DIGITAL QUADRATURE MODULATOR AND DIGITAL QUADRATURE DEMODULATOR

摘要

PROBLEM TO BE SOLVED: To provide the circuit configuration not requiring an arithmetic circuit executing multiplication of exp(jωst) required for digital quadrature modulation/ demodulation. SOLUTION: A 2K-th tap of a roll off filter coefficient of a (4N-1)-tap designed on the basis of 4fs is assigned to an acyclic digital filter 3 and a (2K+1)-th tap is assigned to an acyclic digital filter 4 and a sign of the tap coefficients of the digital filters 3, 4 is inverted at an interval of one. A multiplexer circuit applies time division multiplex to outputs of the digital filters 3, 4 alternately to provide an output of the result. Thus, the arithmetic operation of convolution of the digital filters is executed simultaneously at the arithmetic operation for modulation and demodulation.