Author: Mohammad Reza Salehi
Publisher:
ISBN:
Category :
Languages : fr
Pages : 154
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Cette thèse porte sur l'étude des différentes sources de bruit et l'influence de la dispersion chromatique de la fibre-optique dans les transmissions optiques de signaux hyperfréquences. Nous nous sommes intéressés au traitement de signal microondes par voie optique, en utilisant un interféromètre de type Mach-Zehnder. Nous avons calculé la formule théorique du bruit d'intensité (RIN) avec et sans dispersion chromatique de la fibre optique. Nous avons comparé la réponse microondes expérimentale des lasers DFB, et le RIN, et proposé des modèles de simulation du RIN basé sur un nombre limité de paramètres. Une très bonne correspondance entre les données expérimentales et les prévisions théoriques issues de notre modèle est observée. Ensuite, nous avons présenté les bruits à la photodétection et avons également expliqué la dépendance du bruit à la puissance optique sur le photodétecteur. Nous avons analysé ensuite le bruit de phase du laser dans un système interférométrique optique de tratement de signal microonde. Nous avons calculé et simulé la densité spectrale de bruit dans la puissance optique détectée dans le cas du bruit blanc et de buit flicker en 1/f additif. La comparaison entre le bruit d'intensité direct (RIN direct) et le bruit de phase converti (RIN interférométrique) a été présenté dans cette thèse. Nous avons également analysé l'influence sur le RIN interférométrique de la dispersion dans la raie émise par le laser. L'accent de cette étude porte sur la conversion de bruit-FM en bruit d'intensité et l'influence de l'indice de modulation de fréquence dans un lien optique-RF incluant un interféromètre UMZ et un laser DFB modulé directement. Les résultats théoriques et les résultats de mesures ont été comparés et sont en excellent accord. Enfin, nous avons également illustré les solutions pour réduire le bruit dans un lien optique.
Author:
Publisher:
ISBN:
Category : Electronics
Languages : en
Pages : 300
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Author: Ameya Bhide
Publisher: Linköping University Electronic Press
ISBN: 9175190176
Category :
Languages : en
Pages : 141
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Book Description
Digital-to-analog (D/A) converters (or DACs) are one the fundamental building blocks of wireless transmitters. In order to support the increasing demand for highdata-ate communication, a large bandwidth is required from the DAC. With the advances in CMOS scaling, there is an increasing trend of moving a large part of the transceiver functionality to the digital domain in order to reduce the analog complexity and allow easy reconguration for multiple radio standards. ?? DACs can t very well into this trend of digital architectures as they contain a large digital signal processing component and oer two advantages over the traditionally used Nyquist DACs. Firstly, the number of DAC unit current cells is reduced which relaxes their matching and output impedance requirements and secondly, the reconstruction lter order is reduced. Achieving a large bandwidth from ?? DACs requires a very high operating frequency of many-GHz from the digital blocks due to the oversampling involved. This can be very challenging to achieve using conventional ?? DAC architectures, even in nanometer CMOS processes. Time-interleaved ?? (TIDSM) DACs have the potential of improving the bandwidth and sampling rate by relaxing the speed of the individual channels. However, they have received only some attention over the past decade and very few previous works been reported on this topic. Hence, the aim of this dissertation is to investigate architectural and circuit techniques that can further enhance the bandwidth and sampling rate of TIDSM DACs. The rst work is an 8-GS/s interleaved ?? DAC prototype IC with 200-MHz bandwidth implemented in 65-nm CMOS. The high sampling rate is achieved by a two-channel interleaved MASH 1-1 digital ?? modulator with 3-bit output, resulting in a highly digital DAC with only seven current cells. Two-channel interleaving allows the use of a single clock for both the logic and the nal multiplexing. This requires each channel to operate at half the sampling rate i.e. 4 GHz. This is enabled by a high-speed pipelined MASH structure with robust static logic. Measurement results from the prototype show that the DAC achieves 200-MHz bandwidth, –57-dBc IM3 and 26-dB SNDR, with a power consumption of 68-mW at 1-V digital and 1.2-V analog supplies. This architecture shows good potential for use in the transmitter baseband. While a good linearity is obtained from this DAC, the SNDR is found to be limited by the testing setup for sending high-speed digital data into the prototype. The performance of a two-channel interleaved ?? DAC is found to be very sensitive to the duty-cycle of the half-rate clock. The second work analyzes this eect mathematically and presents a new closed-form expression for the SNDR loss of two-channel DACs due to the duty cycle error (DCE) for a noise transfer function (NTF) of (1 — z—1)n. It is shown that a low-order FIR lter after the modulator helps to mitigate this problem. A closed-form expression for the SNDR loss in the presence of this lter is also developed. These expressions are useful for choosing a suitable modulator and lter order for an interleaved ?? DAC in the early stage of the design process. A comparison between the FIR lter and compensation techniques for DCE mitigation is also presented. The nal work is a 11 GS/s 1.1 GHz bandwidth time-interleaved DAC prototype IC in 65-nm CMOS for the 60-GHz radio baseband. The high sampling rate is again achieved by using a two-channel interleaved MASH 1-1 architecture with a 4-bit output i.e only fteen analog current cells. The single clock architecture for the logic and the multiplexing requires each channel to operate at 5.5 GHz. To enable this, a new look-ahead technique is proposed that decouples the two channels within the modulator feedback path thereby improving the speed as compared to conventional loop-unrolling. Full speed DAC testing is enabled by an on-chip 1 Kb memory whose read path also operates at 5.5 GHz. Measurement results from the prototype show that the ?? DAC achieves >53 dB SFDR, < —49 dBc IM3 and 39 dB SNDR within a 1.1 GHz bandwidth while consuming 117 mW from 1 V digital/1.2 V analog supplies. The proposed ?? DAC can satisfy the spectral mask of the 60-GHz radio IEEE 802.11ad WiGig standard with a second order reconstruction lter.
