Transmission directivity control device and transmission directivity control method

Abstract

Provided is a transmission directivity control device comprising: a first axis phase slope imparting unit that imparts a phase slope on a first axis to an optical signal, the first axis being an axis in the space; wavelength change units which change the wavelength of the optical signal, to which the phase slope is imparted, to different wavelengths, respectively; a multiplexer that multiplexes the optical signals having the changed wavelengths; a second axis phase slope imparting unit that imparts a phase slope on a second axis to the multiplexed optical signal, the second axis being orthogonal to the first axis; and demultiplexers that demultiplex the optical signal to which the phase slope on the second axis is imparted into optical signals of the different wavelengths.

Description

Technical Field

[0001] The present invention relates to a transmission directivity control device and a transmission directivity control method.

Background Art

[0002] As a means to achieve high-speed and large-capacity wireless communication, the utilization of high-frequency bands above the millimeter-wave band has been progressing. Since the spatial propagation loss of radio waves increases as the frequency increases (for example, the free-space propagation loss increases in proportion to the square of the frequency), antennas with high gains are often used in such high-frequency bands. Since high-gain antennas always have high directivity, it is necessary to align the direction of the beam with the communication partner of the wireless communication. When the direction of the communication partner is dynamic, a means to dynamically control the direction of the beam, that is, the application of beam steering, becomes essential. Also, not limited to wireless communication, for example, in applications such as radar, imaging, and wireless power transmission, the implementation of beam steering in antennas is required.

[0003] As means for beam steering, methods such as mechanically controlling the azimuth of the antenna and methods of refracting or reflecting radio waves radiated from the antenna using a movable lens or mirror have been devised and used. In addition, since it does not use mechanical movable parts, phased array antennas with high durability and followability of movement and suitable for miniaturization and weight reduction of antennas are widely used.

[0004] A phased array antenna electronically performs beam steering by controlling the phase and amplitude of the RF (Radio Frequency) signal supplied to each antenna element (hereinafter, the control of the phase and amplitude is called weighting) using means such as variable delay circuits, variable attenuator circuits, and digital signal processing connected to a plurality of antenna elements arranged on a line or on a plane.

[0005] In the fifth-generation mobile communication system using the millimeter-wave band, millimeter-wave band wireless LAN (Local Area Network) systems, etc., phased array antennas of the type that perform weighting with analog circuits are often used.

[0006] In many wireless communication systems, the range where the communication partner exists changes not in a two-dimensional plane but in a three-dimensional space. Therefore, for example, beam steering in two axes such as the azimuth angle and the elevation angle is necessary. For this reason, the phased array antenna requires weighting for performing two-dimensional beam steering using a two-dimensional array antenna in which antenna elements are arranged in a plane.

[0007] For example, Non-Patent Document 1 discloses a 256-element phased array antenna used for a base station for fifth-generation mobile communication in the 28 GHz band. For example, when the radio frequency is increased by about 10 times such as 300 GHz, the propagation loss in free space becomes 100 times, and it is considered that tens of thousands of antenna elements are required.

[0008] When the radio frequency is 300 GHz, since the free space wavelength is 1 mm, it is common to set the interval between antenna elements to half of the wavelength, that is, 0.5 mm. At this time, it is difficult to install a phase shifter circuit in the vicinity of the antenna element at an interval equivalent to the interval between the antenna elements. In addition, in order to configure a circuit (multi-beam forming circuit) that forms a plurality of beams, the same number of phase shifters as the number of beams must be arranged in parallel, which is assumed to be even more difficult.

[0009] Instead of implementing a phase shifter circuit according to the number of antenna elements, there is a method of using a passive circuit having a fixed phase shift amount and switching and using its input terminals. For example, Non-Patent Document 2 discloses a method of performing two-dimensional beam steering using a passive circuit. However, it is necessary to assemble the circuit three-dimensionally, and since it is necessary to be composed of waveguides for implementation in the high-frequency band, mass production is difficult, and it is also difficult to cope with multi-element configuration.

[0010] Non-Patent Document 3 proposes a method of converting a signal into light and performing weighting using an optical circuit. As a method of performing weighting using an optical circuit, Patent Document 1 discloses a three-dimensional optical circuit that performs two-dimensional beam steering using a wavelength dispersion line. Non-Patent Document 4 discloses a method using a loop configuration that repeatedly re-uses a phase shifter while converting the optical wavelength. Non-Patent Document 5 combines a planar phase shift circuit and an FBG (fiber bragg gratings) reflection line with different delay times depending on the optical wavelength, and in addition to one-dimensional (within one plane) beam steering performed by the planar phase shift circuit, enables beam steering in a plane orthogonal to the said plane by the FBG reflection line, and discloses means for implementing two-dimensional beam steering. Patent Document 2 discloses multi-beam forming means using wavelength multiplexing.

