A digital scheme for automatic tuning of continuous-time high-filters is proposed. The tuning scheme uses the phase information for both frequency and-factor tuning, therefore, the relationship between the filter's passband magnitude and is immaterial. Due to the digital control of the tuning loops, only one loop is active at a given time interval, which eliminates the need for a slow tuning loop, improves stability and reduces tuning time. Experimental breadboard tests verify the operation where approximately 1% tuning error is accomplished using the offline tuning algorithm.

A digital automatic tuning technique for high-order continuous-time filters is proposed. Direct tuning of overall response is achieved without separating individual biquad sections, eliminating switches and their parasitics. Output phase of each biquad section is tuned to known references, which are generated by a frequency synthesizer. The core tuning circuit consists of D flip-flops (DFF) and simple logic gates. DFFs are utilized to perform binary phase detection. Frequency and quality factor tuning loops for each biquad are controlled digitally, providing more stable tuning by activating only one loop at a given time. The tuning system was verified by a prototype sixth-order bandpass filter which was fabricated in a conventional 0.5 m CMOS process with 1.5 V power supply.

No abstract

No abstract