Due to their remarkable features, microstrip patch antennas are very attractive for many applications in modern communication systems. In addition to their ease of fabrication, they have low cost, low weight and can be integrated with other electronics. However, microstrip patch antennas in general suﬀer from surface wave excitation when they are mounted on a non-air substrate. Besides their contribution to power loss and reducing overall eﬃciency, excitation of surface waves eventually leads to undesired mutual coupling between elements of an array printed on the same substrate [1–4]. The diﬀraction of these surface waves at the edge of a ﬁnite-size ground plane results in a distorted radiation pattern. In addition, the presence of surface waves is usually associated with lateral waves, which reduce the accuracy of high-precision GPS receivers by causing low-angle interfering signals [5, 6]. Several designs have been proposed to suppress these undesired waves in microstrip patch antennas. In [7, 8], an annular ring patch with a properly adjusted shorted inner radius and open outer radius was proposed as a reduced surface wave antenna. The short circuit at the inner radius was achieved by using a high number of shorting pins. The same technique was used to design a dual-band microstrip patch antenna for high-precision GPS receivers . In [10–13], circular patches that include shorting pins were investigated using homogeneous dielectric substrates, without regard to the experimental realizability of the resulting designs. In this paper, we propose a simple design for a microstrip patch antenna with the ability to suppress surface wave and lateral wave excitation. The design procedure starts with designing a circular patch loaded with a single shorting pin on a grounded homogeneous dielectric substrate, as depicted in Fig. 1. To ensure that the design is experimentally realizable, an inhomogeneous substrate is used to produce an eﬀective relativepermittivity equivalent to the theoretically required value.
As mentioned above, almost all the MAs exhibit very thin vertical sizes, and the basic units of MAs also have very compact sizes compared to the operating wavelengths. However, for some speciﬁc applications (for examples, integrating into compact antennas/array or microwave integrated circuits for the purpose of reducing the coupling between adjacent elements), one needs ultra-compact embedding media so that they can be considered as fully homogenized media and will not induce side eﬀects in the whole system. Quite recently, two works are reported to achieve ultra-compact MAs by using a substrate of high dielectric constant  and a two-layer design . The former one uses a substrate with relativepermittivity r = 100 which is of high-cost and diﬃcult to be fabricated in practical. Most importantly,
The geometric configuration of the proposed ground plane slot resonator is shown in Fig. 1. The structure consists of a 50 Ω microstrip line on the top layer and a rectangular slot is etched in the ground plane of substrate. Two metallic plates forming a parallel plate capacitor is soldered with the ground plane across the ground slot. The low loss dielectric material could be placed between two metallic plates to increase the loading capacitance. The maximum electric field in the slot is at the centre of the slot; where parallel plates are soldered.
deal with lower permittivity. Most other integrated antennas perform poor on highpermittivity substrates due to field trapping effects, so that the slab mode antenna provides an alternative. It is furthermore compatible to relative thick substrates, which are easier and therefore cheaper to handle during production. Radiation occurs in end-fire direction, i.e. parallel to the substrate plane, which may be desired in many cases of product integration. There are very few antenna designs having the same characteristic. Due to its simple construction and very low conductor loss, the dielectric slab mode antenna can be a practicable option up to terahertz frequencies.
11) Design Dk is determined by testing thick microstrip transmission line circuits and reporting the thickness-axis dielectric constant of the raw material without the influence of copper. For more information, refer to the article on the Rogers website titled "The Influence of Test Method, Conductor Profile, and Substrate Anisotropy on the Permittivity Values Required for Accurate Modeling of High Frequency Planar Circuits" which was featured in a publication Sept. 2012. http://www.rogerscorp.com/acm/articles.aspx 12) Testing conditions: 24 hours @ 23 C, specimens etched free of copper
Abstract—This paper presents a design of perforated nanoantenna reflectarray. The use of metallic nanostructures made of Silver and/or Gold at appropriate wavelength cause fascinating unusual electromagnetic effects. Reflectarray consists of an array of unit cell made from Silver is investigated. The effect of the number of perforated holes in the unit cell configurations is investigated for proper reflection coefficient phase compensation. A linearly polarized pyramidal nano- horn is used to feed the perforated nanoantenna reflectarray. The radiation characteristics of 9 × 9 perforated nanoantenna reflectarray are illustrated. A high gain of 20.5 dB is obtained at the designed frequency of 735 THz. A comparison between solid Silver sheet with no perforation holes and the proposed perforated reflectarray is explained.
