Abstract: This paper reports a capacitive switch with a high capacitance ratio.In contrast to conventional capacitive switches,the switch designed here has a metal film covering the dielectric on the signal line to ensure intimate contact with the dielectric film in the down state.The metal film can constitute two series capacitances versus the bridge and the signal line,so the up-capacitance can be lowered significantly.This allows further optimization of the down/up capacitance,with values more than 1000 over conventional designs under the same conditions.The switch designed here shows better isolation performance than conventional capacitive switches,with an isolation of 42dB at 8GHz.

Key words: capacitive RF-MEMS switches, capacitance ratio, isolation, insertion loss