[0011] However, in the above-disclosed devices and methods, there are drawbacks such as difficulty in manufacturing a three-dimensional structure as the frequency increases and an extremely large number of components.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0013]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0014] However, in a beam steering circuit that can be extended to two-dimensionalization and multi-elementalization, it has been difficult to support multi-beams. The present invention provides a transmission directivity control device capable of supporting multi-beams.

Means for Solving the Problem

[0015] One aspect of the present invention includes a first-axis phase tilt imparting unit that imparts a phase tilt on an optical signal on a first axis which is an axis in space, a wavelength changing unit that changes the wavelengths of a plurality of optical signals to which the phase tilt has been imparted to different wavelengths, a multiplexer that multiplexes the optical signals whose wavelengths have been changed, a second-axis phase tilt imparting unit that imparts a phase tilt on the multiplexed optical signal on a second axis perpendicular to the first axis, and a demultiplexer that demultiplexes the optical signal to which the phase tilt on the second axis has been imparted into the optical signals of the different wavelengths, and is a transmission directivity control device.

[0016] One aspect of the present invention includes a first-axis phase tilt imparting step of imparting a phase tilt on an optical signal on a first axis which is an axis in space, a wavelength changing step of changing the wavelengths of a plurality of optical signals to which the phase tilt has been imparted to different wavelengths, a multiplexing step of multiplexing the optical signals whose wavelengths have been changed, a second-axis phase tilt imparting step of imparting a phase tilt on the multiplexed optical signal on a second axis perpendicular to the first axis, and a demultiplexing step of demultiplexing the optical signal to which the phase tilt on the second axis has been imparted into the optical signals of the different wavelengths, and is a transmission directivity control method.

Effect of the Invention

[0017] The transmission directivity control device of the present invention has an advantage that it can support multi-beams.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

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Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the following embodiments.

[0020] (First Embodiment) FIG. 1 is a diagram showing a configuration example of the transmission directivity control device 1 according to the first embodiment.

[0021] The transmission directivity control device 1 includes a first-axis phase tilt imparting unit 11, a wavelength changing unit 12, a multiplexer 14, a second-axis phase tilt imparting unit 15, a demultiplexer 16, a light source 17, an optical modulator 18, and a control unit 19. The transmission directivity control device 1 includes three wavelength changing units 12-1, 12-2, and 12-3. The transmission directivity control device 1 includes three demultiplexers 16-1, 16-2, and 16-3.

[0022] The first-axis phase tilt imparting section 11 imparts a phase tilt in the first axis, which is a certain axis in space, to the optical signal. The optical signal to which the phase tilt is imparted is generated, for example, by modulating the light output from the light source 17 by the optical modulator 18. The optical modulator 18 generates an optical signal, for example, by modulating the light output from the light source with a transmission signal. The first-axis phase tilt imparting section 11 includes a first switching switch 111 and a first-axis weighting circuit 112. The first switching switch 111 includes one input terminal and three output terminals. The first switching switch 111 outputs the optical signal input to the input terminal from any one of the three output terminals. The first-axis weighting circuit 112 includes three input terminals and three output terminals. The three output terminals of the first switching switch 111 are respectively connected to the three input terminals of the first-axis weighting circuit 112. The first-axis weighting circuit 112 imparts different phase tilts to the optical signal depending on the terminal to which the optical signal is input. For example, when an optical signal is input to the first input terminal, the first-axis weighting circuit 112 imparts a phase tilt φ H1 ; when input to the second input terminal, it imparts a phase tilt φ H2 ; when input to the third terminal, it imparts a phase tilt φ H3 and outputs from the three output terminals. For example, when an optical signal is input to the first input terminal, the first-axis weighting circuit 112 outputs an optical signal with no phase imparted from the first output terminal, an optical signal with a phase φ H1 imparted from the second output terminal, and an optical signal with a phase 2φ H1 imparted from the third output terminal. For example, when an optical signal is input to the second input terminal, the first-axis weighting circuit 112 outputs an optical signal with no phase imparted from the first output terminal, an optical signal with a phase φ H2 imparted from the second output terminal, and an optical signal with a phase 2φ H2 imparted from the third output terminal. For example, when an optical signal is input to the third input terminal, the first-axis weighting circuit 112 outputs an optical signal with no phase imparted from the first output terminal, an optical signal with a phase φ H3 imparted from the second output terminal, and an optical signal with a phase 2φ H3 imparted from the third output terminal. That is, to the optical signal input to the first input terminal, 0, φ H1, 2φ H1 is given a phase tilt of, and the optical signals input to the second input terminal are 0, φ H2 , 2φ H2 is given a phase tilt of, and the optical signals input to the third input terminal are 0, φ H3 , 2φ H3 is given a phase tilt of. More specifically, the phase tilt is 0 degrees, 45 degrees, 90 degrees, or 0 degrees, 90 degrees, 180 degrees, etc. The first-axis weighting circuit 112 does not need to output an optical signal without applying a phase. For example, the phase tilt to be applied may be φ, 2φ, 3φ. In the following description, let the wavelength of the optical signal to which the phase tilt is applied be λ0.

