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3D Hilbert resonator, although covering larger substrate area then other configurations, demonstrated very high values of unloaded Q. Simulations have shown that this advantage can further be exploited by decreasing line widths and spacing in the 3D curve, which can be easily done with LTCC technology. CONCLUSIONIn this paper, four novel multilayer microstrip resonators were analyzed via full-wave EM simulations and compared in terms of loaded and unloaded quality factor. All the dimensions were kept in accordance with standard TF procedure.The 3D Hilbert resonator was shown to be superior to all the other configurations examined, both 3D and 2D, thus demonstrating the benefits to be gained from the employment of multilayer fractal shapes in resonators and filters. [5]. In this paper, we propose a novel rectangular slot antenna embedded with a pair of narrow rectangular strips for dual-broadband operation in WLAN communication. Probably due to the narrow strip embedded symmetrically along the center line of the rectangularslot antenna, a new resonant mode close to the second resonant mode of the regular rectangular-slot antenna can be excited to enhance the operating bandwidth of high band, which simultaneously covers the required bandwidth of 5.2 GHz (5.15-5.35 GHz) and 5.8 GHz (5.725-5.825 GHz). It is found that by properly adjusting the spacing between the two narrow strips to be 2 mm, the obtained bandwidths for the 2.4-and 5-GHz bands are 11% (254 MHz) and 24.8% (1446 MHz), respectively, which is sufficient for wireless communication. The proposed dual-broadband rectangular slot antenna also provides the frequency ratio of two operating modes in the range of 1.66 -2.52 with various spacings between the two narrow strips, which is wider than that of the dual-broadband slot-antenna design [5]. The details of the proposed slot antenna designs are described, and the experimental results for the dual-broadband performance obtained are presented and discussed. ANTENNA DESIGNAs shown in Figure 1, a pair of narrow rectangular strips of width b and the length T is embedded symmetrically along the center line of the rectangular slot antenna. The spacing between the two rectangular strips is denoted as S here. The rectangular slot antenna of L ϫ W is etched on an inexpensive FR4 substrate with dielectric constant r (4.4) and substrate thickness h (0.8 mm). In this study, due to the presence of the embedded rectangular strips with less spacing, a new resonant mode close to the second resonant mode of the rectangular slot antenna can be easily excited in order to obtain the desired dual-broadband operation, for example, the WLAN operations in the 2.4-and 5.8-GHz bands. However, the fundamental resonant mode of the proposed slot antenna is less perturbed. And, as the spacing between two narrow strips is more than half of the length of the slot antenna, both of the two operating frequencies increase when the spacing is increased in order to obtain a different operating-frequency-variation trend, compared with the propo...

This paper investigates the Lamb wave generation by the surface bonded circular piezoelectric (PZT) actuator and wave propagation within the orthotropic Carbon Fiber Reinforced Plastic (CFRP) plate considering the anisotropy of the elastic and damping properties of the materials; existence of the adhesive layer; and dependence of the interfacial stress distribution on the surface between host plate and actuator, on the anisotropy of the plate material, and on the excited frequency, wavelength and plate thickness. This part of our investigation includes FE based study of the shear stress distribution on the interface between circular PZT actuator and surface of orthotropic CFRP plate, and its dependence on the excited wavelength and plate thickness. The anisotropic elastic and damping properties of the plate material, which are used in the implemented finite element (FE) model, have been preliminary determined in the first part of our investigation. We compare the behavior of the wave generation, propagation and attenuation that are studied using this model with the similar dependencies obtained at the simulation of the non-dissipating plate excited by the periodical radially oriented force, which is distributed along the circumference bounding the actuator, i.e. 3D pin-force excitation case. The proposed results can be used at the design of SHM for the composite structures with the structural anisotropy and damping, and at making a reasonable choice of the frequency, type, dimensions and optimum placement of the actuators and sensors.

The increasingly widespread use of vacuum assisted technologies in the manufacture of polymer-composite structures does not always provide the required product quality and repeatability. Deterioration of quality most often appears itself in the form of incomplete filling of the preform with resin as a result of the inner and outer dry spot formation, as well as due to premature gelation of the resin and blockage of the vacuum port. As experience shows, these undesirable phenomena are significantly dependent on the location of the resin and vacuum ports. This article presents a method for making a decision on the rational design of a process layout. It is based on early forecasting of its objectives in terms of quality and reliability when simulating its finite element model, on the correlation analysis of the preliminary and final quality assessments, as well as on the study of the cross-correlation of a group of early calculated sub-criteria. The effectiveness of the proposed method is demonstrated by the example of vacuum infusion of a 3D thin-walled structure of complex geometry.