Metrology and modelling of high frequency probes

[摘要] This study investigates high frequency probes through good metrology andcomputation software such as CST. A factor that can strongly influence the accuracyof measurements, is common mode (CM) current. Therefore, the main focus of thisproject was the CM current on the outside of an SMA, flanged, probe used formeasuring material properties.In the course of the investigation, a clamp-on CM current probe (CP) wascalibrated using a CST model and good measurements. This calibration dataindicated that the CP was invasive on the measurement setup and could not deliverthe accuracy required for the CM current measurement.In light of this, a second method was implemented where the material probewas placed within a cylindrical shield. A cavity was formed between the probe andthe walls of the shield in which the electric fields could be simulated and measured.These field measurements allowed measurements to be conducted in both the time-(TD) and frequency-domain (FD).For the TD measurements, a sampling oscilloscope was used. As the basicprinciple of a sampling oscilloscope differs from its real-time counterpart, thisprinciple, as well as the systematic errors associated with these devices, wasexplored.The results of the final measurements indicated that the TD results were withinan acceptable range of both the FD results, measured on the VNA, and the resultspredicted by CST. This study shows that CST can be used to simulate complexmeasurement setups and deliver reliable results in cases where an accuratemeasurement cannot be guaranteed.

[发布机构] Stellenbosch University