Transmission directivity control apparatus

Abstract

Provided is a transmission directivity control apparatus comprising: a generator that generates a light wave in which Nh continuous waves of light from a continuous wave of light having a frequency of f1 to a continuous wave of light having a frequency of fN_h are wavelength-multiplexed with the phases thereof synchronized; a first optical splitter that splits the output of the generator into two directions; a frequency converter that shifts the frequency of the light wave which has been split in one of the two directions, to a prescribed direction by a prescribed frequency of fRF; a first optical circuit that provides the light wave which has been split in a second direction of the two directions with a phase change depending on the frequency; a modulator that modulates the light wave which has propagated through the first optical circuit; an optical coupler that is for obtaining a resultant wave from the output of the frequency converter and the output of the modulator; a first frequency divider that is for obtaining, from the output of the optical coupler, for each p, a p-th paired wave, which is a resultant wave from a modulated wave having a center frequency of fp included in the output of the modulator and a continuous wave having a frequency shifted by fRF from the frequency fp; a p-th photodiode that receives the p-th paired wave; and a p-th antenna element that is excited by the output of the p-th photodiode.

Description

Transmission directivity control device

[0001] This invention relates to a transmission directionality control device.

[0002] To achieve higher speeds and larger capacities in wireless communication, the use of high-frequency bands above the millimeter wave range is progressing. Since the spatial propagation loss of radio waves increases with increasing frequency (for example, free-space propagation loss increases proportionally to the square of the frequency), antennas with high gain are often used in these high-frequency bands. Because high-gain antennas always have high directivity, it is necessary to align the direction of their beam with the wireless communication station. If the direction of the station is dynamic, the application of a means to dynamically control the beam direction, i.e., beam steering, is essential. Furthermore, beam steering in antennas is required not only in wireless communication but also in applications such as radar, imaging, and wireless power transmission.

[0003] As a means of beam steering, methods have been devised and used, including mechanically controlling the direction of the antenna and controlling the direction by refracting or reflecting the radio waves emitted from the antenna using movable lenses or mirrors. Furthermore, because they do not use mechanically moving parts, phased array antennas are widely used, offering high durability and responsiveness to movement, and are suitable for miniaturizing and reducing the weight of antennas.

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

[0005] In fifth-generation mobile communication systems and millimeter-wave wireless LAN (Local Area Network) systems that use the millimeter-wave band, phased array antennas that use analog circuits for weighting are frequently used.

[0006] In many wireless communication systems, the range of the receiving station changes not in a two-dimensional plane but in three-dimensional space, requiring beam steering on two axes, such as azimuth and elevation. Therefore, phased array antennas require weighting to perform two-dimensional beam steering using a two-dimensional array antenna with antenna elements arranged planarly.

[0007] For example, a 256-element phased array antenna has been proposed for use in base stations for fifth-generation mobile communications in the 28 GHz band. For instance, if the radio frequency increases tenfold, such as to 300 GHz, the propagation loss in free space increases a hundredfold, and it is thought that 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 it is common to space antenna elements at half the wavelength, or 0.5 mm. In this case, it is difficult to install phase shifter circuits near the antenna elements at the same spacing as the antenna elements. Furthermore, to configure a circuit that forms multiple beams (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 be even more difficult.

[0009] Instead of implementing a phase shifter circuit corresponding to the number of antenna elements, there is a method that uses a passive circuit with a fixed phase shift amount and switches its input terminal. For example, Non-Patent Document 1 discloses a method for performing two-dimensional beam steering using a passive circuit. However, this requires assembling the circuit three-dimensionally, and implementation in the high-frequency band requires the use of waveguides, making mass production difficult, as is mitigating the need for multi-element designs.

[0010] Furthermore, methods have been proposed in which signals are converted into light and weighted using optical circuits. As a method for weighting using optical circuits, a three-dimensional optical circuit that performs two-dimensional beam steering using wavelength-dispersive transmission lines has been proposed. A method using a loop configuration that repeatedly reuses a phase shifter while converting the optical wavelength has also been proposed. Non-patent documents 2 and 3 disclose a means for performing two-dimensional beam steering by combining a planar phase shift circuit with FBG (fiber bragg gratings) reflection lines that have different delay times depending on the optical wavelength, thereby enabling beam steering in a direction perpendicular to the plane performed by the FBG reflection lines, in addition to one-dimensional (within one plane) beam steering performed by the planar phase shift circuit. Means for performing beam steering by adjusting the intervals between multiple wavelengths using wavelength division multiplexing or a tunable laser have also been proposed.

[0011] 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 100.10 (2017): 884-892.

[0012] Beatriz Ortega, Jose Mora, and Ruben Chulia. "Optical beamformer for 2-D phased array antenna with subarray partitioning capability." IEEE Photonics Journal 8.3 (2016): 1-9.

