Simultaneous tuning and signal processing in integrated continuous-time filters: the correlated turning loop

A new tuning loop configuration for integrated continuous-time filters, the correlated tuning loop (CTL), is presented. This configuration derives tuning signals by calculating autocorrelation and cross-correlation functions of the filter input and output signals. The CTL provides a major improvement over other onchip filter tuning schemes: it allows simultaneous signal processing within, and tuning of, a given filter. Analytical expressions for the tuning voltages are given. Simulated results show that the resonance frequency of a second-order bandpass filter can be tuned to its ideal value, even when the input signal consists of broadband noise