JP2011214899A - Transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission system wherein radiation of an electromagnetic wave from a transmission cable is small.SOLUTION: The transmission system includes: a power source 101 for an amplifier for generating a first signal whose voltage is constant; an autobias circuit 102 for generating a second signal whose voltage changes with time; a combining circuit 103 for combining the first signal and the second signal and outputting their combined signal; a separation circuit 301 for separating the combined signal transmitted through a transmission line 50 into the first signal and the second signal; an LN modulator 303 which uses the second signal separated by the separation circuit 301 as a control signal, and converts an electric signal into an optical signal; and the amplifier 302 which operates by receiving supply of the first signal separated by the separation circuit 301 to operate, and supplies the electric signal to the LN modulator 303.

Description

  The present invention relates to a transmission system for transmitting an electrical signal.

As a method of measuring a weak electromagnetic wave radiated from a certain object, the electromagnetic wave is measured by installing the object in an anechoic chamber. In the anechoic chamber, in addition to the object to be measured, an antenna for receiving electromagnetic waves and a device for processing (amplifying) signals received by the antenna are also installed. In a measurement room away from the anechoic chamber, a signal measuring device and a controller for driving / controlling the device are installed. Between the anechoic chamber and the measurement chamber, in addition to the signal transmission cable for transmitting the antenna measurement signal (the signal processed by the device) to the measurement chamber, the drive cable for supplying drive power to the device Alternatively, a control signal cable for transmitting a control signal for controlling the device is laid.
Patent Document 1 discloses an electric field sensing device that measures electromagnetic interference (EMC).

JP 2003-014800 A

Here, if an electric cable (a conductor cable for transmitting an electrical signal) is used as a signal transmission cable for transmitting a measurement signal from the anechoic chamber to the measurement chamber, a signal transmission loss occurs when the frequency of the electromagnetic wave to be measured is 1 GHz or more. Suddenly increases, making measurement difficult. Therefore, it is conceivable to replace the signal transmission cable with an optical fiber and convert the antenna measurement signal into an optical signal and transmit it to the measurement room.
However, it is necessary to electrically transmit driving power and control signals to the devices in the anechoic chamber. For this reason, when the above-described driving cables and control signal cables are used, these multiple cables are used as electromagnetic wave sources. Therefore, there is a problem that it is difficult to improve the measurement accuracy of the target electromagnetic wave.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a transmission system that emits less electromagnetic waves from a transmission cable.

  The present invention has been made to solve the above problems, and a transmission system according to the present invention includes a first signal generation circuit that generates a first signal having a constant voltage, and a second signal whose voltage changes over time. A second signal generating circuit to be generated; a combining circuit that combines the first signal and the second signal and outputs a combined signal; and the combined signal transmitted through a transmission path is converted into the first signal and the second signal. A separation circuit for separation, an electro-optical conversion device that converts an electrical signal into an optical signal using the second signal separated by the separation circuit as a control signal, and a supply of the first signal separated by the separation circuit And a peripheral device that supplies the electric signal to the electro-optical conversion device or processes the optical signal from the electro-optical conversion device.

  According to the present invention, in the above transmission system, the synthesis circuit adds a voltage frequency conversion circuit that converts the second signal into a frequency modulation signal corresponding to the voltage, and adds the frequency modulation signal and the first signal. An adder circuit, and the separation circuit includes: a low-pass filter that extracts the first signal from the transmitted composite signal; and a frequency-voltage conversion circuit that converts the frequency of the transmitted composite signal into a voltage. It is characterized by providing.

  According to the present invention, in the transmission system, the combining circuit includes an adding circuit that adds the first signal and the second signal, and the separating circuit generates a constant voltage based on the transmitted combined signal. And a difference signal generation circuit that generates a difference signal between the transmitted composite signal and a constant voltage signal generated by the constant voltage generation circuit.

  According to the present invention, since the first signal and the second signal are combined and transmitted and separated after transmission, there is only one transmission path serving as an electromagnetic wave generation source, thereby reducing electromagnetic wave emission. Can do.

