## No full-text available

To read the full-text of this research,

you can request a copy directly from the author.

In this chapter we describe the characteristics of cylindrical microstrip antennas excited by a coax feed or through a coupling slot fed by a microstrip feed line. Typical types of rectangular, triangular, circular, and annular-ring microstrip antennas are analyzed. Characterization of curvature effects on the input impedance and radiation characteristics is of major concern. Calculated solutions obtained from various theoretical techniques, such as the full-wave approach, cavity-model analysis, and the generalized transmission-line model (GTLM) theory, are shown and discussed. Some experimental results are also presented for comparison.

To read the full-text of this research,

you can request a copy directly from the author.

... Cylindrical arrays are commonly used due to the possibility of both elevation and azimuth steering, by phase control of the excitation of elements. Applications include antennas in mobile base stations, radar, satellite communications, rockets, and remote sensing [1,2]. Conformal microstrip antennas have been studied using several techniques [1,2]; including cavity method [3][4][5], the Green's functions method [6], the electric surface current method [7,8], and full-wave methods like the method of moments (MoM) [9]. ...

... Applications include antennas in mobile base stations, radar, satellite communications, rockets, and remote sensing [1,2]. Conformal microstrip antennas have been studied using several techniques [1,2]; including cavity method [3][4][5], the Green's functions method [6], the electric surface current method [7,8], and full-wave methods like the method of moments (MoM) [9]. Cavity method determines an approximation of the field distribution in the cavity below the patch, and uses equivalent surface current distributions to obtain the radiation fields, ignoring the dielectric layer. ...

... where G zϕ (1) (ρ, n, k z ) stands for the Green's function for the zcomponent of the electric field in the substrate, due to a ϕ-directed electric dipole and similarly, for the others. Details for obtaining the Green's functions are presented in the Appendix. ...

This study presents a full-wave solution for arrays of cylindrical-rectangular microstrip antennas, with superstrate. It uses the method of moments (MoM), with full-domain basis functions. The same set of functions is used as testing-functions resulting in a Galerkin procedure. A numerical procedure is presented allowing an efficient and numerically stable evaluation of the elements of the MoM linear system. Results for input impedance are compared to those using HFSS for a flush-mounted geometry. Results for radiation pattern, mutual impedance, and coupling coefficient S12 are also presented. And the effects of the superstrate on those parameters are evaluated.

... By optimizing its distinct features, these antennas will become a major driving factor in designing the futuristic singly or doubly curved communicating devices. The microstrip patch antennas mounted on a singly concave or convex curved surfaces such as circular cylinder geometry are an important class of applications where a wide area coverage or high directive beam is desirable [1,2]. In some of the specific high end applications, the casing of a conformal antenna array is desirable, and here a dielectric material is considered as a protective layer. ...

... where, E P (φ, z) is the electric field due to the patch current and E F (φ, z) the electric field due to the feed with the patch being absent. These unknown parameters need to be solved, and then the input impedance, radiation pattern, etc. can be calculated [1,3]. The close proximity between the patch and the ground plane suggests that for a cylindrical microstrip structure, the electric field has only aρ component, and the magnetic field has onlyφ andẑ components in the region bounded by the patch and the ground cylinder. ...

... where [U ] is a unit matrix of order 2 × 2, and Z 0 is the characteristic impedance of the inset feeding (assumed to be 50 Ω here method technique [1] can be used: ...

... In many applications, patch antenna model is generally enclosed by a dielectric cover for protection and stealth purposes. The loading and bending of the dielectric superstrate affects the characteristics of a curved patch antenna profoundly [1][2][3][4]. The effectiveness of this dielectric cover can be enhanced further by satisfying the resonance condition which is at a quarter wavelength air gap from the antenna element. ...

... Now, an alike cylindrical superstrate with a thickness of R 4 < ρ < R 5 is spaced off up to R 2 < ρ < R 4 air gap with the region denoted as Section 4. The outermost area ρ > R 5 is the free air space with permittivity ε 0 designated as Section 5. Initially, the field components in the respective sectors (where the media is changing) are determined by applying the boundary conditions at various sectors for the tangential electric and magnetic fields. Assuming a time harmonic dependence of (−e jωt ), the z components of the electric and magnetic fields in the qth sector for q = 1, 2, 3, 4 can be expressed in a cylindrical coordinate system (ρ, φ, z) as [1,5,9] ...

... The maximum value of Eq. (7) is defined as rectangular microstrip antenna directivity [1]. Similarly, the other parametric values like gain, return loss, and bandwidth can be determined [4,11]. ...

A microstrip patch antenna can be readily installed on any non-planar surface due to its conformal property, and this feature enhances its applicability in many areas. Moreover, in some specific applications, it is desirable and mandatory to provide protection of antenna from the unfriendly surroundings. Therefore, the present work focuses on the antenna with a dielectric cover and analyzes its effect on directivity, gain, and bandwidth at various superstrate air gaps. Two antenna models of single and dual elements are considered here separately, and both are conformal to the cylindrical surface. The antenna parameters are studied under varying superstrate gaps with equal intervals up to a quarter wavelength under fixed cylindrical curvature. It is noted that there is a significant improvement of 6% and 12% in bandwidth at quarter wavelength gap as compared to simple single and dual antenna models without dielectric loading, respectively. Also, both the calculated and measured results show the other important constructive effect of superstrate on the antenna performance.

