Patent ID: 6879647
Filing Date: 2005-04-12
Classification: H04L

Abstract:
1. In a radio receiver adapted to receive a carrier signal carrying a coded signal representing symbols coded at a predetermined symbol rate by amplitude modulated minimum shift keying, apparatus for processing the coded signal comprising: a detector arranged to detect the coded signal; and a transformer arranged to transform the detected coded signal into two complex baseband signals representing offset minimum phase shift keying of said coded signal, wherein said apparatus comprises a digital processor and wherein said detector and transformer comprise portions of an algorithm executed by said digital processor, wherein said carrier signal frequency is shifted by a Doppler frequency and further comprising a Doppler canceler arranged to cancel said Doppler frequency shift from said MSK baseband signal, wherein said Doppler canceler comprises a portion of an algorithm executed by said digital processor: a phase calculator arranged to calculate the phase represented by said complex baseband signal; a phase modulation component remover; a second transformer arranged to generate a second complex baseband signal in response to the output of the phase calculator and a third complex baseband signal in response to the output of the phase modulation component remover; and a multiplier responsive to the values represented by the second and third complex baseband signals.