60 GHz broadband variable gain mixer using positive feedback in 65 nm CMOS

Abstract

A 60 GHz down-conversion mixer for a superheterodyne receiver with an IF frequency of about 12 GHz is reported. On the basis of the double-balanced Gilbert cell, the mixer comprises two series LCR networks to enlarge the IF bandwidth (BW) and a cross-coupled pair used as positive feedback to the raise conversion gain (CG) at the load stage. By adjusting the bias of the cross-coupled pair, the mixer features a variable CG. The mixer core only consumes 2.8 mA from a 1.2 V supply when the cross-coupled pair is turned off, whereas the corresponding a 3 dB IF BW is from 6.5 to 17.5 GHz with a 3 dB CG, which is believed to be the widest IF BW ever reported for a 60 GHz down-conversion mixer with an IF frequency of about 12 GHz. The CG can be enhanced by driving the cross-coupled pair, which consumes another 2.4 mA, i.e. 5.2 mA in all for the mixer core. The CG will reach 7.5 dB and the corresponding 3 dB IF BW is from 8 to 16 GHz, where the CG and BW product against power consumption is also believed one of the best results ever reported for a 60 GHz down-conversion mixer with IF frequency of about 12 GHz.