JP2022040904A - Beam control device - Google Patents

Abstract

To provide a technique for suppressing an increase in the bandwidth of an optical signal transmitted from a control site.SOLUTION: A beam control device includes determining means that determines the phase of each of a plurality of modulated signals and a plurality of sine wave signals, phase control means that controls the phase of each of the plurality of modulated signals and the plurality of sine wave signals according to the determination of the determination means, and generation means that generates an optical signal including a plurality of modulated light beams corresponding to the plurality of modulated signals and a plurality of optical tone signals corresponding to the plurality of sine wave signals, in which modulated light beams and optical tone signals are alternately arranged at equal intervals in a frequency region, on the basis of the plurality of modulated signals and the plurality of sine wave signals after phase control, and the determination means pairs one optical tone signal and one modulated light beam adjacent in the frequency region in the optical signal, and determines the phase of each of the plurality of modulated signals and the plurality of sinusoidal signals such that the phase of each electric signal obtained by photoelectric conversion of each pair of signals included in the optical signal becomes a target value.SELECTED DRAWING: Figure 3

Description

The present invention relates to a technique for controlling a transmission beam from a site different from an antenna site that transmits a radio signal.

Beamforming technology that electrically controls the beam of a radio signal transmitted from a plurality of antennas (or one array antenna having a plurality of antenna elements) is used in wireless communication. For beamforming, the radio frequency modulation signal (electrical signal) that carries the information is branched by the number of antennas. The desired beam is formed by adjusting the phase (or amplitude and phase) of each modulated signal after branching and transmitting as a radio signal from the corresponding antenna.

Non-Patent Document 1 to Non-Patent Document 3 are sites different from the antenna site without providing a device for independently controlling the phase of each modulated signal at the antenna site where the antenna is installed and the radio signal is transmitted / received. Hereinafter, the configuration for controlling the transmission beam from the control site) is disclosed. FIG. 1 is an explanatory diagram of a beam control configuration disclosed in Non-Patent Documents 1 to 3. In FIG. 1, it is assumed that six antennas are installed at the antenna site.

The control site transmits the optical signal shown in FIG. 1 to the antenna site. The optical signal is a frequency-multiplexed (wavelength-multiplexed) of six optical tone signals (continuous light) and six modulated lights. In FIG. 1, an arrow indicates an optical tone signal, and a quadrangle indicates a modulated light. Each of the six modulated lights is a continuous light modulated by the same modulation method by the same electric signal carrying the same information. For example, the six modulated lights can be generated by frequency-converting each of the same modulated lights to a different frequency. One modulated light is associated with one optical tone signal to form a pair. In this example, there are 6 pairs # 1 to # 6 corresponding to the 6 antennas at the antenna site. The frequency difference between the optical tone signal in the same pair and the center frequency of the modulated light is the same value (fm in this example).

At the antenna site, the frequency of the optical signal shown in FIG. 1 is separated, the optical signal corresponding to each pair is taken out, and each optical signal is individually photoelectrically converted. By photoelectric conversion of an optical signal including one optical tone signal and one modulated light, a modulated signal (electric signal) corresponding to the modulated light can be obtained. The center frequency of this modulated signal is the difference between the optical tone signal in the pair and the center frequency of the modulated light. That is, in the example of FIG. 1, the center frequencies of the six modulated signals obtained by photoelectric conversion of each of the six optical signals corresponding to the six pairs are all the same fm. By setting fm to the frequency of the radio frequency band, each modulated signal becomes a signal of the radio frequency band. That is, FIG. 1 is also a so-called RoF (Radio over Fiber) system. Therefore, the modulated signal obtained by photoelectric conversion is amplified and then transmitted as a radio signal from the corresponding antenna. Here, the phase of the modulated signal obtained by photoelectric conversion of the optical signal including the pair changes depending on the phase of the optical tone signal. Therefore, by controlling the phase of each optical tone signal at the control site, the transmission beam can be controlled from the control site.

Hiroshi Takahashi, "Phase Shift Method for High Frequency Signals Using Optical Phase Control in RoF Transmission", Institute of Electronics, Information and Communication Engineers Society Conference, C-3-23, 2019, September 12, 2019 Hiroshi Takahashi, "Phase Shift Method of High Frequency Signals in RoF Transmission Using Optical Phase Control", Microwave / Millimeter Wave Photonics Study Group, MWP2019-42, November 27, 2019 S. Akiba, et. al. , "Photonic Architecture for Beam Forming of RF Phased Array Antenna", in Optical Fiber Communication Connection, OSA Technical Digital Digital Digital Digital (online) 51

Currently, the number of antennas used in beamforming technology is increasing in order to finely control the beam. In the configurations of Non-Patent Documents 1 to 3, as the number of antennas increases, the bandwidth required for the optical transmission line connecting the control site and the antenna site increases. However, since there is an upper limit to the bandwidth of the optical transmission line connecting the control site and the antenna site, it is necessary to suppress an increase in the bandwidth of the optical signal transmitted from the control site.

