CN103532591B - Based on voltage Power Line Carrier Channel attenuation test system and the method thereof of orthogonal signalling - Google Patents

Abstract

The invention relates to a test system and a method thereof in the field of electric power communication, in particular to a power line carrier channel attenuation test system and a method based on an orthogonal signal. The test system includes a carrier signal sending end and a signal receiving end connected to the power line; the signal sending end includes an orthogonal signal output system, a sending coupling circuit, a data acquisition card and a controller connected in turn to form a closed-loop structure; the signal receiving end The terminal includes a receiving coupling circuit, a data acquisition card and a controller connected in sequence. A test method for the test system is also provided. The method utilizes the cosine (Cos) and sine (Sin) signals with orthogonal relationship to be transmitted on the narrowband output channel and the wideband output channel at the same time, and the present invention simultaneously outputs signals with orthogonal The cosine and sine signals of the relationship can easily distinguish the noise of the same frequency from the signal, and prevent the influence of noise on the attenuation test.

Description

Power Line Carrier Channel Attenuation Test System and Method Based on Orthogonal Signals

technical field

The invention relates to a test system and a method thereof in the field of electric power communication, in particular to a power line carrier channel attenuation test system and a method based on an orthogonal signal.

Background technique

At present, in the existing methods and devices for channel attenuation of power line carriers, if the received signal is almost submerged in the noise when the signal receiving end is noisy or the test line is long, it is difficult for the test device to The noise is separated from the signal, and sometimes the noise is mistaken for the signal for testing, so the attenuation of the power line carrier channel measured will be inaccurate.

Existing testing methods have the following deficiencies:

1) It is difficult to distinguish noise from signal.

2) The signal-to-noise ratio cannot be tested.

Contents of the invention

For the deficiencies in the prior art, the purpose of the present invention is to provide a power line carrier channel attenuation test system based on orthogonal signals, another purpose is to provide a power line carrier channel attenuation test method based on orthogonal signals, the present invention utilizes The cosine (Cos) and sine (Sin) signals of the orthogonal relationship are transmitted on the narrowband output channel and the wideband output channel at the same time, and the signal with the orthogonal relationship can be obtained at the output end, and the noise and signal of the same frequency can be easily separated Distinguished to prevent the impact of noise on the attenuation test.

The object of the present invention is to adopt following technical scheme to realize:

The present invention provides a power line carrier channel attenuation testing system based on orthogonal signals. The system includes a carrier signal sending end and a signal receiving end connected to the power line; Orthogonal signal output system of closed-loop structure, sending coupling circuit, data acquisition card and controller; the signal receiving end includes receiving coupling circuit, data acquisition card and controller connected in sequence; the attenuation Δ= U _R - U _S .

Further, the quadrature signal output system includes a quadrature signal generation module;

The quadrature signal generating module has two carrier channels, and the output signals are mutually orthogonal, wherein one carrier channel outputs a cosine signal, and the other carrier channel outputs a sine signal; the two signals are output through the quadrature signal output system respectively. The sequentially connected filter, signal amplifier, power amplifier and coupler are output to the power line.

Further, the controller at the signal sending end sends an instruction to the orthogonal signal output system to send out an orthogonal dual-channel carrier signal at a single frequency; it is coupled to the power line through a sending coupling circuit; the sending coupling circuit couples the signal on the power line, And utilize the data acquisition card to collect the time-domain signal on the power line, and finally transmit it to the controller, and the controller stores and processes the tested data to obtain the signal level U _S of the carrier signal sending end;

The controller at the signal sending end sends instructions to the orthogonal signal output system to send out a single-frequency orthogonal dual-channel carrier signal, which is coupled to the power line through the sending coupling circuit; the receiving coupling circuit at the signal receiving end couples the signal on the power line, and uses The data acquisition card collects the time-domain signal on the power line, and finally transmits it to the controller. The controller stores and processes the test data to obtain the signal level _UR of the carrier signal receiving end.

