Transmission directivity control device

Abstract

This transmission directivity control device comprises: a splitter that splits an optical signal into a first optical signal and a second optical signal; a first weighting unit that applies, to the first optical signal, a phase in a first axis serving as a given spatial axis; a second weighting unit that applies, to the second optical signal, a phase in a second axis orthogonal to the first axis; and a photo-mixing unit that performs photo-mixing of the first optical signal to which the phase has been applied and the second optical signal to which the phase has been applied. The splitter outputs the first optical signal to different input terminals of the first weighting unit in accordance with the wavelength of the first optical signal and outputs the second optical signal to different input terminals of the second weighting unit in accordance with the wavelength of the second optical signal. The first weighting unit applies different phases to the first optical signal in accordance with the input terminals to which input has been supplied. The second weighting unit applies different phases to the second optical signal in accordance with the input terminals to which input has been supplied.

Description

Transmission directivity control device

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

[0002] Controlling a large-scale array antenna requires complex filter structures and high-speed, large-scale switch structures to process signals at different wavelengths for each beam, making it a challenging task to achieve.

[0003] JP 2004-023400 A JP 2007-165956 A International Publication No. 2023 / 242930

[0004] H. Watanabe, S. Uga, H. Nakamizo, T. Tsutsumi, S. Shinjo, and Y. Kuriyama, “Millimeter-Wave Antenna and RF Front-End Technology for 5th Generation Mobile Communication Base Stations,” IEICE Communications Society Magazine, 2020, Vol. 14, No. 3, pp. 222-231. Dong-Hun KIM, Jiro HIROKAWA, and Makoto ANDO, “One-Body 2-D Beam-Switching Butler Matrix with Waveguide Short-Slot 2-Plane Couplers,” IEICE TRANSACTIONS on Electronics, Vol. E100-C, No. 10, pp. 884-892, 2017. C. Tsokos et al., “Analysis of a Multibeam Optical Beamforming Network Based on Blass Matrix Architecture,” in Journal of Lightwave Technology, vol. 36, no. 16, pp. 3354-3372, 15 Aug.15, 2018.Y. Liu and J. Klamkin, "Scalable Integrated Photonics Beamforming Circuits," 2020 Asia Communications and Photonics Conference (ACP) and International Conference on Information Photonics and Optical Communications (IPOC), 2020, pp. 1-3.B. Ortega, J. Mora and R. Chulia, "Optical Beamformer for 2-D Phased Array Antenna With Subarray Partitioning Capability," in IEEE Photonics Journal, vol. 8, no. 3, pp. 1-9, June 2016.

[0005] In view of the above circumstances, the present invention realizes a transmission directivity control device with a smaller configuration.

[0006] One aspect of the present invention is a transmission directivity control device comprising: a demultiplexer that demultiplexes an optical signal into a first optical signal and a second optical signal; a first weighting unit that imparts a phase on a first axis that is a certain axis in space to the first optical signal; a second weighting unit that imparts a phase on a second axis that is orthogonal to the first axis to the second optical signal; and a photomixing unit that photomixes the first optical signal to which the phase has been imparted and the second optical signal to which the phase has been imparted, wherein the demultiplexer outputs the first optical signal to different input terminals of the first weighting unit according to the wavelength of the first optical signal, and outputs the second optical signal to different input terminals of the double-weighting unit according to the wavelength of the second optical signal, the first weighting unit imparting a different phase to the first optical signal according to the input terminal to which it is input, and the double-weighting unit imparting a different phase to the second optical signal according to the input terminal to which it is input.

[0007] According to the present invention, a transmission directivity control device can be realized with a smaller configuration.

[0008] Fig. 1 is a diagram showing an example of the configuration of the transmission directivity control device 1 according to the present embodiment. Fig. 2 is a diagram showing an example of the configuration of an antenna element 171. Fig. 3 is a diagram showing an example of the configuration of the antenna element 171. Fig. 4 is a diagram showing an example of the wavelength of an optical signal input to a demultiplexer 13. Fig. 5 is a flowchart showing the operation of the transmission directivity control device 1 according to the present embodiment. Fig. 6 is a diagram showing the configuration of a comparative example of the transmission directivity control device 9.

[0009] 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.

[0010] FIG. 1 is a diagram showing an example of the configuration of a transmission directivity control device 1 according to this embodiment.

[0011] The transmission directivity control device 1 includes a light source 11, an optical modulator 12, a demultiplexer 13, a first weighting unit 16-1, a second weighting unit 16-2, a photomixing unit 17, and a control unit .

[0012] The light source 11 outputs light to the optical modulator 12. The light source 11 can change the wavelength of the light it outputs.

