LONDON Belgian independent research organization IMEC has outlined the initial fruits of its Human++ program which focuses on wearable, wireless body area networks.
One of the advances, highlighted at the International Solid State Circuits Conference (ISSCC), which is being held Feb. 5 to Feb. 9 in San Francisco, California, outlines a fully integrated low-power ultrawideband (UWB) receiver for low-data-rate applications, while another paper discusses the development of 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 UWB impulse radio (IR) receiver, made in UMC’s 0.18 micron CMOS technology, operates at between 3GHz and 5GHz and can process pulses with 500MHz up to 2GHz bandwidth thanks to a variable channel select filter.
The researchers say the receiver front-end is particularly suitable 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.
IMEC says the device demonstrates the potential of IR-UWB for low-data-rate sensor-network applications.
The ADC development was done as part of the research group’s 90nm RF CMOS project and IMEC says it breaks through power barriers in low-power wireless applications.
The 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. It was processed with the group’s 90nm RF CMOS prototype technology that features an effective oxide thickness of 1.5nm and physical gate length of 70nm.
To reduce the power consumption, the researchers removed all the non-essential blocks (track-and-hold, preamplifiers, reference ladder and bubble error correction) of the flash architecture. 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 that has intrinsic error correction properties.
Another group described at the Conference a read-out front-end that allows the extraction of bio-potential signals produced by portable electroencephalography (EEG), electrocardiography (ECG) and electromyography (EMG) systems. The researchers say the device is also suitable for autonomous applications.
The bio-potential front-end, which was fabricated in a 0.5 micron CMOS process through AMI Semiconductor, has a core area measuring less than 2mm squared. It is capable of operating for more than three years from two conventional AA batteries.
A number of research areas within the Human++ programs (for instance UWB, low-power digital signal processing, micropower scavenging, power management, sensors and actuators) will be transferred to the Holst Center. This was initiated by IMEC and TNO in September 2005 to develop generic technologies for wireless autonomous transducer solutions.