Multilayer Microwave Research Articles

Design of ultrawideband multilayer slot-coupled vertical microstrip transitions employing novel patch shapes

Design of two different slot-coupled vertical microstrip–microstrip transitions for ultrawideband (UWB) multilayer microwave circuits are introduced. Transitions consist of two stacked substrates with common ground in the middle and two microstrip-feed-lines connected to microstrip patches on the top and bottom. The proposed transitions use broadside coupling between microstrip patches at the top and the bottom layers via a rectangular-shaped slot in the common ground plane (midlayer). The proposed patch shapes are trapezoidal and butterfly shapes, which are capable of achieving broadband characteristics for UWB operation. Extensive parametric studies are performed to address the effect of varying the transition parameters on the coupling value and the operational frequency bandwidth. The simulated results using two simulation programs with two different numerical techniques show that the proposed transitions have low transmission coefficient (less than 1.2 dB) and a high reflection coefficient (better than 16 dB) over the 3.1–10.6 GHz frequency range. Two transition prototypes are fabricated and then tested experimentally using Agilent E8364B PNA Network Analyzer. Experimental results agree well with the simulated ones. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:747–756, 2015

PARTICLE SWARM OPTIMIZATION FOR OPTIMAL DESIGN OF BROADBAND MULTILAYER MICROWAVE ABSORBER FOR WIDE ANGLE OF INCIDENCE

Microwave absorbers find a plethora of applications in the modern-day military and civil industries. This paper compares the performances of different variations of the Particle Swarm Optimization (PSO) algorithm to obtain optimal designs for multilayer microwave absorber over different frequency ranges, angles of incidence and polarizations. The goal of this optimization is to minimize maximum overall reflection coefficient of the absorber by choosing suitable layers of materials from a predefined database and simultaneously make the overall thickness the least practically possible. Numerical optimal results for each variation of the PSO are presented and the best results are compared with those existing in literature.

Echo simulation of lunar penetrating radar: based on a model of inhomogeneous multilayer lunar regolith structure

Lunar Penetrating Radar (LPR) based on the time domain Ultra-Wideband (UWB) technique onboard China's Chang'e-3 (CE-3) rover, has the goal of investigating the lunar subsurface structure and detecting the depth of lunar regolith. An inhomogeneous multi-layer microwave transfer inverse-model is established. The dielectric constant of the lunar regolith, the velocity of propagation, the reflection, refraction and transmission at interfaces, and the resolution are discussed. The model is further used to numerically simulate and analyze temporal variations in the echo obtained from the LPR attached on CE-3's rover, to reveal the location and structure of lunar regolith. The thickness of the lunar regolith is calculated by a comparison between the simulated radar B-scan images based on the model and the detected result taken from the CE-3 lunar mission. The potential scientific return from LPR echoes taken from the landing region is also discussed.

Microwave dielectric properties and compatibility with silver of low-fired Li2MgTi3O8 ceramics with Li2O-MgO-B2O3 frit

The effects of Li2O-MgO-B2O3 (LMB) glass additive on the sintering characteristics, phase purity, microstructure, and microwave dielectric properties of Li2MgTi3O8 ceramics were investigated. The experimental results demonstrate that the addition of LMB glass effectively lowers the sintering temperature of Li2MgTi3O8 ceramic from 1025 °C to 875 °C and induces no obvious degradation of the microwave dielectric properties. Typically, the 1.5% LMB glass-added Li2MgTi3O8 ceramic sintered at 875 °C for 4 h shows excellent microwave dielectric properties of Q×f=45403 GHz, εr=25.9 and τf≈0 °C−1. The dielectric ceramic exhibits stability against the reaction with the Ag electrode, which indicates that the ceramics could be applied in multilayer microwave devices requiring low firing temperatures.

Evolution of double magnetic resonance behavior and electromagnetic properties of flake carbonyl iron and multi-walled carbon nanotubes filled epoxy-silicone

Abstract The complex permittivity and permeability, reflection loss of the flake carbonyl iron (FCI) particles and multi-walled carbon nanotubes (MWCNTs) filled epoxy-silicone resin were investigated in the frequency range of 2–18 GHz. Both the values of complex permittivity and permeability were enhanced with increasing FCI content. The magnetic resonance behavior of such composites was mainly depended on the content of FCI particles, and the μ ″ –f spectra changed from no visible peak to double resonance as the FCI content increased from 10 to 50 wt%. Single-layer and multi-layer microwave absorbing coatings were also designed based on the transmission line theory and electromagnetic properties of the absorber. By changing the filler content and/or optimizing the absorber structure, the measured reflection loss below −10 dB can be obtained in the frequency range of 2–16.9 GHz for FCI particles and MWCNTs filled four-layer absorber.

