Uncertainty of Millimeter-Wave Channel Sounder due to Integration of Frequency Converters

In this study, we investigate the possible sources of measurement uncertainties with the integration of radio over fiber solution and frequency converters in millimeterwave sounders. We examined analytically the effect of phase variations due to the disturbance of the optical fiber cable, the limited sideband suppression of the frequency converters, and the influence of the dispersion in rectangular waveguides to the response of the channel sounder. Characterization of the optical fiber cable confirms that disturbance of the cable leads only to phase variation. Back-to-back measurements of Aalto's sounder operating at V- and D-bands also verify that disturbance of the cable supplying the local (LO) continuous-wave signals are most influential to the stability of frequency- and delay-domain responses of the sounder because the LO signals undergo frequency multiplication. We found that the V-band and D-band channel sounders, with at least 17 dB and 20 dB Image Rejection Ratio, have the maximum gain variation of 0.5 dB and 1.0 dB in the peak of channel impulse responses when subject to different fiber cable positions.