Microstrip antennas are in greater demands in wireless communication and space applications because of small size, low weight. The microstrip antennas possess the shortcomings such as narrow bandwidth, low gain and poor efficiency . These shortcomings can be overcome by using multilayered rectangular microstrip antennas. This can be achieved by proper combination of the substrate and superstrate thickness over and under the patch. Multilayer Microstrip patch is also useful to provide protection to patch from heat, rain, physical damage, and naturally formed ice layers during flight . There are many methods available in the literature to calculate the resonant frequency of multilayered rectangular patch based on numerical technique . None of the efficient analytical model is available in literature related to multilayered structure to obtain the antenna dimension. There are mainly four techniques for enhancement of Bandwidth of given Microstrip Patch Antenna. Which are, multilayered configurations of Broadband Microstrip patch antenna, Stacked Multiresonator Microstrip patch antenna, Modified Shape Patch Broadband Microstrip patch antenna, Planar Multiresonator configuration of Broadband Microstrip patch antenna, in multilayered configuration patches are placed over different dielectric substrates and they are stacked on each other. Based on the coupling mechanism, these configurations are of two types electromagnetically-coupled or aperture-coupled. There are mainly two method of coupling to multilayered antenna, Electromagnetically-coupled Technique and Aperture-coupled Technique. In Stacked Multiresonator Microstrip patch antenna configuration multiresonator and stacked configurations are combined to provide broadband microstrip patch antenna. This antenna is applicable for wireless communication such as WLAN. A single line feed stacked microstrip antenna for 4G system is presented and performance of proposed antenna improvement of bandwidth 15% .
The electrical properties that are of major importance to the operation and lifetime of many electrical components and systems include the relative dielectric constant and relativepermittivity, these properties are dependent on the chemical composition of the dielectric, they usually suffer degradation after electrical deterioration has taken place. The aim of this paper is to use the change in electrical properties with radiation dose to design polymer dosimeter. The experimental results show an improvement the relativepermittivity of the medium decreased except for PE sample which increased when the total irradiation dose of gamma rays was increased whereas the relative dielectric constant increased for all PVC samples. The predominance of cross-linking results shows linear relations between relativepermittivity and relative dielectric constant versus absorbed dose of gamma rays source. These relationships between these properties and dose level can be utilized as measuring tool (Dosimeter) for radiation exposure that incident on the PVC samples.
A broadband feeding technique for the uniplanar TSA on low-permittivitysubstrate is presented. With a substratepermittivity of 2.2 it is possible to establish a good trade- off between radiation characteristics and losses in the feed system. It is demonstrated that low loss, low input reflection coefficient and sufficiently suppressed cross- polarization characteristics are attainable over an ultra- wide bandwidth in extent of 100 percent. Additionally, the TSA system shows sufficient gain values and direc- tivity considering the wide 7 GHz bandwidth. Measure- ments on a prototype TSA system validate the design process, thus providing a solution for future UWB appli- cations of the uniplanar tapered slot antenna in commu- nications or radio astronomy applications.
In 1970, Dr B. Mandelbrot coined the term Fractal. Fractal symbolises broken or irregular fragments. He investigated the relationship between fractals and nature using discoveries made by Gaston Julia, Pierre Fatou, and Felix Hausdorff . He was able to show that many fractals exist in nature and can be used to accurately model certain phenomena. Fractals are a class of shapes which have no characteristic size.Each fractal is composed of multiple iterations of a single elementary shape. The iterations can continue infinitely, thus forming a shape within a finite boundary but of infinite length or area. Fractals describe a family of complex shapes that possess an inherent self-similarity in their geometrical structure. Fractal has various properties like recursive, infinite; space filling and self-symmetry Because of these properties fractals antenna have more resonant frequency which contributes to lower return loss.Therefore less power is reflected back to the source and radiation emission is stronger. Fractal antennas are based on the concept of a fractal, which is a recursively generated geometry that has fractional dimensions.. The paper has been organized into following sections. Section 2 includes the design and simulation results of reference antenna . Section 3 includes a modified compact fractal monopole planar antenna which is designed by combination of GiusepePeano and Sierpinski Carpet fractal geometries on a substrate with permittivity Є r = 4.4, height = 1.6mm.
