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The purpose of this work is to study the capability of heuristic algorithms like genetic algorithm to estimate the electron transport parameters of the Gallium Arsenide (GaAs). Also, the paper provides a simple but complete electron mobility model for the GaAs based on the genetic algorithm that can be suitable for use in simulation, optimization and design of GaAs‐based electronic and optoelectronic devices.

The genetic algorithm as a powerful heuristic optimization technique is used to approximate the electron transport parameters during the model development.

The capability of the model to approximate the electron transport properties of Gallium Arsenide is tested using experimental and Monte Carlo data. Results show that the genetic algorithm based model can provide a reliable estimate of the electron mobility in Gallium Arsenide for a wide range of temperatures, concentrations and electric fields. Based on the obtained results, this paper shows that the genetic algorithm can be a useful tool for the estimation of the transport parameters of semiconductors.

For the first time, the genetic algorithm is used to calculate the electron transport parameters in Gallium Arsenide. A complete electron mobility model for a wide range of temperatures, doping concentrations, compensation ratios and electric fields is developed.

A material that could well replace the silicon chip in future generations of aircraft communications, radar and early warning systems, is now under active development in various military and industrial establishments. Speed is the essence in any communication system and it has been determined that electrons will move six times faster through gallium arsenide (GaAs) than through silicon. GaAs substrates also have the important characteristic of having high resistivity. The superiority of silicon over gallium arsenide at the present time is principally due to the considerable developments that have taken place over many years in Silicon Valley, California, and other research centres. This has resulted in GaAs integrated circuits supporting only several hundred components compared with the near 500,000 in silicon (si).

The set of properties required for microwave packaging materials intended for aerospace applications is discussed in relation to the current range of materials that are commercially available. Initiatives are being taken to replace kovar, the established packaging material, with substitutes which are lighter, stiffer and offer superior heat‐sinking. Promising in this regard are new family of beryllium‐beryllia and also silicon‐aluminium (Si‐Al) alloys high in silicon, with ratios of constituents chosen such that they optimally complement gallium arsenide MMIC devices and alumina circuit boards. Both types of material are relatively easy to machine and electroplate. Demonstrator microwave amplifier modules incorporating the Si‐Al alloys have been designed for space applications and have been successfully produced and tested. The manufacturing technology that has been developed for this purpose is described.

Power amplifiers (PAs) play an important role in wireless communications because they dominate system performance. High-linearity broadband PAs are of great value for potential use in multi-band system implementation. The purpose of this paper is to present a cascode power amplifier architecture to achieve high power and high efficiency requirements for 4.2∼5.4 GHz applications.

A common emitter (CE) configuration with a stacked common base configuration of heterojunction bipolar transistor (HBT) is used to achieve high power. T-type matching network is used as input matching network. To increase the bandwidth, the output matching networks are implemented using the two L-networks.

By using the proposed method, the stacked PA demonstrates a maximum saturated output power of 26.2 dBm, a compact chip size of 1.17 × 0.59 mm² and a maximum power-added efficiency of 46.3 per cent. The PA shows a wideband small signal gain with less than 3 dB variation over working frequency. The saturated output power of the proposed PA is higher than 25 dBm between 4.2 and 5.4 GHz.

The technology adopted for the design of the 4.2-to-5.4 GHz stacked PA is the 2-µm gallium arsenide HBT process. Based on the proposed method, a better power performance of 3 dB improvement can be achieved as compared with the conventional CE or common-source amplifier because of high output stacking impedance.

This paper aims to implement a new high output power fully integrated 23.1 to 27.2 GHz gallium arsenide heterojunction bipolar transistor power amplifier (PA) to meet the stringent linearity requirements of LTE systems.

The direct input power dividing technique is used on the chip. Broadband input and output matching techniques are used for broadband Doherty operation.

The PA achieves a small-signal gain of 22.8 dB at 25.1 GHz and a saturated output power of 24.3 dBm at 25.1 GHz with a maximum power added efficiency of 31.7%. The PA occupies 1.56 mm² (including pads) and consumes a maximum current of 79.91 mA from a 9 V supply.

In this paper, the author proposed a novel direct input dividing technique with broadband matching circuits using a low Q output matching technique, and demonstrated a fully-integrated Doherty PA across frequencies of 23.1∼27.2 GHz for long term evolution-license auxiliary access (LTE-LAA) handset applications.

