Transmission directivity control device and transmission directivity control method

Abstract

A transmission directivity control device comprising a demultiplexer that separates an optical signal into a first optical signal and a second optical signal, a first axial phase slope addition unit that adds a phase slope in a first axis that is a given spatial axis to the first optical signal, a second axial phase slope addition unit that adds a phase slope in a second axis that is perpendicular to the first axis to the second optical signal, and an output unit that photomixes the first optical signal to which the phase slope has been added and a second optical signal to which the phase slope has been added.

Description

[Technical Field]

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

[0002] As a means of achieving faster and larger capacity wireless communications, the use of high-frequency bands, such as millimeter waves, is progressing. Because the spatial propagation loss of radio waves increases with increasing frequency (for example, free-space propagation loss increases in proportion to the square of the frequency), antennas with high gain are often used in these high-frequency bands. High-gain antennas are always highly directional, so it is necessary to align the beam direction with the other station in the wireless communication. When the direction of the other station is dynamic, a means for dynamically controlling the beam direction, i.e., beam steering, becomes essential. Furthermore, beam steering in antennas is required not only for wireless communications but also for applications such as radar, imaging, and wireless power transmission.

[0003] As a beam steering method, methods that have been devised and used include mechanically controlling the direction of the antenna, and controlling the radio waves emitted from the antenna by refracting or reflecting them with movable lenses or reflectors.In addition, phased array antennas are widely used because they have high durability and can follow movements as they do not use mechanical moving parts, and are suitable for making antennas smaller and lighter.

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

[0005] Phased array antennas that use analog circuits for weighting are widely used in fifth-generation mobile communication systems and millimeter-wave wireless LAN (Local Area Network) systems that use millimeter-wave bands.

[0006] In many wireless communication systems, the range in which wireless communication partners exist varies not within a two-dimensional plane but within three-dimensional space, so beam steering along two axes, such as azimuth and elevation, is required. For this reason, phased array antennas require weighting to perform 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 in a fifth-generation mobile communication base station in the 28 GHz band. If the radio frequency increases by approximately 10 times, for example, to 300 GHz, the propagation loss in free space will increase by 100 times, and tens of thousands of antenna elements will be required.

[0008] When the radio frequency is 300 GHz, the free space wavelength is 1 mm, so the spacing between antenna elements is generally set to half the wavelength, or 0.5 mm. In this case, it is difficult to install phase shifter circuits close to the antenna elements at intervals equivalent to the spacing between the antenna elements. Furthermore, to configure a circuit that forms multiple beams (a multi-beam forming circuit), it is necessary to arrange the same number of phase shifters in parallel as the number of beams, which is expected to make this even more difficult.

[0009] Rather than implementing phase shifter circuits according to the number of antenna elements, there is a method of using a passive circuit with a fixed phase shift amount and switching its input terminals. For example, Non-Patent Document 2 discloses a method of performing two-dimensional beam steering using a passive circuit. However, the circuit needs to be assembled three-dimensionally, and implementation in high frequency bands requires a waveguide configuration, making mass production difficult and also making it difficult to accommodate multiple elements.

[0010] Non-Patent Document 3 proposes a method of converting signals into light and weighting them using an optical circuit. As a method of 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 reuses a phase shifter while converting the optical wavelength. Non-Patent Document 5 discloses a means of performing two-dimensional beam steering by combining a planar phase shift circuit with an FBG (fiber bragg grating) reflection line with a delay time that varies depending on the optical wavelength, thereby enabling one-dimensional (within one plane) beam steering performed by the planar phase shift circuit and beam steering in a direction perpendicular to the plane by the FBG reflection line. Patent Document 2 discloses a means of forming multiple beams using wavelength multiplexing.

