JPH06276017A - Antenna feeding circuit - Google Patents

Abstract

PURPOSE:To form multi-beam constitution in which respective antenna beams correspond to plural high frequency signals one to one by using spatial light signal processing technique by preparing plural light sources which output laser lights differing in frequency and performing spatial optical modulating operation and high frequency signal superposing operation corresponding to antenna beam patterns by optical frequency multiplexing. CONSTITUTION:The respective laser lights of angular frequencies omegaL1-3wL which are outputted by the laser light sources 411-41n are distributed to two paths respectively by optical distributors 561-56n. A spatial optical modulating device 11 inputs respective laser lights of one path, performs spatial modulation and light frequency multiplexing corresponding to an antenna beam pattern, and outputs the result. Further, a laser light modulating device 12 imposes time modulation for superposing corresponding high frequency signals on the laser lights of the other distribution path, performs the frequency multiplexing of the respective modulated signal lights, and outputs the result. The lights of those two paths are multiplexed by an optical multiplexer 59 and guided to a light-electricity converter array 52 through an optical fiber bundle 48 corresponding to respective radiation elements 55 of an array antenna.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array antenna feeding circuit for forming an antenna beam pattern by using a spatial optical signal processing technique, and using the same technique, the array antenna is made to function as a multi-beam antenna. Regarding the circuit.

[0002]

2. Description of the Related Art An array antenna can form a predetermined antenna beam pattern by setting the amplitude and phase of a high frequency signal for each radiating element. The antenna beam pattern is represented as a spatial Fourier transform of the electric field distribution given to the antenna aperture. Therefore, the antenna beam pattern can be realized by performing inverse Fourier transform on the required antenna beam pattern and feeding a high-frequency signal having the amplitude and phase obtained therefrom to each radiating element.

The feeding circuit of the array antenna is a circuit for setting the amplitude and phase of the high frequency signal given to each radiating element, and since the antenna beam pattern is formed according to the setting, it is also called an antenna beam forming circuit. There is. Various proposals have been made for its configuration method, but in recent years, there has been proposed an array antenna feeding circuit using a spatial optical signal processing technique (LPAnderson,
F. Boldissar, DCDChang, "Phased array antenna be
amforming using optical processor ", proc.of AIAA '
92, pp. 1279-1288, Washinton DC, March 1992). This is to set the amplitude and phase of a high frequency signal corresponding to the antenna beam pattern by using a lens or other optical system.

That is, since the lens has a Fourier transform function, a Fourier transform image corresponding to the mask pattern can be obtained by preparing a mask pattern corresponding to the antenna beam pattern and passing it through the lens. An antenna beam pattern corresponding to the mask pattern can be realized by applying a high frequency signal having an amplitude and a phase according to the Fourier transform image to each radiating element.
An antenna feeding circuit based on such a principle is hereinafter referred to as "spatial optical signal processing type antenna beam forming circuit".

FIG. 4 is a block diagram showing a configuration example of a spatial light signal processing type antenna beam forming circuit. The configuration shown here is an application of a Mach-Zehnder interferometer.

In the figure, the laser light output from the laser light source 41 passes through the pinhole mask 42 ₁ and the collimating lens 43 ₁ to become parallel light, and the half mirror 44
_It is divided into two paths by ₁ and used for spatial modulation according to the antenna beam pattern and temporal modulation for superimposing a high frequency signal to be transmitted.

One of the laser beams distributed by the half mirror 44 ₁ is reflected by the half mirror 44 ₂ and projected on the reflective spatial light modulator 45. On the reflective spatial light modulator 45, the shape of the antenna beam pattern to be realized is drawn. The amplitude of the projected laser light is spatially modulated and reflected accordingly. The modulated laser light is
The light enters the lens array 47 via the Fourier transform lens 46 and the half mirror 44 ₃ and is guided to a plurality of optical transmission lines (optical fiber bundles) 48. At this time, the reflective spatial light modulator 45 is arranged on the front focal plane of the Fourier transform lens 46,
The lens array 47 is arranged on the back focal plane, and the Fourier transform image of the antenna beam pattern drawn on the reflective spatial light modulator 45 is the position of the lens array 47 (Fourier transform surface).
Can be obtained.

The other laser beam distributed by the half mirror 44 ₁ is focused via a collimator lens 43 ₂ and input to an optical frequency shifter 49. Optical frequency shifter 49
Has a function of shifting the frequency of the input light by the frequency of the high-frequency signal input from the high-frequency signal input terminal 50 and outputting. The signal light output from the optical frequency shifter 49 is transmitted from the pinhole mask 42 ₂ to the collimator lens 43.
_It is returned to parallel light through ₃ and is reflected by the mirror 51 to be applied to the half mirror 44 ₃ .

