VCO-based ADCs Design Techniques for Communication Systems

This work presents a novel technique to implement voltage-controlled oscillator based continuous-time Delta-Sigma analog-to-digital converters (VCO-based CT-ΔΣ ADCs) in closed-loop configuration. Over the past years there has been an upward trend in the use of these type of converters for instrumentation, audio and communication applications. The reason is that they are mostly digital and thus benefit from advances in deep-submicron CMOS processes. VCO-based ADCs have been widely studied in a great deal of papers and it is known that one of its main drawbacks is the non-linearity it presents. To overcome this issue, to place the VCO within a closed-loop is usually done to attenuate its input magnitude level. However, to do so it is needed a digital-to-analog converter (DAC) as in a conventional CT-ΔΣ, therefore it is required for the DAC to be simple and it cannot present a high number of elements, being the latter a bottleneck for implementing VCOs with a high number of inverters. This works presents a technique that enables to use VCOs with severals inverters while keeping the same number of DAC elements as before. Based upon previous theoretical studies of the VCO-based ADCs which model it as a pulse frequency modulation encoder, this new technique is analyzed and linear models are developed in order to study its viability at system level. Moreover, how impairments related to a real implementation affect the use of this technique are also analyzed. The contributions proposed in this document are focused but not limited to communication applications.Máster Universitario en Ingeniería de Sistemas Electrónicos y Aplicaciones. Curso 2018/201

Herramienta de modelado y simulación de convertidores sobremuestrados en MATLAB/Simulink

En el presente documento se presenta una nueva herramienta de modelado basado en MATLAB/SIMULINK para el desarrollo de convertidores sobremuestreados . Este tipo de convertidores suelen estar presentes en aplicaciones de comunicaciones y en sensores. De forma tradicional, están formador por OTAs, sin embargo, con el avance en los procesos CMOS de las últimas décadas, la parte analógica se ha vuelto complicada en las tecnología nanométricas actuales. Por el contrario, la parte digital se beneficia de esta empequeñecimiento y por lo tanto, una nueva alternativa ha surgido, convertidores ADC basados en VCO Debido a la naturaleza del proceso de manufacturación, una serie de pasos son necesario para llegar a un circuito final. Uno de estos primeros pasos en el diseño ocurre a nivel de sistema, y precisamente es el foco de atención del presente trabajo. Esta parte consiste en el modelado comportamental que busca un continuo balance entre precisión y rendimiento de las simulaciones: la primera necesita ser adecuada para asegurar un modelo fiable y la segunda tiene que ser lo suficientemente rápida dado que se necesitan realizar un gran número de simulaciones. Además, con cada iteración en el modelo, el balance se debe mantener. Así, surge la necesidad de una herramienta que facilite esta tarea y así, se propone en el presente documento una biblioteca en Simulink con una serie de componentes que modelan elementos clave, esto es, OTAs y VCOs, en un convertidor ADC sobremuestreado. Un estudio y descripción de los elementos se presentan, así como la implementación en un modelo comportamental completo de un ADC basado en VCO.This work presents a new tool based in MATLAB/SIMULINK for the design of oversampled Analog-to-Digital data Converters (ADC) in continuous-time at system level. These type of data converters are usually present in communications applications and some sensors. Traditionally, they are constitued by OTAs, albeit with the advances in the last decades in the CMOS processes, the analog part have become troublesome in current nanometer technologies. Conversely, the digital part benefits from this shrink and consequently a new alternative has appeared, that is, VCO-based ADC. Given the nature of the manufacturing process, a series of steps are needed in order to yield the final circuit. One of the first steps in the design occurs at system level, and precisely that is the one in which this work focuses on. This stage consists on a behavioral model that craves for a constant balance between accuracy and speed simulation: the former needs to be adequate in order to assure a trustworthy model and the latter needs to be fast enough given that a notable numbers of simulation runs are going to be performed. Furthermore, with each iteration on the model the balance must be kept. Thus, the need for a tool that eases this task arises and therefore, here it is proposed a Simulink library with a series of components, modelling some key elements, that is, OTAs and VCOs, in an oversampled ADC. A study and description of the elements are presented, along with an implementation on a full behavioral model of an ADC. It is noted that as a consequence of a inherent property of the system level, the library is neither limited nor linked to a certain CMOS process, so it can be applied, pretty much, when required. Furthermore, although in the present document the application highlighted is on oversampled data-converters, the library can be of use on another area of application as long as it fulfills the requirements needed by the designer.Ingeniería Electrónica Industrial y Automátic

