Phase jitter compensation arrangement using an adaptive IIR filter

A voice-band data symbol is typically impaired by so-called phase jitter prior to the symbol being received at a data modem. Modem circuitry estimates the phase angle of the jitter and an infinite-impulse-response (IIR) filter adjusts to that phase angle so that the jitter can be corrected for by a demodulator circuit. Advantageously, the IIR filter is arranged so that its pair of complex, conjugate poles are initially positioned at a first predetermined radius within a unit circle. The angular displacement of the poles around the unit circle is adaptively increased in response to receipt of a series of such estimates until such displacement substantially equals the phase angle of the jitter. The poles are then positioned at a second predetermined radius to increase the gain of the filter.