Dielectric filtering switch based on switchable bridge-type coupling structures

As one of the important components in the time division duplex (TDD) subsystem of wireless communications, filtering switch, which integrates two functions of filter and switch, has been widely concerned and studied. At present, most of the reported filtering switches are realized by microstrip lines. However, the loss of microstrip filtering switch cannot meet the requirements of the communication systems. A switchable bridge-type coupling structures for dielectric filters is presented in this paper. The coupling structure is constructed by a section of metal strip on the printed circuit board (PCB) and two metal probes inserted in the adjacent dielectric cavities. Shunt PIN diodes are loaded at the metal strips so that the coupling path can be switched on or off by controlling the bias conditions of the PIN diodes. For demonstration, a fourth-order dielectric filtering switch is implemented and measured for 5G applications. It features an on-state low loss of 1.2 dB and an off-state isolation of 50 dB in measurement. The proposed design features lower insertion loss and higher isolation as compared with the traditional microstrip filtering switches.