Further, the sending coupling circuit includes a varistor, a safety capacitor, a discharge resistor, a step-down transformer, a sending filter circuit and a bidirectional diode;

The varistor, the step-down transformer and the bidirectional diode are connected in parallel; the two safety capacitors are symmetrically connected between the varistor and the step-down transformer; both ends of each safety capacitor are connected with a discharge resistor; 2 groups The sending filter circuit is connected between the step-down transformer and the bidirectional diode; the output end of the bidirectional diode D1 is connected to the signal receiving end; the sending filter circuit is composed of a capacitor and an inductor connected in series;

Among them, the varistor is used to protect the sending coupling circuit and prevent lightning strikes and high-voltage pulses from damaging the sending coupling circuit; the safety capacitor is used to couple high-frequency signals and isolate the 50Hz power frequency from the test system; the discharge resistor is used in the When the power is off, discharge the electric energy stored in the safety capacitor (to prevent the tester from being charged by the charge in the capacitor when he touches the test terminal by mistake); the step-down transformer is used to adjust the impedance relationship between the input and output, so that the signal It can output the maximum power; the bidirectional diode is used to clamp the voltage (to prevent the excessive voltage from burning out the test instrument);

The data acquisition card needs to have a sampling rate of more than 10MS/s, and the withstand power of the input port is more than 10dBm;

The controller adopts PC or notebook computer.

Further, the receiving coupling circuit includes a piezoresistor, a safety capacitor, a discharge resistor, a step-down transformer, a receiving filter circuit and an automatic gain control unit;

The varistor, the step-down transformer and the bidirectional diode are connected in parallel; the two safety capacitors are symmetrically connected between the varistor and the step-down transformer; both ends of each safety capacitor are connected with a discharge resistor; 2 groups The receiving filter circuit is connected between the step-down transformer and the automatic gain control unit; the output terminal of the automatic gain control unit is connected to the signal sending end; the receiving filter circuit is composed of capacitors and inductors connected in series, and in the Capacitors are connected in parallel at both ends of the inductance; the automatic gain control unit adopts an AGC controller.

The present invention provides a kind of power line carrier channel attenuation test method based on orthogonal signals based on another purpose, and its improvement is that the system used in the method is a power line carrier channel attenuation test system, and the method includes the following steps:

A. Obtain the signal level U _S of the carrier signal sending end;

B. Obtain the signal level _UR of the carrier signal receiving end;

C. Determine the attenuation of the test system, the signal-to-noise ratio SNR _S at the sending end of the test system, and the SNR _R at the receiving end of the test system.

Further, in the step A, the controller at the signal sending end sends an instruction to the orthogonal signal output system to send out an orthogonal dual carrier signal of a single frequency point; it is coupled to the power line through a sending coupling circuit; the sending coupling circuit will Coupling the signal on the power line, and using the data acquisition card to collect the time domain signal on the power line, and finally transmitting it to the controller, the controller stores and processes the tested data to obtain the signal level U _S of the carrier signal sending end;

The signal level U _S at the sending end of the carrier signal is obtained by Fourier transforming the time-domain signal, and the expression is as follows:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\underset{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}{\overset{<span\; class="notranslate">\; \&infin;</span>}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; jwt</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

Among them: f(t) is the time-domain voltage signal collected by the signal data card, t represents the time, and ω represents the frequency of the signal test signal.

Further, in the step B, the controller at the signal sending end sends an instruction to the orthogonal signal output system to send out an orthogonal dual-channel carrier signal at a single frequency point, and couples to the power line through the sending coupling circuit; the receiving coupling circuit at the signal receiving end Coupling the signal on the power line, and using the data acquisition card to collect the time domain signal on the power line, and finally transmitting it to the controller, the controller stores and processes the tested data to obtain the signal level _UR of the carrier signal receiving end;

Furthermore, the signal level _UR at the signal receiving end is obtained by Fourier transforming the time-domain signal, and the expression is as follows:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\underset{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}{\overset{<span\; class="notranslate">\; \&infin;</span>}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; jwt</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

Among them: f(t) is the time-domain voltage signal collected by the signal data card, t represents the time, and ω represents the frequency of the signal test signal.

Further, the quadrature signal generating module of the quadrature signal output system has two carrier channels, wherein one carrier channel outputs a cosine signal, and the other carrier channel outputs a sine signal; the two signals respectively pass through the quadrature signal output system in sequence Connected filter, signal amplifier, power amplifier and coupler output to the power line;

The sine signal and the cosine signal are in an orthogonal relationship, that is, the phase difference is maintained at 90°, and the amplitudes of the two carrier signals change synchronously with the change of the power line carrier channel.

Further, in the step _C , the attenuation Δ= _UR -US at the signal sending end and the signal receiving end.

Further, in the step C, the signal-to-noise ratio SNR _S at the sending end of the test system is the signal level at the sending end minus the noise level at the sending end, that is: SNR _S =(Send Signal)-(Send Noise)= _US- (Send Noise);

The data acquisition card directly tests the voltage value of the signal changing with time. The noise level at the sending end is the voltage signal collected by the data acquisition card, and then obtained by Fourier transform. The expression is as in formula (1).

