The C1-C20-XX from RD Microwaves is a Directional Coupler with Frequency 1 to 4 GHz, Coupling 10 to 30 dB, Coupling Variation ±1 to 3 dB, Frequency Sensitivity ±0.5 dB, Directivity 20 to 22 dB. Tags: Module with Connectors. More details for C1-C20-XX can be seen below.