11. spread spectrum communications: spread spectrum techniques - DS

11.4.1 direct sequence (DS) modulation

mathematical expression of signal 

• modulating signal,
  
   its complex envelope

DS modulation is usually used with BPSK information signals, which have the complex form,

where

 is a binary-valued data waveform of

• spreading signal,
  
   its complex envelope,
  

• spread spectrum signal, DS/BPSK

DS/BPSK signal is formed by multiplying the BPSK signal by

, resulting in the real transmitted signal

 

DS system block diagram