EMC filtering design of biasing circuit for broadband active device

Broadband transceiver circuits are so important for the realization of microwave instruments and radar systems that may have decisive influence on the performance of the whole product. Because of very wide frequency range, transceiver frontend circuits in microwave apparatus covering from DC to microwave band, broadband active devices are widely applied in the circuits. And the leakage of useful signal and noise arising from the improper bias circuit design for these active devices may not only decline the system´s sensitivity, but also even make it unworkable at the worst. At the same time, the reasonable design of bias circuit for these active devices is the very important technique for avoiding electromagnetic interference (EMI) and improving electromagnetic compatibility (EMC). In this paper, the filtering features of capacitor, the traditionally filter component, and EMI filter are discussed and better filter performance can achieved when applying the EMI filter to microwave broadband active devices´ biasing circuits. Cooperate with the resistor, this kind of filter circuit can completely satisfy the bias circuit requirements of active devices for high sensitivity circuit and enhance the system´s electromagnetic compatibility.