The lights of these two paths are combined by a half mirror 44 ₃ and both are transmitted from the lens array 47 to a plurality of optical transmission paths 4.
8 to the optical / electrical converter array (O / E) 52. The output of the optical / electrical converter array 52 is
The optical beat signal of the path is obtained. This beat signal is
It has the same frequency as the high-frequency signal input from the high-frequency signal input terminal 50, and has amplitude and phase information corresponding to the antenna beam pattern.

The beat signals output from the optical / electrical converter array 52 to the high frequency transmission line 53 are amplified by the high frequency amplifier module 54 and radiated from the respective radiating elements 55. The high frequency signal supplied to each radiating element 55 includes
Since the amplitude and phase information corresponding to the antenna beam pattern is included, an antenna beam pattern similar to the figure drawn on the reflective spatial light modulator 45 is formed.

Usually, in order to form an arbitrary antenna beam pattern with an array antenna, a number of amplifiers (or attenuators) and phasers corresponding to the number of radiating elements are required.
In the above spatial light signal processing type antenna beam forming circuit,
The reflective spatial light modulator 45 has functions corresponding to these elements.
And the Fourier transform lens 46, and the number of constituent elements is significantly reduced.

FIG. 5 is a block diagram showing the principle configuration of the spatial light signal processing type antenna beam forming circuit, in which the respective units shown in FIG. 4 are grouped by function. In the figure,
The laser light source 41, the plurality of optical transmission lines 48, the high frequency signal input terminal 50, the optical / electrical converter array (O / E) 52, the high frequency transmission line 53, the high frequency amplifier module 54, and the radiating element 55 correspond to each other.

The light distributor 56 divides the laser light output from the laser light source 41 into two paths by a half mirror 44 ₁
Corresponding to. The spatial light modulator 57 corresponds to a reflective spatial light modulator 45 that spatially modulates laser light in accordance with an antenna beam pattern, a Fourier transform lens 46, and a spatial transmission path to the front and back focal planes thereof, Further, the function of the lens array 47 is also included. The laser light modulator 58 is
It corresponds to an optical frequency shifter 49 that superimposes a high frequency signal to be transmitted on the laser light. The optical combiner 59 that combines the two modulated signal lights corresponds to the half mirror 44 ₃ arranged between the Fourier transform lens 46 and the lens array 47. Further, the optical transmission lines 60 _{1 to} 60 ₄ connecting the respective parts correspond to the spatial optical transmission lines formed by using a collimator lens or the like in FIG.

By the way, if the laser light input to the spatial light modulator 57 and the laser light modulator 58 are coherent with each other, they need not necessarily come from the same light source as shown in FIGS. Note that the coherence shown here means temporal coherence, and can be easily realized by using another light source. The configuration of the spatial light signal processing type antenna beam forming circuit based on this principle is
References (Konishi, Nakajo, Fujise, “Excitation distribution and radiation characteristics of optically controlled array antenna”, IEICE technical report A-P90
-102, RCS90-32, 1990).

[0015]

The spatial light signal processing type antenna beam forming circuit shown in FIGS. 4 and 5 is for a single beam.

On the other hand, when the array antenna is used as a multi-beam antenna, a high-frequency signal to be transmitted is associated with each antenna beam in the power feeding circuit, but it is electrically processed.

The present invention can form a multi-beam in which a plurality of high-frequency signals and each antenna beam have a one-to-one correspondence by using a technique of forming an antenna beam pattern by using a spatial optical signal processing technique. It is an object of the present invention to provide an antenna feeding circuit that can be used.

[0018]

According to a first aspect of the present invention, there are provided a plurality of laser light sources for outputting laser beams of different frequencies, an optical distributor for distributing the laser beams of each frequency into two paths, respectively. For the laser light of each frequency distributed to the path of, the spatial light modulator that collectively performs spatial modulation according to the antenna beam pattern, and for the laser light of each frequency distributed to the other path Then, the laser light modulators that perform temporal modulation by superimposing the corresponding high-frequency signals, and optical-frequency-multiplex each modulated signal light, and combine the signal light generated by each modulator, Optical multiplexer that outputs to each radiating element of the antenna, and optical / electrical that converts the signal light corresponding to each radiating element into an electric signal and extracts the high frequency signal corresponding to each antenna beam and supplies it to each radiating element. Strange And a vessel.