Further, in the step C, the signal-to-noise ratio SNR _R at the receiving end of the test system is the signal level at the receiving end minus the noise level at the receiving end, that is: SNR _R =(Receive Signal)-(Receive Noise)= _UR- (Receive Noise);

The data signal acquisition card directly tests the voltage value of the signal changing with time. The noise level at the receiving end is the voltage signal collected by the data acquisition card, and then obtained by Fourier transform. The expression is as in formula (1).

Compared with prior art, the beneficial effect of the present invention is:

1) This method uses the cosine (Cos) and sine (Sin) signals with an orthogonal relationship to be transmitted on two channels at the same time. Cosine and sine signals, this kind of signal with orthogonal relationship keeps a 90° phase in phase, which is equivalent to marking the signal, so it is easy to distinguish noise from signal and prevent noise from affecting the attenuation test , so that the attenuation can be tested more accurately. .

2) In the process of testing the attenuation by using signals with an orthogonal relationship, the present invention can accurately separate the noise and the signal at the same frequency, and test the level values of the noise and the signal respectively, so that the signal level can be used to subtract Noise level, and then get the signal-to-noise ratio.

3) The present invention can test the signal strength and noise strength at the sending end of the signal, thereby determining the signal-to-noise ratio of the sending end, and can also test the signal strength and noise strength of the receiving end at the receiving end, thereby determining the signal-to-noise ratio of the receiving end. .

Description of drawings

Fig. 1 is the functional block diagram of the attenuation test system provided by the present invention; Wherein: 1-orthogonal signal output system; 2-transmit coupling circuit; 3-receive coupling circuit; 4-data acquisition card; 5-controller;

Fig. 2 is a block diagram of an orthogonal signal output system at a signal transmitting end provided by the present invention;

Fig. 3 is the sine and cosine signal waveform figure that the quadrature signal generation module output provided by the present invention;

Fig. 4 is a curve diagram of the received signal changing with time provided by the present invention;

Fig. 5 is a curve diagram of sending/receiving signals changing with time provided by the present invention;

Fig. 6 is a topological structure diagram of the transmitting coupling circuit provided by the present invention;

Fig. 7 is a topological structure diagram of the receiving coupling circuit provided by the present invention.

Detailed ways

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The principle block diagram of the attenuation test system provided by the present invention is as shown in Figure 1, and comprises the carrier wave signal sending end and the signal receiving end that are connected on the power line; The signal sending end includes the orthogonal signal output system 1, sending Coupling circuit 2, data acquisition card 4 and controller 5; the signal receiving end includes receiving coupling circuit 3, data acquisition card 4 and controller 5 connected in sequence.

The quadrature signal output system includes a quadrature signal generating module; the quadrature signal generating module has two carrier channels, and the output signals are mutually orthogonal, wherein one carrier channel outputs a cosine signal, and the other carrier channel outputs a sine signal ; The two signals are respectively output to the power line through the sequentially connected filter, signal amplifier, power amplifier and coupler in the orthogonal signal output system.

The sending coupling circuit includes varistor V21, safety capacitor, discharge resistor, step-down transformer T, filter circuit and bidirectional diode D1; varistor V21, step-down transformer T and bidirectional diode D1 are connected in parallel; two safety capacitors C21 and C22 are symmetrically connected between the varistor V21 and the step-down transformer T; the two ends of the safety capacitor C21 are connected to the discharge resistor R21; the two ends of the safety capacitor C21 are connected to the discharge resistor R22; two groups of filter circuits C41-L1 and C42-L2 are connected between the step-down transformer and the bidirectional diode D1; the output terminal of the bidirectional diode D1 is connected to the signal receiving terminal; a protective resistor R4 is connected in parallel at both ends of the bidirectional diode D1, and R4 is grounded .

The filter circuit C41-L1 is composed of a capacitor C41 and an inductor L1 connected in series; the filter circuit C42-L2 is composed of a capacitor C42 and an inductor L2 connected in series; its topology diagram is shown in FIG. 6 .

