JP2017053731A - Remote antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cost-reducible and miniaturizable remote antenna system having safety against a lightening damage.SOLUTION: A radio wave signal of a micro wave received by an antenna 1 is converted into an optical signal at the same frequency of the radio wave in a reception part 11 and transferred to a demodulation part 21 by an optical fiber 31, and the optical signal is converted into an electric signal in the demodulation part 21. An electric composite cable 30 having an optical fiber 31, a feeder line 32, and a control line 33 connects between the reception part 11 and the demodulation part 21. The reception part 11 includes: an E/O converter 12, a reception part power supply 14, and a thunder detection device 15. The demodulation part 21 includes: an O/E converter 22; a power supply 24; and a control circuit 25 for detecting the output signal of the thunder detection device 15 through the control line 33 so as to output a control signal, and cutoff switches 36 and 37 installed on a feeder 32 and the control line 33 of the demodulation part 21, respectively.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a remote antenna system that transmits an electric signal obtained by receiving a radio signal with an antenna to a device installed at a location away from the antenna.

  Remote antenna system for observing the state of radio signals at a specific point where observation equipment cannot be installed easily, by installing an antenna at that point and transmitting the received signal to the point where the observation equipment is installed Is used.

  Usually, such a system uses a method of transmitting a signal between an antenna and an observation apparatus using an electric cable such as a coaxial cable. It is also conceivable to apply a method of converting an optical signal into an optical signal using an optical modulator as in the radio wave reception / optical transmission system described in Patent Document 1.

JP 2013-42453 A

  When the frequency of radio waves is low and the transmission distance from the antenna to the observation device is short, there is no particular problem with signal transmission using a coaxial cable as in the conventional case. However, when the frequency of radio waves becomes high as in the case of microwaves and the transmission distance is about 100 m or more, the transmission loss of the coaxial cable increases, and amplification by an amplifier becomes indispensable. In particular, the loss is large in the frequency region above the SHF band, and a multistage amplifier is required. That is, if an attempt is made to configure a remote antenna system in this manner for microwave radio waves, the apparatus becomes larger and the apparatus cost also increases. In addition, since the antenna is usually installed at a high place, there is a problem that the safety of the device is not sufficient against lightning damage.

  On the other hand, in the case of the radio wave reception / optical transmission system described in Patent Document 1, a long transmission distance is made possible by receiving radio waves in the SHF band, converting them into optical signals using an optical modulator, and transmitting them using optical fibers. In this system, in order to ensure safety against lightning damage, power is supplied to the device of the antenna receiving unit by optical energy using an optical fiber for power supply. However, this system requires one or two optical fibers for supplying unmodulated light to the optical modulator, transmitting modulated light, and supplying power, and therefore requires a total of three or more optical fibers. In addition, since two or more light sources are required for modulation and power, and a power conversion circuit for the receiver is required, the size and cost of the device can be reduced for use as a remote antenna system. It is difficult to plan.

In the remote antenna system, it is desirable to be able to carry the device with a small size in order to observe the state of the radio signal at various points. Further, it is desirable to be low-cost and safe against lightning damage. Conventional systems cannot adequately meet these requirements.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a remote antenna system that solves the above-described problems, can be reduced in size and cost, and has safety against lightning damage.

  In order to solve the above-mentioned problem, according to a first aspect, a remote antenna system according to the present invention converts a microwave radio signal received by an antenna into an optical signal at the receiving unit while maintaining the frequency of the radio signal, and demodulates it using an optical fiber. In a remote antenna system for transmitting to a signal and converting the optical signal into an electric signal in the demodulator, an opto-electric composite including at least the optical fiber, a feeder line and a control line between the receiver and the demodulator Connected by a cable, the receiving unit converts an electrical signal obtained by receiving the radio wave signal into an optical signal, a receiving unit power source for supplying power to the E / O converter, and the vicinity of the antenna A lightning detector for detecting lightning generated in the light source, and the demodulating unit converts the optical signal into an electric signal, supplies power to the O / E converter, and A power supply for supplying power to the receiver power supply through the feeder line, and a control circuit for detecting an output signal of the lightning detector through the control line and outputting a control signal depending on the output signal, It has a cut-off switch installed in one of the power supply lines, and the cut-off switch is cut off by the control signal.

