Microwave Design Research Articles

Realization of Modified Elliptical Shaped Dielectric Lens Antenna for X Band Applications with 3D Printing Technology

Placing dielectric lens structures into an antenna's aperture has proven to be one of the most reliable methods of enhancing its gain. However, the selected material and the prototyping method usually limit their fabrication process. With the advances in 3D printing technology and their applications, the microwave designs that were either impractical or impossible in the past to manufacture using traditional methods, are now feasible. Herein, a novel prototyping method by using 3D-printer technology for low-cost, broadband, and high gain dielectric lens designs has been presented. Firstly, the elliptical lens design has been modeled in the 3D EM simulation environment. Then fused deposition modeling based 3D-printing method has been used for the fabrication of the dielectric lens. The measured results of the 3D printed antenna show that the lens antenna has a realized gain of 17 to 20.5 dBi over 8-12 GHz. Moreover, the comparison of the prototyped antenna with its counterpart dielectric lens antenna in the literature has indicated that the proposed method is more efficient, more beneficial, and has a lower cost.

Editorial for the special issue on advances in forward and inverse surrogate modeling for high‐frequency design

Editorial for the special issue on advances in forward and inverse surrogate modeling for <scp>high‐frequency</scp> design

Low‐cost data‐driven modelling of microwave components using domain confinement and PCA‐based dimensionality reduction

Fast data-driven surrogate models can be employed as replacements of computationally demanding full-wave electromagnetic simulations to facilitate the microwave design procedures. Unfortunately, practical application of surrogate modelling is often hindered by the curse of dimensionality and/or considerable nonlinearity of the component characteristics. This paper proposes a simple yet reliable approach to cost-efficient modelling of miniaturized microwave components which adopts two fundamental mechanisms to improve the computational efficiency of setting up the surrogate. Firstly, the model domain is confined-using a set of pre-optimized reference designs-to the region of the parameter space containing high-quality designs with respect to the relevant performance figures. Secondly, the domain is spanned by the selected principal components of the reference set for dimensionality reduction. Consequently, the surrogate model, covering wide ranges of the device parameters and operating conditions, can be established using a fraction of training data samples required by conventional approaches, without compromising its predictive power. The proposed technique is illustrated using two miniaturized microstrip components: a rat-race coupler (RRC) and an impedance matching transformer. The following accuracies of the PCA-based surrogates have been obtained: 0.9% for RRC and 2.1% for the transformer (for 800 training data samples).

Design and analysis of effective graded microwave absorbing material for low observable technology

Compositional designing of effective graded radar absorbing material for low observable technology is always a challengeable task in material science. The micro scale or quantum scale interaction of electromagnetic radiation is depends on the characteristic property of each atom or their assembly in a material composition. The filler and matrix in a composite structure plays a vital role between the advantages in electromagnetic absorption capability and the disadvantage due to difficulties in practical homogenous dispersion with weight concentration. The present work describes synthesis of biomaterial based effective graded radar absorbing material (RAM) for application in stealth technology. Ultrasonic treated rice husk raw material shows a significant increase of dielectric property of the composite material blended with epoxy resin. The significant modification in surface of the biomaterials with ultrasonic wave provides the enhanced mechanical strength as well as hardness of the material. Bio ceramic material composed of china clay and carbon rich waste rice husk ash possesses good dielectric loss for frequency 10 GHz and reflection loss -24.5 dB which is quite significant for stealth technology. Scanning electron microscopy (SEM) study shows good dispersion of rice husk ash in the epoxy matrix. Frequency dependence of both dielectric constant and dielectric loss are measured in the X band frequency range (8.2-12.4GHz). This low cost laboratory scale synthesized RAM find its application in designing of stealth aircraft and jet fighter for military purposes.

Fabrication of core-shell nanoporous carbon@chiral polyschiff base iron(II) composites for high-performance electromagnetic wave attenuationin the low-frequency

