10 GHz dual-conversion low-IF downconverter with microwave and analogue quadrature generators

A 10 GHz dual-conversion low-IF downconverter using 0.18-mum CMOS technology is demonstrated. The high-frequency quadrature RF and LO₁ signals are generated by broadside-coupled quadrature couplers while a two-section polyphase filter is utilised for the low-frequency LO₂ quadrature signal generation. As a result, the demonstrated downconverter achieves a conversion gain of 7 dB, IP_{1 dB} of -16 dBm, IIP₃ of -5 dBm and noise figure of 26 dB at a 1.8 V supply. The image-rejection ratio of the first/second image signal is 33/42 dB for IF frequency ranging from 10 to 60 MHz, respectively.