Analysis of in-band spurious tones of VCO-based analog filters and mitigation techniques

Proceedings of: 2023 IEEE International Symposium on Circuits and Systems (ISCAS), 21-25 May 2023, Monterey, USA.Recently VCO-based filters have been used to implement feature extraction in voice recognition systems. Typically implemented filter structures embed the VCOs in a feedback loop. In these implementations, harmonic distortion has been observed in the output signal. This harmonic distortion has been attributed to ring oscillator nonlinearity but its origin stems from a system level problem. In this manuscript we will analyze this problem by looking at the cross modulation of Pulse Frequency Modulation (PFM) side-bands and we will explain how this creates the previously misunderstood harmonic distortion. Moreover, we will propose efficient techniques to mitigate these harmonic components and show that they can easily be implemented in hardware.This paper was supported by program H2020-MSCA-ITN-2020 grant Nr. 956601 and project PID2020-118804RB-I00 of the Spanish Agency of Research (AEI) and by FWO-Vlaanderen

Ring-oscillator with multiple transconductors for linear analog-to-digital conversion

This paper proposes a new circuit-based approach to mitigate nonlinearity in open-loop ring-oscillator-based analog-to-digital converters (ADCs). The approach consists of driving a current-controlled oscillator (CCO) with several transconductors connected in parallel with different bias conditions. The current injected into the oscillator can then be properly sized to linearize the oscillator, performing the inverse current-to-frequency function. To evaluate the approach, a circuit example has been designed in a 65-nm CMOS process, leading to a more than 3-ENOB enhancement in simulation for a high-swing differential input voltage signal of 800-mVpp, with considerable less complex design and lower power and expected area in comparison to state-of-the-art circuit based solutions. The architecture has also been checked against PVT and mismatch variations, proving to be highly robust, requiring only very simple calibration techniques. The solution is especially suitable for high-bandwidth (tens of MHz) medium-resolution applications (10–12 ENOBs), such as 5G or Internet-of-Things (IoT) devices.This research was funded by Project TEC2017-82653-R, Spain

Movimientos en masa en la cuenca del río Huachecsa, Chavín de Huántar

El 17 de enero de 1945 a las 7.00 am, una avalancha de hielo proveniente del Nevado Huantsán a 6 369 m.s.n.m. se precipitó sobre la laguna Ayhuinyaraju, rompiendo su dique morrénico y precipitándose sobre la laguna de Carhuacocha dando origen así al flujo de detritos (“aluvión”) que bajó por el río Huachecsa, causando la destrucción parcial del poblado de Chavín de Huantar, la muerte de numerosos pobladores y sepultó al complejo arqueológico del mismo nombre situado a 200 metros aguas abajo del poblado (Indacochea et al, 1947). El sitio arqueológico de Chavín de Huantar (1 300 a 400 aC.) está ubicado a 3 185 m.s.n.m. sobre el flanco oriental de la Cordillera Blanca entre los ríos Mosna y Huachecsa, en el departamento de Ancash. Se trata de un conjunto arquitectónico monumental de aproximadamente 13 hectáreas de extensión. Este monumento arqueológico es un importante centro ceremonial que data del primer milenio a.C. En los años 20, del siglo pasado, el eminente arqueólogo Julio C. Tello reconoció su importancia fundamental para la historia del Perú antiguo convirtiéndola en pieza clave para su visión del origen de la cultura peruana. El complejo arqueológico, antes de su puesta en valor, fue usado como cantera y destruido por enormes flujos de detritos (“aluviones”) que sepultaron el sitio después de su abandono, hacia 200 años a.C. Para estudiar esta problemática la Dirección de Geología Ambiental del INGEMMET organizó una Escuela de Campo cuya localidad base fue el distrito de Chavín, provincia de Huari, Región Ancash, la cual se realizó entre los días 4 al 10 de Agosto de 2006, estos trabajos contaron con la dirección del Dr. Víctor Carlotto C., la colaboración del Ing. Bilberto Zavala C., y la coordinación general del Ing, Lionel Fidel S., así como la participación de 14 profesionales de esta dirección. El presente informe es el resultado de los trabajos de campo y gabinete, que abarcaron estudios de geología y geodinámica externa de la cuenca del río Huachecsa, el origen del aluvión de 1945, y su recorrido por la quebrada hasta su desembocadura, así como otros aspectos geológicos, geomorfológicos y geodinámicos en el área del depósito del aluvión y en un tramo del río Mosna, entre Chavín y San Marcos