Differential/coherent digital demodulator operating at multiple symbol points
First Claim
1. A coherent digital demodulator for recovering data conveyed by an incoming signal in a stream of symbols, said demodulator comprising:
- a phase angle generator configured to generate a phase value for each symbol, said phase value defining a phase relationship between in-phase and quadrature components of said incoming signal;
a phase error compensator for generating an adjusted phase angle for each symbol, said phase error compensator having a first input coupled to said phase angle generator, a second input, and an output; and
an integrator, having an input coupled to said phase error compensator output and having an output coupled to said second input of said phase error compensator, for forming a carrier phase tracking loop.
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Accused Products
Abstract
Symbols (18) of a burst (12) are sub-divided into symbol sections (20). Each symbol section (20) is sampled and converted into polar coordinates. A buffer bank (38) selectably delays the samples and replays a preamble (14). A demod bank (40) includes a coherent demod (58) and several differential demods (60). Each differential demod (60) processes its own stream of symbol sections (20). The differential demods (60) feed a preamble detector (66) and a symbol synchronization circuit (62). The symbol synchronization circuit (62) identifies the symbol section (20) which yields the smallest magnitude of frequency errors. This symbol section (20) is processed by the coherent demod (58) to acquire carrier phase and recover data. The coherent demod (58) is implemented in the phase domain so that only oscillation signal phase data need be generated in phase locked loops. Two phase locked loops (110, 112) operate in parallel but with initial reference phase offsets so that at least one of the two loops will not experience hang-up.
92 Citations
36 Claims
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1. A coherent digital demodulator for recovering data conveyed by an incoming signal in a stream of symbols, said demodulator comprising:
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a phase angle generator configured to generate a phase value for each symbol, said phase value defining a phase relationship between in-phase and quadrature components of said incoming signal; a phase error compensator for generating an adjusted phase angle for each symbol, said phase error compensator having a first input coupled to said phase angle generator, a second input, and an output; and an integrator, having an input coupled to said phase error compensator output and having an output coupled to said second input of said phase error compensator, for forming a carrier phase tracking loop. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A coherent digital demodulator for rapidly acquiring carrier phase synchronization comprising:
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a first phase error compensator having a first input adapted to receive an incoming signal, having a second input, and having an output; a second phase error compensator having a first input adapted to receive said incoming signal, having a second input, and having an output; a first phase error detector having an input coupled to said first phase error compensator output and having an output coupled to said second input of said first phase error compensator; a second phase error detector having an input coupled to said second phase error compensator output and having an output; and a phase error offset generator having an input coupled to said second phase error detector output and having an output coupled to said second input of said second phase error compensator. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A demodulator for demodulating a burst communication signal having a preamble portion followed by conveyed data, said demodulator comprising:
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a digitizer for characterizing a parameter of said communication signal which is manipulated to convey data, said digitizer having an output; a delay circuit having an input coupled to said digitizer output and having an output; a preamble detector coupled to said digitizer output; and a symbol synchronizer coupled to said delay circuit output. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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29. A method for acquiring an incoming signal that conveys data through a stream of symbols, said method comprising the steps of:
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detecting first and second frequency errors for a plurality of symbols, said first and second frequency errors being detected for first and second sections of each symbol, respectively; identifying whether said frequency errors detected at said first sections are smaller than frequency errors detected at said second sections; and synchronizing symbol timing in response to said identifying step. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36)
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Specification