[0023] The wavelength changer 12 changes the wavelength of the optical signal to which the phase tilt is applied by the first-axis phase tilt applying unit 11 to a different wavelength. The optical signal to which the phase tilt is applied by the first-axis phase tilt applying unit 11 and output from the first output terminal is input to the wavelength changer 12-1, the optical signal output from the second output terminal is input to the wavelength changer 12-2, and the optical signal output from the third output terminal is input to the wavelength changer 12-3. The wavelength changers 12-1, 12-2, and 12-3 change the wavelengths of the input optical signals to different wavelengths. For example, the wavelength changer 12-1 changes the wavelength of the optical signal to λ1, the wavelength changer 12-2 changes the wavelength of the optical signal to λ2, and the wavelength changer 12-3 changes the wavelength of the optical signal to λ3. The wavelength changer 12 changes the wavelength of the input optical signal based on, for example, a signal input from a local oscillator.

[0024] The multiplexer 14 multiplexes a plurality of optical signals whose wavelengths are changed by the wavelength changer 12. For example, it multiplexes the optical signal whose wavelength is changed to λ1 by the wavelength changer 12-1, the optical signal whose wavelength is changed to λ2 by the wavelength changer 12-2, and the optical signal whose wavelength is changed to λ3 by the wavelength changer 12-3. The multiplexer 14 is, for example, an AWG (Arrayed Waveguide Grating).

[0025] The second-axis phase tilt imparting section 15 imparts a phase tilt on the optical signal multiplexed by the multiplexer 14 on a second axis which is a certain axis in space. The second axis is an axis perpendicular to the first axis. The first axis and the second axis are, for example, horizontal and vertical.

[0026] The second-axis phase tilt imparting section 15 includes a second switching switch 151 and a second-axis weighting circuit 152. The second switching switch 151 includes one input terminal and three output terminals. The second switching switch 151 outputs the optical signal input to the input terminal from any one of the three output terminals. The second-axis weighting circuit 152 includes three input terminals and three output terminals. The three output terminals of the second switching switch 151 are respectively connected to the three input terminals of the second-axis weighting circuit 152. The second-axis weighting circuit 152 imparts different phase tilts to the optical signal according to the terminal to which the optical signal is input. For example, the second-axis weighting circuit 152 imparts a phase tilt φ v1 to the optical signal input to the first input terminal, a phase tilt φ v2 when input to the second input terminal, and a phase tilt φ v3 when input to the third input terminal, and outputs from the three output terminals. For example, when an optical signal is input to the first input terminal, the second-axis weighting circuit 152 outputs an optical signal without a phase imparted from the first output terminal, an optical signal with a phase φ V1 imparted from the second output terminal, and an optical signal with a phase 2φ V1 imparted from the third output terminal. For example, when an optical signal is input to the second input terminal, the second-axis weighting circuit 152 outputs an optical signal without a phase imparted from the first output terminal, an optical signal with a phase φ V2 imparted from the second output terminal, and an optical signal with a phase 2φ V2 imparted from the third output terminal. For example, when an optical signal is input to the third input terminal, the second-axis weighting circuit 152 outputs an optical signal without a phase imparted from the first output terminal, an optical signal with a phase φ V3 imparted from the second output terminal, and an optical signal with a phase 2φ V3 imparted from the third output terminal. That is, for the optical signal input to the first input terminal, 0, φ V1 , 2φV1 such a phase tilt is imparted, and for the optical signal input to the second input terminal, there are 0, φ V2 , 2φ V2 such a phase tilt is imparted, and for the optical signal input to the third input terminal, there are 0, φ V3 , 2φ V3 such a phase tilt is imparted. More specifically, the phase tilt is 0 degrees, 45 degrees, 90 degrees, or 0 degrees, 90 degrees, 180 degrees, etc. The second-axis weighting circuit 152 does not necessarily need to output an optical signal without imparting a phase. For example, the phase tilt to be imparted may be φ, 2φ, 3φ.

