Partner und Internationale Organisationen
(Englisch)
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EPFL, DE-LEG, ELB Ecublens, Lausanne (CH),
Logitech SA, z.i. Moulin du Choc, Romanel-sur-Morges (CH), Mead Microelectronics SA, Saint-Sulpice, CH, Transval SA, Valentigney cedex (F)
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Abstract
(Englisch)
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The first objective of the SUPREGE project is to develop a new solution for micropower wireless data transmission over short distances. The frequency bands are the UHF ISM (Industrial Scientific and Medical) frequency bands (centered frequency equal to 434 MHz and 868 MHz, in Europe, and 916 MHz in the USA). As the ISM frequency bands are widely used, a half-duplex link between the receiver and the transmitter is often necessary. Typical applications are high volume low-cost and low-power data transmission systems such as : interconnections of computer peripherals, wireless distributed sensors, domotics, and biomedical circuits. The second objective of the SUPREGE project is to develop industrial demonstrators which share the common constraint of requiring micropower wireless data transmission over short distances. These three applications are respectively : (1) a remote control for vehicle alarms (Transval), (2) wireless computer peripherals (Logitech), and (3) a wireless data transmission system for water counters (Mead Microelectronics).
Most of those devices are supplied by two batteries in series which deliver a supply voltage between 2 V and 3.2 V. In practice, the target current consumption of the receiver is lower than 2 mA to extend the battery life. The 100 % amplitude modulation, also called OOK (On Off Keying) modulation, is used. Typical data-rates are comprised between 1 kbit/s and 50 kbit/s. The typical transmission range is equal to 20 meters in open area.
The micropower receiver makes use of an original architecture based on the super-regeneration principle which was invented by Armstrong in 1922. It is based on the variation of the start-up time of an oscillator as a function of the input RF signal coupled from the antenna. This technique was widely used in vacuum tubes circuits up to the fifties. Then, it was progressively abandoned when the superheterodyne receiver appeared due to its better selectivity compared to the super-regenerative discrete-components solution.
Nowadays, for short distance data transmission systems, the principle of super-regeneration allows a very simple architecture and appears to be particularly suited to micropower applications, compared to classical solutions such as the superheterodyne, the low IF (Intermediate Frequency) or the direct conversion receiver. Compared to a discrete-components super-regenerative solution, original analog integrated circuits techniques have been used to improve selectivity and sensitivity of the integrated super-regenerative receiver.
The external components of the super-regenerative integrated receiver are limited to a resonator and to some decoupling capacitors. In contrast, for classical solutions, it is often necessary to use external IF filters, like ceramic or SAW (Surface Acoustic Waves) filters, which are expensive components. The simple architecture of the super-regenerative receiver implies that its silicon area is much smaller than classical receivers such as the super-heterodyne receiver. Its very small area and its limited number of external components implies that its cost is low compared to classical receivers.
The core of the super-regenerative receiver being an oscillator, the oscillator of the receiver can be used to make the transmitter when adding a modulator. This is another important advantage compared to classical solutions. This super-regenerative receiver-transmitter has been developed by the Electronics Laboratory (LEG) of the Swiss Federal Institute of Technology, Lausanne (EPFL).
The following approach has been followed by the LEG. First, the choice of the oscillator and the application of the quench signal and of the RF input signal to the oscillator have been addressed. It has been decided to use the BiCMOS technology because it allows to combine the advantages of the bipolar and MOS transistors in order to reduce the power consumption.
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