constant values. Hence, stacking alignment issue does not impose a problem. Also, antenna’s impedance and axial ratio bandwidth values are significantly higher than the results presented in . In other words, with the help of conventional stacking and suitable selection of dielectric substrate parameters, the axial ratio bandwidth of antenna reported in  can be increased from 4.7% to 16%, and impedance bandwidth from about 55% to more than 100% at the expense of increased height. However, this configuration is more useful where size is not the prime constraint.
and the permittivity at optical frequency, m , which was by square of the refractive Index for sodium D- line, for ester – amine mixtures, are used to evaluate Kirkwood linear correlation factor, excess permittivity, Bruggeman factor and dipolar excess free energy of mixing.
The first step in deposition is to cut the foil substrate to a manageable size, in this case, approximately 2 inches by 2 inches for copper and 1 cm by 1 cm pieces for platinum. The foil is then taped, along two opposite edges, to a round 3” diameter fused silica substrate which is placed on a Cookson Electronics P-6000 spin coater chuck and secured by vacuum. Prior to spinning, the surface of the foil is completely covered with the final solution by dripping the solution on the foil from a 3 ml Becton- Dickinson syringe that employs a 0.2 micron filter (Fisher Scientific). The foil is spun for 30 seconds at 3000 rpm. The substrate is immediately removed from the spin coater and glass mount and placed directly onto the surface of a 250 °C Mirak Thermolyne hotplate for 5 minutes for solvent evaporation and initial gel formation. This process, which can be seen in figure 2.2, is repeated several times to reach the desired film thickness. Each spun-on layer produces approximately 100 nm of crystallized BaTiO 3 film. For these experiments, the process was repeated 6 times for a
central Gaussian spot to be normally incident on the planar face of the fused quartz MLA substrate. A caldera-like MLA was used in conjunction with a 2x microscope objective (Mitutoyo M Plan Apo 2, NA 0.055, working distance 34 mm) to focus the incident wavefront onto a dot array. The microscope objective was coupled to a high resolution monochrome CMOS camera (Basler acA2500-14gm, 2592 × 1944 pixels, 2.2 µm × 2.2 µm pixel size) by a Navitar 6.5x ultra-zoom lens. The microlens array was mounted onto a micrometer translation stage oriented along the direction of laser propagation and was positioned in front of the virtual focal plane so that the camera recorded an array of focused laser dots. The air in between the collimating lens and the microlens array was perturbed using short sprays of a canned air duster (Miller-Stephenson MS-222N containing 1,1,1,2- Tetrafluoroethane). The duster sprays were oriented perpendicular to the optical axis to avoid physical movement of the optical components. Since the shifts in dot array position were minuscule, the recorded video of the focused dots evolving under the air perturbation was processed using ImageJ in two steps. Firstly, an image of the dot array positions under stationary experimental conditions was subtracted from each frame in the video to accentuate the spatial displacement of each focused beam. Only focused dots that were displaced from their equilibrium positions were visible after this step. Secondly, the subtracted images were thresholded at the same level and converted into binary masks for improved contrast. Fig. 6.8(d) is an example of the perturbed dots after they have been processed, showing the location of the air perturbation. In Fig. 6.8(e) you can see the regular array of focused spots when there is no perturbation in the system which is subtracted from each video frame.
