Enhancing Digital Controllability in Wideband RF Transceiver Front-Ends for FTTx Applications

Enhancing the digital controllability of wideband RF transceiver front-ends helps in widening the range of operating conditions and applications in which such systems can be employed. Technology limitations and design challenges often constrain the extensive adoption of digital controllability in RF front-ends. This work focuses on three major aspects associated with the design and implementation of a digitally controllable RF transceiver front-end for enhanced digital control. Firstly, the influence of the choice of semiconductor technology for a system-on-chip integration of digital gain control circuits are investigated. The digital control of gain is achieved by utilizing step attenuators that consist of cascaded switched attenuation stages. A design methodology is presented to evaluate the influence of the chosen technology on the performance of the three conventionally used switched attenuator topologies for desired attenuation levels, and the constraints that the technology suitable for high amplification places on the attenuator performance are examined. Secondly, a novel approach to the integrated implementation of gain slope equalization is presented, and the suitability of the proposed approach for integration within the RF front-end is verified. Thirdly, a sensitivity-aware implementation of a peak power detector is presented. The increased employment of digital gain control also increases the requirements on the sensitivity of the power detector employed for adaptive power and gain control. The design, implementation, and measurement results of a state-of-the-art wideband power detector with high sensitivity and large dynamic range are presented. The design is optimized to provide a large offset cancellation range, and the influence of offset cancellation circuits on the sensitivity of the power detector is studied. Moreover, design considerations for high sensitivity performance of the power detector are investigated, and the noise contributions from individual sub-circuits are evaluated. Finally, a wideband RF transceiver front-end is realized using a commercially available SiGe BiCMOS technology to demonstrate the enhancements in the digital controllability of the system. The RF front-end has a bandwidth of 500 MHz to 2.5 GHz, an input dynamic range of 20 dB, a digital gain control range larger than 30 dB, a digital gain slope equalization range from 1.49 dB/GHz to 3.78 dB/GHz, and employs a power detector with a sensitivity of -56 dBm and dynamic range of 64 dB. The digital control in the RF front-end is implemented using an on-chip serial-parallel-interface (SPI) that is controlled by an external micro-controller. A prototype implementation of the RF front-end system is presented as part of an RFIC intended for use in optical transceiver modules for fiber-to-the-x applications

Direct sampling receivers for broadband communications

Today everything tends to be connected in the Internet of Things (IoT) universe, where a broad variety of communication standards and technologies are used for those connected devices. It is always a dream to design a Software-Defined Radio (SDR) supporting different standards solely based on the software configuration. As integrated-circuit (IC) manufacture and design advance, a partial of SDR can be realized. This thesis investigates one of the most important parts in a SDR: the analog design of a direct sampling (DS) receiver, which mainly consists of a broadband RF front end and a wideband ADC. Especially, a DS receiver shows a great flexibility and efficiency for the simultaneous reception of multiple channels comparing with the traditional parallelism of superheterodyne structure. The research contributions of this work include (1) demonstration and comparative analysis of two new architectures of broadband RFPGAs: voltage-mode: RFPGA-V and current-mode: RFPGA-I. RFPGA-V and RFPGA-I utilize an innovative interpolation method and current steering approach, respectively, to achieve a fine gain step of 0.25-dB over 40-dB gain range for several GHz frequency range. Besides, with innovative design, no off-chip inductor is needed for the both RFPGAs. (2) The design of a 5-GS/s 10b time-interleaved SAR. The ADC power efficiency is significantly improved by many design techniques: the low-energy CDAC switching scheme, optimized input common-mode voltage for comparator, optimal reduced radix-2 capacitor ratio for low-power reference buffers and higher conversion speed, etc. The lane-to-lane mismatches in a time-interleave ADC are minimized by using optimal floor plan and then are calibrated digitally. Three prototypes: the broadband RF front ends with RFPGA-V, the broadband RF front ends with RFPGA-I and a 5-GHz ADC, are fabricated to verify the proposed ideas in 28nm CMOS technology.Electrical and Computer Engineerin

A 6-bit 2GS/s CMOS Time-Interleaved ADC for Analysis of Mixed-Signal Calibration Techniques