... Reported research based on conformal patch antennas have demonstrated that the performance parameters of antennas are affected by feeding technique/method [8][9][10][11][12] This present research work has analyzed the design and simulation of inset feed cylindrical surrounding patch antenna obtained from a conformal rectangule shaped planar-patch antenna at 1.8 GHz frequency band for mobile communication and automotive applications where antennas have to be integrated on curved surfaces. The approach takes into account the effect of curvature radius (r) on return loss (S1,1), impedance Band Width (BW), Voltage Standing Wave Ratio, and the E-and H-plane radiation patterns of the antennas [11][12][13][14][15]. This research work has resolved the limitations of coaxial, probe and proximity feeding techniques and has justified that microstrip inset-feed technique can mitigate the shortcomings of other feeding methods. ...

... The optimized physical dimension details of the designed rectangular planar patch antenna as shown in Figure 1 has been calculated by transmission line method by the use of (1) to (5). Table 1 depicts the complete details of the physical dimensions of the rectangular planar patch antenna [14][15][16]. The width of the patch (wp) is: ...

... The farfield radiation pattern is the plot of the farfield properties as a function of spatial co-ordinates specified by elevation angle (θ) and azimuth (ϕ) or can be defined as plot of power radiated per unit solid angle [11,14,15]. It could be in polar, Cartesian, 2D or 3D graph. ...

In this research work, a Cylindrical Surrounding Patch Antenna (CSPA) with improved performance parameters based on inset feed method compared to other feed techniques has been proposed for 1.8 GHz applications. The designed and simulated CSPA is a rotary version of an initially designed Rectangular Planar Patch Antenna (RPPA). The RPPA is mounted on a cylindrical surface with radius (r) 10 mm which is an increased curvature for better -10 dB S-parameter (S11), impedance Band Width (BW), Voltage Standing Wave Ratio (VSWR), radiation pattern, and gain. The copper radiating patch has been conformed on the surface of the grounded flexible polyimide substrate with relative permittivity (εr) 3.5 and thickness (h) 1.6 mm at normalized input impedance of 50 Ω. Results for the RPPA and the proposed CSPA have been compared with existing designs in terms of antenna size, resonant frequency (fr), return loss (S11), and gain while taking cognizance of the feeding techniques. The S11, BW, VSWR, and gain are -12.784 dB, 28 MHz, 1.8, and 4.81 dBi respectively for the rectangular planar patch antenna and -35.571 dB, 66 MHz, 1.5, and 3.74 dBi, respectively for the cylindrical surrounding patch antenna.

... Owing to their electrical and mechanical attractive characteristics, conformal microstrip antennas and their arrays are suitable for installation in a wide variety of structures such as aircrafts, missiles, satellites, ships, vehicles, base stations, etc. Specifically, these radiators can become integrated with the structures where they are mounted on and, consequently, do not cause extra drag and are less visible to the human eye; moreover they are lowweight, easy to fabricate and can be integrated with microwave and millimetre-wave circuits [1,2]. Nonetheless, there are few algorithms available in the literature to assist their design. ...

... Once the array elements are chosen and their positions are predefined, to determine the vector v (θ , ϕ) tor v(θ,ϕ) it is necessary to calculate the complex patterns g n (θ,ϕ), 1≤n≤N, of the array elements. For conformal microstrip arrays there are some well-known techniques to accomplish this [1], for example, the commonly used electric surface current method [17][18][19]. However, when this technique is employed to analyse cylindrical or conical microstrip arrays, for instance, it cannot deal with the truncation of the ground layer and the diffraction at the edges of the conducting surfaces that affect the radiation pattern. ...

... Though planar and conformal patch antennas share some common advantages (low profile, light weight, mechanically robust on host surfaces, versatile in terms of polarization, cheap to fabricate with modern printed circuit technology) conformal patch antennas are the focus of recent research and applications [2], [3], [7]- [9]. Conformal patch antennas are preferred to their planar patch counterparts because they exhibit versatile performance parameters such as better bandwidth, gain, directivity, ominidirectionality, enhanced integrated non-obstructive designs, reduced aerodynamic drag, and good azimuth coverage [1], [3], [8], [10]- [12]. ...

... It changes the resonant frequency (f r ), return loss (S 11 ), radiation pattern, bandwidth (BW), and voltage standing wave ratio (VSWR) of the antenna. The conformal antenna designs are capable to circumvent the performance degradation, if the bendability parameters such as the curvature radius (r), bending angle (θ), and substrate thickness (t s ) are critically considered [8]- [10]. Various physical parameters and dimensions of the antennas have been presented in Fig. 1. ...

... In the era of communication modernisation, microstrip antenna plays a deciding role due to its multitasking potentials and finds new opportunities in many applications. In continuation, active research works are reported by many agencies in the area of non-planar surfaces [1][2][3][4][5][6]. The recent developments in MTM and SIW in the microstrip antenna have received increased interest and are utilized as an integrated part of cylindrical surface/device [7][8][9][10][11]. ...

... The transverse field components in the ith region can be obtained from E iz and H iz . Using the exact Green's function approach and applying boundary conditions, the far zone field components and other parameter can be determined [1,4,6]. (ii) The split rectangular ring resonator (SRRR) and strip wire on either side of the substrate for achieving MTM and placement of metallic vias for SIW technology are to be calculated and designed using standard design procedures [14,17,19]. ...

