An auto-calibrating I/Q mismatch scheme for high image rejection GPS RF receiver

An auto-calibrating I/Q mismatch scheme for high image rejection Multi-mode Global Navigation Satellite Systems RF receiver is proposed in this paper. Due to gain and phase errors between I and Q paths, image rejection will be restricted at poor level from the mismatch instead of components themselves in the system. The proposed calibrating scheme included an analog image rejecter and a digital error detector corrects the mismatch to optimize the image rejection performance using bisection adaptive feedback concept. Within 0.5dB gain error and 3 degree phase error, the proposed auto-calibrating scheme followed by a 5^th complex filter can achieve 53.5dB image rejection, compared with 28dB without the scheme. The whole circuit consumes 1.1mA at 1.8V.