Modulation method for generating binary or quadrature PSK signals - using filters for respective baseband signal components with shift registers, stepping generators and waveform memories

摘要

The modulation method involves combining I and Q components of a LF signal with a carrier signal to provide binary phase shift keying signals, or quadrature phase shift keying signals. The I and Q components of the digital baseband signal are fed to respective filters (14,15) using shift registers (1a,1b), stepping generators (3a,3b) and signal waveform memories (2a,2b). The filtered signals are fed to a multiplexer (9) via respective switching devices (4a,4b) and inverters (7,8). The multiplexer is coupled to a 2-bit counter, providing a 1 out of 4 selection. The multiplexer output is fed via a D/A converter (10) with an operating clock which is 4 times the frequency of the carrier signal. The output is obtained via a smoothing filter (11) at the output of the D/A converter. USE/ADVANTAGE - For satellite communication signals. Accurate realisation of phase shifts.