Pulse shaping filter for pi /4-shift QPSK modulator

摘要

A pulse shaping filter for the pi /4-shift QPSK modulator employed in IS-54 and JDC. The pulse shaping filter includes symbol determining circuits of the I-channel and the Q-channel, demultiplexers for inverse multiplexing each of the input signal value from the symbol determining circuits, a plurality of shift registers for shifting data from each of the demultiplexers according to odd and even symbol clock, a multiplexer for multiplexing each data from the shift registers to produce the corresponding address values, a plurality of ROM tables for storing the multiplexed address value, and a multiplexing and adding unit for multiplexing the address value stored in the ROM tables and adding the resulting multiplexed value.