162 research outputs found
An asymmetrical bulk-modified composite MOS transistor with enhanced linearity
In this work, an asymmetrical bulk-linearized composite MOSFET is presented, with an enhanced linear range and an equivalent saturation voltage of up to several hundred mV
even in weak inversion, allowing to implement large MOS resistors. Some preliminary measurements are presented, as well as 150MΩ and 200MΩ equivalent resistors simulations, with a linear range up to 1.5V. A low frequency, 40dB gain, fully integrated cardiac sensing channel filter/amplifier is also shown. Taking advantage of the proposed technique, the circuit consumes only 25nA of supply current.Agencia Nacional de Investigación e Innovació
A Self-biased Current Source, using an Asymmetric Bulk-modified MOS Composite Transistor
In this work a new topology for a self-biased current reference, based on an asymmetric bulk-modified MOS (ABM) composite transistor is presented. Two current references based in this technique were designed: a 13.5nA current reference in a 1.5μm CMOS technology, and a 100nA current reference in a 0.18μm CMOS technology. The latter was designed to minimize the temperature dependence of the output current; the result was less than 5% from 0°C to 100°C, which is a very good result in comparison to other reported similar current references.Agencia Nacional de Investigación e Innovació
Clock-Feedthrough Compensation in MOS Sample-and-Hold Circuits
All MOS sample-and-hold circuits suffer to a greater or lesser extent from clock-feedthrough
(CLFT), also called charge-injection. During the transition from sample to
hold mode, charge is transferred from an MOS transistor switch onto the hold capacitor,
thus the name charge-injection. This error can lead to considerable voltage change across
the capacitor, and predicting the extent of the induced error potentials is important to
circuit designers.
Previous studies have shown a considerable dependency of CLFT on signal voltage, circuit
impedances, clock amplitude and clock fall-time. The focus of this work was on the signal
dependency of the CLFT error and on the CLFT induced signal distortion in open-loop
sample-and-hold circuits. CLFT was found to have a strongly non-linear, signal dependent,
component, which may cause considerable distortion of the sampled signal. The parameters
influencing this distortion were established. It was discovered that distortion could be
reduced by more than 20dB through careful adjustment of the clock fall-rate.
Several circuit solutions that can help reduce the level of distortion arising from CLFT are
presented. These circuits can also reduce the absolute level of CLFT. Simulations showed
their effectiveness, which was also proven in silicon. The CLFT reduction methods used in
these circuits are easily transferable to other switched-capacitor circuits and are suitable for
applications where space is at a premium (as, for example, in analogue neural networks).
A new saturation mode contribution to CLFT was found. It is shown to give rise to
increased CLFT under high injection conditions
Very large time constant Gm-C Filters
In this study a set of tools for the design of fully integrated transconductor-capacitor (Gm-C) filters, with very large time constants and current consumption under one micro-Ampere are presented. The selected application is a 2nd order bandpass-filter-amplifier, with a gain of 400 from 0.5 to 7Hz, carrying out the signal conditioning of a piezoelectric accelerometer which is part of an implantable cardiac pacemaker. The main challenge is to achieve very large time constants, without using any discrete external component. The chosen circuit technique to fulfill the requirement is series-parallel current division applied to standard symmetrical transconductors (OTAs). These circuits have demonstrated to be an excellent solution regarding their occupied area, power consumption, noise, linearity, and particularly offset. OTAs as low as 33pS -equivalent to a 30G resistor-, with up to 1V linear range, and input referred offset of a few mV, were designed, fabricated in a standard 0.8 micron CMOS technology, and tested. The application requires the series-parallel association of a large number of transistors, and the use of bias currents as low as a few pico-Amperes, which is not very common in analog integrated circuits. In this case the designer should employ maximum care in the selection of
the transistor models to be used. A central aspect of this thesis was also to evaluate and
develop noise and offset estimation models which was not obvious in the very beginning of
the research.
In the first two chapters an introduction to the target application is presented, and several
MOS transistor characteristics in terms of the inversion coefficient -using the ACM
transistor model- are evaluated.
In chapter 3 it is discussed whether the usual flicker and thermal noise models are consistent
regarding series-parallel association, and adequately represent the expected noise behavior
under different bias conditions. A consistent, physics-based, one-equation-all-regions model
for flicker noise in the MOS transistor is then presented. Several noise measurements are
included demonstrating that the new model accurately fits widely different bias situations. A
new model for mismatch offset in MOS transistors is presented, as a corollary of the flicker
noise analysis. Finally, the correlation between flicker noise and mismatch offset, that can
be seen as a DC noise, is shown.
