Design and implementation of generalized topologies of time-interleaved variable bandpass Σ−Δ modulators

In this thesis, novel analog-to-digital and digital-to-analog generalized time-interleaved variable bandpass sigma-delta modulators are designed, analysed, evaluated and implemented that are suitable for high performance data conversion for a broad-spectrum of applications. These generalized time-interleaved variable bandpass sigma-delta modulators can perform noise-shaping for any centre frequency from DC to Nyquist. The proposed topologies are well-suited for Butterworth, Chebyshev, inverse-Chebyshev and elliptical filters, where designers have the flexibility of specifying the centre frequency, bandwidth as well as the passband and stopband attenuation parameters. The application of the time-interleaving approach, in combination with these bandpass loop-filters, not only overcomes the limitations that are associated with conventional and mid-band resonator-based bandpass sigma-delta modulators, but also offers an elegant means to increase the conversion bandwidth, thereby relaxing the need to use faster or higher-order sigma-delta modulators. A step-by-step design technique has been developed for the design of time-interleaved variable bandpass sigma-delta modulators. Using this technique, an assortment of lower- and higher-order single- and multi-path generalized A/D variable bandpass sigma-delta modulators were designed, evaluated and compared in terms of their signal-to-noise ratios, hardware complexity, stability, tonality and sensitivity for ideal and non-ideal topologies. Extensive behavioural-level simulations verified that one of the proposed topologies not only used fewer coefficients but also exhibited greater robustness to non-idealties. Furthermore, second-, fourth- and sixth-order single- and multi-path digital variable bandpass digital sigma-delta modulators are designed using this technique. The mathematical modelling and evaluation of tones caused by the finite wordlengths of these digital multi-path sigmadelta modulators, when excited by sinusoidal input signals, are also derived from first principles and verified using simulation and experimental results. The fourth-order digital variable-band sigma-delta modulator topologies are implemented in VHDL and synthesized on Xilinx® SpartanTM-3 Development Kit using fixed-point arithmetic. Circuit outputs were taken via RS232 connection provided on the FPGA board and evaluated using MATLAB routines developed by the author. These routines included the decimation process as well. The experiments undertaken by the author further validated the design methodology presented in the work. In addition, a novel tunable and reconfigurable second-order variable bandpass sigma-delta modulator has been designed and evaluated at the behavioural-level. This topology offers a flexible set of choices for designers and can operate either in single- or dual-mode enabling multi-band implementations on a single digital variable bandpass sigma-delta modulator. This work is also supported by a novel user-friendly design and evaluation tool that has been developed in MATLAB/Simulink that can speed-up the design, evaluation and comparison of analog and digital single-stage and time-interleaved variable bandpass sigma-delta modulators. This tool enables the user to specify the conversion type, topology, loop-filter type, path number and oversampling ratio

Architecture d'amplificateur faible bruit large bande multistandard avec gestion optimale de la consommation

In recent years, the sustainable development, especially the control of the electrical appliances' consumption, has became a major issue in our society. The optimisation of each electrical devices' energy is needed to reduce the consumption of home appliances. The objective of this thesis is the realization of a low noise amplifier (LNA) that offers two modes of operation depending on the quality of the received signal: a high performance mode and a low consumption mode.In order to meet the problem related to multistandard systems, the distributed architecture is selected for low noise amplifier. Indeed, it is known for its wide bandwidth