Farid Ghanem

A Directive Dual-Band Antenna Based on Metallic Electromagnetic Crystals

This letter presents the design of a dual-band electromagnetic crystal antenna. The design is based on controlling the metallic wire crystal resonances by using different row periods. To analyze and predict the antenna radiation pattern behavior at the two frequency bands, the transmission coefficient parameter is used. To validate the proposed approach, numerical and experimental results are presented, and a good agreement is achieved

A New Electromagnetic Crystal-Based Antenna for Ultrafast Radiolocation Applications

In this letter, a new antenna capable of radiolocating and tracking ultrafast targets is presented. Based on an electromagnetic crystal structure, the proposed antenna uses only one radiating element, and beam scanning is achieved by varying the frequency of the excitation signal. Thus, by exciting the antenna with a wideband signal, different patterns will be deployed simultaneously allowing the space covered by the antenna to be scanned instantaneously. This property makes the proposed antenna ideal to radiolocate ultrafast targets that cannot be tracked by the traditional phased antenna arrays. Moreover, the proposed radiolocation process has strong immunity against signal amplitude variations, which makes the new antenna suitable to operate in hostile environments. To present the developed approach, both theoretical study and numerical simulations using the finite-difference time-domain (FDTD) method are given. To validate the developed approach, experimental measurements are also presented and discussed.

Blind spatio-temporal interference rejection receiver for direct-sequence CDMA over multipath channels

Many recent studies show an increasing interest to develop new adaptive algorithms, which aim to mitigate interferences in the future mobile radio using a CDMA system. In this paper, a new interference suppression receiver for demodulation of BPSK DS/CDMA signals received by a base station antenna array is presented. The proposed receiver, which is suitable for multipath channels, combines a spatial generalized sidelobe canceller (GSC) algorithm with a temporal GSC filter bank. Besides its simplicity, one major advantage of the new structure is the fact that it incorporates conventional algorithms, which have been suggested for use in adaptive spatial beamforming and implements them in temporal filtering. The performance of the proposed receiver is studied in terms of signal-to-interference-plus-noise ratio (SINR), bit error rate (BER) and achievable capacity of a given CDMA cell.

Reduced size cross-coupled resonator bandpass filters for wireless communication systems

This paper presents a class of single-plane microstrip filters that are suitable to achieve high performance and high miniaturization level. A new miniature capacitively loaded resonator is designed and integrated in a compact design, resulting in a filter whose dimensions are less than 30 % of that of conventional parallel coupled-line filters. To analyze the performance of the proposed filter, numerical simulations based on a commercial full wave EM software package (ADS-Momentum) were performed. Experiments were also carried out and a good agreement between measured and simulated results was obtained.

Modified-rate-quantization algorithm for multiple-input multiple-output systems under imperfect channel knowledge

In this paper, a modified-rate-quantization algorithm for multiple input multiple output (MIMO) systems is proposed using singular-value decomposition (SVD). This low complexity scheme adapts the subchannel transmit power and spectral efficiency in the spatial and temporal domains under transmit power and instantaneous bit error rate (BER) constraints. It is shown that with five discrete-rate levels, the proposed scheme reaches a spectral efficiency performance similar to the scheme with a continuous rate. The robustness of the proposed scheme to channel state information (CSI) imperfections is also studied. The obtained results show that the spectral efficiency is unaffected up to a certain level, but the bit error rate (BER) performance is particularly sensitive to these imperfections, especially at high SNR levels. Indeed, this ideally designed MIMO system over-estimates the subchannels, which leads to a deterioration of the BER performance. A new version of this algorithm, which is suitable for vertical Bell Labs layered space–time (V-BLAST) systems, is also presented. Through simulation results, it appears that the extended algorithm allows to reach a better performance in terms of spectral efficiency than other known schemes, but it is more sensitive to imperfect CSI than the first version.

On the channel capacity in MIMO systems for aeronautical channels

This paper investigates the capacity behavior in an aeronautical MIMO link between a terrestrial transmitting station and an airborne station. The channel model is small-area and considers only the scattering function. For this purpose, two different scenarios are simulated and analyzed. In the first one, only reflected scattered paths are considered and the second scenario adds a line of sight (LOS) component. The channel effect on the capacity and the capacity variation due to antenna rotation during flight are the main topics investigated. To enhance the channel capacity, the direct paths must be decorrelated by either a space-time coding or by polarization diversity.

Novel and simple approach for reconfiguring the pattern of an UWB CPW-Fed monopole antenna

A simple pattern reconfiguration approach of an Ultra Wide Band (UWB) monopole antenna is presented. By inserting a VIVALDI shape in the Coplanar-Waveguide (CPW) ground plane, the pattern reconfiguration is achieved without changing the original size and form of the monopole. Only two switches were used, thus the main beam is controlled depending on the state of these switches. Therefore, in the band of reconfiguration, the antenna radiates in three different directions (two directive states and one omnidirectional state). Switches were inserted in specific locations so that to eliminate currents to distribute and to radiate from that side, hence the main pattern is shifted in the other side. The proposed approach can be applied to different CPW-Fed monopoles, consequently, it may be suitable for domains were dynamic pattern reconfiguration is needed such as tracking, cognitive radio etc. Our approach is applied to two monopoles: printed stepped rectangular monopole and circular disc antenna. Furthermore, realized prototype and measurements are carried out.

A transmit antenna selection scheme for STBC MIMO OFDM systems with imperfect channel knowledge

In this paper, an adaptive MIMO-OFDM transmitter with imperfect CSI is proposed to reach a maximum transmission rate under a given required bit error rate (BER) and a total transmit power constraints. This transmitter uses the adaptive two-dimensional (2D) coder-beamformer derived in Zhou, S. and Giannakis, G. B., (2002) for each OFDM space-time coded subcarrier, and the greedy adaptive scheme in Hughes-Hartogs, D. (1989) to pursue power and bit loadings. The transmit antennas are selected according to the resultant subchannel Frobenius norm. Compared to the scheme using the whole number of available transmit antennas and despite a certain performance loss, the proposed reduced-complexity architecture provides a viable spectral efficiency.

A new wideband model for metallic wire electromagnetic crystal antennas

In this paper, a new wideband model for metallic wire electromagnetic crystal antennas is presented. It is well known that at resonance frequencies of the crystal structure, the antenna radiation pattern consists in a narrow broadside beam. However, as frequency is increased, the radiation pattern starts to deviate toward end-fire direction. The more the operating frequency is far from resonances, the more the beam deviation is high.

Directive frequency switched beam antenna based on EBG structures

In this paper, a new type of smart antennas based on EBG material properties, and suitable for base stations deployment is presented. In traditional smart antennas, the beamforming is realized by means of phase shifts between several excited antennas constituting the network. The proposed smart antenna excites only one element and the beam switching is realized by exciting the antennas at different frequencies. Following the analytical presentation, both numerical and experimental results are given and discussed.