Patent ID: 7860196

Claim:
A circuit comprising: an antenna for receiving a carrier signal modulated by a data signal; a direct conversion receiver for receiving the modulated carrier signal, the direct conversion receiver including a mixing module having an in-phase and a quadrature phase signal path arranged to mix a mixing signal at different phases with the received modulated carrier signal in order to generate an in-phase and a quadrature baseband signal; a signal generator circuit arranged to generate the mixing signal having a frequency substantially the same as the carrier signal; a frequency offset circuit arranged to generate an offset signal having a frequency offset from the frequency of the carrier signal; and a coupling circuit 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, wherein the signal generator circuit comprises a first frequency divider coupled to an oscillator the frequency offset circuit comprises a programmable frequency divider coupled to the oscillator, the programmable frequency divider having a division ratio offset from the division ratio of the first frequency divider in order to generate the offset signal, and at least one of: wherein the first frequency divider provides the mixing signal to a feedforward path of the direct conversion receiver but does not provide the mixing signal to a feedback path of the direct conversion receiver and the programmable frequency divider provides the offset signal to the feedback path but does not provide the offset signal to the feedforward path, or the frequency offset circuit further comprises a summer, the summer having an input set at a predetermined value and a smaller variable value, the division ratio of the programmable frequency divider being set by the sum of the predetermined value and the smaller variable value.