177 research outputs found
A Fully Differential Digital CMOS Pulse UWB Generator
A new fully-digital CMOS pulse generator for impulse-radio Ultra-Wide-Band (UWB) systems is presented. First, the shape of the pulse which best fits the FCC regulation in the 3.1-5 GHz sub-band of the entire 3.1-10.6 GHz UWB bandwidth is derived and approximated using rectangular digital pulses. In particular, the number and width of pulses that approximate an ideal template is found through an ad-hoc optimization methodology. Then a fully differential digital CMOS circuit that synthesizes the pulse sequence is conceived and its functionality demonstrated through post-layout simulations. The results show a very good agreement with the FCC requirements and a low power consumptio
A low-cost time-hopping impulse radio system for high data rate transmission
We present an efficient, low-cost implementation of time-hopping impulse
radio that fulfills the spectral mask mandated by the FCC and is suitable for
high-data-rate, short-range communications. Key features are: (i) all-baseband
implementation that obviates the need for passband components, (ii) symbol-rate
(not chip rate) sampling, A/D conversion, and digital signal processing, (iii)
fast acquisition due to novel search algorithms, (iv) spectral shaping that can
be adapted to accommodate different spectrum regulations and interference
environments. Computer simulations show that this system can provide 110Mbit/s
at 7-10m distance, as well as higher data rates at shorter distances under FCC
emissions limits. Due to the spreading concept of time-hopping impulse radio,
the system can sustain multiple simultaneous users, and can suppress narrowband
interference effectively.Comment: To appear in EURASIP Journal on Applied Signal Processing (Special
Issue on UWB - State of the Art
Impulse radio ultrawideband pulse shaper based on a programmable photonic chip frequency discriminator
We report and experimentally demonstrate the generation of impulse radio ultrawideband (UWB) pulses using a photonic chip frequency discriminator. The discriminator consists of three add-drop optical ring resonators (ORRs) which are fully programmable using thermo-optical tuning. This discriminator chip in combination with a phase modulator forms a temporal differentiator where phase modulation is converted to intensity modulation (PM-IM conversion). By means of tailoring the discriminator response using either the individual or the cascade of drop and through responses of the ORRs, first-order or second-order temporal differentiations are obtained. Using this principle, the generation of UWB monocycle, doublet and modified doublet pulses are demonstrated. The use of this CMOS-compatible discriminator is promising for the realization of a compact and low cost UWB transmitter
Area and Power Efficient Ultra-Wideband Transmitter Based on Active Inductor
This paper presents the design of an impulse radio ultra-wideband (IR-UWB) transmitter for low-power, short-range, and high-data rate applications such as high density neural recording interfaces. The IR-UWB transmitter pulses are generated by modulating the output of a local oscillator. The large area requirement of the spiral inductor in a conventional on-chip LC tank is overcome by replacing it with an active inductor topology. The circuit has been fabricated in a UMC CMOS 180 nm technology, with a die area of 0.012 mm2. The temporal width of the output waveform is determined by a pulse generator based on logic gates. The measured pulse is compliant with Federal Communications Commission (FCC) power spectral density limits and within the frequency band of 3-6 GHz. For the minimum pulse duration of 1 ns, the energy consumption of the design is 20 pJ per bit, while transmitting at a 200 Mbps data rate with an amplitude of 130 mV
Optical generation of IR-UWB pulse based on weighted sum of modified doublets
We propose a relatively simple optical generation concept for impulse radio ultra wideband (IR-UWB) pulse over fiber transmission using a weighted sum of a modified doublet with its inverted and delayed version. The generated pulses not only fi4ly comply with the FCC spectral mask but also are highly power efficient in the available spectrum. We verified our approach using both simulation and experimental demonstration. The concept has a potential to be integrated with other optical functions on a compact optical chip, making it very suitable for wide UWB deployment for highspeed wireless access at low costfor in-building network applications
