UWB AND NOTCHED‐BAND UWB DIFFERENTIAL FILTERS USING MULTILAYER AND DEFECTED GROUND STRUCTURES (DGSs)

The development of ultra‐wideband (UWB) differential filters is an attractive topic in microwave circuit research because of the capacity of these filters for high data rate transmission, high immunity to environmental noise, and low electromagnetic interference (EMI). The mechanism of the multilayer microstrip‐to‐slotline transition (MST) and its applications in differential topology are analyzed, with the slotline defected ground structure (DGS) pattern etched in the ground. This chapter presents several typical types of UWB and notched‐band UWB differential filters based on the MST. It describes UWB differential filters based on the MST with a notched band and enhanced stopband. To achieve UWB differential filters based on the MST, many investigators have presented a variety of designs with satisfactory performance. In the chapter, the strip‐loaded slotline resonator is introduced and applied to differential filters with multimode operation. The employment of back‐to‐back microstrip resonators enables easy control of the resonant modes for constructing wideband differential filters.