It is a figure which shows the structure of the electromagnetic wave measurement system to which the transmission system by 1st Embodiment was applied. It is a figure which shows the cross-section of a coaxial cable. It is a figure which shows the structure of the electromagnetic wave measurement system to which the transmission system by 2nd Embodiment was applied. It is a figure which shows the structure of the electromagnetic wave measurement system to which the transmission system by 3rd Embodiment was applied.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing a configuration of an electromagnetic wave measurement system to which a transmission system according to a first embodiment of the present invention is applied. In FIG. 1, the electromagnetic wave measurement system includes an antenna 40 and a head 30 in an anechoic chamber, and a controller 10 and a measuring instrument 20 in a measurement chamber away from the anechoic chamber. A coaxial cable 50, an input optical fiber 60, and an output optical fiber 70 are laid between the controller 10 in the measurement room and the head 30 in the anechoic chamber.

  The antenna 40 receives an electromagnetic wave radiated from an object to be measured (not shown) installed in the anechoic chamber, and outputs an electrical signal corresponding to the electromagnetic wave to the head 30.

  The head 30 includes a separation circuit 301, an amplifier 302, and an LN modulator 303.

  The separation circuit 301 converts an electrical signal (described later) from the controller 10 transmitted through the coaxial cable 50 into a drive voltage signal serving as drive power for the amplifier 302 and a control signal for controlling the LN modulator 303. To separate. The drive voltage signal is a signal having a constant voltage. The control signal is a signal whose voltage changes with time. The specific configuration of the separation circuit 301 will be described in the second and third embodiments.

  The amplifier 302 is a device that amplifies the electric signal from the antenna 40 and operates using the power of the driving voltage signal supplied from the separation circuit 301 as the driving power.

  The LN modulator 303 is a device (optical modulator) that converts the electrical signal amplified by the amplifier 302 into an optical signal, modulates the light input from the input optical fiber 60 with the electrical signal from the amplifier 302, and The modulated light is output to the output optical fiber 70. This modulated light is transmitted to the controller 10 through the output optical fiber 70. When modulating the input light, the LN modulator 303 modulates the input light using the control signal supplied from the separation circuit 301 as a bias voltage. That is, the operating point of the LN modulator 303 is controlled by the control signal from the separation circuit 301.

  The controller 10 includes an amplifier power supply 101, an auto bias circuit 102, a synthesis circuit 103, a light source 104 (LD; laser diode), an optical coupler 105, a receiver 106, and a light receiving element 107 (PD: photodiode). It has.

  The amplifier power supply 101 is a drive power supply for the amplifier 302 described above, and generates a drive voltage signal having a constant voltage as drive power for the amplifier 302.

  The auto bias circuit 102 is a circuit that generates a control signal for controlling the operating point of the LN modulator 303, so that the output signal of the light receiving element 107 becomes a predetermined constant value, that is, the output light of the LN modulator 303. The voltage value of the control signal is adjusted so that the intensity becomes a predetermined constant value. The LN modulator 303 may exhibit a drift phenomenon in which an operation curve representing the relationship between the applied voltage and the output light intensity fluctuates. When the drift phenomenon occurs, the output light intensity of the LN modulator 303 changes, and thereby the light receiving element Since the output signal 107 also changes, the auto bias circuit 102 performs the above adjustment of the control signal so that this change is compensated. Therefore, the voltage of the control signal changes with time.

  The synthesizing circuit 103 synthesizes the drive voltage signal (constant voltage) output from the amplifier power supply 101 and the control signal (voltage is time-varying) output from the auto-bias circuit 102 to generate the combined electric signal. The signal is output to the coaxial cable 50. This electric signal is transmitted to the head 30 by the coaxial cable 50. A specific configuration of the synthesis circuit 103 will be described in the second and third embodiments.

  The light source 104 generates laser light. This light is introduced into the input optical fiber 60 and transmitted to the head 30 through the input optical fiber 60.

  The optical coupler 105 branches the light from the output optical fiber 70, outputs one of them to the receiver 106, and outputs the other to the light receiving element 107.

  The receiver 106 (a photodiode similar to the light receiving element 107) converts the output light from the optical coupler 105, which is a part of the output light of the LN modulator 303, into an electrical signal and outputs the electrical signal.

  The light receiving element 107 converts the output light from the optical coupler 105 that is a part of the output light of the LN modulator 303 into an electrical signal and outputs the electrical signal to the auto bias circuit 102.

