Signal processor, RoF transceiver, fiber radio system and signal processing method

Abstract

A signal processor provided in a transceiver for transmitting and receiving radio signals is provided, and includes a branching unit, a detection unit, a determination unit, and a power controller. The branching unit branches a transmission signal and acquires a branched signal. The detection unit detects the branched signal and acquires a voltage value of the branched signal. The determination unit compares the voltage value of the branched signal with a threshold voltage previously stored in a storage unit, and determines whether the voltage value of the branched signal is equal to or greater than the threshold voltage. The power controller controls turning on and off of a power supply of a reception signal amplifier of the transceiver according to a determination result determined by the determination unit.

Description

Technical Field

[0001] This invention relates to signal processors, RoF transceivers, fiber optic radio systems, and signal processing methods. Background Technology

[0002] Fiber Optic Radio (RoF) technology for transmitting and receiving radio signals via fiber optic transmission lines has been proposed as a means of relaying and transmitting radio signals to distant locations. In this RoF radio, so-called signal roundabout can occur, where a portion of the signal transmitted from the transmitting antenna is reflected or otherwise input directly or indirectly to the receiving antenna at the same frequency. Patent document JP2019-153945A discloses a roundabout signal remover for preventing signal quality degradation due to roundabout fiber optic radio signals. The roundabout signal remover disclosed in JP2019-153945A returns a portion of the signal transmitted from the transmitter as a suppression signal to the receiving side and combines it with the already roundabout received signal, thereby suppressing transmission. Summary of the Invention

[0003] In the bypass signal remover disclosed in patent document JP2019-153945A, it is necessary to monitor the level and delay time of the bypass signal separately, and a delay circuit also needs to be set according to the frequency. That is to say, in conventional bypass signal removers, the circuit size and amount of computation become huge, which increases the cost and further leads to delays associated with signal processing.

[0004] The purpose of this invention is to provide a signal processor that can suppress bypass signals with a simple configuration.

[0005] The signal processor of the present invention is a signal processor disposed in a transceiver for transmitting and receiving radio signals, and includes: a branching unit that branches the transmitted signal and acquires the branched signal; a detection unit that detects the branched signal and acquires the voltage value of the branched signal; a determination unit that compares the voltage value of the branched signal with a threshold voltage previously stored in a storage unit and determines whether the voltage value of the branched signal is equal to or greater than the threshold voltage; and a power controller that controls the power supply of the transceiver's receiving signal amplifier according to the determination result determined by the determination unit.

[0006] The RoF transceiver of the present invention is a RoF (Optical Fiber Radio) transceiver used for relaying and transmitting radio signals via optical fiber transmission lines in radio communication between a base station and a terminal. The RoF transceiver includes: an antenna unit for transmitting and / or receiving radio signals; a first amplifier for amplifying the received signal and generating a first electrical signal; an electro-optic converter for converting the first electrical signal amplified by the first amplifier into an optical transmission signal and transmitting the optical transmission signal to the optical fiber transmission line; an opto-converter for converting the optical received signal received via the optical fiber transmission line into a second electrical signal; a second amplifier for amplifying the second electrical signal and generating a transmission signal; and a signal processor for inputting the transmission signal amplified by the second amplifier. The signal processor includes: a branching unit for branching the transmission signal and acquiring the branched signal; a detection unit for detecting the branched signal and acquiring its voltage value; a determination unit for comparing the voltage value of the branched signal with a threshold voltage pre-stored in a storage unit and determining whether the voltage value of the branched signal is equal to or greater than the threshold voltage; and a power controller for controlling the power supply to the first amplifier based on the determination result determined by the determination unit.

[0007] The fiber optic radio system of the present invention includes a first transceiver that performs radio communication with a base station and a second transceiver that performs radio communication with a terminal. The first transceiver is the aforementioned RoF transceiver, and the second transceiver is the aforementioned RoF transceiver. The first transceiver and the second transceiver are connected via an optical fiber transmission line.

[0008] The signal processing method of the present invention is a computer-executable signal processing method, which includes the steps of: transmitting a branch signal and acquiring the branch signal; detecting the branch signal and acquiring the voltage value of the branch signal; comparing the voltage value of the branch signal with a threshold voltage pre-stored in a storage unit and determining whether the voltage value of the branch signal is equal to or greater than the threshold voltage; and controlling the power supply of the receiving signal amplifier to be turned on and off according to the determined result. Attached Figure Description

[0009] Figure 1 This is a diagram illustrating the configuration of the fiber optic radio system according to this embodiment.

