Rachid Allam

Computational estimation of ESD conditions between a charged body and a conductor of floating potential

The paper examines the conditions in which a discharge occurs between a charged body and a floating conductor, in air, at atmospheric pressure. The study, which primarily aimed at simulating a class of hazardous situations quite often met in the operation of electronic circuits, is also of interest to those involved in the research and development of electrostatic technologies for processing of particulate matter: separation of granular mixtures, precipitation of dust, spraying of powders. The boundary element method was employed for the analysis of the electric field in the gap between the charged body and the conductive disk at floating potential, located above a grounded plate. The computations were carried out for bodies of various shapes and sizes; some of them addressed the case of a grounded plate covered with an insulating layer of known permittivity. The data on field distribution represented the input data of another program, which estimated the breakdown conditions of that air-gap. The study enabled the estimation of the energy involved in this type of electrostatic discharge and the prediction of the related hazards.

Cancellation of third order intermodulation currents in a two-stages amplifier topology

This paper gives a detailed description of a linearization technique using a two-stage amplifier. The first stage is used to generate third order intermodulation products (IMD3), which will be added to the input signal of the second stage in order to cancel the IMD3 at its output. The technique effectively improves the linearity of the system. To investigate the effect of IMD3 injection, analytical calculations of the drain currents for the fundamental frequencies f/sub 1/ and f/sub 2/ and for the third order intermodulation currents 2f/sub 1/-f/sub 2/ and 2f/sub 1/-f/sub 1/ are established without and with injection of intermodulation components at the input of the power stage. To evaluate the improvement provided by the proposed technique, a two-tone test at carrier frequency of 900 MHz is performed with a GaAs MESFET. The test procedure is described and measurements show a great improvement of IMD3. A carrier to third intermodulation ratio C/I3 of 55 dBc was achieved for a 19 dBm output power, compared with 25 dBc achieved without the first stage.This paper gives a detailed description of a linearization technique using a two-stage amplifier. The first stage is used to generate third order intermodulation products (IMD3), which will be added to the input signal of the second stage In order to cancel the IMD3 at its output. The technique effectively improves the linearity of the system. To investigate the effect of IMD3 injection, analytical calculations of the drain currents for the fundamental frequencies f/sub 1/ and f/sub 2/ and for the third order intermodulation currents 2f/sub 1/-f/sub 2/ and 2f/sub 2/-f/sub 1/ are established without and with injection of intermodulation components at the input of the power stage. To evaluate the improvement provided by the proposed technique, a two-tone test at carrier frequency of 900 MHz is performed with a MESFET. The test procedure is described and measurements show a great improvement of IMD3. A carrier to third intermodulation ratio C/I3 of 55 dBc was achieved for a 19 dBm output power, compared with 25 dBc achieved without the first stage.

A novel Q-enhanced LC switched-capacitor bandpass filter for digital wireless RF applications

In this paper, a novel architecture for a high-Q switched-capacitor bandpass filter, in 0.35 /spl mu/m CMOS, is presented and tested. The proposed architecture allows high selectivity tuning over a broad band in the radiofrequency range. This circuit is intended to replace surface acoustic wave (SAW) filters; it can be employed in the field of low-cost wireless communications as a subset for professional mobile phones [380-520 MHz]. Experimental results obtained from a prototype show a tunable center frequency range of 268 MHz [240-508 MHz], with quality factors up to 300.

High-Q 8-path bandpass filters design for broadband wireless radio-communication

This paper proposes the design of high-Q tuned 8-path bandpass filters. These circuits, implemented in CMOS technology, allow a high selectivity tunable over a broadband in the radiofrequency range. The proposed architectures are intended to replace the surface acoustic wave (SAW) filters in low-cost wireless radio-communication applications. The prototype of a 8-path bandpass filter has shown quality factors up to 300, and a tunable center frequency range of 285 MHz [240-525 MHz].

Simulation and analytical calculation of the noise figure in HEMT gate mixers

A simplified analytic expression is developed to predict the noise performance of HEMT gate mixers. A nonlinear model of noise was given for theoretical study and implanted in ADS simulator. A contribution of each noise source was presented in this paper. This study is applied to a millimeter-wave HEMT gate mixer. The LO, RF and IF frequencies chosen for this test were 24.5, 28.5 and 4 Ghz respectively. Good agreement is obtained between analytical calculation, simulation and experimental noise figure in single side band NFSSB.

Designing and Modeling Multi-Channel HEMT Gate Mixer

The study of a multichannel HEMT mixer Is presented. We discuss the specific advantages offered by multi-channel AlGaAs/GaAs HEMT for millimeter wave mixer realization. In particular, tailoring of adequate transconductance profile is used to optimize mixer performances. We study also the effect of HEMT non linearities (gate to source capacitance and drain current) on mixer characteristics conversion gain and third order Intermodulation point.

SIMPLIFIED ANALYTICAL EXPRESSION FOR CALCULATING NOISE FIGURE OF HEMT GATE MIXERS

A simplified analytical expression for calculating noise figure of HEMT gate mixers is presented based on superposition method. The contributions of each noise source have been presented. The non-linear behavior of the transistor expressed by the transconductance profile is used to evaluate the noise figure versus LO power. This study is applied to a HEMT gate mixer, tested at 28.5 GHz radio frequency and 4 GHz intermediate frequency. The predicted and the measured noise figures are in good agreement.