[0013] Y. Sun, R. Zhang, Q. Li and Z. Wang, "Tunable Multiwavelength Fiber Laser Source for Continuous True-Time-Delay Beamforming," in IEEE Photonics Technology Letters, vol. 28, no. 11, pp. 1261-1263, 1 June 1, 2016.

[0014] However, in the devices and methods proposed so far, when performing beam steering, a three-dimensional waveguide circuit or wavelength conversion to a plurality of optical wavelength bands or a wavelength dispersion line is required, resulting in a problem that the device size or cost increases.

[0015] In view of the above circumstances, an object of the present invention is to provide a technique for suppressing the device size or cost.

[0016] One aspect of the present invention is a wave in which N (N is a predetermined integer of 2 or more) continuous waves of light from a continuous wave of light having a frequency f １ to a continuous wave of light having a frequency f Ｎ_ｈ are wavelength multiplexed in a state where they are phase synchronized, and each frequency f ｈ from the frequency f ｈ to the frequency f １ to the frequency f Ｎ_ｈ satisfies the condition that the N ｈ frequencies f ｐ (p is 1 to N_h) are different predetermined frequencies. A generator that generates an optical wave, a first optical splitter that is an optical splitter that branches the output of the generator in two directions, and a frequency of the optical wave branched in a first direction that is one of the two directions is shifted by a predetermined frequency f ＲＦ only in a predetermined direction, a first optical circuit that gives a phase change corresponding to the frequency to the optical wave branched in a second direction that is a direction different from the first direction among the two directions, and the first optical circuit A modulator that modulates the propagated optical wave, an optical coupler that obtains a combined wave of the output of the frequency converter and the output of the modulator, and from the output of the optical coupler, the center frequency f ｐ The fp band wave, which is the modulated wave, and the frequency fｐ f ＲＦ The transmission directivity control device comprises a first frequency divider that obtains a p-p pair wave for each p, which is a composite wave with a continuous wave whose frequency has been shifted by a certain amount; a p-p photodiode that receives the p-p pair wave; and a p-p antenna element that is an antenna element excited by the output of the p-p photodiode.

[0017] This invention makes it possible to reduce the size or cost of the device.

[0018] An explanatory diagram illustrating the antenna of the embodiment. An explanatory diagram illustrating the antenna of the first modified example. An explanatory diagram illustrating the antenna 100b of the second modified example. A diagram showing an example of a phase shift branch in a modified example.

[0019] (Embodiment) Figure 1 is an explanatory diagram illustrating the antenna 100 of the embodiment. The antenna 100 includes an optical frequency comb generator 101, an optical splitter 102, a frequency converter 103, a delay line 104, a modulator 105, an optical coupler 106, a frequency divider 107, and photodiodes 108-1 to 108-N ｈ N ｈ The photodiode 108 and antenna elements 109-1 to 109-N ｈ N ｈ It comprises several antenna elements 109. The optical splitter 102 is an example of a first optical splitter. The frequency divider 107 is an example of a first frequency divider.

[0020] The optical frequency comb generator 101 is an optical frequency comb generator. Therefore, the optical frequency comb generator 101 generates a wave in which multiple continuous waves with different frequencies are wavelength-multiplexed in a phase-synchronized state, the continuous waves being continuous waves of light, and all of the frequencies are predetermined frequencies.

[0021] More specifically, the optical frequency comb generator 101 generates a frequency f １ From a continuous wave of light, frequency f Ｎ_ｈ N up to a continuous wave of light ｈ pieces (N ｈ A light wave obtained by wavelength multiplexing a continuous wave of light (where f is a predetermined integer of 2 or more) in a phase-synchronized state, wherein the frequency f１ From the above frequency f Ｎ_ｈ up to N ｈ Each of the frequencies f ｐ This generates light waves that satisfy the condition that (p is 1 to N_h) have different predetermined frequencies. Note that N_h is N ｈ This means that the frequency spectrum of wavelength-multiplexed light waves is, for example, comb-shaped. The optical frequency comb generator 101 is an example of a generator.

[0022] The optical splitter 102 is an optical splitter. The optical splitter 102 splits the wavelength-multiplexed optical wave output from the optical frequency comb generator 101 into two directions. The optical wave split in the first direction, which is one of the two directions, is the local wave. The local wave is incident on the frequency converter 103. The optical wave split in the second direction, which is the other of the two directions, is the carrier wave. The carrier wave is incident on the modulator 105 through the delay line 104.

[0023] The frequency converter 103 converts the frequency of the incident local wave. Specifically, the frequency converter 103 converts the frequency of the incident local wave to a predetermined frequency f in a predetermined direction. ＲＦ It shifts by only that much. Therefore, to explain in terms of frequency spectrum, the frequency converter 103 shifts the frequency spectrum of the local wave in a predetermined direction to a predetermined frequency f ＲＦ It shifts by only that much. If we express the processing performed by the frequency converter 103 in mathematical terms, for the local wave, for example, e^(-2πif ＲＦ This is the process of multiplying by t).