[0027] The first-axis weighting circuit 112 and the second-axis weighting circuit 152 impart a phase tilt to the optical signal by means of a delay line, a high-dispersion line, a resonant ring, a matrix circuit, etc. The matrix circuit is, for example, a Butler Matrix or a Blass Matrix.

[0028] The demultiplexer 16 demultiplexes the optical signal imparted with a phase tilt by the second-axis phase tilt imparting section 15 for each wavelength. The demultiplexer 16 demultiplexes the optical signal into optical signals of wavelength λ1, wavelength λ2, and wavelength λ3, for example. The demultiplexer 16 is, for example, an AWG. The demultiplexed optical signal is converted into an RF signal by, for example, a photodiode and radiated into space by an antenna.

[0029] The control unit 19 controls the first switching switch 111 and the second switching switch 151, and changes the output terminal to which the optical signal input to the input terminal of the first switching switch 111 is output and the output terminal to which the optical signal input to the input terminal of the second switching switch 151 is output.

[0030] FIG. 2 is a flowchart showing the operation of the transmission directivity control device 1 according to the first embodiment. The optical modulator 18 generates an optical signal (step S10). The first switching switch 111 outputs the input optical signal from any output terminal (step S11). Based on the terminal to which the optical signal is input, the first-axis weighting circuit 112 applies a phase gradient (step S12). The wavelength changing unit 12 changes the wavelength of the optical signal to which the phase gradient is applied (step S13). Thereafter, the multiplexer 14 multiplexes the wavelength-changed optical signals (step S14). The multiplexed optical signal is input to the second switching switch 151 and output from any output terminal (step S15). Thereafter, based on the terminal to which the optical signal is input, the second-axis weighting circuit 152 applies a phase gradient (step S16). The demultiplexer 16 demultiplexes the optical signal (step S17).

[0031] As described above, the transmission directivity control device 1 can perform weighting by an optical circuit and perform two-dimensional multi-beam steering. Further, even when the number of antenna elements increases, it is only necessary to change the internal configuration of the first-axis phase gradient applying unit 11 and the second-axis phase gradient applying unit 15 and increase the number of demultiplexers 16, and complexity can be suppressed.

[0032] (Second Embodiment) FIG. 3 is a diagram showing a configuration example of the transmission directivity control device 1 according to the second embodiment.

[0033] The transmission directivity control device 1 according to the second embodiment includes a phase gradient applying unit 21, a filter 23, and a multiplexer 25, different from the transmission directivity control device 1 according to the first embodiment. The transmission directivity control device 1 according to the second embodiment includes three filters 23-1, 23-2, and 23-3, and three multiplexers 25-1, 25-2, and 25-3.

[0034] Similar to the first embodiment, the first switching switch 111 outputs the optical signal input from the optical modulator 18 to the multiplexer 25 from any one of the three output terminals. The first switching switch 111 outputs the optical signal from the first output terminal to the multiplexer 25-1, from the second output terminal to the multiplexer 25-2, and from the third output terminal to the multiplexer 25-3.

[0035] The multiplexer 25 multiplexes the optical signals input from the first switching switch 111 and the second switching switch 151, and outputs the multiplexed signal to the phase tilt imparting unit 21. The multiplexer 25-1 multiplexes the optical signals input from the first output terminal of the first switching switch 111 and the first output terminal of the second switching switch 151, and outputs the multiplexed signal to the first input terminal of the phase tilt imparting unit 21. The multiplexer 25-2 multiplexes the optical signals input from the second output terminal of the first switching switch 111 and the second output terminal of the second switching switch 151, and outputs the multiplexed signal to the second input terminal of the phase tilt imparting unit 21. The multiplexer 25-3 multiplexes the optical signals input from the third output terminal of the first switching switch 111 and the third output terminal of the second switching switch 151, and outputs the multiplexed signal to the third input terminal of the phase tilt imparting unit 21.