According to a second aspect of the present invention, instead of dividing the laser light of each frequency output from a plurality of laser light sources into two paths by using an optical distributor, the laser light of each frequency has a coherent relationship. Two sets of a plurality of laser light sources configured as described above are prepared and supplied to the spatial light modulator and the laser light modulator, respectively. This configuration is similar to that described in claim 1.

[0020]

FIG. 1 is a block diagram showing the principle configuration of the antenna feeding circuit according to the first aspect.

The configuration shown here is a general one that forms n antenna beams (multi-beams). There are n laser light sources with different oscillation frequencies and n high-frequency signals assigned to each antenna beam. It is prepared.

In the figure, the angular frequency (hereinafter referred to as "frequency") ω _L1 output from the laser light sources 41 _{1 to} 41 _n
Each of the laser lights of ˜ω _Ln is divided into two paths by the light distributors 56 _{1 to} 56 _n . The spatial light modulator 11 inputs each one of the laser beams, performs spatial modulation and optical frequency multiplexing according to the antenna beam pattern, and outputs the result.

Further, the laser light modulator 12 performs temporal modulation by superimposing a corresponding high frequency signal (frequency ω _{RF1 to} ω _RFn ) on each of the other distributed laser lights to obtain each modulation signal. Light is frequency-multiplexed and output.
Here, for each of the other laser lights to which the respective optical frequency shifters 49 ₁ to 49 _n are distributed, a high frequency signal input terminal 50
₁ to 50 _n perform temporal modulation according to the high-frequency signal of frequency ω _RF1 ~ω _RFn input from, respectively (omega _L1 +
ω _RF1 ) to (ω _Ln + ω _RFn ) are converted into signal light having frequency components. The optical multiplexer 13 optical-frequency multiplexes the respective signal lights and outputs them.

The lights of the two paths are combined by an optical combiner 59, and are passed through a plurality of optical transmission lines (optical fiber bundles) 48 corresponding to the respective radiating elements 55, and an optical / electrical converter array (O /
E) is led to 52. At this time, 2n number of signal lights having different frequencies are input to the optical / electrical converter array 52.

Since the optical / electrical converter array 52 includes a photodetector having a square characteristic as an input / output characteristic as a constituent element, in principle, the sum of frequencies of all input 2n signal lights is summed up. And outputs a signal (beat signal) having a frequency component that is different from. In this beat signal, the interference between the light beams spatially modulated with respect to the antenna beam pattern, the interference between the light beams superposed with a high frequency signal,
There is interference between the two light beams, i = 1, 2, respectively.
..., n, j = 1,2, ..., When n, it can be expressed as _{ω Li ± ω Lj (ω Li} + ω RFi) ± (ω Lj + ω RFj) (ω Li + ω RFi) ± ω Lj. Among them, in a combination of (ω _Li + ω _RFi ) −ω _Lj, a signal having a frequency component when i = j, that is, a frequency ω _RFi (i = 1, 2, ..., N)
Only the n high-frequency signals are output from the optical / electrical converter array 52.

The n high-frequency signals thus obtained are input to the high-frequency amplifier module 54 via the high-frequency transmission path 53, amplified there and radiated from the corresponding radiating elements 55. The n high-frequency signals have an amplitude and a phase according to the shape of the antenna beam pattern, and each input high-frequency signal is assigned to the corresponding antenna beam (spot beam).

By the way, a laser light modulator 12 for superposing a high frequency signal on the laser light input to the spatial light modulator 11 for forming a Fourier transform image of the antenna beam pattern.
The laser light entering the must be coherent. In the above configuration, a plurality of laser light sources 41 _{1 to} 41 _n that output laser light of different frequencies ω _{L1 to} ω _Ln are prepared, and the laser light of each frequency is divided into two and coherent two.
The system laser light is generated.

As shown in FIG. 2, the antenna feeding circuit according to a second aspect of the invention has a plurality of laser light sources 41 _{11 to} 41 _1n for outputting laser light of different frequencies ω _{L1 to} ω _Ln , and a plurality of lasers similar to those. The light sources 41 _{21 to} 41 _2n are prepared, and the control circuit 21
_The oscillation frequency and phase are controlled by _{1 to} 21 _n so that the laser beams of each frequency become coherent. This makes it possible to obtain the same light as the two laser lights obtained by distributing the light from one light source. Others are claim 1.
Functions similar to those described in. For coherent control between the two laser light sources, for example, a well-known phase locked loop (PLL) technique that heterodyne-detects both laser lights to control the phase error can be used.