[0024] The predetermined direction may be, for example, a direction that lowers the frequency or a direction that raises it. When the predetermined direction is a direction that lowers the frequency, the light wave output by the frequency converter 103 has a frequency (f １ -f ＲＦ From a continuous wave of light (f Ｎ_ｈ -f ＲＦ N up to a continuous wave of light ｈ It is a composite wave of continuous waves of individual light particles.

[0025] When the predetermined direction is the upward direction, the light wave output by the frequency converter 103 has a frequency (f １ +fＲＦ From a continuous wave of light (f Ｎ_ｈ +f ＲＦ N up to a continuous wave of light ｈ It is a composite wave of continuous waves of individual light particles.

[0026] The output of the frequency converter 103 is incident on the optical coupler 106. The frequency converter 103 is an optical element, such as an optical modulator like an LN modulator. The frequency converter 103 may also be, for example, a PPLN wavelength converter.

[0027] Image G01 shows an example of the frequency spectrum of a local wave incident on the frequency converter 103. Image G01 also shows the phases of each continuous wave included in the local wave incident on the frequency converter 103. Since the phase is relative to that of a light wave, the phase of the local wave is used as the reference. That is, Image G01 shows that the phases of each continuous wave included in the local wave incident on the frequency converter 103 are the reference and are identical.

[0028] The delay line 104 is a delay line. Therefore, the carrier wave propagating along the delay line 104 experiences a delay relative to the local wave. The delay line may be a variable delay line or a delay line with a fixed delay amount. The continuous wave of each frequency of the carrier wave is subjected to a phase change by the delay line 104, which depends on the delay amount and frequency. The amount of phase change is, for example, approximately proportional to the delay amount and frequency.

[0029] Image G02 shows an example of the phase change of each continuous wave included in the carrier wave due to the delay line 104. While Image G01 shows that the phases of each continuous wave included in the carrier wave are the same and are reference, Image G02 shows that the phase of each continuous wave has become different from that of the local wave due to the delay line 104. More specifically, Image G02 shows that the phase of each continuous wave has changed by an amount proportional to the frequency compared to the phase in Image G01 due to the delay line 104.

[0030] Modulator 105 is a modulator such as an IQ modulator. Therefore, the carrier wave is modulated by modulator 105. Thus, the output of modulator 105 is the modulated wave, which is a composite wave of the carrier wave and the baseband signal. Image G03 shows an example of the frequency spectrum of the output of modulator 105 (i.e., the modulated wave). In Figure 1, "Signal 1" refers to the wave output by modulator 105 in the example in Figure 1. The output of modulator 105 is incident on optical coupler 106.

[0031] The optical coupler 106 is an optical coupler that combines light waves incident from the (1+1) direction. More specifically, the output of the frequency converter 103 and the output of the modulator 105 are incident on the optical coupler 106. Therefore, the optical coupler 106 outputs a composite wave of the output of the frequency converter 103 and the output of the modulator 105. The output of the optical coupler 106 is incident on the frequency divider 107.

[0032] The frequency divider 107 divides the incident light wave into predetermined frequency ranges. The frequency divider 107 is, for example, an arrayed waveguide grating (AWG).

[0033] The light waves after division by the frequency divider 107 are incident on different photodiodes 108 for each of the above frequency domains. In the example in Figure 1, the output of the optical coupler 106 is incident on different N in each frequency domain by the frequency divider 107. ｈ The light wave is divided into individual light waves. Each of these divided light waves is then incident on a photodiode 108 that is pre-associated with a specific frequency range.

[0034] A photodiode outputs an electrical signal of the frequency difference when light waves of different frequencies are incident on it. Therefore, the antenna element 109 outputs a frequency f ＲＦ The radio waves are emitted.

[0035] The antenna 100 has multiple antenna elements 109, but each of them operates at a frequency f ＲＦ It emits radio waves. Therefore, the antenna 100 emits the frequency f radiated from the multiple antenna elements 109 that the antenna 100 has. ＲＦThe radio waves interfere with each other, and radio waves (i.e., beams) are emitted.

[0036] The light waves obtained by the division by the frequency divider 107 will be explained in more detail. ｈ Each individual light wave is obtained for each peak in the frequency spectrum of the carrier wave. More specifically, the frequency divider 107 divides the center frequency f included in the output of the modulator 105. ｐ The modulated wave (hereinafter referred to as "fp band wave") and frequency f ｐ f ＲＦ A p-th composite wave is obtained for each p-th composite wave, which is a composite wave with a continuous wave whose frequency has shifted by a certain amount. The N_h composite waves from the first composite wave to the (N_h) composite wave are the light waves obtained by the frequency divider 107.

