This paper describes the Customizable Coherent Demodulation Algorithm, a servo demodulator which provides dramatically improved performance over the currently used servo demodulation methods for disk drives. The demodulation algorithm proposed here makes better use of knowledge about the readback signal coming from the disk to provide better noise immunity and more immunity to other nonidealities in the magnetic head response. The net result is a demodulated Position Error Signal (PES) which has a much cleaner response.