Digital phase and amplitude modulator

A digital modulator for modulating a stream of incoming data bits in which a predetermined number of successively incoming ones of such bits, constituting a set, correspond to a symbol, comprising:

• (a) means for temporarily storing, in parallel, incoming symbol data bits of "n" successive symbols where "n" is a positive integer with a value greater than or equal to 1, with the oldest stored symbol bits being discarded upon the arrival and storage of a next set of symbol bits;
• (b) memory means for storing sample values corresponding to a modulated symbol impulse response for each of a predetermined number of symbols wherein the modulated symbol impulse responses each extend over "n" symbol periods;
• (c) means for retrieving, in sequence, sample values from said memory means corresponding to symbols stored in said storing means in pre-selected time intervals over a symbol period for overlapping portions of each of the modulated symbol impulse responses corresponding to the symbols stored in said storing means;
• (d) an adder coupled to said retrieving means and operative to sum the retrieved sample values which correspond to each other in time;
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• (e) a digital to analog converter coupled to an output of said summing means and operative to convert each sum of sample values for each symbol period to an analog signal for subsequent transmission.

A digital modulator for modulating a stream of incoming data bits in which a predetermined number of successively incoming ones of such bits correspond to a symbol, comprising:

• (a) a symbol formatter having an input coupled to said stream of incoming data bits, said formatter operative to arrange incoming symbol bits for each symbol in parallel;
• (b) a shift register coupled to an output of said symbol formatter having "n" stages for storing in parallel incoming symbol bits of "n" successive symbols where "n" is a positive integer with a value greater than or equal to 1, with the oldest set of stored symbol bits being discarded upon the arrival and storage of a next set of incoming symbol bits;
• (c) digital semiconductor memory for storing sample values corresponding to a modulated truncated symbol impulse response for each of a predetermined number of symbols wherein the modulated truncated symbol impulse responses each extend over "n" symbol periods;
• (d) means for retrieving in sequence sample values from said memory corresponding to a given interval of time equal to a symbol period for overlapping portions of each of the modulated truncated symbol impulse responses stored in said storing means;
• (e) an adder having an input coupled to said memory for summing corresponding sample values received from said memory and operative to add sample values which correspond in time for overlapping portions of each of the modulated truncated symbol impulse responses stored in said memory and corresponding to the symbols stored in said storing means sequentially in predetermined time intervals over a symbol period;
• and
• (f) a digital to analog converter means for converting each sum of sample values for each symbol period to an analog signal for subsequent transmission.