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Los circuitos integrados (chips), presentes en la mayoría de sistemas electrónicos, vienen evolucionando en términos de la complejidad de la función que realizan. Para lograr eso, los procesos de fabricación de circuitos integrados mejoran continuamente en términos de las dimensiones mínimas de los dispositivos que pueden ser integrados. Esa miniaturización constante demanda que la tensión de alimentación de los chips sea disminuida, pues de lo contrario los dispositivos más pequeños del sistema estarían sometidos a campos eléctricos suficientemente elevados para damnificar a su estructura. Lamentablemente algunas funciones realizadas en los circuitos integrados requieren de tensiones mayores a la impuesta por la integridad de los dispositivos de dimensiones mínimas. En estos casos se utilizan dispositivos mayores y se necesita de algún circuito que genere esa tensión mayor que la tensión de alimentación. La presente tesis trata del diseño de una bomba de carga que realiza la función de duplicar la tensión de alimentación. Dicho circuito está compuesto por transistores y condensadores de un proceso de fabricación CMOS que permite la formación de canales de 350nm de longitud mínima. Para concluir satisfactoriamente el diseño, se analizaron las relaciones entre parámetros de funcionamiento del circuito y parámetros de diseño tales como dimensiones geométricas de los canales de los transistores y condensadores, corriente de polarización de los transistores y atrasos entre señales digitales de control. Como resultado de ese análisis se propone un procedimiento de diseño de la bomba de carga y se aplica dicho procedimiento al diseño de circuitos con unas determinadas especificaciones de funcionamiento. Las especificaciones verificadas con herramientas de simulación son: 65 μA de corriente de salida nominal, 12,5pF de capacitancia de carga, rango de tensión de alimentación desde 1,5V hasta 3,3V, rango de tensión de salida desde 2,4V hasta 6V y una eficiencia máxima de 80% / Tesis

Personalised medicine is widely considered to be the future of global healthcare, where diagnosis, treatment, and potentially even drug development, will become specific to, and optimised for, each individual patient. Traditional population based cell studies suppress the influence of outlier cells that are frequently those of most clinical relevance. Hence single-cell analysis is becoming increasingly important in understanding disease, aiding diagnosis and selecting tailored treatment; but remains the preserve of biomedical laboratories far from the patient. Current instruments depend upon cell-labelling to identify the cell type(s) of interest, which require that these be chosen a-priori and may not be those most clinically relevant. Furthermore, cell-labelling is fundamentally subjective, requiring highly-skilled operators to decide upon the validity of each and every test. Therefore, new test methods need to be developed to enable the widespread adoption of single-cell analysis. The passive electrical properties of biological cells are known to be indicative of the specific cell type, but no technology has demonstrated their comprehensive measurement within a mass-manufacturable device. This work aims to show that biologically meaningful information can be obtained in the form of identifiable “cell signatures” through broadband frequency measurements spanning 100 kHz to 100 MHz that exploit the properties of differential electric fields. This hypothesis is tested through the design, implementation and experimental testing of a dedicated microsystem that integrates two novel designs of electrical sensor within a standard, mass-manufacturable Complementary Metal-Oxide Semiconductor microelectronics technology. One sensor measures the absolute electrical environment above a single sense electrode. The other measures the difference in electrical environment between a pair of electrodes, with view to provide information regarding the suspended cell only, through rejecting the common signal due to its suspending medium. Both sensors are shown capable of detecting individual biological cells in physiological solution, and the differential sensor capable of identifying individually-fixed red blood cells, cervical cancer HeLa cells, and three diameters of homogeneous polystyrene micro-beads of comparable size, all while suspended in physiological saline. These results confirm the hypothesis that differential electric fields provide greater distinction of suspended cells from their environment than existing electrical methods. This finding shows that electrode polarisation arising from proximity to liquids, and particularly physiological media, can be overcome through fully-differential electrical cell sensing. However, misalignment between cells and sensor electrodes limits the sensitivity achieved with the microsystem. Methods to overcome such alignment issues should be investigated in future work, along with higher frequency measurements beyond those presented here.

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Major Telecomunicações). Faculdade de Engenharia. Universidade do Porto. 2009

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Major de Telecomunicações). Faculdade de Engenharia. Universidade do Porto. 2009

A graphene field-effect-transistor (GFET) model calibrated with extracted device parameters and a commercial 65 nm silicon MOSFET model are compared with respect to their radio frequency behavior. GFETs slightly lag behind CMOS in terms of speed despite their higher mobility. This is counterintuitive, but can be explained by the effect of a strongly nonlinear voltage-dependent gate capacitance. GFETs achieve their maximum performance only for narrow ranges of V-DS and I-DS, which must be carefully considered for circuit design. For our parameter set, GFETs require at least mu = 3000 cm(2) V-1 s(-1) to achieve the same performance as 65 nm silicon MOSFETs. / <p>QC 20130115</p>

