Digital Recursive Demodulator Based on Kalman Filter

The number of samples used for demodulation determines the demodulation speed of a digital demodulator. The traditional digital quadrature demodulator requires samples covering integer signal periods for demodulation. To improve the demodulation speed and flexibility, a digital recursive demodulator based on the Kalman-filter algorithm is proposed, which can implement demodulation with samples of less than one signal period. Then, the resources consumption and time cost of the Kalman-filter-based demodulator, the widely used digital quadrature demodulator and two other digital recursive demodulators are analyzed and compared. Numerical calculations were carried out to study the measurement uncertainty and the influence of the number of samples on the signal-to-noise ratio of the demodulation result. Finally, the proposed demodulator is applied for capacitance measurement in the industrial application. Experimental results are presented to demonstrate the performance and validity of the proposed demodulator.