Vector Network Analyzer Measurements Research Articles

Application of Weighting Algorithm for Enhanced Broadband Vector Network Analyzer Measurements

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.

La:ZnO nanoparticles: an investigation on structural, optical, and microwave properties

This paper presents the utilization of ethylene glycol monomethyl ether (EGME) during the synthesis of ZnO and La:ZnO with two tasks as a solvent and a fuel source within the gel combustion technique. The use of EGME for this purpose provides one-step production of the nanoparticles (NPs) and saves a considerable amount of time. The detailed characterization of the nanoparticles was carried out by X-ray diffractometer (XRD), scanning electron microscope (SEM), particle size analyzer, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and Vector Network Analyzer (VNA) measurements, respectively. The NPs exhibited a hexagonal wurtzite structure with good crystallinity and a porous spongy morphology. The photoluminescence emission maxima of the synthesized NPs appeared at 500, 560, and 676 nm, upon excitation by the 372 nm of excitation. La:ZnO NPs showed significantly better photoluminescent characteristics than La-free ZnO forms. When excited at the same wavelength, La-free ZnO, 3%, and 7% La:ZnO exhibited 92, 45, and 35 μs average decay times, respectively. Finally, the microwave properties of the relative complex permittivity and permeability characteristics were also investigated and discussed in detail, which were derived from the scattering parameters of S11 and S21 in the X band regime.

Microwave-Assisted Hydrothermal Synthesis of Nanosheet Layered Hexagonal Spinel Ferrites for Efficient Electromagnetic Wave Absorbing.

A microwave-induced combustion method has been utilized to prepare nanosized powders of hexagonal spinel ferrites using urea and glycine as fuel. The structural and electromagnetic absorption of these products was investigated using X-ray diffraction (XRD). From the (3,1,1) and (1013) peaks in XRD measurements, it was seen that the samples we synthesized were nanosized spinel and y-phase hexagonal ferrite. In addition, Fourier-transform infrared measurements showed that the synthesized samples had high absorption values showing Fe-O, which is between 878 to 4000 cm-1, and metal-oxygen transitions, which are between the 700 and 2500-3000 cm-1 in the spinel and hexagonal phases. From the scanning electron microscope image of the particles, it is seen that they are homogeneous, filled structures with ∼35-40 nm. It appears from vector network analyzer measurements that the synthesized 1.5 mm thick composite materials have very high electromagnetic absorption properties and that these composites can also be used in electromagnetic interference, Wi-Fi applications, and health.

Calibration Error in 21-Centimeter Global Spectrum Experiment

The redshifted 21 cm line signal is a powerful probe of the cosmic dawn and the epoch of reionization. The global spectrum can potentially be detected with a single antenna and spectrometer. However, this measurement requires an extremely accurate calibration of the instrument to facilitate the separation of the 21 cm signal from the much brighter foregrounds and possible variations in the instrument response. Understanding how the measurement errors propagate in a realistic instrument system and affect system calibration is the focus of this work. We simulate a 21 cm global spectrum observation based on the noise wave calibration scheme. We focus on how measurement errors in reflection coefficients affect the noise temperature and how typical errors impact the recovery of the 21 cm signal, especially in the frequency domain. Results show that for our example set up, a typical vector network analyzer (VNA) measurement error in the magnitude of the reflection coefficients of the antenna, receiver, and open cable, which are 0.001, 0.001, and 0.002 (linear), respectively, would result in a 200 mK deviation on the detected signal, and a typical measurement error of 0.48°, 0.78°, or 0.15° in the respective phases would cause a 40 mK deviation. The VNA measurement error can greatly affect the result of a 21 cm global spectrum experiment using this calibration technique, and such a feature could be mistaken for or be combined with the 21 cm signal.

Synthesis and Characterization of Hematite Fe2O3 Nanofiller for Enhanced Dielectric and Microwave-Absorbing Properties in PTFE Composites

This paper presents the synthesis of hematite Fe2O3 nanofiller from mill scales and its application in polytetrafluoroethylene (PTFE) composites for enhanced dielectric and microwave-absorbing properties. The nanofiller was obtained through 9 hours of high-energy ball milling, resulting in a particle size reduction 43.6 to 11.05 nm. The PTFE/Fe2O3 composites were fabricated by dispersing different concentration of Fe2O3 nanofillers using the dry powder processing technique. The structural and morphological characterization of the nanofiller and PTFE/Fe2O3 composites was carried out using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. The composites’ microwave absorption properties were analyzed utilizing vector network analyzer (VNA) measurements in the 8–12 GHz frequency range. Based on the findings from the results, as the percentage of filler increased from 5 to 15%wt, the composites' loss tangent and dielectric constant increased from 0.0272 to 0.0478 and 2.12 to 3.25, respectively, while their reduced signal transmission speed was between 2.21 and 2.07 x 108 m/s at 8 GHz and from 2.24 to 2.11 x 108 m/s at 12 GHz. These findings demonstrate that Fe2O3 nanoparticles are a suitable material for developing microwave-absorbing polymer composites within the 8–12 GHz frequency range.

