Naima Amar Touhami

Miniaturized Microstrip Patch Antenna with Defected Ground Structure

The aim of this work is to miniaturize a microstrip patch antenna resonating at 3 GHz. For this purpose, defected ground structure (DGS) has been employed to shift the resonance frequency of an initial microstrip antenna from 5.7 GHz to 3 GHz by disturbing the antennas current distribution. The proposed DGS is incorporated in the ground plane under the patch antenna to improve its performances. Finally, a miniaturization up to 50%, with respect to the conventional microstrip antenna, is successfully accomplished. A prototype of the antenna was fabricated with the FR4 substrate and tested. The measurements results were in good agreement with simulation results.

A Compact CPW-Fed Planar Pentagon Antenna for UWB Applications

In this paper, the design and analysis of a compact coplanar waveguide-fed ultra wideband pentagon antenna are presented. To achieve ultra wideband performance, two modiflcations are introduced. The flrst one is to remove a small fan angle on each side of the ground plan, and the second one is to modify the sharp of the patch in the width. The optimal dimensions can be achieved by a parametric analysis. The antenna design exhibits a very wide operating bandwidth of 16.7GHz with a return loss better than 10dB in the frequency range from 4.46GHz to 21.14GHz. The gain of the proposed antenna is 6.3dBi. This antenna conflguration will be useful for UWB indoor application as it is easy to fabricate and integrate with RF circuitry. All simulations in this work were carried out by using the electromagnetic software CST.

ULTRA-BROADBAND HIGH EFFICIENCY MODE CON- VERTER

In this paper, we develop a small-sized mode converter with high performance, high conversion e-ciency and instantaneous bandwidth as high as 55%. This mode converter transforms energy from the TM01 flrst high-order mode towards the fundamental TE11 circular waveguide mode The proposed structure increases the free spurious operating bandwidth in comparison with the existing results in literature. An X/Ku-bands experiment prototype unit was designed, ensuring practical return losses better than 28dB and insertion losses less than 0.1dB (conversion e-ciency > 98:8%) within the entire frequency bandwidth ranging from 9.25GHz to 16.25GHz The presented architecture ofiers useful features such as very wide bandwidth, small size, easy achievement as well as excellent performance, which makes it very suitable for High-power microwave (HPM) sources that generate the TM01 circular waveguide mode. In these cases, the TE11 mode is needed since it has a convergent radiation pattern able to drive conventional antennas. Moreover, this compact concept is fully scalable to any millimeter frequency band.

Genetic Algorithm Optimization for Microstrip Patch Antenna Miniaturization

The miniaturization of the patch antenna has become an important issue in reducing the volume of entire communication system. This paper presents an improved method of size reduction of a microstrip antenna using the genetic algorithm. The shape of a typical rectangular patch is modified in order to reduce it resonance frequency keeping the physical volume of the antenna constant. Indeed, the initial patch is divided into 10× 10 small uniform rectangles (Pixel), and the genetic algorithm searches, the optimal configuration for the desired goal. The resonance frequency of a micro-strip patch is shifted from 4. 9G Hz to 2.16 GHz and a rate of miniaturization is up to 82%. To validate the procedure, an antenna prototype has been fabricated and tested with an FR4 substrate. The measurements results were in good agreement with simulation ones.

Miniaturized Microstrip Patch Antenna with Spiral Defected Microstrip Structure

Use of discontinuities in microstrip lines is currently employed to improve the performance of different passive circuits, including size reduction of amplifiers, enhancement of filter characteristics and applications to suppress harmonics in patch antennas. This paper presents an improved method of size reduction of a microstrip antenna using Defected Microstrip Structure (DMS) that it is used to perform serious LC resonance property in certain frequency. The DMS is integrated in antenna structure, and therefore this method keeps the antenna size unchanged and makes a resonance frequency. This resonance is due to the abrupt change of current path of antenna that resonates at 5.8 GHz which is shifted to 2.69 GHz thanks to spiral DMS. A prototype of the antenna was fabricated with an FR4 substrate and tested.

