Amplitude modulation measurement of symmetrical microwave power sensor

In order to reduce the mismatch error, a direct current （DC） calibration method is introduced when the modulated microwave signal is measured. The microwave power is input to the left section of the power sensor, and the DC power is input to the right of the power sensor. Due to the existence of parasitic loss and electromagnetic coupling, the microwave power results in a mismatch error. However, the DC power does not have the mismatch error. So the DC power applied in the right section can calibrate the mismatch error of the microwave power in the left section. The calibration factor is measured at different modulation rates and modulation depths.The measurement results show that the carrier frequency is the major factor influencing the measurement results. After calibration, the carrier frequency and the modulation rate have little effect on the output voltage. The frequency response becomes relatively flat in the frequency range up to 20 GHz, and the sensitivity on average is enhanced by about 0.12 mV/dBm. Therefore, the DC calibration method has a certain reference value for the terminal-type microwave power sensor.

Autonomous vicarious calibration based on automated test-site radiometer

We employ the in-site automated observation radiometric calibration（AORC） approach to perform vicarious calibration, which does not require the manual efforts of a field team to measure the surface conditions. By using an automated test-site radiometer（ATR）, the surface radiance at any moment in time can be obtained. This Letter describes the AORC approach and makes use of data to compute top-of-atmosphere radiance and compare it to measurements from the Moderate Resolution Imaging Spectroradiometer. The result shows that the relative deviation is less than 5% and the uncertainty is less than 6.2%, which indicates that the in-site AORC maintains an accuracy level on par with traditional calibration.

Application of real-time digitization techniques in beam measurement for accelerators

Beam measurement is very important for accelerators. In this paper, modern digital beam measurement techniques based on I Q（In-phase ＆ Quadrature-phase） analysis are discussed. Based on this method and highspeed high-resolution analog-to-digital conversion, we have completed three beam measurement electronics systems designed for the China Spallation Neutron Source（CSNS）, Shanghai Synchrotron Radiation Facility（SSRF）, and Accelerator Driven Sub-critical system（ADS）. Core techniques of hardware design and real-time system calibration are discussed, and performance test results of these three instruments are also presented.