  The measuring device 20 measures the intensity of the electromagnetic wave received by the antenna 40 based on a signal corresponding to the output light intensity of the LN modulator 303 output from the receiver 106.

FIG. 2 is a diagram showing a cross-sectional structure of the coaxial cable 50.
As shown in the figure, a signal line 51 made of a conductor is provided at the center of the coaxial cable 50, and an insulator 52 is provided around the signal line 51 concentrically with the signal line 51. A ground line 53 made of a conductor concentrically with the signal line 51 is provided around the periphery, and a coating 54 made of an insulating material is provided on the outermost periphery.

  For transmission of an electrical signal from the controller 10 to the head 30, only one such coaxial cable 50 is laid, and the drive voltage signal synthesized by the synthesis circuit 103 is controlled in the one coaxial cable 50. A composite signal is transmitted. Therefore, since the number of cables that transmit electrical signals is as small as one, radiation of electromagnetic waves from the cables can be reduced.

(Second Embodiment)
FIG. 3 is a diagram showing a configuration of an electromagnetic wave measurement system to which the transmission system according to the second embodiment of the present invention is applied. The electromagnetic wave measurement system of the present embodiment is a first example that embodies the configuration of the synthesis circuit 103 and the separation circuit 301, and the other parts have the same configuration as that of the above-described embodiment. Hereinafter, the description of the common part is omitted, and a specific configuration of the synthesis circuit 103 and the separation circuit 301 will be described.

  In FIG. 3, the synthesis circuit 103 includes a voltage frequency conversion circuit 1031 and an addition circuit 1032. The separation circuit 301 includes a low-pass filter 3011 and a frequency / voltage conversion circuit 3012.

  The voltage frequency conversion circuit 1031 converts the control signal S2 output from the auto bias circuit 102 into a modulation signal S3 having a frequency corresponding to the voltage of the control signal S2, and outputs the modulation signal S3 to the addition circuit 1032. As illustrated, the control signal S2 indicates, for example, a first voltage value in a certain period, and a second voltage value higher than the first voltage value in a certain period thereafter. When such a control signal S2 is converted by the voltage frequency conversion circuit 1031, the modulation signal S3 becomes a low frequency sine wave signal in the first period, and a higher frequency sine wave signal in the second period. Become.

  Thus, one input to the adder circuit 1032 is a modulation signal S3 whose voltage varies with time in an alternating manner. The other input to the adder circuit 1032 is a drive voltage signal S1 output from the amplifier power supply 101. As shown in the figure, the drive voltage signal S1 indicates a constant voltage value that does not change with time.

  The adder circuit 1032 adds the drive voltage signal S1 from the amplifier power supply 101 and the modulation signal S3 from the voltage frequency conversion circuit 1031 and outputs a signal S4 in which the signal S3 is superimposed on the signal S1 to the coaxial cable 50. The superimposed signal S4 is transmitted through the coaxial cable 50 and input to the low-pass filter 3011 and the frequency / voltage conversion circuit 3012.

  The low pass filter 3011 extracts a direct current component included in the superimposed signal S4 'after transmission. As a result, a drive voltage signal S5 having a constant voltage corresponding to the drive voltage signal S1 generated by the amplifier power supply 101 is obtained, and drive power is supplied to the amplifier 302.

  The frequency voltage conversion circuit 3012 converts the superimposed signal S4 'after transmission into a signal S6 having a voltage corresponding to the frequency of the superimposed signal S4'. As shown in the figure, for example, the voltage value of the signal S6 is low during the period when the superimposed signal S4 ′ has a low frequency, and the voltage value of the signal S6 is low during the period when the superimposed signal S4 ′ has a high frequency. Get higher. Thus, the control signal S6 indicating the time change of the voltage corresponding to the control signal S2 generated by the auto bias circuit 102 is obtained, and the modulation by the LN modulator 303 is performed according to the control signal S6.

(Third embodiment)
FIG. 4 is a diagram showing a configuration of an electromagnetic wave measurement system to which the transmission system according to the third embodiment of the present invention is applied. The electromagnetic wave measurement system of the present embodiment is a second example that embodies the configuration of the synthesis circuit 103 and the separation circuit 301, and the other parts have the same configuration as the above-described embodiment. Hereinafter, the description of the common part is omitted, and a specific configuration of the synthesis circuit 103 and the separation circuit 301 will be described.

