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Abstract

A sample data position error signal detection means. This invention has application in a digital servo in a magnetic media disk drive environment. In particular, the invention relates to the detection in digital form of position error signals (PES) representative of magnitude and sign of recording head displacement from a track center line. The circuits disclosed provide a digital representation of PES suitable for direct application to a digital signal processor which controls overall servo positioning operations. The invention detects the PES by employing a digital integrator which comprises a register and adder. The composite servo data is first amplified by variable gain amplifier and then undergoes low pass filtering before being digitized by an analog to digital converter (ADC). The digital integration is performed by accumulating a constant number of ADC samples in the register. Before being accumulated in the register, the sampled servo data is alternately multiplied by plus or minus one, using an exclusive-OR gate cascade interposed between the ADC output and adder input. The multiplication of the sampled servo data by plus one or minus one is required for synchronous rectification. Upon completion of accumulation of a prescribed number of ADC samples, the contents of the register are transferred to a temporary buffer pending interrogation by the servo controlled digital signal processor.

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First Claim