Conformability helps microstrip antenna to mount on any geometry platform and can also be used for multiple frequency systems without any complexity. The designing of a frequency reconfigurable antenna conformal to cylindrical surface using the combination of metamaterial (MTM) and substrate integrated waveguide (SIW) is proposed. The single and dual antenna models resonate at various frequencies of C-band by means of changing the cylindrical curvature. The results also show a considerable improvement in bandwidth and gain for dual antennas as compared to the single antenna. The antenna parameters are simulated on HFSS tool, and validation process is done by experimental setup.

... The primary differences between the two frequencies are the range (coverage) and band-width (speed) that the bands provide. The 2.4 GHz band provides coverage at a longer range (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30) but transmits data at slower speeds. The 5 GHz band (10-15 Ft) pro-vides less coverage but transmits data at faster speeds. ...

... As a result, 2.4 GHz band has become standard and all Wi-Fi enabled devices can use this network. Therefore, 2.4 GHz band will be used in this research [19][20][21][22][23][24][25][26][27][28]. ...

... Let we have a curved rectangular patches embedded at that are uniformly periodic with periodicity T φ and T z in φand z-directions respectively, as shown in Fig.1. The Z-components of the scattered electric and magnetic fields in each region due to the induced surface currents J z and J φ on the conductor surface can be expressed as [6], ...

... Once E z and H z are known, the scattered field components of E ρ , E φ , H ρ and H φ in each region can be obtained through the following expressions [6], ...

... It has been only very recent in human history that the electromagnetic spectrum, outside the visible region, has been employed for communication, through the use of radio. One of humankind's greatest natural resources is the electromagnetic spectrum and the antenna has been instrumental in harnessing this resource [1][2][3][4][5]. The IEEE 802.11b and IEEE 802.11g standards utilizes the 2.4 GHz ISM Band. ...

... The length and width of rectangular patch antenna are calculated from below equations .Where c is the velocity of light, ε r is the dielectric constant of substrate [1]. ...

A wide band microstrip antenna for various wireless applications such as WLAN/WiMax having satisfactory radiation characteristics is presented. The proposed antenna has wide bandwidth of 63.81% covering the range of frequency 1.435-2.780GHz. The return loss bandwidth and radiation performance of the antenna are examined by IE3D simulation software.

... In the early 1970s, the microstrip patch antennas were used in missiles and aircraft using printed circuit technology. Then, it adds a new dimension in antenna research sector [4]. The use of printed circuit technology makes an evolution in the development of microstrip patch antennas and they become an exciting research interest to the antenna researchers [5]. ...

One of the important tasks of designing a cut feed microstrip patch antenna is to select length (Lf) and width (Wf) of the feeder. There is no well-known formula to find out the length and width of the feeder directly. So, in order to select the appropriate length and width of the feeder, an antenna designer should have some knowledge about the impact of feeder length and width variation on the performance of the antenna. This paper represents the effect of variations in feeder length and width of a cut feed rectangular microstrip patch antenna on the performance parameters like resonance frequency, gain, directivity, bandwidth, return loss, efficiency, axial ratio etc. All the parameters were simulated by using momentum 3D planar electromagnetic simulator 2009.

... The literature analysis of conformal antenna is categories on the basis of their geometrical size like as planar, cylindrical, spherical and circular. Most of the references successfully explain the analysis of planar and non-planar conformal antenna based on their curvature [1], [2]. The four types of feeding technique named as edge feeding, probe feeding, aperture coupling and proximity coupling are taken into account to design the conformal antenna for avionic applications. ...

This paper present the review of various types of conformal antennas arrays design with different feeding mechanism and used different type of dielectric substrate to achieved desired structure with their performance based on their applications. This paper successfully explains the geometry based antennas performance and their characteristic. Conformal Antennas are a key part of military correspondence frameworks that utilization free space as a propagation medium. Many military missions require conformal antenna outlines. Microstrip antennas are appropriate as conformal antenna since they are thin and can be bended to fit forms. Here we discuss a variety of conformal microstrip patch antennas like as cylindrical, spherical, planar and circular with their novel feeding mechanism and explain the advantages overcome to other structure.

... In this paper considerable influence of curvature of rectangular patch on resonant frequency was noticed. This effect was described in details by Kin-Lu Wong for structures utilized in telecommunication [28], but in our case the resonant frequency is dependent on both: the change of the patch dimensions and curvature effect. Thus, an experiment and numerical analysis (in which deformation was evaluated by patch sensor) were carried out. ...

In this paper the utilization of microstrip antenna sensor for deformation monitoring in bended steel structures is presented. This kind of sensing element can be used in structural health monitoring systems. Deformation measurement by patch sensor is based on the reflection coefficient S11 investigation. So far, relationship between resonant frequency and change of patch dimensions was considered in literature only for planar microstrip sensors. In case of samples subjected to bending process the sensor geometry became non-planar. This fact affects measured resonant frequency, thus it should be studied. In order to analyze influence of patch sensor curvature on resonant frequency during bending process Finite Element Method (FEM) simulations were carried out. Results of analysis were experimentally verified.

