Method and circuit for estimating in-phase/quadrature signal amplitude imbalance

Abstract

A circuit (100) comprising an antenna (105) for receiving a carrier signal modulated by a data signal, a direct conversion receiver (180) for receiving the modulated carrier signal, a signal generator circuit (140, 145, 150) arranged to generate a mixing signal having a frequency substantially the same as the carrier signal, a mixing module (125i, 125q) having an in-phase and a quadrature phase signal path (120i, 120q) arranged to mix the mixing signal at different phases with the received modulated carrier signal in order to generate an in-phase and a quadrature baseband signal, a frequency offset circuit (155, 200) arranged to generate an offset signal having a frequency offset from the frequency of the carrier signal, a coupling circuit (170a, 170b, 170c) arranged to selectively decouple the antenna from the direct conversion receiver and to couple the offset signal to the mixing module in order to generate a baseband test signal in the in-phase and quadrature signal paths for determining an imbalance in the amplitudes of the baseband test signals between the in-phase and quadrature signal paths.

Dependencies are inferred from the claim text.