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 [1]. 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.