B. Ghafary, F.d. Kashani, E. Kazemian,
Volume 9, Issue 1 (3-2013)
Abstract
The effects of aberration on the Bit-Error-Rate (BER) and reliability of free- space optical (FSO) communication links are investigated. Based on aberrated divergent rectangular partially coherent flat-topped beam formula on the receiver plane and considering the atmosphere losses due to absorption and scattering, numerical values for Power In Bucket (PIB), Signal to Noise Ratio (SNR) and BER are calculated. Using above mentioned values, the effects of source parameters on link reliability is described. The results are illustrated by graphs obtained by calculation and simulation.
N. Noori,
Volume 10, Issue 2 (6-2014)
Abstract
In this paper, an optimal approach to design wideband tapped-delay line (TDL) array antenna is proposed. This approach lets us control the array angular and frequency response over a wide frequency band. To this end, some design restrictions are defined and a multi-objective optimization problem is constructed by putting the individual restrictions together. The optimal weights of the TDL processor are determined through solving this multi-objective problem. A design example is presented to show performance of the proposed method and compare the array response with those previously published in the literature.
B. Zakeri, H. Bernety,
Volume 10, Issue 4 (12-2014)
Abstract
Band-notch characteristic has been of great interest recently to overcome the electromagnetic interference of Ultra-wideband systems (UWB) with other existing ones. In this paper, we present a novel microstrip-fed antenna with band rejection property appropriate for UWB applications. Band-notch characteristic has been achieved by adding a rectangular resonant element to the ground section. A prototype was fabricated and measured based upon optimal parameters. Experimental results show consistency with simulation results. Measurement results confirm that the antenna covers the UWB band and satisfies a band rejection in the frequency span of 5 GHz to 5.7 GHz to restrain it from interference with Wireless Local Area Network (WLAN). Then, to achieve better isolation, a rectangular strip is appended to the band-notch creating part of the ground section to enhance obtained VSWR up to 30 through simulation. In addition, by applying a similar technique, a dual band-notched characteristic with an average simulated VSWR of around 13.75 has been achieved for WLAN and the downlink of X band satellite communication systems with each more than 10. Features such as small size, omnidirectional pattern and perfect isolation make the antenna suitable for any UWB applications.
Y. Zehforoosh, M. Sefidi,
Volume 13, Issue 2 (6-2017)
Abstract
In this article, we present a new design of a coplanar waveguide fed (CPW-fed) ultra-wideband (UWB) antenna with dual band-notched characteristics. Two notched frequency bands are achieved by using two inverted U-shaped stepped impedance resonators. The proposed antenna can operate from 2.82 to 11 GHz (118%), defined by VSWR< 2, except two notched bands around 3.5 GHz (WiMAX) and 5.5 GHz (WLAN). The size of the antenna is 20×20×1.6 mm3. The experimental and simulated results of the prototyped antenna, including voltage standing wave ratio (VSWR), radiation pattern, and gain characteristics are presented and discussed. In addition, Analytical Hierarchy Process (AHP) method used for comparison the proposed antenna with previous designed structures.
H. Sedighy,
Volume 14, Issue 2 (6-2018)
Abstract
A null steering GPS antenna array is designed in this paper. In the proposed method, the exact full wave antenna radiation properties with the effect of mutual couplings and nearby scatterers are considered to calculate the array steering vector, precisely. Although the proposed method is not constrained by the array geometry and the antenna element specifications, a five patch antenna elements with planar array geometry is designed and simulated as an anti jam GPS antenna example. The simulation results show the importance of the mutual coupling effects. Moreover, the results verify the proposed method ability to encounter with the multiple GPS jammer sources. Finally, the effect of jammer power is investigated which shown that the antenna performance is increased by jammer power enhancement.
M. A. Trimukhe, B. G. Hogade,
Volume 15, Issue 2 (6-2019)
Abstract
In this paper a particle swarm optimization (PSO) algorithm is presented to design a compact stepped triangle shape antenna in order to obtain the proper UWB bandwidth as defined by FCC. By changing the various cavity dimensions of the antenna, data to develop PSO program in MATLAB is achieved. The results obtained from the PSO algorithm are applied to the antenna design to fine-tune the bandwidth. Bandwidth optimization for ultra-wideband frequency of 3.1 GHz to 10.6 GHz is achieved by applying PSO algorithm. High-Frequency Structure Simulator (HFSS) software tool is used for the simulation. An optimized antenna is fabricated, tested and test results are found in accordance with simulation results.
