An efficient architecture for Kalman band-pass sigma-delta (/spl Sigma/-/spl Delta/) demodulator, used in the application of FM demodulation, is presented. The IF stage of the circuit separates the inphase and quadrature (I and Q) signals using a single circuit path, thus eliminating I-Q differences due to component mismatch. The separated I-Q signals are then filtered using an efficient recursive Kalman band-pass filter. The demodulation performance of Kalman filter is evaluated. The FPGA (field programmable gate array) design of the architecture is given.