Chemical sensor based on a novel capacitive microwave flexible transducer with polymer nanocomposite-carbon nanotube sensitive film

Microsystem Technologies - This study presents the results on the feasibility of a resonant planar chemical capacitive sensor in the microwave frequency range suitable for gas detection and...     

Shape optimized design of microwave dielectric resonators by level‐set and topology gradient methods

The finite element method is coupled with the topology gradient (TG) and level‐set (LS) methods for optimizing the shape of microwave components using a computer‐aided design model. On the one hand, the LS approach is based on the classical shape derivative; while on the other hand, the TG method is precisely designed for introducing new perturbations in the optimization domain. These two approaches, which consist in minimizing a cost function related to the component behavior, are first described. Regarding given electrical specifications, these techniques are applied to optimize the distribution of ceramic parts of a dual‐mode resonator in order to improve its behavior. The optimized dielectric resonators result in a wide spurious‐free stop band. A comparison between classical and optimized dual mode resonator is presented. Theoretical results are then validated by careful measurements. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.     

Development of an electromagnetic tool for the accurate synthesis of manifold multiplexers: The dynamic inverter

This article presents an electromagnetic tool for the synthesis of manifold multiplexers — the dynamic inverter. By associating this model with the classical circuit model of the filter, the broadband behaviour of each filter can be analysed rapidly and then optimised accurately for an efficient synthesis of the manifold multiplexer. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

A general procedure for the design of bulk acoustic wave filters

This article presents a procedure for the design of bulk acoustic wave (BAW) filters. The procedure consists of optimizing the modified Butterworth‐Van Dyke model of each resonator, considering appropriate technological parameters. The approach is demonstrated first to design a classical aluminum nitride‐based BAW filter but remains valid for other piezoelectric layers, considering either longitudinal or transverse acoustic wave coupling. The approach is finally applied to the design of a lithium niobate (LiNbO₃) BAW filter for wide‐band filtering applications. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

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.     

Computer aided design for new microwave filter topologies for spatial applications in Ka band

This paper presents, in the first part, an original topologie of dielectric resonators for multilayer filter applications in Ka band. The resonant element is defined by a partially metallized dielectric plate enclosed in a parallelepipedic cavity. This topology allows a high integration in a planar environment type and presents high electrical performances too. It is easily manufactured, and suitable for high frequencies filtering and power applications. In order to realize multipole filters without tuning, a direct electromagnetic optimization method developed in our laboratory is applied. This method combines a electromagnetic software based on the finite element method, and a specific one to establish the identified coupling matrix deducted from the filter responses. Some experiments are performed to verify the theoretical design. In the second part, we consider a new global function which combines filtering and radiating characteristics. For the first time, an opened tuning less two-pole filter defined by two superposed resonators coupled by a metallic iris is designed. Its filtering and radiating functions are optimized in the same time to present required electrical performances.     

Asymptotic properties of estimates for unknown parameters of almost periodic functions under Gaussian noise

Sufficient conditions of strong consistency are established. Asymptotic distributions of estimates for unknown parameters of an almost periodic function are found in a nonlinear regression model with continuous time and random noise. The noise is assumed to be a weakly dependent Gaussian stationary process.     

Optimization of microwave devices combining topology gradient and genetic algorithm

Topology optimization can be seen as optimizing a distribution of small topological elements within a domain with respect to given specifications. A numerical topology gradient (TG) algorithm is applied in the context of electromagnetism for optimizing microwave devices, computing the sensitivity on adding or removing small metallic elements. This method leads to an optimum topology with very little initial information in acceptable time consumption. The method is applied to the design of a microstrip component in which the topology gradient is directly used as a direction of descent. However, in some ill‐behavior problems, topology gradient is not sufficient to converge to the global optimum. In the latter case, the basic TG is coupled with a genetic algorithm (GA) to make a more suitable algorithm for solving local optima problems. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Ozonation of a landfill leachate: evaluation of toxicity removal and biodegradability improvement

This work shows an evaluation of treatments for the leachate produced at the Gramacho Municipal Landfill in Rio de Janeiro state, Brazil. This leachate has very peculiar characteristics, with a high salinity level and very low biodegradability (BOD(5)/COD of 0.05). A sequence of processes was employed in the treatment of this leachate. Initially, a physicochemical treatment was used, while the second stage consisted of application of ozone to improve the biodegradability of the leachate. The final stage comprised a biological treatment. The physical-chemical treatment led to COD and DOC removal levels of 40 and 25%, respectively, with the use of Al(2)(SO(4))(3). The sequence of treatments proposed brought good results, with an increase in the BOD(5)/COD ratio from 0.05 to 0.3 after ozonation. The toxicity tests performed using Brachydanio rerio and Poecilia vivipara showed that the toxicity of the leachate had hardly been reduced by ozonation. These results are in agreement with the fact that, despite the higher BOD(5)/COD ratio, the biological process did not present a good performance. The total average removal levels of COD and DOC achieved using the combined treatment were 73 and 63%, respectively, for an ozone dose of 3.0 gL(-1) by the leachate.     

Effect of nano aluminum nitride filler on mechanical,thermal, and dielectric properties of the glass/mullite composites for low-temperature co-fired ceramic applications

Mullite/glass/nano aluminum nitride (AlN) filler (1–10 wt% AlN) composites were successfully fabricated for the low-temperature co-fired ceramics applications that require densification temperatures lower than 950°C, high thermal conductivity to dissipate heat and thermal expansion coefficient matched to Si for reliability, and low dielectric constant for high signal transmission speed. Densification temperatures were ≤825°C for all composites due to the viscous sintering of the glass matrix. X-ray diffraction proved that AlN neither chemically reacted with other phases nor decomposed with temperature. The number of closed pores increased with the AlN content, which limited the property improvement expected. A dense mullite/glass/AlN (10 wt%) composite had a thermal expansion coefficient of 4.44 ppm/°C between 25 and 300°C, thermal conductivity of 1.76 W/m.K at 25°C, dielectric constant (loss) of 6.42 (0.0017) at 5 MHz, flexural strength of 88 MPa and elastic modulus of 82 GPa, that are comparable to the commercial low temperature co-fired ceramics products.