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Electromagnetic coupling between planar devices can degrade microwave calibrations and, consequently, the accuracy of a measurement. This letter describes measurement-based methods that can identify, assess, and visualize the electric field coupled between the adjacent planar calibration structures. The coupling within a printed circuit board (PCB)-based and an on-wafer impedance standard substrate is successfully demonstrated and analyzed up to 4 and 20 GHz, respectively, through S-parameter and electric-field measurements obtained using an electrooptic probing system.

An optically-controlled reconfigurable NRI-TL metamaterial phase shifter operating at 3.6 GHz is proposed. A host transmission line with a fixed length loaded with series capacitors and shunt inductors is used to achieve reconfigurability, while the optical control is introduced by integrating highly resistive silicon switches within the shunt branches of the NRI-TL design. The two states of the phase shifter result in a phase shift of ±60° leading to a differential phase shift of 120° with an insertion loss of 1.3 dB and 1.8 dB respectively. The operational bandwidth of the phase shifter is between 3.45–3.75 GHz. The versatile optical control and the high-frequency response make the proposed NRI-TL phase shifter well suited for 5G antenna array applications.

In this paper, a surrogate modeling-based acceleration technique for multi-harmonic phase-coherent electrooptic near-field measurements is presented. The implementation uses an adaptive sampling and modeling algorithm instead of the conventional raster scanning approach, which reduces the measurement time by a factor of 9, from 7 hours to 45 minutes, and the number of samples by a factor of 23, from 10556 to 464, while maintaining the average measurement error under 5%. The reduction in measurement time helps to preserve the accuracy of the multi-harmonic near-field measurements, asthe electro-optic measurement system response can drift over time, due to thermal fluctuations in the measurement environment.

An active interferometry-based measurement configuration for the reference impedance renormalization of a vector network analyzer is presented. The method can be implemented using only a 2-source vector network analyzer, reducing the set-up complexity required. High-impedance surface mount resistors are used to demonstrate the impedance renormalization by minimizing their high reflection. In addition, the method is implemented using the network analyzer’s software.

An optically reconfigurable metasurface is proposed for use as an antenna radiator at 28 GHz. The metasurface is transmittive and is fed through a horn antenna connected to a multi-core-fibre link, significantly reducing the losses compared to a mm-wave feed. In the proposed system, radiated beams will be photonically controlled using a spatial light modulator, thus not requiring the use of optical fibers. For optical reconfigurability the switching component will be based on silicon instead of photodiodes and varactors, eliminating the need for an active biasing network.

For reliability predictions, gallium nitride transistors require accurate estimations of the peak operating temperatures within the device. This article presents a new application of thermoreflectance-based temperature measurements performed on a gallium nitride high electron mobility transistor. The submicron spatial and nanosecond temporal resolutions of the measurement system enables for the first time, the dynamic temperature measurement of a transistor operating up to 5 MHz. The gallium nitride transistor is first biased in class-A and excited with a 1 MHz ac signal to demonstrate the dynamic temperature measurement. The transistor is, then, incorporated in a 20–40 V dc–dc boost converter to measure the dynamic temperature distributions across the semiconductor die operating under real loading conditions at 1 and 5 MHz switching frequencies. This technique captures the temperature variations that occur during the switching of the transistor and the recorded peak temperatures are 7.4 $^{\circ }$ C higher compared with conventional measurement and simulation approaches.

In this paper a thermoreflectance measurement technique is used to capture the channel temperature within a GaN-on-Si HEMT during pulsed I-V excitation. Using pulsed I-V measurements in combination with thermoreflectance measurements allows the direct assessment of the isothermal approximation that is often made during the characterization of the transistor for nonlinear model development. The thermoreflectance measurement has a temporal response of 50 ns, which is sufficiently fast to measure the temperature rise within the pulsed I-V excitation, across the I-V plane of the transistor. We first determine the minimum pulse duration needed to minimize the temperature rise as assessed from drain current measurements as a function of the excitation pulse width. The thermoreflectance measurements show that self-heating occurs during the pulse, revealing a maximum of 13.5°C change over all pulsed I-V measurements. Transient thermoreflectance measurements were then performed to determine that sub-200 ns pulses are required to eliminate the self-heating for this device.

This paper presents results from an interlaboratory comparison of S-parameter measurements where the measurement uncertainty has been evaluated using the dynamic uncertainty option within the PNA vector network analyzer (VNA) from Keysight Technologies. The same devices were measured at two different laboratories (NPL, UK, and the University of Surrey, UK), both using a VNA with the dynamic uncertainty option. Several one- and two-port devices were chosen with a range of different values of reflection and transmission coefficients. The uncertainty of the S-parameter measurements has been evaluated for two different calibration methods (short-open-load-reciprocal and electronic calibration) and these are also reported. The investigation was carried out over the frequency range 100 MHz to 26 GHz which covers many of today’s RF and microwave applications.

