High isolation MMIC switch design technique based on novel high-/low-pass switch concept

This paper describes the proposal of novel high-/low-pass RF switch concept. This proposed RF switch concept is completely different from the conventional switch circuits because the broadband perfect reflection occurs in the off-state, which is essential to achieve broadband high isolation characteristics. By changing the gate bias of FETs between two states of high and low voltages, two functions can be switched between high-pass filter and low-pass filter. By utilizing the stopband of high-pass filter below its cut-off frequency, extremely high isolation can be achieved. And also, broadband low insertion loss can be obtained by using the passband below its cut-off frequency of low-pass filter. High isolation of more than 79 dB SPST MMIC switch with less than 1.6 dB insertion loss have been successfully demonstrated below 6 GHz by using this novel switch concept with small chip size of 1.1 mm × 1.0 mm.