La demande croissante de toujours plus de débit pour les télécommunications entraine une augmentation de la fréquence de fonctionnement des liaisons séries. Cette demande se retrouve aussi dans les systèmes embarqués du fait de l'augmentation des performances des composants et périphériques. Afin de s'assurer que le train de données est bien réceptionné, un circuit de restitution d'horloge et de données est placé avant tout traitement du coté du récepteur. Dans ce contexte, les activités de recherche présentées dans cette thèse se concentrent sur la conception d'une CDR (Clock and Data Recovery). Nous détaillerons le comparateur de phase qui joue un rôle critique dans un tel système. Cette thèse présente un comparateur de phase ayant comme avantage d'avoir une mode de fenêtrage et une fréquence de fonctionnement réduite. La topologie spéciale utilisée pour la CDR est décrite, et la théorie relative aux oscillateurs verrouillés en injection est expliquée. L'essentiel du travail de recherche s'est concentrée sur la conception et le layout d'une restitution d'horloge dans le domaine millimétrique, à 80 Gbps. Pour cela plusieurs prototypes ont été réalisés en technologie BiCMOS 130 nm de STMicrolectronics. / The increasing bandwidth demand for telecommunication leads to an important rise of serial link operating frequencies. This demand is also present in embedded systems with the growth of devices and peripherals performances. To ensure the data stream is well recovered, a clock and data recovery (CDR) circuit is placed before any logical blocks on the receiver side. The research activities presented in this thesis are related to the design of such a CDR. The phase detector plays a critical role in the CDR circuit and is specially studied. This thesis presents a phase comparator that provides an enhancement by introducing a windowed mode and reducing its operating frequency. The used CDR has a special topology, which is described, and the injection locked oscillator theory is explained. Most of the research of this study has focused on the design and layout of a 80 Gbps CDR. Several prototypes are realized in 130 nm SiGe process from STMicroelectronics.

Circuits to extend operation data-rate of a optical receiver is investigated in the dissertation. A new input-stage topology for a transimpedance amplifier (TIA) is designed to achieve 50% higher data-rate is presented, and a new architecture for clock recovery is proposed for 50% higher clock rate. The TIA is based on a gm-boosted common-gate amplifier. The input-resistance is reduced by modifying a transistor at input stage to be diode-connected, and therefore lowers R-C time constant at the input and yielding higher input pole frequency. It also allows removal of input inductor, which reduces design complexity. The proposed circuit was designed and fabricated in 32 nm CMOS SOI technology. Compared to TIAs which mostly operates at 50 GHz bandwidth or lower, the presented TIA stage achieves bandwidth of 74 GHz and gain of 37 dBohms while dissipating 16.5 mW under 1.5V supply voltage. For the clock recovery circuit, a phase-locked loop is designed consisting of a frequency doubling mechanism, a mixer-based phase detector and a 40 GHz voltage-controlled oscillator. The proposed frequency doubling mechanism is an all-analog architecture instead of the conventional digital XOR gate approach. This approach realizes clock-rate of 40 GHz, which is at least 50% higher than other circuits with mixer-based phase detector. Implemented with 0.13-μm CMOS technology, the clock recovery circuit presents peak-to-peak clock jitter of 2.38 ps while consuming 112 mW from a 1.8 V supply. / Ph. D.

This thesis explores the clock and data recovery (CDR) for the high-speed blind-sampling ADC-based receivers. This exploration results in two new CDR architectures that reduce the receiver complexity and save the ADC power and area compared to the previous work. The two proposed CDR architectures constitute the primary contributions of this thesis. The first proposed architecture, a 2x feed-forward CDR architecture, eliminates the interpolating feedback loop, used in the previously reported CDRs, in order to reduce the CDR circuit complexity. Instead of the feedback loop, the proposed architecture uses a feed-forward topology to recover the phase and data directly from the blind digital samples of the received signal. The 2x feed-forward CDR architecture was implemented and characterized in a 5 Gb/s receiver test-chip in 65 nm CMOS. The test-chip measurements confirm that the CDR successfully recovers the data with bit error rate (BER) < 10e-12 in the presence of jitter. The second proposed architecture, a fractional-sampling-rate (FSR) CDR architecture, reduces the receiver sampling rate from the typical integer rate of 2x the baud rate to a fractional rate between 2x and 1x in order to reduce the ADC power and area. This architecture employs the feed-forward topology of the first contribution of this thesis to recover the phase and data from the fractionally-spaced digital samples of the signal. To verify the proposed FSR CDR architecture, a 1.45x receiver test-chip was implemented and characterized in 65 nm CMOS. This test-chip recovers 6.875 Gb/s data from the ADC samples taken at 10 GS/s. The measurements confirm a successful data recovery in the presence of jitter with BER < 10e-12. With sampling at 1.45x, the FSR CDR architecture reduces the ADC power and area by 27.3% compared to the 2x feed-forward CDR architecture, while the overall receiver power and area are reduced by 12.5%.