... The microstrip antenna radiates a relatively broad beam broadside to the plane of the substrate. Thus the microstrip antenna has a very low profile, and can be fabricated using printed circuit (photolithographic) techniques [2]. This implies that the antenna can be made conformable, and potentially at low cost. ...

In this paper, a microstrip patch antenna is studied and the results are simulated using IE3D simulator with an operating frequency of 3 GHz. The conducting patch can take any shape but the preferred configurations are rectangular and circular since the other configurations are parameters. IE3D is a Moment of Method Simulator which solves the Maxwell's Equations in an integral form through the use of Green's functions. The results are analyzed and discussed in terms of return loss, bandwidth, 3D and 2D radiation pattern, Gain vs. frequency plot. The return loss of this antenna is-26dB at 3GHz. The proposed antenna offers 2.34% bandwidth at 2.95-3.02 GHz. In designing a rectangular patch antenna, selection of patch width, length and dielectric constant are the major critical parameters.

... Printed antennas are used in wireless devices such as cellular phones, cordless, wireless LAN Access points, GPS handheld devices, Personal digital assistants (PDAs), and Public switched telephone network (PSTN) series [1]. These patch antennas are not only miniature in size but also manufactured using simple and cost effective techniques [2], [3]. However, radiating currents can be induced on the ground planes of these antennas when they are being used in the devices held by users. ...

... Microstrip antennas are customary components in modern communication systems, since they are low-profile, low-weight, low-cost, and well suited for integration with microwave circuits[1]. Antennas printed on planar surfaces or conformed onto cylindrical bodies have been discussed in many publications[1,2]. However, such is not the case of spherical microstrip antenna arrays, a canonical configuration of great practical interest because of their potential of 360 @BULLET coverage in any radial direction. ...

This paper presents an efficient approach for the calculation of the radiation patterns of circumferential-spherical arrays of circular patches. Using the global coordinate system technique and Mathematica's powerful algorithms for calculating spherical harmonic functions, a computationally- efficient CAD was implemented to evaluate the array radiation patterns and its results were compared with those from HFSS software.

... The microstrip antenna is mostly made of a twodimensional radiating patch on a thin dielectric layer and therefore can be classified as two-dimensional planar component [11] for analysis purposes. The analytical techniques for microstrip antennas can be divided broadly into two groups. ...

... Transmission line model and cavity model often fail in efficient analysis of such complex structure [9]. Therefore, a rigorous and more accurate approach such as full wave analysis is used to analyze conformal microstrip antenna on cylindrical structures [10]. The structure for which analysis has been performed is depicted in figure 1. ...

Calculation of dyadic Green's functions in a fast and convergent manner is a crucial step during analysis of conformal microstrip patch antenna. In the present study, spectral domain dyadic Green's functions and surface current density for cylindrical structure have been calculated. The study demonstrates the behavior of Green's function w.r.t wave numbers in x and z direction. We have also analyzed the behavior of Green's functions for increasing cylinder radius. It is observed that the spectral domain Green's functions show more oscillatory behavior with increasing cylinder radius and thus, the full wave analysis of microstrip antenna becomes non-convergent. The study, therefore, demonstrates the difficulty in full wave analysis of microstrip patch antenna for increasing cylinder radius.

... Classical planar microstrips on an infinite layer-shaped dielectric substrate with grounded opposite surface were investigated in detail using various techniques (Cohn [1], Wheeler [2][3][4], Hammerstad [5], Owens [6], James et al. [7], Tuncer and Neikirk [8], and Edwards and Sreer [9]. In the recent years, attention of numerous researchers is attracted to non-planar microstrips with a conductive strip conformed to a surface of a curvilinear dielectric substrate (for instance, Wong [10]). ...

TEM mode wave propagation in a microstrip transmission line on a dielectric substrate of circular segment cross section is of concern. A suggested design of a microstrip is convenient for manufacturing and allows to miniaturize microstrips since there is no lateral fringing effect of the substrate in the transmitted fundamental TEM mode. By using the bipolar orthogonal coordinates, the plane potential problem is reformulated in the form of trigonometric dual integral equations. The discontinuous integrals containing Legendre functions of complex degree and the Abel integral equation are employed to reduce the dual equations to a Fredholm equation of the second kind. The structure of the Fredholm integral equation allows to obtain a simple approximate solution. Basing on this solution, rigorous approximate formulas for the characteristic impedance are derived. The characteristic impedance of a microstrip transmission line on a silicon substrate is computed and plotted as an example.

... In the literature, boundary-value problems concerning the excitation of a layered medium by N sources, are motivated by important scattering and radiation applications that occur in diversity and abundance for both acoustic and electromagnetic waves. Such applications include the stimulation of the brain by the neurons currents [27], [28], optical diffusion [29], antenna-type scatterers radiating in a layered background [30], microstrip antennas [31], radiation by multiple antennas in inhomogeneous backgrounds [32], and techniques for cancer treatment [33]. ...

