Impacto e compensação da largura de banda vídeo em amplificadores de potência de elevado rendimento

The aim of this work is to determine, quantify and model the performance degradation of wideband power amplifiers when subject to concurrent multiband excitation, with a particular focus on the average efficiency variation. The origins of this degradation are traced to two main transistor properties: the output baseband current generation by the nonlinear transconductance, and the input baseband current generation by the nonlinear gate-source capacitance variation. Each mechanism is analised separately, first by providing a qualitative and intuitive explanation of the processes that lead to the observed efficiency degradation, and then by deriving models that allow the prediction of the average efficiency dependence with the input signal bandwidth. The resulting knowledge was used to improve matching network design, in order to optimize baseband impedance terminations and prevent the efficiency degradation. The derived models were experimentally validated with several PA prototypes implemented with Gallium Nitride HEMT devices, using both conventional and optimized baseband impedance matching networks, achieving over 400MHz instantaneous bandwidth with uncompromised efficiency. The consolidation of the wideband degradation mechanisms described in this work are an important step for modelling and design of wideband, high-efficiency power amplifiers in current and future concurrent multi-band communication systems.O objetivo deste trabalho é determinar, quantificar e modelar a degradação do desempenho de amplificadores de banda-larga quando submetidos a excitação multi-banda concorrente, com particular ênfase na variação do rendimento energético. As origens desta degradação são devidas a duas das principais propriedades do transístor: a geração de corrente em banda-base na saída pela variação não-linear da transcondutância, e a geração de corrente de banda-base na entrada pela variação não-linear da capacidade interna porta-fonte. Cada um destes mecanismos é analisado isoladamente, primeiro por uma explicação qualitativa e intuitiva dos processos que levam à degradação de eficiência observada e, em seguida, através da derivação de modelos que permitem a previsão da degradação do rendimento médio em função da largura de banda do sinal de entrada. O conhecimento resultante foi utilizado para melhorar o desenvolvimento de malhas de adaptação, por forma a otimizar as terminações de impedância em banda-base e prevenir a degradação do rendimento. Os modelos desenvolvidos foram validados experimentalmente em vários amplificadores de potência implementados com transístores de tecnologia GaN HEMT, utilizando malhas de adaptação convencionais e otimizadas, onde se obteve 400MHz de largura de banda instantânea sem degradação do rendimento. A consolidação dos mecanismos de degradação descritos neste trabalho são um importante passo para a modelação e projeto de amplificadores de elevado rendimento e largura-debanda para os sistemas de comunicação multi-banda concorrente convencionais e do futuro.Programa Doutoral em Engenharia Eletrotécnic

High-efficiency and broadband PA design considering the impact of device knee voltage

The new 5G communications system requires the power amplifier (PA) circuits to be operated with high efficiency at both peak and back-off power within a broad RF and video bandwidth. The new 5G signal has an increased complexity for the modulation scheme, resulting into a high signal peak-to-average ratio (PAPR). In consequence, the performances of the PA are limited. This thesis addresses the design analysis for high efficiency and broadband PAs based on harmonic tuned continuous class-F (CCF) mode by including the I-V knee interaction. Most PA modes and waveform engineering techniques to elevate PA performances are ignoring the practical knee voltage. This thesis addresses the new performances of the CCF mode when the I-V knee interaction from the waveforms in considered. The current waveforms are a function of voltage waveforms, that clipped and generates harmonics when voltage waveform is expanded into knee region, as the device is operated with compression. The new performances of the CCF mode does not follow the ideal theoretical performances, instead, changes along the phase of 2nd harmonic impedance termination. The interaction of the current and voltage (I-V) knee on the waveforms of CCF mode allowing load-pull emulation to be calculated, where the α in CCF mode is the function of 2nd harmonic impedances termination in the actual device’s load-pull technique. In this research, the load-pull emulation is performed only through mathematical calculation in MATLAB by manipulating the equation of drain current and voltage waveforms. Output power and efficiency contours are generated from load-pull emulation for CCF mode, that have almost identical behaviour with the actual device model and measurement, when the non-linear I-V knee interaction is considered. This emulation also investigates the efficiency of the device at the output power back-off (OPBO) range, with the sweep of the α parameter. The investigation of the new CCF mode with I-V knee interaction is used as guide for a PA design with restriction of the phase of 2nd harmonic impedances termination to keep the efficiency high across wide bandwidth. The video-bandwidth (VBW) performances for the PA can be extended using a baseband termination circuit at the device’s output to shift the resonance frequency coming from the bias network and the device’s output parasitic capacitance. The VBW enhancement is crucial in the 5G communication system where it is expected to operate up to 800 MHz, or even beyond this frequency, for the instantaneous bandwidth. Analyses are made on the components used in the baseband termination circuit in this thesis, where the VBW can be further extended by having the highest value of the shunt capacitor that is placed close to the device, with the lowest equivalent series inductance. This configuration shifted the resonance frequency and reduced the impedances seen by the device output on the matching and bias network. All the methods described in this thesis are adapted to design and investigate the performances of compact PA with integrated matching and baseband termination network. This PA is aimed to operate with high efficiency at the 50 Ω load impedances and at load modulated output power back-off across a wide-bandwidth. A CW simulation tests are used to evaluate the performances of the PA at peak power, while 2 tones signal with sweep frequency spacing is used to evaluate the VBW performances

