PHASE NOISE AND ADDITIVE NOISE ESTIMATION IN A QAM DEMODULATOR

摘要

A QAM demodulator having a carrier recovery circuit (50) that includes a phaseestimation circuit (506) and an additive noise estimation circuit (507) whichproduces an estimation of the residual phase noise (518) and additive noise(519) viewed by the QAM demodulator. The phase noise estimation (518) is basedon the least mean square error (512) between the QAM symbol (509) decided by asymbol decision circuit (508) and the received QAM symbol (504). The additivenoise estimation is based on the same error as in the phase noise estimation(518), except that it is based only on QAM symbols having the minimumamplitude on the I and Q coordinates. The additive noise estimation (519) isnot dependent on the phase of the signal, thus, is independent of the phasenoise estimator.