Intermodulation distortion in a photoconductive microwave switch

Single-tone harmonic and two-tone intermodulation distortion measurements are presented for a photoconductive microwave switch. The switch consists of a lightly doped die of silicon mounted over a gap in a transmission line. The switch is controlled via near infra-red light delivered by a fiber optic cable. Whilst under constant illumination, the third order intercept for a 2 GHz CW signal is extrapolated to be 74 dBm. Under a 1 MHz spaced two-tone signal, the extrapolated intermodulation intercept point is 58 dBm.