Radio wave receiving system

Abstract

A radio wave receiving system is provided that allows a receiving device to check the operating states of an antenna and a terminal device that generates an optical signal with a simple configuration. [Solution] The system includes an amplifier-equipped antenna 1, an optical network unit 2 having an E / O converter 5 that outputs intensity-modulated light 6 according to a received signal and outputs the intensity-modulated light 6 through an optical fiber 7, and a receiving device 3 connected to the optical fiber 7 and having an O / E converter 8 that converts the intensity-modulated light 6 into an electrical signal. The optical network unit 2 has means for acquiring antenna monitoring information that monitors the operation of the antenna and optical network unit monitoring information that monitors the operation of the optical network unit 2, and has signal multiplexing means for converting the antenna monitoring information and optical network unit monitoring information into signals modulated at a frequency f that satisfies f≦0.8f0, where the center frequency of the received signal is f0, and superimposing the converted information on the received signal. The receiving device 3 has signal separation means for separating and acquiring the antenna monitoring information and optical network unit monitoring information from the intensity-modulated light 6.

Description

[Technical Field]

[0001] The present invention relates to a radio wave receiving system in which a signal received from an antenna placed outdoors or the like is converted into an optical signal by an optical terminal device installed near the antenna, and the optical signal is guided via an optical fiber to a receiving device installed in a remote location such as indoors. [Background technology]

[0002] Radio wave receiving systems that convert electrical signals received by an antenna into optical signals and transmit them over optical fiber have the great advantage of enabling long-distance transmission of high-frequency signals such as microwave signals, which have large transmission losses over coaxial cables. Furthermore, because devices are connected by optical fiber, it is possible to prevent lightning damage from spreading to downstream terminal devices, and by using optical branching, it is possible to simultaneously supply received signals to multiple receiving devices. Examples of such systems are described in Patent Documents 1 and 2.

[0003] On the other hand, the Global Navigation Satellite System (GNSS) is used in a variety of fields, and can determine the position of a receiver and the exact time at the same time by calculating the distance to each satellite from the difference in the reception time from multiple GNSS satellites.The radio wave receiving system converts the received signal from the antenna into an optical signal and transmits it.The advantages of the system, such as the transmission distance and the ability to distribute to multiple points, make it very suitable for transmitting GNSS signals received by a single antenna to many devices that use GNSS signals, and it is used in many systems. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-53731 [Patent Document 2] Japanese Patent Publication No. 2020-102664 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned radio wave receiving system, the receiving device that receives the GNSS signal transmitted via optical fiber needs to be able to constantly check whether the antenna and the terminal device that generates the optical signal are operating normally in order to confirm the reliability of the received GNSS signal. Furthermore, when an abnormality occurs in the equipment, it is necessary to quickly isolate the malfunctioning device in order to quickly restore the system. However, transmitting this information independently would complicate the equipment configuration and significantly increase costs.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a radio wave receiving system that solves the above problems and allows a receiving device to check the operating status of an antenna and a terminal device that generates an optical signal with a simple configuration. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, in a first aspect, a radio wave receiving system according to the present invention is a radio wave receiving system comprising: an antenna having a built-in amplifier for amplifying a received signal; an optical network unit connected to the antenna, having an E / O converter that outputs intensity-modulated light according to the received signal and outputs the intensity-modulated light through an optical fiber; and a receiving device connected to the optical fiber, having an O / E converter that converts the intensity-modulated light into an electrical signal, wherein the optical network unit has: means for acquiring antenna monitoring information that monitors the operation of the antenna; means for acquiring optical network unit monitoring information that monitors the operation of the optical network unit; and signal multiplexing means for converting the antenna monitoring information and the optical network unit monitoring information into a signal modulated at a frequency f that satisfies f≦0.8f0, where f0 is the center frequency of the received signal; and the receiving device has signal separation means for separating and acquiring the antenna monitoring information and the optical network unit monitoring information from the intensity-modulated light.