[0010] Figure 2 This is a diagram illustrating the functional configuration of the signal processor in this embodiment.

[0011] Figure 3A This is a diagram used to illustrate the transmission signal of this embodiment.

[0012] Figure 3B This is a diagram used to illustrate the envelope of the transmitted signal in this embodiment.

[0013] Figure 4 This is a diagram illustrating the relationship between the input power and the output voltage of the fiber optic radio system according to this embodiment.

[0014] Figure 5 This is a diagram used to illustrate the basic propagation loss in free space in the fiber optic radio system according to this embodiment.

[0015] Figure 6 This is a flowchart illustrating an example of processing in a signal processor according to this embodiment. Detailed Implementation

[0016] Different embodiments will be described below with reference to the accompanying drawings.

[0017] The fiber optic radio system 10 according to this embodiment will now be described in detail with reference to the accompanying drawings. The dimensional ratios in the drawings have been enlarged for ease of interpretation and may sometimes differ from the actual ratios. In the following drawings, identical or similar components are indicated by identical or similar symbols.

[0018] (Overview of Fiber Optic Radio System 10)

[0019] Figure 1 This is a diagram illustrating the configuration of the fiber optic radio system 10 according to this embodiment. The fiber optic radio system 10 includes a first transceiver 12a, a second transceiver 12b, and a fiber optic transmission line 11.

[0020] exist Figure 1 In the illustrated fiber optic radio system 10, radio signals transmitted by base station 20 are received by first transceiver 12a at antenna unit 200, and the first transceiver 12a converts the radio signals into optical signals. The optical signals converted by the first transceiver 12a are transmitted to a second transceiver 12b via fiber optic transmission line 11. In the fiber optic radio system 10, the first transceiver 12a and the second transceiver 12b are located a certain distance from each other and are capable of long-distance communication. The second transceiver 12b converts the optical signals received via fiber optic transmission line 11 into electrical signals and further transmits them as radio signals to terminal 30, such as a portable terminal (mobile terminal).

[0021] In the fiber optic radio system 10, the radio signal transmitted by the terminal 30 is received by the second transceiver 12b at the antenna unit 200, and the second transceiver 12b converts the radio signal into an optical signal. The optical signal converted by the second transceiver 12b is transmitted to the first transceiver 12a via the fiber optic transmission line 11. The first transceiver 12a converts the optical signal received via the fiber optic transmission line 11 into an electrical signal, and further transmits it as a radio signal to the base station 20.

[0022] In other words, the fiber optic radio system 10 is a system used for relaying and transmitting communications between the base station 20 and the terminal 30. Furthermore, the fiber optic radio system 10 is a RoF (Radio over Fiber) system used for transmitting radio signals (RF signals) over a certain distance via the fiber optic transmission line 11. As a RoF system, the fiber optic radio system 10 carries high-frequency radio signals on the optical fiber, thus enabling long-distance transmission. The fiber optic radio system 10 can utilize the advantages of low loss and broadband optical fiber characteristics to transmit radio waves to areas where radio waves do not directly reach (dead zones).

[0023] In a typical RoF system, a portion of the electrical power of the radio signal transmitted from antenna element 200 is returned via antenna element 200, and thus, in some cases, a signal loop is generated and oscillations occur. In a typical RoF system, oscillations can occur not only through the signal loop mediated by antenna element 200, but also through, for example, the signal loop from circulator 300 to first amplifier 410. The fiber optic radio system 10 according to this embodiment includes a signal processor 100 for preventing such oscillations.

[0024] (Configuration of RoF transceiver 12)

[0025] Next, the signal processor 100 of this embodiment will be described. For example... Figure 1 As shown, the signal processor 100 is disposed in the first transceiver 12a and the second transceiver 12b. Note that in this embodiment, it is assumed that the first transceiver 12a and the second transceiver 12b have the same configuration. Unless otherwise explained, the first transceiver 12a and the second transceiver 12b are referred to below as "RoF transceiver 12".

[0026] The RoF transceiver 12 includes a signal processor 100, an antenna unit 200, a circulator 300, a first amplifier 410, a second amplifier 420, an electro-optical converter 500 (E / O converter), and an optoelectronic converter 600 (O / E converter). The signal processor 100 will be described in detail later.

