Communications device and related method with improved acquisition estimates of frequency offset and phase error

A method of processing a communications signal, comprising:

• receiving within a modem a repeated preamble bit pattern for a binary phase shift keyed (BPSK) communications signal;
• generating an initial frequency offset estimate and phase error estimate by detecting the repeated preamble bit pattern for a block of samples within the communications signal;
• correlating two halves of the block of samples with a plurality of different BPSK shifted sequences and obtaining a symbol timing estimate by determining the shifted sequence that provides the maximum correlation value;
• and
• acquiring a refined acquisition estimate of the frequency offset and phase error of the received communications signal by processing iteratively through an N number of times the steps of performing a complex conjugate dot product between the two halves of the correlation outputs and determining the frequency offset adjustment, updating the frequency offset estimation based on the initial frequency offset estimate and the frequency offset adjustment, rotating the initial block of samples corresponding to the negative of the initial frequency offset by the updated frequency offset estimate and performing a complex correlation in two halves with the shifted sequence that corresponds to the maximum correlation value.

A communications device, comprising:

• a signal input for receiving a binary phase shift keyed (BPSK) communications signal having a repeated preamble bit pattern;
• a modem that processes the BPSK communications signal and further comprising a demodulator and processor that generates an initial frequency offset estimate and phase error estimate by processing a Fast Fourier Transform (FFT) that detects the repeated preamble bit pattern for a block of samples within the communications signal, correlates two halves of the block of samples with a plurality of different BPSK shifted sequences to obtain a symbol timing estimate and determine a maximum correlation value, and updates a frequency offset estimate iteratively an N number of times using the shifted sequence which provided the maximum correlation value to refine an acquisition estimate of the frequency offset and phase error of the received communications signal;
• and
• radio circuitry operative with the modem for processing communications data obtained from the communications signal.