APPLICATION OF SIGNAL INTERFERENCE TECHNIQUE TO THE IMPLEMENTATION OF WIDEBAND DIFFERENTIAL FILTERS

This chapter introduces and discusses the basic concept and theories in the signal interference techniques. These techniques are used in the chapter to design microwave filters with different performance requirements by applying different circuit topologies along the two signal paths. A simple circuit model is proposed for wideband differential bandpass filters, and based on this model, several design examples are provided to verify the convenience and efficiency of the circuit model. Marchand balun, π‐type ultra‐wideband (UWB) 180° phase shifter, and double‐sided parallel‐strip line (DSPSL) UWB 180° phase inverter will be applied to create the 180° phase difference in the different signal paths of the circuit model. The chapter further presents a compact wideband differential bandpass filter based on the simple DSPSL UWB 180° phase inverter. Finally, it introduces the mixed‐mode S‐matrix to describe the performance of differential filters.