A 6-bit 2-GS/s time interleaved (TI) successive approximation register (SAR) analog-to-digital converter (ADC) is designed and fabricated in a 0.13 μm CMOS process. The architecture uses 8 time-interleaved track-and-hold amplifiers (THA), and 16 SARADC’s. Thechipincludes (i) a programmable delay cell array to adjust the interleaved sampling phase, and (ii) a 12 Gbps low voltage differential signaling (LVDS) interface. These blocks make the fabricated ADC an excellent platform to evaluate mixed-signal calibration techniques, which are of great interest for application in high-speed optical systems. Measurements of the fabricated ADC show 33.9 dB of peak signal-to-noise-and-distortion ratio (SNDR) and 192 mW of power consumption at 1.2 Vhttp://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=6820267Fil: Reyes, Benjamín. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina.Fil: Tealdi, Lucas. Fundación Fulgor; Argentina.Fil: Paulina, German. Fundación Fulgor; Argentina.Fil: Labat, Emanuel. Fundación Fulgor; Argentina.Fil: Sánchez, Raúl. Fundación Fulgor; Argentina.Fil: Mandolesi, Pablo. Universidad Nacional del Sur. Grupo de Investigación en Sistemas Electrónicos y Electromecatrónicos (GISEE). Laboratorio de Micro y Nano Electrónica (LMNE); Argentina.Fil: Hueda, Mario. Universidad Nacional de Córdoba. Consejo Nacional de Investigaciones Científicas y Técnicas. Laboratorio de Comunicaciones Digitales; Argentina.Fil: Reyes, Benjamín. Consejo Nacional de Investigaciones Científicas y Técnicas. Laboratorio de Comunicaciones Digitales; Argentina.Telecomunicacione

Low-Overhead Built-In Self-Test for Advanced RF Transceiver Architectures

abstract: Due to high level of integration in RF System on Chip (SOC), the test access points are limited to the baseband and RF inputs/outputs of the system. This limited access poses a big challenge particularly for advanced RF architectures where calibration of internal parameters is necessary and ensure proper operation. Therefore low-overhead built-in Self-Test (BIST) solution for advanced RF transceiver is proposed. In this dissertation. Firstly, comprehensive BIST solution for RF polar transceivers using on-chip resources is presented. In the receiver, phase and gain mismatches degrade sensitivity and error vector magnitude (EVM). In the transmitter, delay skew between the envelope and phase signals and the finite envelope bandwidth can create intermodulation distortion (IMD) that leads to violation of spectral mask requirements. Characterization and calibration of these parameters with analytical model would reduce the test time and cost considerably. Hence, a technique to measure and calibrate impairments of the polar transceiver in the loop-back mode is proposed. Secondly, robust amplitude measurement technique for RF BIST application and BIST circuits for loop-back connection are discussed. Test techniques using analytical model are explained and BIST circuits are introduced. Next, a self-compensating built-in self-test solution for RF Phased Array Mismatch is proposed. In the proposed method, a sinusoidal test signal with unknown amplitude is applied to the inputs of two adjacent phased array elements and measure the baseband output signal after down-conversion. Mathematical modeling of the circuit impairments and phased array behavior indicates that by using two distinct input amplitudes, both of which can remain unknown, it is possible to measure the important parameters of the phased array, such as gain and phase mismatch. In addition, proposed BIST system is designed and fabricated using IBM 180nm process and a prototype four-element phased-array PCB is also designed and fabricated for verifying the proposed method. Finally, process independent gain measurement via BIST/DUT co-design is explained. Design methodology how to reduce performance impact significantly is discussed. Simulation and hardware measurements results for the proposed techniques show that the proposed technique can characterize the targeted impairments accurately.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Full Duplex CMOS Transceiver with On-Chip Self-Interference Cancelation

abstract: The demand for the higher data rate in the wireless telecommunication is increasing rapidly. Providing higher data rate in cellular telecommunication systems is limited because of the limited physical resources such as telecommunication frequency channels. Besides, interference with the other users and self-interference signal in the receiver are the other challenges in increasing the bandwidth of the wireless telecommunication system. Full duplex wireless communication transmits and receives at the same time and the same frequency which was assumed impossible in the conventional wireless communication systems. Full duplex wireless communication, compared to the conventional wireless communication, doubles the channel efficiency and bandwidth. In addition, full duplex wireless communication system simplifies the reusing of the radio resources in small cells to eliminate the backhaul problem and simplifies the management of the spectrum. Finally, the full duplex telecommunication system reduces the costs of future wireless communication systems. The main challenge in the full duplex wireless is the self-interference signal at the receiver which is very large compared to the receiver noise floor and it degrades the receiver performance significantly. In this dissertation, different techniques for the antenna interface and self-interference cancellation are proposed for the wireless full duplex transceiver. These techniques are designed and implemented on CMOS technology. The measurement results show that the full duplex wireless is possible for the short range and cellular wireless communication systems.Dissertation/ThesisDoctoral Dissertation Engineering 201

