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  • Conference paper
    Logesparan L, Rodriguez-Villegas E, 2010,

    Improving phase congruency for EEG data reduction

    , 32nd International Conference of the IEEE Engineering in Medicine and Biology Society, Publisher: IEEE, Pages: 642-645

    Real signals are often corrupted by noise. In applications where the noise power spectrum is variable with time, dynamic noise estimation and compensation can potentially improve the performance of signal processing algorithms. One such application is scalp EEG monitoring in epilepsy, where the electrical activity generated by cranio-facial muscle contraction and expansion, often obscures the measured brainwave signals. This work presents a data reduction algorithm which is based on differentiating interictal from normal background activity, in epileptic scalp EEG signals, using a modified phase congruency technique. The modification is based on dynamically estimating muscle activity from the signal and incorporating this estimation in phase congruency computations. The proposed algorithm identifies 90%of interictal spikes whilst transmitting only 45% of EEG data. This is in the order of 15% improvement in data reduction when compared to the performance obtained with the state-of-the-art denoised phase congruency-which calculates a constant noise threshold-applied to the same dataset.

  • Conference paper
    Casson AJ, Logesparan L, Rodriguez Villegas E, 2010,

    An introduction to future truly wearable medical devices—from application to ASIC

    , 32nd international conference of the IEEE Engineering in Medicine and Biology Society, Pages: 3430-3431

    This talk will provide an introduction to the "Towards future truly wearable medical devices: from application to ASIC" mini-symposium. For user comfort and acceptance long term physiological sensors must be discrete, comfortable and easy to use. These requirements place stringent limits on all aspects of the system design: from the overall application aim, to power generation issues, to low power electronic design techniques. For successful devices design issues in all of these areas must be solved simultaneously. The work here presents an overview and introduction to these topics.

  • Conference paper
    Abdulghani AM, Rodriguez Villegas E, 2010,

    Compressive sensing: From "compressing while sampling" to 'compressing and securing while sampling

    , 32nd Annual International Conference of the IEEE EMBS, Publisher: IEEE, Pages: 1127-1130, ISSN: 1557-170X

    In a traditional signal processing system sampling is carried out at a frequency which is at least twice the highest frequency component found in the signal. This is in order to guarantee that complete signal recovery is later on possible. The sampled signal can subsequently be subjected to further processing leading to, for example, encryption and compression. This processing can be computationally intensive and, in the case of battery operated systems, unpractically power hungry. Compressive sensing has recently emerged as a new signal sampling paradigm gaining huge attention from the research community. According to this theory it can potentially be possible to sample certain signals at a lower than Nyquist rate without jeopardizing signal recovery. In practical terms this may provide multi-pronged solutions to reduce some systems computational complexity. In this work, information theoretic analysis of real EEG signals is presented that shows the additional benefits of compressive sensing in preserving data privacy. Through this it can then be established generally that compressive sensing not only compresses but also secures while sampling.

  • Conference paper
    Casson AJ, Rodriguez Villegas E, 2010,

    Low power signal processing electronics for wearable medical devices

    , 32nd international conference of the IEEE Engineering in Medicine and Biology Society, Pages: 3439-3440

    Custom designed microchips, known as Application Specific Integrated Circuits (ASICs), offer the lowest possible power consumption electronics. However, this comes at the cost of a longer, more complex and more costly design process compared to one using generic, off-the-shelf components. Nevertheless, their use is essential in future truly wearable medical devices that must operate for long periods of time from physically small, energy limited batteries. This presentation will demonstrate the state-of-the-art in ASIC technology for providing online signal processing for use in these wearable medical devices.

  • Conference paper
    Logesparan L, Rodriguez Villegas E, 2010,

    Improving phase congruency for EEG data reduction

    , 32nd Annual International Conference of the IEEE EMBS, Publisher: IEEE, Pages: 642-645, ISSN: 1557-170X

    Real signals are often corrupted by noise. In applications where the noise power spectrum is variable with time, dynamic noise estimation and compensation can potentially improve the performance of signal processing algorithms. One such application is scalp EEG monitoring in epilepsy, where the electrical activity generated by cranio-facial muscle contraction and expansion, often obscures the measured brainwave signals. This work presents a data reduction algorithm which is based on differentiating interictal from normal background activity, in epileptic scalp EEG signals, using a modified phase congruency technique. The modification is based on dynamically estimating muscle activity from the signal and incorporating this estimation in phase congruency computations. The proposed algorithm identifies 90%of interictal spikes whilst transmitting only 45% of EEG data. This is in the order of 15% improvement in data reduction when compared to the performance obtained with the state–of–the–art denoised phase congruency—which calculates a constant noise threshold—applied to the same dataset.