[0013] The optical modulator 12 generates an optical signal by modulating the input light. The demultiplexer 13 demultiplexes the optical signal input from the optical modulator 12. The demultiplexer 13 demultiplexes the optical signal into a carrier wave and a sideband wave. The demultiplexer 13 may demultiplex the optical signal into a carrier wave and an upper sideband wave, or into a carrier wave and a lower sideband wave. In the following description, the carrier wave L Ｈ is expressed as Equation (1), and the sideband wave L Ｓ is expressed by equation (2) which shows the upper sideband.

[0014]

[0015] The demultiplexer 13 demultiplexes the optical signal input from the optical modulator 12 into a carrier wave and a sideband wave, and outputs them to the first weighting unit 16-1 and the second weighting unit 16-2, respectively. The demultiplexer 13 will be described in detail later.

[0016] The first weighting unit 16-1 has three input terminals and three output terminals. The output terminals of the first changeover switch 14 correspond one-to-one to the input terminals of the first weighting unit 16-1. The three output terminals of the first changeover switch 14 are the first output terminal, the second output terminal, and the third output terminal. When the three input terminals of the first weighting unit 16-1 are the first input terminal, the second input terminal, and the third input terminal, for example, the first output terminal corresponds to the first input terminal, the second output terminal corresponds to the second input terminal, and the third output terminal corresponds to the third input terminal. In this case, a carrier wave is input from the first output terminal of the first changeover switch 14 to the first input terminal of the first weighting unit 16-1, a carrier wave is input from the second output terminal of the first changeover switch 14 to the second input terminal of the first weighting unit 16-1, and a carrier wave is input from the third output terminal of the first changeover switch 14 to the third input terminal of the first weighting unit 16-1.

[0017] The first weighting unit 16-1 assigns a phase on a first axis, which is a certain axis in space, to the carrier wave input from the first changeover switch 14, and outputs the result from all of the multiple output terminals to the photomixing unit 17. The first weighting unit 16-1 changes the phase to be assigned depending on the input terminal to which the carrier wave is input. The first weighting unit 16-1 is, for example, a delay line, a high-dispersion line, a resonant ring, or a matrix circuit. The matrix circuit is, for example, a Butler matrix or a Blass matrix.

[0018] For example, the first weighting unit 16-1 outputs carrier waves to which different phases are imparted depending on the input terminal to which the carrier wave is input from the first output terminal, the second output terminal, and the third output terminal. For example, the first weighting unit 16-1 imparts a phase slope φ to the carrier wave input to the first input terminal. first,1 and outputs an optical signal with no phase added from the first output terminal, and a phase φ first,1 and outputs the optical signal having the phase 2φ from the second output terminal. first,1 For example, the first weighting unit 16-1 applies a phase slope φ to the carrier wave input to the second input terminal and outputs the optical signal to which the phase slope φ is applied from the third output terminal. first,2 and outputs an optical signal with no phase added from the first output terminal, and a phase φ first,2 and outputs the optical signal having the phase 2φ from the second output terminal. first,2 For example, the first weighting unit 16-1 applies a phase slope φ to the carrier wave input to the third input terminal. first,3 and outputs an optical signal with no phase added from the first output terminal, and a phase φ first,3 and outputs the optical signal having the phase 2φ from the second output terminal. first,3 In the first weighting unit 16-1, when a carrier wave is input to the p-th input terminal, the phase φ is assigned to the carrier wave output from the i-th output terminal. Hip is expressed by equation (3).

[0019] In equation (3), φ first,p is the phase tilt on the first axis that is applied when a carrier wave is input to the p-th input terminal of the first weighting unit 16-1.first,p is, for example, 45 degrees or 90 degrees.

[0020] The second weighting unit 16-2 has three input terminals and three output terminals. The output terminals of the second changeover switch 15 correspond one-to-one to the input terminals of the second weighting unit 16-2. The three output terminals of the second changeover switch 15 are the first output terminal, the second output terminal, and the third output terminal. When the three input terminals of the second weighting unit 16-2 are the first input terminal, the second input terminal, and the third input terminal, for example, the first output terminal corresponds to the first input terminal, the second output terminal corresponds to the second input terminal, and the third output terminal corresponds to the third input terminal. In this case, a sideband wave is input from the first output terminal of the second changeover switch 15 to the first input terminal of the second weighting unit 16-2, a sideband wave is input from the second output terminal of the second changeover switch 15 to the second input terminal of the second weighting unit 16-2, and a sideband wave is input from the third output terminal of the second changeover switch 15 to the third input terminal of the second weighting unit 16-2.

