A technique for offset and gain mismatch cancellation in quadrature A/D converters

In this paper we present a new technique for cancelling offset and gain mismatches in dual-channel (quadrature) A/D converters. The proposed technique, based on two A/D converters with pseudo-random swapper cells at the input and at the output, allows the tones, due to offset and gain mismatches between the two channel, to be spread over the whole signal bandwidth, thus maintaining the signal-to-noise ratio unchanged, while strongly improving the spurious-free dynamic range. In addition, we present a technique, also based on pseudo-random signal swapping, for reducing the offset power and hence improving the signal-to-noise ratio as well. This technique results beneficial also for reducing the harmonic distortion. The proposed techniques are analyzed theoretically and verified with behavioral simulations.