  • Conference paper
    Saremi-Yarahmadi S, Murphy OH, Toumazou C, 2010,

    RF Inductive Sensors for Detection of Change in the Ionic Strength and pH of Liquid Samples

    , International Symposium on Circuits and Systems Nano-Bio Circuit Fabrics and Systems (ISCAS 2010), Publisher: IEEE, Pages: 2279-2282, ISSN: 0271-4302
  • Journal article
    Chen G, Rodriguez-Villegas E, 2010,

    System-Level Design Trade-offs for Truly Wearable Wireless Medical Devices

    , 2010 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC), Pages: 1441-1444, ISSN: 1557-170X
  • Conference paper
    He C, Kiziroglou ME, Yates DC, Yeatman EMet al., 2010,

    MEMS energy harvester for wireless biosensors

    , Pages: 172-175
  • Journal article
    Casson AJ, Yates DC, Smith SJM, Duncan JS, Rodriguez-Villegas Eet al., 2010,

    Wearable Electroencephalography

    , IEEE Engineering in Medicine and Biology Magazine, Vol: 29, Pages: 44-56

    The electroencephalogram (EEG) is a classic noninvasive method for measuring a person's brainwaves and is used in a large number of fields: from epilepsy and sleep disorder diagnosis to brain–computer interfaces (BCIs). Electrodes are placed on the scalp to detect the microvolt-sized signals that result from synchronized neuronal activity within the brain. Current long-term EEG monitoring is generally either carried out as an inpatient in combination with video recording and long cables to an amplifier and recording unit or is ambulatory. In the latter, the EEG recorder is portable but bulky, and in principle, the subject can go about their normal daily life during the recording.

  • Conference paper
    Abdulghani, CASSON, RODRIGUEZ VILLEGAS E, 2010,

    Quantifying the performance of compressive sensing on scalp EEG signals

    , 3rd International Symposium on Applied Sciences in Biomedical and Communication Technologies (ISABEL)

    Compressive sensing is a new data compression paradigm that has shown significant promise in fields such as MRI. However, the practical performance of the theory very much depends on the characteristics of the signal being sensed. As such the utility of the technique cannot be extrapolated from one application to another. Electroencephalography (EEG) is a fundamental tool for the investigation of many neurological disorders and is increasingly also used in many non-medical applications, such as Brain-Computer Interfaces. This paper characterises in detail the practical performance of different implementations of the compressive sensing theory when applied to scalp EEG signals for the first time. The results are of particular interest for wearable EEG communication systems requiring low power, real-time compression of the EEG data.

  • Journal article
    Rodriguez-Villegas E, 2009,

    A Low-Power Wide-Range I-V Converter for Amperometric Sensing Applications

    , IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, Vol: 3, Pages: 432-436, ISSN: 1932-4545
  • Journal article
    Casson AJ, Rodriguez-Villegas E, 2009,

    Toward Online Data Reduction for Portable Electroencephalography Systems in Epilepsy

    , IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, Vol: 56, Pages: 2816-2825, ISSN: 0018-9294
  • Journal article
    Rodriguez-Villegas E, Corbishley P, Lujan-Martinez C, Sanchez-Rodriguez Tet al., 2009,

    An ultra-low-power precision rectifier for biomedical sensors interfacing

    , SENSORS AND ACTUATORS A-PHYSICAL, Vol: 153, Pages: 222-229, ISSN: 0924-4247
  • Journal article
    Rodriguez-Villegas E, Xu M, 2009,

    Simplifying the Design of Sigma Delta Modulators Using FGMOS Transistors

    , IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS, Vol: 56, Pages: 1313-1325, ISSN: 1549-8328
  • Journal article
    Yates DC, Holmes AS, 2009,

    Preferred Transmission Frequency for Size-Constrained Ultralow-Power Short-Range CMOS Oscillator Transmitters

    , IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS, Vol: 56, Pages: 1173-1181, ISSN: 1549-8328
  • Conference paper
    Mardell JP, Witkowski M, Spence R, 2009,

    Detecting Search and Rescue Targets in Moving Aerial Images Using Eye-Gaze

    , Communication by Gaze Interaction (COGAIN), Pages: 67-70

    Eye gaze performance is measured and characterised in the context of moving image inspection. The application domain is that of Wilderness Search and Rescue. Here, moving terrain images captured by an Unmanned Aerial Vehicle (UAV) must be inspected accurately and with minimal delay to attempt identification of a missing person or related artefacts.An exploratory pilot experiment using images of real terrain established the extent of gaze for North and East movement of the UAV at four different speeds, and also for the condition in which a sequence of static frames of the same moving image was inspected. Observation were also made of the gaze tracking behaviour initiated by a potential target.Suggestions are made about the way in which the observation and characterization of eye gaze may be harnessed to enhance the success of target detection in a search and rescue context.

