Abstract：To reduce the size of the filter integrated switch (FIS), a compact single-pole-double-throw (SPDT) filtering switch based on a tri-mode resonator was proposed in this paper. Compared with the conventional FIS, this design could reduce the number of the multi-mode resonator in the SPDT filtering switch by adopting different resonator modes and coupling paths in one single resonator with a PIN diode, which would greatly decrease the size of the FISSPDT filtering switch. In addition, a PIN diode was introduced at the end of the feeding line to increase the off-state isolation of the SPDT filtering switch. Results show that the centre frequency of the on-state switch is 975 MHz and the 3dB bandwidth is 250 MHz. The on-state insertion loss was better than 2.4dB and the common port return loss is better than 20 dB. The on-state port return loss is better than 15dB and the off-state suppression is better than 23 dB.
