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Photo-induced coded-aperture imaging (PI-CAI) based on compressed sensing (CS) at 590 GHz using a WR-1.5 (500–750 GHz) vector network analyser is demonstrated. For a 256-pixel (16 × 16) frame, the acquisition time can be reduced by 40%, as compared with PI-CAI without CS, while maintaining high imaging quality. On the basis of this approach, it is envisioned that real-time (26 fps) THz imaging with 1000 pixels (32 × 32) can be realised using high-speed digital micromirror device chipsets and optimised data-acquisition software.

A weighting algorithm for application in the Thru-Reflect-Line (TRL) calibration technique is presented to enhance the accuracy and reliability of vector network analyzer (VNA) measurements over broad frequency bands. The method addresses the inherent limitations of the traditional TRL calibration, particularly the step changes observed in banded-TRL approaches when multiple Line standards are used. By introducing a bespoke weighting function that assigns phase-dependent weights to each Line standard, smoother transitions and improved S-parameter measurements can be achieved. Experimental validation using measurements of both 3.5 mm and Type-N devices demonstrates the effectiveness of the weighted-TRL method in eliminating discontinuities and calibration artifacts across a wide range of frequencies. The results reveal the improved calibration of S-parameters this approach can yield compared to traditional TRL calibration methods. The developed weighted-TRL calibration technique offers a significant advancement in metrology-grade measurements, enabling more precise characterization of high-frequency devices across broad frequency bands. By mitigating a key limitation of the TRL calibration, this method provides a valuable tool for enhancing the accuracy and reliability of VNA measurements for precision metrology applications.

Currently, measurement devices and instruments operating in the microwave range are widespread. Therefore, the problem arises of periodic checks, verifications and calibrations of such devices and instruments. The task of minimizing the systematic measurement error is a key task when performing verification of measuring instruments, measuring systems and devices operating in the microwave range using vector network analyzers. Various methods and models for performing calibrations of a vector network analyzer for determining the scattering parameters of passive microwave devices are described. The analysis of calibration methods is carried out, recommendations for its applications are given.

We describe a method for direct intercomparison of terahertz permittivities at 200 GHz obtained by a Vector Network Analyzer and a Time-Domain Spectrometer, whereby both instruments operate in their customary configurations, i.e., the VNA in waveguide and TDS in free-space. The method employs material that can be inserted into a waveguide for VNA measurements or contained in a cell for TDS measurements. The intercomparison experiments were performed using two materials: petroleum jelly and a mixture of petroleum jelly with carbon powder. The obtained values of complex permittivities were similar within the measurement uncertainty. An intercomparison between VNA and TDS measurements is of importance because the two modalities are customarily employed separately and require different approaches. Since material permittivities can and have been measured using either platform, it is necessary to ascertain that the obtained data is similar in both cases.

This paper begins with a comprehensive review into the existing GaN device models. Secondly, it identifies the need for a more accurate GaN switching model. A simple practical process based on radio frequency techniques using Vector Network Analyser is introduced in this paper as an original contribution. It was applied to extract the impedances of the GaN device to develop an efficient behavioural model. The switching behaviour of the model was validated using both simulation and real time double pulse test experiments at 500 V, 15 A conditions. The proposed model is much easier for power designers to handle, without the need for knowledge about the physics or geometry of the device. The proposed model for Transphorm GaN HEMT was found to be 95.2% more accurate when compared to the existing LT-Spice manufacturer model. This work additionally highlights the need to adopt established RF techniques into power electronics to reduce the learning curve while dealing with these novel high-speed switching devices.

The complex permittivity spectra of binary mixtures (0.0 → 1.0) of n-octanol and N,N-dimethylformamide (DMF) were obtained in the lower microwave radiation region using a vector network analyzer (VNA) at 293.15 K The complex permittivity spectra of n-octanol with DMF and binary mixtures were fitted in a dielectric relaxation model (Havriliak–Negami) to obtain the static dielectric constant (ε0) and relaxation time (τ). Complex nonlinear least-squares (CNLS) fitting was used to fit the complex dielectric spectra. The nonlinear variation in ε0 and τ against DMF concentration in binary mixtures of n-octanol + DMF indicated hetero-molecular interaction between participating molecular species. The variation in the dielectric constant and dielectric loss against concentration is discussed in light of their dependence on frequency. The microwave radiation heating parameters including power reflected (pr), power transmitted (pt), and penetration depth (dp) were investigated at general purpose and commercial microwave radiation of 2.45 GHz, respectively.