A key aspect of refining the design and manufacture of contemporary microwave absorbing materials is to improve their absorption of electromagnetic radiation at low frequency which has proved to be an immensely challenging task. This work reports a relatively uncomplicated method to design core-shell absorbers through nanoporous carbon (NPC) obtained by removing redundant Cu from the pyrolysis products of HKUST-1 (HKUST is the Hong Kong University of Science and Technology) coated with (1R,2R)-(−)-1,2-cyclohexanediamineferrocene formaldehyde polyschiff base iron (II) (CPI). Three NPC@CPI samples not only maintain good impedance matching of the pyrolysis products of HKUST-1, but also increase the attenuation abilities significantly due to the synergetic effect of multiple interfacial polarization, cross-polarization and Debye relaxation, which further leads to their outstanding microwave absorbing performance. When the mass ratio of CPI to NPC is 6.7:100 (NPC@CPI-1), the strongest reflection loss (RL) can achieve −60.8 dB at 3.7 GHz, whereas the RL bandwidth under −10 dB can become as much as 5.6 GHz at 1.65 mm. While CPI to NPC is 10:100 (NPC@CPI-2), an optimal RL of −46.9 dB at 11.7 GHz and 1.9 mm can be achieved. This work thus provides an excellent model for the design and the manufacture of thin, lightweight, broad, and strong EM absorbers based on MOFs derivatives and chiral polymers.

Quantum Computing: An Introduction for Microwave Engineers

During the past decade, quantum computing has grown from a field known mostly for generating scientific papers to one that is poised to reshape computing as we know it [1]. Major industrial research efforts in quantum computing are currently underway at many companies, including IBM [2], Microsoft [3], Google [4], [5], Alibaba [6], and Intel [7], to name a few. The European Union [8], Australia [9], China [10], Japan [11], Canada [12], Russia [13], and the United States [14] are each funding large national research initiatives focused on the quantum information sciences. And, recently, tens of start-up companies have emerged with goals ranging from the development of software for use on quantum computers [15] to the implementation of full-fledged quantum computers (e.g., Rigetti [16], ION-Q [17], Psi-Quantum [18], and so on). However, despite this rapid growth, because quantum computing as a field brings together many different disciplines, there is currently a shortage of engineers who understand both the engineering aspects (e.g., microwave design) and the quantum aspects required to build a quantum computer [19]. The aim of this article is to introduce microwave engineers to quantum computing and demonstrate how the microwave community's expertise could contribute to that field.

Microwave field: Temperature-dependent dielectric properties and heating characteristics during the synthesis of alpha-tellurium dioxide

The temperature-dependent dielectric properties of the precursor can provide theoretical support for microwave synthesis related materials. Herein, temperature-dependent dielectric properties and microwave heating characteristics were researched in detail during the synthesis of alpha-tellurium dioxide (α-TeO2) by a microwave removal of hydrogen from orthotelluric acid (H6TeO6). The results showed that the dielectric constant (εr′) and the dielectric loss (εr″) values of H6TeO6 were divided into six stages due to the evolution of the structure with increasing temperature. And the loss tangent coefficient (tanδ) values had two distinct wave crests: 200–400 °C, and 450–600 °C, which corresponded to maximum tanδ values of 0.044 (F/m) at 350 °C and 0.028 (F/m) at 550 °C, respectively. In addition, TG-DSC, XRD, FT-IR, SEM were employed to track the as-synthesized evolution of structure and morphology during calcination. The results indicated that the fine and uniform α-TeO2 particles could be obtained by the microwave treatment at 600 °C for 10 min. The work not only provides a stable and high-quality precursor for the application of α-TeO2, but also offers theoretical data support for microwave preparation and design of tellurium oxide-based materials.

A 2–20-GHz 10-W High-Efficiency GaN Power Amplifier Using Reactive Matching Technique

In this article, we present the analysis, design, and implementation of a wideband 10-W monolithic microwave integrated circuit power amplifier (PA), fabricated in a low-cost 0.1-μm gallium nitride (GaN) on Si technology. The design is focused on the realization of a low-loss and wideband impedance transformation networks across 2-20 GHz using a reactive matching (RM) technique. The two-stage GaN PA achieves an average output power of 40.1 dBm and a peak output power of 41.6 dBm at 13 GHz, in the CW-mode operation, with a smallsignal gain of S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> > 25.5 dB over the entire bandwidth. The average power-added efficiency (PAE) is 21%, with a peak PAE of 29% at 6 GHz. The PA chip occupies an area of 2.9×2.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . To the best of our knowledge, the PA presented in this work demonstrates the highest broadband gain among the reported GaN-based RMPAs with a corresponding output power of about 10 W.

