Adaptive cancellations of systematic disturbances in a synchronous amplitude demodulator for sensors and instrumentation applications

An adaptive technique is presented that performs synchronous amplitude demodulation while adaptively canceling systematic disturbances—frequently encountered in sensors and instrumentation applications. The method is effective in jointly estimating and tracking the signal amplitude along with additive DC bias, interfering sinusoids, or exponentially decaying transients. Lyapunov method is used to study the stability and convergence of the proposed technique. In addition, the extension of the algorithm for multiple sinusoid case is also presented. Computer simulations and the experimental results are included to demonstrate the effectiveness and applicability of the proposed scheme in applications like resolver, synchros, and power system relays. It can easily be implemented in cost effective manner requiring minimal computation effort and hardware.