408 by a polyphase filter having a response which is matched to that of the transmit chip pulse shape the polyphase filter also serves to correct any timing phase misalignment between the received signal and the locally generated pn sequence the filtered signal is then despread by early punctual and late despreaders matched filtered and decimated to the symbol rate the output of the downconverter despreader ic 408 is a set of complex digital data symbols decimated to the symbol rate the resulting in phase and quadrature i and q symbols for all three channels are sent to a standard digital signal processor dsp ic 414 the dsp ic 414 performs coherent carrier frequency and phase tracking and mpsk demodulation on the punctual channel the i and q early and late symbols are processed by dsp ic 414 to obtain a sample timing phase control signal 418 the dsp ic 414 also serves as a controller for the downconverter despreader ic 408 although a dsp ic 414 is assumed here there is no technical reason why the functions of the dsp ic 414 could not also be incorporated into either the same custom digital ic as the downconverter despreader 408 or implemented in another custom digital ic however the dsp ic 414 provides considerable flexibility in implementing various digital acquisition and tracking algorithms the digital downconverter despreader concept is illustrated in fig5 a and 5 b the technique is best illustrated by an example assume the spread spectrum signal 416 has a chip rate r c of 8 mhz and is filtered in the transmitter with a 30 rolloff square root raised cosine filter thus the transmit signal two sided bandwidth is 10 4 mhz rf stage 401 will be designed for an.