A new energy detection ultra-wideband system based on pulse width modulation is proposed. The bit error rate (BER) performance of this new system is slightly worst than that of a pulse position modulation (PPM) system in additive white Gaussian noise channels. In multipath channels, this system does not suffer from cross-modulation interference as PPM, so it can achieve better BER performance than PPM when cross-modulation interference occurs. In addition, when synchronisation errors occur, this system is more robust than PPM.

Providing secure and efficient real-time voice communication in mobile ad hoc network (MANET) environment is a challenging problem. Voice over Internet protocol (VoIP) has originally been developed over the past two decades for infrastructure-based networks. There are strict timing constraints for acceptable quality VoIP services, in addition to registration and discovery issues in VoIP end-points. In MANETs, ad hoc nature of networks and multi-hop wireless environment with significant packet loss and delays present formidable challenges to the implementation. Providing a secure real-time VoIP service on MANET is the main design objective of this paper. The authors have successfully developed a prototype system that establishes reliable and efficient VoIP communication and provides an extremely flexible method for voice communication in MANETs. The authors’ cooperative mesh-based MANET implementation can be used for rapidly deployable VoIP communication with survivable and efficient dynamic networking using open source software.

This paper proposes a technique to accurately estimate radio frequency behaviour of low-power 90 nm amplifier circuits with geometry scalable discrete complementary metal oxide semiconductor (CMOS) modelling. Rather than characterising individual elements, the scheme is able to predict gain, noise and reflection loss of low-noise amplifier (LNA) architectures made with bias, active and passive components. It reduces number of model parameters by formulating dependent functions in symmetric distributed modelling and shows that simple fitting factors can account for extraneous (interconnect) effects in LNA structure. Equivalent-circuit model equations based on physical structure and describing layout parasites are developed for major amplifier elements like metal–insulator–metal (MIM) capacitor, spiral symmetric inductor, polysilicon (PS) resistor and bulk RF transistor. The models are geometry scalable with respect to feature dimensions, i.e. MIM/PS width and length, outer-dimension/turns of planar inductor and channel-width/fingers of active device. Results obtained with the CMOS models are compared against measured literature data for two 1.2 V amplifier circuits where prediction accuracy for RF parameters (S ₂₁, noise figure, S ₁₁, S ₂₂) lies within the range of 92–99%.

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Recently, multiphase machines have been promoted as competitors to their three-phase counterparts in high-power safety-critical drive applications. Among numerous advantages of multiphase induction machine (IM) drives, self-starting and operation under open phase(s) stand as the most salient features. With open phase(s), optimal current control provides disturbance- free operation given a set of objective functions. Although hysteresis current control was merely employed in the literature as it offers a simple controller structure to control the remaining healthy phases, it is not suitable for high-power applications. In the literature, multiple synchronous reference frame (dq) control can be an alternative; however, it requires back and forth transformations with several calculations and additional sophistication. In this paper, a simple technique employing adaptive proportional resonant (PR) current controllers is presented to control a five-phase IM under open-phase conditions. Results for both volt/hertz (V/f) and field oriented control (FOC) systems are presented. Moreover, sensorless operation under fault condition is also demonstrated by estimating the machine speed using a rotor flux-based model reference adaptive system (MRAS) speed estimator. The proposed controllers are experimentally verified and compared. Although FOC provides better dynamic performance, V/f control offers a simpler control structure and a lower number of PR controllers.

The structural and dielectric properties of lead zirconium titanate (PZT) (52:48) ceramic prepared from different synthesis route are discussed in this paper. The PZT green powders were synthesised via three different routes: ceramic, combustion and co-precipitation. The x-ray diffraction (XRD) patterns confirm the pure tetragonal phase formation of PZT for all the different routes adopted by us. Scanning electron microscopy (SEM) micrographs show the surface morphology vary and also grain sizes of PZT prepared from three different routes change from nano to micron size. The Raman intensities were obtained with slight variation in peak intensities and also with slight variations in wave-numbers for all the three PZT samples prepared using different routes. These slightly varied wave-numbers for all the three present samples are however in close proximity with the Raman vibrational modes pertinent for PZT as seen in the literature. The dielectric constant variation with temperature measured for three different powders also shows a considerable change in transition temperature. The structural and dielectric variations are co-related to explain the variations in transition temperature.

