VALIDITY DECISION CIRCUIT CAPABLE OF CORRECTLY DECIDING VALIDITY OF AN ERROR SIGNAL IN A MULTILEVEL QUADRATURE AMPLITUDE DEMODULATOR

摘要

Abstract of the Disclosure:In a demodulator for demodulating a multilevelquadrature amplitude modulated signal specified by aplurality of output signal points arranged on anapproximately octangular specific region into anin-phase baseband signal and a quadrature basebandsignal and for converting the in-phase and thequadrature baseband signals into a demodulator outputsignal and an error signal, a validity decision circuit(40) is supplied with the in-phase and the quadraturebaseband signals to decide that the error signal isvalid when at least one reception signal point isoutwardly of the approximately octangular specificregion.