Systematic Comparison of HF CMOS Transconductors

Transconductors are commonly used as active elements in high-frequency (HF) filters, amplifiers, mixers, and oscillators. This paper reviews transconductor design by focusing on the V-I kernel that determines the key transconductor properties. Based on bandwidth considerations, simple V-I kernels with few or no internal nodes are preferred. In a systematic way, virtually all simple kernels published in literature are generated. This is done in two steps: 1) basic 3-terminal transconductors are covered and 2) then five different techniques to combine two of them in a composite V-I kernel. In order to compare transconductors in a fair way, a normalized signal-to-noise ratio (NSNR) is defined. The basic V-I kernels and the five classes of composite V-I kernels are then compared, leading to insight in the key mechanisms that affect NSNR. Symbolic equations are derived to estimate NSNR, while simulations with more advanced MOSFET models verify the results. The results show a strong tradeoff between NSNR and transconductance tuning range. Resistively generated MOSFETs render the best NSNR results and are robust for future technology developments

대역 외 방해신호에 내성을 가지는 광대역 수신기에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 공과대학 전기·컴퓨터공학부, 2018. 2. 남상욱.In this thesis, a study of wideband receivers as one of the practical SDR receiver implementations is presented. The out-of-band interference signal (or blocker), which is the biggest problem of the wideband receiver is investigated, and have studied how to effectively remove it. As a result of reviewing previous studies, we have developed a wideband receiver based on the current-mode receiver structure and attempted to eliminate the blocker. The contents of the step-by-step research are as follows. First, attention was paid to the linearity of a low-noise transconductance amplifier (LNTA), which is the base block of current-mode receivers. In current-mode receivers, the LNTA should have a high transconductance (Gm) value to achieve a low noise figure, but a high Gm value results in low linearity. To solve this trade-off, we proposed a linearization method of transconductors. The proposed technique eliminates the third-order intermodulation distortion (IMD3) in a feed-forward manner using two paths. A transconductor having a transconductance of 2Gm is disposed in the main path, and an amplifier having a gain of ∛2 and a Gm-sized transconductor are located in the auxiliary path. This structure allows for some fundamental signal loss but cancel the IMD3 component at the output. As a result, the entire transconductor circuit can have high linearity due to the removed IMD3 component. We have designed a reconfigurable high-pass filter using a linearized transconductor and have demonstrated its performance. The fabricated circuit achieved a high input-referred third-order intercept point(IIP3) performance of 19.4 dBm. Then, a further improved linearized transconductor is designed. Since the linearized transconductors have a high noise figure due to the additional circuitry used for linearization, we have proposed a more suitable form for application to LNTA through noise figure analysis. The improved LNTA is designed to operate in low noise mode when there is no blocker, and can be switched to operate in high linearity mode when the blocker exists. We also applied noise cancelling techniques to the receiver to improve the noise figure performance of the wideband receiver circuit. A feedback path has been added to the current-mode receiver structure consisting of the LNTA, the mixer and the baseband transimpedance amplifier (TIA), and the noise signal can be detected using this path. This feedback path also maintains the input matching of the receiver to 50 Ω in a wide bandwidth. By adding an auxiliary path to the receiver, the in-band signal is amplified and the detected noise is removed from the baseband. The completed circuit exhibited wideband performance from 0.025 GHz to 2 GHz and IIP3 performance of -6.9 dBm in the high linearity mode. Finally, we designed a double noise-cancelling wideband receiver circuit by improving the performance of a wideband receiver with high immunity to blocker signals. In previous receivers, the LNTA was operated in two modes depending on the situation. In the improved receiver, the Gm ratio of the linearized LNTA was changed and the RF noise-cancelling technique was applied. The input matching and noise cancelling scheme introduced in the previous circuit was also applied and a wideband receiver circuit was designed to perform double noise-cancelling. As a result, the linearization and noise-cancellation of LNTA could be achieved at the same time, and the completed receiver circuit showed high IIP3 performance of 5 dBm with minimum noise figure of 1.4 dB. In conclusion, this thesis proposed a linearization technique for transconductor circuit and designed a wideband receiver based on current-mode receiver. The designed receiver circuit experimentally verified that it has low noise figure performance and high IIP3 performance and is tolerant to out-of-band blocker signals.Chapter 1. Introduction 1 1.1. Motivation of Wideband Receiver Architecture 2 1.2. Challenges in Designing Wideband Receiver 7 1.3. Prior Researches 13 1.3.1. N-Path Filter 14 1.3.2. Feed-Forward Blocker Filtering 16 1.3.3. Current-Mode Receiver 18 1.4. Research Objectives and Thesis Organization 22 Chapter 2. Transconductor Linearization Technique and Design of Tunable High-pass Filter 24 2.1. Transconductor Linearization Technique 27 2.2. Design of Tunable High-pass Filter 36 2.3. Measurement Results 41 2.4. Conclusions 46 Chapter 3. Wideband Noise-Cancelling Receiver Front-End Using Linearized Transconductor 47 3.1. Low-Noise Transconductance Amplifier Based on Linearized Transconductor 49 3.2. Wideband Noise-Cancelling Receiver Architecture 58 3.3. Measurement Results 64 3.4. Conclusions 70 Chapter 4. Blocker-Tolerant Wideband Double Noise-Cancelling Receiver Front-End 71 4.1. Linearized Noise-Cancelling Low-Noise Transconductance Amplifier 73 4.2. Wideband Double Noise-Cancelling Receiver Front-End 83 4.3. Measurement Results 90 4.4. Conclusions 97 Chapter 5. Conclusions 98 Bibliography 102 Abstract in Korean 112Docto

