sábado, 20 de marzo de 2010

MIMOSA (MIcrosystem platform for MObile Services and Applications)

1. Background

MIMOSA is an integrated project in the EC 6th framework programme (IST-2002-507045). The project advocates a mobile-phone centric realization of ambient intelligence. The consortium includes major industrial partners and leading European research institutes. The Finnish partners of MIMOSA are VTT, Nokia, Suunto, and MAS. The duration of the project is 1. 1. 2004 – 30. 6. 2006.

2. Objectives

In the MIMOSA vision, the personal mobile phone is chosen as the trusted intelligent user interface to Ambient Intelligence and a gateway between the sensors, the network of sensors, the public network and the Internet. MIMOSA develops an open technology platform for implementing ambient intelligence in different application areas. The well-defined platform allows a fast and focused development of both basic technology solutions as well as system-level applications and services. MIMOSA focuses to develop micro- and nanosystems in several areas of the MIMOSA open platform.

In the environment domain, i.e., in an intelligent environment of a mobile user, MIMOSA contributes by developing wireless remote-powered sensors which exploit RFID technology, and novel low-power radios which exploit RF-MEMS technology.

In the user domain, MIMOSA contributes by developing microsystem-based intuitive user interfaces which make efficient use of short-range communication and various sensors embedded both in the mobile handset and the local environment. MEMS based user-activity and physiological sensors will be used as user interfaces to realize new applications.

In the phone domain, MIMOSA develops a readers/writers for RFID tags and sensors which is closely integrated with the Bluetooth radio by sharing same RF circuit blocks. In addition, MEMS-based inertial, magnetic and audio sensors are realized and embedded in the handset, to enable novel intuitive user interfaces.

3. Work breakdown and methodology

The organization of the MIMOSA project is optimized to support the creation of an open technology and application platform which is well adapted to generating useful services for future intelligent environments. The MIMOSA work packages are represented in Fig. 1. Three work packages are led by Finnish partners, WP1 and WP3A by VTT, and WP2 by Nokia.

Fig. 1. MIMOSA work packages.

Human-centred design in the context of the design of a universal platform and related technologies is quite extraordinary; usually human users are thought about only when individual applications are being designed onto the platform. However, many forthcoming features of applications are actually fixed by the solutions done on the platform level, and that is why VTT in MIMOSA project aims to apply human-centred design principles in designing technical infrastructures for Ambient Intelligence solutions.

In the development of MIMOSA technological building blocks, extensive use is made of advanced IC technology and various MEMS technologies.
  • Silicon MEMS technology for inertial and magnetic sensors, and for low-power, MEMS-based reference oscillators.
  • Thin film AlN technology for SMR-BAW filters and oscillators for low-power radios.
  • Polymer technology for physiological sensors and some novel applications.
  • Advanced 130 nm SOI-IC technology for low-power RFID tags and sensors.

The development of technological building blocks makes use of usual tools that are used for developing microsystems and integrated circuit. These include various circuit simulators both in the device and system level, electromagnetic simulators for antenna design, FEM simulators for MEMS design, process simulators for IC and MEMS fabrication.  

4. Results

4.1 User and application requirements for Ambient Intelligence solutions

The aim of MIMOSA work package 1 (WP1) is to ensure that the development of the MIMOSA core technology is based on the needs of the users, and that the resulting technologies will be easy-to-use, useful and acceptable from the end user's point of view, as well as applicable from the application developers point of view. VTT has coordinated and carried out most of the work in WP1.

In the beginning of the project, WP1 coordinated the definition of a common vision for the project, and illustration of the vision as usage scenarios. During the first project year, the scenarios were analysed and evaluated for credibility, acceptability and technical feasibility by potential end-users, field experts, and technology and application developers in the project.

During the second year, key parts of the usage scenarios have been implemented as proof of concept technology demonstrators that illustrate the look and feel of applications that MIMOSA technology will facilitate in the selected application areas (sports, fitness, health care, housing, everyday). These proof of concepts have been evaluated with users and application field experts. The evaluation results and the potential of MIMOSA technologies have been assessed with the technology and application developer partners in the project.

The main results are written deliverables which describe MIMOSA scenarios in selected application fields and the respective user and application requirements.

It has turned out that human-centred design can be applied also when designing technical infrastructures but novel methods are needed. Scenarios and proof of concepts based on existing technologies illustrate to potential users and application field experts as well as to the project group itself what the project is targeting to. User evaluations help in refining the scenarios. The hardest part of the work is identifying the implication of the scenarios and user feedback to the technical infrastructures. Our approach was based on identifying common patterns, and analyzing in details the interactions with users, terminals, tags and sensors within those patterns. Potential implications were discussed through with technology experts to clarify the technical feasibility of different solutions. Further work is needed to study how user feedback could be got more effectively and precisely, and earlier in the project.   

4.2 RFID-based solutions for short range communication: tags and sensors

The basic solution for the MIMOSA local connectivity is to make use of the 2.4 GHz ISM band. The goal is to develop a reconfigurable RF front end which can be used as the RF front end for the existing Bluetooth radio or, alternatively, as the RF front end of an RFID interrogator.