[0037] Since the fp-bandwave is included in the output of modulator 105, it can be said that modulator 105 outputs the fp-bandwave. Therefore, the p-th composite wave is the f output of modulator 105. ｐ Bandwidth and frequency f ｐ f ＲＦ It can be said that it is a composite wave with a continuous wave whose frequency has shifted by only one degree.

[0038] In the modified example described later, the frequency divider 107 will control n ｈ Each of the modulators 105 outputs f ｐ Bandwidth and frequency f ｐ f ＲＦ A composite wave (hereinafter referred to as the "p-p pair wave") with a continuous wave whose frequency has shifted by a certain amount is obtained for each p. To explain the relationship between the p-p pair wave and the p-p composite wave, n ｈ In the case where = 1, the p-th composite wave is the p-th pair wave.

[0039] Frequency divider 107 is an example of a first frequency divider.

[0040] Image G04-p shows an example of the frequency spectrum of the p-th composite wave. Therefore, image G04-1 shows an example of the frequency spectrum of the first composite wave, and image G04-N ｈ is the Nth ｈ This shows an example of the frequency spectrum of a composite wave.

[0041] Photodiode 108-p is the p-th pair wave (i.e., n ｈ This is a photodiode that receives the p-th composite wave (when = 1) and outputs an electrical signal. Note that photodiode 108-p is an example of a p-th photodiode. Photodiode 108-p is connected to antenna element 109-p. Antenna element 109-p is an antenna element. Antenna element 109-p is excited by the electrical signal output by photodiode 108-p and emits electromagnetic waves. The electromagnetic waves emitted by multiple antenna elements 109 interfere to form a beam. In this way, antenna 100 emits a beam. Note that antenna element 109-p is an example of a p-th antenna element.

[0042] As indicated in Figure 1, "The beam direction is determined by the phase gradient," the direction of the beam radiated by the antenna 100 is determined by the difference in phase changes for each frequency obtained by the delay line 104. Therefore, the beam direction can be changed by changing the phase changes for each frequency obtained by the delay line 104.

[0043] The delay imparted by the delay line 104 to the light wave may be controlled, for example, by a human or by computer.

[0044] <About the effects of Antenna 100> Antenna 100 can change the beam radiation direction simply by changing the delay (phase) that the delay line 104 imparts to the light wave. Therefore, Antenna 100 can reduce the size and cost of the device compared to antennas that require wavelength conversion or chromatic dispersion for each of the multiple spectra generated by the optical frequency comb generator in order to change the beam radiation direction.

[0045] The antenna 100 configured in this way includes a delay line 104. Therefore, as described in <About the effects of the antenna 100>, the size or cost of the device (antenna) can be reduced.

[0046] <Examples of other effects of Antenna 100> However, in the case of the technology described in Non-Patent Document 2 or 3, the modulator uses RF signal modulation, not IQ modulation (baseband). Therefore, for example, when light of frequency Fc is modulated with an RF signal with center frequency Frf, signals are generated around two frequencies: (Fc + Frf) and (Fc - Frf). For example, Fc is 193 THz and Frf is 150 GHz. Therefore, for example, Fc + Frf is 193.15 THz and Fc - Frf is 192.85 THz. As a result of signals being generated around two frequencies, if strong chromatic dispersion is applied for beamforming, the effects of dispersion on the signals around frequency (Fc + Frf) and the signals around frequency (Fc - Frf) will be significantly different. As a result, the RF signal, which is a composite wave of signals around frequency (Fc + Frf) and signals around frequency (Fc - Frf), becomes distorted.

[0047] Furthermore, optical modulators capable of modulating RF signals exceeding 100 GHz have only been realized under limited circumstances, and optical modulation using radio high-frequency band signals exceeding 100 GHz is not easy.

[0048] On the other hand, in the case of antenna 100, since the signal lies around frequency Fc, the distortion of the radio signal caused by chromatic dispersion is reduced compared to the technology described in Non-Patent Document 1 or 2.

[0049] Furthermore, the technologies described in Non-Patent Documents 2 or 3 require either changing the frequency of the light source using a tunable laser or altering the dispersion characteristics of the FBG by heat or other means when changing the beam direction in one dimension (within one plane), which raises concerns about increased equipment costs and the time required to change the beam direction.

[0050] On the other hand, let's explain antenna 100 in more detail. In antenna 100, the variable delay adjusts the phase difference between the local wave and the carrier wave, and the phase of the output RF is controlled by the phase difference between these two optical waves. Therefore, it does not require control of the laser wavelength or FBG dispersion characteristics.