[0029]

FIG. 3 is a block diagram showing the configuration of an embodiment of the antenna feeding circuit according to the first aspect. The configuration of the present embodiment corresponds to the principle configuration shown in FIG.
Further, in the present embodiment, it is assumed that the multi-beam antenna covers the service area with three circular spot beams, but it is also possible to expand to more than three beams.

In the figure, the laser lights of frequencies ω _{L1 to} ω _L3 output from the laser light sources 41 _{1 to} 41 ₃ pass through the collimating lenses 43 ₁₁ to 43 ₁₃ to become parallel lights, and the half mirrors 44 _{11 to} 44 44. It is divided into 2 routes by ₁₃ .

One of the three laser beams distributed by the half mirrors 44 _{11 to} 44 ₁₃ passes through the mask pattern 31, enters the lens array 47 through the Fourier transform lens 46 and the half mirror 44 ₃ , and is optical frequency multiplexed. It is converted to a plurality of optical transmission lines (optical fiber bundles) 48 and guided. The mask pattern 31 has three pinholes corresponding to each laser beam and an antenna beam (spot beam), and is arranged on the front focal plane of the Fourier transform lens 46. After that, the lens array 47 is arranged on the focal plane, and the Fourier transform image corresponding to the mask pattern 31 is obtained at the position of the lens array 47 (Fourier transform plane).

The other 3 laser beam distributed by the half mirror 44 _{11-44 13,} reflected by the mirror 51 ₁ is focused through a collimating lens 43 _{21-43 23,} respectively optical frequency shifter 49 _{1-49 3} Entered in. Each of the optical frequency shifters 49 ₁ to 49 ₃ has a function of shifting the frequency of the input light by the frequency of the high frequency signal input from the high frequency signal input terminals 50 ₁ to 50 ₃ and outputting it. The signal lights output from the optical frequency shifters 49 ₁ to 49 ₃ are
The optical frequency is multiplexed by the optical multiplexer 13, and the half mirror 44 ₃ is irradiated with the light through the collimator lens 43 ₃ , the pinhole 42 ₂ , the mirror 51 ₂ , and the collimator lens 43 ₄ .

The light in the optical frequency multiplexed two paths are multiplexed by the half mirror 44 _3, both the lens array 47
From a plurality of optical transmission lines 48 to an optical / electrical converter array (O / E) 52. Optical / electrical converter array 5
At the output of 2, the optical frequency multiplexed optical beat signal of two paths is obtained. This beat signal has the same frequency as each high frequency signal input from the high frequency signal input terminals 50 ₁ to 50 ₃ , and also has amplitude and phase information corresponding to the Fourier transform of the antenna beam pattern. light/
The beat signals output from the electric converter array 52 to the high frequency transmission line 53 are respectively generated by the high frequency amplifier module 54.
Is amplified by and is radiated from each radiating element 55. At this time, each of the input high frequency signals is assigned to an antenna beam (spot beam) corresponding to the mask pattern 31.

The Fourier transform image forming process corresponding to the antenna beam pattern in the mask pattern 31, the Fourier transform lens 46 and the lens array 47 corresponding to the spatial light modulator 11 shown in FIG. 1 will be described below.

[0035] The coordinate system in the Fourier transform plane at a position of the lens array 47 (f _x, f _y) When the laser beam output from the laser light sources 41 ₁ to 41 _n is the Fourier transform plane,

[0036]

[Equation 1]

[0037] However, the subscript k corresponds to the laser light output from the k-th laser light source 41 _k , n is the number of laser light sources, and n = 3 in this embodiment. ω _k
And φ _{a, k} are the frequency and phase of the laser light output from the laser light source 41 _k , respectively. a _k (f _x , f _y )
And ψ (f _x , f _y ) are the amplitude component and phase component of the Fourier transform image formed by the laser light output from the laser light source 41 _k , respectively. This equation (1) shows that the Fourier transform of a plurality of laser beams can be collectively performed by one lens.

Next, the state of each laser beam on which the corresponding high frequency signal is superimposed on the Fourier transform plane will be described. The frequency of each high-frequency signal is ω
Only _RF1 , ω _RF2 , and ω _RF3 are shifted, and the optical frequency is multiplexed by the optical multiplexer 13 to reach the Fourier transform plane. This signal light is the Fourier transform plane,

[0039]

[Equation 2]

It becomes However, b _k is a constant and φ
_{b and k} are phase lengths of the optical path for the laser light output from the laser light source 41 _k . The image that appears on the Fourier transform plane is
The two signal lights shown in the equations (1) and (2) are superposed, and the brightness and phase distribution of each part of the signal light reach the optical / electrical converter array 52 as they are through the plurality of optical transmission lines 58. To do.