D. Jamunaa, G. K. Mahanti, F. N. Hasoon,
Volume 16, Issue 2 (6-2020)
Abstract
This paper describes the synthesis of digitally excited pencil/flat top dual beams simultaneously in a linear antenna array constructed of isotropic elements. The objective is to generate a pencil/flat top beam pair using the excitations generated by the evolutionary algorithms. Both the beams share common variable discrete amplitude excitations and differ in variable discrete phase excitations. This synthesis is treated as a multi-objective optimization problem and is handled by Quantum Particle Swarm Optimization algorithm duly controlling the fitness functions. These functions include many of the radiation pattern parameters like side lobe level, half power beam width and beam width at the side lobe level in both the beams along with the ripple in the flat top band of flat top beam. In addition to it, the dynamic range ratio of the amplitudes excitations is set below a certain level to diminish the mutual coupling effects in the array. Two sets of experiments are conducted and the effectiveness of this algorithm is proved by comparing it with various versions of swarm optimization algorithms.
M. Khalaj-Amirhosseini, M. Nadi-Abiz,
Volume 16, Issue 2 (6-2020)
Abstract
Phase Perturbation Method (PPM) is introduced as a new phase-only synthesis method to design reflectarray antennas so as their sidelobe level is reduced. In this method, only the reflected phase of conventional unit cells are perturbed from their required values. To this end, two approaches namely the conventional Optimization method and newly introduced Phase to Amplitude Approximation (PAA) method are proposed. Finally, a reflectarray antenna is designed and fabricated to have a low sidelobe level and its performance is investigated.
M. Khalaj-Amirhosseini,
Volume 17, Issue 1 (3-2021)
Abstract
Linear and planar antenna arrays are synthesized to have maximum directivity for a specified sidelobe level. The directivity is maximized subject to a given SLL. The beamwidth and the zeros of array factor are studied as well as the directivity. Maximum directivity-arrays are compared through some examples with super-directive, uniform, Dolph-Chebyshev and Riblet-Chebychev arrays to find a complete definition of optimum arrays. Also, the optimum value of n-bar is intuitively found for Taylor arrays.
J. Fatemi-Nasab, S. Jarchi, A. Keshtkar,
Volume 17, Issue 1 (3-2021)
Abstract
In this study, a radiation pattern reconfigurable microstrip antenna is designed and fabricated. The antenna’s radiation pattern is directed in 9 different angles by employing a radiating patch and embedding complementary split ring resonators (CSRR) on the ground plane. The radiating patch is of circular shape, while for CSRR elements both circular and rectangular shapes are investigated. The antenna is excited through coaxial feed. There are four CSRR cells on the ground plane. With applying slots on CSRR’s arms and loading them by pin diodes, variable length CSRRs are obtained which result in radiation pattern reconfigurable property. Radiation characteristics of the antenna versus different switching modes of pin diodes are investigated and illustrated. The proposed antenna is also compact. The designed antenna was fabricated on FR4 substrate with thickness of 1.6 mm, and measurement results are provided. The results demonstrate that the presented antenna has impedance bandwidth of 2.39-2.47 GHz with a gain of more than 7 dBi.
S. Singh, M. D. Upadhayay, S. Pal,
Volume 17, Issue 2 (6-2021)
Abstract
In this manuscript, higher-order Orbital Angular Momentum (OAM) modes and parameters affecting vortex in the radiation pattern have been studied. A uniform circular array resonating at 10 GHz frequency is formed using eight identical rectangular patch antennas. Three uniform circular arrays are analyzed, simulated, and fabricated for OAM modes 0, +1, and -1 respectively. The higher-order OAM modes ±2, ±3, and ±4 are simulated and their effects on radiation and phase pattern are discussed. The effect of number of antenna elements and radius of the circular array on the phase purity of higher order OAM modes is presented. The results of simulated radiation patterns and phase front are well satisfying the generation of OAM modes. The measured results show a close agreement with the simulated result.
M. Khalaj-Amirhosseini,
Volume 17, Issue 2 (6-2021)
Abstract
Nonuniform Phased Sampling method is proposed to phase-only synthesize the power pattern of both linear and planar antenna arrays. This method modifies the conventional sampling method which is used for amplitude-phase synthesis. This method is based on assigning suitable phases to the sampling points of radiation pattern in order to reach desired amplitude of currents. Some examples are given to verify the effectiveness of the proposed method for both pencil-beam and shaped beam patterns.
A. Chaabane, M. Guerroui,
Volume 17, Issue 4 (12-2021)
Abstract
A new design of a Coplanar Waveguide-Fed (CPW) Ultra Wideband (UWB) Rhombus-shaped antenna for Ground Penetrating Radar (GPR) applications is designed and discussed in this work. The antenna has a simple design which is composed by a rhombus-shaped patch and a modified ground plane. The working bandwidth is improved by removing the metal from the upper part of the ground plane surrounding the patch and by introducing a corrugation geometry in the ground plane. The proposed antenna was designed on a low-cost FR4-substrate having a compact size of 0.2721λ0×0.2093λ0×0.0157λ0 at 3.14 GHz. All the simulations were carried out by using the commercially software CST Microwave StudioTM. The simulated results show that the designed antenna covers an UWB extending from 3.14 GHz to 13.82 GHz (125.94%) and indicate excellent radiation performances throughout the operating bandwidth. The measured bandwidth is nearly extending between 3.95 GHz and 13.92 GHz (111.58%). Besides, the antenna bandwidth response was checked in close proximity to a mass of Concrete. The obtained results are satisfactory and assure the efficiency of the designed antenna to work as a GPR antenna.
