S-parameter Values Research Articles

A Power Combiner–Splitter Based on a Rat-Race Coupler for an IQ Mixer in Synthetic Aperture Radar Applications

Synthetic aperture radar (SAR) is a powerful tool in remote sensing applications that can produce high-resolution images and operate in any weather condition. It is composed of many RF components, such as the IQ mixer, which mixes the base chirp signal (IF) with the carrier signal (LO) and increases the bandwidth of the transmitted signal to twice the maximum frequency of the base chirp signal, reducing the workload of Programmable Field Gate Arrays (FPGA) and increasing the resolution of the SAR system. This research proposes a power combiner–splitter design that will be used as a supporting component to construct the IQ mixer in SAR applications based on a rat-race coupler. The measurement results show that the coupler has good S-parameter values. S11, S22, and S33 have a low reflection value below −17 dB, S13 has a high isolation value below −22 dB, and S21 and S31 have a low attenuation value below −4 dB with amplitude unbalance below 0.1 dB and phase unbalance below 1∘. The 150 MHz requirement bandwidth for the RF signal is also achieved.

Temperature and frequency dependence of conductivity, density of states, and dielectric permittivity of ternary metal chalcogenide PbSnSe2 flake

The mechanically cleaved flake of ternary metal chalcogenide PbSnSe2 was transferred onto the interdigitated electrodes to form electrical contacts. The temperature dependent (180 K–250 K) electrical properties were then analyzed employing complex impedance spectroscopy from 2 kHz to 2 MHz. A detailed analysis of Nyquist plots proposed the space charge dependent behavior and negative temperature coefficient of PbSnSe2 flake. The AC conductivity followed Jonscher's power law with s-parameter value being less than unity. The values of s-parameter increased with rise in temperature suggesting the presence of non-overlapping small polaron tunneling (NSPT) in the PbSnSe2 flake. From this NSPT model, tunneling distance, hopping energy, and density of states (DOS) were estimated at temperatures from 180 K–250 K. The dielectric permittivity showed dispersion at lower frequencies and the tangent loss was also found to be directly related to temperature. A single semicircular arc in complex modulus analysis showed the dominance of bulk effect in the material.

Microwave Loaded Line Phase Shifter Design for Beam-steering Applications in Adaptive Array Antenna System

In this scholarly work, we present innovative design for Loaded Line Phase Shifter (LLPS) which is tailored for the dynamic requirements of beam-steering adaptive antenna arrays. This phase shifter plays a pivotal role by installing a precise 90o phase shift into the elements of the adaptive array, enabling beam switching in diverse directions. In the absence of the Loaded Line Phase Shifter, the S-Parameter values, specifically S11 and S21, are recorded at 158.88o and -23.72o, respectively. Upon integrating the LLPS into the transmission line, a remarkable transformation occurs with S11 and S21 values transitioning to -143.28o and -53.03o, correspondingly. These results hold great promise for the practical applications of adaptive antenna arrays.

Reconfiguration of Polarized Antennas for WLAN Applications

Wireless technology based on the IEEE 802.11 standard and in accordance with the KEMINFO 2019 regulations requires antennas that can adapt to changing environments. Microstrip antennas are a good solution to meet the current technological advancements because they have several advantages, such as a simple design, lightweight, easy manufacturing, and low cost. When designing a microstrip antenna, bandwidth parameters must be observed. The bandwidth of a microstrip antenna is narrow. In order to work properly, some simple techniques can be used to increase antenna bandwidth. This research proposes a reconfigurable microstrip antenna polarization using a U-slot at a frequency of (2.4– 2.485) GHz for WLAN applications. The proposed antenna reconfiguration utilizes two (2) switching mechanisms that can be turned on and off individually or simultaneously. The results of the simulation showed that Ant. 1 and Ant. 2 have a linear polarization (LP), Ant. 1 has a bandwidth of 85 MHz (2.399 – 2.484) GHz, and Ant.2 has a bandwidth of 87 MHz (2.398– 2.485) GHz, both with S-parameter values ≤-9.54 dB. Then, Ant. 3 has a right circular polarization with a bandwidth value of 124 MHz (2.397 – 2.484) GHz, and Ant. 4 has a left circular polarization with a bandwidth value of 87 MHz (2.398 – 2.485) GHz at the Axial Ratio (AR) limit of ≤ 3 dB.

