Double-port network parameter measuring method

Abstract

The double port network parameter measuring method includes: correcting the sampling channels and obtaining the sampling channel difference parameter; measuring the input voltage on the sampling resistor and that of the double port network with the corrected the sampling channels; and obtaining the true voltage values with the channel difference parameter and the measured voltage values and calculating the impedance parameters of the double port network with relevant formula. The present invention has raised measurement accuracy.

Description

technical field [0001] The invention relates to the field of telecommunications, in particular to a dual-port network parameter testing method. Background technique [0002] In the field of telecommunications, operators provide users with broadband telecommunications services and narrowband telecommunications services at the same time through local telephone cables (usually twisted pairs), such as ADSL over POTS (ADSL is added to ordinary telephones), ADSL over ISDN (ADSL is added to ISDN) , VDSL over POTS (add VDSL for ordinary telephones), VDSL over ISDN (add VDSL for ISDN), and other services, such applications are quite common at home and abroad. [0003] During the operation and maintenance of such services, for example, when a user reports a fault, it is often necessary to measure user line parameters, such as: line voltage parameters, line resistance parameters, line capacitance parameters, line insertion loss, line background noise, line-to-ground balance etc. Base...

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Problems solved by technology

[0012] The defect of this method is that the signal before the sampling resistor is considered to be equal to the sending signal source Vs. However, compared with the real signal Va before the sampling resistor and the signal source Vs, due to the channel attenuation error of the source output channel, the amplitude of the signal is attenuated and the phase is attenuated. If there is an offset, then use the signal source Vs instead of the real signal Va to calculate the parameters of the two-port network, which will eventually greatly affect the accuracy of the Z parameter;

[0017] For the second method, although the direct test of the output voltage value Va through the sampling resistor does not use Vs as an approximate replacement, it relatively avoids the test error caused by the attenuation of the signal source output channel, and improves the test compared with the first method. Accuracy. However, after any signal passes through the sampling channel, the amplitude will be attenuated (DC or AC), and the phase will be offset (AC). Due to the inherent loss of the sampling channel, the obtained test value will deviate from the real value; At the same time, there are unavoidable differences in parameters between the two sampling channels, so the real voltage of the test point, the degree of amplitude attenuation and phase shift on the two channels will also be different. The test value when measuring Z11 is Example: For voltage parameters: Va≠V1, VZ1≠V2; in addition, because the attenuation degree of each sampling channel to the signal is different, so there are where A1 and A2 are real or complex numbers, so we have Therefore, the method still has test errors in the end, resulting in low accuracy of parameter results.

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