Small-signal modeling of HBTs using a hybridoptimization/statistical technique

A new formulation for extracting the elements of the small-signal equivalent-circuit model of heterojunction bipolar transistors (HBTs) is proposed in this paper. This approach avoids the main problem of the conventional extraction methods which, in most cases, is the use of brute-force optimization techniques to extract a large number of parameters. At the beginning, this technique first uses the extraction procedure of a low-frequency HBT model. An analytical formulation that allows the reduction of the number of the unknowns of the low-frequency model to only two, which have to be calculated using a suitable optimization technique, is described. This makes the optimization problem much easier to handle and increases the probability for converging to the actual elements of the model, thus avoiding the converging to spurious solutions. Secondly, in order to extend the model to higher frequencies, a statistical approach is proposed to extract parasitic extrinsic elements. An experimental validation is carried out on three HBT devices and satisfactory results are obtained up to 30 GHz     

Energy Efficiency Optimization for Wireless Body Area Networks Under 802.15.6 Standard

Wireless Personal Communications - With the attractive applications in e-Health, a booming interest is granted to wireless body area network (WBAN). Through WBAN, healthcare professionals can...     

Main Effects Ensured by Symmetric Circular Slots Etched on the Radiating Patch of a Compact Monopole Antenna on the Impedance Bandwidth and Radiation Patterns

Wireless Personal Communications - Three compact monopole ultrawideband (UWB) antennas with half-wavelength symmetric circular slots etched on the radiating patch and operating in the UWB spectrum...     

Investigation of new micromachined coplanar probe for near-field microwave microscopy

Microsystem Technologies - The near-field measurement is based generally on the use of purely passive miniature sensors, dedicated to the capture of a component of the electromagnetic field. The...     

Condition number for reliable microwave transistor modeling

An appropriate procedure enabling the evaluation of the sensitivity of a MESFET small-signal model given unavoidable measurement errors is presented in the first section of this article. This technique, which is based on calculation of the condition number, has been applied to an NE 76000 MESFET device. The results obtained enabled us to highlight the difficulties of an accurate MESFET characterization and to predict the equivalent-circuit element errors. In the second part, we introduce a new approach that makes it possible to reduce the sensitivity of the parameters of the model. When applied to the same transistor, this approach enables us to reduce the sensitivity of the model of 30% on average. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14, 174–181, 2004.     

Experiment on the shielding by hollow conducting tubes

This paper describes several practical aspects of shielding provided by openings such as ventilation vents acting as waveguides. Fundamental properties of electromagnetic waves in the interior of a hollow conducting cylindrical tube are presented. Then the guidelines for oscillator's design and harmonic generation by nonlinearities are presented. A consequent wideband setup having low cost and common devices as well as high dynamic range is proposed to perform reliable measurements from 50 MHz to 1.5 GHz. Measurements of circular cylindrical waveguide effectiveness point out the simplicity of the systematic procedure and illustrate the effects of apertures on shielding walls. Shielding loss achieved by these apertures at frequencies below cutoff allows engineers to gain more insight into analysis and design of shields with intentional discontinuities used to exclude and to confine electromagnetic interference.     

Experimental study of the salt gradient solar pond stability

Many natural systems such as oceans, lakes, etc.…, are influenced by the effect of double-diffusive convection. This phenomenon, which is a combination of heat and mass transfer, can destroy the stability of system-flows.In the case of solar ponds the middle layer, that is linearly stratified, acts as a thermal and mass insulator for the lower layer. This middle layer, called the Non-Convective Zone (NCZ), needs special care to avoid convection and to maintain its stability. In fact, due to an excess of heat stored, a thermal gradient occurs within the NCZ. A convective movement appears at the bottom of the stratified-layers and then grows to a double-diffusive convection movement. This movement transforms the stratified-layers into a well mixed layer, reducing the storage capacity of the pond.Laboratory small-scale pond and middle-scale outdoor solar ponds were designed and built to provide both quantitative data and to study the dynamic processes in solar ponds, including the behavior of the gradient zone.Particle Image Velocimetry (PIV) visualization-experiments carried out in the mechanical and energetic laboratory in the engineering school of Tunisia and experiments in the field showed that the instability of solar ponds could be limited by using porous media placed in the lower layer of the stratification.     

Flexible Engineering Tool for Radiofrequency Parameter Identification of RF‐MEMS BAW Filters

In this paper, we present a new specific and customized interface tool with parameter identification of Modified Butterworth‐Van Dyke models for ladder bulk acoustic wave filters. The aforementioned tool is easy to use and flexible because it allows simulations and reengineering to be conducted in an application. A modular design approach is applied to simplify the extension of the proposed tool for different topologies. The proposed tool was validated using measurements from an aluminum‐nitride based ladder BAW filter dedicated to the frequency ranges of the Universal Mobile Telecommunications Service and standards and Wideband Code Division Multiple Access.