Teaching Creative Digital Hardware Design

yesEngineering undergraduates not only need to learn facts, but also how to be creative in the open-ended situations they will encounter in their professional careers. Our final year Honours module gives students a grounding in digital systems design, mainly using VLSI for design entry and simulation. The second half of our module is a design exercise, which has straightforward aspects, but which allows motivated students to undertake progressively open-ended investigations. Our educational framework is guided by recommendations of professional bodies promoting excellence and encouragement of creativity in engineering development. (C) 2013 The Authors. Published by Elsevier Ltd

Vibrational and electronic properties of impurities in semiconductors

Properties of impurities in semiconductors have been investigated by means of absorption spectroscopy. The studies have concentrated not on one topic but on a range of types of impurity behaviour: they may be summarized under three main headings. (1) Fine Structure in Absorption Bands. The shapes and temperature-dependent widths of absorption bands of impurities may be understood qualitatively in terms of vibrational coupling with the lattice. The spectra studied show evidence of Jahn-Teller coupling, one particular form of such an interaction, and it has been found possible in most cases to relate the fine structure observed to features in the phonon spectra of the host lattices. (2) Antiresonances. Since the materials studied are such that in some cases a clear and complete ascription of spectral fine structure can be made in terms of Jahn-Teller coupling, it is possible unambiguously to identify certain other features not previously observed in any systems. These are vibronic anti-resonances, resulting from interference between vibrational levels of the lattice and impurity states of mixed electronic-vibrational nature. In the absence of adequate models, these features are discussed phenomeno- logically. An electronic analogue of these effects, involving spontaneous ionization of excited impurities, has been looked for, but no convincing instances have been found, (3) Photoionization. The charge state and electronic configuration of an impurity depend not only on bonding requirements at the lattice site, but on other factors such as the position of the Fermi level in the bulk medium, and may be changed by photo-excitation. Electrons or holes being removed from ar. impurity and released into crystal bancs results in intense absorption. The form of the absorption cross-section for these processes follows a simple power law near the threshold of ionization, so the value of the ionization energy may be determined quite readily. In this way the positions of a deep level of nickel in zinc selenide and in zinc sulphide have been determined with respect to the conduction and valence bands of these materials. This important information has not been obtained directly for any other transition metal impurity. In addition, fine structure has been seen near the ionization thresholds in these materials. This is due to the coulomb potential of the ionized centre, charged with respect to the lattice, being able to hind holes in hydrogenic orbits. The phonon coupling to this shallow level is found to be much stronger than is observed in absorption bands due to photoionization

A Unique Wavelet-based Multicarrier System with and without MIMO over Multipath Channels with AWGN

yesRecent studies suggest that multicarrier systems using wavelets outperform conventional OFDM systems using the FFT, in that they have well-contained side lobes, improved spectral efficiency and BER performance, and they do not require a cyclic prefix. Here we study the wavelet packet and discrete wavelet transforms, comparing the BER performance of wavelet transform-based multicarrier systems and Fourier based OFDM systems, for multipath Rayleigh channels with AWGN. In the proposed system zero-forcing channel estimation in the frequency domain has been used. Results confirm that discrete wavelet-based systems using Daubechies wavelets outperform both wavelet packet transform- based systems and FFT-OFDM systems in terms of BER. Finally, Alamouti coding and maximal ratio combining schemes were employed in MIMO environments, where results show that the effects of multipath fading were greatly reduced by the antenna diversity

Numerical study of performance of porous fin heat sink of functionally graded material for improved thermal management of consumer electronics

YesThe ever-increasing demand for high performance electronic and computer systems has unequivocally called for increased microprocessor performance. However, increasing microprocessor performance requires increasing the power and on-chip power density of the microprocessor, both of which are associated with increased heat dissipation. In recent times, thermal management of electronic systems has gained intense research attention due to increased miniaturization trend in the electronics industry. In the paper, we present a numerical study on the performance of a convective-radiative porous heat sink with functionally graded material for improved cooling of various consumer electronics. For the theoretical investigation, the thermal property of the functionally graded material is assumed as a linear and power-law function. We solved the developed thermal models using the Chebyshev spectral collocation method. The effects of inhomogeneity index of FGM, convective and radiative parameters on the thermal behaviour of the porous heat sink are investigated. The present study shows that increase in the inhomogeneity index of FGM, convective and radiative parameter improves the thermal efficiency of the porous fin heat sink. Moreover, for all values of Nc and Rd, the temperature gradient along the fin of FGM is negligible compared to HM fin in both linear and power-law functions. For comparison, the thermal predictions made in the present study using Chebyshev spectral collocation method agrees excellently with the established results of Runge-Kutta with shooting and homotopy analytical method.Supported in part from PhD sponsorship of the first author by the Tertiary Education Trust Fund of the Federal Government of Nigeria

Secondary user undercover cooperative dynamic access protocol for overlay cognitive radio networks