Since each photodetector of the optical / electrical converter array 52 has a square characteristic, for each input signal light,

[0042]

[Equation 3]

Is output. Among these, as a signal (beat signal) of a frequency component corresponding to the difference between the frequencies ω _k and (ω _k + ω _RFk ) of the signal light of the two paths, a _k (f _x , f _y ) · b _k · cos {ω _RFk t + ψ (f _x , f _y ) + (φ _{a, k} −φ _{b, k} )} (4) is taken out. Here, k is 1, 2, ..., N (3 in this embodiment). The n signals are signals in a high frequency band and have a frequency ω _RFk , and amplitude information a _k (f _x , f _y ) and phase information ψ (f _x , f _y ) corresponding to the antenna beam pattern.
have.

The high frequency amplifier module 5 outputs these signals.
If amplified by 4 and supplied to each radiating element 55, the frequency ω
N multi-beams are formed to which high-frequency signals _RF1 , ω _RF2 , ..., ω _RFn are respectively assigned.

[0045]

As described above, according to the present invention, a plurality of laser light sources for outputting laser light having different frequencies are prepared,
By performing the spatial light modulation operation corresponding to the antenna beam pattern and the high frequency signal superposition operation by optical frequency multiplexing, the conventional spatial light signal processing type antenna beam forming circuit can be used for multi-beam formation.

That is, in the antenna feeding circuit according to the present invention, one Mach-Zedder interferometer is used by optical frequency multiplexing to form a multi-beam in which a plurality of high-frequency signals and each antenna beam correspond one-to-one. The array antenna can function as a multi-beam antenna.

[Brief description of drawings]

FIG. 1 is a block diagram showing a principle configuration of an antenna feeding circuit according to claim 1.

FIG. 2 is a block diagram showing the basic configuration of the antenna feeding circuit according to claim 2;

FIG. 3 is a block diagram showing the configuration of an embodiment of the antenna feeding circuit according to claim 1;

FIG. 4 is a block diagram showing a configuration example of a spatial light signal processing type antenna beam forming circuit.

FIG. 5 is a block diagram showing a principle configuration of a spatial light signal processing type antenna beam forming circuit.

[Explanation of Codes] 11,57 Spatial light modulator 12,58 Laser light modulator 13 Optical multiplexer 21 Controller 31 Mask pattern 41 Laser light source 42 Pinhole mask 43 Collimator lens 44 Half mirror 45 Reflective spatial light modulator 46 Fourier Conversion lens 47 Lens array 48 Multiple optical transmission lines 49 Optical frequency shifter 50 High frequency signal input terminal 51 Mirror 52 Optical / electrical converter (O / E) 53 High frequency transmission line 54 High frequency amplifier module 55 Radiating element 56 Optical distributor 59 Optical combination Wave device 60 Optical transmission line

Claims (2)

[Claims] 1. A plurality of laser light sources for outputting laser light of different frequencies, an optical distributor for distributing laser light of each frequency into two paths, and a laser light of each frequency distributed to one path. hand,
Spatial light modulator that collectively performs spatial modulation according to the antenna beam pattern, and laser light of each frequency distributed to the other path,
Laser light modulators that perform temporal modulation by superimposing corresponding high-frequency signals and output each modulated signal light by optical frequency multiplexing are combined with the signal light generated by each modulator, An optical multiplexer that outputs for each radiating element, and an optical / electrical device that converts the signal light corresponding to each radiating element into an electric signal and extracts a high frequency signal corresponding to each antenna beam to supply to each radiating element. An antenna feeding circuit comprising a converter. 2. A first plurality of laser light sources that output laser light of different frequencies, and a laser light that has a coherent relationship with the laser light of each frequency output from the first plurality of laser light sources. A plurality of second laser light sources, and a spatial light modulator that collectively performs spatial modulation according to an antenna beam pattern on the laser light of each frequency output from the first plurality of laser light sources. And temporally modulating the respective high frequency signals with respect to the laser light of each frequency output from the second plurality of laser light sources, and optical-frequency-multiplexing each modulated signal light to output. A laser light modulator, an optical multiplexer that multiplexes the signal light generated by each modulator and outputs the multiplexed light to each radiating element of the array antenna, and a signal light corresponding to each radiating element is supplied to each. Antenna feeding circuit, characterized in that into a signal, and a respective antenna beam to the extracts corresponding high frequency signals each radiating element to supply light / electrical converter.