Adaptive delay compensation in multi-dithering adaptive control

Recently, a delay-insensitive architecture for gradient descent adaptive control, based on parallel synchronous detection for model-free gradient estimation was presented. The key to delay insensitivity in the gradient estimation is careful selection of the phase of the local oscillator in the mixer of synchronous detection, amounting to a single parameter to be estimated per control channel. In this contribution we present a practical adaptive phase selection algorithm for delay compensation in the adaptive control architecture, and present experimental results from a SiGe BiCMOS implementation of the architecture demonstrating sub-microsecond response time in closed-loop adaptive control.