APPARATUS AND METHOD FOR EFFICIENT WIRELESS COMMUNICATIONS IN THE PRESENCE OF FREQUENCY ERROR

A receiver (fig.1) for efficient wireless communications in the presence of frequency error in a radio frequency received signal is disclosed. The receiver (fig.1) comprising a receiver channel, a wide band frequency acquisition mode (23), automatic frequency control (33, 41, 43, 45, 57, 55, 53), a narrow band demodulation mode (27) and a demodulator (35). The receiver channel has a variable bandwidth and an approximately fixed receiver mid-channel frequency (fig.4). The wide band frequency acquisition mode comprises a wide channel filter which initially defines the bandwidth to be greater than the frequency error in the received signal and wherein the frequency error is determined by comparing the received signal frequency to the receiver mid-channel frequency. The automatic frequency control comprises at least one frequency adjustable local oscillator (55) which adjusts the local oscillator based upon the frequency error such that the frequency difference between the receiver mid-channel frequency and the receiver signal is made negligible, thereby approximately centering the received signal within the bandwidth in the wide band frequency acquisition mode. The narrow band demodulation mode (27) comprises a narrow channel filter which narrows the bandwidth of the receiver channel with respect to the wide band frequency acquisition mode maintains approximately the same receiver mid-channel frequency. The demodulator (35) demodulates the received signal in the narrow band demodulation mode. L'invention se rapporte à un récepteur (Fig.1) destiné à des communications radio efficaces même en présence d'erreurs de fréquence dans un signal reçu en fréquence radio. Ledit récepteur comporte une voie réceptrice, un mode d'acquisition de fréquence large bande (23), un régulateur automatique de fréquence (33, 41, 43, 45, 57, 55, 53) un mode de démodulation en bande étroite (27) et un démodulateur (35). La voie réceptrice possède une largeur de bande variable et une fréquence de mi-voie réceptrice sensiblement fixe (Fig. 4). Le mode d'acquisition de fréquence large bande comporte un filtre de voie large qui définit initialement la largeur de bande comme étant supérieure à l'erreur de fréquence du signal reçu et dans lequel l'erreur de fréquence est déterminée par comparaison de la fréquence du signal reçu avec la fréquence de mi-voie réceptrice. Le régulateur automatique de fréquence comporte au moins un oscillateur local (55) réglable en fréquence, qu'il ajuste en fo