Abstract: An input signal is a complex vector whose phase is a coherent measurement of the phase rotation occurring between two separated symbols of a received CDMA signal. A processing block (30) provides a first signal showing the magnitude and the sign of the imaginary part of the input signal, and a second signal showing the magnitude and sign of the real part of the input signal to an initialisation block (31). A quadrant determination block (32) examines the signs of the signals to determine the quadrant in which the phase of the input signal exists. A comparator block (33) determines if the magnitude of the first signal is greater than or equal to the magnitude of the second signal. If a negative determination is made, the magnitude of the first signal is doubled in a multiplication block (35) to form a multiplied signal, and a counter incremented, initially from zero. The comparator block (33) then determines if the multiplied signal is greater than or equal to the magnitude of the second signal.