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

A 10 GHz dual-conversion low-IF downconverter using 0.18-µm 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, IP1 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.

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