The problem of exciting a layered medium with an arbitrary distribution of (acoustic) point sources or (electric/magnetic) dipoles is considered in this dissertation. A mathematical formulation based on the topology of the distribution of the sources/dipoles and their number is employed. The energy transfer process is investigated by adopting the complex form of the energy functionals. Energy Conservation Laws that relate the real part of the power flux with the corresponding scattering cross sections and the imaginary part of the power flux with the Lagrangian density in the propagating medium are derived. The notions of Interaction Scattering Cross Sections (ISCS) and Interaction Power Fluxes (IPF) that quantify the effects of interaction between point sources/dipoles are developed and relevant optical theorems are established. Physical bounds for the ISCS ratios, the number of point sources/dipoles and the number of excitation layers are derived as well. The exact solution of the direct problem in spherical geometry is determined by devising an overall superposition method that combines the T-Matrix, Sommerfeld’s and Green’s Functions methods. In particular, by formulating the superposition of the individual fields into an overall field, exact expressions for the coefficients of the scattered fields are obtained. An extensive parametric numerical analysis for the behavior of the energy functionals and the ISCS ratios is presented. Finally, the behavior of the involved fields is further investigated in the so-called low frequency zone by utilizing tools of asymptotic analysis. Several inverse problems concerning the number of sources/dipoles, the physical parameters of the scatterer and/or its geometrical characteristics are formulated and solved analytically for the spherical geometry.

... The work of Harrington and Mautz is one example [3], and the work of Shen and MacPhie is another [4]. Remarkably, the analysis and design of printed antennas is widely documented in numerous research papers and assembled in several books (see for example [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]). In its simplest form, a planar printed antenna is modeled as a transmission line model with its radiating edges treated as slots. ...

In this paper, the modal theory of antennas is re-visited, believing that it brings invaluable information towards facilitating the design of multi-feed multi-band antennas. First, some subtle changes are proposed to enhance the applicability of the theory. Next, using some efficient computational techniques, the proposed formulations are shown to predict, to a very high accuracy, the input impedance of any antenna under study. This greatly simplifies the antenna problem and focuses design efforts on finding the appropriate complex resonance frequency to cover a required band. Finding the appropriate feed location is then a matter of extracting the corresponding impedance map for this antenna through simple field manipulations.

... Cylindrical microstrip and striplines have been previously studied by several authors using different methods. In [1] and [2], quasistatic approaches were done to deliver good approximations for effective dielectric constant and characteristic impedance, and the full-wave solutions were proposed in [3][4][5][6][7]. ...

... Printed antennas are used in wireless devices such as cellular phones, cordless, wireless LAN Access points, GPS handheld devices, Personal digital assistants (PDAs), and Public switched telephone network (PSTN) series [1]. These patch antennas are not only miniature in size but also manufactured using simple and cost effective techniques [2], [3]. However, radiating currents can be induced on the ground planes of these antennas when they are being used in the devices held by users. ...

This paper presents a compact dual-band dipole
antenna with meander line radiating elements. The proposed
antenna has a balanced structure with dimensions of 35 x 6 x 1:52
mm3, and mounted on a 36:2 x 100 mm2 floating ground
plane. The balanced operation of the design is validated by
incorporating a differential feed in the software simulation and
a 180◦ hybrid junction is used for measurement with the
network analyzer to verify the balanced concept of the prototype.
Simulated and measured results of the S-parameters along with
the de-tuning of the antenna in the presence of the human body
shows good agreement. Moreover the proposed design is used
as an exposure source to the simulated human head model. The
human head is modeled as six layers in the Electromagnetic (EM)
software HFSS to study the interaction between the proposed
balanced antenna and the human head model. The Electric field
(E-field) distribution in the six layers of the human head model is
shown to estimate the penetration of the field when the antenna is
placed at a distance of 7 mm from the proposed design. Also Local
Specific Absorption Rates (SARs) and average SARs simulation
results at 3:78 GHz and 4:29 GHz are shown. The SARs analysis
showed that in all the six layers of the human head model, local
SAR values are greater in fat and Cerebrospinal fluid (CSF) for
both the frequencies while the average SAR values are not very
high.

... With the development of communication and navigation technology, efficient transmission is going on; the implementation of conformal antennas plays an important role to enhance the transfer and receiver characteristics for wireless application. 2,3 The conformal antenna is an array of planar antennas that confirm the structure, and this structure is determined by the physical consideration other than the electromagnetics. 4 The design of the conformal antenna might be of any geometry like circular, cylindrical, and tapered or might depend on the shape of the object. ...

The Internet of Things (IoT) is a connection amongst people and applications to another dimension of machine‐to‐machine communication. IoT scenario is unequivocally related with the development of the advancement of wireless sensor systems (WSNs) and radio‐frequency identification (RFID) frameworks. Owing to the technological advances around the world, energy demand is increasing exponentially. Energy proficiency has turned out to be one of the real worries in the present life that essentially influence every single human action. In communication system, return loss is a major issue for transmission process. Owing to return loss, a huge amount of power consumption occurs. This phenomenon is contemporary with transmission process, and it will initiate a serious problem for high‐speed moving substance like aircraft, rockets, and spaceship. To overcome this problem, a four‐element cylindrical antenna (conformal) array with better axial radiation is proposed. The four U‐shaped slots are uniformly wrapped around on a cylindrical surface, which produces tilted radiation. To enhance the axial radiation, four conformal elements are reefed by a one‐ to four‐microstrip feed network. The proposed conformal design has a bandwidth of 200 MHz (narrow bandwidth) at the center frequency of 3.9 GHz, covering the range of 3 to 3.9 GHz, with the gain of 4.9 dBic, and can be suitable for unmanned aerial vehicles (UAV), wireless avionics intra‐communication (WAIC), and so forth. The proposed design is low profile and can be used for high‐speed avionic applications. Finally, machine learning technique is explored to design a model for a smart antenna with optimistic parameters to reduce return loss and enhance the transmission rate.