This thesis explores the clock and data recovery (CDR) for the high-speed blind-sampling ADC-based receivers. This exploration results in two new CDR architectures that reduce the receiver complexity and save the ADC power and area compared to the previous work. The two proposed CDR architectures constitute the primary contributions of this thesis. The first proposed architecture, a 2x feed-forward CDR architecture, eliminates the interpolating feedback loop, used in the previously reported CDRs, in order to reduce the CDR circuit complexity. Instead of the feedback loop, the proposed architecture uses a feed-forward topology to recover the phase and data directly from the blind digital samples of the received signal. The 2x feed-forward CDR architecture was implemented and characterized in a 5 Gb/s receiver test-chip in 65 nm CMOS. The test-chip measurements confirm that the CDR successfully recovers the data with bit error rate (BER) < 10e-12 in the presence of jitter. The second proposed architecture, a fractional-sampling-rate (FSR) CDR architecture, reduces the receiver sampling rate from the typical integer rate of 2x the baud rate to a fractional rate between 2x and 1x in order to reduce the ADC power and area. This architecture employs the feed-forward topology of the first contribution of this thesis to recover the phase and data from the fractionally-spaced digital samples of the signal. To verify the proposed FSR CDR architecture, a 1.45x receiver test-chip was implemented and characterized in 65 nm CMOS. This test-chip recovers 6.875 Gb/s data from the ADC samples taken at 10 GS/s. The measurements confirm a successful data recovery in the presence of jitter with BER < 10e-12. With sampling at 1.45x, the FSR CDR architecture reduces the ADC power and area by 27.3% compared to the 2x feed-forward CDR architecture, while the overall receiver power and area are reduced by 12.5%.

Data transfer rates of communication systems continue to rise fueled by aggressive demand for voice, video and Internet data. Device scaling enabled by modern lithography has paved way for System-on-Chip solutions integrating compute intensive digital signal processing. This trend coupled with demand for low power, battery-operated consumer devices offers extensive research opportunities in analog and mixed-signal designs that enable modern communication systems. The first part of the research deals with broadband wireless receivers. With an objective to gain insight, we quantify the impact of undesired out-band blockers on analog baseband in a broadband radio. We present a systematic evaluation of the dynamic range requirements at the baseband and A/D conversion boundary. A prototype UHF receiver designed using RFCMOS 0.18[mu]m technology to support this research integrates a hybrid continuous- and discrete-time analog baseband along with the RF front-end. The chip consumes 120mW from a 1.8V/2.5V dual supply and achieves a noise figure of 7.9dB, an IIP3 of -8dBm (+2dbm) at maximum gain (at 9dB RF attenuation). High linearity active RC filters are indispensable in wireless radios. A novel feed-forward OTA applicable to active RC filters in analog baseband is presented. Simulation results from the chip prototype designed in RFCMOS 0.18[mu]m technology show an improvement in the out-band linearity performance that translates to increased dynamic range in the presence of strong adjacent blockers. The second part of the research presents an adaptive clock-recovery system suitable for high-speed wireline transceivers. The main objective is to improve the jitter-tracking and jitter-filtering trade-off in serial link clock-recovery applications. A digital state-machine that enables the proposed mixed-signal adaptation solution to achieve this objective is presented. The advantages of the proposed mixed-signal solution operating at 10Gb/s are supported by experimental results from the prototype in RFCMOS 0.18[mu]m technology.

As the volume of data processed by computers and telecommunication devices rapidly increases, high speed serial link has been challenged to maximize its I/O bandwidth with limited resources of channels and semiconductor devices. This trend requires designers’ relentless effort for innovations. The innovations are required not only at system level but also at sub-system and circuit level. This dissertation discusses two important topics regarding high speed serial links: Clock and Data Recovery (CDR) and Current Mode Logic (CML). This dissertation proposes a mixed-mode adaptive loop gain Bang-Bang CDR. The proposed CDR enhances jitter performances even if jitter spectrum information is limited a priori. By exploiting the inherent hard-nonlinearity of the Bang-Bang Phase Detector (BBPD), the CDR loop gain is adaptively adjusted based on a posteriori jitter spectrum estimation. Maximizing advantages of analog and digital implementations, the proposed mixed-mode technique achieves PVT insensitive and power efficient loop gain adaptation for high speed applications even in limited ft technologies. A modified CML D-latch improves CDR input sensitivity and BBPD performance. A folded-cascode-based Charge Pump (CP) is proposed to minimize CP latency. The effectiveness of the proposed techniques was experimentally demonstrated by various jitter performance tests. This dissertation also presents a process-variation-resilient CML. A typical CML requires over-design to meet the specification over the wide range of process parameter variations. To address this issue, the proposed CML employs a time-reference-based adaptive biasing chain with replica load. It adjusts a variable load resistor to simultaneously regulate time-constant, voltage swing, level-shifting and DC gain. The performance of the high speed building blocks such as Bang-Bang Phase Detectors, frequency dividers and PRBS generators can be more accurately regulated with the proposed CML approach. The prototype is fabricated to experimentally compare the process-variation-induced performance degradation between the conventional and the proposed CML. Compared to the conventional CML, the proposed architecture significantly reduces the performance degradation on divider self-oscillation frequency, PRBS generator speed and PRBS output jitters over the process-variation with only <3% additional power dissipation.

