| 摘要 |
PURPOSE:To obtain an amplitude modulator which does not require multiplication, by performing amplitude modulation in a phase area. CONSTITUTION:A modulated signal Rm(T) is converted by an A/D converter 70 into a digital signal, which is inputted to an ROM60. The ROM60 outputs a signal X(T) corresponding to X(T)=cos<-1>[0.5(1+MRm(T)]to a polarity generator 50. In this case, M is a modulation index. Further, a rectangular wave having +1 positive amplitude and -1 negative amplitude is supplied to the polarity generator 50, which outputs a signal S(T)X(T) obtained by inverting the polarity of the signal X(TR) alternately by the rectangular wave S(TR). The output omegacT of a phase accumulator 2 and the output S(TR)X(T) of the polarity generator 50 are summed up by an adder 30, whose output cT+S(TR)X(T) is inputted to an ROM100. The ROM100 outputs sin[omegacT+S(T)X(T)], and a low-pass filter 120 outputs amplitude-modulated components of sin(omegacT)cos[X(T)]=sin(omegacT) [1+MRm(T)]selectively from the output of the ROM100. |