Scaling behavior of InAlN/GaN HEMTs on silicon for RF applications

Due to the low cost and the scaling capability of Si substrate, InAlN/GaN high-electron-mobility transistors (HEMTs) on silicon substrate have attracted more and more attentions. In this paper, a high-performance 50-nm-gate-length InAlN/GaN HEMT on Si with a high on/off current (Ion/Ioff) ratio of 7.28 × 106, an average subthreshold swing (SS) of 72 mV/dec, a low drain-induced barrier lowing (DIBL) of 88 mV, an off-state three-terminal breakdown voltage (BVds) of 36 V, a current/power gain cutoff frequency (fT/fmax) of 140/215 GHz, and a Johnson’s figure-of-merit (JFOM) of 5.04 THz V is simultaneously demonstrated. The device extrinsic and intrinsic parameters are extracted using equivalent circuit model, which is verified by the good agreement between simulated and measured S-parameter values. Then the scaling behavior of InAlN/GaN HEMTs on Si is predicted using the extracted extrinsic and intrinsic parameters of devices with different gate lengths (Lg). It presents that a fT/fmax of 230/327 GHz can be achieved when Lg scales down to 20 nm with the technology developed in the study, and an improved fT/fmax of 320/535 GHz can be achieved on a 20-nm-gate-length InAlN/GaN HEMT with regrown ohmic contact technology and 30% decreased parasitic capacitance. This study confirms the feasibility of further improvement of InAlN/GaN HEMTs on Si for RF applications.

Preparation and Thickness Optimization of Graphenic-Based Carbon Material as a Microwave Absorber

The purpose of this study is to optimize the thickness of a layered graphenic-based carbon compound, which is a non-magnetic material derived from biomass (old coconut shell). After the sample was exfoliated using HCl solution, the morphological structure showed that the material used in this study is a reduced graphene oxide (rGO), similar to carbon but with a thickness of less than 10 nm and lateral size in submicron (100 nm). The sample with a 2 mm thickness was then characterized using a vector network analyzer (VNA) to measure its reflection loss (RL). The measurement result is evaluated by converting the S-parameter values (S11 and S21) from the VNA using the Nicolsson Ross Weir (NRW) method to obtain input variables such as relative complex permeability and relative complex permittivity. Following this, the single-layer thickness of the sample was optimized using a genetic algorithm (GA), which can predict the appropriate thickness so that the optimum RL can be obtained. The optimum thickness of the sample was found to be 3.48 mm, which resulted in a much higher RL. The RL was re-measured for verification using a sample with the corresponding optimized thickness, revealing that this optimization is feasibly operational for a radar absorbing material (RAM) design.
 HIGHLIGHTS
 
 Carbon compounds containing graphenic phase derived from coconut shell are functional materials having various unique properties such as superior electrical conductivity, large surface area, and excellent structural flexibility, and microwave absorbtion
 The single-layer microwave absorber employing carbon compounds has been prepared
 The layer thickness optimized using a genetic algorithm (GA) can estimate the appropriate design with the maximum reflection loss (RL)

Evaluation of the temperature dependence of dielectric properties using probe-backside reflection method at millimeter-wave frequencies

In this study, we demonstrate the temperature dependence of the dielectric properties of Al2O3 and Ba2Ti9O20 ceramics, using a probe-backside reflection (PBR) method, at frequencies range up to 320 GHz. The impact of transmission loss on the dielectric properties was first eliminated from the measured S-parameter values using the original S-parameter values of a transmission line. Although the temperature coefficient of dielectric permittivity was uncertain owing to limitations in the measurement repeatability of the PBR method, those of loss tangents of Al2O3 and Ba2Ti9O20 ceramics were calculated as 2.8 × 10−5 K−1 and 1.1 × 10−4 K−1, respectively, for frequencies up to 125 GHz. Furthermore, the temperature coefficient of the dielectric permittivity of Al2O3 was calculated as 691 ppm K−1 at 255 GHz, while those of the dielectric loss tangent at 235 GHz and 275 GHz was calculated as 1.2 × 10−5 K−1 and 1.5 × 10−5 K−1, respectively.

