Patent ID: 7489660

Claim:
A system for preventing signal quality degradation in a CDMA system, comprising: a phase locking circuit which controls a phase of oscillating frequency signal; a mixer which mixes the oscillating frequency signal and a radio frequency signal received through an antenna; a demodulator which demodulates a signal output from the mixer; a signal detector which detects a demodulated signal output from the demodulator; a processor which calculates at least one of a constellation pattern and an error vector of the demodulated signal detected by the detector and compares at least one of the constellation pattern or the error vector to one or more corresponding reference signals; and a controller which controls at least one of the phase locking circuit, mixer, or demodulator in accordance with a comparison result of the comparison so as to make the constellation pattern or error vector fall within predetermined ranges based on said one or more corresponding reference signals, wherein the controller controls at least one of the phase locking circuit, mixer, or demodulator to adjust a radius and phase of the constellation pattern to cause the constellation pattern to fall within a first predetermined range or to adjust a magnitude and phase of the error vector to cause the error vector to fall within a second predetermined range, and wherein at least the radius of the constellation pattern is increased to exceed the first predetermined range or at least the magnitude of the error vector is increased to exceed the second predetermined range as a result of distortion affecting the received radio frequency signal, and wherein the radius of the constellation pattern or the magnitude of the error vector is reduced by the controller to substantially coincide with a reference signal position, the radius or magnitude reduced to offset the increase in the radius or magnitude caused by the distortion affecting the received radio frequency signal.