A superconducting microwave power limiter for high-performance receiver protection

We report on the development of a microwave power limiter based on high-temperature superconductor technology. The power limiter takes the form of a 50 /spl Omega/ coplanar waveguide transmission line that can be reversibly driven from the low-loss superconducting state into the high-loss normal state as microwave currents within the device exceed a critical value. This device has demonstrated very low insertion loss (<0.5dB/cm at 70K, 40GHz) and extremely wide bandwidth (constant impedance up to 40 GHz) in the signal-pass state, with variable attenuation in the signal-block state. Switching times for transitions from the signal-pass state to the signal-block state are estimated to be on the order of a nanosecond or less. Reversible operation has been demonstrated for continuous-wave (CW) signals up to 10 W at 3GHz, and for 100 /spl mu/s transient signals up to 100W. This device should be valuable for protecting high-performance receiver components from high-power transients encountered in real-world applications.