Radio Frequency (RF) power sensor calibration is one of the essential measurements in RF and microwave metrology. For a reliable and accurate power sensor calibration, there are various methods, such as the substitution method, the direct comparison transfer method (DCTM), and the vector network analyzer (VNA)-based calibration method (VBCM). The VBCM is a method that is derived from the DCTM. It is a preferred method since the VNA has a better measurement capability and has fewer connection requirements for measurement devices. In this study, the milestones and potential application errors of the VBCM are given by considering the connection mistakes, measurement faults, calculation errors, and control software coding problems. At the end of the power sensor calibration measurements with the VBCM, the model function components and the uncertainty calculation examples according to the GUM Bayesian method are also presented in this study. In addition, the advantages and disadvantages of the VBCM compared to the former methods are discussed in this study.

Structural, dielectric and electromagnetic properties of spinel ferrites Ni1 − xZnxFe2O4 have been reported in this study. Zinc substituted nickel ferrites Ni1 − xZnxFe2O4 (x = 0 to 1, Δx = 0.2) have been prepared with the sol gel citrate route with final sintering temperature of 1000°C for 8 h. The structural parameters of these ferrites are measured with the help of x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy and Raman spectroscopy. The dielectric properties of the prepared ferrites have been measured with the help of an impedance analyzer and analyzed as a function of frequency in the MHz frequency range. The electromagnetic properties of these Ni-Zn ferrites in the X-band frequencies (8.2–12.4 GHz) have been obtained from the vector network analyzer (VNA) data. A study of reflection loss (RL) revealed that a minimum RL of − 17.54 dB is achieved at 9.62 GHz with matching thickness of 3.5 mm and absorption bandwidth of 3.108 GHz.

The preparation and complex permittivity and permeability measurement of a new U-type of hexaferrite microwave absorbing material (Ba4 Mg2 − x MnxFe36 O60) is reported for different value of x in range 0 ≤ x ≤ 2. Complex permittivity and permeability values of hexaferrite pellets are measured using a vector network analyser (VNA) in X-band. The reflection loss of the materials is computed for different values of x and thickness using the measured permittivity and permeability values. The optimum reflection loss is found to be −43 dB for hexaferrite pellet (x = 0.5) at a thickness of t = 1.7 mm. Microwave absorbing paint pellets are prepared by mixing hexaferrite powder with polyimide solution and their complex permeability and permittivity are also measured using a VNA. Using these measured values, radar cross-section reduction simulation for artillery shells has been carried out using electromagnetic simulation software in the 8–10 GHz frequency range. A maximum radar cross-section reduction of 15 dB has been observed for a 30 mm artillery shell at 9 GHz.

In this paper, by combining the error network mapping model with the pseudo cascading relationship, the line-reflect-reflect-match (LRRM) calibration of a vector network analyzer (VNA) is reformulated in a novel and simple way. Based on the error network mapping model in the hybrid parameter representation, the raw measured waves are mapped to the equivalent voltages and currents at the test ports. To describe the mapping relationship, the hybrid parameter matrix is constructed by measurement of the thru standard, and only three calibration coefficients, namely x, y, and z, are required to be solved for the VNA calibration. Meanwhile, when measuring the double one-port standard, the pseudo cascading relationship is defined and used to establish the calibration equation in the form of matrix multiplication. By this means, an eigenvalue problem similar to that in thru-reflect-line (TRL) calibration is derived after a series of simple matrix operations. Solving the eigenvalue problem enables the calibration coefficients x and y to be calculated in a convenient manner. Then, by utilizing the lumped models of partial calibration standards, the last calibration coefficient z is determined. Once all three calibration coefficients are obtained, the LRRM calibration is completed. Finally, on-wafer experiments are performed to verify the formulated LRRM calibration.