Compact Planar Microwave Blocking Filters

Innovators at NASA's Goddard Space Flight Center have designed, fabricated, and characterized absorptive thermal blocking filters for cryogenic microwave applications. The device allows direct integration of the high-frequency signal and microwave readout, and mitigates spurious resonances in the circuit response. This leads to improved electrical performance and a reduction in the required circuit area. The transmission line filter's input characteristic impedance is designed to match 50 ohms and its response has been validated from 0 to 50 GHz. The observed return loss in the 0 to 20 GHz design band is greater than 20 dB and shows graceful degradation with frequency. The filter's response is calculable, repeatable under cryogenic cycling, and is capable of providing an intrinsically broadband matched impedance termination.