NARROWBAND COUPLED-RESONATOR BALANCED BANDPASS FILTERS AND DIPLEXERS

Narrowband bandpass filters (BPFs) are key components in modern communication systems and other applications of wireless technologies. This chapter discusses balanced filter topologies where common‐mode (CM) is inherently rejected due to the geometric properties (including symmetry) of the proposed structures. It also discusses several examples of this kind of narrowband filter implementation strategy. Diplexers are also important components in modern dual‐band wireless communication systems. The chapter presents a brief discussion on some balanced diplexers made in microstrip technology. Balanced diplexers can be roughly classified into two categories: balun diplexers; and non‐balun diplexers. Balun diplexers are composed of a single‐ended input (output) and two balanced outputs (or a balanced input). On the other hand, a non‐balun diplexer is a genuine balanced diplexer in the sense that both input and output ports are balanced ports.