Ginés Doménech-Asensi

Comparative analysis of two operational amplifier topologies for a 40MS/s 12-bit pipelined ADC in 0.35μm CMOS

This paper describes a comparative analysis between two topologies of operational amplifiers to design a 40 MS/s 12-bit pipeline analog to digital converter (ADC). The analysis includes AC and transient simulation to select the proper topology. This ADC is implemented in a 0.35 mum AMS CMOS technology with 3.3 V single power supply. The capacitors and selected operational amplifiers were scaled for low power dissipation. All analog components of this pipeline ADC are fully differential, as there are dynamic comparators, analog multiplexers and operational amplifiers with gain boosting.

Empirical model generation techniques for planar microwave components using electromagnetic linear regression models

Accurate and efficient empirical model generation techniques of microwave devices, for a large range of geometric and material parameters opportunely chosen, are presented. The empirical models are based on multiple linear regression approach, which compensates the error between an initial inaccurate empirical model and an electromagnetic (EM) full-wave solver (or measurement data). The aim of these techniques is to generate accurate empirical models, which are computationally very efficient with respect to any EM technique. These simple models could be integrated in a toolbox of any commercially available computed-aided design tools for RF/microwave circuits. Comparisons with artificial neural networks and linear-regression-based models are listed and discussed for the dispersion of a microstrip transmission line propagating the quasi-TEM mode and a microwave tunable phase shifter propagating the even mode.

Distance Measurement Error in Time-of-Flight Sensors Due to Shot Noise

Unlike other noise sources, which can be reduced or eliminated by different signal processing techniques, shot noise is an ever-present noise component in any imaging system. In this paper, we present an in-depth study of the impact of shot noise on time-of-flight sensors in terms of the error introduced in the distance estimation. The paper addresses the effect of parameters, such as the size of the photosensor, the background and signal power or the integration time, and the resulting design trade-offs. The study is demonstrated with different numerical examples, which show that, in general, the phase shift determination technique with two background measurements approach is the most suitable for pixel arrays of large resolution.

A secure energy-efficient m-banking application for mobile devices

Mobile banking is one of the emerging services in telecommunications due to the explosive increase in the number of mobile customers around the world. Solutions for mobile banking are varied, ranging from the use of Wireless Transport Layer Security, Security Socket Layer, or application-layer based options. Whereas security at the transport layer is a good choice for e-banking, using it in a mobile device presents several disadvantages such as high energy consumption. In this work, we present a secure energy-efficient m-banking solution for mobile devices. We propose an application-layer protocol whose message formats and message exchanges are designed to reduce time processing, bandwidth use, and energy consumption. Through experimentation, we demonstrate that our secure solution reduces power and energy consumption in more than 30% compared to a secure web-access from the mobile device.

Low-Frequency CMOS Bandpass Filter for PIR Sensors in Wireless Sensor Nodes

In this paper, a CMOS fourth-order low-frequency bandpass filter for passive pyroelectric infrared sensors is presented. The sensor is intended for use in wireless sensor nodes, demanding strict low power requirements. The final use of these sensor nodes is an ambient assisted living system for elderly people living alone at home. A NICERA RE200B passive pyroelectric infrared sensor with a measured steady operation current of 3.5 μA has been used. The filter has been implemented cascading two biquad OTA-C filtering stages. OTA-C topology has been selected due to the extremely large time constant of the filter. The second-order stage circuit has been prototyped in a 0.35-μm CMOS process and power consumption is below 6.5 μW from a 3 V supply. A central frequency of 1.49 Hz, with Q = 0.5, and a gain of 45 V/V was achieved.

Accurate and reusable macromodeling technique using a fuzzy-logic approach

An approach for applying fuzzy logic for accurate analog circuit macromodel sizing is presented. In our proposed method, multiple adaptive neuro-fuzzy inference systems (MANFIS) are trained to predict the performance characteristics (gain, bandwidth) of a fully differential telescopic transconductance amplifier (OTA). The neuro-fuzzy computed characteristic values are in excellent agreement and one order of magnitude faster than those obtained from device level SPICE simulations. This technique allows the generation of accurate, efficient and reusable models of analog circuits. It is demonstrated and compared with other classical techniques like polynomial regression or artificial neural network approaches.

The dickson charge pump as voltage booster for light energy harvesting on CMOS vision chips

The photodiode structures on a vision chip can be configured in either imaging (IM) or energy harvesting (EHM) mode. The upper voltage achieved with on-chip energy harvesting is below 0.5 V on standard CMOS technologies, thus DC/DC converters are needed to reach the power supply of today CMOS technologies. This paper addresses the design of a Dickson charge pump to this purpose on a standard 0.18 μm CMOS technology. The paper provides data on how the photoconversion characteristics of the photodiodes change, as well as on how the performance metrics of a CMOS vision chip are affected when the energy harvested in EHM is used as power supply in IM.

A fourth order CMOS band pass filter for PIR sensors

This paper describes a fourth order continuous time band pass filter used to filter analog signals coming from passive infrared sensors (PIR). Specifications for this filter are characterized by an extremely large time constant which strongly condition the topology of the filter used. Moreover, very low power consumption is also required, since these filters are implemented together with the sensor in wireless sensor motes for ambient intelligence applications where power dissipation is a key factor. In this paper a low power and low frequency fourth order CMOS band pass filtering for PIR signal conditioning is presented. Results obtained from simulations of this circuit show the initial validity of the proposed approach.

Four-transistor pinned photodiodes in standard CMOS technologies for time-of-flight sensors

This paper studies pinned photodiodes with transmission gates and floating diffusions (FD) as a possible pixel structure for time-of flight sensors fabricated in standard CMOS technologies. Although the doping profiles cannot be modified in standard technologies, it is possible to adjust the geometrical parameters that have an important influence on the performance of the devices. The study is made in terms of the uncertainty introduced in the distance measurement due to the dark current, the noise introduced by the reset transistor and the transmission speed of the photogenerated charges to the FD.

Dark current in standard CMOS pinned photodiodes for Time-of-Flight sensors

This paper deals with the optimal design of pinned photodiodes on standard CMOS technologies for Time-of-Flight sensors with the twofold objective of minimizing the dark current while ensuring an optimal charge transfer. The results are verified through CAD simulations with realistic doping profiles for a standard 0.18 μm CMOS technology. To the best of our knowledge, no similar analysis have been previously reported in the literature.