The purpose of this paper is to conduct a numerical study of the effect of magnetic field on thermocapillary convection of a two layered system of Newtonian fluids, confined in a rectangular cavity. The flow within the cavity is subject to the horizontal temperature gradient. Attention is focused on how the heat transfer and flow properties are affected subject to the applied magnetic field, particularly in the lower layer. For this purpose, the fluid combinations of di‐Boron Trioxide (B₂O₃) over Gallium Arsenide GaAs (III‐V), and Silicon oil 10 cSt over Fluorinert FC 70 are considered in the present study.

The non‐linear two‐dimensional vorticity transport equations along with the energy equations are solved for the two liquid layers using the Alternate Direct Implicit method, whereas the elliptic partial differential equations of the stream function are solved using the Successive Over Relaxation method.

It was found that despite the significant reduction of flow in the two layers, the number of cells in the lower layer increases with the increase in Hartmann number Ha. However, the flow intensity decreases with the increase in Hartmann number. This decrease is more pronounced in the lower layer, as compared to the upper layer. The numerical scheme employed for the solution is found to be in good agreement with the previous work.

The analysis is made for two layer liquid system with undeformable interface and free surface. The detailed study of the effect of magnetic field on oscillatory Marangoni convection in two layer system with deformable interface is left for future work.

The approach is useful in optimizing the flow properties of the fluids in a two layer system, particularly the lower layer, to yield the results of potential practical interest.

The results of the study may be of some interest to researchers in the field of semiconductor technology, as the melt control is intensively investigated for the development in the manufacture of defect‐free semiconductors and crystals.

Modern fighter aircraft using active electronically scanned array (AESA) fire control radars are able to detect and track targets at long ranges, in the order of 50 nautical miles or more. Low observable or stealth technology has contested the radar capabilities, reducing detection/tracking ranges roughly to one-third (or even less, for fighter aircraft radar). Hence, infrared search and track (IRST) systems have been reconsidered as an alternative to the radar. This study aims to explore and compare the capabilities and limitations of these two technologies, AESA radars and IRST systems, as well as their synergy through sensor fusion.

The AESA radar range is calculated with the help of the radar equation under certain assumptions, taking into account heat dissipation requirements, using the F-16 fighter as a case study. Concerning the IRST sensor, a new model is proposed for the estimation of the detection range, based on the emitted infrared radiation caused by aerodynamic heating.

The maximum detection range provided by an AESA radar could be restricted because of the increased waste heat which is produced and the relevant constraints concerning the cooling capacity of the carrying aircraft. On the other hand, IRST systems exhibit certain advantages over radars against low observable threats. IRST could be combined with a datalink with the help of data fusion, offering weapons-quality track.

An original approach is provided for the IRST detection range estimation. The AESA/IRST comparison offers valuable insight, while it allows for more efficient planning, at the military acquisition phase, as well as at the tactical level.

This paper discusses the increasing activity being directed towards microminiature multichip module packaging. It shows new substrate materials that are being investigated, including multilayer thin‐film ceramics and silicon wafers. Wire bonding, tape‐automated bonding (TAB), and flip device termination techniques are covered. Particular attention is given to the use of multichip modules for advanced data processing applications.

The recent copy of the ACM Computing Surveys, Vol. 14, 3, 1982, deals with some of the problems of the “User‐Interface”. All who use computer systems, and particularly the Cybernetician, are concerned at the way in which information is stored, retrieved and edited. All too often, untried methods are implemented, and software engineers fail to search the literature for established and efficient techniques. Two papers in this issue of Computing Surveys brings together details of current editing and user interface developments. The first paper is about using and implementing interactive editing systems and the second, concerned with document formatting systems. Here interactive editing refers to the process of making changes to documents by direct, rather than batched, communication with the computer, during which the user's actions are interleaved with the computer's feedback on the results of each action.

A new micromachining technology of mechanically fixed and thermally insulated cantilevers, bridges and islands was developed to be used for design of GaAs heterostructure based microelectromechanical systems (MEMS) devices. Based on the micromachining technology, two different MEMS devices were designed and analyzed. The first one was micromechanical thermal converter (MTC) and the second one was a micromechanical coplanar waveguide (MCPW). The basic electro‐thermal as well as microwave properties of the MEMS devices designed are investigated. The results obtained are also supported by simulation. The advantages of the fixed micromechanical structures in the field of design of new MEMS devices are discussed.