Microwave active notch filter and operating method with photonic bandgap crystal feedback loop

摘要

An active notch filter and a method of filtering an electrical microwave input signal are disclosed. The filter comprises an amplifier (30) with an input (32) and an output (34), and a feedback loop between the output (34) and the input (32). The feedback loop generates a feedback signal and comprises an element having at least one frequency bandgap within which it substantially attenuates the transmission of electromagnetic radiation. The element, preferably, is a photonic bandgap crystal (PBC) (40). The feedback loop causes the amplifier (30) to impart a greater amplification to signals within the bandgap than signals outside of the bandgap. The element generates the feedback signal by transducing a signal at the output (34) into electromagnetic radiation, filters the radiation to attenuate a selected frequency band, and transduces the filtered radiation back into the feedback signal.