High-speed photonic power-efficient ultra-wideband transceiver based on multiple PM-IM conversions
We experimentally demonstrate a novel photonic ultra-wideband (UWB) transceiver with pulse spectral efficiency of 50.97% and transmission speed up to 3.125 Gb/s. The UWB generator only consists of a highly nonlinear fiber (HNLF) and a commercial arrayed-waveguide grating (AWG). By using the concept of multiple cross-phase modulation in the HNLF and multiple phase modulation to intensity modulation conversions in the AWG, a power-efficient UWB pulse is combined with incoherent summation of two asymmetric monocycle pulses with inverted polarities. Benefiting from the ultra-fast response of fiber nonlinearities in the HNLF, onoff keying encoded UWB signals generated at 781.25 Mb/s, 1.5625 Gb/s, and 3.125 Gb/s are all error-free transmitted through a 22.5-km single-mode fiber (SMF) with power penalties lower than 1 dB. The bit-error rate is directly measured on down-converted baseband signals by using optical full rectification and electrical low-pass filtering technologies. The measured electrical spectra before and after 22.5-km SMF link transmission both fully comply with the spectral mask specified by the U.S. Federal Communications Commission (FCC) without power attenuation. © 2006 IEEE.published_or_final_versio
Ultra-wideband indoor communications using optical technology
La communication ultra large bande (UWB) a attirĂ© une Ă©norme quantitĂ© de recherches ces derniĂšres annĂ©es, surtout aprĂšs la prĂ©sentation du masque spectral de US Federal Communications Commission (FCC). Les impulsions ultra-courtes permettent de trĂšs hauts dĂ©bits de faible puissance tout en Ă©liminant les interfĂ©rences avec les systĂšmes existants Ă bande Ă©troite. La faible puissance, cependant, limite la portĂ©e de propagation des radios UWB Ă quelques mĂštres pour la transmission sans fil Ă lâintĂ©rieur dâune piĂšce. En outre, des signaux UWB reçu sont Ă©tendus dans le temps en raison de la propagation par trajet multiple qui rĂ©sulte en beaucoup dâinterfĂ©rence inter-symbole (ISI) Ă haut dĂ©bit. Le monocycle Gaussien, lâimpulsion la plus commune dans UWB, a une mauvaise couverture sous le masque de la FCC. Dans cette thĂšse, nous dĂ©montrons des transmet- teurs qui sont capables de gĂ©nĂ©rer des impulsions UWB avec une efficacitĂ© de puissance Ă©levĂ©e. Une impulsion efficace rĂ©sulte dans un rapport de signal Ă bruit (SNR) supĂ©rieur au rĂ©cepteur en utilisant plus de la puissance disponible sous le masque spectral de la FCC. On produit les impulsions dans le domaine optique et utilise la fibre optique pour les transporter sur plusieurs kilomĂštres pour la distribution dans un rĂ©seau optique pas- sif. La fibre optique est trĂšs fiable pour le transport des signaux radio avec une faible consommation de puissance. On utilise les Ă©lĂ©ments simples comme un modulateur Mach-Zehnder ou un rĂ©sonateur en anneau pour gĂ©nĂ©rer des impulsions, ce qui permet lâintĂ©gration dans le silicium. Compatible avec la technologie CMOS, la photonique sur silicium a un potentiel Ă©norme pour abaisser le coĂ»t et lâencombrement des systĂšmes optiques. La photodĂ©tection convertit les impulsions optiques en impulsions Ă©lectriques avant la transmission sur lâantenne du cĂŽtĂ© de lâutilisateur. La rĂ©ponse frĂ©quentielle de lâantenne dĂ©forme la forme dâonde de lâimpulsion UWB. Nous proposons une technique dâoptimisation non-linĂ©aire qui prend en compte la distorsion dâantenne pour trouver des impulsions qui maximisent la puissance transmise, en respectant le masque spectral de la FCC. Nous travaillons avec trois antennes et concevons une impulsion unique pour chacune dâentre elle. LâamĂ©lioration de lâĂ©nergie des impulsions UWB amĂ©liore directement la SNR au rĂ©cepteur. Les rĂ©sultats de simulation montrent que les impulsions optimisĂ©es amĂ©liorent considĂ©rablement le taux dâerreur (BER) par rapport au monocycle Gaussien sous propagation par trajet multiple. Notre autre contribution est lâĂ©valuation dâun filtre adaptĂ© pour recevoir efficacement des impulsions UWB. Le filtre adaptĂ© est synthĂ©tisĂ© et fabriquĂ© en technologie microstrip, en collaboration avec lâUniversitĂ© McGill comme un dispositif de bande interdite Ă©lectromagnĂ©tique. La rĂ©ponse frĂ©quentielle du filtre adaptĂ© montre une ex- cellente concordance avec le spectre ciblĂ© de lâimpulsion UWB. Les mesures de BER confirment la performance supĂ©rieure du filtre adaptĂ© par rapport Ă un rĂ©cepteur Ă conversion directe. Le canal UWB est trĂšs riche en trajet multiple conduisant Ă lâISI Ă haut dĂ©bit. Notre derniĂšre contribution est lâĂ©tude