US 6,603,819 B1Granted

Radio symbol synchronization and doppler estimation techniques

AssigneeNorthrop Grumman Corporation

InventorMichael H. Myers

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Abstract

A radio receiver (10) processes a carrier signal having a Doppler shifted frequency and carrying a coded signal having variable phase and amplitude. The coded signal is divided into a preamble portion and a message portion. A memory (23) stores samples of the coded signal representing at least some of the predetermined symbols of the preamble. A logic unit (16) divides the stored samples into a plurality of sample groups and identifies one sample group having the minimum variation of envelope amplitude. That sample group is used to provide additional samples by which the Doppler shift of the carrier frequency is estimated (70). The coded signal is delayed by a delay operation (100) and has its Doppler shift reduced. The Doppler reduced coded signal is processed by a filter operation (120) and a demodulator (130).

Claims14

Dependent claims

In a radio receiver adapted to receive a carrier signal having a Doppler shifted frequency and carrying a coded signal having a variable amplitude, said coded signal representing symbols coded by phase, said symbols being divided into a preamble portion defining a predetermined code and a message portion and being generated at a predetermined symbol rate, apparatus for processing said coded signal comprising:

a memory connected to store samples of said coded signal representing at least some of said predetermined symbols of said preamble, said stored samples having variable amplitudes;
and
a logic unit dividing said stored samples into a plurality of sample groups, identifying one sample group of said sample groups having a predetermined amplitude relationship with respect to other of said sample groups, selecting samples of said coded signal in response to said identification of said one sample group, estimating the Doppler frequency of said selected samples, delaying the message portion of said coded signal, reducing the Doppler frequency of said coded signal in response to the estimating of the Doppler frequency to generate a Doppler reduced coded signal, filtering the Doppler reduced coded signal, and demodulating said message portion in response to said Doppler reduced coded signal to facilitate recovery of the message portion of said coded signal.

In a radio receiver adapted to receive a carrier signal having a Doppler shifted frequency and carrying a coded signal having a variable amplitude, said coded signal representing symbols coded by phase, said symbols being divided into a preamble portion defining a predetermined code and a message portion and being generated at a predetermined symbol rate, a method of processing said coded signal comprising:

storing samples of said coded signal representing at least some of said predetermined symbols of said preamble, said stored samples having variable amplitudes;
dividing said stored samples into a plurality of sample groups;
identifying one sample group of said sample groups having a predetermined amplitude relationship with respect to other of said sample groups;
selecting samples of said coded signal in response to said identification of said one sample group;
estimating the Doppler frequency of said selected samples;
delaying the message portion of said coded signal;
reducing the Doppler frequency of said coded signal in response to the estimating of the Doppler frequency to generate a Doppler reduced coded signal;
filtering the Doppler reduced coded signal;
and
demodulating said message portion in response to said Doppler reduced coded signal to facilitate recovery of the message portion of said coded signal.

7 more elements

Dependencies are inferred from the claim text.