Development of Robust Analog and Mixed-Signal Circuits in the Presence of Process- Voltage-Temperature Variations

Continued improvements of transceiver systems-on-a-chip play a key role in the advancement of mobile telecommunication products as well as wireless systems in biomedical and remote sensing applications. This dissertation addresses the problems of escalating CMOS process variability and system complexity that diminish the reliability and testability of integrated systems, especially relating to the analog and mixed-signal blocks. The proposed design techniques and circuit-level attributes are aligned with current built-in testing and self-calibration trends for integrated transceivers. In this work, the main focus is on enhancing the performances of analog and mixed-signal blocks with digitally adjustable elements as well as with automatic analog tuning circuits, which are experimentally applied to conventional blocks in the receiver path in order to demonstrate the concepts. The use of digitally controllable elements to compensate for variations is exemplified with two circuits. First, a distortion cancellation method for baseband operational transconductance amplifiers is proposed that enables a third-order intermodulation (IM3) improvement of up to 22dB. Fabricated in a 0.13µm CMOS process with 1.2V supply, a transconductance-capacitor lowpass filter with the linearized amplifiers has a measured IM3 below -70dB (with 0.2V peak-to-peak input signal) and 54.5dB dynamic range over its 195MHz bandwidth. The second circuit is a 3-bit two-step quantizer with adjustable reference levels, which was designed and fabricated in 0.18µm CMOS technology as part of a continuous-time SigmaDelta analog-to-digital converter system. With 5mV resolution at a 400MHz sampling frequency, the quantizer's static power dissipation is 24mW and its die area is 0.4mm^2. An alternative to electrical power detectors is introduced by outlining a strategy for built-in testing of analog circuits with on-chip temperature sensors. Comparisons of an amplifier's measurement results at 1GHz with the measured DC voltage output of an on-chip temperature sensor show that the amplifier's power dissipation can be monitored and its 1-dB compression point can be estimated with less than 1dB error. The sensor has a tunable sensitivity up to 200mV/mW, a power detection range measured up to 16mW, and it occupies a die area of 0.012mm^2 in standard 0.18µm CMOS technology. Finally, an analog calibration technique is discussed to lessen the mismatch between transistors in the differential high-frequency signal path of analog CMOS circuits. The proposed methodology involves auxiliary transistors that sense the existing mismatch as part of a feedback loop for error minimization. It was assessed by performing statistical Monte Carlo simulations of a differential amplifier and a double-balanced mixer designed in CMOS technologies