[0011] However, the above-disclosed devices and methods have drawbacks such as the difficulty of manufacturing a three-dimensional structure as the frequency increases and the number of parts required becoming enormous. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-023400 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-165956 [Non-patent literature]

[0013] [Non-Patent Document 1] Hikaru Watanabe, Shinsuke Uga, Hideyuki Nakamizo, Tsutsumi, Shintaro Shinjo, and Yu Kuriyama, "Millimeter-Wave Antenna and RF Front-End Technology for 5th Generation Mobile Communication Base Stations," IEICE Communications Society Magazine, Vol. 14, No. 3, 2020, pp. 222-231. [Non-patent document 2] Dong-Hun KIM Jiro HIROKAWA 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 [Non-patent document 3] 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. [Non-patent document 4] 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. [Non-Patent Document 5] 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 Summary of the Invention [Problem to be solved by the invention]

[0014] An object of the present invention is to provide a transmission directivity control device that can be more easily produced. [Means for solving the problem]

[0015] 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 changeover switch that outputs the first optical signal from one of a plurality of terminals; a second changeover switch that outputs the second optical signal from one of a plurality of terminals; a weighting unit that imparts a phase tilt to the first optical signal on a first axis that is a certain axis in space, which varies depending on the terminal of the first changeover switch from which the first optical signal is output; and that imparts a phase tilt to the second optical signal on a second axis that is orthogonal to the first axis, which varies depending on the terminal of the first changeover switch from which the second optical signal is output; and a photomixing unit that photomixes the first optical signal to which the phase tilt has been imparted and the second optical signal to which the phase tilt has been imparted.

[0016] One aspect of the present invention is a transmission directivity control method including: a demultiplexing step of demultiplexing an optical signal into a first optical signal and a second optical signal; a first switching step of outputting the first optical signal from one of a plurality of terminals; a second switching step of outputting the second optical signal from one of a plurality of terminals; a weighting step of imparting a phase tilt to the first optical signal on a first axis that is a certain axis in space, which differs depending on the terminal from which the first optical signal is output in the first switching step, and imparting a phase tilt to the second optical signal on a second axis that differs depending on the terminal from which the second optical signal is output in the second switching step and is orthogonal to the first axis; and a photomixing step of photomixing the first optical signal to which the phase tilt has been imparted and the second optical signal to which the phase tilt has been imparted. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a transmission directivity control device more simply. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating an example of the configuration of a transmission directivity control device 1 according to a first embodiment. [Figure 2] 10 is a diagram illustrating an example of the configuration of an antenna element 171. FIG. [Figure 3] 10 is a diagram illustrating an example of the configuration of an antenna element 171. FIG. [Figure 4] 4 is a flowchart showing the operation of the transmission directivity control device 1 according to the first embodiment. [Figure 5] FIG. 10 is a diagram illustrating an example of the configuration of a transmission directivity control device 1 according to a second embodiment. [Figure 6] 10 is a flowchart showing the operation of the transmission directivity control device 1 according to the second embodiment. [Figure 7] 10 is a diagram showing an example of the relationship between the wavelength of an optical signal input to a demultiplexer 13 and an antenna element 171 to which the optical signal is multiplexed. FIG. DETAILED DESCRIPTION OF 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] FIG. 1 is a diagram showing an example of the configuration of a transmission directivity control device 1 according to the first embodiment.

[0021] The transmission directivity control device 1 includes a light source 11, an optical modulator 12, a demultiplexer 13, a first changeover switch 14, a second changeover switch 15, a weighting unit 16, a photomixing unit 17, and a control unit 18.

[0022] The light source 11 outputs light to the optical modulator 12. 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 sideband waves. In the following description, the carrier wave L H (1), the sideband wave L S is expressed by equation (2) or equation (3).

[0023]

number

number

number

[0024] Equation (2) represents the upper sideband wave, and equation (3) represents the lower sideband wave. Demultiplexer 13 branches the carrier wave and the sideband wave and outputs them to first changeover switch 14 and second changeover switch 15, respectively. Demultiplexer 13 is, for example, an AWG (Arrayed Waveguide Grating).

[0025] The demultiplexer 13 includes a distributor 131 and an SSB (single side-band) modulator 132, and outputs a carrier wave L H and sideband L S The splitter 131 splits an input optical signal into two optical signals. The SSB modulator 132 suppresses the carrier component of one of the two optical signals and converts it into a sideband. This allows the splitter 131 and the SSB modulator 132 to generate a carrier and a sideband.