  • Conference paper
    Hizon JR, Rodriguez-Villegas E, 2009,

    Design Tradeoffs in a Triode Transconductor for Low Voltage Zero-IF Channel Select Filters

    , 52nd IEEE International Midwest Symposium on Circuits and Systems, Publisher: IEEE, Pages: 82-85, ISSN: 1548-3746
  • Conference paper
    He C, Arora A, Kiziroglou ME, Yates DC, O'Hare D, Yeatman EMet al., 2009,

    MEMS Energy Harvesting Powered Wireless Biometric Sensor

    , Wearable and Implantable Body Sensor Networks, 2009. BSN 2009. Sixth International Workshop on, Pages: 207-212

    One of the main challenges in developing wireless biometric sensors is the requirement for integration of various systems into a very compact device. Such systems include sensing units, conditioning electronics, transmitters and power supplies. In this work, a novel system integration architecture is presented. A unique feature of this new architecture is that the sub-systems are selected and designed for direct output-to-input connection. An array of active pH sensors is used to transform a pH level to an electrical potential in the range of 0 - 2 Volts. This signal is amplified by an electrostatic energy harvester suitable for human motion operation. The amplified signal drives a custom LC transmitter specially designed to suit the harvester output. A system of notable simplicity is achieved and may serve as a demonstrator for other wireless sensors.

  • Conference paper
    Rodriguez-Villegas E, Aguilar-Pelaez E, Chen G, Duncan Jet al., 2009,

    APNEA DETECTOR TO PREVENT SUDEP

    , Publisher: WILEY-BLACKWELL PUBLISHING, INC
  • Journal article
    Casson AJ, Luna E, Rodriguez-Villegas E, 2009,

    Performance metrics for the accurate characterisation of interical spike detection algorithms

    , Journal of Neuroscience Methods, Vol: 177, Pages: 479-487
  • Conference paper
    Abdulghani AM, Casson AJ, Rodriguez-Villegas E, 2009,

    Quantifying the Feasibility of Compressive Sensing in Portable Electroencephalography Systems

    , 5th International Conference on Foundation of Augmented Cognition, Publisher: SPRINGER-VERLAG BERLIN, Pages: 319-328, ISSN: 0302-9743

    The EEG for use in augmented cognition produces large amounts of compressible data from multiple electrodes Mounted on the scalp. This huge amount of data needs to be processed, stored and transmitted and consumes large amounts of power. In turn this leads to physically large EEG units with limited lifetimes which limit the ease of use, and robustness and reliability of the recording. This work investigates the Suitability of compressive sensing, a recent development in compression theory, for providing online data reduction to decrease the amount of system power required. System modeling which incorporates a review of state-of-the-art EEG Suitable integrated circuits shows that compressive sensing offers no benefits when using an EEG system with only a few channels. It can, however, lead to significant power savings in situations where more than approximately 20 channels are required. This result shows that the further investigation and optimization of compressive sensing algorithms for EEG data is justified.

  • Journal article
    Lopez-Morillo E, Carvajal RG, Munoz F, El Gmili H, Lopez-Martin A, Ramirez-Angulo J, Rodriguez-Villegas Eet al., 2008,

    A 1.2-V 140-nW 10-bit Sigma-Delta Modulator for Electroencephalogram Applications

    , IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, Vol: 2, Pages: 223-230, ISSN: 1932-4545
  • Conference paper
    Casson AJ, Rodriguez-Villegas E, 2008,

    Considerations on analogue to digital converter architectures for EEG acquisition in Augmented Cognition applications

    , 52nd annual meeting of the Human Factors and Ergonomics Society, Publisher: Human Factors and Ergonomics Society, Pages: 197-201, ISSN: 1071-1813

    Analogue to Digital Conversion (ADC) forms an essential part of EEG systems allowing signals to be represented in the digital domain and processed by a computer. For wearable, battery powered applications, such as those envisioned in augmented cognition, power consumption is a key design parameter. This paper investigates the ADC specifications that are used for typical augmented cognition applications and links these to a review of ADC topologies and performance. It is found that the ADC power consumption is an exponential function of the resolution of the ADC, but that the resolution required is often over estimated. Also, care is required when considering oversampling converters to ensure that the power consumption of decimation is accounted for.