[0036] The phase tilt imparting unit 21 selects either the first axis, which is an axis in space, or the second axis orthogonal to the first axis, and imparts a phase tilt in the selected axis to the optical signal. The first axis and the second axis are, for example, the horizontal direction and the vertical direction. The phase tilt imparting unit 21 imparts a phase tilt in the first axis to an optical signal having the same wavelength λ0 as the optical signal output from the optical modulator 18, and imparts a phase tilt in the second axis to an optical signal having a wavelength different from λ0. The phase tilt imparting unit 21 may be controlled by the control unit 19 to select whether to impart a phase tilt in the first axis or the second axis.

[0037] The phase tilt imparting unit 21 outputs an optical signal with a phase tilt to the filter 23. The phase tilt imparting unit 21, for example, imparts a phase tilt to the optical signal input to the first input terminal and outputs it to the filters 23-1, 23-2, and 23-3 from the first output terminal, the second output terminal, and the third output terminal. The phase tilt imparting unit 21, for example, imparts a phase tilt to the optical signal input to the second input terminal and outputs it to the filters 23-1, 23-2, and 23-3 from the first output terminal, the second output terminal, and the third output terminal. The phase tilt imparting unit 21, for example, imparts a phase tilt to the optical signal input to the third input terminal and outputs it to the filters 23-1, 23-2, and 23-3 from the first output terminal, the second output terminal, and the third output terminal.

[0038] The filter 23 filters the optical signal output from the phase tilt imparting unit 21. In the present embodiment, the optical signal with a phase tilt in the first axis and the optical signal with phase tilts in the first axis and the second axis have different wavelengths due to the phase tilt imparting unit 21. The filter 23 outputs the optical signal with a phase tilt in the first axis to the wavelength changing unit 12 and outputs the optical signal with phase tilts in the first axis and the second axis to the demultiplexer 16. The filter 23 is designed to separate, for example, an optical signal having the same wavelength as the wavelength λ0 of the optical signal output from the optical modulator 18 and an optical signal having a different wavelength, output the optical signal of wavelength λ0 to the wavelength changing unit 12, and output the optical signal of a different wavelength to the demultiplexer 16. For example, the filter 23-1 separates an optical signal having the same wavelength as the wavelength λ0 and an optical signal having a different wavelength, outputs the optical signal of wavelength λ0 to the wavelength changing unit 12-1, and outputs the optical signal of a different wavelength to the demultiplexer 16-1. The filter 23-2 separates an optical signal having the same wavelength as the wavelength λ0 and an optical signal having a different wavelength, outputs the optical signal of wavelength λ0 to the wavelength changing unit 12-2, and outputs the optical signal of a different wavelength to the demultiplexer 16-2. The filter 23-3 separates an optical signal having the same wavelength as the wavelength λ0 and an optical signal having a different wavelength, outputs the optical signal of wavelength λ0 to the wavelength changing unit 12-3, and outputs the optical signal of a different wavelength to the demultiplexer 16-3.

[0039] The wavelength changing unit 12 changes the wavelengths of a plurality of optical signals with wavelength λ0 having a phase tilt in the first axis input from the filter 23 to different wavelengths. For example, the wavelength changing unit 12-1 changes the wavelength of the optical signal input from the filter 23-1 to λ1, the wavelength changing unit 12-2 changes the wavelength of the optical signal input from the filter 23-2 to λ2, and the wavelength changing unit 12-3 changes the wavelength of the optical signal input from the filter 23-3 to λ3. The wavelength changing unit 12 changes the wavelength of the input optical signal based on, for example, a signal input from a local oscillator.

[0040] The multiplexer 14 multiplexes a plurality of optical signals whose wavelengths are changed by the wavelength changing unit 12.

[0041] Similar to the first embodiment, the second switching switch 151 outputs the optical signal input from the multiplexer 14 to the multiplexer 25 from any one of the three output terminals. The second switching switch 151 outputs the optical signal from the first output terminal to the multiplexer 25-1, from the second output terminal to the multiplexer 25-2, and from the third output terminal to the multiplexer 25-3.

[0042] The demultiplexer 16 demultiplexes the optical signal having a phase tilt in the first axis and the second axis input from the filter 23. For example, the demultiplexers 16-1, 16-2, and 16-3 demultiplex the optical signals having a phase tilt in the first axis and the second axis input from the filters 23-1, 23-2, and 23-3, respectively. The demultiplexed optical signal is converted into an RF signal by, for example, a photodiode and radiated into space by an antenna.