[0026] The demultiplexer 13 includes a distributor 131 and two optical comb filters 133 having periodic pass characteristics, and transmits the carrier L H and sideband L S and may generate a signal having a different wavelength. Splitter 131 splits an input optical signal into two optical signals. One optical comb filter 133 passes only light having a plurality of wavelengths with different carrier waves from one optical signal, and the other optical comb filter 133 passes only light having a plurality of wavelengths with different sideband waves from the other optical signal. When splitter 13 includes splitter 131 and SSB modulator 132, or when splitter 131 and optical comb filter 133, optical signals having two or more different wavelengths can be split into carrier waves and sideband waves.

[0027] The first changeover switch 14 has three output terminals. The first changeover switch 14 outputs a carrier wave from one of the output terminals to the weighting unit 16. The second changeover switch 15 has three output terminals. The second changeover switch 15 outputs a sideband wave from one of the output terminals to the weighting unit 16. For example, the first changeover switch 14 and the second changeover switch 15 have a demultiplexer and determine the output terminal from which the carrier wave or sideband wave is output depending on the wavelength of the input carrier wave or sideband wave. The wavelength of the carrier wave or sideband wave input to the first changeover switch 14 and the second changeover switch 15 is changed, for example, by the control unit 18 controlling the light source 11. Furthermore, for example, the control unit 18 may control the first changeover switch 14 and the second changeover switch 15 to switch the output terminal from which the carrier wave or sideband wave is output. The first changeover switch 14 and the second changeover switch 15 may be realized by, for example, an optical switch.

[0028] The weighting unit 16 has six input terminals and six output terminals. For example, a carrier wave is input to a first input terminal of the weighting unit 16 from a first output terminal of the first changeover switch 14. A carrier wave is input to a second input terminal of the weighting unit 16 from a second output terminal of the first changeover switch 14. A carrier wave is input to a third input terminal of the weighting unit 16 from a third output terminal of the first changeover switch 14. A sideband wave is input to a fourth input terminal of the weighting unit 16 from a first output terminal of the second changeover switch 15. A sideband wave is input to a fifth input terminal of the weighting unit 16 from a second output terminal of the second changeover switch 15. A sideband wave is input to a sixth input terminal of the weighting unit 16 from a third output terminal of the second changeover switch 15.

[0029] The weighting unit 16 applies a phase tilt φ on a first axis, which is a certain axis in space, to the carrier wave input from the first changeover switch 14. Hi (i=1, 2, 3) and outputs the weighted signal to the photomixing unit 17. The weighting unit 16 applies a phase slope φ H1 The weighting unit 16 applies a phase slope φ to the carrier wave input to the second input terminal and outputs the resulting signal from the first, second and third output terminals. H2The weighting unit 16 applies a phase slope φ to the carrier wave input to the third input terminal and outputs the resulting signal from the first, second and third output terminals. H3 and output from the first output terminal, the second output terminal, and the third output terminal.

[0030] For example, when an optical signal is input to the first input terminal, the weighting unit 16 outputs an optical signal without adding a phase from the first output terminal, and outputs an optical signal with a phase φ H1 The optical signal with the phase 2φ is output from the second output terminal. H1 For example, when an optical signal is input to the second input terminal, the weighting unit 16 outputs an optical signal to which no phase is added from the first output terminal, and outputs an optical signal to which a phase φ is added from the third output terminal. H2 The optical signal with the phase 2φ is output from the second output terminal. H2 For example, when an optical signal is input to the third input terminal, the weighting unit 16 outputs an optical signal to which no phase is added from the first output terminal, and outputs an optical signal to which a phase φ is added from the third output terminal. H3 The optical signal with the phase 2φ is output from the second output terminal. H3 The optical signal to which 0 and φ are added is output from the third output terminal. H1 , 2φ H1 The optical signal input to the second input terminal has a phase gradient of 0, φ H2 , 2φ H2 The optical signal input to the third input terminal has a phase gradient of 0, φ H3 , 2φ H3 More specifically, the phase gradient may be 0 degrees, 45 degrees, or 90 degrees, or 0 degrees, 90 degrees, or 180 degrees. The weighting section 16 does not need to output an optical signal to which no phase is added, and the phase gradient to be added may be, for example, φ, 2φ, or 3φ.

