Publications
164 results found
Rodriguez-Villegas E, Corbishley P, Lujan-Martinez C, et 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
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- Citations: 11
Rodriguez-Villegas E, Xu M, 2009, Simplifying the Design of ΣΔ Modulators Using FGMOS Transistors, IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS I-REGULAR PAPERS, Vol: 56, Pages: 1313-1325, ISSN: 1549-8328
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- Citations: 3
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
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- Citations: 1
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.
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
Rodriguez-Villegas E, Aguilar-Pelaez E, Chen G, et al., 2009, APNEA DETECTOR TO PREVENT SUDEP, Publisher: WILEY-BLACKWELL PUBLISHING, INC
Casson AJ, Rodriguez-Villegas E, 2008, Generic vs custom; analogue vs digital: on the implementation of an online EEG signal processing algorithm., Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference, Pages: 5876-5880, ISSN: 1557-170X
This paper quantifies the performance difference between custom and generic hardware algorithm implementations, illustrating the challenges that are involved in Body Area Network signal processing implementations. The potential use of analogue signal processing to improve the power performance is also demonstrated.
Casson AJ, Rodriguez-Villegas E, 2008, On data reduction in EEG monitoring: comparison between ambulatory and non-ambulatory recordings., Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference, Pages: 5885-5888, ISSN: 1557-170X
To compare the performance of an EEG data selection/reduction algorithm for epileptic EEGs on ambulatory and non-ambulatory recorded data to confirm that acceptable performance is achievable in ambulatory recordings despite the presence of overt artifacts. A total of 167 hours of EEG data containing 899 marked interictal events is analysed to determine the percentage of events correctly recorded (the sensitivity) and the amount of data reduction achieved. A better sensitivity-data reduction trade-off is found in the ambulatory recorded data. This may be unexpected as ambulatory recordings are known to contain large numbers of artifacts, but is accounted for by these artifacts being easily detected and discarded, improving the data reduction. Satisfactory performance levels are found in both data types, no degradation is present with ambulatory recordings. Significance: Demonstrates that the processing of EEG data for wearable EEG applications is feasible without a loss in performance compared to traditional inpatient EEG usage.
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.
Lopez-Morillo E, Carvajal RG, Munoz F, et 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
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- Citations: 20
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
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- Citations: 142
Rodriguez-Villegas E, Yates D, 2008, Apparatus and method for obtaining EEG data, WO/2008/015449
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
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- Citations: 5
Aguilar-Pelaez E, Rodríguez-Villegas E, 2008, Low-power differential photoplethysmographic pulse transit time detector for ambulatory cardiovascular monitoring, Pages: 1104-1107
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
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- Citations: 5
Casson AJ, Smith S, Duncan JS, et 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
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- Citations: 45
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
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- Citations: 4
Casson AJ, Yates DC, Patel S, et al., 2007, Algorithm for AEEG data selection leading to wireless and long term epilepsy monitoring., Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference, Pages: 2456-2459, ISSN: 1557-170X
High quality, wireless ambulatory EEG (AEEG) systems that can operate over extended periods of time are not currently feasible due to the high power consumption of wireless transmitters. Previous work has thus proposed data reduction by only transmitting sections of data that contain candidate epileptic activity. This paper investigates algorithms by which this data selection can be carried out. It is essential that the algorithm is low power and that all possible features are identified, even at the expense of more false detections. Given this, a brief review of spike detection algorithms is carried out with a view to using these algorithms to drive the data reduction process. A CWT based algorithm is deemed most suitable for use and an algorithm is described in detail and its performance tested. It is found that over 90% of expert marked spikes are identified whilst giving a 40% reduction in the amount of data to be transmitted and analysed. The performance varies with the recording duration in response to each detection and this effect is also investigated. The proposed algorithm will form the basis of new a AEEG system that allows wireless and longer term epilepsy monitoring.
Casson AJ, Yates DC, Patel S, et al., 2007, An analogue bandpass filter realisation of the Continuous Wavelet Transform., Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference, 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.
Yates D, López-Morillo E, Carvajal RG, et al., 2007, A low-voltage low-power front-end for wearable EEG systems., Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference, 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.
Casson AJ, Yates DC, Patel S, et 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
Rodriguez-Villegas E, 2007, A low-power wide range transimpedance amplifier for biochemical sensing., Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference, Pages: 2673-2676, ISSN: 1557-170X
This paper presents a novel low voltage and low power transimpedance amplifier for amperometric potentiostats. The power is optimized by having three different gain settings for different current ranges, which can be programmed with a biasing current. The voltage ranges have been optimized by using FGMOS transistors in a second voltage amplification stage that simultaneously allow for offset calibration as well as independent biasing of the gates. The circuit operates with input currents from 1 pA to 1 microA, with a maximum power supply voltage of 1.5 V and consumes 82.5 nW, 9.825 microW, 47.325 microW for currents varying from (1 pA, 0.25 nA), (0.25 nA, 62.5 nA) and (62.5 nA, 1 microA) respectively.
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
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- Citations: 72
Yates D C, Casson A, Rodriguez-Villegas E, 2007, Low Power Technology for Wearable Cognition Systems
Casson A, Rodriguez-Villegas E, 2007, Data reduction techniques to facilitate wireless and long term AEEG epilepsy monitoring
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
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- Citations: 20
Yates D, Lopez-Morillo E, Carvajal RG, et 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.
Rodriguez-Villegas E, Duncan JS, Corbishley P, et al., 2007, A method and apparatus for monitoring respiratory activity, WO/2007/099314
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-+
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- Citations: 21
Casson AJ, Yates DC, Patel S, et 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.
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