  In FIG. 4, the synthesis circuit 103 includes an addition circuit 1033. In addition, the separation circuit 301 includes a regulator 3013 and a difference signal generation circuit 3014.

  The adder circuit 1033 adds the drive voltage signal S1 from the amplifier power supply 101 and the control signal S2 from the auto bias circuit 102, and outputs a signal S7 in which the signal S2 is superimposed on the signal S1 to the coaxial cable 50. The superimposed signal S7 is transmitted through the coaxial cable 50 and input to the regulator 3013 and the difference signal generation circuit 3014. The drive voltage signal S1 and the control signal S2 are the same as those in the second embodiment.

  The regulator 3013 generates a signal S8 having a constant voltage from the superimposed signal S7 'after transmission. The amplifier 302 is driven in response to power supply by this signal (drive voltage signal) S8.

  The difference signal generation circuit 3014 generates a difference signal S9 indicating a difference voltage (a voltage obtained by subtracting the voltage of the signal S8 from the voltage of the signal S7 ′) between the superimposed signal S7 ′ after transmission and the output signal S8 of the regulator 3013. . As a result, a control signal S9 indicating a time change of the voltage corresponding to the control signal S2 generated by the auto bias circuit 102 is obtained, and modulation by the LN modulator 303 is performed according to the control signal S9. Note that the difference signal generation circuit 3014 can be configured as a known circuit using an operational amplifier, a resistor, or the like.

As described above, the embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to that described above, and various design changes and the like can be made without departing from the scope of the present invention. It is possible to
For example, power based on the drive voltage signal supplied from the separation circuit 301 may be used as drive power for driving a device other than the amplifier 302. An example of such an apparatus is an optical apparatus that applies optical processing (changing intensity, changing phase, changing polarization state, photoelectric conversion, etc.) to modulated light from the LN modulator 303. However, the present invention is not limited to the specific examples.

  DESCRIPTION OF SYMBOLS 10, 11, 12 ... Controller 20 ... Measuring instrument 30, 31, 32 ... Head 40 ... Antenna 50 ... Coaxial cable 51 ... Signal line 52 ... Insulator 53 ... Ground wire 54 ... Covering 60 ... Input optical fiber 70 ... For output Optical fiber 101 ... Power supply for amplifier 102 ... Auto bias circuit 103 ... Synthetic circuit 104 ... Light source 105 ... Optical coupler 106 ... Receiver 107 ... Light receiving element 301 ... Separation circuit 302 ... Amplifier 303 ... LN modulator 1031 ... Voltage frequency conversion circuit 1032 DESCRIPTION OF SYMBOLS 1033 ... Adder circuit 3011 ... Low pass filter 3012 ... Frequency voltage conversion circuit 3013 ... Regulator 3014 ... Difference signal generation circuit

Claims (3)

A first signal generating circuit for generating a first signal having a constant voltage;
A second signal generating circuit for generating a second signal whose voltage changes over time;
A combining circuit that combines the first signal and the second signal and outputs a combined signal;
A separation circuit that separates the combined signal transmitted through the transmission path into the first signal and the second signal;
Using the second signal separated by the separation circuit as a control signal, and converting the electric signal into an optical signal;
A peripheral device that operates in response to the supply of the first signal separated by the separation circuit, supplies the electric signal to the electro-optical converter, or processes the optical signal from the electro-optical converter;
A transmission system comprising: The synthesis circuit is:
A voltage frequency conversion circuit for converting the second signal into a frequency modulation signal corresponding to the voltage;
An adding circuit for adding the frequency modulation signal and the first signal;
With
The separation circuit is
A low pass filter for extracting the first signal from the transmitted combined signal;
A frequency voltage conversion circuit for converting the frequency of the transmitted composite signal into a voltage;
The transmission system according to claim 1, further comprising: The synthesis circuit is:
An adder circuit for adding the first signal and the second signal;
The separation circuit is
A constant voltage generation circuit for generating a constant voltage based on the transmitted composite signal;
A difference signal generation circuit that generates a difference signal between the transmitted composite signal and a constant voltage signal generated by the constant voltage generation circuit;
The transmission system according to claim 1, further comprising:

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