[0008] As described above, in the present invention, an optical network unit (ONU) located near an antenna and outputting a received signal as intensity-modulated light via an E / O converter includes a means for acquiring antenna monitoring information for monitoring the operation of the antenna and a means for acquiring optical network unit monitoring information for monitoring the operation of the ONU itself. These two pieces of monitoring information are converted into signals modulated at a frequency different from the center frequency of the received signal and superimposed on the received signal by a signal multiplexing means. The multiplexed signal is converted into intensity-modulated light by an E / O converter and sent to a receiving device, where the two pieces of monitoring information can be separated from the received signal by a signal separating means. In this case, multiplexing the monitoring signal at a frequency different from the center frequency of the received signal allows continuous monitoring without affecting the received signal. Experiments have confirmed that frequencies below 80% of the center frequency of the received signal do not affect the received signal. This simple configuration enables the operating status of the antenna and the optical network unit generating the optical signal to be monitored and confirmed by a receiving device receiving GNSS signals, etc.

[0009] Here, the antenna monitoring information can be obtained by monitoring the drive current of the built-in amplifier, detecting the received signal at the antenna and converting it to a DC voltage to monitor the received power, etc. The optical network unit monitoring information can be obtained by monitoring the drive current of the amplifier built into the optical network unit, monitoring the power supply voltage, inputting a pilot signal to monitor the overall gain, etc. Furthermore, the drive current of the E / O converter and the emission intensity of the light source used may also be monitored as the optical network unit monitoring information. The two pieces of monitoring information superimposed on the received signal may be analog values ​​corresponding to the drive current, received power, etc., or may be information converted into multi-level digital values.

[0010] In addition, methods for multiplexing two pieces of monitoring information onto a received signal include the use of a directional coupler, high-frequency power combining, or switching using a switch, and methods for separating signals from the received signal include the use of a frequency filter and a directional coupler or a high-frequency power divider.

[0011] In a second aspect, the present invention provides a radio wave receiving system according to the first aspect, further comprising a plurality of the receiving devices, wherein the optical fiber transmitting the intensity-modulated light output from the optical network unit has an optical branch, and the plurality of receiving devices are connected to the optical fibers branched by the optical branch. In the present aspect of the invention, when there are a plurality of devices that use a received signal from a single antenna, the received signal can be distributed to a large number of receiving devices by using an optical branch, as in the present aspect of the invention. There is no need to change the configuration of the optical network unit or the receiving devices, and since a supervisory signal multiplexed on the received signal is also distributed, each receiving device can obtain supervisory information.

[0012] In a third aspect, the present invention provides the radio wave receiving system of the first aspect, characterized in that the means for acquiring the antenna monitoring information measures the drive current of the built-in amplifier. It is known that, in practice, malfunctions of an antenna with a built-in amplifier are more likely to be caused by failures of the built-in amplifier than by failures of the antenna itself. Furthermore, when a built-in amplifier fails, its drive current often deviates from its rated value. Therefore, the invention of this aspect acquires the antenna monitoring information by measuring the drive current of the built-in amplifier. This monitoring information may be the measured drive current value itself, or it may be binary information indicating whether the drive current value is normal or abnormal, or multi-valued information indicating the degree of abnormality.

[0013] In a fourth aspect, the present invention provides the radio wave receiving system of the first aspect, wherein the optical network unit has an amplifier, and the means for acquiring the optical network unit monitoring information is performed by measuring a drive current of the amplifier. In this aspect of the invention, the optical network unit may have a plurality of amplifiers, and in that case, the monitoring information may be information obtained from one of the amplifiers, or a plurality of pieces of information obtained from the plurality of amplifiers.

[0014] In a fifth aspect, the present invention is characterized in that, in the radio wave receiving system of the first aspect, the signal multiplexing means and the signal separating means each use a directional coupler, a high-frequency power divider, or a high-frequency power combiner. The invention of this aspect uses a directional coupler or a high-frequency power combiner as the signal multiplexing means that superimposes two pieces of monitoring information onto the received signal, and uses a directional coupler or a high-frequency power divider as the signal separating means that separates them from the received signal. This makes it possible to realize the signal multiplexing means and the signal separating means with simpler configurations.

