Radio frequency circuit is a circuit used to process signals, and its operating frequency is usually within the radio frequency band, that is, between a few hundred kilohertz (kHz) and several gigahertz (GHz). Radio frequency circuits are mainly used in various communications, radar, radio, satellite and navigation systems and other fields. The main feature of radio frequency circuits is that the electromagnetic wavelength of the signal they process is of the same order of magnitude as the size of the circuit or device. At this time, the circuit needs to be processed using the relevant theory of distributed parameters.