An Ultra-Wideband Image-Reject Up-Conversion Mixer With a Sandwich-Coupled Transformer for 5G mm-Wave Communication

This letter presents an ultra-wideband 20–42 GHz image-reject up-conversion mixer with low dc-power consumption implemented in 55 nm CMOS technology for multiband mm-Wave 5G systems. A sandwich-coupled transformer (SCT) is adopted to expand the operation bandwidth. The proposed SCT demonstrates good performance in enhancing the coupling coefficient and quality factor, which enables wideband impedance matching. Moreover, a quadrature signal generator composed of a transformer and a polyphase filter (PPF) is utilized to generate wideband high-precision I/Q signals without any calibration. With only 24 mW dc-power consumption, the mixer exhibits excellent conversion gain flatness of 1.2±1.5 dB from 20 to 42 GHz. The measured image reject ratio (IRR) is better than −30 dBc within the entire operation band. The measured output 1-dB compression point (OP _{1 dB} ) is −2.57 dBm at 28 GHz and −3.96 dBm at 38 GHz. The proposed mixer exhibits good broadband characteristics, which can sustain multiband operation.