[0015] In a sixth aspect, the present invention provides the radio wave receiving system of the first aspect, wherein the antenna monitoring information is binary information indicating whether the magnitude of the drive current of the built-in amplifier is within a normal range or an abnormal range, and the optical network unit monitoring information is binary information indicating whether the optical network unit is in a normal operating state or an abnormal operating state, and the signal multiplexing means includes means for blocking the signal modulated at the frequency f to be superimposed on the received signal at a constant period T, turning the time during which the signal modulated at the frequency f passes through within the period T into ON, and changing the duty ratio, i.e., ON / T, to superimpose the signal on the received signal, and the duty ratio is set to a value corresponding to the binary information of the antenna monitoring information and the optical network unit monitoring information, respectively.

[0016] In this aspect of the invention, first, the antenna monitoring information is binary information indicating whether the magnitude of the drive current of the built-in amplifier is within a normal range or an abnormal range, and the optical network unit monitoring information is also binary information indicating whether the optical network unit is in a normal operating state or an abnormal operating state. Furthermore, the signal of frequency f carrying the monitoring information is cut off at a constant period T, for example, a period T of about 100 μs to 100 ms, and the ON / T duty ratio corresponds to the values ​​of the above two pieces of information. For example, when both the antenna monitoring information and the optical network unit monitoring information are normal, the signal of frequency f is not cut off, i.e., all are ON and the duty ratio is 100%. When both are abnormal, the signal of frequency f is all cut off, i.e., the duty ratio is 0%. When only the former is abnormal, the duty ratio is set to a value between 60 and 90%, and when only the latter is abnormal, the duty ratio is set to a value between 10 and 40%, etc.

[0017] In a seventh aspect, the present invention provides a radio wave receiving system according to any one of the first to sixth aspects, wherein the optical network unit has data processing means for converting the antenna monitoring information and the optical network unit monitoring information into multi-value digital data and processing the digital data, the data processing means comprising a microcomputer. The invention of this aspect has data processing means, which first converts the antenna monitoring information and the optical network unit monitoring information into multi-value digital data that is easy for the microcomputer to process. Furthermore, this digital data can be subjected to data processing, such as comparing the operation status of the antenna and the operation status of the optical network unit with predetermined judgment values ​​and creating monitoring information according to the abnormality level. This digital data processing can be achieved in a small size and at low cost by using, for example, a microcomputer on a chip.

[0018] In an eighth aspect, the present invention provides a radio wave receiving system according to any one of the first to sixth aspects, characterized in that the radio wave receiving system is used in a system for receiving radio waves from an artificial satellite in a satellite positioning system. Taking advantage of advantages such as long-distance transmission of high-frequency signals, isolation from lightning damage, and the ability to supply signals to multiple receiving devices via optical branching, the radio wave receiving system of the present invention can be applied to many systems other than satellite positioning systems in which antennas and receiving devices are installed at a distance. For example, a system that distributes TV signals received by an antenna to many locations in an apartment building or facility, or a system that transmits signals received from multiple antennas installed at a distance to an administrative building, such as an airport. Among these many applications, systems that receive radio waves from artificial satellites in a satellite positioning system are particularly in demand for constantly monitoring the operating status of antennas and optical terminal devices, because the reliability of the received signal significantly affects the reliability of the devices and systems that use the data. In other words, the present invention is extremely effective for systems that receive radio waves from artificial satellites in a satellite positioning system.

[0019] In a ninth aspect, the present invention provides the radio wave receiving system according to the seventh aspect, characterized in that the radio wave receiving system is used in a system for receiving radio waves from an artificial satellite in a satellite positioning system.

[0020] In a tenth aspect, the present invention provides the radio wave receiving system of the eighth aspect, wherein the receiving device comprises a GNSS signal processing device that processes GNSS signals obtained by receiving radio waves from artificial satellites and current cut-off means, the GNSS signal processing device having a current supply monitoring circuit that supplies current to an external device of the GNSS signal processing device and monitors the current value, and the current cut-off means cuts off the current depending on the antenna monitoring information and the optical terminal device monitoring information. In a conventional radio wave receiving system that receives signals from an amplifier-integrated antenna by transmitting them via a coaxial cable without using an optical terminal device like the present invention, a system may be used that monitors the operation of the amplifier-integrated antenna by supplying current from the GNSS signal processing device to the built-in amplifier of the amplifier-integrated antenna and monitoring the current. By using the invention of this aspect, the antenna monitoring function of the GNSS signal processing device used in the above-mentioned conventional system can also be effectively utilized in the radio wave receiving system of the present invention.

