Determining frequency offset of signal under test

A system for processing a multi-tone base-band in-phase and quadrature (IQ) data signal in a time domain, the system comprising:

• a processor configured to execute instructions;
• and
• a memory coupled to the processor, the memory storing instructions which when executed by the processor cause the processor to:
• estimate an initial frequency offset based on the base-band IQ signal in the time domain and the block size for a reference multi-tone signal constructed in a frequency domain, wherein the initial frequency offset estimation is based on a partial frequency-bin offset estimation in the time domain;
• compensate for the estimated initial frequency offset, and transform a resultant compensated signal to the frequency domain, wherein a remaining frequency offset of the compensated signal in the frequency domain is an integer number of unit spacings of the reference multi-tone signal;
• cross-correlate the magnitudes of the compensated signal in the frequency domain and the reference multi-tone signal for each of shifted positions of the compensated signal in the frequency domain relative to the reference multi-tone signal to determine a shifted position having a peak cross-correlation, the shifted position relative to an original position constituting an integer number of frequency-bin offsets;
• and
• determine the frequency offset of the base-band IQ signal as the sum of the partial frequency-bin offset and the integer number of frequency-bin offsets.

A non-transitory computer readable storage medium storing instructions that when executed by a processor cause the processor to:

• acquire a base-band in-phase and quadrature (IQ) data signal;
• acquire data indicative of a reference multi-tone signal;
• estimating an initial frequency offset based on the acquired IQ data signal and data, wherein the initial frequency offset estimation is based on a partial frequency-bin offset estimation in the time domain;
• compensate for the estimated initial frequency offset, and transform a resultant compensated signal to the frequency domain, wherein a remaining frequency offset of the compensated signal in the frequency domain is an integer number of unit spacings of the reference multi-tone signal;
• cross-correlate the magnitudes of the compensated signal in the frequency domain and tones of the reference multi-tone signal for each of shifted positions of the compensated signal in the frequency domain relative to the reference multi-tone signal to determine a shifted position having a peak cross-correlation, the shifted position relative to an original position constituting an integer number of frequency-bin offsets;
• and
• determine the frequency offset of the base-band IQ signal as the sum of the partial frequency-bin offset and the integer number of frequency-bin offsets.