Method and apparatus for estimating the phase of a signal

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 () 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 (). A quadrant determination block () examines the signs of the signals to determine the quadrant in which the phase of the input signal exists. A comparator block () 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 () to form a multiplied signal, and a counter incremented, initially from zero. The comparator block () then determines if the multiplied signal is greater than or equal to the magnitude of the second signal. This continues until the multiplied signal is equal to or exceeds the magnitude of the second signal. Carried to an upscaling block () is the multiplied signal (or the first signal if there is no multiplied signal), the magnitude of the second signal and the count of the counter (M). The upscaling block () examines the multiplied signal (or the first signal) and determines an upscaling factor. The multiplied signal (or the first signal) is multiplied by the scaling factor, as is the second signal, and the upscaled signals are provided to an angle determination block (). The phase error θin degrees is estimated by the formula θ=45°/2.