[0027] Antenna element 200 is used to transmit and receive radio signals. Antenna element 200 converts electrical signals into radio signals or radio signals into electrical signals.

[0028] The circulator 300 switches between transmitting and receiving radio signals transmitted via the antenna unit 200 and receiving radio signals via the antenna unit 200. That is, when receiving radio signals, the radio signals (received signals) are transmitted to the first amplifier 410 via the circulator 300. Conversely, when transmitting radio signals, the radio signals (transmitted signals) from the second amplifier 420 are transmitted to the antenna unit 200 via the circulator 300 and transmitted from the antenna unit 200.

[0029] In other words, the use of circulator 300 enables the transmission and reception of radio signals via antenna unit 200. Note that this embodiment has a configuration including antenna unit 200 and circulator 300, but this configuration does not limit the configuration of the embodiment. For example, RoF transceiver 12 may include separate transmit and receive antennas without circulator 300. In this case, it is assumed that the receive antenna is connected to the first amplifier 410 of RoF transceiver 12, and that the transmit antenna is connected to the second amplifier 420 via branch unit 111 of signal processor 100 of RoF transceiver 12 (see...). Figure 2 ).

[0030] The first amplifier 410 amplifies the radio signals received via the antenna unit 200 and the circulator 300. In this embodiment, the first amplifier 410 is made of a general-purpose amplifier (high-frequency amplifier, RF amplifier). The first amplifier 410 is capable of turning the signal amplification function on and off (enabling and disabling) using a voltage supplied from a power supply circuit (not shown). Note that the signal generated by amplification at the first amplifier 410 corresponds to a first electrical signal. A receiving signal amplifier corresponds to the first amplifier 410.

[0031] The electro-optic converter 500 converts the electrical signal amplified by the first amplifier 410 into an optical signal and transmits the optical signal to the optical fiber transmission path 11. Note that the optical signal sent from the electro-optic converter 500 to the optical fiber transmission line 11 corresponds to the optical transmission signal.

[0032] The photoelectric converter 600 converts the optical signal received via the optical fiber transmission line 11 into an electrical signal. Note that the optical signal received by the photoelectric converter 600 from the optical fiber transmission line 11 corresponds to the optical received signal. The electrical signal converted by the photoelectric converter 600 corresponds to the second electrical signal.

[0033] The second amplifier 420 amplifies the electrical signal converted by the photoelectric converter 600. In this embodiment, the second amplifier 420 is made of a general-purpose amplifier (high-frequency amplifier, RF amplifier).

[0034] (Configuration of Signal Processor 100)

[0035] Next, the signal processor 100 will be described in detail. Figure 2 yes Figure 1 This is an enlarged schematic diagram of the second transceiver 12b, and a block diagram showing the configuration of the signal processor 100 in the second transceiver 12b. Figure 2 As shown, the signal processor 100 includes a controller 110 and a storage unit 120.

[0036] The controller 110 can be configured as, for example, a general-purpose microcomputer. In this case, the microcomputer may have a computer program installed for use as the signal processor 100. By executing the computer program, the microcomputer acts as a multiplexing circuit configured in the signal processor 100. The controller 110 can implement the multiplexing circuit configured in the signal processor 100 using software, or the information processing circuit can be constructed by preparing dedicated hardware. The multiplexing circuit can be constructed by separate hardware.

[0037] For example, storage cell 120 can be ROM (Read-Only Memory), RAM (Random Access Memory), hard disk, etc. Storage cell 120 pre-stores threshold voltages, which will be described later.

[0038] (Functions of Signal Processor 100)

[0039] like Figure 2 As shown, the controller 110 of the signal processor 100 includes a branch unit 111, a detection unit 112, a decision unit 113, and a power controller 114 according to its functions.

[0040] Branch unit 111 branches the transmitted signal and acquires the branched signal. The branched signal acquired by branch unit 111 has a power level corresponding to the branch ratio of the transmitted signal. In this embodiment, branch unit 111 is made of, for example, a coupler. The branch ratio is a value determined based on the characteristics of branch unit 111 applied to signal processor 100.

[0041] The detection unit 112 performs envelope detection on the branch signal extracted by the branch unit 111 and calculates the signal level. Figure 3A and Figure 3B These are schematic diagrams illustrating the input signal and envelope detection. Note that for illustrative purposes, they have been simplified. Figure 3A and 3B The input signal shown is assumed to have complex amplitude by the fiber optic radio system 10.