Author: Alexander V. Sergienko
Publisher: CRC Press
ISBN: 1420026607
Category : Science
Languages : en
Pages : 248
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Book Description
All current methods of secure communication such as public-key cryptography can eventually be broken by faster computing. At the interface of physics and computer science lies a powerful solution for secure communications: quantum cryptography. Because eavesdropping changes the physical nature of the information, users in a quantum exchange can easily detect eavesdroppers. This allows for totally secure random key distribution, a central requirement for use of the one-time pad. Since the one-time pad is theoretically proven to be undecipherable, quantum cryptography is the key to perfect secrecy. Quantum Communications and Cryptography is the first comprehensive review of the past, present, and potential developments in this dynamic field. Leading expert contributors from around the world discuss the scientific foundations, experimental and theoretical developments, and cutting-edge technical and engineering advances in quantum communications and cryptography. The book describes the engineering principles and practical implementations in a real-world metropolitan network as well as physical principles and experimental results of such technologies as entanglement swapping and quantum teleportation. It also offers the first detailed treatment of quantum information processing with continuous variables. Technologies include both free-space and fiber-based communications systems along with the necessary protocols and information processing approaches. Bridging the gap between physics and engineering, Quantum Communications and Cryptography supplies a springboard for further developments and breakthroughs in this rapidly growing area.
Author:
Publisher:
ISBN:
Category : Telecommunication
Languages : en
Pages : 494
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Author:
Publisher:
ISBN:
Category : Television
Languages : en
Pages : 14
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Book Description
Report to the President on investigation no. 332-95 under section 332 of the Tariff Act of 1930, as amended.
Author: Paolo Prandoni
Publisher: Collection Savoir suisse
ISBN: 2940222207
Category : Signal processing
Languages : en
Pages : 392
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Book Description
With a novel, less classical approach to the subject, the authors have written a book with the conviction that signal processing should be taught to be fun. The treatment is therefore less focused on the mathematics and more on the conceptual aspects, the idea being to allow the readers to think about the subject at a higher conceptual level, thus building the foundations for more advanced topics. The book remains an engineering text, with the goal of helping students solve real-world problems. In this vein, the last chapter pulls together the individual topics as discussed throughout the book into an in-depth look at the development of an end-to-end communication system, namely, a modem for communicating digital information over an analog channel.
Author: Richard Escadafal
Publisher: IRD Orstom
ISBN:
Category : Geographic information systems
Languages : fr
Pages : 674
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Book Description
ISSS congress remote sensing
Author: Michel Jézéquel
Publisher: Elsevier Science & Technology
ISBN:
Category : Error-correcting codes (Information theory)
Languages : en
Pages : 232
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Book Description
Three leading areas of information about turbo codes, a new type of correction code, are examined: the construction of concatenated codes and their properties, the problems of decoding, and the extension of turbo codes to other applications.
Author: Neil Gershenfeld
Publisher: Cambridge University Press
ISBN: 9780521580441
Category : Computers
Languages : en
Pages : 390
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Book Description
The Physics of Information Technology explores the familiar devices that we use to collect, transform, transmit, and interact with electronic information. Many such devices operate surprisingly close to very many fundamental physical limits. Understanding how such devices work, and how they can (and cannot) be improved, requires deep insight into the character of physical law as well as engineering practice. The book starts with an introduction to units, forces, and the probabilistic foundations of noise and signalling, then progresses through the electromagnetics of wired and wireless communications, and the quantum mechanics of electronic, optical, and magnetic materials, to discussions of mechanisms for computation, storage, sensing, and display. This self-contained volume will help both physical scientists and computer scientists see beyond the conventional division between hardware and software to understand the implications of physical theory for information manipulation.
