A jittered-sampling correction technique for ADCs

In Analogue to Digital Converters (ADCs) jittered sampling raises the noise floor; this leads to a decrease in its Signal to Noise ratio (SNR) and its effective number of bits (ENOB). This research studies a technique that compensate for the effects of sampling with a jittered clock. A thorough understanding of sampling in various data converters is complied

FFT Interpolation from Nonuniform Samples Lying in a Regular Grid

This paper presents a method to interpolate a periodic band-limited signal from its samples lying at nonuniform positions in a regular grid, which is based on the FFT and has the same complexity order as this last algorithm. This kind of interpolation is usually termed "the missing samples problem" in the literature, and there exists a wide variety of iterative and direct methods for its solution. The one presented in this paper is a direct method that exploits the properties of the so-called erasure polynomial, and it provides a significant improvement on the most efficient method in the literature, which seems to be the burst error recovery (BER) technique of Marvasti's et al. The numerical stability and complexity of the method are evaluated numerically and compared with the pseudo-inverse and BER solutions.Comment: Submitted to the IEEE Transactions on Signal Processin

Timing Jitter Analysis and Mitigation in Hybrid OFDM-DFMA PONs

Hybrid orthogonal frequency division multiplexing-digital filter multiple access passive optical networks (OFDM-DFMA PONs) offer a cost-effective solution to the challenging requirements of next-generation optical access networks and 5G and beyond radio access networks. It is crucial to consider the impact of timing jitter in any ADC/DAC-based system, therefore this paper presents an in-depth investigation into the impacts of DAC/ADC timing jitter on the hybrid OFDM-DFMA PON's performance. We introduce improved accuracy white and coloured, DAC and ADC timing jitter models, applicable to any DSP-based transmission system. We prove that DAC and ADC timing jitter effects are virtually identical and investigate the effects of white/coloured timing jitter on upstream performance in hybrid OFDM-DFMA PONs and determine the associated jitter-induced optical power penalties. To mitigate against the timing jitter-induced performance degradations, a simple, but highly effective DSP-based technique is implemented which increases robustness against the timing jitter effects and significantly reduces timing jitter-induced optical power penalties. This consequently relaxes DAC/ADC sampling clock jitter requirements and so reduces implementation costs. White (coloured) timing jitter effects are shown to be independent of (dependent on) ONU operating frequency band and a trade-off between DAC and ADC jitter levels can be exploited to reduce ONU costs

A Pipeline Analog-To-Digital Converter for a Plasma Impedance Probe

Space instrumentation technology is an essential tool for rocket and satellite research, and is expected to become popular in commercial and military operations in fields such as radar, imaging, and communications. These instruments are traditionally implemented on printed circuit boards using discrete general-purpose Analog-to-Digital Converter (ADC) devices and other components. A large circuit board is not convenient for use in micro-satellite deployments, where the total payload volume is limited to roughly one cubic foot. Because micro-satellites represent a fast growing trend in satellite research and development, there is motivation to explore miniaturized custom application-specific integrated circuit (ASIC) designs to reduce the volume and power consumption occupied by instrument electronics. In this thesis, a model of a new Plasma Impedance Probe (PIP) architecture, which utilizes a custom-built ADC along with other analog and digital components, is proposed. The model can be fully integrated to produce a low-power, miniaturized impedance probe

Digitally Assisted Multi-Channel Receivers

This work presents a data estimation scheme for wide band multi-channel charge sampling receivers with sinc filter banks together with a complete system calibration and synchronization algorithm for the receiver. A unified model has been defined for the receiver containing all first order mismatches, offsets and imperfections and a technique based on least mean squares algorithm is employed to track these errors. The performance of this technique under noisy channel conditions has been verified. The sinc filter bank is compared with the conventional analog filter banks and it is shown that the sinc filter banks have very low computational complexity in data estimation Nextly, analytical tools for the design of clock-jitter tolerant multi-channel filterbank receivers have been developed. Clock-jitter is one of the most fundamental obstacles for the future generation of wideband receivers. Additionally all the trade-offs and specifications of a design example for a multi-channel receiver that can process a 5 GHz baseband signal with 40 dB of signal-to-noise-ratio (SNR) using sampling clocks that can tolerate up to 5 ps of clock-jitter standard deviation are presented. A novel bandwidth optimization technique has been presented. As a part of it the bandwidth of the filters present in each path is optimized thereby improving the performance of the receiver further in the presence of sampling clock jitter. The amount of bandwidth reduction possible depends on the order of the filter and the noise amplification provided by the reconstruction matrix. It has been shown that 3rd order filters of bandwidth 1 GHz can be replaced with 1st order filters of bandwidth 100 MHz without any depreciation in the output resolution, implying huge power savings