[0031] The carrier wave L to which a phase gradient is added, output from the weighting unit 16 H is expressed by equation (4).

[0032]

number

[0033] The weighting unit 16 applies a phase tilt φ on a second axis perpendicular to the first axis to the sideband wave input from the second changeover switch 15. vj (j=1, 2, 3) and outputs the weighted signal to the photomixing unit 17. The weighting unit 16 applies a phase slope φ v1 The weighting unit 16 applies a phase slope φ to the carrier wave input to the fifth input terminal and outputs the result from the fourth, fifth and sixth output terminals. v2 The weighting unit 16 applies a phase slope φ to the carrier wave input to the sixth input terminal and outputs the result from the fourth, fifth and sixth output terminals. v3 and output from the fourth output terminal, the fifth output terminal, and the sixth output terminal.

[0034] For example, when an optical signal is input to the fourth input terminal, the weighting unit 16 outputs an optical signal without adding a phase from the fourth output terminal, and outputs an optical signal with a phase φ V1 The optical signal with the phase 2φ is output from the fifth output terminal. V1 For example, when an optical signal is input to the fifth input terminal, the weighting unit 16 outputs an optical signal to which no phase is added from the fourth output terminal, and outputs an optical signal to which a phase φ is added from the sixth output terminal. V2 The optical signal with the phase 2φ is output from the fifth output terminal. V2 For example, when an optical signal is input to the sixth input terminal, the weighting unit 16 outputs an optical signal to which no phase is added from the fourth output terminal, and outputs an optical signal to which a phase φ is added from the sixth output terminal. V3 The optical signal with the phase 2φ is output from the fifth output terminal. V3 The optical signal to which 0 and φ are added is output from the sixth output terminal. V1 , 2φ V1 The optical signal input to the fifth input terminal has a phase gradient of 0, φ V2 , 2φ V2 The optical signal input to the sixth input terminal is given a phase gradient of 0, φ V3 , 2φV3 More specifically, the phase gradient may be 0 degrees, 45 degrees, or 90 degrees, or 0 degrees, 90 degrees, or 180 degrees.

[0035] The sideband wave L with a phase tilt added thereto output from the weighting unit 16 S is expressed by equation (5).

[0036]

number

[0037] The photomixing unit 17 includes a plurality of antenna elements 171. The plurality of antenna elements form a two-dimensional array antenna with 3 rows and 3 columns. The antenna element 171 located in the ith row and jth column has a phase tilt φ Hi and the phase gradient φ on the second axis vj That is, the first output terminal of the weighting unit 16 outputs an optical signal to the antenna elements 171 in the first row, to which a phase tilt φ H1 The second output terminal of the weighting unit 16 outputs a carrier wave to which a phase slope φ is applied to the antenna elements 171 in the second row. H2 The third output terminal of the weighting unit 16 outputs a carrier wave to which a phase tilt φ is applied to the antenna elements 171 in the third row. H3 The fourth output terminal of the weighting unit 16 outputs a carrier wave to which a phase tilt φ is applied to the antenna elements 171 of the first row. V1 The fifth output terminal of the weighting unit 16 outputs a sideband wave to which a phase inclination φ is applied to the antenna elements 171 of the second row. V2 The sixth output terminal of the weighting unit 16 outputs a sideband wave to which a phase inclination φ is applied to the antenna elements 171 of the third row. V3 The output is a sideband wave with

[0038] The photomixing unit 17 generates an electromagnetic wave with a frequency that is the difference between the carrier wave and the sideband wave. 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 the sideband wave input from the weighting unit 16. The multiplexed optical signal is H +L S The multiplexer 1711 is, for example, an AWG. The square-law detector 1712 converts the combined 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 RF_ij (L H +L S ) 2 This is the RF band extracted from and is proportional to equation (6).

[0039]

number

[0040] Therefore, the phase tilt of the output of the antenna element 171 in the i-th row and j-th column is φ vj -φ Hi is.

