Symbol generator for phase modulated system
First Claim
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1. A filter for filtering digital data, comprising:
- means for receiving a digital data stream containing the digital data;
memory means for storing digital representations of analog waveform segments in predetermined addressable locations, said waveform segments corresponding to the cross-correlation of a predetermined filter function with a predetermined sequence and number of adjacent data bits, there being a plurality of different sequences of adjacent data bits with each predetermined sequence of adjacent data bits corresponding to a unique one of said waveform segments;
address means for examining a frame of adjacent data bits in said data stream, said frame equal in length to said predetermined sequence and number of adjacent data bits, said address means generating an address for addressing one of said waveform segments corresponding to said predetermined number of adjacent data bits in said frame; and
means for assembling said addressed waveform segments into an analog filtered waveform, each of said waveform segments having a duration equal to the duration of each of the data bits in said digital data stream, each increment by one data bit of said data stream providing a new frame for examining by said address means.
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Abstract
A symbol generator is provided for generating a filtered analog waveform for use in phase modulating a carrier. A memory (30) is provided for storing predetermined waveform segments. The waveform segments are correlated with an input data stream. The data stream is converted to an address for the memory (30) to output a digital value to a D/A converter (122). The output of the D/A converter (122) is comprised of in-phase and quadrature-phase components which are input to a sample and hold circuit for generating the analog signals. The waveform segments are then sequentially assembled and input to a vector modulator (168).
205 Citations
21 Claims
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1. A filter for filtering digital data, comprising:
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means for receiving a digital data stream containing the digital data; memory means for storing digital representations of analog waveform segments in predetermined addressable locations, said waveform segments corresponding to the cross-correlation of a predetermined filter function with a predetermined sequence and number of adjacent data bits, there being a plurality of different sequences of adjacent data bits with each predetermined sequence of adjacent data bits corresponding to a unique one of said waveform segments; address means for examining a frame of adjacent data bits in said data stream, said frame equal in length to said predetermined sequence and number of adjacent data bits, said address means generating an address for addressing one of said waveform segments corresponding to said predetermined number of adjacent data bits in said frame; and means for assembling said addressed waveform segments into an analog filtered waveform, each of said waveform segments having a duration equal to the duration of each of the data bits in said digital data stream, each increment by one data bit of said data stream providing a new frame for examining by said address means. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A phase modulation system for phase modulating a carrier with digital data, comprising:
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means for receiving a data stream of the digital data at a predetermined bit rate; memory means for storing digital representations of analog waveform segments at predetermined addressable locations, each of said waveform segments having a beginning point and an end point, each of said waveform segments corresponding to one current bit of data in said data stream with each of said waveform segments comprising the cross-correlation of a predetermined filter function with a predetermined number of data bits about said corresponding current data bit, each combination of said predetermined number of data bits of said one current data bit corresponding to at least one of said waveform segments; address means for examining said predetermined number of data bits about said one current data bit in said data stream and generating an address for addressing the one of said waveform segments corresponding to said one current data bit; means for assembling said addressed waveform segments into an analog filtered waveform such that one of said waveform segments has the end point thereof connected to the beginning point of the next adjacent one of said waveform segments, each of said waveform segments having a duration equal to said corresponding current data bit in said digital data stream; and means for phase modulating a carrier with said analog filtered waveform. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A filter for generating filtered inphase and quadraturephase components for phase modulation of a carrier, comprising:
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means for receiving a stream of data bits at a predetermined data rate; first storage means for storing digitized representations of waveform segments for the inphase components at a predetermined address location; second storage means for storing digitized representations of waveform segments for the quadraturephase components at predetermined address locations therein; said inphase and quadraturephase waveform segments generated by cross-correlating a predetermined filter function with a predetermined number of data bits about a current one of the data bits in said data stream, each of said waveform segments having a beginning point and an end point; said predetermined addressable locations in said first and second storage means corresponding to the one of said data bits addressable by a common memory address; address means for examining said one current bit and said predetermined number of bits about said one current bit to generate said memory address to output the corresponding one of said inphase and quadraturephase waveform segments; means for converting said digitized inphase and quadraturephase waveform segments to an analog format; and means for assembling said converted inphase waveform segments in analog format to provide a filtered inphase waveform and said converted quadraturephase waveform segments in analog format to provide a filtered quadraturephase waveform such that for each assembled waveform, the corresponding ones of said waveform segments are assembled with the end point of one of said waveform segments connected to the beginning point of the next adjacent one of said waveform segments. - View Dependent Claims (18, 19, 20)
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21. A phase modulation system for phase modulating a carrier with digital data, comprising:
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means for receiving a data stream of the digital data at a predetermined bit rate; memory means for storing digital representations of phase segments at predetermined addressable locations, each of said phase segments corresponding to one current bit of data in said data stream with each of said phase segments comprising the cross-correlation of a predetermined filter function with a predetermined number of data bits about each of said corresponding current data bits, each combination of said predetermined number of data bits about said one current data bit corresponding to at least one of said phase segments, each of said phase segments having a beginning phase, an ending phase and a predetermined phase relationship between said beginning and ending phase; address means for examining said predetermined number of data bits about said one current data bit in said data stream and generating an address for addressing the one of said phase segments corresponding to said one current data bit; means for assembling said addressed phase segments into a sequential stream of digital data, the beginning phase in one of said phase segments sequentially following the ending phase in the adjacent one of said phase segments, each of such phase segments having a duration equal to said corresponding current data bits in said digital data stream; and means for phase modulating a carrier with the digital data output by said means for assembling.
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Specification