Despreading of a CPM (continuous phase modulation) spread-spectrum signal

摘要

A method of despreading a continuous phase modulated spread spectrum signal, the spread spectrum signal generated from a sequence of odd chips and even chips, the method comprising: receiving the spread spectrum signal (401); separating (803) the spread spectrum signal into first (804) and second (805) duplicate signals; demodulating (811) the first signal into a first demodulated signal (812) using a first non-coherent local reference signal (cos omega lt); demodulating (816) the second signal into a second demodulated signal (817) using a second non-coherent local reference signal (sin omega lt), the second non-coherent local reference signal having the same frequency as the first non-coherent local reference signal but phase offset therefrom by 90 degrees; temporarily storing the first demodulated signal in a single first register (821), and temporarily storing the second demodulated signal in a single second register (827); correlating the contents of the first register to generate a first correlation signal (824) and a second correlation signal (826); correlating the contents of the second register to generate a third correlation signal (830) and a fourth correlation signal (832); and combining (839) the first, second, third and fourth correlation signals into a unified correlation signal (842).