Reconfigurable high efficiency class-F power amplifier using CMOS-MEMS technology

The increasing demand for wireless products to be part of our daily lives brings the need for longer battery lifetime, smaller size and lower cost. To increase battery lifetime, high efficiency power amplifiers (PAs) are needed; To make them smaller, integration or reconfiguration is aimed and to reach lower costs, technologies such as CMOS are final goals. However integration of high efficiency PA in CMOS is challenging due to the technology limitations which restricts the achievable output power and efficiency of the PA. In order to bring solutions for the above-mentioned requirements, in this thesis novel reconfigurable class-F PAs, frequency-reconfiguration, CMOS integration, impedance-reconfiguration and CMOS-MEMS implementation are addressed. Starting with a single frequency operation, a novel class-F PA for mobile applications is proposed in which with a proper harmonic tuning structure the need for extra filtering sections is eliminated, achieving an excellent harmonic-suppression level. This topology uses transmission lines and is developed to cover multiple frequency bands for purpose of global coverage with aim of size reduction. Three novel frequency reconfigurable PAs are proposed using MEMS and semiconductor switches to accomplish class-F operation at two frequencies. The main novelty of this structure is that the reconfiguration is done not only at fundamental frequency but also at harmonics with reduced number of tuning elements. Moreover, by proper placement of the switches in the stubs, the maximum voltages over the switches are minimized. The proposed structure overcomes the narrow band performance of class-F, giving an efficiency more than 60% over a 225 MHz and 175 MHz bandwidth at 900 MHz and 1800 MHz respectively. Measurement results showed high performance at both frequency bands giving 69.5% and 57.9% PAE at 900 MHz and 1800 MHz respectively. A novel CMOS class-F PA is proposed that controls up to the 3rd harmonic and can adapt to load variations due to the effect of the human body on mobile phones. It enables the integration of the PA with other devices in a single chip leading to better matching, higher performance, lower cost and smaller size. In addition, it achieves load impedance reconfigurability by using impedance tuner in its output network and by proper tuning of the network, effects of load variation on the performance are compensated. Two designs at 2.4 GHz have been done using either MOS varactors or MEMS variable capacitors as tuning devices. The design using MOS varactors show a maximum measured values of 26% PAE and 19.2 dBm output power for 50 load. For loads other than 50 ohm an improvement of 15% for PAE and 4.4 dB for output power is obtained in comparison to non-tuned one. The second design is done using MEMS variable capacitors integrated in CMOS technology through a mask-less post-processing technique. Simulations results for 50 ohm load show a peak PAE of 32.8% while delivering 18.2 dBm output power.La creixent demanda de productes sense fils en la nostra vida diària requereix dispositius de menor grandària, menor cost i amb una gran autonomia. Per reduir la mida i augmentar l'autonomia és necessari utilitzar sistemes integrats multiestàndard o reconfigurables, amb amplificadors de RF d'alta eficiència, mentre que per reduir el cost, és preferible utilitzar tecnologies econòmiques com CMOS. No obstant això, la integració en CMOS d'amplificadors de radiofreqüència, i en especial, d'alta eficiència, és un repte a causa de les limitacions de la tecnologia que restringeixen la potència de sortida realitzable i l'eficiència de l'amplificador. En aquesta tesi es tracten els diferents reptes anteriorment esmentats, proposant una nova topologia d'amplificador classe-F amb reconfiguració de freqüència, i proposant la integració d'un amplificador classe-F que s¿adapta a impedància de càrrega variable, implementat en CMOS i CMOS-MEMS. Inicialment en la tesi es proposa una topologia d'amplificador classe-F en què, gràcies a una estructura adequada a la xarxa d'adaptació, s¿elimina la necessitat de filtrat extra, aconseguint un nivell de rebuig d'harmònics excel·lent. La topologia proposada utilitza línies de transmissió i s'ha desenvolupat per dues bandes diferents, amb el disseny orientat a implementar un sistema reconfigurable. S'han aconseguit PAE de l'ordre del 80 % amb potències properes a 10 W. Un cop descrita i analitzada la topologia, s'han proposat tres amplificadors reconfigurables per doble banda freqüencial. Per a la reconfiguració s'han utilitzat MEMS i commutadors basats en semiconductors. L'estructura proposada permet la reconfiguració no només en la freqüència fonamental sinó també en els harmònics, però mantenint un nombre reduït d'elements d'ajust. A més, gràcies a l'adequada col·locació dels commutadors en les línies de transmissió, s'ha minimitzat la tensió màxima en els mateixos. Així mateix, l'estructura proposada evita la característica de banda estreta a classe-F, proporcionant una eficiència superior al 60% en unes amplades de banda de 225 MHz i de 175 MHz, per a les banda de 900 MHz i 1800 MHz respectivament. En aquestes bandes, la PAE màxima mesurada és del 69,5% i del 57,9% respectivament. Finalment, s'ha proposat un amplificador integrat en CMOS, classe-F amb control fins al tercer harmònic. L'amplificador proposat incorpora un sintonitzador a la sortida, podent així adaptar-se a variacions d'impedància de càrrega, típiques en dispositius sense fil (WLAN), degudes a l'efecte del cos humà sobre l'antena. La implementació en CMOS permet la integració de l'amplificador de potència amb altres dispositius en un únic xip, donant lloc a una millor adaptació, millor rendiment, menor cost i menor grandària del sistema. A més, gràcies a l'adaptació a les variacions de la impedància de càrrega, permet mantenir el rendiment en diferents rangs d'operació. S'han realitzat dos dissenys de l'amplificador a 2,4 GHz, un basat en varactors MOS i un altre en condensadors variables MEMS. El disseny que utilitza varactors MOS mostra una PAE màxima del 26% i una potència de 19,2 dBm per a càrrega adaptada 50 ohm. Per altres càrregues, gràcies a l'adaptació d'impedància, s'obté una millora de PAE del 15% i de 4,4 dB en potència de sortida. El disseny utilitzant condensadors MEMS s'integra en CMOS gràcies a post-processat sense màscares addicionals. Els resultats de simulació per a 50 ohm mostren una PAE del 32,8% per 18,2 dBm de potència de sortid

