Effect of phase mismatch on image rejection in Weaver architecture

Abstract

In a radio frequency receiver, image signals degrade the sensitivity of the receiver for receiving desired signals. This letter analyzes the effect of phase mismatch on image rejection in the Weaver architecture, which has been proposed to reject image signals. Weaver architecture requires the phase difference between the I signal and Q signal of the first and second local oscillators (LOs) to be 90 degrees. However, the realization of accurate 90 degrees phase shifters is very difficult. It is found here that an accurate 90 degrees phase shifter is not essential in Weaver architecture. Instead, by making the phase mismatch between the I and Q signals of the first LO be equal to that of the second LO, image rejection can be performed, being insensitive to the phase mismatch. The reason for this is mathematically analyzed and simulation results are presented.