[0021] In an eleventh aspect, the present invention is characterized in that, in the radio wave receiving system of the ninth aspect, the receiving device comprises a GNSS signal processing device that processes GNSS signals obtained by receiving radio waves from an artificial satellite, and current cut-off means, the GNSS signal processing device comprises a current supply monitoring circuit that supplies current to the outside of the GNSS signal processing device and monitors the current value, and the current cut-off means cuts off the current depending on the antenna monitoring information and the optical terminal device monitoring information. [Effects of the Invention]

[0022] As described above, the present invention provides a radio wave receiving system with a simple configuration that allows a receiving device to check the operating status of an antenna and a terminal device that generates an optical signal. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a block diagram showing an example of a radio wave receiving system according to a first embodiment. [Figure 2] FIG. 10 is a configuration diagram showing an example of a radio wave receiving system according to a second embodiment. [Figure 3] FIG. 11 is a block diagram illustrating an example of an optical network unit and a receiving device of a radio wave receiving system according to a third embodiment. [Figure 4] FIG. 10 is a block diagram showing an example of a receiving device of a radio wave receiving system according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, the radio wave receiving system of the present invention will be described in detail by way of examples with reference to the drawings. In the description of the drawings, the same elements are given the same reference numerals and redundant description will be omitted. [Example]

[0025] Fig. 1 is a block diagram showing an example of a radio wave receiving system according to a first embodiment of the present invention. In Fig. 1, a radio wave receiving system 10 of this embodiment includes an amplifier-integrated antenna 1, an optical network unit 2, and a receiving device 3. The amplifier-integrated antenna 1 has a built-in amplifier 4 for amplifying a received signal received by an antenna 11. The optical network unit 2 is connected to the amplifier-integrated antenna 1 by a coaxial cable 12, and has an E / O converter 5 that outputs intensity-modulated light 6 corresponding to the received signal, and outputs the intensity-modulated light 6 through an optical fiber 7. The receiving device 3 is connected to the optical fiber 7, and has an O / E converter 8 that converts the intensity-modulated light 6 into an electrical signal.

[0026] The optical network unit 2 has a means for acquiring antenna monitoring information for monitoring the operation of the amplifier-integrated antenna 1, and a means for acquiring optical network unit monitoring information for monitoring the operation of the optical network unit 2. In this embodiment, the means for acquiring the antenna monitoring information is first performed by measuring the drive current of the built-in amplifier 4. Specifically, a drive current I1 is supplied from the amplifier power supply 13 provided in the optical network unit 2 via a current monitor circuit 14, a bias T15, and a coaxial cable 12, and then from the voltage stabilization circuit 17 to the built-in amplifier 4 through a bias T16 in the amplifier-integrated antenna 1. The value of this supplied drive current I1 is measured by the current monitor circuit 14 and sent to the monitoring information generation circuit 18, which determines whether the operation is normal or to what extent the operating state is at an acceptable level, and generates antenna monitoring information. The signal is then converted into a signal of a predetermined frequency f corresponding to the information.

[0027] In this embodiment, the optical network unit 2 includes an amplifier 9 for amplifying a received signal having a center frequency f0 obtained from the amplifier-integrated antenna 1, and the optical network unit monitoring information is acquired by measuring the drive current of the amplifier 9. Specifically, a drive current I2 is supplied to the amplifier 9 from an amplifier power supply 19 provided in the optical network unit 2 through a current monitor circuit 21. The value of this supplied drive current I2 is measured by the current monitor circuit 21 and sent to the monitor information generation circuit 18, which determines whether the amplifier 9 is operating normally and what the acceptable operating level is, and generates optical network unit monitoring information. The signal is then converted into a signal of a predetermined frequency f corresponding to the information. That is, the monitor information generation circuit 18 generates both antenna monitoring information and optical network unit monitoring information, and converts the two pieces of information into signals of a predetermined frequency f corresponding to the two pieces of information. The amplifier power supply 13 that supplies power to the amplifier-integrated antenna 1 and the amplifier power supply 19 that drives the amplifier of the optical network unit 2 may be a single common power source.

