Today at the International Solid-State Circuits Conference (ISSCC) IMEC, Europe’s largest independent nanoelectronics and nanotechnology R&D center, announced three major advances in technologies that will be used in wireless autonomous sensor nodes:  (1) a read-out front-end for portable biopotential acquisition systems; (2) a fully integrated low-power UWB receiver for low-data-rate applications; and, (3) a high-speed analog-to-digital converter (ADC) with a record low-power consumption of 0.16pJ/conversion step.  The ADC architecture has been implemented within the UWB receiver.

The three technology advances will benefit IMEC's Human++ program, which addresses medical, lifestyle and entertainment applications.

The read-out front-end allows the extraction of bio-potential signals produced by portable electroencephalography (EEG), electrocardiography (ECG) and electromyography (EMG) systems.  It is also suitable for autonomous applications. The front-end has an equivalent input referred noise of 60nV/ÖHz and a total power dissipation of 60µW.

EEG, ECG and EMG waves are µV-range signals that suffer from a large amount of common-mode (CM) interference. Furthermore, the bio-potential electrodes that are needed to view the signals generate a non-negligible offset. To achieve signal extraction, a front-end is needed with high CM rejection ratio (CMRR); low-noise, high-pass filter (HPF) characteristics; and configurability for bio-potentials originating from the heart, muscles or the brain.  Very low power consumption is necessary to enable long-term power autonomy. The aim is to increase the patient’s autonomy and quality of life, as well as extending the devices to sports, entertainment, comfort monitoring, and other health and lifestyle products and services.<br>
The bio-potential front-end, which was fabricated in a 0.5µm CMOS process through AMI Semiconductor, has a core area measuring less than 2mm².  It is capable of operating more than three years from two conventional AA batteries, making it ideal for autonomous applications.

Integrated low-power UWB receiver for low-data-rate sensor networks <br>
IMEC has also developed a fully integrated UWB impulse radio (IR) receiver in UMC's 0.18µm CMOS technology. The UWB receiver operates between 3GHz and 5GHz and can process pulses with 500MHz up to 2GHz bandwidth thanks to a variable channel select filter.

IMEC's receiver front-end is suitable for most IR approaches and very convenient for carrier-based IR (CB-IR) which enables sufficient flexibility in spectrum definition while keeping the system complexity as low as possible.  It comprises an LNA and a quadrature down-conversion mixer. The chip’s total current consumption is 16mA, measured on a 1.8V supply at 20MHz clock rate.  It demonstrates the potential of IR-UWB for low-data-rate sensor-network applications.

Innovative ADC breaks through power barriers in low-power wireless applications
IMEC's 90nm RF CMOS program has designed a 4-bit, 1.25Gsamples/s, 2.5mW high-bandwidth ADC prototype, which has achieved a world-record figure of merit of 0.16pJ/conversion step. The circuit has been processed in IMEC's 90nm RF CMOS prototype manufacturing technology which features an effective oxide thickness of 1.5nm and physical gate length of 70nm. The NMOS cutoff frequency ft is 170GHz. The maximum oscillation frequency fmax is 240GHz. The NMOS and PMOS threshold voltage matching coefficients are respectively 4.0 and 3.0 mV µm.

To reduce the power consumption, all the non-essential blocks (track-and-hold, preamplifiers, reference ladder and bubble error correction) of the flash architecture have been removed. First, 15 comparators sample the data and amplify it. The output comparator outputs are stored in 15 set-reset latches. The stored thermometer code is then converted into a 4-bit gray code by the ROM-based encoder which has intrinsic error correction properties.

The implemented comparator circuit combines the sampling, amplifying and reference levels functions with high accuracy and high sampling speed at low power. The reference levels are generated by an intentional imbalance that is introduced in the input differential pair. The threshold voltages are then calibrated with DC input signals and are sufficiently accurate to reduce the integral non-linearity to less than 0.15 LSB (last significant bit).

About IMEC's Human++ Program
IMEC’s Human++ research develops generic technologies that can be used in the fabrication of devices that improve the quality of life. Hence, Human++ complements the needs of a changing society that will utilize medicine, sports and entertainment in new ways.  Ultimately, the technology will lead to the development of a personal body-area network (BAN) that delivers services to the wearer.  These services include the management of chronic disease, medical diagnostic, home-monitoring, biometrics, and sports and fitness tracking.

The technologies being developed within the Human++ program are generic and can be tuned to other wireless autonomous system applications.

Human++ is structured around 5 main technology programs: ultra-low-power signal processing, ultra-low-power radio, micropower systems, sensors and actuators and integration and implementation.

A number of research areas within these programs (i.e., ultra-wide-band technology, low-power digital signal processing, micropower scavenging, power management, sensors and actuators) will be transferred to the Holst Centre.  The Holst research center was initiated by IMEC and TNO in September 2005 to develop generic technologies for future generations of wireless autonomous transducer solutions and systems-in-foil.
---end---

For more information:

Katrien Marent
Corporate Communication Manager
IMEC, Kapeldreef 75
B- 3001 Leuven, Belgium
Tel +32 16 28 18 80 Fax +32 16 28 16 37
Email: Katrien.Marent@imec.be