Passive devices are an important category of microwave radio frequency devices and occupy a very important position in microwave technology. Passive devices mainly include resistors, capacitors, inductors, converters, faders, matching networks, resonators, filters, mixers and switches. Electronic components that can display their characteristics without the need for an external power supply. Passive components are mainly resistive, inductive and capacitive devices. Their common feature is that they can work when there is a signal without adding power in the circuit. Microwave radio frequency devices are divided into two categories: passive and active. The criterion for distinguishing the two is to see whether the equivalent circuit model established by the device contains a power source (voltage source or current source). power supply, the device is called a passive device.