Mohamed Aghoutane

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.

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.

Novel compact dual-and tri-band filters using stepped impedance resonators

We present in this paper a novel approach for dual-and tri-band filters design with independently controlled center frequencies and bandwidths. On the one hand, a stepped impedance resonator (SIR) is designed to operate at the center frequencies of two bands simultaneously (dual-band), on the other hand, two stepped impedance resonators are designed to operate at the center frequencies of three bands simultaneously (tri-band). To verify the proposed approach two filters are designed and analyzed by using Sonnet and HFSS simulators, the obtained results using these two simulators are in very good agreement

Modelling of temperature and dispersion effects in MESFET and HEMT transistors

In this paper, an accurate technique to model temperature, bias, and frequency dispersion effects in MESFET and HEMT transistors is presented. The approach is based on a single drain to source current source I ds nonlinear model. Pulsed I/V characteristics measurements are used to model bias and frequency dispersion effects while temperature is directly implemented in the I ds equation. Model parameters extraction strategy is simple, being based just on a few measurements. The approach validity is verified by comparing the simulated and measured I/V characteristics of the device tested under continuous and pulsed excitation. Large-signal simulation results show that the model can efficiently predict the output power under different bias and temperature conditions.

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).

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.

Design and implementation of a technology planar 8×8 Butler matrix with square truncated Edge-Fed array antenna for WLAN networks application

In this paper switched beam smart antenna systems are investigated to improve the performance of wireless networks. The microstrip technology of antenna arrays with Butler matrix topology as a beam-former is used to implement the switched beam smart antenna system. The optimum design of a 8×8 planar Butler matrix array, operating at 2.4 GHz for WLAN applications. Systems design and optimization was based on computer simulations.

A Novel CPW BandPass Filter Integrating Periodic Rectangular Slot Cells

In this paper, we introduce the design and the achievement of a Bandpass filter structure based on the use of rectangular slot cell. The originality of this work is to achieve a coplanar filter easy to integrate with microwave planar circuits and having a wide frequency bandwidth. The proposed bandpass filter is a low cost and compact planar filter structure. The final circuit is simulated by using two electromagnetic solvers, ADS and HFSS. The validation into simulation is based on using optimization methods integrated into the both solvers. Simulations have taken into account a high meshing density to cover the whole circuit. The fabricated bandpass filter has an area of 35X31mm2 and having a good insertion loss around -0.75dB in the bandwidth. The comparison between simulation and measurement results presents a good agreement.