Designing of Multilayer Microwave Absorbing Coating of Advanced Carbon and Metal Powder Based on Genetic Algorithm

The coating optimization has been carried out for the design of microwave absorbing materials of advanced carbon and metal powder based on genetic algorithm. An optimum designing program for multilayer absorbing material has been compiled by matlab language. The program can transfer the electromagnetic parameters of advanced carbon and metal powder which measured by vector network analyzer, and can process thickness optimum design of different absorbing materials in the range of 0.5~6GHz. The result shows that, the best absorbing layers can easily gained from the electromagnetic parameter database by computing with this program according to our requirement. The objective function in genetic algorithm has great effect on the optimization results. The multi-constant weight method is very helpful to design the microwave absorbing layers of broad-frequency and high absorption.

A W-Band Multi-Layer Microwave Window for Pulsed Operation of Gyro-Devices

A broadband multi-layer microwave window operating in the W-band frequency range was numerically simulated, constructed and its microwave properties measured. The window acts to separate vacuum and atmosphere. It had to meet strict requirements for application in gyro-amplifiers of broadband, low reflection and high mechanical strength. The window was manufactured showing a ${- 20}~{\rm dB}$ reflection over 90–100 GHz (except in two small regions), which is in good agreement with the numerical simulation presented in this letter.

Modeling and Performance of Microwave and Millimeter-Wave Layered Waveguide Filters

This paper presents the novel designs, analysis, and performance of 4-pole and 8-pole microwave and millimeter-wave (MMW) waveguide filters for operation at X and Y frequency bands. The waveguide filters have been designed and analyzed based on the mode matching and coupled resonators design techniques employing layered technology. Thorough waveguide filters working at X-band and Y-band have been designed, analyzed, fabricated, and tested along with the analysis of the output characteristics. Accurate designs of RF waveguides along with their filters based on the E-plane filter concept have been carried out with the ability of fitting into layered technology in high frequency production techniques. The filters demonstrate the appropriateness in order to develop high-performance well-established designs for systems that are intended for the multi-layer microwave, millimeter- and sub-millimeter-waves devices and systems; with the potential employment in radar, satellite, and radio astronomy applications. DOI: http://dx.doi.org/10.11591/telkomnika.v11i7.2411 Full Text: PDF

Effects of ZnO and B2O3on the Microstructure and Microwave Dielectric Properties of 5Li2O-1Nb2O5-5TiO2Ceramics

The effects of ZnO and B2O3 addition on the sintering behavior, microstructure, and the microwave dielectric properties of 5Li2O-1Nb2O5-5TiO2 (LNT) ceramics have been investigated. With addition of low-level doping of ZnO and B2O3, the sintering temperature of the LNT ceramics can be lowered down to near 920°C due to the liquid phase effect. The Li2TiO3ss and the “M-phase” are the two main phases, whereas other phase could be observed when co-doping with ZnO and B2O3 in the ceramics. And the amount of the other phase increases with the ZnO content increasing. The addition of ZnO does not induce much degradation in the microwave dielectric properties but lowers the τf value to near zero. Typically, the good microwave dielectric properties of er = 36.4, Q × f = 8835 GHz, τf = 4.4 ppm/°C could be obtained for the 1 wt% B2O3 and 4 wt% ZnO co-doped sample sintered at 920°C, which is promising for application of the multilayer microwave devices using Ag as internal electrode.

Frequency fine adjusting of LTCC microwave resonators based on BZN ceramics

Abstract BZN-based ceramics with low sintering temperature were prepared using a conventional route. Green sheets of ceramics were formed using tape casting technique. The laminated tapes were pressed together for forming multilayer microwave resonators. The green chips were sintered at about 950 °C. In order to adjust the resonant frequency of resonator, the width of the ground terminal electrode of the stripline can be changed. When the width of the ground terminal electrode varied from 1.0 to 2.4 mm, the resonant frequency of resonator changed from 0.971 GHz to 0.986 GHz. As the width of the ground terminal electrode increased, the resonant frequency of resonator varied slowly and then saturated. The maximum adjusting value of the resonant frequency of resonator is about 1.5%.

