operation is the same. The k'th
Th (1 ≦ k signals applied to '(N-2)) 112a k _of' is input to the k 'th variable power distributor 118 _k', divided into any ratio to two output ports The output signal is output. One output of the k'th variable power distributor 118 _k'is one of the input ports of the k'th power combiner 119 _{k '} , and the other output is the (k' + 1) th power combiner. It is added to one of the 119 _{k '+ 1} input ports. The (N-1) outputs of the pre-circuit 120 are the second
Is input to the pre-circuit 123.

The second front-end circuit 123 is composed of an array of (N-1) power distributors 122 _{1 to} 122 _{N-1 and} an array of N power combiners 119 _{N to} 119 _2N-1. ing. The high frequency signal applied to the k'th port of the second pre-circuit 123 is the k'th power distributor 122 _{k '.}
Is input to the signal and the signal is divided into two while maintaining the in-phase relationship. One of the signals divided by the power distributor 122 _{k ′} is the front circuit 1
23 is added to one of the inputs of the _k'th power combiner 119 _{N + k'-1 and} the other is added to one of the inputs of the (k '+ 1) th power combiner 119 _{N + k'.} . Even in the power combiner, the two signals are combined in phase. Note that the first and Nth power combiners 11 in the front-end circuit 123 are
Since only one signal is given to 9 _N and 119 _2N-1 , a terminating resistor is connected to the input port to which no signal is given.

Pre-circuit 120 and second pre-circuit 123
Together form a circuit with (N-1) inputs and N outputs. The signal applied to the k-th high-frequency signal input port 112a _{k ′} is the k-th, k ′ + 1, k ′ + of the second pre-circuit.
The signal strength at the second output port is α / 8: 1/8:
Appear at a ratio of (1-α) / 8 while maintaining the in-phase relationship. Here, α represents a power branching ratio in the variable power distributor, and outputs a signal with an intensity ratio of α: (1−α). Also,
The Winkinson power distributors 122 _{1 to} 122 _N-1 distribute the signals with equal signal strength, and the power combiners 119 _{1 to} 119 _2N.
Combines the two signals with equal signal strength.

The circuit configuration after the output of the second front-end circuit 123 is the same as that described in the first embodiment.
The N outputs of the second front-end circuit 123 are connected to the Butler matrix 116 via arrays 114a _{1 to} 114a _N of fixed phase shifters.

Next, the antenna beam pattern formed by the above-mentioned 6-input / 8-output beam forming circuit was calculated. They are shown in Figures 13a to 13c. In the calculation, the element antenna is omnidirectional, and the element spacing is half wavelength. The variable power distributor of the front end circuit 120 is shown in FIG.
It is constructed as shown in b, and its branching ratio changes depending on the value of the variable phase shifter in the circuit. If the branching ratio of the variable power distributor changes, the branching ratio of the signals appearing at the three adjacent ports of the second pre-circuit also changes, and the antenna beam can be scanned. 13a to 13c, the setting value β of the variable phase shifter in the variable power distributors 118 ₁ , 118 ₂ and 118 ₃ of the front-end circuit 120 is used as a parameter, and β is 0 to 180.
It is a plot of the beam pattern when the angle is changed by 30 ° to 30 °. In Figure 13a the main beam direction is -30 ° to -48.6 °, in Figure 13b the main beam direction is -14.5 ° to -30 ° and in Figure 13c it is 14.5 ° to -14.5 °. It can be seen that the range changes. Beam scanning is performed independently at each port. Note that the characteristics of the remaining input ports of the front-end circuit 120 are considered to be symmetric to the cases of FIGS. 13a, 13b, and 13c, and are therefore omitted.

FIGS. 14a and 14b summarize the characteristics of the shape of the antenna beam shown in FIG. The beam direction, the gain, the level of the first side lobe, and the beam full width at half maximum are plotted using the set value β of the variable phase shifter as a parameter. From FIG. 14a, the relationship between the value of the variable phase shifter and the beam direction can be seen for each beam. There is a slight variation in antenna gain with changes in beam direction. Also in the circuit of the present embodiment example of FIG. 12, as in the case of the circuit of the first embodiment example, the variation of the antenna gain is the same regardless of the input port. Β with a ratio of 0: 1 or 1: 0
When = 0 ° or 180 °, the antenna gain becomes the minimum, and the level becomes relatively small by −0.85 dB. Also, the overall level of antenna gain is lowered by adding the front circuit, that is, the power loss of the circuit is 6.02 to 6.87d.
B. From FIG. 14b, it can be seen how the side level changes. The level of the first side lobe with respect to the main beam is -24 dB at β = 0 ° or 180 °.
However, the minimum value of −31 dB is obtained when β = 90 °, that is, the distribution ratio becomes 1: 1. The state of change is the same regardless of the input port (antenna beam). In the present invention in which the pre-circuit is connected to the Butler matrix, it is understood that the addition of the pre-circuit does not deteriorate the side lobe level. The beam half width also changes with the change in the value of the variable phase shifter.

