Method of carrier frequency estimation

A method of estimating the unknown frequency of a carrier contained in a received data signal within a search bandwidth, comprising the steps of:

• taking a multiplicity of time domain samples of the data signal;
• performing a single Fast Fourier Transform on said samples to obtain a plurality of power spectral density components at discrete points across the search bandwidth;
• filtering said power spectral density components;
• moving a search window encompassing three power spectral density components across said search bandwidth to determine an area of greatest power concentration;
• and
• computing a weighted average frequency from the plurality of power spectral density components in the area of greatest power concentration in accordance with the following formula:
• ##EQU3## where:
• Pa, Pb, Pc=power spectral density components
• a, b, c=frequencies of components
• said frequency being said estimated carrier frequency of said data signal.

A method of estimating an uncertain data signal carrier frequency in a search bandwidth, comprising the steps of:

• obtaining a plurality of samples at predetermined intervals;
• performing transforms on said samples to generate power spectral density components at discrete points across the search bandwidth;
• filtering said components with averaging filters;
• moving a search window across said filtered components to locate an area of greatest power concentration;
• computing a center frequency of the area of greatest power concentration to estimate the carrier frequency;
• monitoring frequency lock of a frequency-locked demodulator by comparing the carrier frequency estimate with a current demodulator frequency to obtain a difference frequency;
• and
• indicating a loss of lock if said difference frequency exceeds a predetermined value for a predetermined time.