Clock-Offset Tracking Software Algorithms For IR-UWB Energy-Detection Receivers

We present a clock-offset tracking algorithm for impulse-radio ultra-wide band (IR-UWB) energy-detection receivers. There is a complexity versus performance trade-off for the design of IR-UWB energy-detection receivers: Extremely low-complexity energy-detection receivers are built with a large, constant integration duration; they are robust to clock drifts but are sensitive to noise enhancement effects and cannot adapt to channel variations. More sophisticated energy-detection receivers use a shorter integration duration and combine several weighted outputs of the energy collector; they are robust to noise enhancement effects, can adapt to channel variations and offer a much better performance than non-adaptive receivers. However, they become sensitive to clock offsets. Hence, there is a need for low-complexity clock-offset tracking solutions to support adaptive energy-detection receivers. Our solution is constructed around the Radon transform, an image processing tool traditionally used to detect line features in images. Our solution is fully compatible with the IEEE 802.15.4a standard, does not increase the hardware complexity of the receiver and reduces the performance loss due to clock offset to less than 0.5 dB

Optimisation des performances de réseaux de capteurs dynamiques par le contrôle de synchronisation dans les systèmes ultra large bande

The basic concept of Impulse-Radio UWB (IR-UWB) technology is to transmit and receive baseband impulse waveform streams of very low power density and ultra-short duration pulses (typically at nanosecond scale). These properties of UWB give rise to fine time-domain resolution, rich multipath diversity, low power and low cost on-chip implementation facility, high secure and safety, enhanced penetration capability, high user capacity, and potential spectrum compatibility with existing narrowband systems. Due to all these features, UWB technology has been considered as a feasible technology for WSN applications. While UWB has many reasons to make it a useful and exciting technology for wireless sensor networks and many other applications, it also has some challenges which must be overcome for it to become a popular approach, such as interference from other UWB users, accurate modelling of the UWB channel in various environments, wideband RF component (antennas, low noise amplifiers) designs, accurate synchronization, high sampling rate for digital implementations, and so on. In this thesis, we will focus only on one of the most critical issues in ultra wideband systems: Timing Synchronization.Dans cette thèse nous nous sommes principalement concentrés sur les transmissions impulsion radio Ultra Large Bande (UWB-IR) qui a plusieurs avantages grâce à la nature de sa bande très large (entre 3.1GHZ et 10.6GHz) qui permet un débit élevé et une très bonne résolution temporelle. Ainsi, la très courte durée des impulsions émises assure une transmission robuste dans un canal multi-trajets dense. Enfin la faible densité spectrale de puissance du signal permet au système UWB de coexister avec les applications existantes. En raison de toutes ces caractéristiques, la technologie UWB a été considérée comme une technologie prometteuse pour les applications WSN. Cependant, il existe plusieurs défis technologiques pour l'implémentation des systèmes UWB. A savoir, une distorsion différente de la forme d'onde du signal reçu pour chaque trajet, la conception d'antennes très larges bandes de petites dimensions et non coûteuses, la synchronisation d'un signal impulsionnel, l'utilisation de modulation d'onde d'ordre élevé pour améliorer le débit etc. Dans ce travail, Nous allons nous intéresser à l'étude et l'amélioration de la synchronisation temporelle dans les systèmes ULB

Ultra-Wideband Pulse Doppler Radar for Short-Range Targets

This thesis addresses the design and characterization of a pulse Doppler radar designed to detect targets at short range (R ≤ 7m). To minimize the shortest detectable range, a subnanosecond transmitted pulsewidth is desired. UWB design techniques were combined with a pulse Doppler radar architecture to demonstrate a full radar, including the transmitter, receiver, simulated channel, and post processor. The transmitted pulse train has a 2.5GHz carrier frequency, a 730 ps pulsewidth, and a 1GHz 10 dB-bandwidth. The PRF of the radar is 20 MHz, which allows unambiguous range and Doppler detection with a single PRF. The peak transmitted power is 1.2W. The characteristics of the transmitted waveform provide fine range accuracy (δR = ±0.03m), facilitate a short minimum range, and allow for an efficient transmitter design. The receiver was designed to complement the transmitter; it has a homodyne architecture and is pulsed to isolate a specific detectable range. A closed-loop channel model was designed to simulate the range delay, Doppler shift, and channel attenuation of a moving target; the model is connected to the transmitter and receiver with coaxial cable, facilitating bench-top characterization of the radar and eliminating some effects of wireless transmission, such as multipath. Extensive closed-loop radar testing was performed, and the following radar characteristics were determined: (1) The minimum detectable SNR, assuming a 36.5 μs integration time, is 0 dB. (2) Assuming a transmitter-to-receiver isolation of 80 dB, the minimum range of the radar is R[sub]min = 1:3m+R[sub]lk, where R[sub]lk is the apparent leakage range between the transmitter and receiver. Depending on the antenna system design, the radar can detect targets from 1:5m ≤ R ≤ 7m, meeting the original goal of this work. These results support the supposition that a UWB pulse Doppler radar architecture can be employed for short-range, moving target detection

Antennas and Propagation

This Special Issue gathers topics of utmost interest in the field of antennas and propagation, such as: new directions and challenges in antenna design and propagation; innovative antenna technologies for space applications; metamaterial, metasurface and other periodic structures; antennas for 5G; electromagnetic field measurements and remote sensing applications