[0043] FIG. 4 is a flowchart showing the operation of the transmission directivity control device 1 according to the second embodiment. The optical modulator 18 generates an optical signal (step S20). The first switching switch 111 outputs the input optical signal from any output terminal (step S21). For the distributed optical signal, the phase tilt imparting unit 21 imparts a phase tilt on the first axis (step S22). The wavelength changing unit 12 changes the wavelength of the optical signal to which the phase tilt has been imparted (step S23). Thereafter, the multiplexer 14 multiplexes the wavelength-changed optical signals (step S24). The combined optical signal is input to the second switching switch 151 and output from any output terminal (step S25). Thereafter, for the distributed optical signal, the phase tilt imparting unit 21 imparts a phase tilt on the second axis (step S26). The demultiplexer 16 demultiplexes the optical signal (step S27).

[0044] As described above, the transmission directivity control device 1 according to the first embodiment includes two weighting circuits, while the transmission directivity control device 1 according to the second embodiment includes one weighting circuit. Therefore, the number of weighting circuits can be reduced, and a transmission directivity control device that exhibits the same effect with fewer elements can be configured.

[0045] (Third Embodiment) FIG. 5 is a diagram showing a configuration example of the transmission directivity control device 1 according to the third embodiment. The transmission directivity control device 1 according to the third embodiment includes a polarization demultiplexing unit 31 instead of the filter 23, unlike the transmission directivity control device 1 according to the second embodiment. Further, the transmission directivity control device 1 according to the third embodiment includes a polarization control unit 32 between the multiplexer 14 and the second switching switch 151, unlike the transmission directivity control device 1 according to the second embodiment.

[0046] The polarization control unit 32 rotates the polarization plane of the optical signal multiplexed by the multiplexer 14 by 90 degrees and outputs it to the second switching switch 151. The polarization beam splitter 31 splits the optical signal according to the polarization angle. Since the polarization plane of the optical signal input from the second switching switch 151 to the phase tilt imparting unit 21 is rotated by 90 degrees by the polarization control unit 32, the polarization angle is different from that of the optical signal input from the first switching switch 111 to the phase tilt imparting unit 21. Therefore, the polarization beam splitter 31 is designed to output the optical signal input from the first switching switch 111 to the phase tilt imparting unit 12 to the wavelength changing unit 12, and output the optical signal with the polarization plane rotated by 90 degrees input from the second switching switch 151 to the phase tilt imparting unit 21 to the optical demultiplexer 16.

[0047] In the second embodiment, the filter 23 splits the optical signal into the wavelength changing unit 12 and the optical demultiplexer 16 according to the wavelength difference. In the third embodiment, the filter 23 is a polarization beam splitter. Further, in the third embodiment, the polarization plane of the optical signal multiplexed by the multiplexer 14 is rotated by 90 degrees. Thereby, in the third embodiment, the optical signal can be separated according to the difference in polarization of the optical signal.

[0048] In the above embodiments, the transmission directivity control device 1 includes three optical demultiplexers 16, which split the optical signal into three wavelengths and form a 3×3 square two-dimensional array antenna, but it does not have to be square. FIG. 6 is a diagram showing a modified example of the transmission directivity control device 1 according to the first embodiment. The transmission directivity control device 1 shown in FIG. 6 includes three optical demultiplexers 16, which split the optical signal into two wavelengths and form a 3×2 two-dimensional array antenna. At this time, the first switching switch 111 only needs to have two output terminals, and does not have to include the filter 23-3, the wavelength changing unit 12-3, and the multiplexer 25-3. Further, the multiplexer 14 only needs to multiplex the optical signals input from the wavelength changing units 12-1 and 12-2, the filter 23 only needs to be able to separate λ0 and λ1 and λ2, and the optical demultiplexer 16 only needs to be able to demultiplex the optical signals of wavelengths λ1 and λ2. At this time, the number of the wavelength changing units 12 can be reduced, and the wavelengths and bands used can be saved.

[0049] (Fourth Embodiment) FIG. 7 is a diagram showing a configuration example of the transmission directivity control device 1 according to the fourth embodiment. The transmission directivity control device 1 according to the fourth embodiment is different from the transmission directivity control device 1 according to the first embodiment, and includes a long-wavelength conversion unit 41 and a short-wavelength conversion unit 42 instead of the wavelength change unit 12. Further, the transmission directivity control device 1 includes two or more light sources and an optical modulator 18, and the first switching switch 111 includes two or more input terminals.

