Digital phase modulator formed with a fixed-point digital signal processor

摘要

Data from an A/D converter is supplied to a fixed-point DSP. The fixed- point DSP adjusts the level of the data x so that computed results do not exceed .+-.1. In succession, for the i-th data x.sub.i, the fixed- point DSP computes cos &pgr;·x.sub.i when i=1, 5, . . . , -sin . pi.. multidot.x.sub.i when i=2, 6, . . . , -cos &pgr;·x. sub.i when i=3, 7, . . . and sin &pgr;·x.sub.i when i=4, 8, . . . and outputs a digital phase modulated signal y(t) by outputting the computed results in order. Trigonometrical functions are computed by expanding them to a series so that the intermediate computed results do not exceed .+-.1.