Flexible and efficient computer‐aided design tool for advanced comb‐line rectangular waveguide filters

A very flexible and efficient computer‐aided design (CAD) tool, specifically suited for advanced comb‐line rectangular waveguide filters, is presented in this work. The developed software tool, which makes use of a full‐wave analysis technique based on the Boundary Integral—Resonant Mode Expansion method, allows loading the considered comb‐line resonators with any number of radially symmetrical partial‐height metallic posts. The implemented CAD tool also allows dealing with coupling windows of arbitrary cross‐section, thus drastically enhancing the flexibility of the CAD process. The excitation of the analyzed components, which is performed using generalized coaxial probes, has also been integrated in the implemented software tool, thus achieving a full‐wave electromagnetic characterization of the whole component. Furthermore, a novel simple procedure to efficiently connect all the obtained wide‐band matrices is proposed. To validate the accuracy and efficiency of this novel CAD tool, several new designs concerning advanced band‐pass comb‐line waveguide filters are presented. The accuracy of the developed CAD tool has been successfully validated by comparing the obtained results with numerical data provided by a commercial tool based on the finite‐element method. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:696–708, 2015.     

Application of the computer‐aided analysis for modeling the behavior of a TCXO

Quartz crystal oscillators for many radio frequency (RF) applications must provide a high‐frequency stability in a wide temperature range. To do this, a temperature compensation network is commonly included. This study analyzes and determines the frequency behavior of an oscillator circuit with variations in temperature and shows how simulation may be employed for the design of high‐stability quartz crystal oscillators. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 22–32, 2001.     

Yield‐oriented design protocol and equivalent circuit model for W‐band E‐plane waveguide‐to‐microstrip transitions

This work presents a comprehensive design protocol for a W‐band E‐plane waveguide‐to‐microstrip transition covering all aspects, from the probe design, matching, cut‐off cavity size estimations, verification analysis with different 3D EM simulators, and the entire fabrication process, with special emphasis on tolerances and yield with optimized costs. In fact, a complete study of the manufacture yield is done without the need to fabricate a large number of units of the microstrip‐to‐waveguide transition by taking advantage of the Monte Carlo tools embedded in 3D EM simulators. A simple equivalent circuit model of the transition is proposed and validated to be used in W‐band system level simulations. These are requirements to enable massive use of W‐band products (i.e., concealed weapons detection, imaging, etc.) with reasonable costs. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:77–91, 2014.     

Fast simulation‐driven feature‐based design optimization of compact dual‐band microstrip branch‐line coupler

Design of miniaturized microwave components is a challenging task. On one hand, due to considerable electromagnetic (EM) cross‐couplings in highly compressed layouts full‐wave EM analysis is necessary for accurate evaluation of the structure performance. Conversely, high‐fidelity EM simulation is computationally expensive so that automated determination of the structure dimensions may be prohibitive when using conventional numerical optimization routines. In this article, computationally efficient simulation‐driven design of a miniaturized dual‐band microstrip branch‐line coupler is presented. The optimization methodology relies on suitably extracted features of a highly nonlinear response of the coupler structure under design. The design objectives are formulated in terms of the feature point locations, and the optimization is carried out iteratively with the linear model of the features utilized as a fast predictor. The entire process is embedded in the trust‐region framework as convergence safeguard. Owing to only slightly nonlinear dependence of the features on the geometry parameters of the circuit at hand, the optimized design satisfying prescribed performance requirements is obtained at the low computational cost of only 24 high‐fidelity EM simulations of the structure. Experimental validation of the fabricated coupler prototype is also provided. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:13–20, 2016.     

Design and development of the W‐band corrugated waveguide mode converter for fusion plasma experiments

In this paper, a W‐band mode converter is designed using a circular corrugated horn and its detailed numerical study is presented. The proposed mode converter was fabricated, and the measured results are validated. The device converts fundamental mode (TE₁₁) into a Hybrid mode (HE₁₁) mode in a frequency range of 75 GHz to 105 GHz. The reflection coefficient is less than ?15 dB and a peak directivity of 24.5 dB is achieved. The corrugated horn also shows good mode purity. The measured gain of the device was found to be 18.05 dB. The designed mode converter will be useful in Electron Cyclotron Resonance Heating system for fusion plasma experiments.     

