High-frequency current transformers are popular noninvasive inductive wideband sensors. Despite simplicity in design and operational principle, implementation of such sensors for partial discharge applications requires careful consideration, particularly in the higher frequency range where traveling wave attenuation and distortion is relevant. First, the role of design variables, including core materials, winding design, and shielding practices on sensor sensitivity and frequency characteristics (transfer impedance) are presented. Next, the suitability of the constructed sensors for partial discharge applications is assessed. The designed wideband sensors are suitable for laboratory applications with standard measurement circuits and controlled conditions. The low-level magnitude and frequency spectrum of the discharge pulses hinders signal integrity in relation to the placement of the sensors within the measurement circuit, signal amplification, and pulse repetition rate (pulse resolution). To enable most stringent detection levels under 1 pC, efforts are needed in distortionless amplifier design and interference mitigation. 

This paper describes a bilateral comparison between PTB and SP on the calibration factor of a 2.92 mm thermocouple power sensor. The measurements were done at 0 dBm from 50 MHz to 40 GHz. The comparison also covers the sensor reflection coefficient over the same frequency range.

The fundamental and most straightforward method for high performance time and frequency transfer is the two-way technique, which is suitable when the user has access to the whole system, and when both transmission paths are equal or with a known and predictable asymmetry. Furthermore it is most practical when the numbers of users are limited and when no security concerns limit the bidirectional connectivity.

A method for measuring the reflection coefficient and absolute power in the propagating waves from a circuit embedded in a planar circuit environment is presented. The method utilizes a pair of inductive and capacitive probes. The standard one-port vector-network-analyzer calibration is extended to allow the measurement of power in the forward and backward waves. Experimental results are presented for measurements between 700 MHz and 20 GHz. Good agreement between the new noncontacting method and a standard coaxial measurement method is demonstrated up to 12 GHz for power and up to 14 GHz for the reflection coefficient. The method is useful for in-circuit testing of open transmission-line structures, e.g., microstrip.

A method for measuring S-parameters of a circuit embedded in a planar circuit environment is presented. The method utilizes an inductive and a capacitive probe. Experimental results are presented for probe measurements of reflection coefficient from 0.7 to 20 GHz with good agreement to verifying measurements up to 14 GHz. The method shows great promise for in-circuit Sparameter testing that has previously required physical modification or even complete disassembly to test sub-circuits in a microstrip environment.