A microwave spread spectrum modem
N.D. Du Toit · 2003
The design of a direct-sequence spread-spectrum modem intended for a mobile microwave communications link is described. Major design issues are signal generation and synchronization. The key features of this design are: (1) coherency among all frequencies: RF carrier, code clock, data bit rate, code repetition frequency and demodulator sample rate; (2) a combined carrier frequency and code phase-lock loop incorporating a single oscillator; and (3) software implementation of the automatic gain control loop filter, carrier frequency-code phase loop filter and an entire Costas loop.>