Computer aided design for dual‐band filters with complex source and load impedances

This article presents a computer aided technique to synthesize the filtering function for dual‐band microwave filters with complex source and load impedances. Based on the exchange‐Remez algorithm and the power wave renormalization theory, the characteristic function is first obtained with assigned ripple level at the first passband. Two additional transmission zeros are then optimally allocated to control the ripple level at the second passband. By directly modifying the coupling matrix elements in the first and last stages, a simplified method is also presented when the loading impedance is frequency‐independent. Three synthesized examples with both controlled in‐band and out‐of‐band responses are presented. Finally, LC multi‐coupled circuits are also provided to validate the effectiveness of the proposed method.     

Design and optimization of multi‐band Wilkinson power divider

In this paper, a general and easy procedure for designing the symmetrical Wilkinson power divider that achieves equal‐power split at N arbitrary frequencies is introduced. Each quarter‐wave branch in the conventional Wilkinson divider is replaced by N sections of transmission lines, and the isolation between the output ports is achieved by using N resistors. The design parameters are the characteristic impedances and lengths of the N transmission line sections, and the N isolation resistors. The even–odd modes of analysis are used to derive the design equations. Closed‐form expressions, which are suitable for CAD purposes, are derived for the dual‐band divider. For N ≥ 3, closed‐form expressions are not available, and therefore, the powerful particle swarm optimization method is used to obtain the design parameters. Examples of the dual‐, triple‐, and quad‐band dividers are presented to validate the proposed design procedure, and the results are compared, wherever possible, with published results using other methods. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Reduced‐cost surrogate modeling of input characteristics and design optimization of dual‐band antennas using response features

In this article, a procedure for low‐cost surrogate modeling of input characteristics of dual‐band antennas has been discussed. The number of training data required for construction of an accurate model has been reduced by representing the antenna reflection response to the level of suitably defined feature points. The points are allocated to capture the critical features of the reflection characteristic, such as the frequencies and the levels of the resonances, and supplemented by the additions (infill) points, which is necessary to provide sufficient data that allows restoring the entire response through interpolation. Because the coordinates of the feature points exhibit less nonlinear behavior (as a function of antenna geometry parameters) compared to S‐parameters as a function of frequency, surrogate model construction can be realized with a smaller number of data points. The presented modeling approach is demonstrated using an example of a planar dipole antenna. Also, the feature‐based method is favorably compared to direct modeling of reflection characteristics using kriging. The relevance of the technique is further verified by its application for design optimization.     

Design of a novel metasurface for dual‐band Fabry‐Pérot cavity antenna

A novel reflective metasurface which presents different reflection phases to different polarization waves is designed in this article. The metasurface is used as the ground plane of a Fabry‐Pérot cavity (FPC) antenna. The radiator of the FPC antenna is a dual‐band patch antenna which has different polarizations in different bands, so by tuning the reflection phase of the metasurface correctly, the FPC antenna can work in two frequency bands. A prototype antenna is fabricated and measured. The measured results show that the antenna can operate at 8.35‐8.56 GHz (2.5%) in x‐polarization and 9.5‐10.1 GHz (6.1%) in y‐polarization. The maximum realized gains of the antenna in two bands are 17.6 dB at 8.75 GHz and 19 dB at 9.8 GHz. The measured results agree well with the simulated results which confirm the correctness of the design.     

Multiobjective design optimization of a nano-CMOS voltage-controlled oscillator using game theoretic-differential evolution

Engineering problems presenting themselves in a multiobjective setting have become commonplace in most industries. In such situations the decision maker (DM) requires several solution options prior to selecting the best or the most attractive solution with respect to the current industrial circumstances. The weighted sum scalarization approach was employed in this work in conjunction with three metaheuristic algorithms: particle swarm optimization (PSO), differential evolution (DE) and the improved DE algorithm (GTDE) (which was enhanced using ideas from evolutionary game theory). These methods are then used to generate the approximate Pareto frontier to the nano-CMOS voltage-controlled oscillator (VCO) design problem. Some comparative studies were then carried out to compare the proposed method as compared to the standard DE approach. Examination on the quality of the solutions across the Pareto frontier obtained using these algorithms was carried out using the hypervolume indicator (HVI).     

