Patent ID: 8358993

Claim:
An image rejection calibration system for a wireless receiver comprising: an RF source for providing an RF calibration signal in the frequency range of said wanted RF input signal; a switching circuit for selectively connecting said RF calibration signal and said wanted RF input signal to quadrature mixers; a quadrature phase adjust circuit responsive to a local oscillator for adjusting the phase of the outputs of said quadrature mixers; a quadrature gain adjust circuit for adjusting the gain of the outputs of said quadrature mixers, said quadrature gain adjust circuit includes a pair of quadrature gain adjust channels, each channel including a variable impedance device and a preamplifier, and a digital to analog converter, responsive to a command from said control circuit, for decreasing the impedance of one variable impedance in one channel and increasing the impedance of the other variable in the other channel; a filter responsive to said gain adjust circuits for passing the wanted RF signals and attenuating image frequencies; a power measurement circuit responsive to said filter for determining the power at the output of said filter; and a control circuit for operating the switching circuit to selectively apply said RF source to said quadrature mixers in calibration mode and is responsive to the output of the power measurement circuit for driving, during calibration mode, the quadrature phase adjust circuit and quadrature gain adjust circuit to adjust the phase and gain, respectively, of the quadrature mixers to reduce the power of the image frequency.