This paper investigates and resolves in-phase/quadrature phasen(I/Q) imbalances between the input paths of quadrature IF receivers.nThese mismatches along the paths result in the image interferencenaliasing into the desired signal band, thus reducing the dynamic rangenand degrading the performance of the receivers. I/Q errors occur becausenof gain and phase imbalances between quadrature mixers. They are alsoncaused by capacitor mismatches in analog-to-digital converters (A/Ds),nwhich are designed to be identical for each input path. This papernpresents a novel and feasible digital signal processing (DSP) solutionnfor the I/Q mismatch problems. The system includes a novel complex leastnmean square algorithm and a modified adaptive noise canceler (signalnseparator) to separate the desired signal and the image noise caused bynthe mismatch. The noise canceler can also solve the signal leakagenproblem, which is that the noise reference includes signal components.nThis system was implemented in a Xilinx FPGA and an Analog Devices DSPnchip. It was tested with a complex intermediate frequency receiver,nwhich includes an analog front end and a complex sigma-delta modulator.nBoth simulation results and test results show a dramatic attenuation ofnthe image noise. Extending applications of the system to N-path systemsnfurther indicates the robustness and feasibility of this novel adaptivenmismatch cancellation system
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