... Such deformations can lead to changes in the wearable antenna's shape and characteristics [15,16]. However, due to conformal capability, researches on nonplanar microstrip antennas has received much attention [17], but in comparison to antenna's deformation, it seems the problem is different [18]. ...

This paper presents a study on the bending behavior of rectangular textile patch antennas
including analytical modeling, full wave simulations, and experimental measurements.
In the proposed analytical model, the textile patch antenna was treated as a laminated
composite beam. Therefore, after locating the position of neutral axis considering the
tensile modulus and the dimensions of each layer, the classic cylindrical cavity model was
modified to predict the relation between resonance frequency and bending curvature,
taking into account the patch’s elongation. Since the presented interdisciplinary analytical
approach is associated with a set of simplifying assumptions, a full wave model was
also utilized to study this effect. All the simulations were performed in two modes;
patches with fixed and elongated dimensions. Finally the results of both models were
compared with the experimental measurements and the effects of bending on the
resonance frequency of textile patch antennas were discussed in more detail. The
obtained results showed that some parameters including the direction of bending,
substrate thickness, and mechanical properties of antenna’s components can alter the
textile patch antenna’s behavior under bent conditions.

... In addition, the relative permittivity of a superstrate plays a role in radiation loss, which implies that the radiation resistance of antenna can increase with a higher relative permittivity superstrate [175]. Therefore, a low relative permittivity substrate Owing to the fact that the current density is high at the feeding point compared to farthest parts ( Fig. 7.3(a)), the patch is trimmed in a circular shape to allow the current to be close to tuning capacitive slits. ...

The importance of implantable medical devices (IMDs) in ameliorating the quality of life has long been an attractive research topic. IMDs are placed inside the human body for diagnosis, monitoring and therapeutic applications. Wireless medical telemetry (WMT) for IMDs enables a bidirectional transmission of data pertaining to a patient’s condition and reception of control signals, without wires connected to bedside monitors/controllers. The need of WMT for IMDs is anticipated to pair with the increased number of age-related diseases due to the prolonged life expectancy rate and necessity of telemedicine at aged care facilities.
In a specific type of IMDs, a brain implantable medical device (BIMD) is embedded underneath the skull in the cerebrospinal fluid (CSF). The CSF is an aqueous solution surrounding the brain and provides biomarkers, which are ascribed to neurodegenerative diseases, particularly Alzheimer’s disease (AD). The association between dielectric properties (DPs) of CSF and accumulation of proteins in it can therefore be an important biomarker. In addition, monitoring DPs of CSF in-vivo via a BIMD assists in understanding brain functions with people suffering from AD. One of the key components in BIMDs is the implantable antenna, which is the radio frequency (RF) front-end. The head tissues are extremely challenging for EM radiation compared to other body parts, which make the requirements for BIMDs to be rigorous in terms of the size, safety and sensitivity to changes in DPs of CSF. Furthermore, the absorption of EM field and dissipation into heat in tissues can be evaluated only by a numerical simulation with realistic human body models and accurate DPs of tissues.
This work focuses on several aspects that are mainly centered around implantable antennas in BIMDs for monitoring DPs of CSF through near-field WMT. Thus, the measured frequency-dependent DPs of head tissues available in an online dataset are fitted to a Debye model in the sub-1GHz band (0.1 − 1 GHz) to allow precise optimization of the implantable antenna, estimation of the specific absorption rate (SAR) and calculation of the path loss in head tissues. Concurrent with modelling, DPs measurements of CSF from animal primates are conducted to study whether DPs of CSF are age-dependent and explore the effect of proteins responsible for AD in DPs of CSF.
To monitor DPs of CSF remotely, wireless power transfer (WPT) based upon inductive coupling to a millimeter (mm)-size implantable antenna is investigated. This is a preferred WPT method as biological tissues have a weak magnetic response, consequently, a deeper penetration is achieved for magnetic field as opposed to electric field. Following the severe impact of head tissues on the inductive coupling strength and the small antenna footprint for sensing DPs of CSF, several planar antennas are assessed for monitoring DPs through impedance (resonance frequency). The nearfield interaction with implantable antenna in CSF leads to a resistive loading, which reduces the quality factor and impacts the sensing sensitivity. A near-field data communication link with a strong signal to noise ratio (SNR) is also developed as a feasible solution to avert increasing the power level to the implantable antenna. An exterior antenna coupled to implantable antenna in near-field is used to build a path loss model, which is validated in-vitro in an animal primate. After quantifying the power margin and examining the Poynting vector in head tissues, a sensor is designed with a stable antenna to link changes in DPs of CSF to the received power levels.
The main findings of this thesis show that employing a voltage controlled oscillator (VCO) with a stable implantable antenna is effective to monitor DPs of CSF. The analysis and results described in this thesis will help in establishing a future research direction for building a WMT using a battery-less BIMD to monitor DPs changes in CSF. Lower frequencies (< 20 MHz) can achieve a satisfactory WPT to a battery-less BIMD, whereas higher frequencies can be used to monitor DPs of CSF in-vivo.