[0042] Figure 3A An example of a branch signal extracted by branch unit 111 is shown. Detection unit 112 calculates... Figure 3AThe envelope of the branch signal is shown, and the electrical power (signal level) of the branch signal is calculated based on the calculated envelope.

[0043] The detection unit 112 calculates the voltage value based on the electrical power (signal level) of the branch signal. Specifically, the detection unit 112 calculates the voltage value based on, for example, the electrical power (signal level) of the branch signal. Figure 4 The voltage value of the branch signal is calculated using the relationship between the input power (dBm) and the output voltage (V). Here, dBm is based on a power level of 1mW in dB.

[0044] The determination unit 113 compares the voltage value of the branch signal with the threshold voltage previously stored in the storage unit 120, and determines whether the voltage value of the branch signal is equal to or greater than the threshold voltage. In this embodiment, the threshold voltage is used as a value obtained by converting the threshold reference power, described later, into a voltage value.

[0045] In this embodiment, the threshold reference power is a power value that is equal to or greater than the power obtained by adding the gain RoF_G in the transmission path of the fiber optic radio system 10 to the minimum received power value (Pin_min) received by the antenna element 200, and is a power value that can be set in any way. That is, when the threshold reference power is P, the threshold reference power P is represented by the following equation (1).

[0046] P≥Pin_min+RoF_G···(1)

[0047] Note that the minimum received power value (Pin_min) constitutes the receiver sensitivity in the fiber optic radio system 10, indicating the degree of capability to receive weak radio waves, and is the minimum input level that satisfies a predetermined error condition. In this embodiment, the minimum received power value is assumed to be predetermined based on the environment in which the fiber optic radio system 10 is installed.

[0048] Gain RoF_G is the gain at the first amplifier 410, electro-optical converter 500, optical fiber transmission line 11, photoelectric converter 600, and second amplifier 420 of the fiber optic radio system 10.

[0049] In this embodiment, the gain RoF_G is the gain that compensates for the spatial attenuation applied after transmission when transmitting a signal from RoF transceiver 12. Figure 5 An example of the basic propagation loss in free space is shown. Figure 5 The loss L shown is represented by the following equation (2). Here, d is the distance (m), and λ represents the wavelength (m).

[0050] L=(4πd / λ)2···(2)

[0051] like Figure 5As shown, the loss L varies with distance d. Therefore, in this embodiment, the gain RoF_G is determined to compensate only for the loss L determined based on the distance d between the location of the installed fiber optic radio system 10 and the base station 20 and / or terminal 30.

[0052] The threshold voltage is obtained by converting the threshold reference power P, as defined by equation (1) above, into a voltage value. The conversion from the threshold reference power P to the threshold voltage is performed by... Figure 4 The relationship between the input power and the output voltage is shown. In this embodiment, the threshold voltage is determined by the user, etc., based on the above equations (1) and (2) and... Figure 4 The relationships shown are predetermined and stored in storage unit 120.

[0053] Note that, preferably, the threshold voltage is correlated with, for example, proportional to, the received power of the fiber optic radio system 10. For example, as... Figure 4 As shown, by setting the relationship between input power and output voltage to be correlated to a certain extent, a signal processor 100 can be implemented that can prevent complex threshold voltage settings and suppress bypass signals with a simpler configuration.

[0054] The power controller 114 controls the power supply to the first amplifier 410 used for receiving signals to be turned on and off based on the determination result determined by the determination unit 113. Specifically, when the determination unit 113 determines that the voltage value indicating the signal level of the transmitted signal is equal to or greater than the threshold voltage, the power controller 114 controls the power supply to the first amplifier 410 to be turned off. Conversely, when the determination unit 113 determines that the voltage value indicating the signal level of the transmitted signal is lower than the threshold voltage, the power controller 114 controls the power supply to the first amplifier 410 to be turned on.

[0055] Note that the power supply controller 114 controls the switching on and off of the power supply to the first amplifier 410, for example, by controlling a power supply circuit (not shown) that generates the power supply voltage for the first amplifier 410. Alternatively, the power supply controller 114 can be configured to physically cut off the conduction of the power supply voltage supplied to the first amplifier 410 using an electromagnetic relay or the like. Alternatively, the power supply controller 114 can be configured to control the switching on and off of the power supply to the first amplifier 410 by using a semiconductor switch such as a transistor for power supply to the first amplifier 410.