Among them, the varistor V21 is used to protect the circuit and prevent damage to the circuit caused by lightning strikes and high-voltage pulses; the safety capacitor is used to couple high-frequency signals and isolate the 50Hz power frequency from the test system; the discharge resistor is used when the power is off Under normal circumstances, the electric energy stored in the safety capacitor is discharged to prevent the tester from being charged by the charge in the capacitor when he touches the test terminal by mistake; the step-down transformer T is used to adjust the impedance relationship between input and output, so that the signal can reach the maximum power The output; the bidirectional diode D1 is used to clamp the voltage to prevent excessive voltage from burning out the test instrument.

The receiving coupling circuit includes a varistor, a safety capacitor, a discharge resistor, a step-down transformer, a receiving filter circuit and an automatic gain control unit; the varistor V21, the step-down transformer T and the automatic gain control unit are connected in parallel; the two described The safety capacitors C21 and C22 are symmetrically connected between the varistor V21 and the step-down transformer T; the two ends of the safety capacitor C21 are connected to the discharge resistor R21; the two ends of the safety capacitor C21 are connected to the discharge resistor R22; 2 groups The receiving filter circuits C41-L1 and C42-L2 are connected between the step-down transformer and the automatic gain control unit;

The filter circuit C41-L1 is composed of a capacitor C41 connected in series and an inductor L1; the filter circuit C42-L2 is composed of a capacitor C42 connected in series and an inductor L2; A capacitor C45 is connected in parallel at both ends. The automatic gain control unit adopts an AGC controller, and its structural topology is shown in FIG. 7 .

The data acquisition card needs to have a sampling rate of more than 10MS/s, and the withstand power of the input port is more than 10dBm; the controller adopts a PC or a notebook computer.

The present invention also provides a method for testing power line carrier channel attenuation based on orthogonal signals, using the above-mentioned testing system, comprising the following steps:

A. Obtain the signal level U _S of the carrier signal sending end: the controller at the signal sending end sends an instruction to the orthogonal signal output system to send out a single frequency point orthogonal dual-way carrier signal; it is coupled to the power line through a sending coupling circuit; The sending coupling circuit couples the signal on the power line, and uses the data acquisition card to collect the time-domain signal on the power line, and finally transmits it to the controller, which stores and processes the tested data to obtain the signal level of the carrier signal sending end _US ;

B. Obtain the signal level U _R of the carrier signal receiving end: the controller at the signal sending end sends an instruction to the orthogonal signal output system to send out a single frequency point orthogonal dual-channel carrier signal, which is coupled to the power line through the sending coupling circuit; the signal receiving The receiving coupling circuit at the terminal couples the signal on the power line, and uses the data acquisition card to collect the time-domain signal on the power line, and finally transmits it to the controller, which stores and processes the tested data to obtain the signal at the receiving end of the carrier signal. Ping U _R .

The signal level U _S at the carrier signal sending end and the signal level U _R at the carrier signal receiving end are both obtained by Fourier transforming the time domain signal, and the expressions are as follows:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; [</span>\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; =</span>\underset{<span\; class="notranslate">\; -</span><span\; class="notranslate">\; \&infin;</span>}{\overset{<span\; class="notranslate">\; \&infin;</span>}{<span\; class="notranslate">\; \&Integral;</span>}}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; jwt</span>}}\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ;</span>$

Among them: f(t) is the time-domain voltage signal collected by the signal data card, t represents the time, and ω represents the frequency of the signal test signal.

The power line attenuation test system involved in the present invention utilizes dual-channel outputs of sine signals and cosine signals with an orthogonal relationship (phase difference of 90°) to perform power line carrier channel attenuation tests. As shown in Figure 2, the cosine signal (Y ₁ =A*Cos(ωt)) is output by the I channel, and the sine signal (Y ₂ =A*Sin(ωt)) is output by the Q channel. The phase difference of this kind of signal with orthogonal relationship will not change with the channel, and will always remain orthogonal, that is, the phase difference will always remain 90°, but the amplitude of the two carrier signals will change with the power line carrier channel And change synchronously. Therefore, by simultaneously collecting signals at the sending end and the receiving end, the level and amplitude of the signals at both ends can be obtained.

C. Determine the attenuation of the test system, the signal-to-noise ratio SNR _S at the sending end of the test system, and the SNR _R at the receiving end of the test system.

Step 1: The sending end first sends a signal of a single frequency point;

The second step: collect the time-domain signal of the signal through the high-speed data acquisition card at the sending end and the receiving end at the same time;

Step 3: Perform fast Fourier transform on the collected time-domain signal, and calculate the level value of the signal at this moment;

Step 4: Turn off the signal, and calculate the noise level through the method of the second and third steps above;

Step 5: Change to the next frequency point and repeat the signals from Step 2 to Step 4 above.

