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  • Articles  (2,845)
  • Institution of Engineering and Technology (IET)  (2,845)
  • Electrical Engineering, Measurement and Control Technology  (2,845)
  • 1
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    Non-uniform sampling based on an adaptive level-crossing scheme (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-07
    Description: Level-crossing (LC) analog-to-digital (A/D) converters can efficiently sample certain classes of signals. An LC A/D converter is a real-time asynchronous system, which encodes the information of an analog signal into a sequence of non-uniformly spaced time instants. In particular, this class of A/D converters uses an asynchronous data conversion approach, which is a power efficient technique. In this study, the authors propose adaptive and multi-level adaptive LC sampling models as alternatives to conventional LC schemes and apply an iterative algorithm to improve the reconstruction quality of LC A/D converters. This simulation results show that multi-level adaptive LC outperforms conventional A/D converters such as sigma-delta A/D converters in terms of performance and computational complexity.
    Print ISSN: 1751-9675
    Electronic ISSN: 1751-9683
    Topics: Electrical Engineering, Measurement and Control Technology
    Published by Institution of Engineering and Technology (IET)
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  • 2
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    Epileptic seizure detection by exploiting temporal correlation of electroencephalogram signals (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-07
    Description: Electroencephalogram (EEG) has a great potential for diagnosis and treatment of brain disorders like epileptic seizure. Feature extraction and classification of EEG signals is the crucial task to detect the stages of ictal and interictal signals for treatment and precaution of epileptic patients. However, existing seizure and non-seizure feature extraction techniques are not good enough for the classification of ictal and interictal EEG signals considering the non-abruptness phenomena and inconsistency in different brain locations. In this study, the authors present a new approach for feature extraction and classification by exploiting temporal correlation within EEG signals for better seizure detection as any abruptness in the temporal correlation within a signal represents the transition of a phenomenon. In the proposed methods, they divide an EEG signal into a number of epochs and arrange them into two-dimensional matrix and then apply different transformation/decomposition to extract a number of statistical features. These features are then used as an input into LS-SVM to classify them. Experimental results show that the proposed methods outperform the existing state-of-the-art method for better classification in terms of sensitivity, specificity and accuracy of ictal and interictal period of epilepsy for benchmark datasets and different brain locations.
    Print ISSN: 1751-9675
    Electronic ISSN: 1751-9683
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 3
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    Admissible wavelet packet sub-band-based harmonic energy features for Hindi phoneme recognition (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-07
    Description: In recent years, wavelet packet (WP) transform has been used as an important speech representation tool. WP-based acoustic features have found to be more effective than the short-time Fourier transform (STFT)-based features to capture the information of unvoiced phoneme in continuous speech. However, wavelet features fail to carry the same usefulness to represent the voiced phonemes such as vowels, nasals. This paper proposes new WP sub-band-based features by taking care of harmonic information of voiced speech signal. It has been noted that most of the voiced energy of the speech signal lies in between 250 and 2000 Hz. Thus, the proposed technique emphasises the individual sub-band harmonic energy up to 2 kHz. The speech signal is decomposed into 16 wavelet sub-bands and harmonic energy features are combined with WP cepstral (WPCC) features to enhance the performance of voiced phoneme recogniser. A standard phonetically balanced Hindi database is taken to analyse the performance of the proposed feature set. The noisy phoneme recognition task is also carried out to study the robustness. Significant improvement is obtained with the proposed feature set in voiced phoneme recognition over WPCC and conventional Mel frequency cepstral coefficient.
    Print ISSN: 1751-9675
    Electronic ISSN: 1751-9683
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 4
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    Negative differential resistance in graphene nanoribbon superlattice field-effect transistors (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-21
    Description: Different from researches in two-terminal nanoscale graphene structures, the negative differential resistance (NDR) phenomenon in graphene nanoribbon superlattice (GNSL) field-effect transistors (FETs) is studied in this reported work. Numerical analyses of two types of GNSL FETs with different gate voltages reveal that NDR occurs in some ‘Z’-type GNSL FETs under some gate voltages, which develops NDR research compared with the traditional two-terminal nanoscale structures. Based on these results, two trends are observed: the 3 m + 2 series GNSL FETs easily exhibit NDR, whereas it is more difficult to achieve this phenomenon with narrow FETs. This phenomenon is explained by the transmission coefficient as well as ab-initio calculations of the energy levels, where the entire channel of the FET is considered as a supercell. Through this analysis, the effect of gate control on energy-level localisation is uncovered, and a heterojunction-like explanation is proposed. This new explanation bridges the gap between a novel structure's physical analysis and the general semiconductor device concept, which can also provide inspiration for improving our understanding of novel nanostructure devices.