Design and analysis of a quad‐band substrate‐integrated‐waveguide cavity backed slot antenna for 5G applications

A planar and compact substrate integrated waveguide (SIW) cavity backed antenna and a 2 × 2 multi‐input multi‐output (MIMO) antenna are presented in this study. The proposed antenna is fed by a grounded coplanar waveguide (GCPW) to SIW type transition and planned to be used for millimeter‐wave (mm‐wave) fifth generation (5G) wireless communications that operates at 28, 38, 45, and 60 GHz frequency bands. Moreover, the measured impedance bandwidth (|S₁₁| ≤ ? 10 dB ) of the antenna covers 27.55 to 29.36, 37.41 to 38.5, 44.14 to 46.19, and 57.57 to 62.32 GHz bands and confirms the quad‐band characteristic. Omni‐directional radiation characteristics are observed in the far‐field radiation pattern measurements of the antenna over the entire operating frequency. The reported antenna is compact in size (9.7 × 13.3 × 0.6 mm³) and the gain values at each resonance frequency are measured as 3.26, 3.28, 3.34, and 4.51 dBi, respectively. Furthermore, the MIMO antenna performance is evaluated in terms of isolation, envelope correlation coefficient and diversity gain.     

Analysis and optimization of the unpredictable transmission zero in X‐band filter design

This article focuses on the common problem of uncontrollable transmission zero (TZ) in X‐band filter design. Using uniform impedance rectangular resonator (UIRR) to design an X‐band filter always results in an unpredictable TZ on the low‐frequency side of the passband, which greatly deteriorates the frequency selectivity of the filter performance. Electromagnetic coupling polarity analysis of the UIRR shows that the magnetic crosscoupling between nonadjacent resonators which is opposite to the main coupling plays a major role in the unpredictable TZ. By optimizing the UIRR from the loop structure with a small opening to the folded one, weak couplings between resonators are obtained. A high‐temperature superconducting filter at X‐band using folded UIRR resonator was designed and fabricated with a center frequency of 10.01 GHz and a bandwidth of 58 MHz, and the uncontrollable TZ has been removed successfully from the low‐frequency side of passband. The measured insertion loss is less than 0.4 dB and the return loss is greater than 15 dB.     

An integral‐imaging‐based head‐mounted light field display using a tunable lens and aperture array

A head‐mounted light field display based on integral imaging is considered as one of the promising methods that can render correct or nearly correct focus cues and address the well‐known vergence‐accommodation conflict problem in head‐mounted displays. Despite its great potential, it still suffers some of the same limitations of conventional integral imaging‐based displays such as low spatial resolution and crosstalk. In this paper, we present a prototype design using tunable lens and aperture array to render 3D scenes over a large depth range while maintaining high image quality and minimizing crosstalk. Experimental results verify and show that the proposed design could significantly improve the viewing experience.     

Design of a cavity‐based filtering antenna with dual‐polarization operating at Ka‐band

The contribution of this work is to propose a cavity‐based antenna with both dual‐polarization and bandpass filter characteristics. Proper cavity resonators and antenna based on the substrate integrated waveguide (SIW) technology are designed utilizing the low temperature co‐fired ceramics (LTCC) for demonstration. By properly arranging and coupling the cavities, a shaping of filter‐like response for the antenna gain and input return loss can be obtained. Measures for achieving a good isolation and a low cross‐polarization level have also been taken into account during the design procedure. A 4th‐order prototype working in the Ka‐band is designed and fabricated. Investigations show that the antenna presents a good isolation below ‐29 dB across the operating bandwidth, together with a cross‐polarization level lower than ‐25 dB at the center working frequency. The performance of the prototype has been verified in the measurement.     

Design of a compact dual‐band folded‐waveguide bandpass filter using multilayer waveguide resonators

A novel compact dual‐band bandpass filter based on multilayer folded‐waveguide (FWG) structure is presented in this article.In this design, slots are used to realize direct coupling between adjacent resonators and apertures are adopted to implement cross coupling between non‐adjacent resonators.A new technique of external quality factor of FWG resonator and coupling coefficients between different resonators are studied using full‐wave simulator. In order to demonstrate the proposed technique, a four‐pole dual‐band bandpass filter is designed, fabricated and measured using vector network analyzer. Measurement results which are well agreed with simulation results are presented. Moreover, four‐pole substrate integrated folded waveguide SIFW dual‐band bandpass filter, using two layers of slotted folded waveguide resonators, is demonstrated. The proposed filter has a compact size and it is excellent candidate for the application of wireless communication systems. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:780–788, 2015.     

