Analyses have shown that many local communication applications require simple, low-cost equipment with very low power consumption.The majority of current communications systems is designed for the transmission of data in a micro-computing context and do not entirely meet these criteria. Consequently, the research aims to produce communication devices based on innovative new structures, such as Ultra Wide Band (UWB) systems. The team’s activities within Telecom Sud Paris mainly concern CMOS integration of the RF part of Impulse Radio Systems.

Impulse Radio system

Recently the techniques based on Impulse Radio (IR) Ultra Wideband (UWB) have experienced a growing interest in the field of wireless systems. An efficient technique known as Transmitted Reference (TR) UWB, has gained in popularity for low and medium data rates applications such as sensor networks. This technique uses two pulses per symbol period, which are strongly correlated and separated by a well known delay (D). The reception system is composed of a wideband analog delay element and a correlator. The delay line allows making a copy of the received signal with a delay that corresponds exactly to D; the correlation is then made with these two pulses. Despite the apparent simplicity of this type of receiver, its implementation in a low power integrated circuit is not an easy task, especially the delay element which must be wideband for UWB applications.

To overcome this difficulty, a new detection method called Time Delayed Sampling and Correlation (TDSC) has been proposed recently, and developed at EPH department.  It uses two analog waveform samplers activated at different times; here the delay D between pulses is applied to the control signals of the two samplers. The delay is generated in a digital way; it becomes programmable and can be used in a multi-user context (a different delay for each user for example).

The design and implementation of a CMOS prototype for a TDSC-UWB receiver based on TR-UWB detection scheme was realized. The prototype made in CMOS 0.35mm technology, allows the validation of the new detection concept, i.e. TDSC. Thanks to this prototype, it was possible to measure a -3 dB bandwidth of around 1.1 GHz and a sampling frequency of more than 7 GHz. This allows the detection of impulse signals with an input bandwidth of 500 MHz (»2 ns), which is the minimum bandwidth for the UWB technology.

The main results can be seen on the figure 1 below:

Today the work goes on, with the implementation of the synchronisation programm in order to obtain a more or less real time communication system for 802.15.4a like.

A new phd student studies the localisation potentiallity offers by this method and different other problems like WBAN or MIMO communication.