[0028] The signal of frequency f containing both the antenna monitoring information and the optical network unit monitoring information and the amplified received signal of center frequency f0 pass through frequency filters 22 and 23 corresponding to the respective frequencies, are multiplexed by high-frequency power combiner 24, converted into intensity-modulated light 6 by E / O converter 5, and output to optical fiber 7. For example, if the received signal is a GNSS signal, its center frequency f0 is about 1 to 2 GHz, and in this case, frequency f can be about 1 to 100 MHz.

[0029] Here, the antenna monitoring information and optical network unit monitoring information may be converted into multi-value digital data in the monitoring information generation circuit 18. Furthermore, a microcomputer may perform data processing such as comparing the digital data with predetermined judgment values ​​for the operation status of the antenna and the optical network unit, and creating monitoring information according to the abnormality level. By using a microcomputer on a chip, such data processing can be achieved in a small size and at low cost.

[0030] In the receiving device 3, the intensity-modulated light 6 input through the optical fiber 7 is converted into an electric signal by the O / E converter 8. The electric signal is amplified by the amplifier 25 and divided into two by the high-frequency power divider 26, and separated into a received signal with a center frequency f0 that passes through the frequency filter 27, and antenna monitoring information and optical network unit monitoring information with a frequency f that pass through the frequency filter 28. The received signal is converted into a target signal by the received signal processing circuit 29 for use, and the two pieces of monitoring information are converted into target monitoring information by the monitoring information processing circuit 30 for use.

[0031] As described above, in this embodiment, the receiving device can check the operating status of the antenna and the terminal device that generates the optical signal with a simple configuration. [Example]

[0032] FIG. 2 is a configuration diagram showing an example of a radio wave receiving system according to a second embodiment of the present invention. In FIG. 2, the radio wave receiving system 20 of this embodiment is a system for receiving radio waves from an artificial satellite in a satellite positioning system. An amplifier-integrated antenna 31 installed on the roof of a building is connected to an optical network unit 32 via a coaxial cable. The amplifier-integrated antenna 31 and the optical network unit 32 have the same configurations as the amplifier-integrated antenna 1 and the optical network unit 2 of the first embodiment, respectively. This system has three receivers 33, 34, and 35. An optical fiber 37 transmitting intensity-modulated light output from the optical network unit 32 has two 1×2 optical branches 38 and 39. The receiver 33 is connected to the optical fiber branched by the optical branch 38, and the receivers 34 and 35 are connected to the optical fiber branched by the optical branch 39. The configurations of the receivers 33, 34, and 35 are the same as those of the receiver 3 of the first embodiment.

[0033] In a GNSS system, accurate time information can be obtained from the received GNSS signal, so in this embodiment, for example, the time synchronization signal used by a time server that supplies reference time to various devices on each floor can be obtained by receivers 33, 34, and 35 installed on each floor. In this embodiment, a 1x2 optical branch is used and three receivers are shown, but a system with, for example, 10 or more receivers is also possible. In this case, optical branching such as 1x4, 1x8, or 1x16 can be used.

[0034] In this embodiment as well, if any trouble occurs in a receiving device, each receiving device can determine whether the trouble is caused by the amplifier built-in antenna or the optical network unit. [Example]

[0035] 3 is a block diagram showing an example of an optical network unit and a receiving device of a radio wave receiving system according to a third embodiment of the present invention. Although not shown in FIG. 3, the configuration of the amplifier-integrated antenna of the radio wave receiving system of this embodiment is the same as that of the amplifier-integrated antenna 1 of the first embodiment. In FIG. 3, an optical network unit 40 is connected to the amplifier-integrated antenna by a coaxial cable 12, has an E / O converter 5 that outputs intensity-modulated light 6 according to a received signal, and outputs the intensity-modulated light 6 through an optical fiber 7. A receiving device 50 is connected to the optical fiber 7, and has an O / E converter 8 that converts the intensity-modulated light 6 into an electrical signal.