de performance des rĂ©cepteurs en simulant un systĂšme avec des conditions de canaux rĂ©alistes. Les rĂ©sultats de la simulation montrent que la performance dâun tel systĂšme se dĂ©grade de façon significative pour les hauts dĂ©bits. Afin de compenser la forte ISI dans les taux de transfert de donnĂ©es en Gb/s, nous Ă©tudions lâalgorithme de Viterbi (VA) avec un nombre limitĂ© dâĂ©tats et un Ă©galiseur DFE (decision feedback equalizer). Nous examinons le nombre dâĂ©tats requis dans le VA, et le nombre de coefficients du filtre dans le DFE pour une transmission fiable de UWB en Gb/s dans les canaux en ligne de vue. LâĂ©valuation par simulation de BER confirme que lâĂ©galisation amĂ©liore considĂ©rablement les performances par rapport Ă la dĂ©tection de symbole. La DFE a une meilleure performance par rapport Ă la VA en utilisant une complexitĂ© comparable. La DFE peut couvrir une plus grande mĂ©moire de canal avec un niveau de complexitĂ© relativement rĂ©duit.Ultra-wideband (UWB) communication has attracted an enormous amount of research in recent years, especially after the introduction of the US Federal Communications Commission (FCC) spectral mask. Ultra-short pulses allow for very high bit-rates while low power eliminates interference with existing narrowband systems. Low power, however, limits the propagation range of UWB radios to a few meters for indoors wireless transmission. Furthermore, received UWB signals are spread in time because of multipath propagation which results in high intersymbol interference at high data rates. Gaussian monocycle, the most commonly employed UWB pulse, has poor coverage under the FCC mask. In this thesis we demonstrate transmitters capable of generating UWB pulses with high power efficiency at Gb/s bit-rates. An efficient pulse results in higher signal-to-noise ratio (SNR) at the receiver by utilizing most of the available power under the FCC spectral mask. We generate the pulses in the optical domain and use optical fiber to transport the pulses over several kilometers for distribution in a passive optical network. Optical fiber is very reliable for transporting radio signals with low power consumption. We use simple elements such as a Mach Zehnder modulator or a ring resonator for pulse shaping, allowing for integration in silicon. Being compatible with CMOS technology, silicon photonics has huge potential for lowering the cost and bulkiness of optical systems. Photodetection converts the pulses to the electrical domain before antenna transmission at the user side. The frequency response of UWB antennas distorts the UWB waveforms. We pro- pose a nonlinear optimization technique which takes into account antenna distortion to find pulses that maximize the transmitted power, while respecting the FCC spectral mask. We consider three antennas and design a unique pulse for each. The energy improvement in UWB pulses directly improves the receiver SNR. Simulation results show that optimized pulses have a significant bit error rate (BER) performance improvement compared to the Gaussian monocycle under multipath propagation. Our other contribution is evaluating a matched filter to receive efficiently designed UWB pulses. The matched filter is synthesized and fabricated in microstrip technology in collaboration with McGill University as an electromagnetic bandgap device. The frequency response of the matched filter shows close agreement with the target UWB pulse spectrum. BER measurements confirm superior performance of the matched filter compared to a direct conversion receiver. The UWB channel is very rich in multipath leading to ISI at high bit rates. Our last contribution is investigating the performance of receivers by simulating a system employing realistic channel conditions. Simulation results show that the performance of such system degrades significantly for high data rates. To compensate the severe ISI at gigabit rates, we investigate the Viterbi algorithm (VA) with a limited number of states and the decision feedback equalizer (DFE). We examine the required number of states in the VA, and the number of taps in the DFE for reliable Gb/s UWB trans- mission for line-of-sight channels. Non-line-of-sight channels were also investigated at lower speeds. BER simulations confirm that equalization considerably improves the performance compared to symbol detection. The DFE results in better performance compared to the VA when using comparable complexity as the DFE can cover greater channel memory with a relatively low complexity level
Impulse radio ultra wideband over fiber techniques for broadband in-building network applications
