Mehmet R. Yuce

A 128-Channel 6 mW Wireless Neural Recording IC With Spike Feature Extraction and UWB Transmitter

This paper reports a 128-channel neural recording integrated circuit (IC) with on-the-fly spike feature extraction and wireless telemetry. The chip consists of eight 16-channel front-end recording blocks, spike detection and feature extraction digital signal processor (DSP), ultra wideband (UWB) transmitter, and on-chip bias generators. Each recording channel has amplifiers with programmable gain and bandwidth to accommodate different types of biological signals. An analog-to-digital converter (ADC) shared by 16 amplifiers through time-multiplexing results in a balanced trade-off between the power consumption and chip area. A nonlinear energy operator (NEO) based spike detector is implemented for identifying spikes, which are further processed by a digital frequency-shaping filter. The computationally efficient spike detection and feature extraction algorithms attribute to an auspicious DSP implementation on-chip. UWB telemetry is designed to wirelessly transfer raw data from 128 recording channels at a data rate of 90 Mbit/s. The chip is realized in 0.35 mum complementary metal-oxide-semiconductor (CMOS) process with an area of 8.8 times 7.2 mm2 and consumes 6 mW by employing a sequential turn-on architecture that selectively powers off idle analog circuit blocks. The chip has been tested for electrical specifications and verified in an ex vivo biological environment.

A 128-Channel 6mW Wireless Neural Recording IC with On-the-Fly Spike Sorting and UWB Tansmitter

The chip is composed of eight 16-channel front-end blocks, data serializing circuits, a DSP for on-chip spike sorting, digital MUX, encoder, UWB TX, and bias generators. The chip operates in one of the two modes. In sorting mode, a selected channel is connected to the on-the-fly spike sorting block and the extracted features of the spikes are transmitted for off-chip classification. In streaming mode, all the sampled data from the 128 channels are recorded and transmitted without any additional processing.

Easy-to-Swallow Wireless Telemetry

Many countries will experience the effects of an aging population, resulting in a high demand of healthcare facilities. Development of novel biomedical technologies is an urgent necessity to improve diagnostic services for this demographic. Electrocar diogram (ECG) and temperature recording have been used for more than 50 years in medical diagnosis to understand various biological activities [1], [2]. A more recent development, electronic pill technology, requires the integration of more complex systems on the same platform when compared to conventional implantable systems. A small miniaturized electronic pill can reach areas such as the small intestine and can deliver real time video images wirelessly to an external console. Figure 1 shows an electronic pill system (i.e., wireless endoscopy) for a medical monitoring system. The device travels through the digestive system to collect image data and transfers the data to a nearby computer for display with a distance of one meter or more. A high resolution videobased capsule endoscope produces a large amount of data, which can then be delivered over a high-capacity wireless link.

Performance evaluation of a Wireless Body Area sensor network for remote patient monitoring

In recent years, interests in the application of Wireless Body Area Network (WBAN) have grown considerably. A WBAN can be used to develop a patient monitoring system which offers flexibility and mobility to patients. Use of a WBAN will also allow the flexibility of setting up a remote monitoring system via either the internet or an intranet. For such medical systems it is very important that a WBAN can collect and transmit data reliably, and in a timely manner to the monitoring entity. In this paper we examine the performance of an IEEE802.15.4/Zigbee MAC based WBAN operating in different patient monitoring environment. We study the performance of a remote patient monitoring system using an OPNET based simulation model.

Dielectric Loaded Impedance Matching for Wideband Implanted Antennas

In implanted biomedical devices, due to the presence of surrounding dissipative biological tissue, the antenna suffers poor impedance matching. This causes degradation in the performance of a wideband or ultra-wideband (UWB) implanted device. Moreover, the electrical properties of tissue change from organ to organ, and possibly from time to time. In this paper, it is shown that loading of antennas with suitable insulators can deliver broadband matching across a range of dissipative medium properties. An impedance-matched UWB antenna designed to operate inside a lossy medium, which has varying electromagnetic properties within the range expected in biological tissues, is presented. The operating bandwidth of the proposed design is 3.5-4.5 GHz, which is an interference-free subset of the unlicensed UWB band in the US. It is demonstrated that once the dielectric loading is applied, the conventional procedure for antenna design in free space can be followed. The proposed implantable small capsule-shaped slot antenna has been characterized using numerical simulations. Details of a proof-of-concept experiment are presented.

