High-speed continuous-time analog complex graphic equalizer for magnetic recording read channels

A high-speed continuous-time CMOS analog adaptive equalizer for use in magnetic recording read channels is presented. The equalizer is implemented as the summation of several bandpass filters covering different frequency bands as in a graphic equalizer. The outputs from each filter are weighted by a complex coefficient and summed, which results in a linear combiner structure guaranteed to converge under LMS adaptation. System-level simulations of our “Complex Graphic Equalizer (CGE)´ shows that its performance is comparable to or better than that of a 10-tap FIR equalizer using two different sequence detectors-PRML and FDTS/DF. A five-band CGE has been fabricated using an 0.8 μ CMOS technology. The highest band of the fabricated CGE was centered at 80 MHz (corresponding to about 200 Msamples/sec). Measured dynamic range was 68 dB and measured THD was less than -70 dB while consuming 97 mW at 3.3 V