An Ultra-Wideband, High Power and High Isolation Single-Pole-Double-Throw Switch Using Capacitive Loading Approach

This brief presents an ultra-wideband, series-shunt type single-pole-double-throw (SPDT) switch with high isolation and good power handling capability from DC to 40 GHz. A new topology using capacitive loading on the shunt arms was proposed to improve the isolation across the entire band. The effect of the capacitive loading has been theoretically analyzed. Using the simple SPDT topology with one shunt arm as comparison, the capacitive loading approach exhibited an improvement of 5.9 dB in isolation at 40 GHz. To enhance the power handling capability, the stacked-FET configuration was adopted at the shunt arms. The optimum design has been implemented in the commercially available 0.15- $\mu \text{m}$ GaAs pseudomorphic high-electron-mobility transistor (pHEMT) process and demonstrated an insertion loss of less than 3 dB, an isolation of greater than 39 dB, and an input 1-dB compression point (P textsubscript 1dB) of better than 32 dBm from DC to 40 GHz. To our knowledge, the proposed SPDT switch demonstrates the highest isolation over the widest bandwidth among other reported works to date.