60 GHz broadband image rejection receiver using varactor tuning

A pHEMT broadband image rejection receiver with an image rejection ratio (IRR) more than 20 dB from 54 GHz to 66 GHz is presented using varactor tuning topology. Tunable varactors connected in shunt between an RF coupler and mixers are used to control the phase and amplitude of two RF signals. It offers the IRR improvement of 3.1 ∼ 21.4 dB in the cost of gain degradation below 1.1 dB from 54 GHz to 66 GHz except for 65 GHz. To the best of authors' knowledge, this work shows the best image rejection performance of V-band receivers. At 61 GHz, this circuit achieves an 18.3 dB conversion gain (C.G) and a 49.3 dB IRR. It shows a noise figure of 5.6 ∼ 8.1 dB from 56 GHz to 64 GHz.