Pseudo-random sequence based tuning system for continuous-time filters

Continuos-Time filters are widely used in signal processing but require a tuning system to align their frequency response. Several tuning techniques have been proposed in the literature, which can be grouped in two basic schemes: master-slave and self-calibration arrangements. Here we propose a novel tuning approach which can be applied to both tuning schemes. The tuning algorithm is based on the application of a pseudo-random input Test Pattern Signal and on the evaluation of a few samples of the input-output cross-correlation function. The key advantages of the proposed technique are basically the use of a pseudo-random pattern signal which can be generated by a very simple circuit in a small die area and the simple circuitry required to sample the filter output and to perform the cross-correlation operation. Some experimental results of the application of the proposed tuning technique to a benchmark filter are given in order to assess its effectiveness.