This paper presents a microwave impedance characterization technique for extreme impedance devices. The method is based on active interferometry and uses a 2-source 4-port vector network analyzer, which allows for a compact and straight-forward implementation. A new calibration algorithm is described that incorporates error terms from two separate three-known-load calibrations. Based on simulated and measured data, the proposed technique shows substantial improvement in obtaining the impedance of two offset-short devices when compared with conventional measurements.

This paper presents the extraction of the complex propagation constant from carbon fiber reinforced plastic (CFRP) transmission lines up to 5 GHz. A test-fixture is designed and fabricated to obtain the propagation constant using a line-line extraction method. Use of this method reduces the required number of fabricated transmission lines compared to calibration algorithms such as TRL. Comparison of the extracted propagation constant with simulation data indicates CFRP conductivity of 1.0 –1.5x104 S/m.

This paper presents the experimental verification, imaging and animation of the radiation and coupling generated due to a coaxial-to-microstrip transition using electro-optic based measurements. The measured and simulated scattering parameters of a 50-Ω microstrip transmission line accessed with two SMA microwave end launch connectors are presented. An electro-optic based system and a vector network analyzer are integrated to measure the normal electric field component of the device at multiple frequencies up to 10 GHz. The measurements capture the radiation due to the coaxial-to-microstrip transition. Finite-element-method (FEM) based electric field simulations show a very good agreement with the measured results.

The feasibility of using self‐assembled InAs nanowire bottom‐gated field‐effect transistors as radio‐frequency and microwave switches by direct integration into a transmission line is demonstrated. This proof of concept is demonstrated as a coplanar waveguide (CPW) microwave transmission line, where the nanowires function as a tunable impedance in the CPW through gate biasing. The key to this switching capability is the high‐performance, low impedance InAs nanowire transistor behavior with field‐effect mobility of ≈300 cm2 V−1 s−1, on/off ratio of 103, and resistance modulation from only 50 Ω in the full accumulation mode, to ≈50 kΩ when the nanowires are depleted of charge carriers. The gate biasing of the nanowires within the CPW results in a switching behavior, exhibited by a ≈10 dB change in the transmission coefficient, S21, between the on/off switching states, over 5–33 GHz. This frequency range covers both the microwave and millimeter‐wave bands dedicated to Internet of things and 5G applications. Demonstration of these switches creates opportunities for a new class of devices for microwave applications based on solution‐processed semiconducting nanowires.

On-wafer microwave characterization and uncertainty evaluation of two-port coplanar waveguide (CPW) high impedance nanodevices are proposed. The test devices are manufactured with resistive metallic nano-films integrated in tapered CPW structures. Microwave conductance in the range 100–500 $\mu \mathbf{S}$ associated to parallel capacitances in the order of hundreds aF are exemplary shown up to 20 GHz. The uncertainty corresponding to the post-calibration residual errors-terms is provided. In addition, a sensitivity analysis investigating technological process variability using FEM-based EM modelling is considered.

This paper presents the modelling of a coplanar-waveguide bottom-gated FET switch using indium-arsenide nanowires. The nanowires have been included on the switch using dielectrophoresis, which is a solution processable technique. This is a necessary first step towards developing a fully printable switch on a flexible substrate, for low cost microwave devices, built using additive manufacturing methods. The measured S-parameters show the switching capabilities of the device with an insertion loss of 9 dB, when the switch is open (gate voltage $\geq \mathbf{60}\ \mathbf{V}$ ). The development of a distributed circuit model that matches the measured data is described, alongside the calculated network parameters used to represent the coplanar-waveguide and the nanowires. The model fits the measured results within 8%, making it suitable for inclusion in a CAD based circuit simulator.

Nano-scale devices and high-power transistors present extreme impedances, which are far removed from the 50- ${\Omega }$ reference impedance of conventional test equipment, resulting in a reduction in the measurement sensitivity as compared with impedances close to the reference impedance. This letter describes a novel method based on active interferometry to increase the measurement sensitivity of a vector network analyzer for measuring such extreme impedances, using only a single coupler. The theory of the method is explained with supporting simulation. An interferometry-based method is demonstrated for the first time with on-wafer measurements, resulting in an improved measurement sensitivity for extreme impedance device characterization of up to 9%.

International audience; This paper describes the design, fabrication, and testing of an on-wafer substrate that has been developed specifically for measuring extreme impedance devices using an on-wafer probe station. Such devices include carbon nano-tubes (CNTs) and structures based on graphene which possess impedances in the k Omega range and are generally realised on the nano-scale rather than the micro-scale that is used for conventional onwafer measurement. These impedances are far removed from the conventional 50-Omega reference impedance of the test equipment. The on-wafer substrate includes methods for transforming from the micro-scale towards the nano-scale and reference standards to enable calibrations for extreme impedance devices. The paper includes typical results obtained from the designed wafer.