The present invention provides a technique for suppressing an increase in the bandwidth of an optical signal transmitted from a control site.

According to one aspect of the present invention, a beam control device that controls a transmission beam formed by transmitting an electric signal as a radio signal from a plurality of antennas determines the phase of each of a plurality of modulated signals and a plurality of sinusoidal signals. The determination means, the phase control means for controlling the phase of each of the plurality of modulated signals and the plurality of sinusoidal signals according to the determination of the determination means, the plurality of modulated signals after phase control by the phase control means, and the said. An optical signal including a plurality of modulated lights corresponding to the plurality of modulated signals and a plurality of optical tone signals corresponding to the plurality of sine wave signals based on the plurality of sine wave signals, and the modulated light in the frequency region. And the generation means for generating the optical signal in which the optical tone signals are alternately arranged at equal intervals, and the determination means is one optical tone signal and one modulated light adjacent to each other in the frequency region in the optical signal. The phases of the plurality of modulated signals and the phases of the plurality of sinusoidal signals so that the phase of each of the electric signals obtained by photoelectric conversion of the signals of each pair included in the optical signal becomes a target value. It is characterized by determining.

According to the present invention, it is possible to suppress an increase in the bandwidth of an optical signal transmitted from a control site.

Explanatory drawing of background technology. FIG. 6 shows an optical signal transmitted by a beam control device at a control site to a radio device at an antenna site according to an embodiment. The block diagram of the beam control apparatus by one Embodiment. A block diagram of a wireless device according to an embodiment.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. It should be noted that the following embodiments do not limit the invention according to the claims, and not all combinations of features described in the embodiments are essential to the invention. Two or more of the plurality of features described in the embodiments may be arbitrarily combined. In addition, the same or similar configuration will be given the same reference number, and duplicated explanations will be omitted.

FIG. 2 shows an optical signal transmitted by the beam control device according to the present embodiment to the wireless device. The wireless device is installed at the antenna site, and the beam control device is installed at the control site at a place different from the antenna site. The RoF system according to the present embodiment controls the transmission beam from the control site without providing a device for individually controlling the phase of the modulated signal supplied to each antenna at the antenna site. Note that FIG. 2 shows a case where the wireless device at the antenna site has six antennas and a beam is formed by the six antennas, as in FIG. 1.

The optical signal is one in which four optical tone signals (continuous light) 51 to 54 and three modulated lights 61 to 63 are alternately arranged in the frequency domain. The difference between the optical tone signal and the center frequency of the adjacent modulated light is the same fm. That is, the optical tone signal and the modulated light are alternately arranged at equal intervals in the frequency domain. In addition, fm is a frequency of the radio frequency band. Also in this embodiment, the modulated light is associated with the adjacent optical tone signal to form a pair. However, in the present embodiment, the modulated light in which both the optical tone signal adjacent to each other on the low frequency side and the optical tone signal adjacent to each other on the high frequency side are present is the optical tone signal on the low frequency side and the optical tone signal on the high frequency side. Form a pair with each. That is, such modulated light belongs to each of the two pairs. Therefore, in the example of FIG. 2, as shown in the figure, six pairs # 1 to # 6 are formed corresponding to the six antennas of the radio device at the antenna site. Although not present in FIG. 2, the modulated light in which only one of the adjacent optical tone signal on the low frequency side and the adjacent optical tone signal on the high frequency side exists is paired with only one adjacent optical tone signal. Form. Such modulated light will belong to only one pair.

The radio device at the antenna site performs frequency separation of the optical signals shown in FIG. 2, extracts the optical signals corresponding to each pair, and performs photoelectric conversion of each optical signal individually. By photoelectric conversion of an optical signal including one optical tone signal and one modulated light, a modulated signal (electric signal) corresponding to the modulated light can be obtained. The center frequency of this modulated signal is the difference between the optical tone signal in the pair and the center frequency of the modulated light. That is, in the example of FIG. 2, the center frequencies of the six modulated signals obtained by photoelectric conversion of each of the six optical signals corresponding to the six pairs are all the same fm. The wireless device performs amplification, filtering, and the like on these six modulated signals, and outputs the processed modulated signal to the corresponding antenna. If the phases of the six modulated signals can be individually controlled from the control site, the transmitted beam can be controlled from the control site without providing a device for independently adjusting the phase of each modulated signal in the wireless device.