A Coalesced Kite Shaped Monopole Antenna for UWB Technology

A small and compact monopole antenna of dimensions 25 × 18 × 1.6 mm3 is presented for UWB communications. The proposed design consists of two kite shaped radiators in coalesced form and a tapered slotted ground plane for the UWB characteristics. The parametric study of the patch and the modified ground plane is made and the measured impedance bandwidth of 14.2 GHz (2.8–17 GHz) is achieved. The measured antenna gain varies from 2.28 to 5.0 dBi for the entire frequency band of application. Group delay, signal analysis and antenna isolation |S21| are also studied at different orientations of the antenna and found to be quite satisfactory to meet the requirements for UWB applications. The co- and cross-polarization patterns are also calculated for E and H-planes, and compared with the measured results. Antenna simulation and optimization are performed using CST Microwave Studio and design is fabricated and measured for the validation of the results.

Design of a pilot-scale microwave heated chemical vapor infiltration plant: An innovative approach

A hybrid Microwave-assisted Chemical Vapor Infiltration (MW-CVI) pilot plant to produce silicon carbide-based Ceramic Matrix Composites was designed, built and setup, as a part of the European project HELM. Being different from the existing lab-scale MW-CVI equipment, this pilot plant was designed with the idea of a further industrial scale-up.In order to enable the infiltration of the large samples of interest in industrial applications, the reactor was designed with the internal microwave cavity acting as an overmoded resonator at the frequencies of interest. The designed pilot plant allowed proper microwave heating of cylindrical samples of diameter doubled with respect to typical lab-scale preforms, with reproducible operating conditions in terms of transmitted/reflected power. First infiltration trials resulted in an average reaction efficiency of 25 % with the desired inside-out silicon carbide infiltration. The main steps of the design and the results of the first infiltration tests are discussed in this paper.

Effect of interface magnetization depinning on the frequency shift of ferromagnetic and spin wave resonance in YIG/GGG films**Project supported by the National Natural Science Foundation of China (Grant Nos. 11674187 and 51871127) and Technology on Electronic Test & Measurement Laboratory (Grant No. 6142001180103).

Nowadays the yttrium iron garnet (Y3Fe5O12, YIG) films are widely used in the microwave and spin wave devices due to their low damping constant and long propagation distance for spin waves. However, the performances, especially the frequency stability, are seriously affected by the relaxation of the interface magnetic moments. In this study, the effect of out-of-plane magnetization depinning on the resonance frequency shift (Δfr) was investigated for 3-μm YIG films grown on Gd3Ga5O12 (GGG) (111) substrates by liquid-phase epitaxy. It is revealed that the ferromagnetic resonance (FMR) and spin wave propagation exhibit a very slow relaxation with relaxation time τ even longer than one hour under an out-of-plane external magnetic bias field. The Δfr span of 15.15–24.70 MHz is observed in out-of-plane FMR and forward volume spin waves. Moreover, the Δfr and τ depend on the magnetic field. The Δfr can be attributed to that the magnetic moments break away from the pinning layer at the YIG/GGG interface. The thickness of the pinning layer is estimated to be about 9.48 nm to 15.46 nm according to the frequency shifting. These results indicate that Δfr caused by the pinning layer should be addressed in the design of microwave and spin wave devices, especially in the transverse magnetic components.

A Survey of Differential-Fed Microstrip Bandpass Filters: Recent Techniques and Challenges.

Differentially driven devices represent a highly promising research field for radio frequency (RF), microwave (MW), and millimeter-wave (mmWave) designers and engineers. Designs employing differential signals are essential elements in low-noise fourth-generation (4G) and fifth-generation (5G) communications. Apart from the conventional planar MW components, differential–fed balanced microstrip filters, as promising alternatives, have several advantages, including high common-mode rejection, low unwanted radiation levels, high noise immunity, and wideband harmonic suppression. In this paper, a comprehensive and in-depth review of the existing research on differential-fed microstrip filter designs are presented and discussed with a focus on recent advances in this research and the challenges facing the researchers. A comparison between different design techniques is presented and discussed in detail to provide the researchers with the advantages and disadvantages of each technique that could be of interest to a specific application. Challenges and future developments of balanced microstrip bandpass filters (BPFs) are also presented in this paper. Balanced filters surveyed include recent single-, dual-, tri-, and wide-band BPFs, which employ different design techniques and accomplish different performances for current and future wireless applications.