  • Conference paper
    Casson AJ, Rodriguez-Villegas E, 2008,

    Generic vs custom; analogue vs digital: on the implementation of an online EEG signal processing algorithm

    , 30th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society, Publisher: IEEE, Pages: 5876-5880, ISSN: 1557-170X
  • Conference paper
    Casson AJ, Rodriguez-Villegas E, 2008,

    An inverse filter realisation of a single scale Inverse Continuous Wavelet Transform

    , IEEE International Symposium on Circuits and Systems, Publisher: IEEE, Pages: 904-907, ISSN: 0271-4302
  • Journal article
    Corbishley P, Rodriguez-Villegas E, 2008,

    Breathing detection: Towards a miniaturized, wearable, battery-operated monitoring system

    , IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, Vol: 55, Pages: 196-204, ISSN: 0018-9294
  • Conference paper
    Casson AJ, Smith S, Duncan JS, Rodriguez-Villegas Eet al., 2008,

    Wearable EEG: what is it, why is it needed and what does it entail?

    , 30th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society, Publisher: IEEE, Pages: 5867-+, ISSN: 1557-170X
  • Conference paper
    Casson AJ, Rodriguez-Villegas E, 2008,

    On data reduction in EEG monitoring: comparison between ambulatory and non-ambulatory recordings

    , 30th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society, Publisher: IEEE, Pages: 5885-5888, ISSN: 1557-170X
  • Conference paper
    Aguilar-Pelaez E, Rodríguez-Villegas E, 2008,

    Low-power differential photoplethysmographic pulse transit time detector for ambulatory cardiovascular monitoring

    , Pages: 1104-1107
  • Patent
    Rodriguez-Villegas E, Yates D, 2008,

    Apparatus and method for obtaining EEG data

    , WO/2008/015449
  • Journal article
    Corbishley P, Rodriguez-Villegas E, 2007,

    A Nanopower Bandpass Filter for Detection of an Acoustic Signal in a Wearable Breathing Detector

    , IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS, Vol: 1, Pages: 163-171, ISSN: 1932-4545
  • Conference paper
    Casson A, Rodriguez-Villegas E, 2007,

    Data reduction techniques to facilitate wireless and long term AEEG epilepsy monitoring

  • Conference paper
    Yates D C, Casson A, Rodriguez-Villegas E, 2007,

    Low Power Technology for Wearable Cognition Systems

  • Journal article
    Rodriguez-Villegas E, Jimenez M, Carvajal RG, 2007,

    On dealing with the charge trapped in floating-gate MOS (FGMOS) transistors

    , IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-EXPRESS BRIEFS, Vol: 54, Pages: 156-160, ISSN: 1549-7747
  • Conference paper
    Casson AJ, Yates DC, Patel S, Rodriguez-Villegas Eet al., 2007,

    An analogue bandpass filter realisation of the Continuous Wavelet Transform

    , Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE, Publisher: IEEE, Pages: 1850-1854, ISSN: 1557-170X
  • Conference paper
    Casson AJ, Yates DC, Patel S, Rodriguez-Villegas Eet al., 2007,

    Algorithm for AEEG data selection leading to wireless and long term epilepsy monitoring

    , Engineering in Medicine and Biology Society, 2007. EMBS 2007. 29th Annual International Conference of the IEEE, Pages: 2456-2459, ISSN: 1557-170X
  • Conference paper
    Yates DC, Rodriguez-Villegas E, 2007,

    A key power trade-off in wireless EEG headset design

    , 3rd International IEEE/EMBS Conference on Neural Engineering, Publisher: IEEE, Pages: 453-+
  • Conference paper
    Rodriguez-Villegas E, 2007,

    A low-power wide range transimpedance amplifier for biochemical sensing

    , 29th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society, Publisher: IEEE, Pages: 2673-2676, ISSN: 1094-687X
  • Conference paper
    Xu M, Rodriguez-Villegas E, 2007,

    A 1V low power Sigma-Delta modulator based on Floating Gate MOS transistors

    , 18th European Conference on Circuit Theory Design, Publisher: IEEE, Pages: 48-51
  • Conference paper
    Casson AJ, Yates DC, Patel S, Rodriguez-Villegas Eet al., 2007,

    An analogue bandpass filter realisation of the Continuous Wavelet Transform.