Fault-tolerant design of RF front-end circuits

The continuing trends of scaling in the CMOS industry have, inevitably, been accompanied by an ever-increasing array of process faults and fabrication complexities. The relentless march towards miniaturization and massive integration, in addition to increasing operating frequencies has resulted in increasing concerns about the reliability of integrated RF front-ends. Coupled with rising cost per chip, the fault-tolerant paradigm has become pertinent in the RFIC domain. Two main reasons have contributed to the fact that fault-tolerant solutions for circuits that operate in the GHz domain have not been realized so far. First, GHz signals are extremely sensitive to higher-order effects such as stray pick-ups, interference, package & on-chip parasitics, etc. Secondly, the use of passives, especially inductors, in the feedback path poses huge area overheads, in addition to a slew of instability problems due to wide variations and soft faults. Hence traditional fault-tolerance methods used in digital and low frequency analog circuits cannot be applied in the RF domain. This work presents a unique methodology to achieve fault-tolerance in RF circuits through dynamic sensing and on-chip self-correction, along with the development of robust algorithms. This technique is minimally intrusive and is transparent during \u27normal\u27 use of the circuit. It is characterized by low area and power overheads, does not need any off-chip computing or DSP cores, and is characterized by self-correction times in the range of a few hundreds of microseconds. It compares very well with existing commercial RF test solutions that use DSP cores and require hundreds of milliseconds. The methodology is demonstrated on a LNA, since it is critical for the performance of the entire front-end. It is validated with simulation and fabrication results of the system designed in IBM 0.25 µm CMOS 6RF process

Développement d'une architecture innovante de récepteur radar à 77 GHz et démonstration en CMOS 28 nm FDSOI

Grâce à sa capacité à détecter des cibles éloignées malgré une mauvaise visibilité, le radar automobile à 77 GHz joue un rôle important dans l'aide à la conduite. L'utilisation des fréquences millimétriques offre une bonne résolution et une importante capacité d'intégration des circuits. C'est aussi un défi car il faut satisfaire un cahier des charges exigeant sur le bruit et la linéarité du récepteur. Les technologies SiGe BiCMOS ont été les premières utilisées pour la conception de récepteurs radar à 77 GHz. De bons résultats ont été obtenus en se basant sur des architectures utilisant des mélangeurs actifs. Cependant l'utilisation des technologie BiCMOS se traduisait par une consommation élevée, une faible capacité d'intégration et des coûts de production importants. Récemment, l'intégration des procédés CMOS menant à l'augmentation des fréquences de transition rend ces technologies plus attractives pour les applications nécessitant un faible coût et la cointégration de plusieurs fonctions au sein d'une même puce. La littérature sur les récepteurs radars en technologie CMOS à 77 GHz montre que les architectures inspirées par les technologies BiCMOS ne sont pas pertinentes pour cette application. Le but de cette thèse et de montrer que l'utilisation de techniques propres aux technologie CMOS comme l'échantillonnage et l'utilisation de portes logiques permet d'obtenir de très bonnes performances. Dans ce travail, deux nouvelles architectures de récepteurs radars basées sur le principe d'échantillonnage sont proposées. La première architecture est basée sur un mélangeur passif échantillonné qui permet d'obtenir un très bon compromis bruit/linéarité. La seconde exploite les propriétés des mélangeurs sous-échantillonnés afin utiliser une fréquence d'OL trois fois inférieure à la fréquence RF offrant ainsi de très intéressantes simplifications au niveau de la chaîne de distribution du signal d'OL du récepteur. Le contexte de cette étude est expliqué dans le 1er chapitre qui présente les exigences de conception liées à l'application radar et fourni une analyse de l'état de l'art des récepteurs à 77 GHZ. Le chapitre suivant décrit le principe de fonctionnement et l'implémentation d'un mélangeur échantillonné à 77 GHz en technologie CMOS 28- nm FDSOI. Une topologie de mélangeur sous-échantillonné utilisant une fréquence d'OL de 26 GHz pour convertir des signaux RF autour de 77 GHz est ensuite détaillée dans le chapitre 3. Le chapitre 4 conclut cette étude en détaillant l'intégration des mélangeurs étudiés dans les chapitres précédents avec un amplificateur faible bruit dans différents récepteurs radars. Ces architectures de récepteurs basées sur l'échantillonnage sont ensuite comparées entre elles et avec l'état de l'art montrant ainsi leurs avantages et inconvénients. Les résultats de cette comparaison confirment l'intérêt des techniques d'échantillonnage pour la conversion de fréquence dans le cadre de l'application radar.With its ability to detect distant targets under harsh visibility conditions, the 77 GHz automotive radar plays a key role in driving safety. Using mm-wave frequencies allow a good range resolution, a better circuit integration and a wide modulation bandwidth. This is also a challenge for circuit designers who must fulfill stringent requirements especially on the receiver front-end. First 77 GHz radar receivers were manufactured with SiGe BiCMOS processes benefiting from the high transition frequency and high breakdown voltage of Hetero-junction Bipolar Transistors (HBT). Good results have been achieved with active-mixer-based architectures, but these technologies suffer from high power consumptions, limited integration capacity and large production cost. More recently, the scaling down of CMOS processes (coming together with the increase of the transition frequency of the transistors) makes CMOS a good candidate for 77 GHz circuit design, especially when cost target requires single chip solutions. The literature related to CMOS radar receivers highlights that receivers based on BiCMOS architectures generally show poor performances. The aim of this work is to demonstrate that using CMOS specific technics such as sampling and the use of high-speed digital gates should enhance the performance of the receivers. In this work, two innovative radar receiver architectures based on the sampling principle are proposed. The first one shows that this principle can be extended to millimeter wave frequencies to benefit from a very good noise/linearity trade-off. While the second one uses this principle to converts a 77 GHz RF signal by using a 26 GHz LO frequency thus simplifying the LO distribution chain of the receiver. The background of this study is introduced in the chapter 1 presenting the design trade-off related to the 77 GHz radar receiver and provides a review of the existing solutions. The following chapter describes the sampling mixer principle and the implementation of a 77 GHz sampling mixer in 28-nm FDSOI CMOS technology. Then, a sub- sampling mixer topology allowing to convert an RF signal around 77 GHz using a 26 GHz LO frequency is detailed in the chapter 3. The chapter 4 draws the conclusion of this study by showing the implementation of the two proposed sampling-based mixers with a low noise amplifier in 77 GHz front ends. These receiver architectures are compared with the state of the art highlighting the strengths and weaknesses of the proposed solutions. The results of this study demonstrates that using sampling for down conversion can be convenient to address millimeter-wave frequency applications

