Channel tracking in a mobile receiver

In a method carried out in a receiver where an incoming signal is demodulated with a local oscillator that is close in frequency to the frequency of the carrier signal, where a channel characteristics estimate is developed in accordance with a given algorithm in response to an output signal of the demodulator, and where a detector is responsive to the output signal of the demodulator that is modified in accordance with said channel characteristics, the improvement comprises the steps of:

• developing an offset frequency estimate by carrying out said given algorithm on said incoming signal;
• modifying said output signal of said demodulator with said offset frequency estimate, and
• developing said channel characteristics estimate from said output signal of the demodulator, as modified by said step of modifying.

A receiver adapted for use in a mobile environment which includes a receiver front end for receiving a phase modulated carrier signal, a demodulator responsive to the received signal that employs a local oscillator which is offset in frequency from the frequency of the carrier signal, and a processor responsive to the output signal of said demodulator for estimating characteristics of a channel through which the signal applied to said receiver front end has passed, which processor employs a given algorithm, the improvement in said receiver comprising:

• a frequency offset processor interposed between said demodulator and said processor for estimating in said receiver characteristics of said channel, said frequency offset processor employing said given algorithm to correct for said offset in frequency;
• and
• a detector coupled to said frequency offset processor and to said processor for estimating characteristics of said channel.

A receiver adapted for use in a mobile environment which includes a receiver front end for receiving a phase modulated carrier signal, a demodulator responsive to the received signal that employs a local oscillator which is offset in frequency from the frequency of the carrier signal, and a processor responsive to the output signal of said demodulator for estimating characteristics of a channel through which the signal applied to said receiver front end has passed, which processor employs a given algorithm, the improvement in said receiver comprising:

• first means, interposed between said demodulator and said processor for developing a measure of said offset in frequency by performing said given algorithm upon an output signal of said demodulator, and for developing a frequency-compensated signal based on said developed measure;
• and
• second means, responsive to said first means and to said processor, for detecting a signal that modulated said phase modulated signal.

A receiver adapted for use in a mobile environment which includes a receiver front end for receiving a phase modulated carrier signal, a demodulator responsive to the received signal that employs a local oscillator which is offset in frequency from the frequency of the carrier signal, a processor responsive to the output signal of said demodulator for estimating characteristics of a channel through which the signal applied to said receiver front end has passed, which processor employs a given algorithm, and a detector responsive to said processor and to said output signal of said demodulator, the improvement in said receiver comprising:

• means, interposed between said demodulator and said processor for developing a measure of said offset in frequency by performing said given algorithm upon an output signal of said demodulator, and for developing a frequency-compensated signal based on said developed measure.