[0056] (An overview of the processing flow in the signal processor 100)

[0057] Next, refer to Figure 6 The flowchart shown describes the processing flow in the signal processor 100. When the signal processor 100 is started, it begins... Figure 6The flowchart illustrates a series of operations of the signal processor 100, and processing ends when the operations are completed. Figure 6 The flowchart shown also terminates the process by a power outage or interruption to indicate completion. In the following description of the flowchart, the same content as described above in the description of the fiber optic radio system 10 and the signal processor 100 is omitted or simplified.

[0058] In step S601, the branching unit 111 performs branching processing on the transmitted signal. Specifically, the branching unit 111 branches the transmitted signal and acquires the branched signal. Then, the processing proceeds to step S602.

[0059] In step S602, the detection unit 112 performs detection processing on the branch signal. Specifically, the detection unit 112 performs envelope detection on the branch signal extracted by the branch unit 111 and calculates the signal level. In step S602, the detection unit 112 calculates the voltage value based on the electrical power (signal level) of the branch signal. Then, the processing proceeds to step S603.

[0060] In step S603, the determination unit 113 determines whether the voltage value of the branch signal's signal level calculated by the detection unit 112 is equal to or greater than the threshold voltage pre-stored in the storage unit 120. When the determination unit 113 determines in step S603 that the voltage value of the branch signal's signal level is equal to or greater than the threshold voltage (step S603: Yes), the process proceeds to step S604. Conversely, when the determination unit 113 determines in step S603 that the voltage value of the branch signal's signal level is lower than the threshold voltage (step S603: No), the process proceeds to step S605.

[0061] In step S604, the power controller 114 performs power control processing on the first amplifier 410. Specifically, the power controller 114 controls the power circuit of the first amplifier 410 to disconnect the power supply voltage to the first amplifier 410. Next, the process proceeds to step S606.

[0062] In step S605, the power controller 114 performs power control processing on the first amplifier 410. Specifically, the power controller 114 controls the power circuit of the first amplifier 410 to connect the power supply voltage to the first amplifier 410. Next, the process proceeds to step S606.

[0063] In step S606, the controller 110 determines whether control has been completed in the signal processor 100. When the controller 110 determines in step S606 that control has been completed in the signal processor 100 (step S606: Yes), the process proceeds to step S607. Conversely, when the controller 110 determines in step S606 that control has not been completed in the signal processor 100 (step S606: No), the process returns to step S603, and the process starting from step S603 is repeated.

[0064] In step S607, the power controller 114 performs power control processing on the first amplifier 410. Specifically, the power controller 114 controls the power circuit of the first amplifier 410 to connect the power supply voltage to the first amplifier 410. As a result, in the fiber optic radio system 10, assuming normal radio communication is to be performed.

[0065] As described above, the signal processor 100 is disposed in a transceiver for transmitting and receiving radio signals, and includes a branching unit 111, a detection unit 112, a determination unit 113, and a power controller 114. The branching unit 111 branches the transmitted signal and acquires the branched signal. The detection unit 112 detects the branched signal and acquires its voltage value. The determination unit 113 compares the voltage value of the branched signal with a threshold voltage pre-stored in the storage unit 120, and determines whether the voltage value of the branched signal is equal to or greater than the threshold voltage. The power controller 114 controls the power supply to the transceiver's receiving signal amplifier based on the determination result determined by the determination unit 113.

[0066] Therefore, the signal processor 100 does not need to include a frequency-corresponding multiplex delay circuit, and enables the suppression of bypass signals using a simple configuration.

[0067] The threshold voltage of the signal processor 100 can be determined based on the minimum received power of the fiber optic radio system including the transceiver and the gain in the transmission path of the fiber optic radio system. Therefore, the signal processor 100 enables the use of a threshold voltage corresponding to the fiber optic radio system and allows for more accurate threshold determination corresponding to the system.

[0068] (Other embodiments)

[0069] Although embodiments have been described in detail with reference to the accompanying drawings, these embodiments are not limited to the content described in the above embodiments. The above-described components include those that can be readily conceived and are substantially equivalent to those skilled in the art. The above configurations can be combined in a suitable manner. Various omissions, substitutions, or changes can be made to the configurations without departing from the spirit of the embodiments.

[0070] The above embodiments illustrate an example of the signal processor 100 being applied to an optical fiber radio system 10 including a first transceiver 12a, a second transceiver 12b, and an optical fiber transmission line 11. The signal processor 100 can be used not only in systems for relaying and transmitting via the optical fiber transmission line 11, but also in systems for relaying and transmitting via cables such as high-frequency coaxial cables or twisted-pair cables.