Carry out the test of all frequency points in turn.

In this way, the noise and signal at the sending end and receiving end can be tested sequentially.

Put the test data at the sending end and the data at the receiving end in the same coordinate system, and calculate the attenuation and signal-to-noise ratio.

As shown in Figure 5, the number 1 in the figure shows the signal level at the sending end (Send Signal), and the number 3 shows the signal level at the receiving end (Receive Signal), then the attenuation at the sending end and the receiving end is The signal level at the receiving end minus the signal level at the sending end: Attention=(Receive Signal)-(Send Signal) or Δ=U _R -U _S .

As shown in Figure 5, the number 1 in the figure shows the signal level of the sender (Send Signal), and the number 2 shows the level of noise at the sender (Send Noise), then the signal-to-noise ratio of the sender is The signal level at the end minus the noise level at the sending end, that is:

SNR _S = (Send Signal) - (Send Noise) = U _S - (Send Noise).

The data acquisition card directly tests the voltage value of the signal changing with time. The noise level at the sending end is the voltage signal collected by the data acquisition card, and then obtained by Fourier transform. The expression is as in formula (1).

As shown in Figure 5, the number 3 in the figure shows the signal level at the receiving end (Receive Signal), and the number 4 shows the noise level at the receiving end (Receive Noise), then the signal-to-noise ratio at the receiving end is The signal level at the receiving end minus the noise level at the receiving end, that is:

SNR _R = (Receive Signal) - (Receive Noise) U _R - (Receive Noise).

The data signal acquisition card directly tests the voltage value of the signal changing with time. The noise level at the receiving end is the voltage signal collected by the data acquisition card, and then obtained by Fourier transform. The expression is as in formula (1).

The test system and test method provided by the present invention are a test system and method for performing power line carrier channel attenuation by using dual output sine signals and cosine signals with an orthogonal relationship (phase difference of 90°). As shown in Figure 2, the cosine signal (Y ₁ =A*Cos(ωt)) is output by the I channel, and the sine signal (Y ₂ =A*Sin(ωt)) is output by the Q channel. The phase difference of this orthogonal signal will not change with the channel, but will always remain orthogonal, that is, the phase difference will always remain 90° (as shown in Figure 3), but the amplitude of the two carrier signals will vary. It changes synchronously with the change of the power line carrier channel. Therefore, this method can be used to measure the amplitude attenuation of the power line carrier channel.

This two-way carrier signal with a strictly orthogonal relationship is equivalent to marking the signal, so it can be distinguished from other noises of the same frequency. Therefore, using this method, the level of signal and noise can be accurately measured, and the signal-to-noise ratio (SNR) of the power line carrier signal can be tested more accurately.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims (6)

