A 2-V 1.9-GHz Si down-conversion mixer with an LC phase shifter

This paper describes a 2.0-V 1.9-GHz silicon down-conversion mixer with an LC phase shifter in a 20-GHz bipolar process. In this circuit, the lower emitter-coupled pair in a Gilbert cell mixer is removed to enable low voltage operation, and instead an LC phase shifter is inserted between two current sources. The time constant of the LC phase shifter has to be optimized, because the phase shifter acts as a low-pass filter and the lower cutoff frequency results in the loss of signal power. By this optimization, it can keep both high conversion gain and low distortion. The experimental results show conversion gain of 7.0 dB and the input third-order intercept point of -1.0 dBm are realized at 2.0 V.