High-Performance LPF Using Coupled C-Shape DGS and Radial Stub Resonators for Microwave Mixer

A high-performance microstrip low-pass filter (LPF) with low cutoff frequency, negligible passband insertion loss, very sharp transition band, and deep ultra-wide stopband is designed, fabricated and measured. The presented filter is realized using three types of resonators which are coupled C-shape defected ground structure (C-CDGS), mirrored series-resonant branch loaded by radial stub and high impedance line loaded by radial stub. A novel equivalent circuit model of the C-CDGS resonator is created, and its corresponding parameters are also extracted. The proposed filter is experimentally verified through the measured results which show good agreement with electromagnetic simulations.

Improvement of Carrier Power to Third-Order Intermodulation Distortion Power Ratio for a Power Amplifier at 5.25 GHz using LINC Method

Method: In this paper, the Linear Amplification with Nonlinear Components (LINC) technique is used to improve the linearity and efficiency of the power amplifier. The LINC technique is based on converting the envelope modulation signal into two constant envelope phase-modulated baseband signals. After amplification and combining the resulting signals, the required linear output signal is obtained. To validate the proposed approach, LINC technique is used for linearizing an amplifier based on a GaAs MESFET (described by an artificial neural network Model).

Compact Size Coplanar Waveguide Bandpass Filter Design and Modeling

This paper proposes a compact cross-Coupled lines design of a coplanar waveguide bandpass filter which is built from cascading several sections of quarter wavelength open-end series stubs. The design originates from modeling the series stub as a system of two asymmetrically coupled transmission lines, which is then made equivalent to a basic filter element of admittance inverter. In addition, by introducing the cross-coupling effect, two transmission zeros at the upper and lower stopbands may be created, which improve the filter selectivity. Simple equivalent lumped circuit models of the discontinuities formed between two sections are evaluated and incorporated into the circuit simulation to get better prediction for the filter performance. Specifically, two 4th order CPW bandpass filters centered at about 2GHz implemented on a FR4 substrate are demonstrated.

NOVEL DECOUPLING TECHNIQUE FOR ENHANCING THE MUTUAL COUPLING BETWEEN PRINTED ANTENNAS

In this work, an E-shape Defected Ground Structure (DGS) is achieved to reduce the mutual coupling between two nearby microstrip antennas up to 47% (from 0.064 to 0.03). Both antennas radiate in the same frequency band of 10 GHz. The technique is based on a wall integrating periodic structure permitting the absorption of the electromagnetic field. By using this structure, it was possible to achieve a 20 dB reduction in the insertion loss S21 between the two microstrip patch antennas with center-to-center distance of 0.45λ0 (λ0 is the free-space wavelength). The obtained coupling coefficient demonstrates that there is a good isolation between the two antennas. EM solver, simulating the reflection and transmission coefficients of the designed antenna arrays, achieves the reduction of the mutual coupling. The simulated results are verified by measuring the fabricated prototypes.

Studying the Influence of the Number Vanishing Moments of Daubechies Wavelets for the Analysis of Microstrip Lines

Using Daubechies wavelet with one, two, three, and four vanishing moments, basis functions for the efficient solution of electromagnetic integral equations are studied. Due to the vanishing moments, the moment matrices resulting in these problems are sparsified by wavelet, and consequently, the solution can be obtained rapidly. The microstrip line is examined in order to demonstrate the advantages of this suggested wavelet-moments method over the traditional moment method. To demonstrate the effectiveness and accuracy of the proposed technique, numerical results for error relative for different vanishing moments of Daubechies wavelets are presented. It is found that Daubechies wavelets with larger number of vanishing moments generally give higher accuracy. NOMENCLATURE MoM Method of Moments TEM Transverse electromagnetic dbN Daubechies wavelet with N vanishing moments nfb Number of basic functions nfe Number of testing functions Thr Threshold IM Impedance Matrix CPU Central Processing Unit