Research On Power Density Standard In The Range Of (26.5-40)GHz

Power density and field strength are two important parameters for evaluating the intensity of electromagnetic radiation which is normally measured in units of power density at the microwave frequency range. Currently, a series of microwave power density standard device have been established in China, further expansion, however, is particularly needed in the band of Ka. The completion of microwave power density standard device ranging from26.5to40GHz has not only met the demands of measurement traceability requirements, but it can also facilitate China to participate in the international comparison of field strength parameters in this band. It will strengthen the competition of China in this field, and can further narrow the gap between China and technologically-advanced countries.In this thesis, the device is installed in a microwave anechoic chamber and a pyramidal horn, which is easy to be simulated and verified, is chosen to be a transmit antenna owing to its characteristics of narrow beam and high gain. By monitoring the power fed into pyramidal horn antenna, it can produce the expected field strength at a certain distance from its aperture spindle. The expected field strength produced by this method is closer to the theoretical field strength.This thesis elaborates more on the critical technological issues in the establishment of this device. For instance, how to calculate the net power fed into horn antenna by using the accurate calculation of coupling coefficient and the scattering parameters of the directional coupler; how to simulate the horn antenna gain by using HFSS-the technology of FEBI and thus accurately verify the horn antenna near-field gain; how to optimize the measurement condition; how to lower the adverse impact of standing wave effect caused by the absorbing material etc. via evaluating the calibration area. Meanwhile, in practical, two probe brackets are designed in order to measure the isotropic response of the probe. The software of the controlling system has been developed based on VB, through which more accurate and faster expected fields can be generated by a higher degree of cooperation between signal generator and power amplifier. Numerical identification and calibration certificate of the probe are automatically issued by the other software based on LabVIEW, which also improves the efficiency of electric field probe calibration on condition that the measurement results are guaranteed to be credible. Finally, at four separate frequency points, the uncertainty evaluation model of the transparent and black box is established. According to the research on the uncertainty evaluation theory, an uncertainty evaluation of the system, which is more detailed and comprehensive, has been conducted.