Fully-integrated correlated tuning processor for continuous-time filters

Measurement results on the correlated tuning loop (CTL), a novel tuning loop for continuous-time filters integrated in a 2 μm CMOS process are presented. Measured performance indicates that a second-order bandpass filter at 2.5 MHz and Q-factor of 10 can be tuned with an error in resonance frequency of only 0.2% and a gain error of only 1.1 dB. The prototype circuit, which measures 4.8 mm², has been designed and optimized specifically to tune a second order bandpass filter at 10 MHz. The CTL approach, however, may be applied to any filter structure in which the attenuation specifications can be translated to specifications of real and imaginary parts of transfer functions