and tunable power gain. A design method is proposed, which is based on GaAs technology of TriQuint Semiconductor Texas foundry. The LNA's high performance mode measurement results is at the level of the state of the art. For the low consumption mode, LNA shows good performance while reducing power consumption by 91%.Finally, an innovative reconfiguration strategy is defined. It's applied to a homodyne receiver based on the integration of our LNA. It reduces significantely the receiver's consumption in case where the received power allows the receiver operates in low power mode (constraint of the Bit Error Rate (BER) is verified). Considering each received power is equiprobable, our reconfigurable receiver saves consumption by 77% compared to a conventional receiver that has a single mode (high performance mode).Ces dernières années, le développement durable, notamment le contrôle de la consommation de nos appareils électriques, est devenu un enjeu majeur de notre société. L'essor de la domotique associé à cette problématique implique la nécessité d'optimiser le bilan énergétique de chaque dispositif électrique. L'objectif de cette thèse est la réalisation d'un amplificateur faible bruit (LNA) qui propose deux modes de fonctionnement suivant la qualité du signal reçu: un mode haute performance et un mode basse consommation.Afin de satisfaire la problématique liée aux systèmes multistandard, l'architecture sélectionnée pour l'amplificateur faible bruit est la topologie distribuée. En effet, elle est connue pour ses performances en terme de bande passante et permet un gain en puissance accordable. Une méthode de conception est proposée, basée sur la technologie GaAs de la fonderie TriQuint Semiconducteur Texas. Les mesures réalisées sur le LNA dans sa configuration haute performance se situe au niveau de l'état de l'art. Pour le mode basse consommation, on obtient de bonnes performances tout en réduisant sa consommation de 91%.Enfin, une stratégie de reconfiguration innovante est proposée basée sur l'intégration de notre LNA dans un récepteur homodyne. Elle permet de réduire de manière significative la consommation du récepteur, dans le cas où la puissance reçue permet un fonctionnement en mode basse consommation (contraintes sur le Bit Error Rate (BER) vérifiées). En considérant chaque puissance reçue de manière équiprobable, notre récepteur reconfigurable a une consommation réduite de 77% par rapport à un récepteur classique qui possède un seul mode de fonctionnement (mode haute performance)

Quadrature sigma-delta modulators for reconfigurable A/D interface and dynamic spectrum access: analysis, design principles and digital post-processing

In the course of development of wireless communications and its modern applications, such as cloud technologies and increased consumption and sharing of multimedia, the radio spectrum has become increasingly congested. However, temporarily and spatially underused spectrum exists at the same time. For increasing the efficiency of spectrum usage, the concept of dynamic spectrum access (DSA) has been proposed. Ultimately, the DSA principle should be exploited also in cognitive radio (CR) receivers. Herein, this paradigm is approached from the receiver architecture point-of-view, considering software-defined radio (SDR) as a platform for the future DSA and CR devices. Particularly, an analog-to-digital converter (ADC) architecture exploiting quadrature ΣΔ modulator (QΣΔM) is studied in detail and proposed as a solution for the A/D interface, being identified as a performance bottleneck in SDRs. By exploiting a complex valued noise transfer function (NTF) enabled by the QΣΔM, the quantization precision of the ADC can be efficiently and flexibly focused on the frequency channels and the signals to be received and detected. At the same time, with a traditional non-noise-shaping ADC, the precision is distributed equally for the whole digitized frequency band containing also noninteresting signals. With a single QΣΔM, it is also possible to design a multiband NTF, allowing reception of multiple noncontiguous frequency channels without parallel receiver chains. Furthermore, with the help of digital control, the QΣΔM