A discrete sine transform (DST)-based single-carrier transceiver scheme for broadband wireless communications is proposed and investigated. The proposed scheme uses a DST rather than the conventional discrete Fourier transform (DFT) as a basis function to implement the single-carrier system. The performance of the proposed scheme is studied and compared with the DFT-based single-carrier transceiver scheme and the discrete cosine transform based single-carrier transceiver scheme. Simulation results for single-carrier frequency division multiple access system are presented to demonstrate the effectiveness of the proposed scheme for broadband wireless communications.

Memristor as a novel and emerging electronic device having vast range of applications suffer from poor frequency response and saturation length. In this paper, the authors present a novel and an innovative device structure for the memristor with two active layers and its non-linear ionic drift model for an improved frequency response and saturation length. The authors investigated and compared the I–V characteristics for the proposed model with the conventional memristors and found better results in each case (different window functions) for the proposed dual sided doped memristor. For circuit level simulation, they developed a SPICE model of the proposed memristor and designed some logic gates based on hybrid complementary metal oxide semiconductor memristive logic (memristor ratioed logic). The proposed memristor yields improved results in terms of noise margin, delay time and dynamic hazards than that of the conventional memristors (single active layer memristors).

Multi-walled carbon nanotube (MWCNT) bundles have potentially provided attractive solutions in current nanoscale VLSI interconnects. From fabrication point of view, it is difficult to control the growth of a densely packed bundle having MWCNTs with similar diameters. A realistic bundle is combination of MWCNTs with different number of shells. Thus, this research work focuses on the analytical model of a bundle having the MWCNTs with different number of shells or in turn different diameters [mixed MWCNT bundle (MMB)]. Based on the multi-conductor transmission line theory, an equivalent single conductor (ESC) model is employed for the proposed MMB arrangements. The ESC model of MMB is used to compare the dynamic crosstalk delay with conventionally arranged bundle containing MWCNTs with similar diameters [MWCNT bundle (MB)] under different input transition time and spacing conditions. It is observed that a realistic MMB correctly estimates the crosstalk delay for the different transition time that overestimates the delay of a conventionally arranged MB by 1.35 times. Moreover, the MMB arrangement reduces the overall crosstalk delay by 47.26% compared with the conventional MB arrangements for an inter-bundle spacing ranging from 5 to 30 nm.

The authors consider non-linear state filtering problem in continuous–discrete systems, where the system dynamics is modelled by a stochastic differential equation, and noisy measurements of the system are obtained at discrete time instances. A novel particle method is proposed based on sequential importance sampling. This approach uses a bank of the continuous–discrete unscented Kalman filters (CDUKFs) to obtain the importance proposal distribution, retaining the advantage of the CDUKF in continuous–discrete systems as well as the accuracy of particle filter in highly non-linear systems. Simulation results show that the algorithm outperforms some other benchmarks substantially in estimation accuracy.

Adaptive search is one of the fastest fractal compression algorithms and has gained great success in many industrial applications. By substituting the luminance offset by the range block mean, the authors create a completely new version for both the encoding and decoding algorithms. In this paper, theoretically, they prove that the proposed decoding algorithm converges at least as fast as the existing decoding algorithms using the luminance offset. In addition, they prove that the attractor of the decoding algorithm can be represented by a linear combination of range-averaged images. These theorems are very important contributions to the theory and applications of fractal image compression. As a result, the decoding image can be represented as the sum of the DC and AC component images, which is similar with discrete cosine transform or wavelet transform. To further speed up this algorithm and reduce the complexity of range and domain blocks matching, they propose two improvements in this paper, that is, employing the post-quantisation and geometric neighbouring local search to replace the currently used pre-quantisation and the global search, respectively. The corresponding experimental results show the proposed encoding and decoding algorithms can provide a better performance compared with the existing algorithms.

This paper investigates wound rotor induction machine torque and vibration signals spectra for operation with and without a stator short-circuit or open-circuit winding fault. Analytical expressions that enable the healthy and faulty machine pulsating electromagnetic torque frequencies to be related to shaft speed are derived and validated for operating conditions of interest. A coupled-circuit machine model is used to investigate the healthy and faulty electromagnetic torque signal. Shaft torque and stator frame vibration are measured on a laboratory test rig comprising a 30 kW wound rotor induction machine. It is shown that the existence of a stator winding inherent electrical unbalance or that arising from fault gives rise to a range of pulsating torque frequencies that are transmitted to the machine frame and can be detected in the measured vibration signal. The magnitudes of the resulting vibration components are demonstrated to be largely determined by the unbalance severity and the mechanical system response. The presented experimental results clearly validate the analytical and simulation analysis for the operating range of the investigated industrial machine design.