ABSTRACT: The bandwidth and efficiency of folded rectangular patch antenna can be improved by addition of superstrate layer over the substrate of folded rectangular patch antenna results the multi dielectric layer microstrip folded patch antenna. The superstrate layer act as a part of the folded patch antenna. Design of folded rectangular patch antenna with different multidielectric layer can improves the gain and antenna efficiency of the antenna. With right choice of the thickness of substrate and superstrate layer, significant increase in gain can be achieved for practical applications. Multidielectric layer microstrip antenna designed for applications where various physical properties of antenna such as permittivity, patch dimensions, height of the substrate and the resonant frequency can be analyzed. The antenna performances can been evaluated for variety of cases of permittivity and thickness of the superstrate layer.
orientation. Dielectric materials ordinarily exhibit at least one of the mentioned polarization types depending on the material and also the manner of the external field application (Kuntaman and Ayten, 2002; Kittel, 2005), polymers such as polystyrene and PTFE, have no polar groups so its permittivity reflects the displacement of electrons relative to nuclei, i. e., electronic polarization when an AC electric field is applied (Kuntaman and Ayten, 2002). The decrease of relativepermittivity with increasing frequency due to the dielectric dispersion as a result of the lag of molecules behind the alternation of the electric field at high frequency, i. e., there is no enough time for molecules to follow the alternation of the electric field at high frequency (rapid phase orientation) (Nada et al., 2004). The total variation of relative dielectric constant against frequency and temperature is small, its value ranges between 1.766 and 1.789 and this is due to the nonpolar nature of PTFE and in this polymer the electronic polarization is dominant and occurs during a very short interval of time (of order of 10-15 sec.), (Khare and Sandeep, 2000). In general, the variation of relativepermittivity with temperature is different depending on the polarity of the polymers. For nonpolar polymers the relativepermittivity is known to be slightly affected by temperature as depicted in Fig. 2 ; but in the case of strong polar polymers is completely different, that is, the relativepermittivity increases as the temperature increases (Wong, Youterson and Sutherland, 2005). The dielectric loss versus frequency at different temperatures for commercial PTFE are presented in Fig. 3.
complex permittivity and permeability are needed, for the good impedance matching and attenuation of the composite film depend on the value of relative complex permittivity and permeability at a given frequency and thickness . CIP is a kind of traditional ferromagnetic absorbing materials with proper value of relative complex permittivity and permeability [16,17]. Traditionally, the investigation of electromagnetic wave absorbing properties of microwave absorbers made from particles dispersed in polymer matrix focused on the achievement of strong absorption with a thickness of more than1mm [12-14, 18, 19]. However, it is better for practical application as microwave absorbers with thinner film thickness. To our best knowledge, there has no report on the influence of external magnetic field on the microwave absorbing properties during preparation process of magnetic particles and polymer composites film with the film thickness less than 1mm. In this study, we prepared thin and flexible films of carbonyl iron particles (CIP) and polychloroprene composites (CIP/CR) with thickness of 0.54mm under external magnetic field supplied by coils, and study the effect of the anisotropy and the particles dispersion uniformity in the matrix on the microwave absorbing properties.
Figure 7 shows the relationship between relative permit- tivity of concrete on the older bridges and the relative humidity measured at the weather stations near the bridge locations by Korea Meteorological Administration. It has been reported that the relativepermittivity of geo-materials (e.g., clay and silty soils) shows a non-linear reduction when moisture content falls to the level of dry conditions. This is because water molecule mobility is restricted by interaction with the surface charges of the concrete aggregates (Saarenketo 1998). In this study, an exponential curve was used to describe the non-linear behavior of the relativepermittivity in relation to the water content in the concrete. In the ﬁgure, data from different expressways are repre- sented with different symbols, and the best ﬁtted lines for each expressway route were obtained from non-linear regression analyses. Table 3 summarizes the numerical equations for best ﬁt curves and R-squares. Interestingly, the three best-ﬁt curves were close to each other, which con- noted that the effect of different expressways did not much affect the effect of relative humidity of air on the relativepermittivity of concrete in bridge decks.
Equation (17) can be used to calculate either the resonant frequency of the split-cylinder resonator given the substratepermittivity or the substratepermittivity given a measured resonant frequency. To solve Eq. (17) we can take advan- tage of the peculiarity that det [ Z ] alternates between purely real and purely imaginary values whereas the nonzero part crosses the zero line at the resonance, as demonstrated in Fig. 2 for the order combination (m = 0, n = 1). This allows for a fast and coarse detection of zeroes over the whole fre- quency range in a first step. Subsequently, the detected zeroes can be located more accurately by applying root determining methods like the method of false position (regula falsi).