Quality factor tuning system.

摘要

Based on the insight that the damping of a tunable filter is both related to its quality factor as to its passband gain, an inventive tuning system is proposed which tunes the quality factor of such a filter to a desired quality factor value by tuning the passband gain of the filter to a desired gain value. Such a tuning system is particularly useful in the field of OTA-C filters and consists of first (P1) and second (P2) tuning paths including such a tunable filter (BIQUAD) and fixed gain amplifiers (B-OTA1, B-OTA2). The gain of the latter amplifiers corresponds to the desired gain values. The tuning system further includes matching means (MM) for equalizing the gains in both tuning paths (P1, P2) by generating a quality factor tuning signal (VTQ) which is applied both to the tunable filter (BIQUAD) and to a replica thereof used as master filter in a data processing path. This matching means (MM) includes current rectifiers (C-REC1, C-REC2) implemented so as to use little hardware. <IMAGE>