response can be reconfigured during operation. These capabilities fit in especially well with the above mentioned DSA and CR schemes, where the temporarily and spatially available channels might be scattered in frequency. From the implementation point-of-view, the effects of inherent implementation inaccuracies in the QΣΔM design need to be thoroughly understood. In this thesis, novel closed-form matrix-algebraic expressions are presented for analyzing the transfer functions of a general multistage QΣΔM with arbitrary number of arbitrary-order stages. Altogether, the signal response of an I/Q mismatched QΣΔM has four components. These are the NTF, an image noise transfer function, a signal transfer function (STF) and an image signal transfer function. The image transfer functions are provoked by the I/Q mismatches and define the frequency profile of the generated mirror-frequency interference (MFI), potentially deteriorating the quality of the received signal. This contribution of the thesis increases the understanding of different QΣΔM structures and allows the designers to study the effects of the implementation inaccuracies in closed form. In order to mitigate the MFI and improve the signal reception, a mirror-frequency rejecting STF design is proposed herein. This design is found to be effective against I/Q mismatches taking place in the feedback branches of the QΣΔM. This is shown with help of the closed-form analysis and confirmed with computer simulations on realistic reception scenarios. When a mismatch location independent MFI suppression is the desired option, it is a logical choice to do this processing in a digital domain, after the whole analog receiver front-end. However, this sets demands for the information to be digitized, i.e., the source of the MFI should be available also in the digital domain. For this purpose, a novel multiband transfer function design is proposed herein. In addition, a QΣΔM specific digital MFI compensation algorithm is developed. The compensation performance is illustrated in practical single- and multiband reception scenarios, considering desired signal bandwidths up to 20 MHz. In the multiband scenario, allowing reception and detection of noncontiguous frequency channels with a single receiver chain, the digital compensation processing is done sub-bandwise, securing reliable functionality also under strongly frequency-selective interference. In the applied single- and multistage QΣΔM architectures, the I/Q mismatches are considered in all the QΣΔM branches as well as in the preceding receiver front-end, modeling the challenging and realistic scenario where the whole receiver chain includes cascaded in-phase/quadrature (I/Q) mismatch sources. As a whole, developing digital MFI compensation is a significant step towards practical receiver implementations with QΣΔM ADCs. In consequence, this allows the exploitation of the multiband and reconfigurability properties. The proposed design can be implemented without additional analog components and is straightforwardly reconfigurable in dynamic signal conditions typical for DSA and CR systems, e.g., in case of frequency hand-off because of a primary user appearance. In addition, the digital post-compensation of the MFI eases the strict demands for the matching of the analog circuits in SDRs

CUHK electronic theses & dissertations collection

在過去的十年裡，隨著便攜式通訊，電腦與消費電子市場的快速發展，以及在超大規模積體電路中，越來越多的功能實現被轉移到數字領域中，這些都引起了人們對模數轉換器研究的極大關注。基於過採樣與量化誤差整形技術，ΣΔ模數轉換器對與類比電路中的非理想特性具有很強的容忍度。然而，爲了優化其在功耗，硅片面積與上市時間等方面的性能，ΣΔ模數轉換器的設計需要對眾多實際問題做出折中考慮。本文在不同的設計層次上提出了一些創新，包括算法，架構及電路設計，從而提升其在通訊，語音與傳感等應用領域中的性能指標。本文第一部份提出的新技術主要解決運用於低中頻無線接收器中開關電容型正交帶通ΣΔ模數轉換器的I/Q通道的不匹配問題。這些I/Q通道的不匹配將導致位於臨近信道的鏡像信號，自鏡像信號及量化噪聲混疊至輸入信道，從而降低模數轉換器的動態範圍。為此，本文提出了一種新的動態單元匹配技術與一種雙線性技術來解決上述問題。同時通過在I/Q信道間複用運算放大器，比較器與數模轉換器，芯片的面積得到了大幅的降低。基於以上技術，在0.18微米CMOS工藝上設計實現了開關電容型正交帶通ΣΔ模數轉換器的測試樣片，其鏡像抑制比可達到73dB，這是迄今為止公開發表論文中報告的最高值。在本文的第二部份，我們關注ΣΔ模數轉換器在音頻領域的應用。其對動態範圍與功耗提出的較高要求為級聯型連續時間ΣΔ模數轉換器帶來了機遇。然而，相比于單環型，級聯型連續時間ΣΔ模數轉換器對於電阻-電容時間常數的偏離及有限的運放低頻增益等非理想特性表現得更加敏感，因為這些不理想因素將影響量化噪聲在模擬與數字路徑中的精確抵消。為此，我們提出了使用脈寬調製技術來對片上的電阻-電容時間常數進行自動調整。基於脈寬調製技術，我們可以使用在離散時間電路中常用的相關雙採樣技術來提高運放的有效低頻增益。同時我們提出了一種有限運放帶寬補償技術來節省芯片的功耗。另外，本文對基於連續時間ΣΔ模數轉換器的脈寬調製技術，相關雙採用技術，反混疊濾波，噪聲與抖動效應等方面均做出了詳盡的仿真與分析。