High-Bandwidth Voltage-Controlled Oscillator based architectures for Analog-to-Digital Conversion

The purpose of this thesis is the proposal and implementation of data conversion open-loop architectures based on voltage-controlled oscillators (VCOs) built with ring oscillators (RO-based ADCs), suitable for highly digital designs, scalable to the newest complementary metal-oxide-semiconductor (CMOS) nodes. The scaling of the design technologies into the nanometer range imposes the reduction of the supply voltage towards small and power-efficient architectures, leading to lower voltage overhead of the transistors. Additionally, phenomena like a lower intrinsic gain, inherent noise, and parasitic effects (mismatch between devices and PVT variations) make the design of classic structures for ADCs more challenging. In recent years, time-encoded A/D conversion has gained relevant popularity due to the possibility of being implemented with mostly digital structures. Within this trend, VCOs designed with ring oscillator based topologies have emerged as promising candidates for the conception of new digitization techniques. RO-based data converters show excellent scalability and sensitivity, apart from some other desirable properties, such as inherent quantization noise shaping and implicit anti-aliasing filtering. However, their nonlinearity and the limited time delay achievable in a simple NOT gate drastically limits the resolution of the converter, especially if we focus on wide-band A/D conversion. This thesis proposes new ways to alleviate these issues. Firstly, circuit-based techniques to compensate for the nonlinearity of the ring oscillator are proposed and compared to equivalent state-of-the-art solutions. The proposals are designed and simulated in a 65-nm CMOS node for open-loop RO-based ADC architectures. One of the techniques is also validated experimentally through a prototype. Secondly, new ways to artificially increase the effective oscillation frequency are introduced and validated by simulations. Finally, new approaches to shape the quantization noise and filter the output spectrum of a RO-based ADC are proposed theoretically. In particular, a quadrature RO-based band-pass ADC and a power-efficient Nyquist A/D converter are proposed and validated by simulations. All the techniques proposed in this work are especially devoted for highbandwidth applications, such as Internet-of-Things (IoT) nodes or maximally digital radio receivers. Nevertheless, their field of application is not restricted to them, and could be extended to others like biomedical instrumentation or sensing.El propósito de esta tesis doctoral es la propuesta y la implementación de arquitecturas de conversión de datos basadas en osciladores en anillos, compatibles con diseños mayoritariamente digitales, escalables en los procesos CMOS de fabricación más modernos donde las estructuras digitales se ven favorecidas. La miniaturización de las tecnologías CMOS de diseño lleva consigo la reducción de la tensión de alimentación para el desarrollo de arquitecturas pequeñas y eficientes en potencia. Esto reduce significativamente la disponibilidad de tensión para saturar transistores, lo que añadido a una ganancia cada vez menor de los mismos, ruido y efectos parásitos como el “mismatch” y las variaciones de proceso, tensión y temperatura han llevado a que sea cada vez más complejo el diseño de estructuras analógicas eficientes. Durante los últimos años la conversión A/D basada en codificación temporal ha ganado gran popularidad dado que permite la implementación de estructuras mayoritariamente digitales. Como parte de esta evolución, los osciladores controlados por tensión diseñados con topologías de oscilador en anillo han surgido como un candidato prometedor para la concepción de nuevas técnicas de digitalización. Los convertidores de datos basados en osciladores en anillo son extremadamente sensibles (variación de frecuencia con respecto a la señal de entrada) así como escalables, además de otras propiedades muy atractivas, como el conformado espectral de ruido de cuantificación y el filtrado “anti-aliasing”. Sin embargo, su respuesta no lineal y el limitado tiempo de retraso alcanzable por una compuerta NOT restringen la resolución del conversor, especialmente para conversión A/D en aplicaciones de elevado ancho de banda. Esta tesis doctoral propone nuevas técnicas para aliviar este tipo de problemas. En primer lugar, se proponen técnicas basadas en circuito para compensar el efecto de la no linealidad en los osciladores en anillo, y se comparan con soluciones equivalentes ya publicadas. Las propuestas se diseñan y simulan en tecnología CMOS de 65 nm para arquitecturas en lazo abierto. Una de estas técnicas presentadas es también validada experimentalmente a través de un prototipo. En segundo lugar, se introducen y validan por simulación varias formas de incrementar artificialmente la frecuencia de oscilación efectiva. Para finalizar, se proponen teóricamente dos enfoques para configurar nuevas formas de conformación del ruido de cuantificación y filtrado del espectro de salida de los datos digitales. En particular, son propuestos y validados por simulación un ADC pasobanda en cuadratura de fase y un ADC de Nyquist de gran eficiencia en potencia. Todas las técnicas propuestas en este trabajo están destinadas especialmente para aplicaciones de alto ancho de banda, tales como módulos para el Internet de las cosas o receptores de radiofrecuencia mayoritariamente digitales. A pesar de ello, son extrapolables también a otros campos como el de la instrumentación biomédica o el de la medición de señales mediante sensores.Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidente: Juan Pablo Alegre Pérez.- Secretario: Celia López Ongil.- Vocal: Fernando Cardes Garcí