Phantom evaluation of electrical conductivity mapping by MRI: Comparison to vector network analyzer measurements and spatial resolution assessment.

To evaluate the performance of various MR electrical properties tomography (MR-EPT) methods at 3 T in terms of absolute quantification and spatial resolution limit for electrical conductivity. Absolute quantification as well as spatial resolution performance were evaluated on homogeneous phantoms and a phantom with holes of different sizes, respectively. Ground-truth conductivities were measured with an open-ended coaxial probe connected to a vector network analyzer (VNA). Four widely used MR-EPT reconstruction methods were investigated: phase-based Helmholtz (PB), phase-based convection-reaction (PB-cr), image-based (IB), and generalized-image-based (GIB). These methods were compared using the same complex images from a 1 mm-isotropic UTE sequence. Alternative transceive phase acquisition sequences were also compared in PB and PB-cr. In large homogeneous phantoms, all methods showed a strong correlation with ground truth conductivities (r > 0.99); however, GIB was the best in terms of accuracy, spatial uniformity, and robustness to boundary artifacts. In the resolution phantom, the normalized root-mean-squared error of all methods grew rapidly (>0.40) when the hole size was below 10 mm, with simplified methods (PB and IB), or below 5 mm, with generalized methods (PB-cr and GIB). VNA measurements are essential to assess the accuracy of MR-EPT. In this study, all tested MR-EPT methods correlated strongly with the VNA measurements. The UTE sequence is recommended for MR-EPT, with the GIB method providing good accuracy for structures down to 5 mm. Structures below 5 mm may still be detected in the conductivity maps, but with significantly lower accuracy.

Design, Simulation, and Fabrication of a 500 kV Ultrawideband Coaxial Matched Load and Its Connectors for Fast Transient Pulse Measurement Systems

In the past few decades, Pulsed Power (PP) has been one of the fastest growing technologies, with more and more systems frequently emerging in domains such as civil, medical and military. These systems are based on high-voltage pulses, up to several hundreds of kilovolts, with temporal parameters ranging from microsecond levels to sub-nanosecond levels. One of the biggest challenges in this technology is the accurate and precise measurement of the generated PP. The PP measurement systems must possess high-voltage and wideband properties simultaneously, which is often conflicting. The central elements of a PP measurement system are a voltage divider and a termination load. The work presented in this article is dedicated to the second element of the PP measurement system. This paper describes the development of a 50 Ω coaxial termination load and its connectors for a high power ultrawideband (UWB) pulse measurement systems. The principle roles of these devices are to serve as a dummy matched load for the former and to facilitate the connections between different components of the pulse measurement system for the latter. These devices are designed to withstand pulse voltage amplitudes at least up to 500 kV with temporal parameters, such as rise time and pulse duration, varying from nanosecond to sub-nanosecond ranges. The main challenge in the development of a high-voltage UWB termination load is the tradeoff between the high-voltage and wideband characteristics, both of them requiring opposite dimensional aspects for the load device. This challenge is overcame by the special exponential geometry of the load device. The design employs a 30 cm long low-inductance tubular ceramic 50 Ω resistor, enclosed in a critically dimensioned shielding conductor of an exponential inner profile. This shrinking coaxial structure makes it possible to maintain a good level of matching all along the 50 Ω load. The results obtained through 3D electromagnetic modeling and vector network analyzer measurements show good agreement and confirm the reflection coefficient below −27 dB up to at least 2.5 GHz for the load device. Moreover, calculations demonstrate that the load device is very well adapted for nanosecond and sub-nanosecond pulses with voltage peaks as high as 500 kV. These results demonstrate the high-voltage and UWB properties of the developed load device and prove the utilization of this device in the measurement systems for the accurate and precise measurements of the PP.