[0051] (Modified Version) <First Modified Version> Figure 2 is an explanatory diagram illustrating a modified antenna 100a. Hereafter, components having the same configuration as antenna 100 will be denoted by the same reference numerals as in Figure 1, and their explanation will be omitted. Note that the value n in the following explanation refers to... ｈ Antenna 100a, where n is 1, is antenna 100. ｈ When this value is 1, the optical splitter 110 described later is equivalent to not existing, and the optical coupler 106a described later is the optical coupler 106.

[0052] Antenna 100a includes an optical frequency comb generator 101, an optical splitter 102, an optical splitter 110, a frequency converter 103, a delay line 104, a modulator 105, an optical coupler 106a, a frequency divider 107, and photodiodes 108-1 to 108-N. ｈ N ｈ The photodiode 108 and antenna elements 109-1 to 109-N ｈ N ｈ It comprises several antenna elements 109. The optical splitter 110 is an example of a second optical splitter.

[0053] The optical splitter 110 receives the light wave that has been split in the second direction by the optical splitter 102. ｈ Direction (n ｈ is 1 or more N ｈ This is an optical splitter that branches to the following predetermined integers. In the example in Figure 2, n ｈ n is a predetermined integer of 2 or more. Each light wave branched by the optical splitter 110 passes through the delay line 104 and enters the modulator 105. Therefore, in antenna 100a, the delay line 104 and modulator 105 are n ｈ There are n. In Figure 2, to improve visibility, ｈ Each modulator 105 is displayed as a single block.

[0054] The above n ｈ A light wave propagating in the p-th direction among the directions is n ｈ Passing through the p-th delay line 104 of the existing delay lines 104, n ｈ The signal is injected into the p-th modulator 105 out of the n modulators 105. In other words, the above n ｈThe light wave propagating in the p-th direction passes through the pre-associated delay line 104 and is incident on the pre-associated modulator 105. ｈ Light waves propagating in different directions pass through different delay lines 104 and are incident on different modulators 105.

[0055] n ｈ The modulations by each modulator 105 may be different from each other. Therefore, n ｈ The antenna 100a, which is equipped with several modulators 105, has different n values ​​from each other. ｈ Multiple types of information can be simultaneously transmitted from the antenna element 109 to the target of transmission.

[0056] Image G03a is n ｈ An example of the frequency spectrum of the output (i.e., the modulated wave) of each modulator 105 is shown. Note that “Signal 1” in Figure 2 refers to n in the example in Figure 2. ｈ This refers to the modulated wave output by the first modulator 105 among the modulators 105. In Figure 2, “Signal n ｈ " is n in the example in Figure 2 ｈ n of the modulators 105 ｈ This refers to the modulated wave output by the second modulator 105.

[0057] The output of each modulator 105 is incident on the same optical coupler 106a.

[0058] The optical coupler 106a is (n ｈ +1) This is an optical coupler that couples light waves incident from the direction of +1). More specifically, the optical coupler 106a receives the output of the frequency converter 103 and n ｈ Each output of the modulators 105 is incident. Therefore, the optical coupler 106a is incident on the output of the frequency converter 103 and n ｈ It outputs a composite wave with the outputs of each modulator 105. The output of the optical coupler 106a is incident on the frequency divider 107.

[0059] Thus, n ｈ The light waves propagating in each direction pass through different delay lines 104 and modulators 105 before being incident on the same optical coupler 106a.

[0060] In antenna 100a, the frequency divider 107 outputs N ｈ pairs of p-waves.

[0061] Image G04a-p represents an example of the frequency spectrum of the p-th pair of waves. Therefore, image G04a-1 represents an example of the frequency spectrum of the first pair of waves, and image G04a-N ｈ represents an example of the frequency spectrum of the Nth ｈ pair of waves.

[0062] Antenna 100a includes an optical splitter 110, and the optical wave is split by the optical splitter 110 into n ｈ directions. Then, the optical waves propagating in each direction may each undergo a modulation different from that of the optical waves propagating in other directions by the modulator 105. Therefore, antenna 100a can radiate multiple types of radio waves.

[0063] In FIG. 2, as described by "the beam direction is determined by the phase gradient", the direction of the beam radiated by antenna 100a is determined by the difference in the phase change for each frequency obtained by the delay line 104. Therefore, by changing the phase change for each frequency obtained by the delay line 104, the direction of the beam can be changed.

[0064] <Second modification example> FIG. 3 is an explanatory diagram for explaining the modified antenna 100b. Hereinafter, those having the same configuration as antenna 100a will be denoted by the same reference numerals as in FIG. 2, and the description will be omitted. In the following description, the antenna 100b in which the value N ｖ is 1 is antenna 100a. When the value N ｖ is 1, the value n ｖ is 1. Also, when the value n ｖ is 1, it is synonymous that the optical splitter 111 does not exist.