[0021] The second weighting unit 16-2 assigns a phase on a second axis orthogonal to the first axis to the sideband waves input from the second changeover switch 15, and outputs the sideband waves from all of the multiple output terminals to the photomixing unit 17. The second weighting unit 16-2 changes the phase to be assigned depending on the input terminal to which the sideband waves are input. The second weighting unit 16-2 is, for example, a delay line, a high-dispersion line, a resonant ring, or a matrix circuit. The matrix circuit is, for example, a Butler matrix or a Blass matrix.

[0022] For example, the second weighting unit 16-2 outputs carrier waves to which different phase gradients are applied depending on the input terminal to which the sideband waves are input from the first output terminal, the second output terminal, and the third output terminal. For example, the second weighting unit 16-2 applies a phase gradient φ second,1 and outputs an optical signal with no phase added from the first output terminal, and a phase φ second,1 and outputs the optical signal having the phase 2φ from the second output terminal. second,1 For example, the second weighting unit 16-2 applies a phase slope φ to the carrier wave input to the second input terminal and outputs the optical signal to which the phase slope φ is applied from the third output terminal. second,2and outputs an optical signal with no phase added from the first output terminal, and a phase φ second,2 and outputs the optical signal having the phase 2φ from the second output terminal. second,2 For example, the second weighting unit 16-2 applies a phase slope φ to the carrier wave input to the third input terminal. second,3 and outputs an optical signal with no phase added from the first output terminal, and a phase φ second,3 and outputs the optical signal having the phase 2φ from the second output terminal. second,3 In the second weighting unit 16-2, when a sideband wave is input to the q-th input terminal, the phase φ is assigned to the sideband wave output from the j-th output terminal. Vjq is expressed by equation (4).

[0023] In equation (3), φ second,q is the phase tilt on the second axis that is applied when a carrier wave is input to the q-th input terminal of the second weighting unit 16-2. second,q is, for example, 45 degrees or 90 degrees.

[0024] The photomixing unit 17 includes a plurality of antenna elements 171. The plurality of antenna elements form a two-dimensional array antenna with three rows and three columns. The antenna element 171 located in the ith row and jth column receives the optical signal L from the ith output terminal of the first weighting unit 16-1. H,i is input, and the optical signal L is output from the j-th output terminal of the second weighting unit 16-2. S,j is input. H,i is the phase φ of equation (3) Hi is defined by equation (5) using

[0025] Optical signal L S,j is the phase φ of equation (4) Vjq is defined by equation (6) using

[0026] The antenna element 171 generates an electromagnetic wave based on the two input optical signals. The frequency of the generated electromagnetic wave is the difference between the frequencies of the two input optical signals. FIG. 2 is a diagram showing an example of the configuration of the antenna element 171. The antenna element 171 includes a multiplexer 1711, a square-law detector 1712, and an antenna 1713. The multiplexer 1711 multiplexes the carrier wave and sideband waves input from the weighting unit 16. The multiplexed optical signal is L Ｈ +L Ｓ The multiplexer 1711 is, for example, an AWG. The square-law detector 1712 converts the multiplexed optical signal into an RF signal. The square-law detector 1712 is, for example, a photodiode. The antenna 1713 outputs only components of a predetermined RF frequency band that depends on the output frequency characteristics of the square-law detector 1712. In other words, the output v from the antenna 1713 of the antenna element 171 installed in the i-th row and j-th column is ＲＦｉｊ (L Ｈ +L Ｓ ) ２ is extracted from the RF band and is proportional to equation (7).

[0027] From the above, the phase given to the output of the antenna element 171 in the i-th row and j-th column is φ Vjq -φ Hip is.

[0028] 3 is a diagram showing an example of the configuration of the antenna element 171. In the antenna element 171, a mirror 1714 may be used instead of the multiplexer 1711 to multiplex an optical signal to which a phase has been assigned by the weighting unit 16 and an optical signal to which a phase has been assigned by the weighting unit 16.

[0029] The demultiplexer 13 outputs a carrier wave to a different input terminal of the first weighting unit 16-1 according to the wavelength of the carrier wave, and outputs a sideband wave to a different input terminal of the second weighting unit 16-2 according to the wavelength of the sideband wave.

[0030] The demultiplexer 13 is, for example, an arrayed waveguide grating (AWG). The demultiplexer 13 is designed to determine to which input terminal of the first weighting unit 16-1 or the second weighting unit 16-2 the input signal is to be output, depending on the wavelength of the input optical signal and the frequency at which the input optical signal is to be output.

[0031] The control unit 18 changes the wavelength of the light output from the light source 11 and controls the direction of the beam output from the photomixing unit 17 .