Integrated Circuits for Medical Ultrasound Applications: Imaging and Beyond

Medical ultrasound has become a crucial part of modern society and continues to play a vital role in the diagnosis and treatment of illnesses. Over the past decades, the develop- ment of medical ultrasound has seen extraordinary progress as a result of the tremendous research advances in microelectronics, transducer technology and signal processing algorithms. How- ever, medical ultrasound still faces many challenges including power-efficient driving of transducers, low-noise recording of ultrasound echoes, effective beamforming in a non-linear, high- attenuation medium (human tissues) and reduced overall form factor. This paper provides a comprehensive review of the design of integrated circuits for medical ultrasound applications. The most important and ubiquitous modules in a medical ultrasound system are addressed, i) transducer driving circuit, ii) low- noise amplifier, iii) beamforming circuit and iv) analog-digital converter. Within each ultrasound module, some representative research highlights are described followed by a comparison of the state-of-the-art. This paper concludes with a discussion and recommendations for future research directions

Design of Adaptive Amplifiers with DC Varying Inputs

Analog amplifiers are one of the most commonly used building blocks in electronic systems. Emerging circuit technologies create new systems and also new applications for signal amplification. A conventional amplifier operates at a fixed biasing point to transfer signals varying on a fixed DC level with a constant or variable gain. In some new systems, particularly those involving sensors, the DC component of a signal to be amplified can be variable, instead of fixed. The established design procedure is not applicable for such signals. In this thesis, a design method for adaptive amplifiers is proposed. It is to design an amplifier that can adjust itself automatically to suit the DC level of the input voltage and the amplification gain is variable according to the input DC level. The amplifier is made to perform, from a small signal point view, a linear amplification with a fixed gain, but from a large signal point view, a nonlinear voltage transfer. The nonlinear character of its function makes the amplifier capable of operating with an input voltage of which the DC level can vary in a specified range and providing a gain adapting to the input DC level. The proposed method has been used to design an amplifier for a voltage signal enhancement in a wide dynamic range current-to-voltage conversion circuit. The designed amplifier has four cascading stages, i.e., three simple common source amplifier stages and one source follower. The units are tuned to perform a nonlinear voltage transfer while keeping a local linearity. These units are combined to implement the characteristics needed for the signal enhancement. The circuit has been simulated and the results demonstrated that it is able to perform the required amplification of the signal varying on different DC levels with an input-dependent gain