Els dispositius MEMS han demostrat la seva utilitat en un gran ventall d'aplicacions de sensat i actuació. L'extensió al domini de RF d'aquests elements mecànics són ara una de les peces clau per sistemes altament reconfigurables referències de freqüència i processadors de senyals. Aquesta tesi es centra en algunes de les aplicacions dels dispositius MEMS en el domini de RF: referències de freqüència per oscil·ladors, filtres i mescladors. Els resonadors que es presenten en aquesta tesi s'han fabricat completament en tecnologies CMOS comercials per aprofitar la integració de MEMS i circuiteria complementària i el baix cost de fabricació d'aquestes tecnologies. Diferents tipus de ressonadors MEMS s'han dissenyat i fabricat a fi d'avaluar les seves prestacions en diferents propietats. La validesa de la tècnica emprada per fabricar els MEMS en tecnologies CMOS futures s'ha demostrat fabricant i testant amb èxit resonadors MEMS en dos tecnologies diferents: de diferents fàbriques i nodes tecnològics (0.35um i 0.18um). La freqüència de ressonància d'aquests dispositius mecànics es troben a les bandes de HF i VHF. Tots aquests dispositius basats en bigues flexurals, presenten un major factor de qualitat Q que els tancs LC integrats i són a més a més sintonizables en freqüència, amb una mida inferior a la dels citats tancs LC. Els ressonadors MEMS-CMOS descrita a la tesi presenten un valor de Qxf en el rang entre 1GHz i els 10GHz mesurats a l'aire. Aquests valors es milloren mesurant al buit arribant als 100GHz, majors a qualsevol altre ressonador basat en tecnologia CMOS. Les aplicacions de mesclat i filtrat de senyals també s'estudien. Dins d'aquestes aplicacions, la meta és definir una banda passant plana combinant diferents ressonadors. El prototipus d'un filtre paral·lel basat en ponts i un amplificador diferencial CMOS monolític presenta una banda passant plana de 200kHz a una freqüència central de 21.66MHz quan es mesura a l'aire. També es demostra el filtrat emprant un únic ressonador del tipus tuning fork. Com a mesclador, és destacable la possibilitat de convertir a alta i baixa senyals de 1GHz amb un ressonador de 22MHz Com a oscil·ladors monolítics, es mostra un oscil·lador operatiu per tensions DC baixes (<5V), gràcies a la reducció del gap del ressonador. L'oscil·lador basat en un tuning fork aconsegueix valors de soroll de fase de -87dBc/Hz@10kHz i -98.7dBc/Hz@100kHz, millor que altres oscil·ladors CMOS monolític reportats. / MEMS devices demonstrated a wide range of sensing and actuation applications. These mechanical elements present nowadays extension to the RF world as key elements for highly reconfigurable systems, frequency references and signal processors. This thesis focuses on some of the applications of MEMS devices in the RF domain: frequency references for oscillators, filters and mixers. The resonators presented in this thesis are completely fabricated in commercial CMOS technologies to take profit of monolithic MEMS and complementary circuitry integration and low cost fabrication inherent of these technologies. Several kinds of MEMS resonators (clamped-clamped beams, free-free beams and double ended tuning forks) were designed and fabricated to evaluate their performance according to different properties. Two different CMOS technologies, from two different foundries and also different technological node (0.35um and 0.18um) were successfully used to validate the monolithic fabrication approach on future CMOS technologies. The resonance frequencies of these resonators are located on the HF and VHF range. All these devices, based on flexural beams, show superior Q than integrated LC tanks and are also tunable. Moreover, their size is significatively lower than the one of the aforementioned LC tanks. The CMOS-MEMS resonators reported in this thesis show a Qxf value in the range between 1GHz and 10GHz in air and these values are further improved in vacuum up to 100GHz, higher than any other reported resonator based on CMOS technology. Filtering and mixing applications were also studied. The goal in these applications was to define a flat band-pass combining different resonators. A prototype of parallel filter was measured using two CC-beams and a monolithic CMOS differential amplifier. The filter shows a flat bandpass up to 200kHz in air at a center frequency of 21.66MHz. Filtering with a single resonator was also demostrated with a DETF. A mixer based on a 22MHz CC-beam resonator was able to up and downconvert a signal from/to 1GHz. Monolithic oscillators with MEMS elements as frequency references have shown oscillation with a reduced applied DC voltage (<5V) thanks to the reduction of the gap. The DETF based oscillator shows good phase noise performance of -87dBc/Hz@10kHz and -98.7dBc/Hz@100kHz better than previously reported monolithic oscillators whereas operating at a lower DC voltage.