[0032] 4 is a diagram showing an example of the wavelength of an optical signal input to the demultiplexer 13. The demultiplexer 13 receives the wavelength λ １ to the first input terminal of the first weighting unit 16-1, and the carrier wave of wavelength λ １ +Δλ sideband waves are output to the first input terminal of the second weighting unit 16-2, and ２ to the first input terminal of the first weighting unit 16-1, and the carrier wave of wavelength λ ２ +Δλ sideband waves are output to the second input terminal of the second weighting unit 16-2, and ３ to the first input terminal of the first weighting unit 16-1, and the carrier wave of wavelength λ ３ The second weighting unit 16-2 is designed to output a sideband wave of wavelength λ +Δλ to the third input terminal of the second weighting unit 16-2. １ Carrier wave and wavelength λ １ When a sideband wave of +Δλ is input to the branching filter 13, the phase given to the output of the antenna element 171 in the i-th row and j-th column is φ Vj1 -φ Hi1 and the wavelength λ ２ Carrier wave and wavelength λ ２ When a sideband wave of +Δλ is input to the branching filter 13, the phase given to the output of the antenna element 171 in the i-th row and j-th column is φ Vj2 -φ Hi1 and the wavelength λ ３ Carrier wave and wavelength λ ３ When a sideband wave of +Δλ is input to the branching filter 13, the phase given to the output of the antenna element 171 in the i-th row and j-th column is φ Vj3 -φ Hi1 and three beams are output in different directions.

[0033] Here, the optical signal input to the demultiplexer 13 may include multiple carrier waves and multiple sideband waves. In other words, even when light obtained by multiplexing all of the optical signals with the wavelengths shown in Figure 4 is input to the demultiplexer 13, the demultiplexer 13 can output optical signals for each wavelength to a specific input terminal of the first weighting unit 16-1 or the second weighting unit 16-2, and cause the photomixing unit 17 to output a beam in a desired direction.

[0034] 5 is a flowchart showing the operation of the transmission directivity control device 1 according to this embodiment. The control unit 18 controls the light source 11 to control the wavelength of the optical signal output from the light source 11 (step S10). Here, the control unit 18 controls the wavelength of the light output from the light source 11 in accordance with the direction of the beam output from the photomixing unit 17.

[0035] The optical modulator 12 modulates the light output from the light source 11 to generate an optical signal (step S11). The demultiplexer 13 then demultiplexes the optical signal input from the optical modulator 12 into a carrier wave and sideband waves according to their wavelengths, and outputs them to the input terminals of the first weighting unit 16-1 or the second weighting unit 16-2 according to their wavelengths (step S12). The first weighting unit 16-1 assigns a phase on the first axis to the carrier wave (step S13-1). The second weighting unit 16-2 assigns a phase on the second axis to the sideband waves (step S13-2). The first weighting unit 16-1 assigns a phase to the carrier wave according to the input terminal to which the carrier wave is input, and the second weighting unit 16-2 assigns a phase to the sideband waves according to the input terminal to which the sideband waves are input. The photomixing unit 17 photomixes the carrier wave and sideband waves in each antenna element 171 (step S14). The photomixed optical signal is output as an RF signal from an antenna 1713 .

[0036] (Comparative Example) Fig. 6 is a diagram showing the configuration of a comparative example of the transmission directivity control device 9. The transmission directivity control device 9 shown in Fig. 6 includes a light source 91, an optical modulator 92, a demultiplexer 93, a first changeover switch 94, a second changeover switch 95, a first weighting unit 96-1, a second weighting unit 96-2, a photomixing unit 97, and a control unit 98.

[0037] The demultiplexer 93 demultiplexes the optical signal input from the optical modulator 92 into a carrier wave and sideband waves. The first changeover switch 94 has three output terminals, and outputs the carrier wave from one of the output terminals to the first weighting unit 96-1. The output terminals of the first changeover switch 94 and the input terminals of the first weighting unit 96-1 correspond one-to-one, and the first changeover switch 94 outputs the carrier wave to the input terminal of the first weighting unit 96-1 that corresponds to its output terminal.

[0038] The second changeover switch 95 has three output terminals, and outputs the sideband waves from any one of the output terminals to the second weighting unit 96-2. The output terminals of the second changeover switch 95 correspond one-to-one to the input terminals of the second weighting unit 96-2, and the second changeover switch 95 outputs the sideband waves to the input terminal of the second weighting unit 96-2 that corresponds to the output terminal.

[0039] The control unit 98 controls the first changeover switch 94 and the second changeover switch 95, controls which output terminal of the first changeover switch 94 the carrier wave is output from, and controls which output terminal of the second changeover switch 95 the sideband wave is output from.