[0041] 3 is a diagram showing an example of the configuration of antenna element 171. In antenna element 171, a mirror 1714 may be used instead of multiplexer 1711 to multiplex an optical signal to which a phase has been assigned by weighting unit 16 and an optical signal to which a phase has been assigned by weighting unit 16.

[0042] 4 is a flowchart showing the operation of the transmission directivity control device 1 according to the first embodiment. The optical modulator 12 modulates the light output from the light source 11 to generate an optical signal (step S10). Then, the demultiplexer 13 demultiplexes the optical signal input from the optical modulator 12 into a carrier wave and sideband waves (step S11). The first changeover switch 14 outputs the carrier wave from one of a plurality of terminals to the weighting unit 16 (step S12-1). The second changeover switch 15 outputs the sideband waves from one of a plurality of terminals to the weighting unit 16 (step S12-2). The weighting unit 16 imparts a phase tilt on the first axis to the carrier wave (step S13-1). The weighting unit 16 imparts a phase tilt on the second axis to the sideband waves (step S13-2). The photomixing unit 17 photomixes the carrier wave and the sideband waves in each antenna element 171 (step S14). The photomixed optical signal is output from antenna 1713 as an RF signal.

[0043] 5 is a diagram showing the configuration of the weighting unit 16 according to the first embodiment. The weighting unit 16 according to the first embodiment includes a first axis weighting circuit 161 and a second axis weighting circuit 162. The first axis weighting circuit 161 applies a phase slope φ to the carrier wave input from the first changeover switch 14. Hi The first axis weighting circuit 161 applies a phase slope φ to the carrier wave input to the first input terminal of the weighting unit 16 and outputs the result to the photomixing unit 17. H1 The first axis weighting circuit 161 applies a phase slope φ to the carrier wave input to the second input terminal of the weighting unit 16 and outputs the phase slope φ from the first output terminal, the second output terminal, and the third output terminal. H2 The first axis weighting circuit 161 applies a phase slope φ to the carrier wave input to the third input terminal of the weighting unit 16 and outputs the result from the first output terminal, the second output terminal, and the third output terminal. H3 and output from the first output terminal, the second output terminal, and the third output terminal.

[0044] The second axis weighting circuit 162 applies a phase slope φ to the sideband wave input from the second changeover switch 15. vjand outputs the result to the photomixing unit 17. The second axis weighting circuit 162 applies a phase slope φ to the carrier wave input to the fourth input terminal of the weighting unit 16. v1 The second axis weighting circuit 162 applies a phase slope φ to the carrier wave input to the fifth input terminal of the weighting unit 16 and outputs the result from the fourth, fifth and sixth output terminals. v2 The second axis weighting circuit 162 applies a phase slope φ to the carrier wave input to the sixth input terminal of the weighting unit 16 and outputs the result from the fourth, fifth and sixth output terminals. v3 and output from the fourth output terminal, the fifth output terminal, and the sixth output terminal.

[0045] The first axis weighting circuit 161 and the second axis weighting circuit 162 impart a phase tilt to the optical signal by using 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.

[0046] As described above, the transmission directivity control device 1 includes a branching filter 13, a first changeover switch 14, a second changeover switch 15, a weighting unit 16, and a photomixing unit 17. The transmission directivity control device 1 performs weighting for each axis using an optical circuit and performs electronic beam steering. When weighting for two axes is performed collectively using a single weighting circuit, the number of elements in the weighting circuit is proportional to the square of the number M of antenna elements. However, in this embodiment, when weighting is performed for each axis, the number of elements in the weighting circuit is proportional to 2√M. This makes it possible to suppress the complexity that accompanies an increase in the number of antennas.

[0047] Furthermore, since the transmission directivity control device 1 performs phase shifting using analog circuits, the number of analog-to-digital converters can be significantly reduced compared to a fully digitally controlled array antenna in which phase shifting is performed entirely by digital signal processing. Furthermore, since the transmission directivity control device 1 performs phase shifting through analog processing of optical signals, it can be applied to circuits that electronically, rather than mechanically, perform beam scanning when emitting light in free-space optical communication (FSO communication) and the like, as well as when emitting radio waves.

