Estimation of the uncertainty for a phase noise optoelectronic metrology system

Abstract

The configuration of the phase noise measurement system operating in the X-band (8.2–12.4 GHz) using a photonic delay line as a frequency discriminator is presented in this paper. This system does not need any excellent frequency reference and works for any frequency in this band. Oscillator frequency fluctuation is converted into phase frequency fluctuation through the delay line. The measured phase noise includes the device under test noise and the instrument background. Then the use of a cross correlation decreases the cross spectrum terms of uncommon phase noise as √(1/m), where m is the average number. Using cross correlation on 500 averages, the noise floor of the instrument £(f) becomes, respectively, −150 and −170 dBc Hz−1 at 101 and 104 Hz from the 10 GHz carrier (−90 and −170 dBc Hz−1 including 2 km delay lines). We then focus on determining the uncertainty. There are two categories of uncertainty terms: ‘type A’, statistic contributions such as repeatability and experimental standard deviation; ‘type B’ due to various components and temperature control. The elementary term of uncertainty for repeatability is found to be equal to 0.68 dB. Other elementary terms still have lower contributions. This leads to a global uncertainty of 1.58 dB at 2σ.