[0036] Like the optical network unit 2 of the first embodiment, the optical network unit 40 supplies a drive current I1 from the amplifier power supply 13 to the built-in amplifier in the amplifier-integrated antenna via the current monitor circuit 14, bias T15, and coaxial cable 12. The value of this supplied drive current I1 is measured by the current monitor circuit 14 and sent to the monitoring information generation circuit 46. The optical network unit 40 also has three amplifiers 41, 42, and 43 for amplifying a received signal having a center frequency f0 obtained from the amplifier-integrated antenna. Optical network unit monitoring information is acquired by measuring the drive currents I3, I4, and I5 of the amplifiers 41, 42, and 43, respectively. Specifically, the amplifier power supply 44 provided in the optical network unit 40 supplies drive currents to the amplifiers 41, 42, and 43 via the current monitor circuit 45, and the values ​​of these drive currents are measured by the current monitor circuit 45 and sent to the monitoring information generation circuit 46. Here, the amplifiers 41, 42, and 43 are used to increase the amplification of the received signal or to adjust the amplification.

[0037] In this embodiment, the antenna monitoring information is binary information indicating whether the value of the drive current I1 of the built-in amplifier is within a normal range or an abnormal range. The optical network unit monitoring information is binary information indicating whether the optical network unit 40 is in a normal or abnormal operating state, i.e., whether the measured values ​​of the drive currents I3, I4, and I5 of the amplifiers 41, 42, and 43 are all within the specified values. The monitoring information generating circuit 46 determines whether the amplifier-built-in antenna and the optical network unit 40 are in a first state where both are operating normally, a second state where only the former is operating abnormally, a third state where only the latter is operating abnormally, or a fourth state where both are operating abnormally, and outputs a signal according to the determination result.

[0038] In the signal multiplexing means of this embodiment, a signal of frequency f generated by a signal generator 47 passes through a frequency filter 22 and is then blocked by a high-frequency switch 48 at a fixed period T. The time during which the signal of frequency f passes through the high-frequency switch 48 is designated as ON, and its duty ratio, i.e., the ON / T ratio, is changed based on the result of the determination by the monitoring information generation circuit 46, thereby superimposing monitoring information onto the received signal. For example, in the first state described above, no signal of frequency f is blocked, i.e., all signals are ON, and the duty ratio is 100%. If both signals are abnormal, all signals of frequency f are blocked and the duty ratio is 0%. If only the former is abnormal, the duty ratio is set to 60-70%, and if only the latter is abnormal, the duty ratio is set to 30-40%. The signal of frequency f that passed through the high-frequency switch 48 is multiplexed with a received signal of center frequency f0 that passed through the frequency filter 23 by the high-frequency power combiner 24, as in the first embodiment, and converted into intensity-modulated light 6 by the E / O converter 5 and output to the optical fiber 7.

[0039] In the receiving device 50, the input intensity-modulated light 6 is converted into an electric signal by the O / E converter 8, amplified by the amplifier 25, and divided into two by the high-frequency power divider 26, and separated into a received signal with a center frequency f0 that passes through a frequency filter 27, and antenna monitoring information and optical network unit monitoring information with a frequency f that passes through a frequency filter 28. The received signal is converted into a target signal by the received signal processing circuit 29 and used.

