Asynchronous position error signal detector employing weighted accumulation for use in servo system

A servo system accurately detects and processes signals from servo patterns encoded on magnetic storage disks using weighted accumulation, for use in precisely positioning read/write heads with respect to tracks of data contained on the disks. After servo patterns are sensed by reading them from a disk, the resultant servo signals are processed by weighted accumulation circuitry to provide a position signal, which may be decoded to ascertain the positioning error of the read/write head and to apply any corrections that might be needed. In one embodiment, an amplitude position signal is generated by multiplying the servo signal by complementary quadrature weighting signals, then squaring each quadrature output signal, summing them, and taking the square root of the summed signal. In another embodiment, a phase position signal is generated by multiplying the servo signal by complementary quadrature weighting signals, dividing one of the multiplied signals by the other to provide a quotient signal, and then generating a signal corresponding to the arctangent of the quotient signal. The invention may be implemented with analog or digital circuitry. In an analog embodiment, the quadrature output signals are created using multipliers to multiply the servo signal by complementary analog quadrature weighting signals. In a digital embodiment, the output quadrature signals are created using latches to sample the servo signal at predetermined intervals, selectively multiplying sampled signals by predetermined quadrature weighting signals, and accumulating the resulting signals.