Ivan Grech

Body area network for wireless patient monitoring

Patient data monitoring is a key issue for health and disease management. The use of wireless sensors within a body area network (BAN) makes this task seamless and easy. A BAN system is presented, which allows the connectivity of a wide range of heterogeneous body sensors to a portable hub device that is connectable to external networks (IEEE 802.11, GPRS). This BAN is based on the use of Zigbee/IEEE 802.15.4 standard technology and off-the-shelf modules. It is currently being used at the European level for the detection and the prediction of the human physiological state in relation to wakefulness, fatigue, and stress applications in which users carrying out daily activities are monitored in an unobtrusive and comfortable way. Characterised by its low power consumption, low cost, and ability to connect a wide range of heterogeneous sensors, this system can substantially improve the performance of different services, especially those that are health related.

Comparative study of automatic speech recognition techniques

Over the past decades, extensive research has been carried out on various possible implementations of automatic speech recognition (ASR) systems. The most renowned algorithms in the field of ASR are the mel-frequency cepstral coefficients and the hidden Markov models. However, there are also other methods, such as wavelet-based transforms, artificial neural networks and support vector machines, which are becoming more popular. This review article presents a comparative study on different approaches that were proposed for the task of ASR, and which are widely used nowadays.

Analysis of the Spur Characteristics of Edge-Combining DLL-Based Frequency Multipliers

A complete analysis of the spur characteristics of edge-combining delay-locked loop (DLL)-based frequency multipliers is presented in this brief. The novelty of this analysis is the fact that it can be used to estimate the effect of both the in-lock error and the delay-stage mismatch on the spurious level of the frequency multiplier with low computational complexity. In addition, a way to reduce the mismatch between the delay cells in the delay line is discussed via an analytic model and verified by the implementation of a delay cell in a 65-nm CMOS process.

Low voltage SC TDM correlator for the extraction of time delay

This paper proposes a novel technique for the computation of interaural time delay cues which are useful for sound localization. A switched capacitor implementation is used in order to achieve good accuracy. Furthermore, to reduce the area requirement and minimize the accumulation of offset and noise, a time-division multiplexed approach has been used requiring just three fast op amps, one analogue multiplier and a comparator. These blocks have been optimized to operate at a supply voltage of 1.8 V.

Experimental results obtained from analog chips used for extracting sound localization cues

Sound localization, in both azimuth and elevation, using two (left and right) sensors can be carried out by extracting, from the received left and right signals, certain features known as localization cues. This paper presents the test results obtained from three cue extraction chips implemented using standard 0.8 /spl mu/m CMOS technology (threshold voltage: 0.8 V) and operating at a supply voltage of /spl plusmn/0.9 V. The chips consist of an onset detector which determines those portions of the received waveform which contain primarily incident (as opposed to echo) information, a spectral cue front-end and a time delay estimator. Some block level results are presented, together with measured cue values. To our knowledge, these are the first results obtained from such an analog localization hardware, which has been broadly inspired from the biological auditory system.

FPGA-based autonomous parking of a car-like robot using Fuzzy Logic Control

This paper proposes a hardware solution to the problem of autonomous parking of a car-like robot. The proposed system scans for a valid parking space and performs the necessary manoeuvres to park the robot within that space. Parallel and perpendicular parking is achieved by using a fuzzy logic based system that was developed in a simulation environment and subsequently prototyped on a custom built, car-like robot. Fuzzy logic is being proposed as it provides a fast response with a very small hardware footprint. For optimal efficiency, the system was implemented on an FPGA (Field Programmable Gate Array) resulting in a very cost-effective, yet robust system that could be implemented on a full size vehicle.

Support Vector Machines with the priorities method for speaker independent phoneme recognition

A speaker independent phoneme recognition system, based on Support Vector Machines (SVMs) method was improved by adding a priority scheme to forecast the three most likely phonemes. The system helps improve the obtained recognitions rate. For the phoneme recognition system, four multiclass SVMs methods, the All-at-once, One-against-all, One-against-one, and the Directed Acyclic Graph SVM (DAGSVM), were designed. The One-against-one method performed best, achieving an accuracy of 53.70%. This accuracy was further increased to 75.41%, when the second and third priorities were considered in the priorities method. All tests were carried out on the TIMIT database.

Utilization of MEMS Tunable Inductors in the design of RF voltage-controlled oscillators

This paper presents the concept of using a MEMS piezoelectric actuated tunable inductor in the design of a wideband high performance VCO. Furthermore, a model of the tunable inductor is presented to facilitate the VCO design and simulation. In addition, by means of this model important characteristics of the tunable inductor can be derived enabling a design of the VCO to be superior in phase noise and power consumption to one which makes use of conventional capacitive tuning as indicated by the simulation results.

1.6-GHz low power low phase noise quadrature phase locked loop with on chip DC-DC converter for wide tuning range

This paper presents the design of a 1.6 GHz quadrature phase locked loop for GPS applications, operated with a supply voltage of 1.2 V and dissipating a current of less than 5 mA. It is capable of delivering quadrature locked signals in the range from 1.22 GHz to 1.96 GHz with a phase noise response of less than 115 dBc at an offset of 1 MHz from the carrier. The wide tuning range is obtained using an on-chip regulated DC-DC converter clocked by the reference signal, with negligible effect on phase noise and spurious level of the PLL. The design was made using the STMicroelectronics proprietary 0.13 mum HCMOS9 technology design kit.

Analytical, Numerical and Experimental Study of a Horizontal Electrothermal MEMS Microgripper for the Deformability Characterisation of Human Red Blood Cells

Microgrippers are typical microelectromechanical systems (MEMS) that are widely used for micromanipulation and microassembly in both biological and micromanufacturing fields. This paper presents the design, modelling, fabrication and experimental testing of an electrothermal microgripper based on a ‘hot and cold arm’ actuator design that is suitable for the deformability characterisation of human red blood cells (RBCs). The analysis of the mechanical properties of human RBCs is of great interest in the field of medicine as pathological alterations in the deformability characteristics of RBCs have been linked to a number of diseases. The study of the microgripper’s steady-state performance is initially carried out by the development of a lumped analytical model, followed by a numerical model established in CoventorWare® (Coventor, Inc., Cary, NC, USA) using multiphysics finite element analysis. Both analytical and numerical models are based on an electothermomechanical analysis, and take into account the internal heat generation due to the applied potential, as well as conduction heat losses through both the anchor pads and the air gap to the substrate. The models are used to investigate key factors of the actuator’s performance including temperature distribution, deflection and stresses based on an elastic analysis of structures. Results show that analytical and numerical values for temperature and deflection are in good agreement. The analytical and computational models are then validated experimentally using a polysilicon microgripper fabricated by the standard surface micromachining process, PolyMUMPs™ (Durham, NC, USA). The microgripper’s actuation is characterised at atmospheric pressure by optical microscopy studies. Experimental results for the deflection of the microgripper arm tips are found to be in good agreement with the analytical and numerical results, with process-induced variations and the non-linear temperature dependence of the material properties accounting for the slight discrepancies observed. The microgripper is shown to actuate to a maximum opening displacement of 9 μm at an applied voltage of 3 V, thus being in line with the design requirement of an approximate opening of 8 μm for securing and characterising a RBC.