[0050] The first switching switch 111 independently outputs the two input optical signals from one of the three output terminals. The long-wavelength conversion unit 41 is provided between the first output terminal of the first-axis weighting circuit 112 and the first input terminal of the multiplexer 14. The short-wavelength conversion unit 42 is provided between the third output terminal of the first-axis weighting circuit 112 and the third input terminal of the multiplexer 14. The long-wavelength conversion unit 41 increases the wavelength of the input optical signal and outputs it to the multiplexer 14. The short-wavelength conversion unit 42 decreases the wavelength of the input optical signal and outputs it to the multiplexer 14.

[0051] The first-axis phase tilt imparting unit 11 and the second-axis phase tilt imparting unit 15 impart different phase tilts according to the wavelength of the input optical signal. In the first-axis phase tilt imparting unit 11 and the second-axis phase tilt imparting unit 15, the correspondence between the wavelength of the input optical signal and the imparted phase tilt is set. FIG. 8 is an example of the correspondence between the wavelength of the input optical signal and the imparted phase tilt. The wavelength of the optical signal output from the optical modulator 18 is determined based on the imparted phase tilt, that is, the direction in which the signal is finally radiated by the antenna. The wavelength of the optical signal output from the optical modulator 18 changes, for example, by changing the wavelength of the light output from the light source 17. When the first-axis weighting circuit 112 and the second-axis weighting circuit 152 are matrix circuits, the first switching switch 111 and the second switching switch 151 are demultiplexers, and select the input terminals of the matrix circuit that outputs the optical signal according to the frequency of the input optical signal.

[0052] When the wavelength of the optical signal input to the first-axis phase tilt imparting section 11 is λ1, the wavelengths of the three optical signals multiplexed by the multiplexer 14 are, for example, λ1+Δ, λ1, and λ1-Δ. Here, Δ is set to a value smaller than the smallest wavelength difference in the correspondence relationship between the wavelength of the optical signal and the imparted phase tilt.

[0053] The demultiplexer 16 demultiplexes the optical signal based on the deviation from the wavelength in the correspondence relationship between the wavelength of the optical signal and the imparted phase tilt. For example, the demultiplexer 16 demultiplexes the optical signal into wavelengths of λ1+Δ, λ1, and λ1-Δ, demultiplexes the optical signal into wavelengths of λ2+Δ, λ2, and λ2-Δ, and demultiplexes the optical signal into wavelengths of λ3+Δ, λ3, and λ3-Δ.

[0054] (Fifth Embodiment) Unlike the transmission directivity control device 1 according to the first embodiment, in the transmission directivity control device 1 according to the fifth embodiment, the wavelength changing section 12-1 does not change the wavelength of the optical signal, the wavelength changing section 12-2 changes the wavelength of the optical signal in three steps in the correspondence relationship shown in FIG. 8, and the wavelength changing section 12-3 changes the wavelength of the optical signal in six steps in the correspondence relationship shown in FIG. 8. For example, the wavelength changing section 12-2 changes the optical signal of wavelength λ1 to an optical signal of wavelength λ4, changes the optical signal of wavelength λ2 to an optical signal of wavelength λ5, and changes the optical signal of wavelength λ3 to an optical signal of wavelength λ6. For example, the wavelength changing section 12-3 changes the optical signal of wavelength λ1 to an optical signal of wavelength λ7, changes the optical signal of wavelength λ2 to an optical signal of wavelength λ8, and changes the optical signal of wavelength λ3 to an optical signal of wavelength λ9. The second-axis phase tilt imparting section 15 imparts different phase tilts to the optical signal input by the multiplexed optical signal of λ1, λ4, and λ7, the multiplexed optical signal of λ2, λ5, and λ8, and the multiplexed optical signal of λ3, λ6, and λ9. The demultiplexer 16 demultiplexes the optical signal of wavelengths λ1, λ4, and λ7, demultiplexes the optical signal of wavelengths λ2, λ5, and λ8, and demultiplexes the optical signal of wavelengths λ3, λ6, and λ9. Similar to the transmission directivity control device 1 according to the fourth embodiment, the transmission directivity control device 1 according to the fifth embodiment includes two or more light sources and an optical modulator 18, and the first switching switch 111 may include two or more input terminals.

[0055] As described above, the transmission directivity control device 1 according to the fourth and fifth embodiments can transmit a plurality of signals in different directions from the antenna provided in the demultiplexer 16 based on a plurality of optical signals.