  As described above, in the present invention, a microwave radio wave signal received by an antenna is converted into an optical signal at the receiving unit while maintaining the frequency of the radio wave signal, and transmitted to the demodulating unit using an optical fiber. Since the signal transmission loss is small compared with the case where an electric cable such as is used, an amplifier is not necessary. In addition, an E / O converter that converts an electrical signal into an optical signal and a receiving unit power source that supplies power to the E / O converter are installed in the receiving unit, and generate an optical signal only with the function of the receiving unit. Unlike conventional radio wave reception / optical transmission systems, no modulated light for generating an optical signal, a light source for supplying power, and an optical fiber for supplying them are not required. For this reason, simplification, size reduction, and cost reduction of an apparatus are attained. In the present invention, since a general-purpose photoelectric composite cable including two optical fibers, two control lines, and two power lines can be used, the cost can be further reduced.

  Furthermore, the present invention has a lightning detector that detects lightning generated near the antenna in the receiving unit, detects the output signal of the lightning detector through the control line in the demodulating unit, and shuts off the power supply line and the control line This can prevent the demodulator from being damaged by lightning. In this case, the output signal from the lightning detector is input to the control circuit of the demodulator, and the lightning detector or control circuit has a function to determine whether or not lightning damage is at an expected level. Thus, a control signal is output from the control circuit, and the cutoff switch installed in any of the feeder lines is set to the cutoff state. Thereby, in the remote antenna system of this invention, the safety | security of the apparatus with respect to a lightning damage can fully be maintained.

  In a second aspect, the present invention provides the antenna characteristic measurement method according to the first aspect, further comprising: a cutoff switch installed on one of the control lines, wherein the cutoff switch is blocked by the control signal. It is characterized by. If the lightning detector itself has a function to block the electrical path inside the lightning detector for protection when it detects lightning exceeding the allowable level, it is not necessary to cut off the control line, but it goes through the lightning detector. If there is a possibility that the device of the demodulating unit may break down, it is necessary to install a cut-off switch on one of the control lines and cut it off with a control signal.

  According to a third aspect, in the remote antenna system according to the second aspect, the present invention is characterized in that a cutoff switch for the feeder line and the control line is installed in the demodulator. The power supply line and control line cutoff switch need only be installed anywhere from the receiver to the demodulator, but it can be controlled by installing it in the demodulator where the control circuit is installed. The signal transmission time is shortened, and the probability of interruption before the lightning surge voltage reaches is improved.

  In a fourth aspect, the present invention provides the remote antenna system according to any one of the first to third aspects, wherein the lightning detector has a function of detecting a change in electric field or generation of electric charge accompanying generation of thunderclouds. And Lightning detectors that detect changes in electric fields or electric charges associated with thunderclouds can detect lightning and lightning events before lightning strikes. Is possible.

  In a fifth aspect, the present invention provides the remote antenna system according to any one of the first to fourth aspects, wherein the lightning detector has a function of detecting an electromagnetic wave generated by lightning discharge. By detecting electromagnetic waves generated in the vicinity of the antenna, such as lightning and lightning, it is possible to more directly determine the possibility of a lightning surge voltage. Furthermore, by providing a function for detecting the change in electric field or the generation of electric charge accompanying the occurrence of thunderclouds, it is possible to operate the cutoff switch more appropriately and prevent the device from being broken.

  In a sixth aspect, the present invention provides the remote antenna system according to any one of the first to fifth aspects, wherein the E / O converter directly modulates the output of the semiconductor laser light source by an electric signal applied to the semiconductor laser light source. It is a type E / O converter. In the present invention, since the transmission distance of the optical signal is mainly assumed to be 1 km or less, the E / O converter is special for suppressing chirping and dispersion even if the frequency of the optical signal is in the microwave region. In many cases, it is possible to employ a general-purpose semiconductor laser direct modulation method that does not use a simple circuit or device. This facilitates cost reduction and miniaturization.

  In a seventh aspect, the present invention provides the remote antenna system according to any one of the first to fifth aspects, wherein the E / O converter modulates output light of a light source having a constant output by an external modulator. It is a / O converter. When the optical signal is in the high frequency region of the microwave region, or when the demand for signal degradation is severe due to high-accuracy observation of the radio signal waveform, E / O of the external modulation method that makes it easier to obtain higher transmission quality A converter may be used.

