A 5.6-GHz CMOS doubly balanced sub-harmonic mixer for direct conversion -zero IF receiver

A new low power 5.6 GHz doubly balanced sub-harmonic mixer for industrial scientific medical (ISM) band direct conversion - zero IF receiver in 0.25-μm CMOS is presented. The mixer uses a power efficient LO frequency generation scheme to overcome the LO self-mixing problems common in conventional direct conversion receivers (DCR). Simulated with 1% gm mismatch, 0.5% load mismatch and 2° LO phase error, the mixer is able to achieve 55 dBm of IIP2, -6.5 dBm of IIP3 and voltage conversion gain of 8 dB while consuming less than 1.75 mA from a single 3 V supply. The mixer also achieves input compression of -12 dBm and an overall double side band noise figure of 5.96 dB. The proposed mixer takes up less than 1 mm² of silicon real estate.