最後我們對一顆基於0.18微米CMOS工藝設計的樣片進行了測試。測試結果表明，採用本文提出的技術可以將ΣΔ模數轉換器的動態範圍提高28dB以上。本文的第三部份展示了一種可用於單端或差分電容傳感器的高精度電容-數字轉換器。在傳統的電容-數字轉換器中，由電容底板開關引入的電荷注入與數字輸出結果及被感知電容的容值有關。當被感知電容的容值變化範圍較大時，這些電荷注入將產生很大的非線性。對此本文提出了一種新的開關控制與校準算法。我們對一顆基於0.18微米CMOS工藝設計的二階電容-數字轉換器樣片進行了測試。測試結果表明，其在0.5毫秒的測試時間內可達到53.2aFrms的精度。同時本文提出的技術可以在0.5pF至3.5pF的較寬電容範圍內，使得電容-數字轉換器在單端電容傳感模式下的線性度（準確度）從9.3位提高至12.3位；在差分電容傳感模式下的線性度（準確度）從10.1位提高至13.3位。最後，本文對連接微機電電容型壓力傳感器和加速度傳感器的實際應用情境進行了測試。The rapid growth of the market for portable, battery operated systems for communications, computer and consumer electronics (3C), and the trend of moving functionality to the digital domain in very large scale integration (VLSI) systems have resulted in an enormously increasing interest in analog-to-digital converter (ADC) design.Combining both oversampling and quantization error shaping techniques, delta sigma (ΔΣ) ADCs achieve a high degree of insensitivity to analog circuit imperfections. Nevertheless, the design of CMOS ΔΣ ADCs involves a number of practical issues and trade-offs that must be taken into account in order to optimize their performance in terms of power consumption, silicon area, and time-to-market deployment. This thesis proposes a number of novel performance-enhancement techniques on different design levels, including algorithm, architecture and circuit level, for ΔΣ ADCs in various application circumstances, such as telecom, audio, sensor, and so on.First, novel techniques are proposed to mitigate I/Q mismatches in switched-capacitor quadrature bandpass Delta-Sigma modulators (DSMs) used in low-IF wireless receivers. The I/Q mismatches result in a nearby channel at the image frequency, the mirrored image of the desired signal around its center frequency (self-image) and the quantization noise to corrupt the desired signal, degrading the dynamic range of the modulator. A dynamic element matching scheme and a bilinear scheme are the proposed solution to reduce all the above-mentioned I/Q mismatch effects. Furthermore, a multiplexing scheme for the sharing of op-amps, quantizers and DACs between the I and Q channels is investigated for smaller chip area. A prototyping DSM was designed and fabricated in a 0.18 ưm CMOS, measuring an image rejection ratio of 73 dB, being the best reported.Second, a pulse-width-modulation (PWM) technique is proposed for on-chip automatic RC time constant tuning for cascaded continuous-time (CT) DSMs for audio application. The demand for high signal-to-noise-plus-distortion ratio (SNDR) and low power brings a wealth of opportunities to the CT DSMs. In CT DSMs, cascading low-order stages provides an effective way to achieve stable high-order modulation. However, compared to CT single-loop modulators, CT cascaded modulators are more sensitive to variation of RC time constant and finite dc gain of the opamps as these nonidealities affect the precise cancellation of the quantization noises between the analog and digital paths. In the CT cascaded modulator presented here, we propose to apply a PWM technique for on-chip automatic RC time constant tuning. The application of PWM in turn enables the use of the correlated double sampling (CDS) technique, which is conventionally confined to discrete-time circuits, to boost the effective dc gain. The PWM further allows the use of a finite-opamp-bandwidth compensation technique for power saving. Analysis on PWM tuning, CDS, anti-aliasing filtering, noise and jitter in the CT modulator are presented and verified with extensive simulations. Measurement results on a prototype CT cascaded 2-2 DSM in a 0.18ưm CMOS show that the proposed techniques can improve the dynamic range (DR), SNDR and spurious-free dynamic range (SFDR) of the modulator by at least 28 dB.Third, a high-precision capacitance-to-digital converter (CDC) is proposed, which can be configured to interface with single-ended or differential capacitive sensors. In the conventional CDC, charge injection from bottom-plate switches depends on the digital output and the value of the sensing capacitor. Nonlinearity is resulted especially when the varying ranging of the sensing capacitor is wide. In this thesis, new switching and calibration schemes are proposed to reduce these charge injection. A prototyping 2nd order CDC employing the proposed techniques is fabricated in a 0.18ưm CMOS process and achieves a 53.2aFrms resolution in a 0.5ms measuring time. The proposed techniques improve the CDC's linearity from 9.3 bits to 12.3 bits in the single-ended sensing mode, and from 10.1 bits to 13.3 bits in the differential sensing mode, with a wide sensing capacitor range from 0.5 to 3.5pF. The CDC is also demonstrated with real-life pressure (single-ended) and acceleration (differential) sensors.