[0048] (Second embodiment) 6 is a diagram showing an example of the configuration of the weighting unit 16 according to the second embodiment. The weighting unit 16 according to the second embodiment includes a multiplexer 163, a weighting circuit 164, and a demultiplexer 165. The weighting unit 16 according to the second embodiment includes three multiplexers 163-1, 163-2, and 163-3. The weighting unit 16 according to the second embodiment includes three demultiplexers 165-1, 165-2, and 165-3.

[0049] The multiplexer 163 multiplexes the carrier wave and sideband waves input from the first changeover switch 14 and the second changeover switch 15. The multiplexer 163-1 multiplexes the carrier wave input to the first input terminal with the sideband waves input to the fourth input terminal. The multiplexer 163-2 multiplexes the carrier wave input to the second input terminal with the sideband waves input to the fifth input terminal. The multiplexer 163-3 multiplexes the carrier wave input to the third input terminal with the sideband waves input to the sixth input terminal. The multiplexer 163 outputs an optical signal to a corresponding terminal of the weighting circuit 164. The multiplexer 163-1 outputs the multiplexed optical signal to the first input terminal of the weighting circuit 164. The multiplexer 163-2 outputs the multiplexed optical signal to the second terminal of the weighting circuit 164. The multiplexer 163-3 outputs the multiplexed optical signal to a third terminal of the weighting circuit 164. When an optical signal is input from only one of the first changeover switch 14 and the second changeover switch 15, the multiplexer 163 outputs the input optical signal to the weighting circuit 164. The multiplexer 163 is, for example, an AWG.

[0050] The weighting circuit 164 imparts a phase tilt on a first axis, which is a certain axis in space, to the carrier wave included in the optical signal input from the multiplexer 163, and outputs the result to the demultiplexer 165. The weighting circuit 164 imparts a phase tilt to the carrier wave that differs depending on the terminal to which the optical signal is input, and outputs the result to the demultiplexer 165. For example, the weighting circuit 164 imparts a phase tilt φ H1 The weighting circuit 164 applies a phase slope φ to the carrier wave input to the second input terminal and outputs the resulting signal to the duplexers 165-1, 165-2, and 165-3. H2 The weighting circuit 164 applies a phase slope φ to the carrier wave input to the third input terminal and outputs the resulting signal to the duplexers 165-1, 165-2, and 165-3. H3 and outputs the result to the demultiplexers 165-1, 165-2 and 165-3.

[0051] The weighting circuit 164 imparts a phase tilt on a second axis orthogonal to the first axis to the sidebands included in the optical signal input from the multiplexer 163, and outputs the result to the demultiplexer 165. The weighting circuit 164 imparts a different phase tilt to the sidebands depending on the terminal to which the optical signal is input, and outputs the result to the demultiplexer 165. For example, the weighting circuit 164 imparts a phase tilt φ v1 The weighting circuit 164 applies a phase slope φ to the sideband waves input to the second input terminal and outputs the result to the branching filters 165-1, 165-2, and 165-3. v2 The weighting circuit 164 applies a phase slope φ to the sideband waves input to the third input terminal and outputs the result to the branching filters 165-1, 165-2, and 165-3. v3 and outputs the result to the demultiplexers 165-1, 165-2 and 165-3.

[0052] The weighting circuit 164 applies a phase tilt to the optical signal by using 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.

[0053] The demultiplexer 165 demultiplexes the optical signal output from the weighting circuit 164 according to the wavelengths of the carrier wave and the sideband wave. H1 and φ v1 The demultiplexer 165-2 demultiplexes the optical signal to which the phase tilt φ H2 and φ v2 The demultiplexer 165-3 demultiplexes the optical signal to which the phase tilt φ H3 and φ v3 The demultiplexer 165 is, for example, an AWG.