A 7–21 GHz Dual-Polarized Planar Ultrawideband Modular Antenna (PUMA) Array

The design, fabrication, and measurement of a 16 × 16 dual-polarized planar ultrawideband modular antenna (PUMA) array operating over 7-21 GHz (3:1 bandwidth) are presented. The array is comprised of tightly coupled dipoles printed on a grounded dielectric substrate and are excited by an unbalanced feeding scheme that eliminates external wideband baluns and feed organizers. The array can be assembled modularly, where each low-profile, fully planar, low-cost tile is fabricated using standard multilayer microwave PCB techniques. A unique solderless, modular interconnect mates the array to a dilation fixture that facilitates measurements using standard surface-mount assembly (SMA) connectors and terminations. After presenting the most critical design trends, simulation results of the final array in infinite, infinite × finite, and finite × finite models are compared with measurements. This prototype array exhibits a measured active VSWR <; 2.1 and close to ideal gain at broadside, and VSWR <; 2.8 with low cross-polarization out to θ = 45° in all planes, showing close agreement with simulations.

Effect of Ni fillers on microwave absorption and effective permeability of NiCuZn ferrite/Ni/polymer functional composites

This work investigated the concentration dependence of the nanosized Ni fillers on crystallographic structure, electrical transport, effective permeability, constitutive electromagnetic property, and microwave-absorbing behavior of the insulating polymer matrix embedded with NiCuZn ferrites (NCZFs). The effective permeability of the percolation ferrite composites which are composed of three-phases, 0.55 NCZF/(x) nano Ni/(0.45-x) polymer, increases with x till x=0.1. It is due to the Ni fillers acting as magnetic bridge to enhance magnetic exchange coupling and to decrease the demagnetization field between ferrite granules. The electrical resistivity decreases abruptly above the percolation threshold (x=0.02). It is ascribed to the narrowed polymer gaps and the significant decrease in the grain boundary resistance after the Ni additions. The frequency response of the microwave absorption in ferrite composites is attributed to its macroscopic magnetic loss and dielectric loss correlated with domain-wall motion, spin resonance, and dipolar relaxation. Various multilayer microwave absorbers terminated by perfect metal conductor (PMC) are systematically designed utilizing the constitutive electromagnetic properties of ferrite composites. When the Ni concentration is increased, the microwave return loss is greatly enhanced and the absorption band becomes narrower towards the lower frequency. The maximal return loss of single-layer absorbers composing of 7.2mm-thick ferrite composites with x=0.15 is estimated as −53.9dB with an absorption bandwidth 1.72GHz. Due to the decreasing products of matching thickness and frequency at maximal return loss, the incorporation of Ni fillers in ferrite composites facilitates to reduce the absorber thickness. Additionally, the microwave absorbing behaviors of double-layer microwave absorbers with different lamination sequences of Ni-encapsulated ferrite composites were also investigated.

A Simple Microstrip Bandstop Filter Using Cross-Coupling Stubs

This paper presents an alterative implementation of a shunt open-circuited stub for multilayer microwave circuit. With making use of the proposed implementation, a simple and compact bandstop filter with a district bandstop characteristics and a first spurious at the third harmonic is proposed. The proposed filter exhibits about 12.5% fractional bandwidth of −10 dB signal rejection at the center frequency of 2.04 GHz and flat group delay at the pass bands. Besides, by cascading a number of the proposed bandstop filters designed at the different frequencies, multiband bandstop filters can be easily realized. A dual- (tri-) band design at the center frequencies of 2 GHz and 3 GHz (and 4 GHz) is designed, realized, and measured. The proposed bandstop filter well suits the nowadays multilayer and compact radio frequency integrated circuit design.

A novel butterfly‐shaped multilayer backward microstrip hybrid coupler for ultrawideband applications

AbstractIn this letter, the numerical analysis and design of aperture‐coupled backward microstrip hybrid coupler for ultrawideband (UWB) multilayer microwave circuits are introduced. The proposed coupler is composed of two microstrip patches located on two stacked substrate layers. This coupler uses a broadside coupling via a rectangular‐shaped slot in the common ground plane (mid‐layer). To achieve broadband characteristics for UWB operation, butterfly‐shaped patches are used. The numerically simulated results using two simulation programs with two different numerical techniques show that the proposed coupler have good insertion losses (both through S21 and coupled S31) variation (less than ±2 dB) and high return loss S11 (greater than 14 dB) with acceptable isolation S41 (about 14 dB) over most of the 3.1–10.6‐GHz frequency band. A 3dB/90°‐backward hybrid coupler prototype is fabricated and then tested experimentally using Agilent E8364B PNA Network Analyzer. Experimental results agree well with the simulated ones. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2231–2237, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27092

Thin smart multilayer microwave absorber based on hybrid structure of polymer and carbon nanotubes

We present a thin and flexible multilayer solution for effective absorption of electromagnetic waves from 8 to 40 GHz and probably higher. Submillimetric conductive and dielectric layers based on polymer and carbon nanotubes are successively stacked. A smart gradient-periodic arrangement results in a very high absorption index despite overall millimetric thickness of the system.

