Automatic Tuning for Linearly Tunable Filters

Automatic Tuning for Linearly Tunable Filters. (May 2004) Sung-Ling Huang, B.S., Tatung Institute of Technology, Taiwan; M.S., Tatung Institute of Technology, Taiwan Chair of Advisory Committee: Dr. Aydin I. Karsilayan A new tuning scheme for linearly tunable high-Q filters is proposed. The tuning method is based on using the phase information for both frequency and Q factor tuning. There is no need to find out the relationship between a filter’s passband magnitude and Q. A gmC biquadratic filter is designed to demonstrate the proposed tuning circuitry. The project includes a phase locked loop (PLL) based frequency tuning loop, reference clock generator, and differential difference amplifier (DDA) for dealing with frequency and Q factor tuning loop and linearly tunable second order gm-C bandpass filter. Simulation results for a 10 MHz prototype filter using AMI 0.5μm process is presented. The chip testing results show that the automatic frequency tuning error is 2.5% for the 10 MHz case.