1. A power line carrier channel attenuation test system based on orthogonal signals, the system includes a carrier signal sending end and a signal receiving end connected to the power line; it is characterized in that the signal sending end includes sequentially connected into a closed-loop structure Orthogonal signal output system, sending coupling circuit, data acquisition card and controller; the signal receiving end includes receiving coupling circuit, data acquisition card and controller connected in sequence; the attenuation Δ= _UR at the signal sending end and signal receiving end- _US ; The controller at the signal sending end sends instructions to the orthogonal signal output system to send out a single-frequency orthogonal dual-channel carrier signal; it is coupled to the power line through the sending coupling circuit; the sending coupling circuit couples the signal on the power line, and uses the data The acquisition card collects the time-domain signal on the power line, and finally transmits it to the controller, and the controller stores and processes the tested data to obtain the signal level U _S of the carrier signal sending end; The controller at the signal sending end sends instructions to the orthogonal signal output system to send out a single-frequency orthogonal dual-channel carrier signal, which is coupled to the power line through the sending coupling circuit; the receiving coupling circuit at the signal receiving end couples the signal on the power line, and uses The data acquisition card collects the time-domain signal on the power line, and finally transmits it to the controller, and the controller stores and processes the tested data to obtain the signal level _UR of the carrier signal receiving end; The sending coupling circuit includes a varistor, a safety capacitor, a discharge resistor, a step-down transformer, a sending filter circuit and a bidirectional diode; The varistor, the step-down transformer and the bidirectional diode are connected in parallel; the two safety capacitors are symmetrically connected between the varistor and the step-down transformer; both ends of each safety capacitor are connected with a discharge resistor; 2 groups The sending filter circuit is connected between the step-down transformer and the bidirectional diode; the output end of the bidirectional diode D1 is connected to the signal receiving end; the sending filter circuit is composed of a capacitor and an inductor connected in series; Among them, the varistor is used to protect the sending coupling circuit and prevent lightning strikes and high-voltage pulses from damaging the sending coupling circuit; the safety capacitor is used to couple high-frequency signals and isolate the 50Hz power frequency from the test system; the discharge resistor is used in the When the power is off, discharge the electric energy stored in the safety capacitor; the step-down transformer is used to adjust the impedance relationship between input and output, so that the signal can output the maximum power; the bidirectional diode is used to clamp the voltage; The data acquisition card needs to have a sampling rate of more than 10MS/s, and the withstand power of the input port is more than 10dBm; Described controller adopts PC or notebook computer; The receiving coupling circuit includes a piezoresistor, a safety capacitor, a discharge resistor, a step-down transformer, a receiving filter circuit and an automatic gain control unit; The varistor, the step-down transformer and the bidirectional diode are connected in parallel; the two safety capacitors are symmetrically connected between the varistor and the step-down transformer; both ends of each safety capacitor are connected with a discharge resistor; 2 groups The receiving filter circuit is connected between the step-down transformer and the automatic gain control unit; the output terminal of the automatic gain control unit is connected to the signal sending end; the receiving filter circuit is composed of capacitors and inductors connected in series, and in the Capacitors are connected in parallel at both ends of the inductance; the automatic gain control unit adopts an AGC controller. 2. power line carrier channel attenuation test system as claimed in claim 1, is characterized in that, described orthogonal signal output system comprises orthogonal signal generation module; The quadrature signal generating module has two carrier channels, and the output signals are mutually orthogonal, wherein one carrier channel outputs a cosine signal, and the other carrier channel outputs a sine signal; the two signals are output through the quadrature signal output system respectively. The sequentially connected filter, signal amplifier, power amplifier and coupler are output to the power line. 3. A power line carrier channel attenuation test method based on orthogonal signals, characterized in that, the system used by the method is a power line carrier channel attenuation test system, and the method may further comprise the steps: A. Obtain the signal level U _S of the carrier signal sending end; B. Obtain the signal level _UR of the carrier signal receiving end; C. Determine the attenuation of the test system, the signal-to-noise ratio SNR _S at the sending end of the test system and the SNR _R at the receiving end of the test system; In the step A, the controller at the signal sending end sends an instruction to the orthogonal signal output system to send out an orthogonal dual-channel carrier signal at a single frequency point; it is coupled to the power line through a sending coupling circuit; Signal coupling, and use the data acquisition card to collect the time domain signal on the power line, and finally transmit it to the controller, and the controller stores and processes the tested data to obtain the signal level U _S of the carrier signal sending end; In the step B, the controller at the signal transmitting end sends an instruction to the orthogonal signal output system to issue an orthogonal dual-channel carrier signal of a single frequency point, which is coupled to the power line through the sending coupling circuit; the receiving coupling circuit at the signal receiving end connects the power line signal coupling, and use the data acquisition card to collect the time domain signal on the power line, and finally transmit it to the controller, and the controller stores and processes the tested data to obtain the signal level _UR of the carrier signal receiving end; The quadrature signal generating module of the quadrature signal output system has dual carrier channels, wherein one carrier channel outputs a cosine signal, and the other carrier channel outputs a sine signal; the two signals pass through successively connected filter channels in the quadrature signal output system respectively. The output of the device, signal amplifier, power amplifier and coupler to the power line; The sine signal and the cosine signal are in an orthogonal relationship, that is, the phase difference is maintained at 90°, and the amplitudes of the two carrier signals change synchronously with the change of the power line carrier channel. 4. The power line carrier channel attenuation testing method according to claim 3, characterized in that, in the step _C , the attenuation Δ= _UR -US at the signal sending end and the signal receiving end. 5. power line carrier channel attenuation test method as claimed in claim 3, is characterized in that, in described step C, test system sending end signal-to-noise ratio SNR _S is the signal level of sending end minus the noise level of sending end, i.e. : SNR _S =( _SendSignal )-(Send Noise)=US-(Send Noise). 6. power line carrier channel attenuation test method as claimed in claim 3, is characterized in that, in described step C, test system receiving end signal-to-noise ratio SNR _R is the signal level of receiving end minus the noise level of receiving end, i.e. : SNR _R = (Receive Signal) - (Receive Noise) = U _R - (Receive Noise).