Advances in Solid State Circuit Technologies

This book brings together contributions from experts in the fields to describe the current status of important topics in solid-state circuit technologies. It consists of 20 chapters which are grouped under the following categories: general information, circuits and devices, materials, and characterization techniques. These chapters have been written by renowned experts in the respective fields making this book valuable to the integrated circuits and materials science communities. It is intended for a diverse readership including electrical engineers and material scientists in the industry and academic institutions. Readers will be able to familiarize themselves with the latest technologies in the various fields

Architectures and Circuit Techniques for High-Performance Field-Programmable CMOS Software Defined Radios

Next-generation wireless communication systems put more stringent performance requirements on the wireless RF receiver circuits. Sensitivity, linearity, bandwidth and power consumption are some of the most important specifications that often face tightly coupled tradeoffs between them. To increase the data throughput, a large number of fragmented spectrums are being introduced to the wireless communication standards. Carrier aggregation technology needs concurrent communication across several non-contiguous frequency bands, which results in a rapidly growing number of band combinations. Supporting all the frequency bands and their aggregation combinations increases the complexity of the RF receivers. Highly flexible software defined radio (SDR) is a promising technology to address these applications scenarios with lower complexity by relaxing the specifications of the RF filters or eliminating them. However, there are still many technology challenges with both the receiver architecture and the circuit implementations. The performance requirements of the receivers can also vary across different application scenario and RF environments. Field-programmable dynamic performance tradeoff can potentially reduce the power consumption of the receiver. In this dissertation, we address the performance enhancement challenges in the wideband SDRs by innovations at both the circuit building block level and the receiver architecture level. A series of research projects are conducted to push the state-of-the-art performance envelope and add features such as field-programmable performance tradeoff and concurrent reception. The projects originate from the concept of thermal noise canceling techniques and further enhance the RF performance and add features for more capable SDR receivers. Four generations of prototype LNA or receiver chips are designed, and each of them pushes at least one aspect of the RF performance such as bandwidth, linearity, and NF. A noise-canceling distributed LNA breaks the tradeoff between NF and RF bandwidth by introducing microwave circuit techniques from the distributed amplifiers. The LNA architecture uniquely provides ultra high bandwidth and low NF at low frequencies. A family of field-programmable LNA realized field-programmable performance tradeoff with current-reuse programmable transconductance cells. Interferer-reflecting loops can be applied around the LNAs to improve their input linearity by rejecting the out-of-band interferers with a wideband low in- put impedance. A low noise transconductance amplifier (LNTA) that operates in class-AB-C is invented to can handle rail-to-rail out-of-band blocker without saturation. Class-AB and class-C transconductors form a composite amplifier to increase the linear range of the input voltage. A new antenna interface named frequency-translational quadrature-hybrid (FTQH) breaks the input impedance matching requirement of the LNAs by introducing quadrature hybrid couplers to the CMOS RFIC design. The FTQH receiver achieves wideband sub-1dB NF and supports scalable massive frequency-agile concurrent reception