EU DEMO EC equatorial launcher pre-conceptual performance studies

The preliminary conceptual design for the Electron Cyclotron (EC) system of the future European DEMOnstration fusion power plant is ongoing in the EUROfusion Consortium. This represents one of the key aspects in order to assess the performances and the integration capabilities of such a system in EU DEMO as well as in the alternative reactor configuration Flexi-DEMO. Different options for the antenna, namely remote steering antenna (RSA), open ended waveguides (OEWG) and the front steering antenna (FSA) later on renamed in mid steering antenna (MSA) to notify that the MSA is protected behind the breeding blanket (BB) in DEMO, are investigated, analyzing their performance for several injection angles and launch points. This activity considers the constraints given by physics and engineering requirements, as for example the maximum power per port and the necessary local current drive to stabilize neo-classical tearing modes (NTMs) with a proper deposition width. The beam tracing calculations have been performed on different scenarios, providing information on plasma accessibility and deposited power. The microwave design and initial ideas about the ex-vessel EC transmission lines routing will be shown.

In-port-plug transmission line design of the ITER plasma position reflectometer

This work describes the microwave design of the transmission line housed in the in-port-plug region of the ITER plasma position reflectometer (PPR). The design of the components of the in-port-plug reflectometers (located in equatorial port-plug 10 (EPP10) and in upper-port-plug 01 (UPP01)) is presented. Using a 3D ray tracing code, the spatial position and optimum orientation angles of each set of emission and detection antennas were determined. A feasible path was then created from the obtained antenna positions and orientations to the primary vacuum window. Oversized tall waveguides were chosen to reduce ohmic losses. Due to space constraints in the ITER crowded environment, bends in oversized waveguides were unavoidable, and thus mode conversion was produced. To keep mode conversion losses at bay, hyperbolic secant curvature bends had to be used whenever possible. However, E-plane bends in tall waveguides proved to be especially critical, making it necessary to employ other approaches when higher bending angles were needed. Mode conversion results were obtained by evaluating the mode coupling equations. Ohmic losses have also been computed and their results compared with commercial simulators, obtaining a perfect agreement.

621 Successfully Advocating to Make Microwave Ovens “child-resistant” to Protect Young Children from Severe Scalds

Abstract Introduction Scald burn injuries are the leading cause of burn-related emergency room visits and hospitalizations for young children. An increasing portion of these injuries occur when children are removing items from microwave ovens. Many of these occur on the face/chest and can have lifelong physical, functional, aesthetic and psychological consequences. Over the past 15 years we have published a series of studies supporting our advocacy for a change in microwave oven design to protect children from severe scalds. Requiring microwave oven doors to be more difficult for a child to open would help to protect young children from these types of burn injuries. Our analysis of the National Electronic Injury Surveillance System found an estimated 7000 young children were treated in US emergency departments over the last decade for burns suffered when the child opened a microwave oven door and spilled the heated contents. This report describes our continued research and advocacy to finally get a regulatory agency to pass a “child-safety” mechanism for opening microwave doors. Methods In the United States, microwave ovens must meet the published microwave standard administered by Underwriters Laboratories (UL 923). In 2013, we formally proposed a change in the standard which underwent a voting process by the Standards Technical Panel. Microwave makers are well represented on the panel. This attempt did not pass. We continued to publish focused research, presented at national meetings, enlisted engineering students to design “child-resistant” microwave doors to demonstrate feasibility, and created a video to put a face to the statistics. In 2017, we became active members of a National Task Group convened by UL, and two authors became voting members on the 17 member microwave Standards Technical Panel. A new proposal was introduced by the Association of Home Appliances Manufacturers requiring “two distinct actions” to make it more difficult for a young child to open a microwave oven door. Multiple concerns were addressed including those related to the impact on seniors. We lobbied members who appeared undecided. Results On September 17, 2018, the UL 923 STP voted by a narrow margin to pass the measure. In the future, new microwave ovens sold in the United States will be required to be made with “child-resistant doors”. Conclusions Research and advocacy work together to protect children. Child scald risk will be reduced as microwaves with child-resistant doors replace current models. Applicability of Research to Practice Our research demonstrated that very young children are able to open microwave ovens putting them at risk for burn injuries. We worked diligently through various advocacy channels to actively improve the safety of microwave ovens. With the approved changes for future microwave design requirements, research and advocacy have now resulted in practice changes.

Rain Fade Analysis on Earth–to-Satellite Microwave Link Operating in Comoros

Microwave link operates at high frequency approximately 10 GHz and above, and it suffers from high attenuation in the tropical region due to high rain intensity. Therefore, a microwave designer should consider this effect in the design so that the link can be operated with good quality of service, high availability and reliability. This study is about analysis of rain fade in a tropical country, Comoros, where the rain intensity was considered from ITU-R Recommendation. This rain intensity was used to determine the rain fade for earth-to-satellite of links operating in this country at L, C, Ka, Ku and V bands in horizontal, vertical and circular for 0.001% to 1% of exceeded per year. From the analysis, it was found that the link has availability to work from 99.999% to 99% with least effects in all frequency bands at vertical polarization, except in V-band. At 99% of availability, it shows that B-PSK is the best technique for modulation to make the proposed link more reliable. To attain 10dB fade margin which allows the antenna to reach certain quality of services, the gain receiver, diameter and figure of merit were increased while the footprint was maximized. The outcome of this study will be useful resources to upgrade the availability and reliability of earth to satellite microwave link in Comoros.