[0065] Antenna 100b includes an optical frequency comb generator 101, an optical splitter 102, an optical splitter 110, a frequency converter 103, a delay line 104, an optical splitter 111, a modulator 105, an optical coupler 106a, an optical circuit 112, a frequency divider 107, and N ｖ pieces (N ｖThe sum N (where N is a predetermined integer of 1 or more) of the photodiodes 108-p ｈ ×N ｖ photodiodes 108 and N ｖ The sum N (where N is a predetermined integer of 1 or more) of the antenna elements 109-p ｈ ×N ｖ antenna elements 109.

[0066] The optical splitter 111 exists for each delay line 104. Therefore, the antenna 100b includes n ｈ optical splitters 111. The optical splitter 111 branches the incident light wave into n ｖ directions (where n ｖ is an integer of 1 or more and N ｖ or less). The output of the optical splitter 111 is incident on the modulator 105. The optical splitter 111 is located after the optical splitter 102 and before the modulator 105. In the example of FIG. 3, the light wave that has propagated through the delay line 104 is incident on the optical splitter 111.

[0067] In the antenna 100b, the modulator 105 is provided for each branch by the optical splitter 111. Since the optical splitter 111 branches the light wave in n ｖ directions, in the antenna 100b, there are n ｈ ×n ｖ modulators 105.

[0068] The modulation by the n ｈ ×n ｖ modulators 105 may be different from each other. Therefore, the antenna 100b having n ｈ ×n ｖ modulators 105 can simultaneously transmit n <00QQ0113>×n ｖ different types of information from the antenna element 109 to the transmission target.

[0069] The optical splitter 111 is an example of a third optical splitter.

[0070] The image G03b shows an example of the frequency spectrum of the output (i.e., the modulated wave) of each of the n ｈ ×n ｖ modulators 105. Note that "Signal 1" in FIG. 3 is n ｈ ×n ｖThis refers to the modulated wave output by the first modulator 105 among the modulators 105. In Figure 3, "Signal N" means N = n in the example in Figure 3. ｈ ×n ｖ N = n among the modulators 105 ｈ ×n ｖ This refers to the modulated wave output by the second modulator 105.

[0071] The N modulators 105 have n elements. ｈ n is ｖ The devices are pre-classified to belong to only one of the following sets (hereinafter referred to as "classification sets"). In antenna 100b, the outputs of the N modulators 105 belonging to the same classification set are incident on the same optical coupler 106a, and the outputs of the modulators belonging to different classification sets are incident on different optical couplers 106a. Therefore, the output destination condition is satisfied in antenna 100b. The output destination condition is that the outputs of the N modulators 105 belonging to the same classification set are incident on the same optical coupler 106a, and the outputs of the modulators belonging to different classification sets are incident on different optical couplers 106a.

[0072] Therefore, antenna 100b connects optical coupler 106a to n ｖ Each one has its own. ｖ The outputs of each optical coupler 106a are incident on the same optical circuit 112.

[0073] The optical circuit 112 receives n from the optical coupler 106a. ｖ For each individual light wave, a matrix-like process equivalent to matrix operation is performed to demultiplex, phase change, or combine the waves, N ｖ It outputs n light waves. That is, the optical circuit 112 outputs n ｖ The light waves incident from the directions N ｖ The light wave is split into individual light waves, and each light wave is given the same or different predetermined phase change, and then n ｖ The process is equivalent to combining each individual wave. At this time, specific phase conditions may be satisfied so that the beam directions of the ultimately emitted radio waves are each in different, independent directions. The phase conditions are N ｖThe condition includes the fact that the phase difference between any two of the output light waves is proportional to the distance between the two corresponding antenna elements 109. The output light waves are the light waves output by the optical circuit 112.

[0074] Let's explain a more specific example of such a phase condition. The signal that excites the antenna element 109 is the output of the photodiode 108, and the phase difference between the signals output by different photodiodes 108 is equal to the phase difference of the light waves incident on each photodiode 108. Therefore, the phase condition can be defined by focusing on the antenna element 109.

[0075] Therefore, we focus on the antenna element 109, N ｖ The phase conditions when the antenna elements 109 are positioned along a predetermined one direction will be explained. ｖ Of the number of antenna elements 109, one predetermined antenna element 109 is referred to as the first element, and the nth element (where n is 1 or greater than or equal to N) is referred to as the nth element. ｖ The antenna element 109 closest to the following integer is referred to as the (n+1)th element.

[0076] Using this terminology, in antenna 100b, the phase difference between the signal that excites the nth element and the signal that excites the (n+1)th element is proportional to the distance between the nth element and the (n+1)th element, while the phase difference between the signal that excites the first element and the signal that excites the nth element varies depending on the beam direction.

[0077] Therefore, the phase condition includes the condition that the phase difference between the nth light wave and the (n+1)th light wave is proportional to the distance between the nth element and the (n+1)th element. Here, the nth light wave is one of the N output light waves that have the same input port, and is the output light wave output from the output port of the optical circuit 2 that is connected to the nth element via a photodiode.