Thickness optimization of a double-layered microwave absorber combining magnetic and dielectric particles

The purpose of this study is to optimize the thickness of the double-layered microwave absorber for obtaining the highest absorption. The graphenic-based carbon compounds and Fe3O4 magnetic particles were combined to fabricate the double-layered absorber. The thickness was optimized by employing a genetic algorithm (GA) to obtain high reflection loss values. These samples at a thickness of 2 mm were measured for reflection loss (RL) with a Vector Network Analyzer (VNA). Input variables, such as relatively complex permeability and relatively complex permittivity, were obtained using a conversion program that uses Nicolson-Ross-Weir (NRW) method from VNA S-parameter values (S11 and S21) data. By entering the permeability and permittivity of the complex relative to GA, the thickness can be optimized to produce high value. Optimization of the double-layer thickness of 12 absorbers produces the optimum thickness of = 5.99 mm and = 0.87 mm among the materials combination, which results in a high (−44.69 dB). This optimization is very important for designing double-layer radar absorbing material (RAM) which results in high values.

Design and fabrication of a 6dB compact directional coupler

In this paper, we will present a planar geometry design for a 6dB compact microwave coupler, and will further explore and discuss the results of an electromagnetic simulation in Sonnet® Suites™ Electromagnetic simulation software. Being a compact coupler, the device features a minute circuit footprint size, while still observing the limitations of the production technologies involved in manufacturing it. The technology utilized in the paper is a 4 port microstrip copper trace on a production-friendly and extremely economical FR4 dielectric substrate. The circuit shows excellent performance in a 1.8GHz bandwidth (3.9GHz – 5.7GHz), with a loss of 6dB on the coupled port. A further advantage of this geometry is a very linear and predictable change in the S-parameter values as a result of small linear changes in the geometry

Positron Annihilation Spectroscopy of Basaltic Rocks from Plio-Qaternary Volcanics, Sana’a-Amran Volcanic Field, Yemen

We focus a new application of positron annihilation lifetime spectroscopy and Doppler broadening techniques at the annihilation sites have been applied on some basaltic rocks from inactive volcano related to Sana’a-Amrana volcanic Field (SAVF). A brief geologic set up and the main petrographic signature of this inactive volcano are given. To gain an insight into geological environment, open nanospaces in the well-characterized basaltic rocks were investigated by positron annihilation spectroscopy. The analysis of the lifetime spectra yielded two lifetime components. The olivine basalt samples contain less mono- vacancies than those found in the trachybasalt and vesicular basalt samples. The overall defect (vacancy) concentration and its variation in the samples were estimated using the mean positron lifetime (τm). The Doppler broadening parameters (S and W-Parameters) were measured. A little variation of the S-parameter values has been observed for all the studied samples indicating that the valance electron contribution to annihilation is not significant.

Microstrip Antenna Design with Patch Rectanguler for Primary Surveillance Radar (PSR) L-Band Application

This research aims to design an inexpensive primary surveillance radar (PSR) antenna with high efficiency and works on the L-Band frequency by using a microstrip antenna, this antenna has advantages in terms of ease of design, light weight and low production prices. The design of the antenna design is made in a simulation that works at a frequency of 1.3 GHz, the substrate material is made of Fr-4 which has a dielectric constant value (er) of 4.3, while the patch material is made of copper. The antenna has a patch size of 71 x 54 mm array 2x1, while the size of the ground plane is 222 x 124.8 mm. Antenna performance testing is done by looking at S-Parameter simulation and voltage standing wave ratio (VSWR). To get an accurate value at a frequency of 1.3 GHz, the sweep method is applied to the patch by changing the width and length of the patch. From the simulation results we get the S-Parameter value right at the frequency of 1.3 GHz with a return loss value of -35 dB while the value of VSWR of 1.29 indicates the antenna has a high efficiency. This research aims to create an antenna innovation that is based on inexpensive and has high efficiency.

Comparing Mutual Coupling of Ring Metamaterial on Square and Vivaldi Array Antennas

The antenna performance is seen from the S-parameter value. The S-parameter graph can be seen as the return loss (S11, S22) and the mutual coupling (S21, S12) value. This research focuses on analyzing mutual coupling on Square and Vivaldi array antennas using the ring metamaterial method. The value of mutual coupling is considered very important to analyze because it affects the performance of the antenna in which is arranged in an array. The simulation results of the mutual coupling value obtained on a square array antenna use a ring metamaterial is -17 dB at a frequency of 2.4 GHz. Meanwhile, the Vivaldi array antenna uses a ring metamaterial that produces a mutual coupling value of -13.840744 dB at a frequency of 3.0162 GHz. The factors that affect the square array antenna so that it becomes the best to suppress the mutual coupling value between antenna elements are a selection of metamaterial shape and proper placement between the antenna array elements is arranged horizontally.

