The vector network analyzer comes with a signal generator that can frequency scan a frequency band. If it is a single-port measurement, add the excitation signal to the port and measure the amplitude and phase of the reflected signal. Determine the impedance or reflection. For dual-port measurement, you can also measure the transmission parameters. Because it is obviously affected by distribution parameters, etc., the network analyzer must be calibrated before use.
In the design and calculation of microwave circuits, it is necessary to comprehensively set all network parameters of the components and device characteristics used. Most microwave components and devices, including microwave transistors, use S parameters (scattering parameters) to describe their characteristics. Generally, a two-port network requires four scattering parameters (S11, S22, S12 and S21) to fully set its value. Therefore, measurement methods are often used to determine network parameters.
In the mid-1960s, a multi-functional instrument emerged that could perform sweep measurements within a wide frequency band and display the modulus and amplitude of all network S parameters. This was the microwave network analyzer. So the basic part of a network analyzer is actually an S-parameter meter. The block diagram is shown in Figure 2.
Since the S parameters of the network are measured, various other characteristic parameters of the network can be derived from the S parameters. Therefore, the microwave network analyzer has multiple functions.