[0071] The computer program (signal processing program) used to cause a computer to perform the processing (signal processing method) in the signal processor 100 described above, and the non-transitory computer-readable storage medium on which the program is stored, are included within the scope of this embodiment. The type of non-transitory computer-readable storage medium can be any type. The computer program described above is not limited to a computer program stored on a non-transitory storage medium, but can also be a computer program transmitted via telecommunication lines, wireless or wired communication lines, networks represented by the Internet, etc.

[0072] The characteristics of the signal processor 100, RoF transceiver 12, fiber optic radio system 10, and signal processing method are described below.

[0073] According to the first aspect, a signal processor 100 is disposed in a transceiver for transmitting and receiving radio signals, and includes a branching unit 111 and a detection unit 112. The branching unit 111 branches the transmitted signal and acquires the branched signal, and the detection unit 112 detects the branched signal and acquires the voltage value of the branched signal. The signal processor 100 also includes a determination unit 113, which compares the voltage value of the branched signal with a threshold voltage pre-stored in a storage unit 120, and determines whether the voltage value of the branched signal is equal to or greater than the threshold voltage. The signal processor 100 also includes a power controller 114, which controls the power supply to the transceiver's receiving signal amplifier according to the determination result determined by the determination unit 113.

[0074] The above configuration eliminates the need for the signal processor 100 to be equipped with a frequency-specific multiplex delay circuit, and enables the suppression of bypass signals using a simple configuration.

[0075] According to the second aspect, the threshold voltage of the signal processor 100 can be a value determined based on the minimum received power value of the fiber optic radio system including the transceiver and the gain in the transmission path of the fiber optic radio system.

[0076] The above configuration enables the signal processor 100 to use the threshold voltage corresponding to the fiber optic radio system and to perform more accurate threshold determination corresponding to the system.

[0077] According to the third aspect, the RoF transceiver 12 is a RoF (Radio over Fiber) transceiver used for relaying and transmitting radio signals via an optical fiber transmission line 11 in radio communication between a base station 20 and a terminal 30. The RoF transceiver 12 includes: an antenna unit 200 for transmitting and / or receiving radio signals; and a first amplifier 410 for amplifying the received signal and generating a first electrical signal. The RoF transceiver 12 also includes an electro-optical converter 500 that converts the first electrical signal amplified by the first amplifier 410 into an optical transmission signal and transmits the optical transmission signal to the optical fiber transmission line 11. The RoF transceiver 12 also includes an opto-optical converter 600 that converts the optical received signal received via the optical fiber transmission line 11 into a second electrical signal. The RoF transceiver 12 further includes: a second amplifier 420 that amplifies the second electrical signal and generates a transmission signal; and a signal processor 100 that receives the transmission signal amplified by the second amplifier 420 as input. The signal processor 100 includes: a branching unit 111, which branches and transmits signals and acquires branch signals; and a detection unit 112, which detects the branch signals and acquires the voltage values ​​of the branch signals. The signal processor 100 also includes a determination unit 113, which compares the voltage value of the branch signals with a threshold voltage pre-stored in a storage unit 120, and determines whether the voltage value of the branch signals is equal to or greater than the threshold voltage. The signal processor 100 also includes a power controller 114, which controls the switching on and off of the power supply to the first amplifier 410 based on the determination result determined by the determination unit 113.

[0078] The above configuration eliminates the need to configure a RoF transceiver 12, which includes a signal processor 100 with multiplexed delay circuitry corresponding to the frequency, and enables the suppression of bypass signals with a simple configuration.

[0079] The fiber optic radio system 10 according to the fourth aspect includes: a first transceiver 12a, which performs radio communication with a base station 20, the first transceiver 12a being the aforementioned RoF transceiver 12; and a second transceiver 12b, which performs radio communication with a terminal 30, the second transceiver being the aforementioned RoF transceiver 12. In the fiber optic radio system 10, the first transceiver 12a and the second transceiver 12b are connected via a fiber optic transmission line 11.

[0080] The above configuration eliminates the need for setting up an optical fiber radio system 10 including a RoF transceiver 12 with multiple delay circuitry corresponding to the frequency, and makes it possible to suppress bypass signals with a simple configuration.

