S.W. Chua

Development of a 50 GHz coaxial direct comparison transfer microwave power sensor calibration system at NMC

This paper describes the continuous development of NMCs microwave power sensor calibration system using the direct comparison transfer method. The system uncertainties are evaluated for the complex reflection coefficient inputs in terms of real and imaginary components and its magnitude and phase format following the internationally recommended guidelines. Monte Carlo method is also used to numerically check the distribution of the output quantities. The measurement results and the uncertainties in different methods are presented and discussed.

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.

Bilateral comparison between NMC and INRIM on microwave power sensor using type N and 3.5 mm connectors

This paper describes the bilateral comparison between two national metrology institutes, NMC from Singapore and INRIM from Italy, concerning microwave power measurements with coaxial lines using type N (up to 18 GHz) and 3.5 mm (up to 26.5 GHz) connectors.

Direct comparison transfer microwave power sensor calibration system

This paper describes the development of a microwave power sensor calibration system using the direct comparison transfer method with a resistive power splitter. The system setup, its uncertainty analysis and measurement results are discussed.

A direct comparison of Josephson Array Voltage Standards

A number of direct comparisons of Josephson Array Voltage Standards (JAVS) using Superconductor-Insulator-Superconductor (SIS) junction arrays have been performed at the National Metrology Centre (NMC), Singapore. The comparisons were performed over a range of voltage from 1 V to 10 V and with different combinations of array chips, both USA and German made. The comparisons used a parallel biasing method that made it relatively easy to quickly bias both arrays on a nearly matched quantum step. The Type-A uncertainty of the difference voltage was typically lower than 1.5 nV.

Improvement on Shielding of a Cryogenic Current Comparator Bridge for Operation in an Unscreened Environment

This paper presents the investigation and improvement of an automated cryogenic current comparator resistance bridges shielding for a stable and accurate operation in an unscreened environment under adverse electromagnetic interference condition

Enhancements of NMC'S Josephson array voltage standard system

A series of system enhancements for the Josephson array voltage standard (JAVS) have been implemented to improve the efficiency and quality of dc voltage dissemination in the National Metrology Centre, A*STAR. Periodic direct comparison between two JAVS systems has been adopted as a quality assurance procedure to ensure accurate reproduction of the volt for calibration of secondary standards. A miniature millimeter-wave synthesizer is employed for better control of microwave power and locking frequency. Low thermal terminal reversing switches are introduced to minimize zero-offset measurement uncertainty. Monte Carlo method and ANOVA method are implemented in the data analysis and reporting.

RF-dc difference measurement system at NMC

This paper describes an automated RF-dc transfer difference measurement system developed at the National Metrology Centre, Singapore. The system uses calculable single junction thermal voltage converters as primary standards and various high frequency reference thermal converter standards to measure the RF-dc voltage transfer difference for frequency range from 100 kHz to 100 MHz at voltage range from 0.5 V to 10 V.

Quality Assurance for Josephson Array Voltage Standards

A series of quality assurance (QA) procedures for the Josephson array voltage standard (JAVS) has been implemented to improve the efficiency and quality of dc voltage measurements in the National Metrology Centre, Agency for Science, Technology, and Research (A*STAR), Singapore. Periodic direct comparisons between two JAVS systems are required in the QA procedure to ensure accurate representation of the volt for calibration of secondary standards. QA-oriented setup and procedure are developed for better control of microwave power and locking frequency when using the millimeter-wave synthesizer. The analysis-of-variance method and the Monte Carlo method are implemented in data reporting and uncertainty evaluation processes.

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.