QPSK MODULATOR

摘要

PURPOSE: A QPSK modulator is provided to speed up the modulator by improving a filter of limiting a band width of a carrier, introducing the Zero-IF mode, and removing a multiplier. CONSTITUTION: A first pulse shaping filter(PSF) limits the band of the I-channel signal to an allocated band width. A second pulse sharing filter(PSF) limits the band of the Q-channel signal to an allocated band width. A first multiplier multiplies the output of the first PSF by using the Zero-IF mode. A second multiplier multiplies the output of the second PSF using the zero-IF mode. An adder adds the outputs of the first multiplier and the second multiplier. The PSFs include a level converter for converting the I-channel signal or the Q-channel signal to '01' and '11'.