The configuration and characteristics of the multi-beam forming circuit for the (N-2) beam N element capable of beam scanning using the Butler matrix have been described above. Although this description has been made assuming a transmission system, this circuit can be applied as a multi-beam forming circuit of a receiving antenna.

The configuration and circuit characteristics of the multi-beam forming circuit for (N-1) beam N element using the Butler matrix capable of beam scanning have been described above. In the description, the transmission system is assumed, but this circuit can be applied to the reception antenna.

[0051]

The Butler matrix is a beam forming circuit for a multi-beam phased array antenna. Although it is possible to form multi-beams with a small circuit scale, only fixed beams can be formed. The present invention is characterized in that a pre-circuit for performing beam scanning is provided in the preceding stage of the Butler matrix. By using the pre-circuit to input signals to the input ports forming adjacent antenna beams of the Butler matrix at the same time and with weighting, the beams can be scanned between the directions of the adjacent antenna beams. The power loss of the circuit due to the addition of the front circuit was as small as about 3 to 4 dB in the case of Example 1, for example. Further, the circuit for weighting signals (variable power divider) is composed of two hybrids and one variable phase shifter, and the distribution ratio is determined by the value of the variable phase shifter. As a result, the beam can be scanned by controlling one variable phase shifter, and the control mechanism can be greatly simplified. Furthermore, it is clarified that the antenna side lobe level does not deteriorate by connecting the pre-circuit.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of beam scanning in a phased array.

FIG. 2 is a diagram showing a configuration example of a multi-beam phased array antenna.

FIG. 3 is a diagram showing a circuit configuration of an 8-input 8-output Butler matrix.

FIG. 4 is a diagram showing eight antenna beam patterns formed by a Butler matrix with eight inputs and eight outputs.

FIG. 5 is a diagram showing an excitation phase distribution obtained by an 8-element Butler matrix.

6 is a diagram showing a circuit configuration of an 8-input 8-output Butler matrix that realizes the excitation phase distribution of FIG. 5;

FIG. 7 is a diagram showing an example of a first exemplary embodiment of the present invention.

FIG. 8a is a diagram showing a configuration example of a variable power distributor.

FIG. 8b is a diagram showing another configuration example of the variable power distributor using the Wilkinson power distributor.

FIG. 8c shows the transmission characteristics of the circuit of FIG. 8a or 8b.

9a is a diagram showing an antenna beam pattern formed by the circuit of FIG. 7 and a diagram showing beam scanning characteristics. FIG.

9b is a diagram showing an antenna beam pattern formed by the circuit of FIG. 7 and a diagram showing beam scanning characteristics. FIG.

9c is a diagram showing an antenna beam pattern configured by the circuit of FIG. 7 and a diagram showing beam scanning characteristics. FIG.

9d is a diagram showing an antenna beam pattern configured by the circuit of FIG. 7, and is a diagram showing beam scanning characteristics. FIG.

FIG. 10a is a diagram showing a change in antenna gain and direction according to a change in a setting value of a variable phase shifter in a front circuit.

FIG. 10b is a diagram showing changes in the level of the first side lobe and the beam half width.

11] Fixed phase shifters 114a _{1 to} 114 in FIG.
is a diagram showing the values for Butler matrix 4, 8, 16 elements for a value to be set to a _N.

FIG. 12 is a diagram showing an example of a second exemplary embodiment of the present invention.

13A is a diagram showing an antenna beam pattern configured by the circuit of FIG. 12 and a diagram showing beam scanning characteristics. FIG.

13B is a diagram showing an antenna beam pattern configured by the circuit of FIG. 12 and a diagram showing beam scanning characteristics.

FIG. 13c is a diagram showing an antenna beam pattern configured by the circuit of FIG. 12, showing beam scanning characteristics.

