Complex Microwave Devices Research Articles

A high‐performance empty substrate integrated waveguide filter with mixed electric and magnetic coupling

AbstractAn empty substrate integrated waveguide (ESIW) bandpass filter with enhanced electric and magnetic coupling is proposed in this letter. ESIW uses the air as dielectric in order to reduce the dielectric loss caused by usual medium materials. However, the existence of air cavities requires at least three layers of structure, which greatly increases the difficulty of designing complex circuits with high‐performance and multiple requirements. The proposed mixed coupling structure creates the finite transmission zeros based on ESIW technology for the first time, which makes it possible to realize complex high‐performance circuits with ESIW technology. Taking advantage of the multilayer structure of the ESIW, the proposed cross‐coupling is conveniently realized with higher frequency selectivity and lower insertion loss while maintaining the substrate of three layers and the self‐encapsulation characteristics of ESIW. A fourth‐order filter with an H‐shaped slot line on the top metal plane of two adjacent air cavities is produced. A good agreement between the measurements and simulations indicates that the proposed filter achieves an insertion loss as low as 0.7 dB and the 6.1% bandwidth at 9.85‐GHz X band. It demonstrates the improvement of insertion loss and frequency selectivity, which lays a foundation for the design of complex microwave devices.

Multiscale modeling and simulation methods for electromagnetic and multiphysics problems

Multiscale modeling and simulation methods for electromagnetic and multiphysics problems

THE DEPENDENCE OF THE ELECTRODYNAMIC CHARACTERISTICS OF THE MICROSTRIP PHASED ARRAY SUBARRAY ON THE METHOD OF POWER SUPPLY

Microwave technology in microstrip design is widely used in various antenna systems. The active use of phased array (PA) of this type makes developers around the world search for various options of its construction. To improve individual characteristics, in particular, expand the scanning angle, as well as optimize the configuration of the excitation of the PA, they use subarrays that combine a given number of elements of the entire array. In this paper, we considered various options for constructing microstrip PA subarrays made on a homogeneous substrate from a high-frequency laminate GIL_GML 1000, in particular, various methods for their excitation. Using modern, accurate 3D electrodynamic modeling environment and HF device analysis, we studied changes in the electrodynamic characteristics of the simulation model of a multi-element microstrip PA subarray, depending on how the excitation is organized. This article discusses three simulation models of subarrays for microstrip PA with various options for their excitation. All subarrays have a radiation pattern of a special shape. After calculating the main characteristics, the issue of the most preferred organization of subarray power supply for the developed PA was solved. It is shown that in practice, the study of parameters and decision-making on the design of complex microwave devices, possibly without expensive field modeling.

The Grid Methods of the Recognition of the Region of Efficiency of Microwave Devices

Some results for design and optimization of complex microwave devices are considered in this article. The problems are investigated from the standpoint of recognition of region of efficiency in which necessary values of given output characteristics are appeared. The application for optimization of meshes that are uniform in the multidimensional space of parameters is discussed. The solution of the approximate optimization problem using a specially created mathematical model of the device and software packages that implement time-consuming computational procedures is debated.

3D Net-Shape Manufacturing of Complex Ceramic Parts by High Resolution Stereo Lithography – Examples of Application to Biomedical and Industrial Products

Solid Freeform Fabrication (SFF) processes are fairly new shaping methods, which allow the direct fabrication of complex ceramic structures, without tooling or machining, on the basis of a component CAD file. SFF techniques provide an attractive answer for applications with the need to produce custom designs while also controlling the product structure or producing multimaterial devices demanding improved properties or multifunctional components. Stereolithography (SL) is a layer manufacturing process based on the space-resolved polymerisation of a UV photocurable compound consisting in a dispersion of ceramic particles in a monomer containing a photoinitiator. Improvements in the SL process, notably understanding and driving the key parameters influencing the 3D resolution of the reactive compound, now make it possible to directly manufacture useful 3D ceramic parts with final properties similar or identical to those obtained from traditional processes. SL processing applications are numerous and include medical implants, complex microwave devices, refractory molds and cores, MEMS, microfluidic networks for micro reactors, drug delivery devices or biological analysis, etc...

Focus on software and data acquisition

Focus on software and data acquisition

Fabrication of Millimeter Wave Components Via Ceramic Stereo‐ and Microstereolithography Processes

Complex ceramic parts, designed by 3D electromagnetic simulations for microwave devices of high performances, are difficult, even impossible, to elaborate by classical ceramic processing routes. This paper demonstrates the direct fabrication of useful complex microwave devices in millimeter and submillimeter wavelength domains, with a high dimensional resolution, by the numerical techniques of stereolithography and microstereolithography. Alumina and zirconia formulations have been developed with a powder loading >50 vol%, a suitable rheology to spread thin (25–50 μm) and homogeneous layers, and with a sufficient reactivity to UV for polymerization. Devices built with a satisfying manufacturing accuracy have presented excellent experimental electrical behaviors in good agreement with the theoretical ones.