In chapter 4, the design of OTAs with an extended linear range, and very low
transconductance, using series-parallel current division is presented. Precise tools are
introduced for the estimation of noise and mismatch offset in series-parallel current mirrors,
that are shown to help in the reduction of inaccuracies in the copy of currents with a large
copy factor. The design and measurement of several OTA examples are presented.
In chapter 5, the developed tools, and the OTAs shown, are employed in the design of the
above mentioned filter for the piezoelectric accelerometer. A general methodology for the
design of Gm-C filters with similar characteristics is established. The filter was fabricated and tested, successfully operating with a total power consumption of 233nA, up to a 2V
power supply, with an input noise and mismatch offset of 2-4 Vrms, and 18 V respectively.
To summarize the main results obtained were: The development of a new flicker noise
model, the study of the effect of mismatch regarding series-parallel association, a new
design methodology for OTAs and Gm-C filters. It is our hope that this constitutes a helpful
set of tools for the circuit designer.En esta tesis se presenta un conjunto de herramientas para el diseño de circuitos integrados
que implementan filtros transconductor-capacitor (Gm-C), de muy altas constantes de
tiempo, con bajo ruido, y consumo de corriente por debajo del micro-Ampere. Como
ejemplo de aplicación se toma un amplificador-pasabanda 2º orden, de ganancia 400 en la
banda de 0.5 a 7Hz, que realiza el acondicionamiento de señal de un acelerómetro
piezoeléctrico a ser empleado en un marcapasos implantable. El principal desafÃo es realizar
en dicho filtro de tiempo continuo, muy altas constantes de tiempo sin usar componentes
externos. La técnica elegida para alcanzar tal objetivo es la división serie-paralelo de
corriente en transconductores (OTAs) simétricos estándar. Estos circuitos demostraron ser
una excelente solución en cuanto al área ocupada, su consumo, ruido, linealidad, y en
particular offset. Se diseñaron, fabricaron, y midieron, OTAs hasta 33pS -equivalente a una
resistencia de 30G -, con hasta 1V de rango de lineal, y offset a la entrada de algunos mV,
utilizando una tecnologÃa CMOS de 0.8 micras de largo mÃnimo de canal. La aplicación
requiere la asociación serie-paralelo de un gran número de transistores, y polarización con
corrientes de hasta pico-Amperes, lo que constituye una situación poco frecuente en
circuitos integrados analógicos. En este marco el diseñador debe elegir los modelos de
transistor con sumo cuidado. Un aspecto central de esta tesis es también, el estudio y
presentación de modelos adecuados de ruido y offset, que no resultan obvios al principio.
En los primeros dos capÃtulos se realiza una introducción y se revisa, utilizando el modelo
ACM, diferentes caracterÃsticas del transistor MOS en función del nivel de inversión.
En el capÃtulo 3 revisa la pertinencia y consistencia frente a la asociación serie-paralelo, de
los modelos usuales de ruido de flicker o 1/f, y térmico. Luego se presenta, incluyendo
medidas, un nuevo modelo fÃsico, consistente, simple, y válido en todas las regiones de
operación del transistor MOS, para el ruido de flicker. Como corolario a este estudio se
presenta un nuevo modelo para estimar el desapareo entre transistores, en función no solo de
la geometrÃa, pero también de la polarización. Se demuestra la correlación, debido a su
origen fÃsico análogo, entre el ruido de flicker y el offset por desapareo que puede ser visto
como un ruido en DC.
En el capÃtulo 4 se presenta el diseño de OTAs con rango de linealidad extendido, y muy
baja transconductancia, utilizando división serie-paralelo de corriente. Se presentan
herramientas precisas para la estimación de offset y ruido y se demuestra la utilidad de la
técnica para reducir el offset en espejos de corriente. Se presenta el diseño y medida de
diversos OTAs.
En el capÃtulo 5, las herramientas desarrolladas, y los OTAs presentados, son empleados en
el diseño del filtro descripto para un acelerómetro piezoeléctrico. Se establece una
metodologÃa general para el diseño de filtros Gm-C con caracterÃsticas similares. El filtro se
fabricó y midió, operando en forma satisfactoria, con un consumo total de 230nA y hasta los
2V de tensión de alimentación, con ruido y offset a la entrada de tan solo 2-4 Vrms, y 18 V
respectivamente.
