Miniaturized, Ultra-Wideband and High Isolation Single Pole Double Throw Switch by Using π-Type Topology in GaAs pHEMT Technology

In this brief, a compact ultra-wideband monolithic microwave integrated circuit single pole double throw (SPDT) switch with high isolation level and low insertion loss is presented. A π-type topology, consisted of a transmission line with an electrical length of less than 90° and two parallel grounded metal-insulator-metal capacitors, is employed to replace the conventional λ/4 transmission line between the adjacent parallel field effect transistors of the serial parallel SPDT switch. In comparison with the traditional method, an ultra-wideband high isolation behavior and the reduced dimension is achieved simultaneously with the proposed SPDT switch. Furthermore, the equivalent circuit model is built to interpret the mechanism of the improved technique. A chip sample is fabricated with Gallium Arsenide processing with a size of 1.25 × 1.05 mm ² . The measured insertion loss is less than 1.9 dB and the isolation is better than 36 dB from DC to 30 GHz. Good agreements are observed between the simulated and measured results.