Sub-Nyquist Sampling: Bridging Theory and Practice

Sampling theory encompasses all aspects related to the conversion of continuous-time signals to discrete streams of numbers. The famous Shannon-Nyquist theorem has become a landmark in the development of digital signal processing. In modern applications, an increasingly number of functions is being pushed forward to sophisticated software algorithms, leaving only those delicate finely-tuned tasks for the circuit level. In this paper, we review sampling strategies which target reduction of the ADC rate below Nyquist. Our survey covers classic works from the early 50's of the previous century through recent publications from the past several years. The prime focus is bridging theory and practice, that is to pinpoint the potential of sub-Nyquist strategies to emerge from the math to the hardware. In that spirit, we integrate contemporary theoretical viewpoints, which study signal modeling in a union of subspaces, together with a taste of practical aspects, namely how the avant-garde modalities boil down to concrete signal processing systems. Our hope is that this presentation style will attract the interest of both researchers and engineers in the hope of promoting the sub-Nyquist premise into practical applications, and encouraging further research into this exciting new frontier.Comment: 48 pages, 18 figures, to appear in IEEE Signal Processing Magazin

Low-voltage low-power continuous-time delta-sigma modulator designs

Ph.DDOCTOR OF PHILOSOPH

Data processing pipelines tailored for imaging Fourier-transform spectrometers

Cette thèse propose des algorithmes d'acquisition et de traitement de données adaptés aux spectromètres imageurs par transformation de Fourier. L'objectif visé est d'alléger le fardeau de post-traitement, afin que l'usager ait rapidement accès à des spectres étalonnés. La configuration d'instrument étudiée consiste en un interféromètre à balayage continu couplé à une caméra intégratrice à synchronisation externe. Un banc d'essai d'imageur spectral proche/moyen infrarouge fabriqué par la compagnie Telops Inc. a été utilisé pour développer et valider les algorithmes d'acquisition et de traitement de données. Deux thèmes spécifiques ont été étudiés, s'avérant d'intérêt pour cette configuration particulière. Le premier thème concerne l'optimisation du processus de. collection de données. Une nouvelle technique d'échantillonnage d'interférogramme est démontrée pour les spectromètres imageurs par transformation de Fourier. Cette technique permet à la fois de minimiser la quantité de données et de corriger au besoin la gigue d'échantillonnage induite par le retard inhérent au processus de photointégration. Le deuxième thème concerne l'étalonnage spectral de mesures obtenues avec une matrice de détecteurs. Une technique d'intégration de fonction d'appareil est adaptée aux spectromètres imageurs par transformation de Fourier. Des résultats d'étalonnage sont présentés, ainsi que des résultats d'élargissement de champ de vue qui dévoilent un comportement inattendu de l'instrument. Une étude de l'amplitude et de la phase de deux interférogrammes laser est ensuite faite pour scruter certaines contributions instrumentales. L'approche utilisée démontre la présence d'une subtile altération due à l'instrument. Un algorithme de correction est finalement proposé pour compléter le processus d'étalonnage spectral

Architecture, Modeling, and Analysis of a Plasma Impedance Probe

Variations in ionospheric plasma density can cause large amplitude and phase changes in the radio waves passing through this region. Ionospheric weather can have detrimental effects on several communication systems, including radars, navigation systems such as the Global Positioning Sytem (GPS), and high-frequency communications. As a result, creating models of the ionospheric density is of paramount interest to scientists working in the field of satellite communication. Numerous empirical and theoretical models have been developed to study the upper atmosphere climatology and weather. Multiple measurements of plasma density over a region are of marked importance while creating these models. The lack of spatially distributed observations in the upper atmosphere is currently a major limitation in space weather research. A constellation of CubeSat platforms would be ideal to take such distributed measurements. The use of miniaturized instruments that can be accommodated on small satellites, such as CubeSats, would be key to acheiving these science goals for space weather. The accepted instrumentation techniques for measuring the electron density are the Langmuir probes and the Plasma Impedance Probe (PIP). While Langmuir probes are able to provide higher resolution measurements of relative electron density, the Plasma Impedance Probes provide absolute electron density measurements irrespective of spacecraft charging. The central goal of this dissertation is to develop an integrated architecture for the PIP that will enable space weather research from CubeSat platforms. The proposed PIP chip integrates all of the major analog and mixed-signal components needed to perform swept-frequency impedance measurements. The design\u27s primary innovation is the integration of matched Analog-to-Digital Converters (ADC) on a single chip for sampling the probes current and voltage signals. A Fast Fourier Transform (FFT) is performed by an off-chip Field-Programmable Gate Array (FPGA) to compute the probes impedance. This provides a robust solution for determining the plasma impedance accurately. The major analog errors and parametric variations affecting the PIP instrument and its effect on the accuracy and precision of the impedance measurement are also studied. The system clock is optimized in order to have a high performance ADC. In this research, an alternative clock generation scheme using C-elements is described to reduce the timing jitter and reference spurs in phase locked loops. While the jitter performance and reference spur reduction is comparable with prior state-of-the-art work, the proposed Phase Locked Loop (PLL) consumes less power with smaller area than previous designs