  As described above, according to the present invention, a remote antenna system that can be reduced in size and cost and has safety against lightning damage can be obtained.

The block block diagram of the remote antenna system which concerns on an Example. The block block diagram of the E / O converter of a direct modulation system. The block block diagram of the E / O converter of an external modulation system.

  Hereinafter, the remote antenna system of the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description thereof is omitted.

FIG. 1 is a block diagram of a remote antenna system according to the embodiment. In FIG. 1, a remote antenna system 10 according to the present embodiment converts a microwave radio signal received by an antenna 1 into an optical signal at a receiving unit 11 without changing the frequency of the radio signal, and transmits the optical signal to a demodulating unit 21 through an optical fiber 31. In the remote antenna system, the demodulator 21 converts the optical signal into an electrical signal. Here, the receiving unit 11 and the demodulating unit 21 are connected by an optical / electrical composite cable 30 including an optical fiber 31, a feeder line 32, and a control line 33.
The receiving unit 11 is an E / O converter 12 that converts an electric signal obtained by receiving a radio wave signal into an optical signal, a receiving unit power supply 14 that supplies power to the E / O converter 12, and lightning generated near the antenna. And a lightning detector 15 for detection. The demodulator 21 includes an O / E converter 22 that converts an optical signal into an electric signal, a power supply 24 that supplies power to the O / E converter 22 and supplies power to the receiver power supply 14 through a feeder line 32, The control circuit 25 detects an output signal of the lightning detector 15 through the control line 33 and outputs a control signal depending on the output signal. Furthermore, in the present embodiment, there are cutoff switches 36 and 37 installed on the power supply line 32 and the control line 33 of the demodulator 21 respectively. These shutoff switches 36 and 37 are shut off by the control signal.

  In FIG. 1, a microwave radio wave signal such as an SHF band is received by an antenna 1 made up of a parabolic antenna or the like installed in a steel tower or the like, and is input to an amplifier 13 of a receiving unit 11 as an electric signal, amplified, and E / O Input to the converter 12. The optical signal output from the E / O converter 12 enters the optical fiber 31. The power of the E / O converter 12, the amplifier 13, and the lightning detector 15 is supplied from the receiver power supply 14, and the power of the receiver power supply 14 is supplied from the power supply 25 of the demodulator 21 through the feeder line 32. The photoelectric composite cable 30 may include a signal line and an optical fiber other than the feeder line 32, the control line 33, and the optical fiber 31. Further, in order to make the receiving unit portable, it is desirable that one receiving unit 11 is accommodated in a package. In this case, a connector for connection between the signal cable of the antenna 1 and the photoelectric composite cable 30 is used. It is desirable to have. In addition, the package must be waterproof to be used outdoors.

  The lightning detector 15 has either a function of detecting a change in electric field or generation of electric charge due to the occurrence of a thundercloud, a function of detecting electromagnetic waves generated by a lightning discharge, or a function of both of them. You may do it.

  In the demodulator 21, the optical signal input from the optical fiber 31 is converted into an electric signal by the O / E converter 22 and amplified by the amplifier 23. In this embodiment, the amplified electric signal is input to the measuring device 28 and the receiving converter 26. If the purpose of the remote antenna system 10 is only to evaluate the quality of radio waves such as radio wave intensity, frequency characteristics, and noise level, only the measuring device 28 such as a spectrum analyzer may be used. However, when evaluating the quality of a signal obtained by demodulating a radio signal, the reception converter 26 and the demodulator 27 are required. The reception converter 26 and the demodulator 27 are indispensable also when there is a possibility that the remote antenna system 10 may be used for an emergency backup line of a receiving device at a normal receiving station.

  The output signal from the lightning detector 15 that is input to the control circuit 25 through the control line 33 is a level at which the level of the output signal may be affected by lightning by the comparison circuit, the determination circuit, etc. in the control circuit 25. When it is determined that there is a possibility of lightning damage, a control signal for turning off the shutoff switches 36 and 37 is output. As a result, it is possible to prevent a failure due to lightning damage to the device of the demodulator 21. After the shutoff switches 36 and 37 are shut off, the shutoff switches 36 and 37 are temporarily connected at regular intervals, the thunder cloud status is confirmed by the output signal of the lightning detector 15, and the possibility of lightning damage disappears. After the safety is confirmed, the restoration of the shutoff switches 36 and 37 is determined.