Traditional implementations of optical receivers are designed to operate with external photodetectors or require integration in a hybrid technology. By integrating a CMOS photodetector monolithically with an optical receiver, it can lead to the advantage of speed performance and cost. This dissertation describes the implementation of a photodetector in CMOS technology and the design of an optical receiver front-end and a clock and data recovery system. The CMOS detector converts the light input into an electrical signal, which is then amplified by the receiver front-end. The recovery system subsequently processes the amplified signal to extract the clock signal and retime the data. An inductive peaking methodology has been used extensively in the front-end. It allows the accomplishment of a necessary gain to compensate for an underperformed responsivity from the photodetector. The recovery circuits based on a nonlinear circuit technique were designed to detect the timing information contained in the data input. The clock and data recovery system consists of two units viz. a frequency-locked loop and a phase-locked loop. The frequency-locked loop adjusts the oscillator’s frequency to the vicinity of data rate before phase locking takes place. The phase-locked loop detects the relative locations between the data transition and the clock edge. It then synchronises the input data to the clock signal generated by the oscillator. A system level simulation was performed and it was found to function correctly and to comply with the gigabit fibre channel specification. / Dissertation (MEng (Micro-Electronics))--University of Pretoria, 2007. / Electrical, Electronic and Computer Engineering / unrestricted

This thesis proposes a decision-feedback equalizer (DFE) scheme for blind ADC-based receivers to overcome the challenges introduced by blind sampling. It presents the design, simulation, and implementation of a 5Gb/s speculative DFE for a 2x blind ADC-based receiver. The complete receiver, including the ADC, the DFE, and a 2x blind clock and data recovery (CDR) circuit, is implemented in Fujitsu’s 65-nm CMOS process. Measurements of the fabricated test-chip confirm 5Gb/s data recovery with bit error rate (BER) less than 1e−12 in the presence of a test channel introducing 13.3dB of attenuation at the Nyquist frequency of 2.5GHz. The receiver tolerates 0.24UIpp of high-frequency sinusoidal jitter (SJ) in this case. Without the DFE, the BER exceeds 1e−8 even when no SJ is applied.

This thesis presents the design, implementation, and fabrication of an analog front-end (AFE) targeting 2x blind ADC-based receivers. The front-end consists of a combination of an anti-aliasing filter (AAF) and a 2-tap feed-forward equalizer (FFE) (AAF/FFE), the required clock generation circuitry (Ck Gen), 4 time-interleaved 4-b ADCs, and DeMUX. The contributions of this design are the AAF/FFE and the Ck Gen. The overall front-end optimizes the channel/filter characteristics for data-rates of 2-10 Gb/s. The bandwidth of the AAF is scalable with the data-rate and the analog 2-tap feed-forward equalizer (FFE) is designed without the need for noise-sensitive analog delay cells. The test-chip is implemented in 65-nm CMOS and the AAF/FFE occupies 152×86 μm2 and consumes 2.4 mW at 10 Gb/s. Measured frequency responses at data-rates of 10, 5, and 2 Gb/s confirm the scalability of the front-end bandwidth. FFE achieves 11 dB of high-frequency boost at 10 Gb/s.

This thesis proposes a decision-feedback equalizer (DFE) scheme for blind ADC-based receivers to overcome the challenges introduced by blind sampling. It presents the design, simulation, and implementation of a 5Gb/s speculative DFE for a 2x blind ADC-based receiver. The complete receiver, including the ADC, the DFE, and a 2x blind clock and data recovery (CDR) circuit, is implemented in Fujitsu’s 65-nm CMOS process. Measurements of the fabricated test-chip confirm 5Gb/s data recovery with bit error rate (BER) less than 1e−12 in the presence of a test channel introducing 13.3dB of attenuation at the Nyquist frequency of 2.5GHz. The receiver tolerates 0.24UIpp of high-frequency sinusoidal jitter (SJ) in this case. Without the DFE, the BER exceeds 1e−8 even when no SJ is applied.