El desarrollo de un nuevo modelo de ruido 1/f para el transistor MOS, el estudio de la
influencia del offset frente a la asociación serie-paralelo y su aplicación en OTAs, la
metodologÃa de diseño empleada, la demostración del uso de técnicas novedosas en una
aplicación como la elegida que tiene relevancia tecnológica e interés académico; esperamos
que todo ello constituya una contribución valiosa para la comunidad cientÃfica en
microelectrónica y un conjunto de herramientas de utilidad para el diseño de circuitos
Reconfigurable Receiver Front-Ends for Advanced Telecommunication Technologies
The exponential growth of converging technologies, including augmented reality, autonomous vehicles, machine-to-machine and machine-to-human interactions, biomedical and environmental sensory systems, and artificial intelligence, is driving the need for robust infrastructural systems capable of handling vast data volumes between end users and service providers. This demand has prompted a significant evolution in wireless communication, with 5G and subsequent generations requiring exponentially improved spectral and energy efficiency compared to their predecessors. Achieving this entails intricate strategies such as advanced digital modulations, broader channel bandwidths, complex spectrum sharing, and carrier aggregation scenarios. A particularly challenging aspect arises in the form of non-contiguous aggregation of up to six carrier components across the frequency range 1 (FR1). This necessitates receiver front-ends to effectively reject out-of-band (OOB) interferences while maintaining high-performance in-band (IB) operation. Reconfigurability becomes pivotal in such dynamic environments, where frequency resource allocation, signal strength, and interference levels continuously change. Software-defined radios (SDRs) and cognitive radios (CRs) emerge as solutions, with direct RF-sampling receivers offering a suitable architecture in which the frequency translation is entirely performed in digital domain to avoid analog mixing issues. Moreover, direct RF- sampling receivers facilitate spectrum observation, which is crucial to identify free zones, and detect interferences. Acoustic and distributed filters offer impressive dynamic range and sharp roll off characteristics, but their bulkiness and lack of electronic adjustment capabilities limit their practicality. Active filters, on the other hand, present opportunities for integration in advanced CMOS technology, addressing size constraints and providing versatile programmability. However, concerns about power consumption, noise generation, and linearity in active filters require careful consideration.This thesis primarily focuses on the design and implementation of a low-voltage, low-power RFFE tailored for direct sampling receivers in 5G FR1 applications. The RFFE consists of a balun low-noise amplifier (LNA), a Q-enhanced filter, and a programmable gain amplifier (PGA). The balun-LNA employs noise cancellation, current reuse, and gm boosting for wideband gain and input impedance matching. Leveraging FD-SOI technology allows for programmable gain and linearity via body biasing. The LNA's operational state ranges between high-performance and high-tolerance modes, which are apt for sensitivityand blocking tests, respectively. The Q-enhanced filter adopts noise-cancelling, current-reuse, and programmable Gm-cells to realize a fourth-order response using two resonators. The fourth-order filter response is achieved by subtracting the individual response of these resonators. Compared to cascaded and magnetically coupled fourth-order filters, this technique maintains the large dynamic range of second-order resonators. Fabricated in 22-nm FD-SOI technology, the RFFE achieves 1%-40% fractional bandwidth (FBW) adjustability from 1.7 GHz to 6.4 GHz, 4.6 dB noise figure (NF) and an OOB third-order intermodulation intercept point (IIP3) of 22 dBm. Furthermore, concerning the implementation uncertainties and potential variations of temperature and supply voltage, design margins have been considered and a hybrid calibration scheme is introduced. A combination of on-chip and off-chip calibration based on noise response is employed to effectively adjust the quality factors, Gm-cells, and resonance frequencies, ensuring desired bandpass response. To optimize and accelerate the calibration process, a reinforcement learning (RL) agent is used.Anticipating future trends, the concept of the Q-enhanced filter extends to a multiple-mode filter for 6G upper mid-band applications. Covering the frequency range from 8 to 20 GHz, this RFFE can be configured as a fourth-order dual-band filter, two bandpass filters (BPFs) with an OOB notch, or a BPF with an IB notch. In cognitive radios, the filter’s transmission zeros can be positioned with respect to the carrier frequencies of interfering signals to yield over 50 dB blocker rejection
Millimeter-Wave Concurrent Dual-Band BiCMOS RFICs for Radar and Communication RF Front-End
The recent advancement in silicon-based technologies has offered the opportunity for the development of highly-integrated circuits and systems in the millimeter-wave frequency regime. In particular, the demand for high performance multi-band multi-mode radar and communication systems built on silicon-based technologies has been increased dramatically for both military and commercial applications.