CMOS MESFET Cascode Amplifiers for RFIC Applications

abstract: There is an ever-increasing demand for higher bandwidth and data rate ensuing from exploding number of radio frequency integrated systems and devices. As stated in the Shannon-Hartley theorem, the maximum achievable data rate of a communication channel is linearly proportional to the system bandwidth. This is the main driving force behind pushing wireless systems towards millimeter-wave frequency range, where larger bandwidth is available at a higher carrier frequency. Observing the Moor’s law, highly scaled complementary metal–oxide–semiconductor (CMOS) technologies provide fast transistors with a high unity power gain frequency which enables operating at millimeter-wave frequency range. CMOS is the compelling choice for digital and signal processing modules which concurrently offers high computation speed, low power consumption, and mass integration at a high manufacturing yield. One of the main shortcomings of the sub-micron CMOS technologies is the low breakdown voltage of the transistors that limits the dynamic range of the radio frequency (RF) power blocks, especially with the power amplifiers. Low voltage swing restricts the achievable output power which translates into low signal to noise ratio and degraded linearity. Extensive research has been done on proposing new design and IC fabrication techniques with the goal of generating higher output power in CMOS technology. The prominent drawbacks of these solutions are an increased die area, higher cost per design, and lower overall efficiency due to lossy passive components. In this dissertation, CMOS compatible metal–semiconductor field-effect transistor (MESFETs) are utilized to put forward a new solution to enhance the power amplifier’s breakdown voltage, gain and maximum output power. Requiring no change to the conventional CMOS process flow, this low cost approach allows direct incorporation of high voltage power MESFETs into silicon. High voltage MESFETs were employed in a cascode structure to push the amplifier’s cutoff frequency and unity power gain frequency to the 5G and K-band frequency range. This dissertation begins with CMOS compatible MESFET modeling and fabrication steps, and culminates in the discussion of amplifier design and optimization methodology, parasitic de-embedding steps, simulation and measurement results, and high resistivity RF substrate characterization.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Integrated Filters and Couplers for Next Generation Wireless Tranceivers