Here, in the configuration of FIG. 1, the optical tone signal and the modulated light belong to only one pair, and therefore each pair is independent. Therefore, the phase of each modulated signal obtained at the antenna site is arbitrarily controlled by arbitrarily adjusting the phase of the optical tone signal in the pair at the control site while keeping the phase of the modulated light of each pair the same. It was possible. However, in the configuration of this embodiment, there are optical tone signals or modulated light belonging to a plurality of pairs. For example, in the configuration of FIG. 2, the optical tone signal 52 belongs to both pair # 2 and pair # 3. Therefore, assuming that the phases of the modulated signals 61 to 63 are the same as in the configuration of FIG. 1, the modulated signal obtained by photoelectric conversion of the optical signal corresponding to pair # 2 and the optical signal corresponding to pair # 3 The modulation signals obtained by photoelectric conversion of the above are both determined only by the phase of the optical tone signal 52 and are the same. Therefore, in the configuration of FIG. 2, it is necessary to control the phase of the modulated light 61 to 63 according to the transmission beam. Hereinafter, a specific description will be given.

First, the phases of the optical tone signals 51 to 54 are set to θ ₅₁ to θ ₅₄ , the phases of the modulated lights 61 to 63 are set to θ ₆₁ to θ ₆₃ , and the modulated signals obtained by photoelectric conversion of pairs # 1 to pair # 6 are obtained. Modulated signals # 1 to # 6. In this case, the phases θ _{# 1} to θ _{# 6} of the modulation signals # 1 to # 6 are given by the following equations (1) to (6).
θ _{# 1} = θ ₆₁ -θ ₅₁ (1)
θ _{# 2} = θ ₅₂ -θ ₆₁ (2)
θ _{# 3} = θ ₆₂ -θ ₅₂ (3)
θ _{# 4} = θ ₅₃ -θ ₆₂ (4)
θ _{# 5} = θ ₆₃ -θ ₅₃ (5)
θ _{# 6} = θ ₅₄ -θ ₆₃ (6)
The phases θ _{# 1} to θ _{# 6} are values determined by the transmitted beam to be formed, that is, target values for forming a desired transmitted beam, and are therefore known to the beam control device. Further, since the phases θ _{# 1} to θ _{# 6} are determined by the phase difference between the optical tone signal and the modulated light, one of the phases θ ₅₁ to θ ₅₄ and the phases θ ₆₁ to θ ₆₃ is an arbitrary phase. be able to. That is, for example, the beam control device can arbitrarily determine the value of the phase θ ₅₁ . Then, there are a total of six unknowns, that is, phases θ ₅₂ to θ ₅₄ and phases θ ₆₁ to θ ₆₃ , and since there are six equations, the beam control device has a phase θ _{# 1} to form a desired transmission beam. Based on θ _{# 6} and the arbitrarily determined phase θ ₅₁ , the values of the phases θ ₅₂ to θ ₅₄ and the phases θ ₆₁ to θ ₆₃ can be determined.

When the number of antennas is 7, for example, the modulated light is arranged on the low frequency side of the optical tone signal 51 or on the high frequency side of the optical tone signal 54 to form pair # 7. More generally, assuming that the number of antennas is M (M is an integer of 2 or more), when M is an even number, the number of optical tone signals is M / 2 + 1, and the number of modulated lights is M / 2. When M is an odd number, the number of optical tone signals and modulated light is both (M + 1) / 2. When M is an even number, the number of optical tone signals may be M / 2, and the number of modulated lights may be M / 2 + 1. That is, the optical tone signal of FIG. 2 and the modulated light can be reversed. However, the bandwidth of the optical signal transmitted by the beam control device is narrower when arranged as shown in FIG.

FIG. 3 is a configuration diagram of a beam control device according to the present embodiment. In the following description, the number of optical tone signals included in the optical signal transmitted by the beam control device to the wireless device is _NT , the number of modulated lights is NM, and the number of pairs is _M. The branching unit 14 branches the modulation signals (electrical signals) that carry information received from a modulation unit (not shown) of another device or beam control device into _NM pieces, and outputs each to the phase control unit 15. Each of the _NM modulated signals corresponds to the _NM modulated light contained in the optical signal. Further, the local oscillation unit 12 generates a sine wave signal (electrical signal) and outputs it to the branch unit 13. The branching unit 13 branches the sine wave signal into _NT pieces, and outputs each to the phase control unit 15. Each of the _NT sine wave signals corresponds to the _NT optical tone signals included in the optical signal.

