2-14GHz Quadrature Hybrid Coupler for Broadband Cryogenic Receiver

A quadrature hybrid coupler with both ultra-wideband and good cryogenic performance is presented. Based on classic wideband coupler theory, the hybrid is designed to have five symmetrical coupled line sections in order to operating from 2 to 14GHz. An offset broadside coupled stripline structure is used for coupler implementation. Three low loss and thermally stable substrates are used to construct the thin copper films. The measured results show that the hybrid has 0.8 dB amplitude imbalance and 90±3.5° phase difference across the designate frequency band at 24K.