Tune-All RF Planar Duplexers with Intrinsically Switched Channels

A class of frequency-agile planar duplexers with independently controllable channels in terms of center frequency, passband-width, out-of-band power-attenuation characteristics, and tune-all transfer-function capabilities is reported. Each channel filter is made up of frequency-reconfigurable resonators that are coupled to its direct input-to-output electrical path through static impedance inverters and generate power transmission zeros (TZs). Thus, the duplexer channels are exclusively reconfigured by means of dynamic TZ allocation. Furthermore, the channel filters can be intrinsically switched-OFF by incorporating a bandstop-filtering function into them. The operational principles of this spectrally adaptive duplexer concept are expounded and experimentally demonstrated through the manufacturing and characterization of a microstrip prototype in the UHF range.