Mohamed A. Habib

ULTRA WIDEBAND CPW-FED APERTURE ANTENNA WITH WLAN BAND REJECTION

In this paper, we present a new ultra wideband antenna design with band rejection for UWB applications. A CPW-fed circular patch radiates through a circular aperture, which ensures wideband impedance matching and stable omnidirectional pattern over an UWB frequency range, from 3GHz to 10.6GHz. In order to avoid interference

CA-CFAR DETECTION PERFORMANCE OF RADAR TARGETS EMBEDDED IN "NON CENTERED CHI-2 GAMMA" CLUTTER

This work is about evaluating radar performance in detection of targets embedded in a clutter following Non centered chi-2 Gamma distribution model. This model, also called NG-distribution model, is able to fit high resolution sea radar clutter. In this paper, NG model is described. The performances of CA-CFAR radar, namely probability of detection and probability of false alarm, are calculated and closed forms of these probabilities are achieved. In order to evaluate the obtained results, simulation and analytical results are compared. Good matching between these results is achieved.

Design of UWB filter -antenna with notched band at 5.8GHz

In this paper, an UWB integrated filter-antenna system with notched band at 5.8 GHz has been presented. The design of the proposed integrated filter-antenna is based on cascading an UWB notched filter with an UWB antenna. The two parts of the system have already been matched to each others. The antenna-filter has a small size (68 × 27mm2). The system bandwidth meets the UWB requirements.

A New Ultra-Wideband Beamforming for Wireless Communications in Underground Mines

In this paper, a novel ultra-wideband switched-beam antenna system based on 4×4 two-layer Butler matrix is presented and implemented to be used in hostile environment, such as underground mines. This matrix is based on the combination of a broadband two- layer slot-coupled directional coupler and a multilayer slot-coupled microstrip transition. With this configuration, the proposed matrix was designed without using any crossovers as used in conventional Butler matrices. Moreover, this new structure is compact and offers an ultra-wide bandwidth of 6 GHz. To examine the performance of the proposed matrix, experimental prototypes of the multilayer microstrip transition and the Butler matrix were fabricated and measured. Furthermore, a three 4-antenna arrays were also designed, fabricated and then connected to the matrix to form a beamforming antenna system at 3, 5.8 and 6 GHz. As a result, four orthogonal beams are produced in the band 3-9 GHz. This matrix is suitable for ultra- wideband communication systems in confined areas.

An Adaptive Reduced Rank Stap Selection with Staggered Prf, Effect of Array Dimensionality

AN ADAPTIVE REDUCED RANK STAP SELECTIONWITHSTAGGEREDPRF,EFFECTOFARRAYDIMEN-SIONALITYB.A¨issaEMPB.P.17,BordjElBahri,Algiers,AlgeriaM.BarkatAmericanUniversityofSharjahSharjah,UAEB.AtrouzEMPB.P.17,BordjElBahri,Algiers,AlgeriaM.C.E.YagoubSITE,UniversityofOttawaOttawa,CanadaM.A.HabibEMPB.P.17,BordjElBahri,Algiers,AlgeriaAbstract—Space-TimeAdaptiveProcessing(STAP)isawellknowntechniqueintheareaofairborneradars,whichisusedtodetectweaktarget returns embedded in strong ground Clutter, Jammers, andreceiverNoise. STAPhastheuniquepropertyofcompensatingfortheplatformmotioninducedDopplerspread,thusmakingdetectionofslowtargetspossible.Butthereareotherproblemsresultingfromthecharacteristicsoftheairborneradarthatmaylimittheperformanceofdetectionoftheradar,forinstance,theambiguities(RangeorDopplerambiguities)whicharedependentonthevalueofthepulserepetitionfrequency(PRF).WhenPRFishigh,rangeambiguitiesappear;when

Quasi-Metallic-Wall Technique for Increasing the Efficiency of CB-CPW Antennas

This paper presents a new quasi-metallic-wall technique for improving the gain of CB-CPW single antenna and arrays. This technique allows reducing the surface wave losses of the CB-CPW antennas, which decreases the antenna radiation efficiency. It consists on including pins as quasi-metallic wall between the upper and lower ground planes in the CB- CPW antenna structure. To validate the proposed approach, a CB-CPW-slot antenna fed through an inductive coupled CPW-line operating at 5.8 GHz is considered. This approach allows to increase the antenna efficiency from 70% to 95% around the operating frequency. The antenna gain achieves then an improvement of 2 dBi. Also, an antenna array is designed and the pins technique is also applied to prove its applicability for the array case. An efficiency increase from 64% to 95% was achieved. Both single antenna and antenna array withpins were fabricated and measured. A good agreement between numerical and experimental results was obtained.

Design of a new wide-band CPW-fed circular slot antenna

In this paper, a new design of an ultra wide-band antenna is proposed and described. This antenna is composed of a circular slot fed with 50 Omega CPW line through a circular patch. A proper parametric investigation results in an optimal structure, and a bandwidth of 143.2% is thus achieved. Experimental investigations are presented, and the obtained results confirm the proposed antenna performances

Active control on EBG structures for multiband antenna applications

In this work, a parametric analysis of an EBG layer behaviour based on continuous and discontinuous strips has been presented. The obtained results show that continuous and discontinuous strips present dual behaviour when considered as basic elements in the EBG structure. In addition, it has been observed that the discontinuity periodicity act on duality bandwidth. Thus, this duality can be electronically controlled by using diodes to switch between dual cases. Diode capacitor feature may introduce a shift on the duality bandwidth; this shift can be either compensated by the structure dimension or exploited to achieve bandwidth tuning. Experimental results have been presented and validate the simulated ones.

Reconfigurable radiation pattern antenna based on active frequency selective surfaces

In this paper, a prototype of AFSS screen based on the simple dipole strips has been proposed for a reconfigurable radiation pattern antenna. The results achieved in the measurements confirm the expected objectives for the proposed structure. However, it has been observed that the parasitic elements created by the active elements are indeed the main problem in attainting the desired properties. Because of this, the position of bandgap significantly changes which it leads to an in complete transparent screen in one state. However, measurement results demonstrate that using this idea it is possible to achieve a reconfigurable radiation pattern. Study on this subject is undergoing to improve the performance of the antenna.

Design and Implementation of a Miniaturized CPW-FED Antenna with Enhanced Bandwidth

In this paper, the design and implementation of a new small antenna using a CPW-FED technology for further reducing the size and increasing the bandwidth are presented. The proposed antenna is designed and analyzed based on meandered parallel resonant arm to decrease the antenna area. In addition, a superstrate layer is added for further antenna miniaturization and bandwidth enhancement. For validation, an experimental prototype was built and tested. Obtained simulation and measurement results show that this miniaturized antenna operating at 2.45 GHz achieves a bandwidth of 220 MHz for 10-dB of return loss. Both simulation and measurement radiation patterns are stable across the operating frequency range, and show a good agreement.