This dissertation presents the design and implementation of advanced millimeter-wave front-end circuits in SiGe BiCMOS process including a transmit/receive switch module with integrated calibration function, low noise amplifier, and power amplifier for millimeter-wave concurrent dual-band dual-polarization radars and communication systems. The proposed circuits designed for the concurrent dual-band dual-polarization radars and communication systems were fabricated using 0.18-μm BiCMOS process resulting in novel circuit architectures for concurrent multi-band operation.
The developed concurrent dual-band circuits fabricated on 0.18-μm BiCMOS process include the T/R/Calibration switch module for digital beam forming array system at 24.5/35 GHz, concurrent dual-band low noise amplifiers at 44/60 GHz, and concurrent dual-band power amplifier at 44/60 GHz. With having all the design frequencies closely spaced to each other showing the frequency ratio below 1.43, the designed circuits provided the integrated dual-band filtering function with Q-enhanced frequency responses. Inspired by the composite right/left- handed metamaterial transmission line approaches, the integrated Q-enhanced filtering sub-circuits provided unprecedented dual-band filtering capability.
The new concurrent dual-band dual-mode circuits and system architecture can provide enhanced radar and communication system performance with extended coverage, better image synthesis and target locating by the enhanced diversity. The circuit level hardware research conducted in this dissertation is expected to contribute to enhance the performance of multi-band multi-mode imaging, sensing, and communication array systems
DYNAMIC MAGNETIC EFFECTS IN AMORPHOUS MICROWIRES FOR SENSORS AND CODING APPLICATIONS
This work is devoted to the study of the dynamic properties of magnetic amorphous wires,
in particular, glass-coated microwires, which have small diameters (5-30 microns), outstanding
soft magnetic behaviour with a high permeability and low coercivity, yet, possess a well-defined
magnetic structure.
First part of my PhD research has been devoted to the investigation of a bi-stable
magnetisation reversal in glass-coated amorphous microwires. In contrast to traditional
approaches, where characteristics of the magnetisation reversal are analysed as a consequence of
the eddy current effect, l have applied stochastic methods for modelling the remagnetisation
reversal in the microwires with axial anisotropy. While the eddy current approach, widely
discussed in literature, was based on the single domain model, proposed stochastic approach
takes into account a multi-domain state of studied samples. A modified stochastic Neel-Brown
model of the magnetisation reversal has been proposed enabling the explanation of number of
characteristic parameters of the microwires with axial magnetisation. Such important parameters
of Barkhausen discontinuity as a mean switching field and a standard deviation of the switching
field distribution have been investigated experimentally for understanding the influence of
extrinsic factors such as a slew rate of the alternating magnetic field on applications operation.
A deep understanding of the remagnetisation process in amorphous the microwires with
axial anisotropy was successfully applied in development of a new type of the remote magnetic
interrogation system. My reading system allows the large Barkhausen jump to be detected
without actual contact between the magnetic microwire and the magnetic field detector.
Experiments show that the detection will be possible at a distance of approximately 100-150 mm
from the detecting sensor. A very low cost and easily repetitive amorphous microwires with axial
anisotropy are . incontrovertibly best materials for Electronic Article Surveillance (EAS)
applications.
During the study of the microwires with axial anisotropy and development of the
application based on them, I took part in the investigation of unusual coding methods of the
amorphous microwires using a localised laser annealing treatment. This treatment produces a
multi-pulse code within the wire and therefore adds to the information contained within the wire,
improving reliability and security. I developed and used a magnetic interrogation system
allowing an accurate and reliable test and analysis of the studied samples.
The second part of my PhD research has included investigations of microwires with
circumferential and helical anisotropies. The main interest in these materials is due to their
applications for high-performance magnetic and stress sensors. Within this research project, the
microwires with circumferential/helical anisotropy have been studied in a broad range of
frequencies. A number of dynamic effects have been experimentally obtained and analysed. In
particular, a detailed investigation of dynamic circular hysteresis (10kHz-300kHz) has been
carried out allowing explanation of different behaviour of the materials with
circumferential/helical anisotropy at different frequencies. The experimental curves are proposed
to be analysed in terms of field dependence of characteristic permeabilities: domain wall
displacements (reversible and irreversible) and magnetisation rotation. It was established that
these permeabilities have different field behaviour. That explains different MI patterns at
relatively low frequencies (less than a few MHz) and relatively high frequencies (more than 10
MHz).
