Communication signal detection and acquisition

摘要

The presence of a communication signal having a predetermined recognition pattern of symbols that occur at a predetermined rate (1/T) is detected by processing the communication signal to extract in-phase (I) and quadrature-phase (Q) components of the symbols; processing the extracted components to compute a complex autocorrelation function of the extracted components with a time parameter equal to an integer multiple (nT) of the symbol period (T); integrating the complex autocorrelation function over a substantial portion of the recognition pattern; and comparing the magnitude of the integrated complex autocorrelation function with a predetermined threshold value to detect the presence of the recognition pattern. The communication signal is acquired at a given intermediate frequency and at a given phase by adjusting the frequency of a local oscillator signal in response to a frequency error signal provided by processing the real and imaginary components of the integrated complex autocorrelation function and by adjusting the phase of the local oscillator signal in response to a phase error signal provided by processing extracted I and Q components of the communication signal to compute an arctangent of a quotient of a sum of the values of the Q components extracted over an integer multiple (rT) of the symbol period divided by a sum of the values of the I components extracted over the integer multiple (rT) of the symbol period.