The control unit 11 determines the phase of each optical tone signal and the phase of each modulated light as described above according to the transmitted beam to be formed. The transmitted beam to be formed may be fixed or dynamically changing. When the transmitted beam to be formed is fixed, information indicating the transmitted beam is set in the control unit 11. When the transmitted beam to be formed changes dynamically, for example, information specifying the transmitted beam to be formed is input to the control unit 11 from a device (not shown). For example, in a mobile communication system or the like, a transmission beam is designated, for example, in the form of PMI from a UE that is a communication partner of a wireless device, and the designated transmission beam is input to the control unit 11. When the transmitted beam to be formed changes dynamically, the control unit 11 determines the phase of each optical tone signal and the phase of each modulated light each time the transmitted beam changes. The phase of each optical tone signal and the phase of each modulated light are also the phases of the corresponding sine wave signal and the corresponding modulated signal. The control unit 11 notifies the phase control unit 15 of the phase of each determined optical tone signal and each modulated light, that is, the phase of each sine wave signal and each modulated signal.

The phase control unit 15 controls the phase of each of the _NT sine wave signal and the NM modulated signal according to the notification from the control unit 11, and converts each of the phase-controlled _sine wave signal and the modulated signal into a frequency conversion unit. Output to 16. The frequency conversion unit 16 frequency-converts each of the _NT sine wave signal and the _NM -modulated signal according to the arrangement of the optical tone signal and the modulated light in the optical signal as shown in FIG. 2, and the frequency-converted sine wave signal. The wave signal and the modulated signal are output to the frequency multiplexing unit 17. The frequency multiplexing unit 17 outputs a frequency-multiplexed signal obtained by frequency-multiplexing an _NT sine wave signal and an _NM -modulated signal to the optical modulation unit 18. The optical modulation unit 18 has a light source that generates continuous light, and modulates the continuous light with the frequency multiplexing signal from the frequency multiplexing unit 17 to generate an optical signal as shown in FIG. The optical signal is transmitted to the wireless device at the antenna site after processing such as amplification.

FIG. 4 is a configuration diagram of a wireless device according to the present embodiment. The antenna unit 23 has M antennas. The frequency separation unit 21 receives an optical signal as shown in FIG. 2 from the beam control device, frequency-separates each pair, and outputs an optical signal corresponding to each pair to the photoelectric conversion unit 22. That is, the frequency separation unit 21 outputs an optical signal including one optical tone signal and one modulated light corresponding to each of the M pairs. For example, a coupler that splits an optical signal as shown in FIG. 2 into two, and a frequency separator that extracts an odd-numbered pair (pairs # 1, # 3, and # 5 in FIG. 2) from one of the optical signals. The frequency separator 21 can be configured by a frequency separator that takes out even-numbered pairs (pairs # 2, # 4, and # 6 in FIG. 2) from the other.

The photoelectric change conversion unit 22 individually photoelectrically converts the optical signals corresponding to each pair. Therefore, the photoelectric conversion unit 22 outputs M modulated signals to the corresponding antenna of the antenna unit 23. The M modulation signals correspond to the modulation signals input to the beam control device, and the phase thereof is a value (target value) for forming a desired transmission beam. Therefore, a radio signal is transmitted from the antenna unit 23 with a desired transmission beam.

Although not shown, an amplification unit and a filter unit are provided between the photoelectric conversion unit 22 and the antenna unit 23. Here, when the amplitude of each modulated signal is made different for the formation of the transmission beam, the modulated signal can be individually amplified by an amplification unit (not shown). The gain of the modulated signal in each amplification unit is notified by, for example, a control line (not shown) from the control unit 11 of the beam control device. Further, by adjusting the amplitudes of the optical tone signal and the modulated light, the amplitude of the modulated signal output by the photoelectric conversion unit 22 can be adjusted. The method for determining the amplitude of each optical tone signal and each modulated light is the same as the method for determining the phase described above. That is, a function for controlling the amplitude is added to the phase control unit 15 in FIG. 3 to form an amplitude phase control unit. Then, the control unit 11 of the beam control device also increases the amplitude of each sinusoidal signal and each modulated signal so that the amplitude of the signal obtained by photoelectric conversion of the signal corresponding to each pair at the antenna site becomes a desired value. Determine and notify the amplitude phase control unit. Then, the amplitude phase control unit controls each sine wave signal and each modulation signal so as to have the phase and amplitude notified from the control unit 11. In this case, in the wireless device, the gain of the amplification unit that amplifies each modulated signal can be the same, and the control unit 11 does not need to notify the wireless device of the gain.