YesA secondary cooperative overlay dynamic spectrum access protocol in cognitive radio networks is proposed, allowing secondary users to access the primary system using full power without causing harmful interference to primary users. Moreover, an enhancement in the primary system will be achieved as a result of secondary relaying of primary messages. A detailed description of the protocol is given and illustrated with network scenarios

Design of very compact Combline Band-Pass Filter for 5G applications

NoIn this paper, a compact microstrip band-pass filter (BPF) covering the 3.4 to 3.8 GHz spectrum bandwidth for 5G wireless communications is presented. The planar filter uses three resonators, each terminated by a via to hole ground at one end and a capacitor at the other end with 50 Ω transmission line impedances for input and output terminals. The coupling between the lines is adjusted to resonate at the centre frequency with third-order band-pass Butterworth properties. The proposed combline filter is designed on an alumina substrate with a relative dielectric constant of 9.8 and a very small size of 9×5×1.2 mm3. The proposed filter is simulated and optimized using CST microwave studio software.European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424, UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/

Performance Evaluation of Spatial Modulation and QOSTBC for MIMO Systems

YesMultiple-input multiple-output (MIMO) systems require simplified architectures that can maximize design parameters without sacrificing system performance. Such architectures may be used in a transmitter or a receiver. The most recent example with possible low cost architecture in the transmitter is spatial modulation (SM). In this study, we evaluate the SM and quasi-orthogonal space time block codes (QOSTBC) schemes for MIMO systems over a Rayleigh fading channel. QOSTBC enables STBC to be used in a four antenna design, for example. Standard QO-STBC techniques are limited in performance due to self-interference terms; here a QOSTBC scheme that eliminates these terms in its decoding matrix is explored. In addition, while most QOSTBC studies mainly explore performance improvements with different code structures, here we have implemented receiver diversity using maximal ratio combining (MRC). Results show that QOSTBC delivers better performance, at spectral efficiency comparable with SM

Recent developments of reconfigurable antennas for 4G and 5G wireless communications: A survey

YesReconfigurable antennas play important roles in smart and adaptive systems and are the subject of many research studies. They offer several advantages such as multifunctional capabilities, minimized volume requirements, low front-end processing efforts with no need for a filtering element, good isolation, and sufficient out-ofband rejection; these make them well suited for use in wireless applications such as fourth generation (4G) and fifth generation (5G) mobile terminals. With the use of active materials such as microelectromechanical systems (MEMS), varactor or p-i-n (PIN) diodes, an antenna’s characteristics can be changed through altering the current flow on the antenna structure. If an antenna is to be reconfigurable into many different states, it needs to have an adequate number of active elements. However, a large number of high-quality active elements increases cost, and necessitates complex biasing networks and control circuitry. We review some recently proposed reconfigurable antenna designs suitable for use in wireless communications such as cognitiveratio (CR), multiple-input multiple-output (MIMO), ultra-wideband (UWB), and 4G/5G mobile terminals. Several examples of antennas with different reconfigurability functions are analyzed and their performances are compared. Characteristics and fundamental properties of reconfigurable antennas with single and multiple reconfigurability modes are investigated.European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424

Compact Dielectric Resonator Antenna with Band-Notched Characteristics for Ultra-Wideband Applications.

yesIn this paper, a compact dielectric resonator antenna (DRA) with band-notched characteristics for ultra-wideband applications is presented. A comprehensive parametric study was carried out using CST Microwave Studio Suite TM 2011 to analyze and optimize the characteristics of the proposed antenna. Three shapes for the coupling slot were investigated. Simulation results show that the proposed DRA had a −10 dB impedance bandwidth of 23% from 9.97 GHz to 12.558 GHz, and a maximum gain of 7.23 dBi. The antenna had a notched band centered at 10.57 GHz, which increased the reflection coefficient by 23.5 dB, and reduced the gain by 6.12 dB. The optimized designs were verified by experimental tests on fabricated samples

Dual Segment S-Shaped Aperture-Coupled Cylindrical Dielectric Resonator Antenna for X-Band Applications.

yesA new low-cost dual-segmented dielectric resonator (DR) antenna design is proposed for wideband applications in the X-band region. Two DRs coupled to an S-shaped slot introduce interesting features. The antenna performance was characterized in terms of the reflection coefficient, gain, and radiation pattern, and detailed simulation studies indicate excellent antenna performance from 7.66 GHz to 11.2 GHz (37.5% fractional bandwidth) with a maximum gain of 6.0 dBi at 10.6 GHz while the fabricated prototype has a matched bandwidth from 7.8 GHz to 11.85 GHz (41% fractional bandwidth) and maximum gain of 6dBi. The antenna is compact, size 1 x 0.83 x 0.327 time the wavelength at 10 GHz. The two DR segments may be located on the same side or on opposite sides of the substrate, giving respectively improved gain or more uniform field patterns. Experimental testing of the prototype performance showed reasonable agreement with the predicted performance