Reflection mode notch filter

摘要

A two stage transmission notch filter characteristic is achieved with one stage of microwave circuitry. Elimination of the second stage is accomplished by reflecting the microwave power back through a single stage device. Structurally, the adjacent ports of two 3 dB directional couplers are directly connected by delay lines of unequal delay times. The opposite adjacent ports of one coupler comprise the device input and output while the opposite adjacent ports of the other coupler are terminated in a manner that reflects microwave power back through the device. A phase shifter is inserted into one delay line for tuning and a non-reciprocal phase element is used to prevent reflected signals from emerging from the input port.