In the present embodiment, when M is an even number and the number of optical tone signals is larger than that of the modulated light as shown in FIG. 2, the bandwidth required for the optical signal transmitted from the control site is fm ×. It becomes M. When M is an odd number and the bandwidth of the modulated light is 2 W (W <fm), the bandwidth required for the optical signal transmitted from the control site is fm × M + W. On the other hand, in the configuration of FIG. 1, assuming that the guard band between the pairs is G, the bandwidth required for the optical signal transmitted from the control site is fm × M + (G + W) × (M-1). Therefore, when M is an even number, the bandwidth of the optical signal transmitted from the control site can be reduced by (G + W) × (M-1). Further, when M is an odd number, the bandwidth of the optical signal transmitted from the control site can be reduced by (G + W) × (M-1). When M is an even number and the number of optical tone signals is smaller than that of the modulated light, the band increases by 2 W as compared with the case where the number of optical tone signals is larger than that of the modulated light. Bandwidth can be reduced at M = 4 and above.

In the present embodiment, the beam control device branches the modulated signal received from the external device or the internally generated modulated signal at the branch portion 14. However, when the modulation signal is generated in the beam control device based on the information to be carried, it is also possible to individually generate _NM modulation signals based on the information to be carried. Further, in the present embodiment, the beam control device generates one sine wave signal at the local oscillation unit 12 and branches at the branch unit 13. However, it is also possible to generate _NT sinusoidal signals by the individual local oscillators 12.

The invention is not limited to the above embodiment, and various modifications and changes can be made within the scope of the gist of the invention.

11: Control unit, 15: Phase control unit, 18: Optical modulation unit

Claims (7)

A beam control device that controls a transmission beam formed by transmitting an electric signal as a radio signal from a plurality of antennas.
Determining means for determining the phase of each of a plurality of modulated signals and a plurality of sine wave signals,
A phase control means that controls the phase of each of the plurality of modulated signals and the plurality of sine wave signals according to the determination of the determination means.
Based on the plurality of modulated signals and the plurality of sine wave signals after phase control by the phase control means, a plurality of modulated lights corresponding to the plurality of modulated signals and a plurality of lights corresponding to the plurality of sine wave signals. An optical signal including a tone signal, which is a generation means for generating the optical signal in which modulated light and optical tone signals are alternately arranged at equal intervals in a frequency region.
Equipped with
The determining means is a pair of one optical tone signal and one modulated light adjacent to each other in the frequency region in the optical signal, and each of the electric signals obtained by photoelectric conversion of each pair of signals included in the optical signal. A beam control device comprising determining the phase of each of the plurality of modulated signals and the plurality of sinusoidal signals so that the phase becomes a target value. The beam control device according to claim 1, wherein the target value of the phase of each of the electric signals obtained by photoelectric conversion of each pair of signals is determined based on the transmission beam. When the number M (M is an integer of 2 or more) of the plurality of antennas is an even number, the number of one of the plurality of modulated lights and the plurality of optical tone signals is M / 2 + 1, and the number of the other is M. / 2 and
The claim is characterized in that when the number M (M is an integer of 2 or more) of the plurality of antennas is an odd number, the number of the plurality of modulated lights and the plurality of optical tone signals are both (M + 1) / 2. The beam control device according to 1 or 2. The determining means is adjacent to the modulated light and the modulated light on the high frequency side for the modulated light in which the optical tone signal adjacent to both the high frequency side and the low frequency side is arranged among the plurality of modulated lights. One of claims 1 to 3, wherein the optical tone signal to be used is one pair, and the modulated light and an optical tone signal adjacent to the modulated light on the low frequency side are paired. Beam control device according to the section. The beam control device according to any one of claims 1 to 4, further comprising means for generating the plurality of sine wave signals. The beam control device according to any one of claims 1 to 5, further comprising means for generating the plurality of modulated signals by branching a modulated signal that carries information. The generation means includes a frequency conversion means for frequency-converting the plurality of modulated signals and the plurality of sine wave signals after phase control by the phase control means to different frequencies.
A frequency multiplexing means that frequency-multiplexes the plurality of modulated signals and the plurality of sine wave signals after frequency conversion by the frequency converting means and outputs a frequency-multiplexed signal.
An optical modulation means that generates an optical signal by modulating continuous light based on a frequency division signal output by the frequency multiplexing means, and an optical modulation means.
The beam control device according to any one of claims 1 to 6, wherein the beam control device is provided.

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