    Electronic ISSN: 1750-0443
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 5
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    Miniaturised design of coplanar waveguide-fed broadband circularly polarised slot antenna (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: A novel miniaturised design of broadband circularly polarised (CP) antenna using a coplanar waveguide feed is presented. To realise CP characteristic, a pair of inverted-L strips around two opposite corners of the slot is protruded. By properly folding the modified ground plane, the 3-dB axial-ratio (AR) band is shifted to around a lower-frequency location, whereas the input impedance band is shifted downwards through the Y-shaped loading strip. The overall size of the antenna is about 0.34 λ 0 × 0.34 λ 0 × 0.009 λ 0 at 1.7 GHz. Measured results show that the proposed design can deliver 3-dB AR bandwidth of 36.8% (1.55–2.25 GHz) and 10 dB impedance bandwidth of 63.2% (1.17–2.25 GHz).
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 6
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    Miniaturised antenna design with crossed-field elements to radiate strong electromagnetic fields for near-field communications (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: Near-field (NF) communications require strong energy coupling between transmitting and receiving antennas. An antenna design methodology is thus proposed to design the reader antennas that radiate strong evanescent fields in the vicinity of antenna with good radiation efficiency. This concept employs a pair of radiating elements with approximately conjugated input impedances in nature that have large reactance such that the energy will reside in the NF region. In addition, the orientations of the antenna pair are adjusted to form the relationship of crossed-fields in the electric and magnetic field components such that the relationship in Poynting vector can be established in the near zone. Both numerical and experimental results based on an antenna design example for the radio frequency identifications applications are presented to validate the concept.
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 7
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    Low-power ultra-wide band pulse generator based on a PIN diode (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: Radio-frequency identification (RFID) tags (passive kind) are typically not designed to include ultra-wide band (UWB) pulse generators, but may be in the future. The reason is that the very short pulses produced by the RFID tags could be used to estimate their positions with errors of solely a few centimetres using time difference of arrival techniques. Currently, the method most commonly used to estimate tag positions relies on received signal strengths (less accurate). An UWB pulse generator based on a PIN diode is presented in this study. This pulse generator was designed to produce a positive unipolar pulse for each high-to-low transition (1.8 V to 0) it receives at its input. This trigger signal is generated by a microntroller-based battery-free RFID tag. The end result is a pulse with an amplitude of ∼300 mV and a duration of slightly 〈2 ns measured using a 50 Ω load.
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 8
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    Design of phased array antennas with beam switching capability in the near-field focus applications (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: This study presents the design methodology of a phased array antenna whose radiation will focus in the near zone of array aperture by using microstrip feeding circuits. A beam-forming network based on Butler matrix is also implemented to scan the radiation beam along a target area in the near zone, which may improve the energy efficiency and reduce the multipath interferences. The design approach, numerical simulation and experimental measurement over an antenna prototype in the applications of radio-frequency identification are presented to validate the feasibility.
    Print ISSN: 1751-8725
    Electronic ISSN: 1751-8733
    Topics: Electrical Engineering, Measurement and Control Technology
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  • 9
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    Systematic procedure to avoid unintended polarity mismatch in the cascade connection of multiport devices with symmetric feeding lines (2015)
    Institution of Engineering and Technology (IET)
    Details
    Publication Date: 2015-08-25
    Description: The traditional cascading of generalised scattering matrices (GSMs) assumes that the modal sets at the connected ports of a cascaded network are strictly equal. This implies a careful selection of the modal polarities, or the reference systems, of every port. Usually, the connection scheme of every device is known a priori. Then, the individual GSMs are pre-processed, or auxiliary devices, which correct possible modal mismatches at the ports, are included in appropriate positions among the cascade, so that the traditional cascading-by-pairs approach can be directly applied. This scheme clearly complicates the reutilisation of previously calculated GSMs, and mixes the cascading with the solution of the individual building blocks. In this study, a systematic procedure is proposed to define the polarity of the modes at the ports of a device fed with transmission lines or waveguides showing a single or double symmetry. The modified expressions to calculate the scattering parameters of the cascade of two multiport devices, incorporating the regular modal corrections to apply when this criterion is used to define the modal polarity at the ports, is also presented in this study. This strategy is more convenient from the point of view of programming, less error-prone and easier to implement.
    Print ISSN: 1751-8725
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    Topics: Electrical Engineering, Measurement and Control Technology
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  • 10
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    Design and performance analysis of the miniaturised water-filled double-ridged horn antenna for active microwave imaging applications (2015)
    Institution of Engineering and Technology (IET)
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    Publication Date: 2015-08-25
    Description: The design and analysis of a miniaturised double-ridged horn antenna for active microwave imaging application are presented in this study. For such an application, a physically small horn is required. For effective signal penetration, a low frequency of operation (about 1.4 GHz) is selected. An array of these sensors is intended for use in a cylindrical breast imaging system, which is under development in the authors laboratory. The miniaturisation is achieved by loading the double-ridged horn antenna with distilled water ( ε r = 76), a high permittivity, but easily available material. Further size reduction is achieved by reducing the aperture size and flare length in the horn section. The frequency response and both near- and far-field patterns were studied. Two simplified prototypes were fabricated, and as per the system requirements, tested in a cylindrical container filled with distilled water. Measured and simulated reflection and transmission responses are discussed. Measured radiation patterns are compared with the simulated ones to validate the analysis.
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    Topics: Electrical Engineering, Measurement and Control Technology
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