Weeds [MicroBusiness

Discusses the concept of weeds and parasitic elements as they apply to the microwave engineering. Just as in gardening, there are weeds that one can keep in flowerbeds as well as those that are ripped out due to their hindrance to other grasses and flowers. Suggests that there are things like weeds in engineering too. Consider a transistor. Ideally, it is just a controlled current source. But real transistors have lots of parasitic elements—the weeds in a circuit. Sometimes we can take advantage of the parasitics in a circuit design. Consider, for example, the distributed amplifier. We use the parasitic gate and drain capacitances to realize artificial transmissions lines. These parasitics are, in essence, neutralized. Another place where we can make use of parasitics is in a microwave assembly. Examine other ways to make use of parasitics in microwave design and assembly.

Feedback [MicroBusiness

As a technically inclined adolescent, and then as an undergraduate student, I was intrigued by negative feedback. The ability to reduce distortion and stabilize a circuit and the wide variety of things that could be done with an operation amplifier were a revelation. Once I started working as a microwave design engineer, I didn’t generally find opportunities for negative feedback, but I would occasionally revisit the concept. Recently, I’ve been interested in positive feedback. It does plenty of interesting things, too. It can enhance the quality factor of a resonance, increase the gain of a circuit virtually limitlessly, and cause oscillations. The terms negative feedback and positive feedback are applied in many other areas. Customers provide feedback on how well products meet their needs. Sales people provide feedback about customer interest. Marketing provides feedback on what the market needs. The stock market provides feedback on company performance. Managers provide feedback on the performance of their employees.

An Angular-Displacement Microwave Sensor Using an Unequal-Length-Bi-Path Transversal Filtering Section

A class of angular-displacement microwave sensor based on a microwave signal-interference transversal filtering section (TFS) with unequal-electrical-length paths is reported for the first time. It consists of a bi-path TFS composed of two in-parallel transmission-line segments with distinct lengths, which is modified by adding a rotational open-circuit-ended stub as the rotor to a curved section as the stator of one of its line segments. In this manner, the spectral positions of the transmission zeros, which are produced in its filtering transfer function through destructive signal-energy interactions, are modified with the rotation of this additional stub. This allows single/multi-band angular displacement microwave-sensing capabilities in terms of transmission-zero inter-spacing variation for passbands/stopbands and stopband-peak-level modification to be attained by means of the mechanical rotation of the rotor. The theoretical operational principles of this type of bi-path-TFS-based angular-displacement microwave sensor and design curves for specific values of its electrical parameters are provided. Moreover, for experimental validation purposes, a proof-of-concept prototype of the devised TFS-based microwave sensor approach operating at 961 MHz with 180° dynamic range is prototyped in microstrip technology and measured. A comparative analysis of the developed angular-displacement microwave sensor with the state-of-the-art is also presented.

Design of a Ku-band MMIC LNA with a Simple T-type Input Matching Network

In this paper, the design of a wideband monolithic microwave integrated circuit (MMIC) low-noise amplifier (LNA) fabricated in 0.13-[Formula: see text]m GaAs pHEMT process is presented. A simple T-type input matching network (IMN) and a source feedback structure are employed to achieve low noise figure (NF). The MMIC LNA, which operates across 12–18[Formula: see text]GHz, can be used for satellite applications. Experimental results show an NF around 1.5[Formula: see text]dB in 12–17.5[Formula: see text]GHz and a minimum NF of 1.21[Formula: see text]dB at 16.5[Formula: see text]GHz. In addition, a flat small-signal gain of [Formula: see text][Formula: see text]dB is achieved at 13.5–17.5[Formula: see text]GHz. The input return loss is lower than [Formula: see text] dB at 12–14.5[Formula: see text]GHz and the output return loss is lower than [Formula: see text] dB at 12–17[Formula: see text]GHz. The power consumed is lower than 0.3[Formula: see text]W and the [Formula: see text] (1-dB compression point) output power is around 13[Formula: see text]dBm.