The objective of the proposed research is to extend the battery life in cellular handsets by improving the transmitter efficiency. Bandwidth efficient modulation formats, such as W-CDMA, encode much of the information in amplitude modulation. Therefore, linear transmitters must be used so as not to increase transmission errors, and cause interference in adjacent bands. Various engineering trade-offs were examined to find a suitable transmitter architecture for W-CDMA. Dynamic biasing of the transmitter power amplifier (PA) provides a simple way to improve efficiency for applications that require highly linear amplification. The envelope elimination and restoration (EER) PA or EER-based polar-modulated PA is an attractive solution since it has potential to achieve very high efficiency with high linearity. However, the major impediment to EER implementation has been the lack of power-efficient dynamic power supply circuits that can operate with sufficient modulation bandwidth, and simultaneously achieve the required modulation linearity. This work proposes several solutions to this problem. First, a dynamic supply circuit using delta modulation was designed and implemented. An open-loop EER PA with 48% peak efficiency was constructed and tested with a cellular band IS-95 CDMA signal with a bandwidth of 1.25 MHz. The low switching loss by using a delta modulator made the implementation of a wideband dynamic biasing circuit possible. Second, a dynamic supply circuit using dual-phase PWM was designed and implemented to achieve wider bandwidth, lower noise, and higher efficiency. An open-loop EER PA was implemented with the dynamic supply IC. A digital gain compensation scheme was developed to further increase bandwidth and linearity. This enables a dynamic supply circuit with lower switching frequency to have larger usable bandwidth with little increased power consumption. A cellular band W-CDMA voice signal was used to evaluate the performance of the overall PA. The PA achieved 50% efficiency while passing all required spectral specifications of W-CDMA standard. To increase the inherent low dynamic range of an EER PA, a dual-mode power amplifier combining an EER PA and power-level tracking PA was proposed. This work will contribute to the development of high efficiency, small-sized multi-mode linear PAs for battery-operated wireless handheld devices.

Ultra-Wideband (UWB) technology has become one of the hottest topics in wireless communications, for it provides cost-effective, power-efficient, high bandwidth solution for relaying data in the immediate area (up to 10 meters). This work demonstrates two different solutions for the RF front-end designs in the UWB receivers, one is distributed topology, and the other is based on traditional lumped element topology. The distributed amplifier is one of the attractive candidates for UWB Low Noise Amplifier (LNA). The design, analysis and operation of the distributed amplifiers will be presented. A distributed amplifier is designed with Coplanar Waveguide (CPW) transmission lines in 0.25-μm CMOS process for time domain UWB applications. New design techniques and new topologies are developed to enhance the power-efficiency and reduce the chip area. A compact and high performance distributed amplifier with Patterned Grounded Shield (PGS) inductors is developed in 0.25-μm CMOS process. The amplifier has a measurement result of 7.2dB gain, 4.2-6dB noise figure, and less than -10dB return loss through 0-11GHz. A new distributed amplifier implementing cascade common source gain cells is presented in 0.18-μm CMOS. The new amplifier demonstrates a high gain of 16dB at a power consumption of 100mW, and a gain of 10dB at a low power consumption of 19mW. A UWB LNA utilizing resistive shunt feedback technique is reported in 0.18-μm CMOS process. The measurement results of the UWB LNA demonstrate a maximum gain of 10.5dB and a noise figure of 3.3-4.5dB from 3-9.5GHz, while only consuming 9mW power. Based on the distributed amplifier and resistive shunt-feedback amplifier designs, two UWB RF front-ends are developed. One is a distributed LNA-Mixer. Unlike the conventional distributed mixer, which can only deliver low gain and high noise figure, the proposed distributed LNA-Mixer demonstrates 12-14dB gain ,4-5dB noise figure and higher than 10dB return loss at RF and LO ports over 2-16GHz. To overcome the power consumption and chip area problems encountered in distributed circuits, another UWB RF front-end is also designed with lumped elements. This front-end, employing resistive shunt-feedback technique into its LNA design, can achieve a gain of 12dB and noise figure of 8-10dB through 3-10GHz, the return loss of less than -10dB from 3- 10GHz at RF port, and less than -7dB at LO port, while only consuming 25mA current from 1.8V voltage supply.

There has been an exponential increase in the performance of silicon based semiconductor devices in the past few decades. This improvement has mainly been due to dimensional scaling of the MOSFET. However, physical constraints limit the continued growth in device performance. To overcome this problem, novel channel materials are being developed to enhance carrier mobility and hence increase device performance. This work explores a novel semiconducting alloy - Silicon-tin (SiSn) as a channel material for CMOS applications. For the first time ever, MOS devices using SiSn as channel material have been demonstrated. A low cost, scalable and manufacturable process for obtaining SiSn by diffusion of Sn into silicon has also been explored. The channel material thus obtained is electrically characterized by fabricating MOSCAPs and Mesa-shaped MOSFETs. The SiSn devices have been compared to similar devices fabricated using silicon as channel material.