[0081] The signal processing method according to the fifth aspect is a computer-executable signal processing method, and includes the steps of transmitting a branch signal and acquiring the branch signal, and detecting the branch signal and acquiring the voltage value of the branch signal. The signal processing method further includes the step of comparing the voltage value of the branch signal with a threshold voltage pre-stored in the storage unit 120 and determining whether the voltage value of the branch signal is equal to or greater than the threshold voltage. The signal processing method also includes the step of controlling the switching on and off of power to the receiving signal amplifier based on the determined result.

[0082] In the above configuration, the use of signal processing methods eliminates the need to set up multiple delay circuits corresponding to the frequency, and makes it possible to suppress bypass signals with a simple configuration.

[0083] Although the invention has been described above with reference to embodiments, the invention is not limited thereto, and the configuration of the components can be replaced by any configuration with similar functionality, provided that they are within the scope of the claims.

Claims

1. A signal processor provided in a transceiver for transmitting and receiving a radio signal, the signal processor comprising: a branching unit configured to branch a transmission signal and acquire a branched signal; a detection unit configured to detect the branched signal and acquire a voltage value of the branched signal; a determination unit configured to compare the voltage value of the branched signal with a threshold voltage pre-stored in a storage unit, and determine whether the voltage value of the branched signal is equal to or greater than the threshold voltage; and a power controller configured to control turning on and off of a power of a reception signal amplifier of the transceiver according to a determination result determined by the determination unit, wherein, in a case where the voltage value of the branched signal is equal to or greater than the threshold voltage, the power controller controls the power of the reception signal amplifier to be turned off, in a case where the voltage value of the branched signal is less than the threshold voltage, the power controller controls the power of the reception signal amplifier to be turned on. 2.The signal processor according to claim 1, wherein the threshold voltage is a value determined based on a minimum reception power value of a fiber radio system including the transceiver, which constitutes reception sensitivity in the fiber radio system and indicates a degree of an ability to receive a weak radio wave, and a gain in a transmission path of the fiber radio system. 3.A radio over fiber (RoF) transceiver for relaying and transmitting a radio signal via an optical fiber transmission line in radio communication between a base station and a terminal, the RoF transceiver comprising: an antenna unit configured to transmit and / or receive the radio signal; a first amplifier configured to amplify a reception signal and generate a first electric signal; an electro-optical converter configured to convert the first electric signal amplified by the first amplifier into an optical transmission signal, and transmit the optical transmission signal to the optical fiber transmission line; an optical-electric converter configured to convert an optical reception signal received via the optical fiber transmission line into a second electric signal; a second amplifier configured to amplify the second electric signal and generate a transmission signal; and a signal processor configured to input the transmission signal amplified by the second amplifier, wherein the signal processor comprises: a branching unit configured to branch the transmission signal and acquire a branched signal; a detection unit configured to detect the branched signal and acquire a voltage value of the branched signal; a determination unit configured to compare the voltage value of the branched signal with a threshold voltage pre-stored in a storage unit, and determine whether the voltage value of the branched signal is equal to or greater than the threshold voltage; and a power controller configured to control turning on and off of a power of the first amplifier according to a determination result determined by the determination unit. ​ ​ wherein, in a case where the voltage value of the branch signal is equal to or greater than the threshold voltage, the power supply controller controls the power supply of the first amplifier to be turned off, in a case where the voltage value of the branch signal is less than the threshold voltage, the power supply controller controls the power supply of the first amplifier to be turned on.

4. A radio-over-fiber system comprising: a first transceiver configured to perform radio communication with a base station, the first transceiver being the RoF transceiver according to claim 3; and a second transceiver configured to perform radio communication with a terminal, the second transceiver being the RoF transceiver according to claim 3, wherein the first transceiver and the second transceiver are connected via a fiber transmission line.

5. A signal processing method executed by a computer, comprising: a step of branching a transmission signal and acquiring a branch signal; a step of detecting the branch signal and acquiring a voltage value of the branch signal; a step of comparing the voltage value of the branch signal with a threshold voltage pre-stored in a storage unit and determining whether the voltage value of the branch signal is equal to or greater than the threshold voltage; and a step of controlling turning on and off of a power supply of a reception signal amplifier according to a determination result of the determination, wherein, in a case where the voltage value of the branch signal is equal to or greater than the threshold voltage, the power supply of the reception signal amplifier is controlled to be turned off, in a case where the voltage value of the branch signal is less than the threshold voltage, the power supply of the reception signal amplifier is controlled to be turned on.

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