... Scattering and radiation problems, concerning the excitation of a layered medium by external or internal point-generated waves, are motivated by significant applications, including e.g. antenna-type scatterers radiating in a layered background [21], cancer-treatment techniques [10], and radiation by multiple sensors in 5G networks [22]. Particularly, excitation of a layered medium by N internal point sources finds applications in optical diffusion, where an incident beam is replaced by multiple sources of different strengths [12], and in stimulation of the brain by the neurons currents [7], [8]; related applications and techniques for mathematical modeling are highlighted by Dassios in his survey [6]. ...

A layered medium is excited by N N external or internal point sources. Boundary-value problems for the generated acoustic waves are formulated. General scattering and optical theorems are established relating the involved fields and far-field patterns due to groups of sources. Interaction scattering cross sections are defined and associated physical bounds are derived. The large- N N behavior of these cross sections is also investigated. Numerical results are presented demonstrating the variations of the interaction cross sections and their physical bounds.

... In recent years, various antenna array antenna designs covering different bands have been introduced for WLAN Applications. The 5 GHz had assigned for wireless LAN (WLAN) in the 802.11ac standards [2]. In this standard, the maximum bandwidth has been specified to be 80 MHz and 180 MHz, with 8 elements antenna enhanced the data rate. ...

An antenna array with 4 ports is designed and implemented. The proposed antenna consists of four ports and a four-antenna array Microstrip patch antenna with ground plane extruded on the substrate. The overall size of the proposed substrate is 220×220 mm ² . The antenna is fabricated on an inexpensive FR4 a dielectric constant of εr=4.5, loss tangent of tan δ=0.019, with thickness of substrate of 1.6-mm and the thickness of patch is 0.035 mm . The measured results represent that the proposed antenna obtained a reasonable bandwidth from 2.4 GHz that could cover point-to-point application defined by 10-dB return loss. Furthermore, The S-Parameters of antenna are simulated and measured. A four-port antenna operating in point-to-point applications is designed; the antenna shows good pattern diversity low correlation coefficient.

... The other important issue for the wearable antennas is the bending effect (for conformal patches) [29]. A part of the research papers dealing with the wearable antennas on textile fabrics and polymers usually include additional information for the effect of bending at typical radii, compliant with the human body [30][31][32][33]. ...

The simultaneous influences of the substrate anisotropy and substrate bending are numerically and experimentally investigated in this paper for planar resonators on flexible textile and polymer substrates. The pure bending effect has been examined by the help of well-selected flexible isotropic substrates. The origin of the anisotropy (direction-depended dielectric constant) of the woven textile fabrics has been numerically and then experimentally verified by two authorship methods described in the paper. The effect of the anisotropy has been numerically divided from the effect of bending and for the first time it was shown that both effects have almost comparable but opposite influences on the resonance characteristics of planar resonators. After the selection of several anisotropic textile fabrics, polymers, and flexible reinforced substrates with measured anisotropy, the opposite influence of both effects, anisotropy and bending, has been experimentally demonstrated for rectangular resonators. The separated impacts of the considered effects are numerically investigated for more sophisticated resonance structures—with different types of slots, with defected grounds and in fractal resonators for the first three fractal iterations. The bending effect is stronger for the slotted structures, while the effect of anisotropy predominates in the fractal structures. Finally, useful conclusions are formulated and the needs for future research are discussed considering effects in metamaterial wearable patches and antennas.

... Tsitsas (2013) καθώς και στον σχεδιασμό και την ανάπτυξη μικροταινιακών κεραιών, βλ. Wong (1999). ΕΥΧΑΡΙΣΤΙΕΣ Θα ήθελα να ευχαριστήσω τον Α' επιβλέποντα καθηγητή μου, κ. ...

... Le modèle de la ligne de transmissions (MLT) [50][51][52] [39]. Les fréquences de résonance de l'antenne sont résolues par les fréquences de résonance de la cavité [51,53]. ...

... Representative applications include e.g. stimulation of the brain by the neurons currents [1], [2], cancer-treatment techniques like ablation and interstitial hyperthermia [3], [4], radiation by multiple sensors in 5G networks [5], multilayer optical diffusion [6], and design of nonplanar microstrip antennas [7]. Moreover, in the context of inverse problems, excitation by N dipoles was employed in field-splitting techniques [8], identifications of fields on spherically-symmetric conductors [9], reconstruction of obstacles buried in layered media [10], and dipoles localization using electromagnetic induction sensors [11]. ...

A three-dimensional layered and isotropic medium is excited by primary spherical waves due to N magnetic dipoles radiating inside or outside the medium. Interaction scattering cross sections (ISCS) are defined as the differences between the overall scattering cross section and the sum of the individual cross sections generated by all dipoles within a layer or by all N dipoles. Optical theorems and physical bounds for the ISCS are established. Extensive numerical investigations are performed for the variations of the ISCS and their physical bounds with respect to the geometrical and physical characteristics of the layered medium. Conditions for which ISCS contribute significantly in the overall cross section are analyzed. It is also demonstrated that the number of excitation layers and the total number N of dipoles can be determined by means of the individual scattering cross sections.

... Microstrip antennas have been studied intensively because of attractive advantages of light weight, low profile, ease of integration with active devices, conformability to mounting hosts, and so on [1]. However, microstrip antennas inherently have a narrow bandwidth, and bandwidth enhancement is usually demanded for practical applications [2]. ...