The central features of two RFID communication protocols were chosen for implementation, namely the ISO 18000-4 standard and a modification of the Palomar protocol for the 2.4 GHz band.

The primary goal was to develop passive tags and sensors, i.e., tags that are powered remotely by the interrogator. The efficiency of the wireless power transfer and the power consumption of the tag circuit become then major design issues. The effective apertures of the tag and the reader antennas are restricted by their small geometric sizes. The efficiency of the RF rectification of the tag circuit is important. Two different rectifiers were designed and fabricated. One was based on CMOS-transistors on 130 nm SOI IC technology of STMicroelectronics. The other approach made use of Schottky diodes on thick SOI wafers.

The analog circuit blocks such as a demodulator, regulator, limiter, modulator, and power-on-reset circuit were also designed on the 130 nm SOI IC technology of STMicroelectronics. The digital blocks of the RFID protocol management were implemented by using a FPGA circuit. These features will later be included in the integrated circuit.

A low-power interface circuit with A/D conversion was designed for capacitive sensors. The RFID protocol was defined to include sensor data inquiries.

The first wireless remotely-powered sensors of the MIMOSA are now being integrated and tested. Figure 2 illustrates an RFID tag on a foil-type antenna. Figure 3 shows the calculated radiation pattern.

Fig. 2. Foil-type antenna for WRPS.

Fig. 3. Radiation pattern of the antenna of Fig. 2.

4.3 RFID-based solutions for short range communication: reader

Figure 4 represents the architecture of the RFID reader RF parts which are designed to be finally integrated in a mobile phone. The major difference between a radio and an RFID reader is that the RFID reader simultaneously sends and receives signal at the same frequency.  A good isolation between the transmit and receive paths is essential, otherwise the LNA gets easily saturated, especially when the same antenna is being used for both signals. Additional problems are caused by environmental reflections of the transmitted microwave signal. These reflections can amount to some -20 dB signal at the LNA with respect to the transmitted power. Environmental reflections change in time while the antenna and the nearby reflecting objects move with respect to each other. Thus the isolation should adapt to the changing environment. Figure 4 illustrates one solution to this problem. A separate compensation channel is used to superpose an appropriate signal at the LNA input to keep the LNA within its dynamic range. The amplitude and the phase of the compensation signal is controlled by a baseband logic. The circuit has now been integrated with a mobile phone platform. Tests have confirmed the basic functionality in the RFID reader and Bluetooth modes. Further tests are being made on the radio channel stability. This demonstrator will be used to communicate with the RFID sensors developed in MIMOSA.

Fig. 4. Block diagram of the combined 2.4 GHz RFID reader and a Bluetooth radio.

4.3 MEMS-based RF circuit blocks

MEMS-technology offers new solutions for several components in RF-electronics. The general advantages of RF-MEMS include low-power operation, miniaturization, small parasitics, tunability and/or reconfigurability, potential for highly integrated modules and subsystems. MIMOSA develops several RF-MEMS components

  • MEMS-based reference oscillators
  • Thin-film AlN components for SMR-BAW filters and oscillators
  • AlN-piezoactuated RF-MEMS switches
  • Packaging and interconnection techonologies for RF-MEMS components

MAS and VTT are developing monolithically integrated MEMS-based reference oscillators. Figure 5 shows an image of the device. The operation of the device is based on a square-shaped silicon structure which is suspended above the substrate by spring structures at the corners of the square. In addition, the middle point of the square is fixed to the substrate. Other parts of the square are released from the substrate by using a special etching technique developed by VTT, i.e., the so-called plug-up method. This etching technique makes it possible to release patterned MEMS structures from the substrate and yet preserve a wafer surface that can undergo the normal processing steps that are needed for fabrication of CMOS circuits.

The device that is being developed by MAS and VTT is a monolithically integrated 13 MHz reference oscillator. The functional blocks of the device include the MEMS resonator, the loop amplifier, a charge pump for the high bias voltage of the MEMS resonator, phase-locked-loop for a 2.4 GHz voltage-controlled oscillator, and a temperature sensor and associated control electronics for thermal compensation.

The first set of devices has been fabricated at VTT. Tests show that integration of loop amplifiers with MEMS resonators was successful. The next manufacturing run will narrow the gap between the sense and drive electrodes of the square plate. This should increase the electromechanical coupling to the level needed for a closed-loop oscillation. The devices have so far been tested under a pumped low-pressure environment. Wafer-level low-pressure packaging is eventually needed.

Fig. 5. Optical profilometer image of a 13 MHz oscillator circuit based on a MEMS resonator.

Commercial Impact

Industrial partners will exploit the results of MIMOSA within their own applications fields. These include Nokia (telecommunication), STMicroelectronics (IC circuits and microsystems), Legrand (home automation), Suunto (sports and fitness), ÅMIC (fabrication of polymer-based microsystems), Cardiplus (tele medicine), MAS (IC circuits), and Sonion (MEMS-based microphones). Exploitation of the MIMOSA results is described in a dedicated report (Plan of Use and Dissemination of Knowledge).

Emmanuel Rodriguez
Fuente: www.mimosa-fp6.com

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