Variations in Structural and Electrical Properties of Ba-Hexaferrite due to Pb Substitution

BaFe2-xPbxO9 (x=0.0 to 1.0) samples were prepared by co-precipitation method. All samples were sintered at 960±5°C for three hours. Structural properties were investigated by X-ray diffraction (XRD) and Scanning electron microscopy (SEM). Variation in structural parameters was calculated from XRD obtained data. SEM micrographs were used to study the morphology and grain growth. No regular increase or decrease in structural parameters and morphology is observed with increase in Pb content. For dc electrical characterizations, dc resistivity was measured as a function of temperature up to 750K. Data obtained was further analyzed and different dc parameters like activation energy and mobility were measured. For dielectric analysis, capacitance C was measured in the frequency range from 100 kHz to 3MHz. High dielectric constant for this material makes this material suitable for applications like multilayer capacitors (MLC), microwave devices and dynamic random access memory (DRAM).

Microstructures and Dielectric Properties of Ba1−xSrxTiO3 Ceramics Doped with B2O3-Li2O Glasses for LTCC Technology Applications

Ba1−xSrxTiO3 ceramics, doped with B2O3-Li2O glasses have been fabricated via a traditional ceramic process at a low sintering temperature of 900 °C using liquid-phase sintering aids. The microstructures and dielectric properties of B2O3-Li2O glasses doped Ba1−xSrxTiO3 ceramics have been investigated systematically. The temperature dependence dielectric constant and loss reveals that B2O3-Li2O glasses doped Ba1−xSrxTiO3 ceramics have diffusion phase transformation characteristics. For 5 wt% B2O3-Li2O glasses doped Ba0.55Sr0.45TiO3 composites, the tunability is 15.4% under a dc-applied electric field of 30 kV/cm at 10 kHz; the dielectric loss can be controlled about 0.0025; and the Q value is 286. These composite ceramics sintered at low temperature with suitable dielectric constant, low dielectric loss, relatively high tunability and high Q value are promising candidates for multilayer low-temperature co-fired ceramics (LTCC) and potential microwave tunable devices applications.

Microstructure and microwave dielectric properties of lead borosilicate glass ceramics with Al2O3

The effects of Al2O3 addition on both the sintering behavior and microwave dielectric properties of PbO-B2O3-SiO2 glass ceramics were investigated by Fourier transform infrared spectroscope (FTIR), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that with the increase of Al2O3 content the bands assigned to [SiO4] nearly disappear. Aluminum replaces silicon in the glass network, which is helpful for the formation of boron-oxygen rings. The increase of the transition temperature Tg and softening temperature Tf of PbO-B2O3-SiO2 glass ceramics leads to the increase of liquid phase precipitation temperature and promotes the structure stability in the glasses, and consequently contributes to the decreasing trend of crystallization. Densification and dielectric constants increase with the increase of Al2O3 content, but the dielectric loss is worsened. By contrast, the 3% (mass fraction) Al2O3-doped glass ceramics sintered at 725 °C have better properties of density ρ=2.72 g/cm3, dielectric constant ɛr=6.78, dielectric loss tan δ=2.6×10−3 (measured at 9.8 GHz), which suggest that the glass ceramics can be applied in multilayer microwave devices requiring low sintering temperatures.

Numerical analysis of transitions for multilayer microwave circuits designed on the basis of electromagnetic crystals

Characteristics of transitions designed for connection of electromagnetic-bandgap (EBG) waveguides situated in different layers of a microwave electromagnetic crystal are analyzed. Two types of transitions (with slot and probe coupling) are considered. Two operating modes of the transition with slot coupling, the propagation mode and the cutoff mode, are studied. It is shown that wider operating band of the device is ensured in the cutoff mode. The possibility of transition from one layer to another with simultaneous power division into two channels is studied.

Microwave dielectric properties and compatibility with silver of low-fired Ba2Ti3Nb4O18 ceramics with BaCu(B2O5) addition

The effects of BaCu(B2O5) (BCB) additions on the sintering temperature and microwave dielectric properties of Ba2Ti3Nb4O18 ceramic have been investigated. The addition of BCB can lower the sintering temperature of Ba2Ti3Nb4O18 ceramic from 1,250 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 5 wt% BCB added Ba2Ti3Nb4O18 ceramic sintered at 900 °C for 2 h exhibited good microwave dielectric properties of Q × f = 17,600 GHz, er = 38.2 and τf = 7 ppm/°C. The dielectric ceramic demonstrated stability against the reaction with the Ag electrode, which suggests that the ceramics could be applied in multilayer microwave devices requiring low sintering temperatures.