    , Pages: 1850-1854, ISSN: 1557-170X

    The Continuous Wavelet Transform (CWT) is a highly useful signal processing technique for which low power implementations are desirable, for example to allow the transform to be used in battery powered, portable devices. This paper describes a Low Power CWT (LPCWT) implementation that is based around the mathematical approximation of a mother wavelet and uses application specific information to guide the approximation process. Simulations comparing the LPCWT and CWT are carried out with the two giving equivalent signal processing performance. The LPCWT is suitable for realisation in any desired circuit topology.

  • Conference paper
    Yates D, Lopez-Morillo E, Carvajal RG, Ramirez-Angulo J, Rodriguez-Villegas Eet al., 2007,

    A low-voltage low-power front-end for wearable EEG systems

    , 29th Annual International Conference of the IEEE-Engineering-in-Medicine-and-Biology-Society, Publisher: IEEE, Pages: 5282-5285, ISSN: 1557-170X

    A low-voltage and low-power front-end for miniaturized, wearable EEG systems is presented. The instrumentation amplifier, which removes the electrode drift and conditions the signal for a 10-bit A/D converter, combines a chopping strategy with quasi-FGMOS (QFG) transistors to minimize low frequency noise whilst enabling operation at 1 V supply. QFG devices are also key to the A/D converter operating at 1.2 V with 70dB of SNR and an oversampling ratio of 64. The whole system consumes less than 2uW at 1.2V.

  • Conference paper
    Yates DC, Casson AJ, Rodriguez-Villegas E, 2007,

    Low power technology for wearable cognition systems

    , BERLIN, 3rd International Conference on Foundation of Augmented Cognition, Publisher: SPRINGER-VERLAG, Pages: 127-136, ISSN: 0302-9743

    This paper analyses a key tradeoff behind miniature devices intended to monitor cognition-related parameters. These devices are supposed to be worn by people that would otherwise be carrying on a normal life and this factor imposes important constraints in the design. They have to be wireless, wearable, discrete, low maintenance and reliable. In order to reduce power intelligence will be built into the sensors aiming to reduce the data transmission to only that information that it is strictly necessary. This intelligence will be in the form of an algorithm which will be required to be implemented in electronic circuits as part of the system. The complexity of the algorithm affects the complexity of the electronics and hence the power consumption. This, in turn affects the size of the battery and the overall size of the device. For the sensor to be low maintenance the device must operate for extended periods from the battery, adding more constraints to the power consumption of the electronic circuits. The battery must be kept small so that the overall size of the device is small and lightweight enough to be worn on the body and the more discrete the device the higher consumer compliance. A tradeoff has to be met between the algorithm complexity, the power consumption of the electronics required to realize the latter, the power consumption required to transmit data and the battery size and lifetime.

  • Patent
    Rodriguez-Villegas E, Duncan JS, Corbishley P, Smith Set al., 2007,

    A method and apparatus for monitoring respiratory activity

    , WO/2007/099314
  • Conference paper
    López-Morillo E, Gonzalez-Carvajal R, Galan J, Ramirez-Angulo J, Lopez-Martin A, Rodriguez-Villegas Eet al., 2006,

    A Low-Voltage Low-Power QFG-based Sigma-Delta Modulator for Electroencephalogram Applications

  • Book
    Rodriguez-Villegas E, 2006,

    Low Power and Low Voltage Analogue Design with the Floating Gate MOS Transistor (FGMOS)

    , Publisher: The Institution of Engineering and Technology
  • Conference paper
    Rodriguez-Villegas E, Alam I, 2006,

    Ultra low power four-quadrant multiplier/two-quadrant divider circuit using FGMOS

    , IEEE Midwest Simposium on Circuits and Systems (Midwest 2006)
  • Conference paper
    Yates D C, Rodriguez-Villegas E, 2006,

    An Ultra Low Power Low Noise Chopper Amplifier for Wireless EEG

    , IEEE Midwest Symposium on Circuits and Systems
  • Conference paper
    Corbishley P G, Rodriguez-Villegas E, 2006,

    A Low Power Low Voltage Rectifier Circuit

    , IEEE Midwest Simposium on Circuits and Systems
  • Conference paper
    Corbishley P G, Rodriguez-Villegas E, 2006,

    Design Tradeoffs in low-power low-voltage transconductors in weak inversion

    , IEEE Midwest Simposium on Circuit and Systems
  • Conference paper
    López-Morillo E, Gonzalez-Carvajal R, ElGimili H, Ramirez-Angulo J, Lopez-Martin A, Rodriguez-Villegas Eet al., 2006,

    A Very Low-Power Class AB/AB Op-amp based Sigma-Delta Modulator for Biomedical Applications

    , IEEE Midwest Symposium on Circuits and Systems

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