The main focus of this thesis is to investigate the critical nonlinear distortion issues affecting RF/Microwave components such as power amplifiers (PA) and develop new and improved solutions that will improve efficiency and linearity of next generation RF/Microwave mobile wireless communication systems. This research involves evaluating the nonlinear distortions in PA for different analog and digital signals which have been a major concern. The second harmonic injection technique is explored and used to effectively suppress nonlinear distortions. This method consists of simultaneously feeding back the second harmonics at the output of the power amplifier (PA) into the input of the PA. Simulated and measured results show improved linearity results. However, for increasing frequency bandwidth, the suppression abilities reduced which is a limitation for 4G LTE and 5G networks that require larger bandwidth (above 5 MHz). This thesis explores creative ways to deal with this major drawback. The injection technique was modified with the aid of a well-designed band-stop filter. The compact narrowband notch filter designed was able to suppress nonlinear distortions very effectively when used before the PA. The notch filter is also integrated in the injection technique for LTE carrier aggregation (CA) with multiple carriers and significant improvement in nonlinear distortion performance was observed. This thesis also considers maximizing efficiency alongside with improved linearity performance. To improve on the efficiency performance of the PA, the balanced PA configuration was investigated. However, another major challenge was that the couplers used in this configuration are very large in size at the desired operating frequency. In this thesis, this problem was solved by designing a compact branch line coupler. The novel coupler was simulated, fabricated and measured with performance comparable to its conventional equivalent and the coupler achieved substantial size reduction over others. The coupler is implemented in the balanced PA configuration giving improved input and output matching abilities. The proposed balanced PA is also implemented in 4G LTE and 5G wireless transmitters. This thesis provides simulation and measured results for all balanced PA cases with substantial efficiency and linearity improvements observed even for higher bandwidths (above 5 MHz). Additionally, the coupler is successfully integrated with rectifiers for improved energy harvesting performance and gave improved RF-dc conversion efficienc

Spin Detection, Amplification, and Microwave Squeezing with Kinetic Inductance Parametric Amplifiers

Superconducting parametric amplifiers operating at microwave frequencies have become an essential component in circuit quantum electrodynamics experiments. They are used to amplify signals at the single-photon level, while adding only the minimum amount of noise required by quantum mechanics. To achieve gain, energy is transferred from a pump to the signal through a non-linear interaction. A common strategy to enhance this process is to place the non-linearity inside a high quality factor resonator, but so far, quantum limited amplifiers of this type have only been demonstrated from designs that utilize Josephson junctions. Here we demonstrate the Kinetic Inductance Parametric Amplifier (KIPA), a three-wave mixing resonant parametric amplifier that exploits the kinetic inductance intrinsic to thin films of disordered superconductors. We then utilize the KIPA for measurements of 209Bi spin ensembles in Si. First, we show that a KIPA can serve simultaneously as a high quality factor resonator for pulsed electron spin resonance measurements and as a low-noise parametric amplifier. Using this dual-functionality, we enhance the signal to noise ratio of our measurements by more than a factor of seven and ultimately achieve a measurement sensitivity of 2.4 x 10^3 spins. Then we show that pushed to the high-gain limit, KIPAs can serve as a `click'-detector for microwave wave packets by utilizing a hysteretic transition to a self-oscillating state. We calibrate the detector's sensitivity to be 3.7 zJ and then apply it to measurements of electron spin resonance. Finally, we demonstrate the suitability of the KIPA for generating squeezed vacuum states. Using a cryogenic noise source, we first confirm the KIPAs in our experiment to be quantum limited amplifiers. Then, using two KIPAs arranged in series, we make direct measurements of vacuum noise squeezing, where we generate itinerant squeezed states with minimum uncertainty more than 7 dB below the standard quantum limit. High quality factor resonators have also recently been used to achieve strong coupling between the spins of single electrons in gate-defined quantum dots and microwave photons. We present our efforts to achieve the equivalent goal for the 31P flip-flop qubit. In doing so, we confirm previous predictions that the superconducting material MoRe would produce magnetic field-resilient resonators and demonstrate that it has kinetic inductance equivalent to the popular material NbTiN