Development of a color‐tunable polychromatic organic‐light‐emitting‐diode device for roll‐to‐roll manufacturing

A flexible vertically stacked flexible polychromatic color‐tunable OLED has been developed by means of low resistive intermediate electrode technology. The polychromatic OLED has a capability to show 16 million colors with 105% National Television Committee Standard (NTSC) color reproduction. The device can produce arbitrary shape with arbitrary colors, suitable for artistic expressions, just as many as those used in information displays. Independently controlled red, green, and blue light‐emitting layers are stacked vertically. With conventional indium tin oxide technology, because of the temperature restriction, it was quite difficult to achieve low resistance on plastic substrate. The reported numbers were all more than 80 Ω/□. According to the surface mobility control using Fick's law analysis, low sheet resistance 7.34 Ω/□ on plastic film was developed. At first, flexible 7.17 cm² transparent OLED was fabricated for the performance confirmation of transparent electrode. And then polychromatic color‐tunable OLED with the same size were successfully fabricated on plastic. With optical length optimization for each color stack of polychromatic OLED, more than 100% color reproduction in National Television Committee Standard was achieved by stack design. The polychromatic device can be used for colored illumination, as well as for organic‐light‐emitting display pixels for three times emission than conventional pixel design. The device is fabricated on plastic substrate so that the polychromatic organic‐light‐emitting‐diode device is manufacturable with roll‐to‐roll production line.     

The effect of a graph‐oriented computer‐assisted project‐based learning environment on argumentation skills

The purpose of this quasi‐experimental study was to explore how seventh graders in a suburban school in the United States developed argumentation skills and science knowledge in a project‐based learning environment that incorporated a graph‐oriented, computer‐assisted application. A total of 54 students (three classes) comprised this treatment condition and were engaged in a project‐based learning environment that incorporated a graph‐oriented, computer‐assisted application, whereas a total of 57 students (three classes) comprised the control condition and were engaged in a project‐based learning environment without this graph‐oriented, computer‐assisted application. Verbal collaborative argumentation was recorded and the students' post essays were collected. A random effects analysis of variance (ANOVA) was conducted and a significant difference in science knowledge about alternative energies between conditions was observed. A multivariate analysis of variance (MANOVA) was conducted and there was a significant difference in counterargument and rebuttal skills between conditions. A qualitative analysis was conducted to examine how the graph‐oriented, computer‐assisted application supported students' development of argumentation skills and affected the quality of collaborative argumentation. The difference in argumentation structure and quality of argumentation between conditions might explain a difference in science knowledge as well counterargument and rebuttal skills (argumentation) between both conditions. This study concluded that a project‐based learning environment incorporating a graph‐oriented, computer‐assisted application was effective in improving students' science knowledge and developing their scientific argumentation skills.     

Design of a wideband filtering power divider with good in‐band and out‐of‐band isolations

In this article, a wideband filtering power divider with good in‐band and out‐of‐band isolations is designed based on a hybrid Wilkinson and Gysel structure. To achieve a good in‐band response, two additional in‐band transmission poles can be introduced by installing the coupled‐line structures at each port. By mounting a stepped impedance open stub at the input port, two transmission zeros are generated near the passband to improve the passband skirt. Furthermore, the out‐of‐band rejection and isolation are achieved by the other two transmission zeros, which are produced by the open stub and the three coupled‐line sections mentioned above. Additionally, a good in‐band isolation is realized by the isolation resistor between output ports. For the demonstration, a wideband filtering power divider centered at 1.5 GHz with a 56% fractional bandwidth and 20‐dB isolation is designed and fabricated. The simulated and measured results are in good agreement with each other.     

Computer‐aided design of 3D microwave filter using quasi‐planar high Qu dielectric resonator

A dielectric resonator filter is proposed for high‐speed data communication systems and for multilayer filter applications. The structure is composed of a partially metallized dielectric plate enclosed in a parallelepipedic cavity. This topology allows high integration in a planar‐type environment. The proper excitation is ensured by coplanar lines directly integrated on the dielectric resonator. This structure, easily manufactured, is suitable for high frequency‐filtering and power applications. In order to realize two‐ and four‐pole filters without tuning, some new coupling and frequency compensation techniques are presented. To compensate for a parasitic effect, a direct optimization method is combined applying a global electromagnetic (EM) analysis to describe the four‐pole filter. Some experiments are performed to verify the theoretical design. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 333–341, 2000.     

Design and simulation of a novel RF-MEMS tunable narrow band LC filter in the UHF band

Microsystem Technologies - The design and simulation of a continuously tunable LC filter by integration of microelectromechanical systems (MEMS) is presented in this work. The proposed tunable LC...