Further, some special features of the Magneto-Impedance effect in the microwires with a
circumferential anisotropy such as off-diagonal impedance and microwave impedance have been
considered. In this research, the former presents a considerable interest for development of linear
magnetic sensors and the latter can find application in tuneable microwave materials and
devices. As a result of this study several types of linear, bi-directional MI sensors were
developed. I also developed new MI sensing approaches (such as off-diagonal response) and a
new high performance detection technique allowing us to improve sensitivity, bandwidth, and
linearity at low cost and simple construction ..
The last part of the PhD research has been devoted to an investigation of the stress-impedance
in the ultra high-frequency (UHF) band (300MHz-3 GHz). Based on the experimental
investigation, a new type of a stress-sensitive composite material is proposed. The microwave
effective permittivity of such material depends on mechanical stresses. These composite
materials opens up new possibilities for remote monitoring of stress with the use of microwave
"free-space" techniques. This kind of composite material can be characterised as a "sensing
medium", which images the mechanical stress distribution inside construction or on its surface
CMOS and SOI CMOS FET-based gas sensors
In recent years, there has been considerable interest in the use of gas/vapour monitors and
electronic nose instruments by the environmental, automotive and medical industries. These
applications require low cost and low power sensors with high yield and high reproducibility,
with an annual prospective market of 1 million pounds. Present device and sensor
technologies suffer a major limitation, their incompatibility with a standard silicon CMOS
process. These technologies have either operating/annealing temperatures unsuited for
MOSFET operation or an inappropriate sensing mechanism. The aim of this research is the
development of CMOS compatible gas/vapour sensors, with a low cost of fabrication, high
device repeatability and, in the future, transducer sensor amalgamation. Two novel
approaches have been applied, utilising bulk CMOS and SOI BiCMOS. The bulk CMOS
designs use a MOSFET sensing structure, with an active polymeric gate material, operating at
low temperatures (<100°C), based on an array device of four elements, with channel lengths
of 10 μm or 5 μm. The SOI designs exploit a MOSFET heater with a chemoresistive or
chemFET sensing structure, on a thin membrane formed by the epi-taxial layer. By applying
SOI technology, the first use in gas sensor applications, operating temperatures of up to 300
°C can be achieved at a power cost of only 35 mW (simulated). Full characterisation of the
bulk CMOS chemFET sensors has been performed using electrochemically deposited (e.g.
poly(pyrrole)/BSA)) and composite polymers (e.g. poly(9-vinylcarbazole)) to ethanol and
toluene vapour in air. In addition, environmental factors (humidity and temperature) on the
response and baseline were investigated. This was carried out using a newly developed flow
injection analysis test station, which conditions the test vapour to precise analyte (<15 PPM
of toluene) and water concentrations at a fixed temperature (RT to 105°C +- 0.1), with the
sensor characterised by either I-V or constant current instrumentation. N-channel chemFET
sensors operated at constant current (10 μA) with electrochemically deposited and composite
polymers showed sensitivities of up to 1.1 μV/PPM and 4.0 μV/PPM to toluene vapour and to
1.1 μV/PPM and 0.4 μV/PPM for ethanol vapour, respectively, with detection limits of <20
PPM and <100 PPM to toluene and <20 PPM and 10+ PPM to ethanol vapour (limited by
baseline noise), respectively. These responses followed either a power law (composite
polymers) or a modified Langmuir isotherm model (electrochemically deposited polymers)
with analyte concentration. It is proposed that this reaction-rate limited response is due to an
alteration in polymers work function by either a partial charge transfer from the analyte or a
swelling effect (polymer expansion). Increasing humidity caused, in nearly all cases a
reduction in relative baseline, possible by dipole formation at the gate oxide surface. For the
response, increasing humidity had no effect on sensors with composite polymers and an
increase for sensors with electrochemically-deposited polymers. Higher temperatures caused
a reduction in baseline signal, by a thermal expansion of the polymer, and a reduction in
response explained by the analyte boiling point model describing a reduction in the bulk
solubility of the polymer. Electrical and thermal characterisation of the SOI heaters,
fabricated by the MATRA process, has been performed. I-V measurements show a reduction
in drain current for a MOSFET after back-etching, by a degradation of the carrier mobility.
Dynamic measurement showed a two stage thermal response (dual exponential), as the
membrane reaching equilibrium (100-200 ms) followed by the bulk (1-2 s). A temperature
coefficient of 8 mW/°C was measured, this was significantly higher than expected from
simulations, explained by the membrane being only partially formed. Diode and resistive
temperature sensors showed detection limits under 0.1°C and shown to measure a modulated
heater output of less than 1°C at frequencies higher than 10Hz. The principal research
objectives have been achieved, although further work on the SOI device is required. The
results and theories presented in this study should provide a useful contribution to this
research area
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