Bilal Beydoun

Timing synchronisation method for MIMO-OFDM system using orthogonal preamble

The benefits of OFDM (Orthogonal Frequency Division Multiplexing) include resistance against RF interference, high spectral efficiency and lower multipath distortion, while MIMO (Multi-Input Multi-Output) system increases the bandwidth due to the propagation of signals using multiple transmit antennas. The timing synchronization in MIMO-OFDM system, is the main challenge in order to detect the header of each received frame. In this paper, a new timing synchronization method based on orthogonal codes is proposed. Simulation results, for the proposed method, show a good performance for timing synchronisation for MIMO-OFDM system by using some LTE parameters.

Characteristics degradation of the SiGe HBT under electromagnetic field stress

Abstract This paper describes a new reliability study in SiGe Heterojunction Bipolar Transistors (HBTs) by which the electromagnetic field aggression effects can be identified. Base current deviation mechanism with current gain degradation is studied for the first time. Reverse Gummel plots and capacitance characterizations indicate that the electromagnetic field stress induces traps not only at the emitter–base spacer’s oxide, but also at the collector–base spacer’s oxide. These traps induce generation/recombination centers, and leads to excess non-ideal base currents. Two-dimensional physical simulations have been used to analyse the impact of this degradation mechanism on the device behavior. As a consequence of introducing surface recombination centers at emitter–base and collector–base spacer’s oxide, a non-ideal base current rises up in agreement with the experimental data extracted. As the density of interface traps increases, the charge contributed by these interface states causes a broadening in the base current response and the capacitances deviation.

A new concept of enhanced-mode GaN HEMT using fluorine implantation in the GaN layer

In this paper, a new concept of normally-off HEMT is proposed: it uses for the first time the implantation of Fluorine ions in the GaN layer below the AlGaN/GaN interface rather than in the AlGaN layer. Simulation results show that the proposed method is more effective when it comes to the Fluorine concentration required to achieve normally-off operation.

Scalable normally-off MIS-HEMT using fluorine implantation below the channel

A new normally-off Metal-Insulator-Semiconductor High-Electron-Mobility-Transistor (MIS-HEMT) is proposed. The design is based on the implantation of fluorine ions in the GaN layer below the gate electrode under the AlGaN/GaN interface. Sensitivity analyses are carried out, showing the effects of the fluorine concentration and the thickness of the insulator on the threshold voltage. The limitations and scalability of this technique are pointed out.

P-doped region below the AlGaN/GaN interface for normally-off HEMT

Development of a new design for enhancement-mode AlGaN/GaN HEMT is presented. The normally-off operation was achieved by burying a p-GaN region below the AlGaN/GaN interface only below the gate. Simulation results show that the proposed technique is capable of shifting the threshold voltage to positive values, making the HEMT normally-off. To address the advantages and drawbacks of the proposed structure a comparison with the normally-off Gate Injection Transistor (GIT) was performed. The proposed structure seems to be more effective when it comes to the p-doping concentration required to achieve normally-off operation and offers superior confinement for the two dimensional electron gas. On the other hand, the low forward gate voltage limits the increase of the threshold voltage.

Modeling of the coupling phenomenon between a transmission line and a near-field excitation

In this paper, the coupling phenomenon between the electromagnetic near-field stress and the micro-strip lines connecting the SiGe Heterojunction Bipolar Transistor (HBT), are evaluated by electromagnetic and electrical simulations. A complete electrical model of an electromagnetic near field setup is presented. Each part of this model (injection probe and Printed Circuit Board) are characterized and modeled thank to the ADS software. Comparisons are given between the induced voltage obtained by the electromagnetic simulator HFSS and the induced voltage obtained by using the electrical ADS model, validate the complete electrical model. The originality of this study comes from the generation of a localized electromagnetic field using the near field bench to investigate the reliability of the SiGe HBT. After stress the DC and the high-frequency characteristics are affected by aggression. The comparison between the Direct Power Injection and the near field stress effects indicates that the probe/micro-strip line coupling phenomenon is responsible for the near field stress effects.