METHOD AND SYSTEM FOR CALIBRATING PHASES OF COMB TEETH IN COMB SIGNAL WITH PILOT TONE AND USING CALIBRATED COMB TEETH PHASES TO MEASURE A DEVICE UNDER TEST

摘要

A system and method sequentially measure phases of selected comb teeth of a comb signal using a local oscillator (LO) signal whose frequency and phase are changed for each sequential measurement, and adjust the measured phases to account for the change of phase in the LO signal from measurement of one selected comb tooth to the next to ascertain reference phase differences between the selected comb teeth. The measured phases of the selected comb teeth are adjusted by applying a phase offset determined from a first phase and a second phase of a pilot tone which are measured using the LO signal, respectively, before and after the frequency and phase of the LO signal change from measurement of one comb tooth to the next. The frequency of the pilot tone is maintained to be substantially the same when measuring the first phase and the second phase of the pilot tone.

主权项

1. A method, comprising:
producing a pilot tone with a pilot tone generator; receiving a comb signal having a plurality of comb teeth, wherein selected comb teeth among the plurality of comb teeth span a selected bandwidth of the comb signal; sequentially converting the selected comb teeth to a first intermediate frequency (IF) signal in a first IF channel by mixing the comb signal with a local oscillator (LO) signal, wherein a frequency of the LO signal is changed for each sequential conversion such that for each frequency of the LO signal at least one of the selected comb teeth is converted to fall within the first IF channel, and sequentially measuring calibration phases of the converted selected comb teeth in the first IF channel using a first measurement device whose measurement bandwidth for any frequency of the LO signal is less than the selected bandwidth of the comb signal; mixing the pilot tone with the LO signal to produce a converted pilot tone in a second IF channel, during at least some of the sequential conversions,
measuring a first phase of the converted pilot tone with the converted pilot tone at a first frequency in the second IF channel prior to changing the frequency of the LO signal,measuring a second phase of the converted pilot tone with the converted pilot tone at a second frequency in the second IF channel subsequent to changing the frequency of the LO signal, where the frequency of the pilot tone is maintained to be substantially the same in measuring the first phase of the converted pilot tone as in measuring the second phase of the converted pilot tone, andafter measuring the first and second phases of the converted pilot tone, and before changing the frequency of the LO signal again, changing the frequency of the pilot tone such that the converted pilot tone is at the first frequency in the second IF channel; and ascertaining reference phase differences between the converted selected comb teeth using the measured calibration phases of the converted selected comb teeth and the measured first and second phases of the converted pilot tone.