Synthesis and characterization of Ba0.6Ca0.4Fe12O19/Fe3O4/SiO2 nanocomposite

This research synthesized two types of materials, namely M-type barium hexaferrite Ba0.6Ca0.4Fe12O19 and Ba0.6Ca0.4Fe12O19/Fe3O4/SiO2 nano composite by using ceramic and mechanical milling method. To characterize obtained powder properties, we employed permagraph and vector network analyser (VNA) measurement. Furthermore, complex permeability (μ) and permittivity (ε) were calculated based on VNA measurement signal in The samples have shown a lowest reflection loss of –40.43 dB at 8.46 GHz and –21.14 dB dB at 12.4 GHz for barium hexaferrite Ba0.6Ca0.4Fe12O19 (0%) and Ba0.6Ca0.4Fe12O19/Fe3O4/SiO2 (20%) nano composite, respectively.

Analysis of Acid Diffusion Effects on Physical Properties of Polymer Composites: A Combined Study of Mechanical and Electrical Characterization

In this study, we examined the impact of carbon nanotube (CNT) concentration on the mechanical properties of epoxy/CNT composites under acid exposure. Samples with varying CNT concentrations (0% to 5%) were fabricated and characterized using dynamic mechanical analysis (DMA) and nanoindentation. Beyond the percolation threshold, the composites experienced decreased bulk mechanical properties due to CNT agglomeration. Acid exposure for one week and one month revealed a gradient of properties from the sample’s skin to its core. Overall, the composites exhibited modified physical properties, with degradation influenced by the CNT concentration. Higher concentrations acted as barriers but also created pathways for acid diffusion through pores surrounding CNT agglomerates. The agreement between nanoindentation and vector network analyzer (VNA) measurements further supported our findings. This convergence of mechanical and electromagnetic characterization techniques holds promise for wireless structural health monitoring (SHM) applications. Our study enhances the understanding of epoxy/CNT composites for SHM applications. The relationship between CNT concentration, acid exposure, and mechanical properties guides material selection and the development of real-time damage-detection techniques. Integrating multiple measurement techniques, as demonstrated by the agreement between nanoindentation and VNA data, provides a comprehensive understanding of structural behavior, improving SHM practices.

Synthesis, structural, and microwave absorption properties of hematite (α-Fe2O3) and maghemite (γ-Fe2O3)

This work demonstrated the synthesis, structural, and microwave absorption properties of hematite (α-Fe2O3) and maghemite (γ-Fe2O3) nanopowders. The desired samples are successfully synthesized from the natural ironstone of Indonesia by using the coprecipitation method. The variations of acidic environments during the synthesis process (i.e., pH 6 and 7) were done to obtain the maghemite and hematite phases. The combination of x-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements was used to investigate the crystal and microstructure, respectively. Meanwhile, the vector network analyzer (VNA) was performed to examine the microwave absorption properties at x-band frequency. The structural measurements of the samples confirmed the formation of single-phase maghemite and hematite phases for precipitation pH 6 and 7, respectively, which showed the change in morphology after the precipitation process and sphere-like agglomerated particles of samples. The results Debye–Scherrer equation indicates that the crystal size of precipitated samples is on the order of nanometers. The microwave absorption characteristics through VNA measurements showed enhanced microwave absorption properties after the precipitation process; the RL max of natural ironstone increased from −4.39 dB to −10,99 and −11,72 dB for S6 and S7 samples, respectively. Generally, the hematite and maghemite reveal the same pattern of absorption peaks. The RL max of natural ironstone, S6, and S7 samples were observed at 10.52, 11.04, and 11,06 GHz, respectively. These results revealed that the variation of acidic environments during the synthesis process influenced the structure and microwave absorption.

A compact triband antenna using artificial magnetic conductor for wireless body area network communicationsFront

The proliferation of the Internet of Things devices and advancements in wireless communication have fostered the growth of Wireless Body Area Networks (WBAN). This research provides a triband antenna supported by a 4 × 4 Artificial Magnetic Conductor (AMC) array surface that has a low Specific Absorption Rate (SAR), a high Front to Back Ratio (FBR), and increased gain for use in wearable devices. For WBAN communications, the proposed antenna operates in the Industrial, Scientific, and Medical (2.4 GHz) band, the C (3.7–4.2 GHz), and the Wi-Fi 6E (5.925–7.125 GHz) bands. The dual-band AMC unit cell exhibits Double-Negative and angular stability behaviour at 2.45 GHz and 6.5 GHz. AMC-backed antenna achieved multiband functionality by incorporating slots into the unit cell and a defective ground structure into the antenna. The antenna was positioned 0.139λ0 above the AMC surface, which measured 0.556λ0 × 0.556λ0 × 0.013λ0 (at 2.45 GHz). The antenna exhibited good gain and return loss variations when mounted on curved surfaces. The proposed integrated design yielded substantial enhancements, as evidenced by the increase of 8.2 dBi in maximum gain, 25.2 dB in FBR, and over 93% in total efficiency. The AMC-backed antenna’s − 10 dB impedance bandwidth is 18.4%, 21.2%, and 22.3%, with corresponding frequency ranges of 2.25–2.66 GHz, 3.66–4.53 GHz, and 5.9–7.35 GHz. Additionally, the AMC surface showed an average reduction in SAR of 93.22%. Vector Network Analyzer and Anechoic chamber measurements proved simulation accuracy. As a result, it is strongly recommended that the integrated antenna design be acknowledged in WBAN communications.