[0054] Demultiplexer 165 outputs the demultiplexed carrier wave and sideband waves to photomixing unit 17. Demultiplexer 165-1 outputs the carrier wave with a phase slope added from the first output terminal, and outputs the sideband waves with a phase slope added from the fourth output terminal. Demultiplexer 165-2 outputs the carrier wave with a phase slope added from the second output terminal, and outputs the sideband waves with a phase slope added from the fifth output terminal. Demultiplexer 165-3 outputs the carrier wave with a phase slope added from the third output terminal, and outputs the sideband waves with a phase slope added from the sixth output terminal.

[0055] As described above, the transmission directivity control device 1 according to the first embodiment has two weighting circuits, whereas the transmission directivity control device 1 according to the second embodiment has one weighting circuit. This allows the number of weighting circuits to be reduced, making it possible to configure a transmission directivity control device that achieves similar effects with fewer elements.

[0056] (wavelength-based switching method) In the first embodiment, an example will be described in which the first changeover switch 14 and the second changeover switch 15 switch the output terminal of the weighting unit that outputs an optical signal depending on the wavelength of the input optical signal. Fig. 7 is a diagram showing an example of the relationship between the wavelength of the optical signal input to the demultiplexer 13 and the antenna element 171 to which the optical signal is multiplexed. The difference between adjacent wavelengths (for example, the difference between λ1 and λ2 or the difference between λ2 and λ3) is set to be larger than the wavelength corresponding to the frequency difference between the carrier wave and sideband waves of the optical signal.

[0057] For example, the first changeover switch 14 outputs carrier waves of wavelengths λ1, λ2, and λ3 to a first input terminal of the weighting unit 16, outputs carrier waves of wavelengths λ4, λ5, and λ6 to a second input terminal of the weighting unit 16, and outputs carrier waves of wavelengths λ7, λ8, and λ9 to a third input terminal of the weighting unit 16. Also, for example, the second changeover switch 15 outputs sideband waves of wavelengths λ1, λ4, and λ7 to a fourth input terminal of the weighting unit 16, outputs sideband waves of wavelengths λ2, λ5, and λ8 to a fifth input terminal of the weighting unit 16, and outputs sideband waves of wavelengths λ3, λ6, and λ9 to a sixth input terminal of the weighting unit 16. The first changeover switch 14 and the second changeover switch 15 each have, for example, a demultiplexer and are configured to distribute the above wavelengths.

[0058] As a result, for an optical signal of wavelength λ1, the carrier wave is input to the first input terminal of weighting unit 16 and a phase tilt is added, and the sideband waves are input to the fourth input terminal of weighting unit 16 and a phase tilt is added, and the two optical signals are multiplexed at nine antenna elements 171. Also, for an optical signal of wavelength λ2, the carrier wave is input to the first terminal of weighting unit 16 and a phase tilt is added, and the sideband waves are input to the fifth terminal of weighting unit 16 and a phase tilt is added, and the two optical signals are multiplexed at nine antenna elements 171. As described above, the phase tilt added to the optical signal can be changed depending on the wavelength of the optical signal input to demultiplexer 13, and transmitted from antenna elements 171.

[0059] Alternatively, the transmission directivity control device 1 may include multiple light sources 11 and optical modulators 12, and the demultiplexer 13 may demultiplex each of the multiple optical signals into a carrier wave and a sideband wave. In this case, the first selector switch 14 outputs a first optical signal from one of multiple terminals for each of the multiple optical signals. The second selector switch 15 outputs a second optical signal from one of multiple terminals for each of the multiple optical signals. The weighting unit 16 imparts a phase tilt on a first axis to the first optical signal and a phase tilt on a second axis to the second optical signal for each of the multiple optical signals. The photomixing unit 17 photomixes the first optical signal to which a phase tilt has been imparted and the second optical signal to which a phase tilt has been imparted for each of the multiple optical signals. This allows the antenna element 171 to transmit signals in directions based on the respective optical signals and to perform an operation of transmitting multiple beams.

[0060] 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 can be made within the scope that does not deviate from the gist of the present invention. For example, in the above-described embodiment, the weighting circuit has three input terminals and three output terminals, and the array antenna included in the photomixing unit 17 has antenna elements 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, such as three rows and three columns or four rows and four columns. The input terminals and output terminals of the weighting circuit may vary depending on the number of rows and columns of antenna elements included in the array antenna.