[0040] The monitoring information corresponding to the duty ratio of frequency f is converted by logarithmic amplifier 51 into a rectangular signal corresponding to the duty ratio, and then shaped by comparator 52 into a rectangular wave with a voltage of approximately 5 to 7 V. This signal is then converted into a DC voltage by frequency filter 53, which passes low frequencies. For example, the signal is converted into DC voltages of 5 to 6 V, 3 to 4 V, 1 to 2 V, and 0 V, corresponding to the first, second, third, and fourth states, respectively. This DC voltage is then supplied to three comparators 54, 55, and 56. Comparator 54 outputs a signal or display when a voltage of 5 V or higher is input, confirming that the amplifier-integrated antenna and optical network unit are operating normally. Comparator 55 outputs a signal or display when a voltage of 3 to 4 V is input, confirming that only the amplifier-integrated antenna is operating abnormally. Comparator 56 outputs a signal or display when a voltage of 1 to 2 V is input, confirming that only the optical network unit is operating abnormally. When none of the three comparators 54, 55, 56 outputs any signal, it can be confirmed that both the amplifier built-in antenna and the optical network unit are operating abnormally. [Example]

[0041] 4 is a block diagram showing an example of a receiving device of a radio wave receiving system according to a fourth embodiment of the present invention. Although not shown, the amplifier-integrated antenna and optical network unit of the radio wave receiving system of this embodiment have the same configurations as the amplifier-integrated antenna 1 and the optical network unit 2 of the first embodiment, respectively. In FIG. 4, a receiving device 60 of this system converts input intensity-modulated light 6 into an electrical signal by an O / E converter 8, amplifies it by an amplifier 25, and divides it into two by a high-frequency power divider 26, separating it into a received signal with a center frequency f0 that passes through a frequency filter 27 and antenna monitoring information and optical network unit monitoring information with a frequency f that pass through a frequency filter 28.

[0042] Furthermore, the receiving device 60 of this system includes a GNSS signal processing device 61 that processes GNSS signals obtained by receiving radio waves from artificial satellites, and a switch 62 that serves as current interruption means. The GNSS signal processing device 61 includes a current supply monitoring circuit 64 that supplies a current 63 to the outside of the GNSS signal processing device 61 and monitors the current value. Antenna monitoring information and optical terminal device monitoring information are detected by a monitoring information processing circuit 65, and if an abnormality is detected in either monitoring information, a signal to interrupt the current 63 is sent to the switch 62. While the switch 62 is not interrupted and the current 63 is flowing, the current 63 is absorbed by a current circuit 66, and the current supply monitoring circuit 64 monitors the current value to confirm that no abnormality exists. If an abnormality occurs in the amplifier-integrated antenna or the optical terminal device, the current 63 is interrupted, allowing the GNSS signal processing device 61 to detect the occurrence of the abnormality.

[0043] In a conventional radio wave receiving system that receives a signal from an amplifier-integrated antenna and transmits it to a GNSS signal processing device via a coaxial cable without using an optical terminal device, a system may be used that monitors the operation of the amplifier-integrated antenna by supplying a current from the GNSS signal processing device to the built-in amplifier of the amplifier-integrated antenna and monitoring that current. The receiving device 60 of this embodiment makes it possible to use the above-mentioned conventional GNSS signal processing device as is and effectively utilize its antenna monitoring function.

[0044] It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications are possible depending on the purpose. For example, the number of receiving devices can be set arbitrarily according to the requirements of the system, and the method of acquiring antenna monitoring information and optical network unit monitoring information, the form of those signals, the signal processing method, the method of multiplexing into received signals, etc. can be changed arbitrarily according to the purpose and use of the system. Furthermore, the optical network unit and receiving device can be provided with functions and means other than those shown in the embodiments depending on the purpose. [Explanation of symbols]

[0045] 1, 31 Built-in amplifier antenna 2, 32, 40 Optical Terminal Equipment 3, 33, 34, 35, 50, 60 Receiver 4 built-in amplifier 5 E / O converter 6. Intensity-modulated light 7, 37 Optical Fiber 8 O / E converter 9, 25, 41, 42, 43 Amps 10, 20 Radio wave receiving system 11 Antenna 12 Coaxial Cable 13, 19, 44 Amplifier power supply 14, 21, 45 Current monitor 15, 16 Bias Tee 17 Voltage Stabilizer Circuit 18, 46 Monitoring information generation circuit 22, 23, 27, 28, 53 frequency filters 24 High frequency power combiner 26 High frequency power divider 30, 65 Monitoring information processing circuit 38, 39 Optical Branching 47 Signal Generator 48 High Frequency Switch 51 Log Amplifier 52, 54, 55, 56 Comparators 61 GNSS signal processing device 62 Switch 63 Current 64 Current supply monitoring circuit