Characterization of Novel Structures Consisting of Micron-Sized Conductive Particles That Respond to Static Magnetic Field Lines for 4G/5G (Sub-6 GHz) Reconfigurable Antennas

Controlling Radio Frequency (RF) signals through switching technology is of interest to designers of modern wireless platforms such as Advanced Wireless services (AWS) from 2.18 GHz–2.2 GHz, mid-bands of sub-6 GHz 5G (2.5 GHz and 3.5 GHz), and 4G bands around 600 MHz/700 MHz, 1.7 GHz/2.1 GHz/2.3 GHz/2.5 GHz. This is because certain layout efficiencies can be achieved if suitable components are chosen to control these signals. The objective of this paper is to present a new model of an RF switch denoted as a Magnetostatic Responsive Structure (MRS) for achieving reconfigurable operation in 4G/5G antennas. In particular, the ABCD matrices of the MRS are derived from the S-parameter values and shown to be a good model from 100 kHz to 3.5 GHz. Furthermore, an overall agreement between simulations, analytical results, and circuit model values are shown.

Development of an Accurate Resonant Frequency Controlled Wire Ultrasound Surgical Instrument.

Our developed wire ultrasound surgical instrument comprises a bolt-clamped Langevin ultrasonic transducer (BLUT) fabricated by PMN-PZT single crystal material due to high mechanical quality factor and electromechanical coupling coefficient, a waveguide in the handheld instrument, and a generator instrument. To ensure high performance of wire ultrasound surgical instruments, the BLUT should vibrate at an accurate frequency because the BLUT’s frequency influences hemostasis and the effects of incisions on blood vessels and tissues. Therefore, we implemented a BLUT with a waveguide in the handheld instrument using a developed assembly jig process with impedance and network analyzers that can accurately control the compression force using a digital torque wrench. A generator instrument having a main control circuit with a low error rate, that is, an output frequency error rate within ±0.5% and an output voltage error rate within ±1.6%, was developed to generate the accurate frequency of the BLUT in the handheld instrument. In addition, a matching circuit between the BLUT and generator instrument with a network analyzer was developed to transfer displacement vibration efficiently from the handheld instrument to the end of the waveguide. Using the matching circuit, the measured S-parameter value of the generator instrument using a network analyzer was −24.3 dB at the resonant frequency. Thus, our proposed scheme can improve the vibration amplitude and accuracy of frequency control of the wire ultrasound surgical instrument due to developed PMN-PZT material and assembly jig process.

Rancang Bangun Filter Bandpass Mikrostrip Pita Sangat Lebar Berbasis Defected Ground Structure (Design of Ultra Wideband Microstrip Bandpass Filter Based on Defected Ground Structure)

Along with the rapid development of technology, many techniques have been employed to improve filter performance by using microstrip, one of them is using a Defected Ground Structure (DGS) technique. The DGS is a technique implemented by combining various forms of slot on the groundplane of filter. This paper presents an ultra wideband (UWB) filter designed using DGS technique by combining two kind of slots on the groundplane, i.e., rectangular slot and rectangular ring slot. The design of composed filter is initialized using filter without DGS, then by adding two kinds of DGS on the groundplane. The DGS is used to improve S-parameter values and increase bandwidth. The method of filter design is using several parametric studies, such as changing the length of patch, width of patch, number of rectangular slot, length of rectangular slot, width of rectangular slot, and gap in rectangular ring slot. This filter is fabricated on a FR4 epoxy dielectric substrate with the thickness of 0.8 mm and the size of 27.4 mm x 22 mm. The measurement result shows that the filter could produce the working bandwidth of 4.01 GHz in the frequency range from 1.52 GHz to 5.53 GHz.