  FIG. 2 is a block diagram of a direct modulation type E / O converter that can be used in this embodiment. An output signal of the amplifier 13 is input to the LD drive circuit 42, and a current-modulated electric signal is applied to the semiconductor laser 41. As a result, an optical signal whose intensity is modulated in accordance with the electrical signal is input to the optical fiber 31.

  FIG. 3 is a block diagram of an external modulation type E / O converter that can be used in this embodiment. The output of the light source 43 composed of a semiconductor laser or the like is input to the optical modulator 44, the output signal from the amplifier 13 is input to the modulator drive circuit 45, and the voltage-modulated electrical signal is applied to the optical modulator 44. As a result, an optical signal whose intensity is modulated in accordance with the electrical signal is input to the optical fiber 31. As the optical modulator, an optical waveguide type optical modulator using a lithium niobate crystal, a semiconductor optical modulator, or the like can be used.

  Needless to say, the present invention is not limited to the above-described embodiments, and various modifications can be made according to the purpose. For example, the receiving unit and the demodulating unit may include devices, circuits, elements, and the like other than the devices and circuits shown in the embodiments. When the optical / electrical composite cable includes the signal line and optical fiber other than the power supply line, control line, and optical fiber of the embodiment, it is possible to provide other functions by performing signal transmission between the receiving unit and the demodulating unit. Also good. In addition, the power of the lightning detector may be obtained from a battery or the like instead of from the power supply of the receiver.

1 Antenna 10 Remote Antenna System 11 Receiver 12 E / O Converter
DESCRIPTION OF SYMBOLS 13, 23 Amplifier 14 Reception part power supply 15 Lightning detector 21 Demodulation part 22 O / E converter 24 Power supply 25 Control circuit 26 Reception converter 27 Demodulator 28 Measuring instrument 30 Photoelectric composite cable 31 Optical fiber 32 Feeding line 33 Control line 36, 37 Cutoff switch 41 Semiconductor laser 42 LD drive circuit 43 Light source 44 Optical modulator 45 Modulator drive circuit

Claims (7)

A remote antenna system that converts a microwave radio signal received by an antenna into an optical signal at the receiving unit while maintaining the frequency of the radio signal and transmits the optical signal to a demodulating unit through an optical fiber, and converts the optical signal into an electrical signal in the demodulating unit In
The receiver and the demodulator are connected by an optical / electrical composite cable including at least the optical fiber, a feeder line and a control line,
The receiving unit includes an E / O converter that converts an electric signal obtained by receiving the radio signal into an optical signal, a receiving unit power source that supplies power to the E / O converter, and lightning generated near the antenna. A lightning detector to detect,
The demodulator is an O / E converter that converts the optical signal into an electrical signal; a power source that supplies power to the O / E converter and that supplies power to the receiver power source through the feeder line; A control circuit for detecting an output signal of the lightning detector through a control line and outputting a control signal depending on the output signal;
A remote antenna system comprising: a cut-off switch installed on any one of the feeder lines, wherein the cut-off switch is cut off by the control signal.   The remote antenna system according to claim 1, further comprising: a cutoff switch installed on any one of the control lines, wherein the cutoff switch is blocked by the control signal.   The remote antenna system according to claim 2, wherein the power supply line and the control line cutoff switch are installed in the demodulation unit.   4. The remote antenna system according to claim 1, wherein the lightning detector has a function of detecting a change in an electric field or generation of an electric charge accompanying generation of a thundercloud.   5. The remote antenna system according to claim 1, wherein the lightning detector has a function of detecting an electromagnetic wave generated by a lightning discharge. 6.   6. The E / O converter according to claim 1, wherein the E / O converter is an E / O converter of a type that directly modulates an output of a semiconductor laser light source by an electric signal applied to the semiconductor laser light source. The remote antenna system according to item 1.   6. The E / O converter according to claim 1, wherein the E / O converter is an E / O converter that modulates output light of a light source having a constant output by an external modulator. The described remote antenna system.

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