[0078] The phase condition is further N to prevent interference between different beams. ｖ Among the individual light waves, the phase difference between the light wave with the smallest phase change given by the optical circuit 112 and the light wave with the largest phase change is 2mπ + θ (where m is n). ｖ N for each input port ｖ The remainders when divided by are predetermined integers that are distinct from each other, and θ is n. ｖThe condition may include the fact that the input ports are all real numbers common to all input ports. In this case, the phase condition also includes the condition that the phase difference between the signal that excites the first element and the signal that excites the Nth element is 2mπ + θ.

[0079] Therefore, if the antenna elements 109 are arranged at equal intervals, the phase difference between all adjacent elements is equal.

[0080] When the antenna elements 109 are arranged at equal intervals, the optical circuit 112 that satisfies all of these phase conditions is, for example, a Butler matrix.

[0081] The optical circuit 112 outputs N ｖ Each of the light waves is incident on a different frequency divider 107. The propagation destinations of the output of each frequency divider 107 in Figure 3 are the same as in Figure 1. That is, each frequency divider 107 is incident on photodiode 108-1 to photodiode 108-N ｈ up to N ｈ It is connected to the photodiode 108.

[0082] Antenna 100b is further equipped with an optical splitter 111 at the end of the optical splitter 110. The optical splitter 111 then splits the light wave into n ｖ The signal is branched in a specific direction. Therefore, antenna 100b can radiate even more types of radio signals than antenna 100a.

[0083] Figure 3 shows the phase shift branching section 113. The phase shift branching section 113 consists of an optical brancher 110 and a delay line 104. The antenna 100c may be equipped with a phase shift branching section 113a, which will be explained in Figure 4, instead of the phase shift branching section 113.

[0084] Figure 4 shows an example of a phase shift branching unit 113a in a modified example. The phase shift branching unit 113a comprises a frequency divider 301 and an optical circuit 302. The frequency divider 301 is an example of a second frequency divider. The optical circuit 302 is an example of a third optical circuit.

[0085] The frequency divider 301 divides the light wave that has been split in the second direction into N in the frequency domain. ｈThis is a frequency divider that divides into individual units. The optical circuit 302 changes the phase of each light wave divided by the frequency divider 301 according to the frequency, and n ｈ This is an optical circuit that branches into individual light waves. The optical circuit 302 is, for example, a Butler matrix.

[0086] <Explanation that the phase shift branching section 113a is an example of a first optical circuit> The delay line 104 is an example of a first optical circuit that gives a phase change according to the frequency to the light wave that has been branched in the second direction, as the light wave is incident on it. Optical circuit 112 is an example of a second optical circuit. Therefore, the second optical circuit is, for example, a Butler matrix.

[0087] The phase shift branching section 113a receives the light wave branched in the second direction and divides it in the frequency domain. Each divided light wave is given a phase change according to its frequency, and n ｈ It is split into individual light waves. In this way, a given frequency f with a phase change corresponding to the frequency is obtained. ｐ The continuous wave of n ｈ The generation of individual particles occurs every p. The phase shift branching section 113a generates a frequency f from the light wave after branching. １ From frequency f Ｎ_ｈ Each continuous wave is combined up to n ｈ It outputs individual light waves. Therefore, the phase shift branching section 113a is n ｂ Although further limited to branching into individual circuits, it is still an example of a first optical circuit, as it provides a phase change according to frequency to the light waves branched in the second direction. The third optical circuit provided in the phase shift branching unit 113a may be, for example, a Butler matrix.

[0088] Note N ｖ ×N ｈ For example, if the antenna element 109 has N ｈ The array antennas, which consist of several elements, are spaced at equal intervals N ｖ They may be arranged so as to be positioned individually. In such cases, the output of the optical circuit 112 is N ｖ Of the individual light waves, the phase change given by the optical circuit 112 is the q-th (where q is 1 or greater than or equal to N).ｖ The difference between a small light wave (less than an integer less than 1) and the (q+1)th smallest light wave is 2nπ / N ｖ That's fine.

[0089] Furthermore, in the above array antenna, N ｈ The antenna elements 109 may be positioned at equal intervals along a predetermined axis, for example. Note that in the examples in Figures 1 and 2, N ｈ The antenna elements 109 may be positioned at equal intervals along a predetermined axis, for example.

[0090] Furthermore, all or part of the functions of antenna 100, antenna 100a, and antenna 100b may be implemented using hardware such as ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), or FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Computer-readable recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. The program may also be transmitted via a telecommunications line.

[0091] Antenna 100, antenna 100a, and antenna 100b are all examples of transmission directivity control devices.

[0092] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention.