PANI-coated YIG/CFO hybrid composites as advanced electromagnetic wave absorber through X-band

Polyaniline (PANI)-coated Y3Fe5O12(YIG)/CoFe2O4(CFO) hybrid composites were synthesized via sol-gel and oxidative polymerization methods to achieve advanced microwave absorption properties. The structural, morphological, magnetic, and microwave absorption characteristics of the resulting samples were analyzed by performing X-ray diffraction (XRD), scanning electron microscopy (SEM), vibration sample magnetometer (VSM), and vector network analyzer (VNA). XRD results revealed that CFO and YIG have cubic crystal structures with Fd3m and Ia3d space symmetry, respectively, with an average crystallite size of 35.3 nm and 42.9 nm. The Ferro/ferrimagnetic signals were detected from the ferrite samples' room temperature magnetic hysteresis loops. The incorporation of PANI and YIG into the composites resulted in a decrease in their magnetic saturation (Ms) and coercive field (Hc) values. VNA measurements demonstrated that nearly all samples achieved 90% absorption (≤−10 dB) of incident electromagnetic waves throughout the X-band frequency range. The minimum reflection loss (RLmin) value reaches − 47.34 dB at 8.14 GHz, with an effective bandwidth of 4.00 GHz, covering the entire X-band and beyond. These impressive absorption characteristics suggest that the manufactured composites possess potential as viable candidates for defense applications conducted at X-band frequency.

Comparison of free‐space VNA and TDS measurements using transmission‐type frequency selective surfaces

AbstractA method for directly comparing vector network analyzer (VNA) and time‐domain spectrometer (TDS) measurements in free space using transmission‐type frequency selective surfaces (FSSs) is proposed. The transmission characteristics of FSSs with artificially controlled frequency dispersions facilitate flexible and detailed comparisons of VNA and TDS measurements. Four FSSs were designed as verification devices of free space measurements. The proposed approach was demonstrated in the D and J bands by comparing the measurement results of the transmission amplitude and phase characteristics of the FSSs obtained using VNA and TDS systems. The amplitude and phase results obtained using both systems were in good agreement, confirming the consistency and validity of the VNA and TDS measurements.

Scattering Parameter Measurements of the Long Wavelength Array Antenna and Front End Electronics

We present recent 2-port vector network analyzer (VNA) measurements of the complete set of scattering parameters for the antenna used within the Long Wavelength Array (LWA) and the associated front end electronics (FEEs). Full scattering parameter measurements of the antenna yield not only the reflection coefficient for each polarization, S11 and S22, but also the coupling between polarizations, S12 and S21. These had been previously modeled using simulations, but direct measurements had not been obtained until now. The measurements are used to derive a frequency dependent impedance mismatch factor (IMF) which represents the fraction of power that is passed through the antenna–FEE interface and not reflected due to a mismatch between the impedance of the antenna and the impedance of the FEE. We also present results from a two-antenna experiment where each antenna is hooked up to a separate port on the VNA. This allows for cross–antenna coupling to be measured for all four possible polarization combinations. Finally, we apply the newly measured IMF and FEE forward gain corrections to LWA data to investigate how well they remove instrumental effects.

A Method of Extracting Transmission Characteristics of Interconnects from Near-Field Emissions in PCBs

This paper proposes a method for extracting transmission characteristics of interconnects in printed circuit boards (PCBs) from near-field emission. A wideband microstrip line electric probe is used to measure the near-field emission. There are two key technologies in the extraction principle, obtaining the transfer function and the input signal estimation, and they are explained in detail. To validate the method, one-trace structures, including a corner trace and a via trace, and a multi-trace structure were measured. The transmission characteristics extracted by the proposed method agrees well with the standard vector network analyzer (VNA) measurements up to frequency of 12 GHz. The error caused by the distance and the disturbance signal is investigated.

