Y. Zhang et al., "Removing Random Phase Contributions of Sweeping Local Oscillator From Modulated RF Measurements," in IEEE Transactions on Microwave Theory and Techniques, vol. 66, no. 12, pp. 5737-5749, Dec. 2018. doi: 10.1109/TMTT.2018.2879507
This paper proposes a measurement strategy to remove the random phase contributions of the sweeping local oscillator (LO) from modulated radio frequency (RF) phase measurements based on down-conversion. To obtain a stable phase spectrum for each run of tone-by-tone sweeping measurement, the LO used for down-conversion is coupled out to an extra path and modulated to be a wideband multisine signal. By monitoring the phase change of multisine signal at a specific and fixed frequency point, random LO phase offsets during the frequency sweep can be measured and compensated. In this paper, two experimental test benches with the same core measurement strategy but different architectures are established for method validation. According to the experimental results using test bench one, the phase stability is ±(0.2~0.4) deg. at 1.8 GHz for fundamental mixing based down-conversion, and ±(0.6~1) deg. for harmonic mixing at 6 GHz. Based on test bench two, relative phase deviations of ±(0.8~1.2) deg. at 22 GHz for fundamental mixing, and ±(2~3) deg. at 66 GHz for harmonic mixing, are reachable.