[0093] 100, 100a, 100b... Antenna, 101... Optical frequency comb generator, 102... Optical splitter, 103... Frequency converter, 104... Delay line, 105... Modulator, 106, 106a... Optical coupler, 107... Frequency divider, 108... Photodiode, 109... Antenna element, 110... Optical splitter, 111... Optical splitter, 112... Optical circuit, 113, 113a... Phase shift splitter, 301... Frequency divider, 302... Optical circuit

Claims

1. Frequency f １ from the continuous wave of light of frequency f Ｎ_ｈ to the continuous wave of light of frequency f ｈ N ｈ (N １ is a predetermined integer of 2 or more) is a light wave wavelength multiplexed in a state where the continuous waves of N lights are phase-synchronized, and the frequency f Ｎ_ｈ from the frequency f ｈ to the frequency f ｐ of each of the N frequencies f ＲＦ (p is 1 to N_h) are different predetermined frequencies, a generator that generates a light wave that satisfies the above conditions, a first optical splitter that is an optical splitter that branches the output of the generator in two directions, and the frequency of the light wave branched in the first direction, which is one of the two directions, is shifted by a predetermined frequency f ｐ only in a predetermined direction, a first optical circuit that gives a phase change corresponding to the frequency to the light wave branched in the second direction, which is a direction different from the first direction among the two directions, a modulator that modulates the light wave propagated through the first optical circuit, an optical coupler that obtains a composite wave of the output of the frequency converter and the output of the modulator, and from the output of the optical coupler, the f p-band wave, which is the modulated wave having the center frequency f ｐ included in the output of the modulator, and the continuous wave whose frequency is shifted by f ＲＦ only, a first frequency divider that obtains a p-th pair wave, which is a composite wave, for each p, a p-th photodiode that receives the p-th pair wave, and a p-th antenna element that is an antenna element excited by the output of the p-th photodiode. A transmission directivity control device comprising:

2. The light waves branched in the aforementioned two directions are n ｈ Direction (n ｈ is 1 or more N ｈ The system further comprises a second optical splitter, which is an optical splitter that branches to the following predetermined integers, n ｈ The light waves propagating in the direction pass through the first optical circuit and the modulator, which are different from each other, and are incident on the same optical coupler, and the output of the optical coupler is incident on the first frequency divider, and the p-p pair wave is n ｈ Each of the above modulators outputs f ｐ Bandwidth and frequency f ｐ f ＲＦ The transmission directivity control device according to claim 1, wherein the combined wave is a continuous wave with a frequency shift of only one degree.

3. The incoming light wave is n ｖ Direction (n ｖ is 1 or greater N ｖ The following integer: N ｖ A third optical splitter that branches into a predetermined integer of 1 or more, and n ｖ The phase of the light wave incident from the direction is changed, and the phase condition is satisfied N ｖ The system further comprises a second optical circuit that branches into individual light waves, wherein the phase condition is N ｖ The condition includes that the phase difference between any two of the aforementioned light waves is proportional to the distance between the two corresponding antenna elements, the third optical splitter exists for each of the first optical circuits, the light wave incident on the third optical splitter is the light wave that has propagated through the first optical circuit, the modulator exists for each branch by the third optical splitter, and N = n ｈ ×n ｖ The modulators have n elements. ｈ n is ｖ Each element is pre-classified to belong to only one of the sets, where N = n ｈ ×n ｖ The outputs of the modulators belonging to the same classification set are incident on the same optical coupler, and the outputs of the modulators belonging to different classification sets are incident on different optical couplers, and the output of the second optical circuit is N ｖ The transmission directivity control device according to claim 2, wherein each of the light waves is incident on a different first frequency divider.

4. The incoming light wave is n ｖ Direction (n ｖ is 1 or greater N ｖ The following integer: N ｖ A third optical splitter that branches into a predetermined integer of 1 or more, and n ｖ A light wave incident from a certain direction has a phase difference of N ｖ The first optical circuit further comprises a second optical circuit that converts the light waves branched in the second direction into N in the frequency domain. ｈ A second frequency divider divides the light waves into individual units, and the phase of each light wave divided by the second frequency divider is changed according to the frequency, and n ｈ The system comprises a third optical circuit that branches into individual light waves, the third optical brancher exists for each output of the first optical circuit, the light wave incident on the third optical brancher is a light wave branched by the first optical circuit, and the modulator exists for each branch by the third optical brancher, N=n ｈ ×n ｖ The modulators have n elements. ｈ n is ｖ Each element is pre-classified to belong to only one of the sets, where N = n ｈ ×n ｖ The outputs of the modulators belonging to the same classification set are incident on the same optical coupler, and the outputs of the modulators belonging to different classification sets are incident on different optical couplers, and the output of the second optical circuit is N ｖ The transmission directivity control device according to claim 2, wherein each of the light waves is incident on a different first frequency divider.

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