Low Power Filtering Techniques for Wideband and Wireless Applications

This dissertation presents design and implementation of continuous time analog filters for two specific applications: wideband analog systems such as disk drive channel and low-power wireless applications. Specific focus has been techniques that reduce the power requirements of the overall system either through improvement in architecture or efficiency of the analog building blocks. The first problem that this dissertation addresses is the implementation of wideband filters with high equalization gain. An efficient architecture that realizes equalization zeros by combining available transfer functions associated with a biquadratic cell is proposed. A 330MHz, 5th order Gm-C lowpass Butterworth filter with 24dB boost is designed using the proposed architecture. The prototype fabricated in standard 0.35um CMOS process shows -41dB of IM3 for 250mV peak to peak swing with 8.6mW/pole of power dissipation. Also, an LC prototype implemented using similar architecture is discussed in brief. It is shown that, for practical range of frequency and SNR, LC based design is more power efficient than a Gm-C one, though at the cost of much larger area. Secondly, a complementary current mirror based building block is proposed, which pushes the limits imposed by conventional transconductors on the powerefficiency of Gm-C filters. Signal processing through complementary devices provides good linearity and Gm/Id efficiency and is shown to improve power efficiency by nearly 7 times. A current-mode 4th order Butterworth filter is designed, in 0.13um UMC technology, using the proposed building. It provides 54.2dB IM3 and 55dB SNR in 1.3GHz bandwidth while consuming as low as 24mW of power. All CMOS filter realization occupies a relatively small area and is well suited for integration in deep submicron technologies. Thirdly, a 20MHz, 68dB dynamic range active RC filter is presented. This filter is designed for a ten bit continuous time sigma delta ADC architecture developed specifically for fine-line CMOS technologies. Inverter based amplification and a common mode feedback for such amplifiers are discussed. The filter consumes 5mW of power and occupies an area of 0.07 mm2

Circuits and architectures for the implementation of broadband channelizers

Broadband spectrum channelizers sub-divide a broadband input spectrum into multiple sub-bands, where each of the sub-bands is down-converted and further processed at baseband. These designs can help to relax baseband design specifications. For example, baseband analog-to-digital converters (ADCs) that process the sub-bands at the channelizer output see only a part of the incident spectrum. The sampling frequency, and potentially the dynamic range of each sub-band ADC can thus be relaxed, compared to the case where a single ADC is used to digitize the full spectrum. Spectrum channelizers can be used for multiple applications. These designs can be used as general-purpose hybrid frequency-and-time domain ADCs. The designs can also be employed for spectrum analysis, as well as for wireless communication applications. In this dissertation, two circuit techniques for the implementation of broadband channelizers are proposed. A frequency-translational feedback-based interference canceler for attenuating large interferers at the output of the front-end low-noise amplifier (LNA) of a channelizer is shown. The design uses harmonic rejection mixers (HRMs) with embedded frequency synthesis capability. While channelizers reduce the bandwidth and potentially the dynamic range of the baseband ADCs, the analog signal paths in the channelizer can be broadband. Consequently the dynamic range required of the analog section of a sub-band path can still be limited by the presence of large signals in other, potentially distant parts of the spectrum. The demonstrated design is useful for relaxing the dynamic range requirement of the analog section that follows the front-end LNA in a channelizer. Reduction of the harmonic response and the frequency synthesizer tuning-range is also achieved in this design. Second, a two-stage HRM is proposed which shares the same bias current between the RF and baseband stages, thus reducing the power consumption. Issues arising from bias-current sharing, such as the 1/f noise of the RF stage and potential degradation of the 2nd harmonic response are identified, and circuit techniques are introduced to mitigate these potential degradation mechanisms.Electrical and Computer Engineerin