Offers an up-to-date description of modern multifunctional antenna systems and microwave components Compact multifunctional antennas are of great interest in the field of antennas and wireless communication systems, but there are few, if any, books available that fully explore the multifunctional concept. Divided into six chapters, Compact Multifunctional Antennas for Wireless Systems encompasses both the active and passive multifunctional antennas and components for microwave systems. It provides a systematic, valuable reference for antenna/microwave researchers and designers. Beginning with such novel passive components as antenna filters, antenna packaging covers, and balun filters, the book discusses various miniaturization techniques for the multifunctional antenna systems. In addition to amplifying and oscillating antennas, the book also covers design considerations for frequency- and pattern-reconfigurable antennas. The last chapter is dedicated to the field of solar cell integrated antennas. Inside, readers will find comprehensive chapters on: Compact Multifunctional Antennas in Microwave Wireless Systems Multifunctional Passive Integrated Antennas and Components Reconfigurable Antennas Receiving Amplifying Antennas Oscillating Antennas Solar cell integrated Antennas Aimed at professional engineers and researchers designing compact antennas for wireless applications, Compact Multifunctional Antennas for Wireless Systems will prove to be an invaluable tool.

Array antenna characteristics improvement: parasitic patches (two disposals) and multi layer substrate techniques; This paper will introduce the approaches for characteristics improvement of patch array antenna for electronic scanning radar application. The basic array antenna is designed on FR-4 substrate and we have used microstrip technique as feeding. This antenna is based on 8 patches operating at frequency 3GHz. This structure has two disadvantages; a low gain value caused by the lossy nature of substrate and a narrow bandwidth by dint of microstrip antenna limitations. Thus, the objective of this work is to improve the gain and the bandwidth of the basic structure. For this reason, two techniques will be presented and compared in this paper: Parasitic patches and multilayer techniques. The first one consists on adding a number of parasitic patches, two different ways of parasitic patches dispositions are proposed. The distance between driven and parasitic patches is evaluated. Regarding the second technique, a layer of FR-4 is added to the substrate distanced with air gap which th! ickness is 0.04x .....

N magnetic dipoles radiate (inside or outside) a piecewise homogeneous (layered) and isotropic medium. The power fluxes and energy processes inside and outside the medium resulting from the various interactions between participating fields are investigated by means of the introduced interaction scattering cross sections (ISCS) and interaction power fluxes (IPF). Connections between the power flux through the excitation layers and the radiation in the far field are established by specifying the law of energy conservation for the considered scattering problem. Additionally, the relation between the IPF and the ISCS is derived by applying a generalized version of the optical theorem. Physical bounds for the ISCS with respect to the minimum and maximum individual cross sections and the number of excitation dipoles and layers are derived. The large-N behavior of the ISCS is analyzed. Variations of the ISCS and their physical bounds are numerically investigated.

This letter presents an insightful and significant improvement of the cylindrical cavity model and an experimental methodology to compensate the mechanical bending effects on cylindrical microstrip antennas. In the first part of this document, by studying analytical and numerical results from a non-radiating resonant rectangular cavity, a new function for the resonant length of the circumferential mode that is governed by the antenna thickness and cylinder radius was determined. In the second part, an experimental methodology is presented to compensate the copper elongation effect due to bending. To validate the proposed techniques, a circularly polarized rectangular microstrip antenna was designed and built to operate at 2.2 GHz with an input impedance of 50 Ω for a metallic cylinder with a radius of 25 cm. The experimental results showed that the new approaches to calculate the circumferential resonant frequency and elongation effect due to bending improved significantly the cylindrical antenna design.

L probe provides a huge amount of impedance bandwidth by mounting the patch on a planar and cylindrical substrate. A parametric study and a comparative analysis between planar and cylindrical patch has been presented. Both planar and conformal patches have been designed in X band frequency. Around 2.65 GHz and 3 GHz impedance bandwidth and about 9.66 dBi and 8.37 dBi average gain has been achieved for both planar and conformal antenna, respectively. A stable radiation patterns across the pass band in both the antennas is observed. Design parameters and its effects have been thoroughly studied. Resonant input impedance is plotted. All the simulation work has been carried out in CST EM Simulation Software.

Over the years chat system which is an application or tool used for communicating between two or more persons over a network, has been faced with issues of security, data
integrity and confidentiality of information/data, the attacks include social engineering or poisoned URL (universal resource locator). An effective attack using a poisoned URL may affect lots of users within a short period of time, since each user is regarded as a trusted
user, other are plain text attack which makes communication vulnerable to avesdropping, instant messaging client software often requires users to expose open user datagram protocol ports increasing the threat posed. The purpose of this research is to develop a secured chat system environment using Digital Signature, the digital signature is used to establish a secure communication channel, providing an improved secured technique for authentication of chat communication.

An efficient procedure for the pre-design of circumferential circularly-polarized cylindrical microstrip arrays, based on the electric surface current model, is the focus of this work. Its major achievement is cutting the time to pre-design the patch dimensions down to less than one-tenth of what it takes in a 3D electromagnetic simulator, such as the HFSS, running on high-performance workstations. As a result, the array design procedure can be completed faster and more effectively.

ResearchGate has not been able to resolve any references for this publication.