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Li, Bing.Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.Includes bibliographical references.Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Abstracts also in Chinese.Abstracts of thesis entitled: --- p.I摘 要 --- p.VContents --- p.VIIList of Figures --- p.XIList of Tables --- p.XVIAcknowledgement --- p.XVIIChapter CHAPTER 1. --- Introduction --- p.1Chapter 1.1 --- Motivation --- p.1Chapter 1.2 --- Original contributions and outline of the thesis --- p.2References --- p.1Chapter CHAPTER 2. --- A High Image-Rejection SC Quadrature Bandpass DSM for Low-IF Receivers --- p.3Chapter 2.1 --- Mismatch in Complex Gain Blocks --- p.6Chapter 2.2 --- Mismatches in QBDSM --- p.8Chapter 2.3 --- Proposed High Image-Rejection QBDSM --- p.13Chapter 2.3.1 --- Technique to remove I/Q mismatches in the first complex resonator (for P1 in Fig. 2.6) --- p.13Chapter 2.3.2 --- Technique to remove I/Q mismatches in the Feedback DAC (for B in Fig. 2.6) --- p.19Chapter 2.3.3 --- Technique to remove I/Q mismatches in the Input Coefficient (for A1 in Fig. 2.6) --- p.20Chapter 2.3.4 --- Summary and Simulation Results --- p.27Chapter 2.4 --- I/Q Multiplexing Schemes and Circuit Implementation of the QBDSM --- p.34Chapter 2.5 --- Measurement Results Analysis --- p.40Chapter 2.6 --- Conclusions --- p.47Chapter APPENDIX I: --- I/Q MISMATCHES IN LOW-IF RECEIVERS --- p.48Chapter A. --- I/Q Mismatch in Mixer --- p.48Chapter B. --- I/Q Mismatch in Polyphase Filter --- p.49Chapter C. --- I/Q Mismatch in QBDSM --- p.50Chapter D. --- I/Q Imbalance Analysis for whole receiver --- p.51Chapter APPENDIX II: --- IRR Measurement Method --- p.52References --- p.56Chapter CHAPTER 3. --- A Continuous-time Cascaded Delta-Sigma Modulator with PWM-Based Automatic RC Time Constant Tuning and Correlated Double Sampling --- p.59Chapter 3.1 --- PWM for on-chip RC Time Constant Tuning --- p.61Chapter 3.1.1 --- Integrator Gain Error --- p.64Chapter 3.1.2 --- Automatic Generation of PWM Clock --- p.65Chapter 3.1.3 --- Modulator Architecture --- p.66Chapter 3.1.4 --- Anti-aliasing Filtering --- p.68Chapter 3.1.5 --- Noise Analysis --- p.69Chapter 3.2 --- Proposed SRMC Integrator with CDS --- p.71Chapter 3.2.1 --- Analysis on the opamp gain enhancement --- p.73Chapter 3.2.2 --- Simulation Results --- p.75Chapter 3.3 --- Compensation for Finite-Opamp-Bandwidth-Induced Error --- p.76Chapter 3.3.1 --- Compensation for fininte opamp bandwidth --- p.77Chapter 3.3.2 --- Behavorial Simulation Results --- p.79Chapter 3.4 --- Jitter Analysis --- p.80Chapter 3.4.1 --- Jitter on Rising Edges --- p.81Chapter 3.4.2 --- Duty cycle jitter --- p.84Chapter 3.5 --- Prototyping Modulator Design --- p.85Chapter 3.6 --- Measurement Results --- p.89Chapter 3.7 --- Summary --- p.95References --- p.97Chapter CHAPTER 4. --- A High-Linearity Capacitance to Digital Converter with Techniques Suppressing Charge Injection from Bottom-Plate Switches --- p.105Chapter 4.1 --- Introduction --- p.105Chapter 4.2 --- Proposed CDC Switching and Calibration Schemes --- p.107Chapter 4.2.1 --- Single-Ended Sensing Mode --- p.107Chapter 4.2.2 --- Differential Sensing Mode --- p.111Chapter 4.3 --- Circuit Implementation --- p.114Chapter 4.4 --- Measurement Results --- p.117Chapter 4.5 --- Conclusion --- p.125Chapter APPENDIX: The cross section of NPN transistor in triple-well CMOS process --- p.126References --- p.127Chapter CHAPTER 5. --- Conclusions and future works --- p.129Chapter 5.1 --- Conclusions --- p.129Chapter 5.2 --- Future works --- p.130Chapter APPENDIX: --- A typical CMOS fabrication process flow (1 poly/2 M, twin well CMOS) --- p.13