The target for the research is to reach the goal of a thumb-size autonomous ultrasound measurement system with wireless communication capabilities. The work combines and increases the knowledge available in the various fields within EISLAB. The vision is that a complete measurement system that comprises the excitation of the piezoelectric device, analog and signal conditioning, communication capability, as well as battery power
supply shall be integrated in a thumb-size unit.

The stringent size and power consumption demands of the system leads to a high integration level of the electronics, with the target to integrate all electronics affiliated with the system in one single chip. Challenges involve high voltage excitation, low noise amplification, A/D conversion, and on-chip signal conditioning. An effective tool to help in the design proces and system level optimization is to use SPICE models of the ultrasound system directly in the design environment for the chip-level electronics.

The EISCAT (European Incoherent SCATter) Scientific Association is an international research organisation operating three incoherent scatter radar systems in Northern Scandinavia. EISCAT studies the interaction between the Sun and the Earth as revealed by disturbances in the magnetosphere and the ionised parts of the atmosphere (these interactions also give rise to the spectacular aurora, or Northern Lights).

EISCAT 3D is a research project with several partners aiming to design large distrubuted phased array antennas for the EISCAT system. The research performed by the mixed mode design group at EISLAB will investigate, design, and test the microelectronics that will interface to each element in the distributed phase array antennas. The project involves both on-chip and discrete electronics. Key issues are time synchronization between array elements, low noise RF front-end design and calibration, and high speed A/D converter design.

The level-crossing A/D converter is based on level-crossing sampling as opposed to the conventional time sampled A/D converters. The signal is sampled when it crosses a quantization level, when for each
sample the sampling time and level crossed are stored. Thus, the time intervals between sampling instants are unevently distributed, but the amplitude error in the sampling instant is minimized.

Critical components in the system design are the comparator that detects the level crossing, as well as the time measuring unit. The research has focused on the design of low power time-continous comparators with stable propagation time.

The Mulle is a small EIS (Embedded Internet Systems) platform based on a Renesas M16C/62 microprocessor. The first version uses a bare die micropocessor chip which is mounted and bonded to the six-layer circuit board, the second version uses a standard package. The bare die processor chip is covered with a glob top (the black goo in the picture). All other components are surface mounted. On the same circuit board, mounted on the rear (front shown in picture), is a Bluetooth module.

The platform is battery powered and designed for low-power consumption. The size of the Mulle platform is only 25 x 23 x 5 mm. The Mulle platform is a complete standalone sensor node aimed at ad-hoc sensor networking and ambient intelligence systems.

The Mulle generation 1 has analog and digital interfaces while generation 2 has on-board sensors. Generation 3 uses a high-density 60-pin expansion connecter where daughter boards can be attahed for a large variety of sensors. All Mulles has signal processing capabilities, an integrated webserver as well as integrated wireless communication using Bluetooth.

The Mulle uses standardized protocols such as Bluetooth profiles (LAP, SPP and PAN) and TCP/IP to communicate. This approach enables users all over the world to access sensor data from a Mulle in real time.