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An antipodal Vivaldi antenna is designed for use in the ground penetrating radar (GPR) detection of landmines. Two such antennas, one transmitting and one receiving, are connected to an ultra-wideband GPR to record the responses of exact models of certain types of landmines. Later, a periodic structure converter is used to transform the antennas' linear polarization into circular polarization. The...
Information and communication systems have several security vulnerabilities. In addition, conventional security software requires tuning effort and may not be able to detect many web attacks. For this reasons, security becomes a worldwide objective to many technological systems including Learning Management Systems (LMSs) such as Moodle. In this work, we propose a secured multi agent system (MAS)...
This paper presents an inventive and simple procedure for the design of a 2D slotted waveguide antenna (SWA) having a desired sidelobe level (SLL) and a pencil shape pattern. The 2D array is formed by a defined number of 1D broadwall SWAs, which are fed using an extra broadwall SWA. For specified number of identical longitudinal slots in both dimensions, the desired SLL and the required operating...
A simple method for the design of rectangular slotted waveguide antennas (SWAs) with specified sidelobe levels is briefly described, and is used to design an example SWA with 7 broadwall elliptical slots and sidelobes lower than −20 dB. A special corrugation geometry is then added to the SWA, where the uniform height of the corrugations controls the SWA's operation frequency. This height can be changed...
The smart behavior of cognitive receivers is based on an efficient spectrum sensing, leading to an opportunistic use of vacant resources. Therefore, an error-free detection of spectrum white spaces is required to enable all the adaptive functionalities of cognitive radios. Practically, the RF tunable frontend is a source of various RF impairments that harm the accuracy of sensing techniques. On the...
In this paper, a circularly polarized antenna operating at 1.575GHz, for GPS applications is designed. The antenna has a square patch, with cross slots to ensure Right Hand Circular Polarization (RHCP) over the operating frequency range. Electronic Band Gap (EBG) structures are incorporated between the patch and the ground plane to reduce the back lobes. The antenna has a gain of 5.37dB. The design...
In a cognitive radio system, spectrum sensing is considered as the key step of the cognition cycle and the primary function of the opportunistic usage of the spectrum. In real world scenarios, spectrum sensing algorithms are sensitive to several factors especially the model uncertainty problem in low signal-to-noise ratio environments. In this paper, a blind detector based on the cyclostationarity...
Spectrum sensing has been identified as the key step of the cognition cycle and the most important function for the establishment of cognitive radio. In this paper, a blind cyclostationary feature detector, which is based on the symmetry property of cyclic autocorrelation function (SP-CAF), is implemented and tested using universal software radio peripheral platform and GNU Radio open-source software...
In this paper, a metamaterial unit cell with low effective permeability attained over a specific frequency band is used to form a planar single-layer metamaterial structure, which is utilized as a lens for broadside gain enhancement of a patch antenna. The proposed metamaterial lens consists of an 8-by-8 matrix of Split-Ring Resonators (SRRs), and is positioned above a probe-fed rectangular patch...
In this paper, a simple method to estimate the relative permittivity εr and the tangential loss tan(δ) of wearable textiles is presented. Quarter-wavelength stub-line band-stop filters, based on jeans and cordura textiles, are designed assuming reasonable initial values of εr and tan(δ), fabricated and experimentally tested. The filter designs are then re-simulated, by tweaking the values ofεr and...
In this paper, a compact quad-band antenna based on Open Loop Resonators (OLRs) is presented. The antenna is microstrip line-fed, and is printed on a 40 mm × 35 mm × 1.6 mm FR4-Epoxy substrate over a partial ground plane. The incorporation of each OLR contributes a resonance that depends on the OLR's design frequency and electrical length. Ansoft HFSS, an FEM-based solver, is used to design and simulate...
A simple frequency-tunable antenna for cognitive radio is proposed. It features a narrow bandpass filter, rendered tunable with a single varactor, and embedded in the feed line of an ultrawideband antenna. A modified version capable of both ultrawideband and tunable narrowband operations is also presented. Due to the topology of the antenna, the required DC biasing lines are easy to design and leave...
In this paper a novel printed diversity antenna for WiMAX applications is proposed. The antenna consists of two identical monopoles, and operates over a wide band spanning the 2.8–4.7 GHz frequency range, over which it has high isolation of over 20 dB. The diversity performance of the antenna, which is attributed to the configuration of the slots placed in its ground plane, is assessed by calculating...
This paper presents a planar antenna for employment in overlay and underlay ultra-wideband cognitive radio (UWB-CR). The antenna can be operated as ultra-wideband, for underlay CR and for sensing in the overlay CR. When used in the overlay CR mode, the proposed antenna can selectively have one, two or three notches in the WLAN, WiMAX, and U-NII bands, to prevent interference to primary users operating...
In this paper, a polarization reconfigurable microstrip antenna, for WLAN applications, is proposed. The antenna structure is based on a reconfigurable feed network, which drives a circular patch. The approach, presented herein, is based on electronically reconfiguring the phase difference, between the antenna's feeding ports, to achieve polarization diversity. The proposed antenna is designed and...
In this paper, a modified Finite Volume Control (FVC) method is introduced and used to solve for the fields in a 3D rectangular waveguide. The FVC method finds its main applications in Computational Fluid Dynamics (CFD) problems and has been rarely used in Computational Electromagnetics (CEM). The 3D rectangular waveguide under consideration is coupled through its apertures to two infinite conducting...
This article describes a spreadsheet tool for the design of major antenna elements and antenna arrays. The antenna elements included are the dipole, circular loop, long wire, rectangular and circular patch antenna. Linear, circular, planar, and cylindrical array types can also be simulated. It is also possible to study an antenna behavior for given parameters, plot its patterns, and estimate its directivity...
Opportunistic beamforming is investigated in the context of multicell OFDMA uplink scheduling. A low complexity scheduling algorithm for utility maximization with opportunistic beamforming is presented. Beams are formed in a pseudorandom fashion thus allowing users to opportunistically benefit from the antenna gain and interference rejection capabilities. The simulations for resource allocation in...
In this paper, two designs of an ultra-wideband antenna with controllable band notch are presented. The first design is based on one complementary split-ring resonator (CSRR), whereas the second has two slightly-different conjoined CSRRs. By mounting an electronic switch across the slot of a CSRR, this latter can be activated/deactivated, thus offering the ability to switch ON and OFF the band notch...
A novel circularly polarized microstrip antenna that incorporates a decagonal slot in the ground plane is presented in this paper. The antenna is based on a 0.762-mm-thick Rogers RO3203 substrate with dimensions 5 cm × 8 cm, and employs a Wilkinson power divider as a feeder. The proposed antenna is designed and simulated using Ansoft HFSS, a Finite-Element-Method based EM solver. The computed return...
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