Small-Size Complex Microwave Devices (CMD) for Onboard Applications

Small-size complex microwave devices (CMD) are designed for applications in onboard air-, sea-, and ground-based radio-electronic systems. They are compact integrated multifunctional devices, which are capable of providing generation, processing, and amplification of complex multifrequency microwave signals, although their operating frequency band is relatively low - about 2%. Small-sized and miniature multiple-beam klystrons are, as a rule, the output power tube of choice for onboard CMDs. CMDs are usually applied to systems where high power, high level of integration (multifunctionality), and high signal quality are desired. Design parameters and performance capability for several onboard CMDs are discussed in this paper. In addition, distinctions between onboard CMDs and state-of-the-art onboard microwave power modules are considered

Perfectly matched layer implementation using bilinear transform for microwave device applications

This paper presents an extensive study on the perfectly matched layer (PML) implementation using bilinear transform in the finite-difference time-domain (FDTD) simulation. The bilinear transform is used to implement both the stretched coordinate PML (SC-PML) and the uniaxial PML (UPML) with the complex frequency-shifted (CFS) equations. It is shown that with the CFS factor, the implemented SC-PML and UPML attain significantly lower relative reflection error over wide frequency range with both superior in performance to the split-field PML. The FDTD algorithm incorporating these PMLs is applied to analyze wide-band responses of some complex microwave devices, including RF microelectromechanical systems switch and coplanar waveguide crossover junction.

Buffer layers for Tl-2212 thin films on MgO and sapphire substrates

High quality Tl-2212 films can be readily grown on LaAlO/sub 3/ substrates, but the design of complex microwave devices in these films is made more difficult by the twinning of the substrate. CeO/sub 2/ buffer layers on sapphire have been previously demonstrated to offer excellent substrates for Tl-2212 films. We have been exploring alternative architectures for buffer layers on MgO and sapphire. Epitaxial Tl-2212 superconducting thin films have been successfully grown on Gd/sub 2/O/sub 3/-buffered MgO substrates by sputter deposition of a Tl-free precursor followed by an ex-situ thalliation anneal. The Tl-2212 films were aligned with the c-axis normal to the film surface, and also had excellent in-plane orientation with Tl-2212 [100] aligned with the Gd/sub 2/O/sub 3/ and MgO [110]. The critical temperatures of the films ranged from 100 - 103 K and transport and inductive critical current densities of 7.5 /spl times/ 10/sup 5/ A/cm/sup 2/ at 77 K have been achieved. We have also fabricated epitaxial GdAlO/sub 3/ buffer layers on sapphire substrates which support epitaxial growth of Tl-2212 but with relatively poor microstructure. High quality films have been prepared on the new (La,Sr)(Al,Ta)O/sub 3/ (LSAT) substrates.

A rigorous and efficient full-wave analysis of uniform bends in rectangular waveguide under arbitrary incidence

In this paper, a rigorous full-wave analysis of uniform bends in rectangular waveguides is performed. An accurate and efficient method-of-moments solution combined with the generalized-admittance-matrix (GAM) formulation is proposed in order to achieve a full-wave characterization of the analyzed structures. This full-wave modal solution turns out to be necessary for modeling complex microwave devices involving an arbitrary number of discontinuities between curved and straight waveguides, where all the modes of the involved guides are excited. The key feature of the presented method lies in the GAM representation of single and cascaded curved E- and H-plane uniform bends, which allows the construction of accurate models of the investigated discontinuities. To validate the theory, the convergence of the method is discussed and comparisons between our simulations and theoretical and experimental data are presented. The excellent behavior of our results, together with the computational efficiency of the proposed method, proves that the developed computer-aided-design tool can be successfully used in the design of complex microwave subsystems involving curved waveguides.

Neural network applications in microwave device design

This paper deals with many different neural network architectures that have been introduced to simulate the electromagnetic behavior of complex microwave devices and antennas. Many issues linked to the peculiarities of such devices are addressed. Furthermore, the inverse problem of designing a microwave device, once the required characteristics are given, is also developed by using a neural network approach. © 2002 John Wiley & Sons, Inc. Int J RF and Microwave CAE 12: 90–97, 2002.

Electromagnetic analysis for microwave FET modeling

This letter presents a technique to analyze complex microwave devices. An electromagnetic three-dimensional (3-D) software is applied to characterize the distributed part of the structure. It is coupled to a circuit simulator to introduce the contribution on the electrical response of the localized passive or active elements contained in the device. The link between the two parts is made thanks to a new type of access, "the localized access". We have applied this method to the study of a field effect transistor and good agreements are observed between simulations and measurements from 1 to 30 GHz.

Automatsko baždarenje mikrotalasnih oslabljivača

Microwave attenuators are components of many complex radio frequency and microwave devices but they can be used separately for repair, adjustment or calibration. Disregarding the usage, attenuators ought to be verified in terms of metrology in order to determine with reliability if the standing wave ratios and the attenuation of attenuators are within prescribed limits. This paper treats the method of automatic calibration of microwave attenuators with the attenuation of up to 70 dB.

Rigorous Design Of Dielectric Resonator FiltersApplying The Finite Element Method

Numerical techniques permit now to analyze rigorously complex voluminous ar planar microwave devices. In this paper, a rigorous design of dielectric resonator filters applying the finite element method is described. We first present a dual mode coupling technique which replaces classical dielectric resonators, coupling and tuning screws commonly used in dual mode filters, by slotted dielectric resonators. Next, to explain the generation of transmission zeros in the insertion loss performance of microwave filters, we define a new theoretical analysis based on the contribution of the first dielectric resonator hybrid mode and of higher order modes. This analysis can be applied to any type of microwave dual mode filter. Finally, a synthesis method applying the finite element method, is developed to design rigorously for the first time, a four and a eight pole slotted dielectric resonator elliptic filters. The experimental results obtained with no tuning and the theoretical ones show good agreement.