Claims

1. an antenna having a built-in amplifier for amplifying a received signal; an optical network unit having an E / O converter connected to the antenna and outputting intensity-modulated light corresponding to the received signal, the intensity-modulated light being output through an optical fiber; a receiving device connected to the optical fiber and having an O / E converter that converts the intensity-modulated light into an electrical signal; A radio wave receiving system comprising: The optical network unit comprises: means for acquiring antenna monitoring information for monitoring the operation of the antenna; means for acquiring optical network unit monitoring information for monitoring the operation of the optical network unit; The center frequency of the received signal is f 0 Then, f≦0.8f 0 and a signal multiplexing means for converting the antenna monitoring information and the optical network unit monitoring information into a signal modulated at a frequency f that satisfies the above formula and superimposing the converted signal on the received signal, The radio wave receiving system is characterized in that the receiving device has a signal separating means for separating and acquiring the antenna monitoring information and the optical terminal unit monitoring information from the intensity-modulated light.

2. 2. The radio wave receiving system according to claim 1, wherein the system comprises a plurality of receiving devices, the optical fiber for transmitting the intensity-modulated light output from the optical network unit has an optical branch, and the plurality of receiving devices are connected to the optical fiber branched by the optical branch.

3. 2. The radio wave receiving system according to claim 1, wherein the means for acquiring the antenna monitoring information measures a drive current of the built-in amplifier.

4. 2. The radio wave receiving system according to claim 1, wherein the optical network unit has an amplifier, and the means for acquiring the optical network unit monitoring information measures a drive current of the amplifier.

5. 2. The radio wave receiving system according to claim 1, wherein the signal multiplexing means and the signal separating means each use a directional coupler, a high frequency power divider, or a high frequency power combiner.

6. The antenna monitoring information is binary information indicating whether the magnitude of the drive current of the built-in amplifier is within a normal range or an abnormal range, and the optical network unit monitoring information is binary information indicating whether the optical network unit is in a normal operating state or an abnormal operating state, the signal multiplexing means includes means for cutting off the signal modulated with the frequency f to be superimposed on the received signal at a fixed period T, setting the time during which the signal modulated with the frequency f passes through within the period T as ON, and changing the duty ratio, i.e., ON / T, to superimpose the signal on the received signal; 2. The radio wave receiving system according to claim 1, wherein the duty ratio is set to a value corresponding to each of the binary information of the antenna monitoring information and the optical network unit monitoring information.

7. The optical terminal device has a data processing means for converting the antenna monitoring information and the optical terminal device monitoring information into multi-value digital data, respectively, and processing the digital data, and the data processing means is characterized in that the radio wave receiving system described in any one of claims 1 to 6 is equipped with a microcomputer.

8. 7. The radio wave receiving system according to claim 1, wherein the radio wave receiving system is used as a system for receiving radio waves from an artificial satellite in a satellite positioning system.

9. 8. The radio wave receiving system according to claim 7, wherein the radio wave receiving system is used as a system for receiving radio waves from an artificial satellite in a satellite positioning system.

10. the receiving device has a GNSS signal processing device that processes a GNSS signal obtained by receiving radio waves from an artificial satellite, and a current interruption means; the GNSS signal processing device has a current supply monitoring circuit that supplies a current to the outside of the GNSS signal processing device and monitors the current value; 9. The radio wave receiving system according to claim 8, wherein said current cut-off means cuts off said current depending on said antenna monitoring information and said optical network unit monitoring information.

11. the receiving device has a GNSS signal processing device that processes a GNSS signal obtained by receiving radio waves from an artificial satellite, and a current interruption means; the GNSS signal processing device has a current supply monitoring circuit that supplies a current to the outside of the GNSS signal processing device and monitors the current value; 10. The radio wave receiving system according to claim 9, wherein the current cutoff means cuts off the current depending on the antenna monitoring information and the optical network unit monitoring information.

Images