[0061] 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 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. [Explanation of symbols]

[0062] 1 Transmission directivity control device, 11 Light source, 12 Optical modulator, 13 Demultiplexer, 14 First changeover switch, 15 Second changeover switch, 16 Weighting section, 161 First axis weighting circuit, 162 Second axis weighting circuit, 163 Multiplexer, 164 Weighting circuit, 165 Demultiplexer, 17 Photomixing section, 171 Antenna element, 1711 Multiplexer, 1712 Square-law detection section, 1713 Antenna, 1714 Mirror

Claims

1. a demultiplexer that demultiplexes the optical signal into a first optical signal and a second optical signal; a first changeover switch that outputs the first optical signal from one of a plurality of terminals; a second selector switch that outputs the second optical signal from one of a plurality of terminals; a weighting unit that imparts a phase gradient to the first optical signal on a first axis that is a certain axis in space, the phase gradient varying depending on the terminal of the first changeover switch to which the first optical signal is output, and that imparts a phase gradient to the second optical signal on a second axis that is orthogonal to the first axis, the phase gradient varying depending on the terminal of the second changeover switch to which the second optical signal is output; a photomixing unit that photomixes the first optical signal to which a phase tilt has been added and the second optical signal to which a phase tilt has been added; A transmission directivity control device comprising:

2. The weighting unit a first axis phase tilt imparting unit that imparts a phase tilt along the first axis to the first optical signal; a second axis phase tilt imparting unit that imparts a phase tilt on the second axis to the second optical signal; The transmission directivity control device according to claim 1 , comprising:

3. The weighting unit a multiplexer that multiplexes the first optical signal input from the first changeover switch and the second optical signal input from the second changeover switch; a weighting circuit that imparts a phase tilt along a first axis, which is a certain axis in space, to the first optical signal included in the combined optical signal, and imparts a phase tilt along a second axis, which is perpendicular to the first axis, to the second optical signal included in the combined optical signal; a demultiplexer that demultiplexes the optical signal output from the weighting circuit; The transmission directivity control device according to claim 1 , comprising:

4. the phase tilt imparted to the first optical signal and the second optical signal is based on the wavelengths of the first optical signal and the second optical signal; The transmission directivity control device according to claim 1 .

5. the demultiplexer demultiplexes each of the plurality of optical signals into a first optical signal and a second optical signal; the first changeover switch outputs the first optical signal from one of a plurality of terminals for each of the plurality of optical signals; the second changeover switch outputs the second optical signal from one of a plurality of terminals for each of the plurality of optical signals; the weighting unit imparts a phase tilt on the first axis to the first optical signal and imparts a phase tilt on the second axis to the second optical signal for each of the plurality of optical signals; the photomixing unit photomixes, for each of the plurality of optical signals, the first optical signal to which a phase tilt has been imparted and the second optical signal to which a phase tilt has been imparted; The transmission directivity control device according to claim 4 .

6. the first optical signal and the second optical signal are a carrier wave and a sideband wave or an upper sideband wave and a lower sideband wave; The transmission directivity control device according to claim 1 .

7. the branching filter includes a distributor and an SSB (single side-band) modulator; the splitter splits an input optical signal into two optical signals; the SSB modulator converts one of the two optical signals into a sideband wave; The transmission directivity control device according to claim 6 .

8. a demultiplexing step of demultiplexing the optical signal into a first optical signal and a second optical signal; a first switching step of outputting the first optical signal from one of a plurality of terminals; a second switching step of outputting the second optical signal from one of a plurality of terminals; a weighting step of imparting a phase gradient to the first optical signal on a first axis that is a certain axis in space, which varies depending on the terminal from which the first optical signal is output in the first switching step, and imparting a phase gradient to the second optical signal on a second axis that is orthogonal to the first axis, which varies depending on the terminal from which the second optical signal is output in the second switching step; a photomixing step of photomixing the first optical signal to which a phase tilt has been applied and the second optical signal to which a phase tilt has been applied; A transmission directivity control method comprising:

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