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Description:
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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 gm -C 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 . |