[0040] The light source 91, the optical modulator 92, the first weighting unit 96-1, the second weighting unit 96-2, and the photomixing unit 97 are equivalent to the light source 11, the optical modulator 12, the first weighting unit 16-1, the second weighting unit 16-2, and the photomixing unit 17 of this embodiment.

[0041] Comparing the transmission directivity control device 1 according to this embodiment with the transmission directivity control device 9, which is a comparative example, the transmission directivity control device 9 includes a first changeover switch 94 and a second changeover switch 95, while the transmission directivity control device 1 does not include a changeover switch. This makes it possible to omit the changeover switch configuration in this embodiment. The demultiplexer 13 in the transmission directivity control device 1 needs to demultiplex more wavelengths of light than the demultiplexer 93 in the transmission directivity control device 9, but the resulting increase in the size of the demultiplexer is smaller than the scale of the changeover switch. As a result, this embodiment achieves a transmission directivity control device with a smaller configuration.

[0042] One embodiment of the present invention has been described in detail above with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes and the like are possible within the scope that does not deviate from the gist of the present invention.

[0043] The first weighting unit 16-1 and the second weighting unit 16-2 each have three input terminals and three output terminals, and the array antenna included in the photomixing unit 17 has antenna elements 171 arranged in three rows and three columns, but this is not limited to this. For example, the array antenna may have two rows, four or more rows, or two or four or more columns. Furthermore, the array antenna does not have to be configured with square antenna elements 171, such as three rows and three columns or four rows and four columns. The input terminals and output terminals of the first weighting unit 16-1 and the second weighting unit 16-2 may vary depending on the number of rows and columns of antenna elements 171 included in the array antenna.

[0044] In the above-described embodiment, the demultiplexer 13 first demultiplexes the optical signal into a carrier wave and sideband waves, but this is not limited thereto and the demultiplexer 13 may demultiplex the optical signal into a first optical signal and a second optical signal. For example, the demultiplexer 13 may demultiplex the optical signal into an upper sideband wave and a lower sideband wave and output the signals to the first changeover switch 14 and the second changeover switch 15, respectively. For example, the demultiplexer 13 may include a distributor that divides the optical signal into two optical signals, an SSB converter that converts one optical signal into the upper sideband wave, and an SSB converter that converts the other optical signal into the lower sideband wave, and output the upper sideband wave and the lower sideband wave to the first changeover switch 14 and the second changeover switch 15, respectively.

[0045] The processing of the control unit 18 in the above-described embodiment may be implemented by a computer using software. In this case, a program for implementing this function may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an OS and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into a computer system. Furthermore, "computer-readable recording medium" may also include media that dynamically store programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or telephone lines, or media that store programs for a fixed period of time, such as volatile memory within a computer system that serves as a server or client. The program may be a program that implements only a portion of the above-described functions, or may be a program that can implement the above-described functions in combination with a program already stored in the computer system, or may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0046] 1 Transmission directivity control device, 11 Light source, 12 Optical modulator, 13 Demultiplexer, 16-1 First weighting unit, 16-2 Second weighting unit, 17 Photomixing unit, 171 Antenna element, 1711 Multiplexer, 1712 Square-law detection unit, 1713 Antenna, 1714 Mirror, 18 Control unit

Claims

1. A transmission directivity control device comprising: a demultiplexer that demultiplexes an optical signal into a first optical signal and a second optical signal; a first weighting unit that imparts a phase on a first axis that is a certain axis in space to the first optical signal; a second weighting unit that imparts a phase on a second axis that is orthogonal to the first axis to the second optical signal; and a photomixing unit that photomixes the first optical signal to which a phase has been imparted and the second optical signal to which a phase has been imparted, wherein the demultiplexer outputs the first optical signal to different input terminals of the first weighting unit depending on the wavelength of the first optical signal, and outputs the second optical signal to different input terminals of the second weighting unit depending on the wavelength of the second optical signal, the first weighting unit imparts a different phase to the first optical signal depending on the input terminal to which it is input, and the second weighting unit imparts a different phase to the second optical signal depending on the input terminal to which it is input.

2. The transmission directivity control device according to claim 1, further comprising: a control unit that controls the wavelength of the optical signal in accordance with the output direction of the signal from the photomixing unit.

3. A transmission directivity control device according to claim 1 or 2, wherein the first optical signal is a carrier wave of the optical signal, and the second optical signal is a sideband wave of the optical signal.

4. The transmission directivity control device according to claim 3, wherein the optical signal includes a plurality of carrier waves and a plurality of sideband waves.

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