F. Bahmanzadeh, F. Mohajeri,
Volume 18, Issue 1 (3-2022)
Abstract
In this article, a very small flexible antenna with dual-band rejection specifications is proposed for operating in both wearable and ultra-wideband (UWB) applications. The overall size of this antenna is about 18×18×0.508 mm3 and by etching out two rectangular slot type single split-ring resonators (SRRs) of different dimensions from the radiating patch, dual band-notched specifications are obtained in WiMAX (3.3 GHz to 3.7 GHz) and WLAN (5.15 GHz to 5.825 GHz) wireless communication bands. The designed antenna operates over a wide impedance bandwidth (|S11| < –10 dB) from 2.1 GHz to 12 GHz which can cover the whole UWB band from 3.1 GHz to 10.6 GHz and reject the two mentioned bands. An asymmetrical partial ground plane and a beveled radiating patch are utilized to achieve 140% fractional bandwidth. Also, due to the good wearable radiation characteristics, this antenna can operate in industrial scientific medical (ISM) band from 2.4 GHz to 2.5 GHz. Meanwhile, the specific absorption ratio (SAR) value of the proposed antenna is less than the standard limit of 1.6 W/kg.
M. Khalaj-Amirhosseini,
Volume 18, Issue 3 (9-2022)
Abstract
Linear antenna arrays are synthesized to have maximum directivity for a specified beamwidth. The directivity is maximized subject to a given beamwidth such as null to null or half power one. The excitation currents are obtained using a matrix equation obtained from the Lagrange multiplier method. The performance of the proposed method is studied by means of some examples. The synthesized arrays have the pre-specified beamwhidths and their directivity is close to the number of elements.
K. Fertas, F. Fertas, S. Tebache, A. Mansoul, R. Aksas,
Volume 18, Issue 3 (9-2022)
Abstract
In this paper, a frequency switchable antenna design using genetic algorithms (GAs) for dual band WiMAX (3.5GHz) and WLAN (5.2GHz) applications is proposed. The area of the radiating patch element is divided into 2 mm square cells, with each cell assigned a conducting or non-conducting characteristic. To realize frequency reconfiguration, switches are incorporated into appropriate locations to activate/deactivate corresponding cells. The on/off states of the switches are represented by the presence or absence of conductor, respectively. Hence, the proposed approach allows the antenna to operate as mono-band or dual-band radiator according to the desired application. Further, measurements and simulations are carried out and a reasonable agreement is achieved.
Atefeh Sohrabi, Hamideh Dashti, Javad Ahmadi-Shokouh,
Volume 19, Issue 4 (12-2023)
Abstract
In this article, an active electrically small Horn antenna for very high frequency (VHF) and ultra-high frequency (UHF) frequencies is presented. The proposed horn antenna has a height of 5 cm and a diameter of 4.28 cm which can cover 6-12 GHz without a special active circuit with the VSWR of less than 2. A Non-foster Active Adaptation Circuit is used to reduce the antenna input frequency from 164 MHz to 880 MHz. Good matching is visible between the simulation results and the measurement of the antenna reflection coefficient with the active matching circuit. The proposed structure has more than 137 % bandwidth. With the proposed active antenna, the problem of non-portability of VHF and UHF Horn antenna antennas has been solved. Finally, by analyzing the time domain, the stability of the circuit is examined, and the results of the stability test show that the system, including the antenna and the circuit, is stable. The antenna and the matching circuits are simulated by CST microwave studio and advanced design system, respectively.
Ayotunde Abimbola Ayorinde, Sulaiman Adeniyi Adekola, Ike Mowete,
Volume 19, Issue 4 (12-2023)
Abstract
This paper, using the circuit-geometric features of the Method of Moments (MoM), presents a comprehensive analytical treatment of an exponentially non-uniform helical antenna (ENH), mounted on a ground plane of finite extent. Earlier investigations reported in the literature established that the introduction of an exponential non-uniformity in the turns spacing of an otherwise uniformly wound helical antenna significantly improves its axial ratio and power gain profiles, but failed to address two important questions; one concerning the influence of the degree of non-uniformity on the antenna performance: and the other, the associated return loss profile, which is of particular importance in practical applications. It is shown in this paper, that when a properly designed impedance matching circuitry is introduced, a return loss of the ENH of close to 60 dB is achievable; without compromising axial ratio and gain performances. Indeed, axial ratio bandwidth remained unchanged at 54.55% for both the impedance-matched and unmatched ENHs, whilst maximum gain changed marginally from 14.19dB, for the unmatched ENH to 14.18dB for the impedance-matched antenna.