In recent years, the demand for high bandwidth and mobility from the end users has been continuously growing. To satisfy this demand, broadband communication technologies that combined the benefit of both wired and wireless are considered as vital solutions. These hybrid optical wireless solutions enable multi-Gbit/s transmission as well as adequate flexibility in terms of mobility. Optical fiber is the ideal medium for such hybrid solution due its signal transparency and wide bandwidth. On the other hand, ultra wideband(UWB) radio over optical fiber technology is considered to be one of the key promising technologies for broadband communication and sensor network applications. The growing interest for UWB is mainly due to its numerous attractive features, such as low power spectral density, tolerance to multipath fading, low probability of interception, coexistence with other wireless services and capability of providing cost-effective > 1 Gb/s transmission. The main idea of UWB over fiber is to deliver UWB radio signals over optical channels, where the optical part serves as a backbone communication infrastructure to carry the UWB signal with a bandwidth of several GHz. This enables multiple novel applications such as: range extension of high speed wireless personal area networks (WPANs), low cost distributed antenna systems, secure and intelligent networks, or delivering broadband services to remote areas. In particular, this thesis deals with novel concepts on shaping and generation of IR-UWB pulses, theoretical and experimental demonstrations over different fiber types, routing of integrated wired/wireless IR-UWB services and effect of fiber types on ranging/localization of IR-UWB-over-fiber systems. Accordingly, this thesis investigates techniques for delivery of high data rate wireless services using impulse radio ultra wideband (IR-UWB) over fiber technology for both access and in-building network applications. To effectively utilize the emission mask imposed for UWB technologies by the Federal Communications Commission(FCC), novel pulse shaping techniques have been investigated and experimentally demonstrated. Comparison of the proposed pulses with conventional ones in terms of the compliance to the FCC-mask requirements, spectral power efficiencies and wireless coverage has been theoretically studied. Simple and efficient optical generation of the new pulse has been experimentally demonstrated. Furthermore, performance evaluation of 2 Gb/s transmission of IR-UWB over different types of fiber such as 25 km silica single-mode, 4.4 km silica multi-mode and 100 m plastic heavily-multi-mode fiber have been performed. To improve the functionalities of in-building networks for the delivery of wireless services; techniques that provide flexibility in terms of dynamic capacity allocation have been investigated. By employing wavelength conversion based on cross-gain modulation in optical semiconductor amplifiers(SOA), routing of three optical channels of IR-UWB over fiber system has been experimentally realized. To reduce the cost of the overall system and share the optical infrastructure, an integrated testbed for wired baseband data and wireless IR-UWB over 1 km SMF-28 fiber has been developed. Accordingly, 1.25 Gb/s wired baseband and 2 Gb/s wireless IR-UWB data have been successfully transmitted over the testbed. Furthermore, to improve the network flexibility, routing of both wired baseband and wireless signals has been demonstrated. Additionally, the ranging and localization capability of IR-UWB over fiber for in-door wireless picocells have been investigated. The effect of different fiber types (4 km SMF, 4.4 km GI-MMF and 100 m PF GI-POF) on the accuracy of the range estimation using time-of-arrival (ToA) ranging technique has been studied. A high accuracy in terms of cm level was achieved due to the combined effect of high bandwidth IR-UWB pulses, short reach fiber and low chromatic dispersion at 1300nm wavelength. Furthermore, ranging/ localization using IR-UWB over fiber system provides additional benefit of centralizing complex processing algorithms, simplifying radio access points, relaxing synchronization requirement, enabling energy-efficient and efficient traffic management networks. All the concepts, design and system experiments presented in this thesis underline the strong potential of IR-UWB for over optical fiber(silica and plastic) techniques for future smart, capacity and energy-efficient broadband in-building network applications
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