High-Performance SLCFETs for Switched Filter Applications

FET-based switched filters do not occupy a large space in the literature due to the high loss of the switches relative to other technologies. The Super-Lattice Castellated Field Effect Transistor (SLCFET) is a low loss, high isolation, broadband RF switch that meets this need. A 4 channel tunable band pass filter employing SLCFET switches in a splitter/combiner network was fabricated in order to demonstrate the enabling capability of the SLCFET for this application. Each filter state employed a novel, high-Q LC circuit. The insertion loss of the MMIC passbands was around -6.5 dB, of which -1.3 dB was attributable to the six Single Pole Double Throw (SPDT) switches in the network. Breakout SPDTs were measured from 0.5 to 25 GHz. Measured insertion loss at 18 GHz was -0.41 ± 0.1 dB and isolation was -28.8 ± 0.1 dB, for 35 SPDTs on the wafer.