FIG. 14a is a diagram showing a change in antenna gain and direction according to a change in a setting value of a variable phase shifter in a front circuit.

FIG. 14b is a diagram showing changes in side lobe level and beam half width.

[Explanation of symbols]

101, 101a _{1 to} 101a _M high frequency signal source 102, 102a _{1 to} 102a _M 1: N power distributor 103 _{1 to} 103 _N variable phaser 103a _{1 to} 103a _M , 103b array of variable phaser (N element) 104 ₁ to 104 _N , 104 b _{1 to} 104 b _N element antenna 105 Equal phase surface of radio wave 106 Direction of traveling radio wave (direction of antenna main beam) 107 Front direction of antenna 108 _{1 to} 108 _M Array of variable attenuators (N element) 109 Interconnection circuit 110 ₁ ~110 _N M: ₁ power combiner 111 ₁ - 111 _N power amplifiers _{112 1 ~112 8, 112a 1 ~112a} N, 112
b RF signal input port 113 ₁ ~113 ₁₂ 90 ° hybrid 114 _{1-114 16} fixed phase shifters 114a ₁ ~114a _N fixed phase shifters _{115 1 ~115 8, 115a 1 ~115a} N, 115
b ₁ , 115b ₂ High frequency signal output port 116 8 element Butler matrix 117 8 element Butler matrix with phase array 118 _{1 to} 118 _N-1 variable power distributor 119 _{1 to} 119 _N , 119 _{1 to} 119 _2N-1 power combining Device 120 pre-circuit 121 terminating resistors 122, 122 _{1 to} 122 _N-1 Wilkinson power distributor 123 second pre-circuit

Claims (4)

[Claims] 1. A variable power divider having one input and two outputs (N-
1) array (N is a positive integer) and N of 2 inputs and 1 output
And an array of power combiners, the k-th (1 ≦ k
≦ N−1, k is a positive integer) is connected to the k-th variable power distributor to divide the signal into two at an arbitrary branching ratio while maintaining the in-phase relationship between the output signals, One output of the kth variable power distributor is connected to one input of the kth power combiner, and the other output of the kth variable power distributor is connected to the (k + 1) th power combiner. The (N-1) input N output pre-circuits, the array of N phase shifters, and the N input N output Butler matrix, which are configured to be respectively connected to the other input of A multi-beam antenna feeding circuit characterized by being configured. 2. A one-input, two-output variable power divider (N-
2) (N is a positive integer) array and an array of (N-1) power combiners with 2 inputs and 1 output, and the k-th (1≤k≤N-2, k is positive) Integer) of the input port
Connected to the k-th variable power divider, the signal is divided into two with an arbitrary branching ratio while maintaining the in-phase relationship between the output signals,
One output of the k-th variable power divider is connected to one input of the k-th power combiner, and the other output of the k-th variable power divider is connected to the (k + 1) -th power combiner. A first pre-circuit of (N-2) input (N-1) output, each connected to the other input; and (N-1) array of 1-input 2-output power dividers. When,
Consisting of an array of N power combiners with 2 inputs and 1 output,
The k′-th (1 ≦ k ′ ≦ N−1, k ′ is a positive integer) input port is connected to the k′-th power distributor, and the k′-th power distributor is connected.
One output of the th power divider is connected to one input of the k'th power combiner, and the other output of the k'th power divider is connected to the (k '+ 1) th power combiner. A second pre-circuit of (N-1) input N output, each array connected to the other input of the converter, an array of N phase shifters, and a Butler matrix of N input N outputs, A multi-beam antenna feeding circuit characterized by being connected in cascade. 3. The first 90 ° hybrid, wherein the variable power distributor distributes and outputs a high frequency signal with equal signal strength,
The multi according to claim 1 or claim 2, which is composed of a second 90 ° hybrid which combines a signal distributed and output from the first 90 ° hybrid with a signal passing through a variable phase shifter and a signal not passing through the variable phase shifter. Beam antenna feeding circuit. 4. The Wilkinson power distributor, wherein the variable power distributor distributes and outputs an input high frequency signal in equal parts and in phase, and a variable phase shifter for a signal distributed and output from the Wilkinson power distributor. 3. The multi-beam antenna feeding circuit according to claim 1, wherein the multi-beam antenna feeding circuit comprises a 90.degree. Hybrid that combines the generated signal and a signal through a 90.degree. Phase shifter.