Characterization of Millimeter-Wave Wideband FMCW Signals Based on a Precisely Synchronized NVNA for Automotive Radar Applications

In this article, a nonlinear vector network analyzer (NVNA) measurement setup is developed to characterize frequency modulated continuous wave (FMCW) signals in the frequency domain. Thanks to the use of precisely synchronized multisine phase reference and pulsed-RF phase calibration standards, such NVNA setup is validated for high-accuracy measurement of wideband FMCW signals at the millimeter-wave test bands. According to the method validation at 24 and 60 GHz with a maximum FMCW bandwidth of 2 GHz, the proposed NVNA setup has lower measurement errors and uncertainties than the commercial real-time oscilloscope (RTO) and vector signal analyzer (VSA), offering a reference standard of test and calibration for automotive radar applications.

Analytical Framework of S-Parameter-Based Efficiency for Secondary-Parallel Compensation WPT System to Authenticate Data Using VNA

Resonant wireless power transfer (R-WPT) is the most efficient system in near-field applications. Predominantly, four distinct resonant topologies exist for R-WPT to enhance the power transfer efficiency (PTE) under different load conditions. Here, the PTE is considered crucial for gauging the R-WPT system performance. In a typical experimental scenario, measurement of the PTE is performed by exciting the transmitter (Tx) coil with a sinusoidal signal using a high-frequency inverter source. Therefore, the input and output power measurements are conducted using an oscilloscope. Here, the measurement using an oscilloscope is highly susceptible to external noise. As an alternative, the vector network analyzer (VNA) is the most accurate instrument to measure <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameters with high precision, even at very high frequencies. The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameter-based analytical expressions for evaluating PTE are available only for series–series compensation topology. Therefore, VNA usage is severely limited for experimental validation of the other compensation topologies. This article proposes an analytical evaluation of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameter-based PTE for secondary-parallel compensation topology as a contribution. Moreover, the mathematical proof is deduced to determine the active operating load condition for the secondary-parallel capacitor. Error analysis of experimental data is performed where the signal-to-noise ratio (SNR) of the measurement system is greater than 35 dB and the percentage error rate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\epsilon $ </tex-math></inline-formula> is less than 1.3%, which implies high precision and accuracy of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> -parameter-based VNA measurement system.

Theory and measurement of the single and hybrid-mode excitation and evolution in a lossy-dielectric-loaded waveguide

ABSTRACT This paper investigates the mode excited, evolved, and propagating properties of the lossy dielectric-loaded waveguide (DLW) used in a Ku-band TE11-mode gyrotron traveling wave tube (gyro-TWT). Theoretical calculation and numerical simulation show that different DLW eigenmodes can be excited by the hollow circular waveguide as a single or hybrid-mode. This study clearly reveals the transformation conditions of the single and hybrid-mode, and the mechanism of the resulting specific dispersion, loss, and electromagnetic field distribution. According to the mode excitation principle and its evolution laws, the propagating properties can be accurately controlled by adjusting the dielectric thickness, which can effectively suppress the potential oscillations and improve the electron bunching phase in the gyro-TWT. As a result, the dielectric loading scheme can be optimized by properly arranging the DLWs, thus enhancing the stability and gain of the gyro-TWT. The theory and simulation are verified by the vector network analyzer measurement at Ku-band, and the results show a good agreement.

Measurement and Analysis of Vector Network Analyzer

One of the main instrument used in the microwave communication laboratory is analyzer. Particularly, network analyzer, which is used for testing the RF components. Here in this paper the vector network analyzer design study and measurement analysis is discussed. The introduction to Vector Network Analyzer (VNA), working, types, blocks, function, measurements and specifications are presented as revisiting the technologies. As a DUT, a fractal antenna is connected to VNA and its results are presented.

A Novel Bandstop Filter Based on Two-Port Coaxial Cavities for the Installation of Metallic Mode Stirrers in Microwave Ovens

Metallic stirrers are commonly used in mode-stirred reverberation chambers but are less common in microwave ovens, because the use of a metallic axis creates a coaxial port in the cavity wall where the axis is introduced, which may result in significant microwave leakage levels. However, due to electromagnetic, mechanical, temperature, or chemical requirements, metallic axes must be used in some cases. In this paper, we present a high power coaxial filter that enables the use of metallic stirrers in microwave applications. The filter employs two-port coaxial cavities that are analyzed to determine their design parameters. These cavities are coupled via coaxial lines to achieve proper attenuation levels. The cavities were designed using commercial electromagnetic (EM) software, and a filter prototype was validated using vector network analyzer (VNA) measurements. The simulated and measured results show that a three-stage configuration can achieve attenuations greater than 70 dB at the 2.45 GHz ISM band, allowing the use and external handling of the metallic axis inserted into microwave ovens with negligible microwave radiation leakage.