发明授权
US5440265A Differential/coherent digital demodulator operating at multiple symbol points 失效
差分/相干数字解调器在多个符号点运行

Differential/coherent digital demodulator operating at multiple symbol
points
摘要:
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.
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