Perancangan dan Analisis Antena Dipole Pada Frekuensi 2,4 GHz Untuk Modul Xbee S2 Pro Menggunakan HFFS 14.0

Xbee s2 pro module works at 2,4 Ghz using IEEE 802.15.4 standard and polarization are linear. There are many types of antennas that can be used, which one is the dipole antenna. The simulation model implemented in this study uses Ansoft HFSS 14.0 software. HFSS stands for high frequency structure simulator is a pioneer in the use of finite element method for electromagnetic wave simulators that implement tangential vector finite elements, adaptive meshing and Adaptive Lanczos-Pade Sweep (ALPS) technology. By using HFSS 14.0 simulation, the axial ratio value of 35.0359 dB that means linier polarization. For the value of s-parameter -21,1851 db and VSWR value approaches 1, that is 1.5195 db. The gain value obtained is 0.7469 dB, the gain value needs to be optimized by using a metamaterial to get a good gain.

Investigation of the free volume characteristics of PEO based solid state polymer electrolyte by means of positron annihilation spectroscopy

Ion conduction in poly (ethylene oxide), PEO, based electrolytes are explained considering the ion movement coupled with polymer segmental motions or free volume. Herein, we describe the application of positron annihilation spectroscopy to investigate the free volume structure of PEO-LiTFSI solid state electrolyte with varying electrolyte concentration. Addition of LiTFSI indicates plasticization effect through the increase in free volume size of polymer matrix. Depth dependent Doppler broadening measurements have shown a decrease in positron/positronium diffusion length and S-parameter value on addition of electrolyte. The observed decrease in S-parameter and positronium intensity could not be ascribed to positronium reaction (inhibition) with dissociated ions or salt aggregates as the variation does not follow the established inhibition expression. The SW correlation curves indicate that the chemical environment at positron/positronium annihilation sites in PEO-LiTFSI is similar to pristine PEO. It again confirms that reduction in positronium intensity and S-parameter cannot be attributed to positronium inhibition. The present study shows that resultant positron/positronium annihilation parameters can be directly attributed to the change in molecular packing or free volume structure of the solid state electrolytes.

Optimization of the geometry of a charge plasma double-gate junctionless transistor for improved RF stability

The radiofrequency (RF) stability of a charge plasma double-gate junctionless transistor (DG-CPJLT) is reported based on the stability factor (K) obtained from the Y-parameters of the device. The impact of variation of geometrical parameters, voltage biases, temperature, and interface traps on the stability of the DG-CPJLT is studied. Based on the results, an optimized DG-CPJLT device is designed and its RF figures of merit obtained. S-parameter values are also computed to study the high-frequency behavior of the device. Moreover, parameters for evaluation of the linearity, such as the third-order transconductance coefficient (gm3) and third-order voltage intercept point (VIP3), are also obtained for the optimized device. It is found that the DG-CPJLT shows significantly improved stability without affecting the RF figures of merit.

Temperature Sensitive Conductivity Studies of NBT-Based Lead-Free Ternary System

The frequency and temperature dependence electrical conduction characteristics of a lead-free 0.78NBT-0.2ST-0.02BT ternary system were investigated by impedance spectroscopy. Variation of real part of conductivity with frequency reveals a frequency independent and a dispersive region obeying Jonscher power law. The relatively higher values of S-parameter in the mid temperature range envisage the presence of localized relaxation or hopping of the charge carriers. The activation energies calculated from the temperature dependent hopping frequency and dc conductivity, portray the increase of unsuccessful hops of the charge carriers with increase in temperature according to the Jump relaxation model. Interestingly the conductivity values could be curbed by introduction of BT in to NBT-ST. The collapsing of the scaled conductivity spectrum in to a single master curve depicts the temperature independent conduction relaxation mechanism.

Positron annihilation spectroscopy studies of bronze exposed to sandblasting at different pressure

An application of Doppler broadening of annihilation line spectroscopy to samples of beryllium bronze DIN-CuBe2 exposed to sandblasting is presented in performed studies. It is familiar that sandblasting introduces open-volume defects. Samples were sandblasted under different pressure for 1 minute using 110 μm particles of Al2O3. For a non-defected sample the constant value of S-parameter was detected. In the cases of sandblasted samples, S-parameter decreased when the depth enhanced. In our studies the thicknesses of defected zones were determined (it was c.a. 30 μm for a sample blasted under pressure of 1 bar and 110 μm – for 5 bar), and it was also observed that if sandblasting pressure is higher the defected zone is larger.