Thomas Y. Wu

Analysis of phase noise effect on microwave attenuation precision measurement using a heterodyne receiver

The phase noise effect on microwave attenuation precision measurement using a lock-in amplifier (LIA) is studied. A frequency domain phase noise modeling is used to analyse the phase sensitive detection made by the LIA. The error bound for the magnitude and phase of LIA measurement has been established. The theoretical prediction of the maximum magnitude and phase fluctuation in LIA output agrees with the measured data quite well. This analysis is important for estimating the maximum attenuation measurement error caused by the phase noise of microwave sources and its uncertainty contribution to microwave attenuation measurement.

Broadband microwave attenuation measurement standard in the frequency range from 10 MHz to 26.5 GHz

A broadband microwave attenuation measurement standard using audio frequency substitution method is described in this paper. The broadband standard includes a single channel and a dual channel system. The single channel system is used to perform accurate attenuation measurement from 10 MHz to 2 GHz. From 2 GHz to 26.5 GHz, the dual channel system is used to reduce the receiver noise and improve the measurement accuracy. Attenuation up to 110 dB can be measured by this standard. The measurement uncertainty of the standard is also analyzed. The expanded measurement uncertainties of a 0.01 dB ~ 110 dB variable attenuator are estimated to be 0.0028 dB ~ 0.028 dB from 10 MHz to 26.5 GHz.

The accurate measurement of microwave phase-shift using a dual-channel heterodyne system

A dual-channel heterodyne microwave phase-shift measurement system has been developed. This system is used to provide accurate transmission phase measurement of various devices and phase-shift standards from 50 MHz to 2 GHz. The system design and measurement uncertainties analysis are given in this paper. A beadless coaxial air line has been used as a phase-shift standard to verify the system performance and its phase-shift is calculated with consideration of its insertion loss. The measured phase-shift value agrees with the calculated values within the measurement uncertainties. The estimated phase measurement uncertainty is 0.055 to 0.2 degrees for variable attenuators with attenuation up to 140 dB.

Comparison of a single channel and a dual channel microwave attenuation measurement system

The performance of a single channel microwave attenuation measurement system is compared to a dual channel implementation. The results show that a single channel system is more suitable for attenuation measurement from 10 MHz to 4 GHz since it can cover this frequency range using only two bands, while a dual channel system has to be used for attenuation measurement from 4 GHz to 26.5 GHz since the receiver reading is more stable in this frequency range.

Evaluation of mismatch uncertainty in microwave power sensor calibration using Monte-Carlo method

The mismatch uncertainty in microwave power sensor calibration system is analyzed. Propagation of uncertainties from the reflection coefficients in real and imaginary format are considered. Monte Carlo method (MCM) is used to estimate the probability distribution function (PDF) of the mismatch factor, which is found to be non-Gaussian for small reflection coefficient values. The mismatch uncertainties estimated using MCM for various reflection coefficient values are larger than those obtained by the method recommended in the Guide to the Expression of Uncertainty in Measurement (GUM). This study shows that MCM gives more reliable mismatch uncertainty estimation than a conventional GUM method in microwave power sensor calibration.