[0056] As described above, one embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the input terminals and output terminals of the first-axis phase tilt imparting unit 11, the second-axis phase tilt imparting unit 15, and the phase tilt imparting unit 21 are three, and the three demultiplexers 16 demultiplex the optical signals of three wavelengths. However, the present invention is not limited to this. For example, the input terminals and output terminals of the first-axis phase tilt imparting unit 11, the second-axis phase tilt imparting unit 15, and the phase tilt imparting unit 21 may be two or four or more. The number of demultiplexers 16 may be two or four or more. The demultiplexer 16 may demultiplex the optical signals of two wavelengths or demultiplex the optical signals of four or more wavelengths.

Explanation of Reference Numerals

[0057] 1 Transmission directivity control device, 11 First-axis phase tilt imparting unit, 111 First switching switch, 112 First-axis weighting circuit, 12 Wavelength changing unit, 14 Multiplexer, 15 Second-axis phase tilt imparting unit, 151 Second switching switch, 152 Second-axis weighting circuit, 16 Demultiplexer, 17 Light source, 18 Optical modulator, 19 Control unit, 21 Phase tilt imparting unit, 23 Filter, 25 Multiplexer, 31 Polarization demultiplexing unit, 32 Polarization control unit, 41 Long-wavelength conversion unit, 42 Short-wavelength conversion unit

Claims

1. A first-axis phase tilt imparting unit that imparts a phase tilt in a first axis, which is an axis in space, to an optical signal; A wavelength changing unit that changes the wavelengths of the optical signals to which the phase tilt has been imparted to different wavelengths respectively; A multiplexer that multiplexes the optical signals whose wavelengths have been changed; A second-axis phase tilt imparting unit that imparts a phase tilt in a second axis orthogonal to the first axis to the multiplexed optical signal; A demultiplexer that demultiplexes the optical signal to which the phase tilt in the second axis has been imparted into the optical signals of the different wavelengths; A transmission directivity control device comprising the above.

2. A phase tilt imparting unit that selects either a first axis, which is an axis in space, or a second axis orthogonal to the first axis, and imparts a phase tilt in the selected axis to an optical signal; A first switching switch that outputs an input optical signal to any one of the input terminals of the phase tilt imparting unit; A wavelength changing unit that changes the wavelengths of a plurality of optical signals to which a phase tilt in the first axis has been imparted to different wavelengths respectively; A multiplexer that multiplexes the optical signals whose wavelengths have been changed; A second switching switch that outputs the multiplexed optical signal to any one of the input terminals of the phase tilt imparting unit; A demultiplexer that demultiplexes the optical signal to which a phase tilt in the second axis has been imparted; A filter that filters an optical signal input from the phase tilt imparting unit based on wavelength between the phase tilt imparting unit and the wavelength changing unit, outputs the optical signal to which a phase tilt in the first axis has been imparted to the wavelength changing unit, and outputs the optical signal to which a phase tilt in the second axis has been imparted to the demultiplexer; A transmission directivity control device comprising the above.

3. A polarization control unit that rotates the polarization plane of the multiplexed optical signal and outputs it to the second switching switch; Instead of the filter, a polarization demultiplexing unit that polarization-demultiplexes an optical signal input from the phase tilt imparting unit, outputs the optical signal to which a phase tilt in the first axis has been imparted to the wavelength changing unit, and outputs the optical signal to which a phase tilt in the second axis has been imparted to the demultiplexer; The transmission directivity control device according to Claim 2, comprising the above.

4. The first-axis phase tilt imparting unit independently imparts a phase tilt in the first axis to a plurality of optical signals; The wavelength changing unit changes the wavelengths of the optical signals to which the phase tilt has been imparted to different wavelengths respectively for each of the plurality of optical signals; The second-axis phase tilt imparting unit imparts a phase tilt in the second axis for each of the plurality of optical signals; The transmission directivity control device according to Claim 1.

5. The wavelength changing unit includes a wavelength increasing unit that increases the wavelength of an input optical signal, and a wavelength decreasing unit that decreases the wavelength of the input optical signal. The transmission directivity control device according to claim 4.

6. A first-axis phase tilt imparting step of imparting a phase tilt on a first axis, which is an axis in space, to an optical signal; A wavelength changing step of changing the wavelengths of a plurality of optical signals to which the phase tilt has been imparted to different wavelengths; A multiplexing step of multiplexing the optical signals whose wavelengths have been changed; A second-axis phase tilt imparting step of imparting a phase tilt on a second axis, which is perpendicular to the first axis, to the multiplexed optical signal; A demultiplexing step of demultiplexing the optical signal to which the phase tilt on the second axis has been imparted into optical signals of the different wavelengths; A transmission directivity control method having the above steps.

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