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Development of Network Analyser Foundation
Network analyzer is a new instrument for measuring network parameters. It can directly measure complex scattering parameters of active or passive, reversible or irreversible dual-port and single-port networks, and give the amplitude and phase frequency characteristics of scattering parameters by sweeping frequency. The automatic network analyzer can correct the measured results point by point and convert dozens of other network parameters, such as input reflection coefficient, output reflection coefficient, voltage standing wave ratio, impedance (or admittance), attenuation (or gain), phase shift and group delay, isolation and orientation.
Network analyzer is developed on the basis of four-port microwave reflectometer (see standing wave and reflection measurement). In the mid-1960s, automation was realized, and the errors caused by imperfect orientation, mismatch and leakage of the directional coupler were corrected at each frequency point by computer according to a certain error model, so that the measurement accuracy was greatly improved, and the measurement accuracy of the most precise measurement line technology in the metering room could be reached, while the measurement speed could be increased. Degree increased by tens of times.
In 1973, a six-port network analyzer was developed. It uses a six-port network consisting of a directional coupler and a hybrid connector (magic T) as the measurement unit. Except for two ports connected to the signal source and the measured component respectively, the other four ports are connected to an amplitude detector or a power meter. The modes and phases of the scattering parameters of the measured network can be obtained by proper combination of the detected four amplitudes. It does not need to use complex dual channel receivers to obtain phase information, thus greatly simplifying the hardware of the measurement system. In addition, it has more than the necessary number of redundant measurement ports, and can use the redundant data to check each other to improve the reliability of measurement results. But its calculation is much more complicated than that of four-port network analyzer. Dual-six-port network analyzer is used to measure dual-port network, that is, one six-port network analyzer is connected to port 1 of the network under test and the other is connected to port 2, which can avoid switching or manual inversion of the input and output terminals of the network under test in the measurement process, thus further improving the accuracy of measurement.