High Frequency And Microwave Power Standard And Applications

High frequency and microwave power is one of the basic parameters inelectronic measurement. Establishing national standards for high frequency andmicrowave power measurement is an important basic research to ensure thetraceability to the International System of Units (SI) and the accuracy ofelectronics measurement in our country. Therefor, highfrequency and microwavepower measurement research is of great theoretical and practical value.Calorimeters and microcalorimeters are used for establishment of highfrequency and microwave low-power national standards in most of the nationalmetrology laboratories. With the analysis of calorimetry principles, the researchwork is focused on the shortcomings of traditional microcalorimeters and theirimpact on power measurement accuracy. The design of microcalorimeters isimproved and used for developingour national broadband coaxial power standard.Then the power transfer system is studied to improve the power metermeasurement and calibration process modeling. A new power meter calibrationsystem is designed for new power meters. Different from the traditional Law ofUncertainty Propagation, the Monte Carlo method is adapted for the uncertaintyevaluation of power measurement.The main contents and research contributions of this dissertation are asfollows:1. To solve measurement difficulty of the loss of heat isolation transmissionline in microcalorimeter, a method to switch HF and microwave power on and offperiodically is presented based on the heat transfer analysis of transmission line.The transmission line loss and effective efficiency is measured together in thismethod. So it simplifies the complexity of microcalorimeter and reduces theuncertainty source of effective efficiency measurement. It has been applied in thedevelopemt of Chinese broadband coaxial power standard. In this way goodresults of our countryin the international comparison of power areguaranteed.2. The modeling of power meter measurement and calibration process ismodified according to the characteristics of new commercial power meter, whichhas features of large power scale, self-calibration and self-correction. The original commercial power meter calibration system is improved to measurecorrection factor of commercial power meter directly. That reduces theuncertainty sources of calibration factor and correction factor. The measurementuncertainty is smaller than the uncertainty given by commercial power metermanufacturers.3. Heat transfer theory is used to analyze calibration process of thermistorpower sensor in microcalorimeter and power measurement process withthermistor sensor. The relation is deduceed between effective efficiency and heattransfer characteristics of thermistor power sensor and verified with the test dataof international comparison. A new defination, "real effective efficiency",unrelated to heat transfer characteristics is given to study the thermal equivalentmeasurement error that comes from effective efficiency variety. Several methodssuch as shortening the time of power measurement are suggested to reducethermal equivalent measurement error.4. The traditional Law of Uncertainty Propagation cannot handle mismatcherrors and obtain coverage factor of measurement uncertainty accurately. Toovercome these shortcomings, the Monte Carlo method is applied to evaluateuncertainties of power meter calibration factor, correction factor and powermeasurement results. The simulation results of uncertainty evaluation indicatethat itis better than the traditional Lawof UncertaintyPropagation.