In a transmitting unit, an input signal is converted into an I data sequence of an in-phase (I) symbol and a Q data sequence of a quadrature (Q) symbol, a differential encoding is performed for the I and Q data sequences according to a differential binary phase shift keying (DBPSK) modulation to produce...http://www.google.co.uk/patents/US5881099?utm_source=gb-gplus-sharePatent US5881099 - Signal processing circuit for spread spectrum communications