Wideband Communication for Implantable and Wearable Systems

This paper presents the feasibility of applying an ultra-wideband (UWB) wireless scheme to both high data rate implantable neural recording and low data rate wearable biomedical applications. An extensive analysis on the UWB signal generation for biomedical application is discussed. A CMOS UWB transmitter has been designed, fabricated, and used in a high data rate neural recording system. A method to readily assemble a flexible UWB transmitter for wearable physiological monitoring system is also presented. An eight-channel low data rate recording system for monitoring multiple continuous electrocardiogram and electroencephalogram signals has been designed, and its test results are presented.

Wireless Body Area Network (WBAN) Design Techniques and Performance Evaluation

In recent years interest in the application of Wireless Body Area Network (WBAN) for patient monitoring applications has grown significantly. A WBAN can be used to develop patient monitoring systems which offer flexibility to medical staff and mobility to patients. Patients monitoring could involve a range of activities including data collection from various body sensors for storage and diagnosis, transmitting data to remote medical databases, and controlling medical appliances, etc. Also, WBANs could operate in an interconnected mode to enable remote patient monitoring using telehealth/e-health applications. A WBAN can also be used to monitor athletes’ performance and assist them in training activities. For such applications it is very important that a WBAN collects and transmits data reliably, and in a timely manner to a monitoring entity. In order to address these issues, this paper presents WBAN design techniques for medical applications. We examine the WBAN design issues with particular emphasis on the design of MAC protocols and power consumption profiles of WBAN. Some simulation results are presented to further illustrate the performances of various WBAN design techniques.

Wireless Body Sensor Network Using Medical Implant Band

A wireless body sensor network hardware has been designed and implemented based on MICS (Medical Implant Communication Service) band. The MICS band offers the advantage of miniaturized electronic devices that can either be used as an implanted node or as an external node. In this work, the prototype system uses temperature and pulse rate sensors on nodes. The sensor node can transmit data over the air to a remote central control unit (CCU) for further processing, monitoring and storage. The developed system offers medical staff to obtain patient’s physiological data on demand basis via the Internet. Some preliminary performance data is presented in the paper.

A Non-Coherent DPSK Data Receiver With Interference Cancellation for Dual-Band Transcutaneous Telemetries

A dual-band telemetry, which has different carrier frequencies for power and data signals, is used to maximize both power transfer efficiency and data rate for transcutaneous implants. However, in such a system, the power signal interferes with the data transmission due to the multiple magnetic couplings paths within the inductive coils. Since the power level of the transmitted power signal is significantly larger than that of the data signal, it usually requires a high-order filter to suppress the interference. This paper presents a non-coherent DPSK receiver without a high-order filter that is robust to the interference caused by the power carrier signal. The proposed scheme uses differential demodulation in the analog domain to cancel the interference signal for a dual-band configuration. The data demodulation also uses subsampling to avoid carrier synchronization circuits such as PLLs. The experimental results show that the demodulator can recover 1 and 2 Mb/s data rates at a 20 MHz carrier frequency, and it is able to cancel an interference signal that is 12 dB larger than the data signal without using complex filters. The demodulator is fabricated in a 0.35 mum CMOS process, with a power consumption of 6.2 mW and an active die area of 2.6times1.7mm2.

A 2-DOF MEMS Ultrasonic Energy Harvester

This paper reports a novel ultrasonic-based wireless power transmission technique that has the potential to drive implantable biosensors. Compared with commonly used radio-frequency (RF) radiation methods, the ultrasonic power transmission is relatively safe for the human body and does not cause electronic interference with other electronic circuits. To extract ambient kinetic energy with arbitrary in-plane motion directions, a novel 2-D MEMS power harvester has been designed with resonance frequencies of 38520 and 38725 Hz. Frequency-response characterization results verify that the device can extract energy from the directions of X, Y, and diagonals. Working in the diagonal direction, the device has a bandwidth of 302 Hz, which is twice wider than a comparable 1-D resonator device. A 1- storage capacitor is charged up from 0.51 to 0.95 V in 15 s, when the harvester is driven by an ultrasonic transducer at a distance of 0.5 cm in the X-direction, and is biased by 60 Vdc, indicating the energy harvesting capability of 21.4 nW in the X-direction. When excited along the Y-axis, the harvester has an energy-harvesting capacity of 22.7 nW. The harvester was modeled and simulated using an equivalent electrical circuit model in Saber, and the simulation results showed good agreement with the experimental results. The ultrasonic energy harvesting was also investigated using a 1-D piezoelectric micro-cantilever.