Distinguished Lecturer Roster

Dynamic device, circuit, and system parameter variations degrade processor performance, energy efficiency, and yield across all market segments, ranging from small embedded cores in an Internet of Things (IoT) device to large multicore servers.  This lecture introduces the primary variations during the processor operational lifetime, including supply voltage droops, temperature changes, transistor and interconnect aging, radiation-induced soft errors, and workload fluctuations.  This presentation then describes the negative impact of these variations on processor logic and memory across a wide range of voltage and clock frequency operating conditions.  To mitigate the adverse effects from dynamic variations, this lecture presents adaptive and resilient circuits while highlighting the key design trade-offs and testing implications for product deployment.

Deep neural networks (DNNs) are commonly used in artificial intelligence (AI) processors to achieve high-accuracy recognition and prediction functions for a variety of applications. However, DNN-based AI processors using a conventional (von Neumann) architecture face challenges in long latency and high energy consumption due to memory wall issue in data movement and large-volume computation. Computing-in-memory (CIM) or process-in-memory (PIM) methods have been proposed to improve computational efficiency by enabling parallel computing within the memory macro or array, thereby reducing the instances of memory access and suppressing the volume of intermediate data to be generated. In this talk, I will review recent progress and the challenges in circuit designs of SRAM and emerging memory (STT-MRAM, ReRAM and PCM) based CIMs for AI chips.

Memory has become one of the bottlenecks in the development of IoT and wearable devices with low energy consumption. This seminar addresses trends in the development of on-chip (embedded) nonvolatile memory (NVM) for energy-efficient IoT applications. The first part of this seminar will introduce a variety of nonvolatile memory (NVM) technologies, including eFlash, resistive RAM (ReRAM), phase-change memory (PCM), and STT-MRAM. This seminar will explore the challenges and silicon verified solutions in the design of low-power and high-speed circuits for on-chip NVM macros. The 2nd part of this seminar will explore the implementation of emerging memory beyond conventional memory applications, such as nonvolatile-logics (nvLogics) and nonvolatile processors for frequent-off intelligent IoT chips.

Internet of Things (IoT) devices are rapidly becoming common place in consumer, industrial, medical, automotive applications and elsewhere. In most cases, a network of multiple devices, called nodes, each one including sensors and actuators interfacing to the physical world, communicates wirelessly with a hub/base station, which, in turn, acts as a gateway to internet. This lecture introduces to the analog/mixed-signal hardware of the IoT devices and the hub. It discusses the most common sensors and actuators used in the network nodes, their signal conditioning electronics, the data acquisition/synthesis (ADCs/DACs), and briefly touches upon the embedded digital signal processing. A brief technical introduction makes the core topics accessible to the non-experts. Some case studies illustrating the practical implementations of IoT devices to a variety of applications and real products complement the technology coverage.

Demand for ultra-wideband data acquisition and real time processing systems handling analog signals in the GHz range comes from applications in high performance instrumentation, defense and infrastructure communication systems among others. In these cases, front-end circuitry and ADCs/DACs are rapidly getting integrated together with front-end digital processing, preferably in mixed-signal CMOS systems-on-a-chip. This lecture will briefly review some of the technical challenges faced by analog designers developing such systems along with some the technologies behind that. The performance demands, coupled together with limitations of the underlying technologies such as those of nanometer CMOS processes and die packaging, require a comprehensive design approach combining circuits and architectural innovation with algorithmic techniques. This lecture introduces some of the present engineering approaches being developed to tackle such challenges. 

Many emerging applications in wearable sensors, unattended ground sensor networks, and other Internet-of-Things (IoT) devices measure signals such as human physiochemistry, ambient temperature, or the presence of intruders - all of which are signals that do not tend to vary rapidly with time. In such systems, battery life is often dominated by radios - not because of large payloads, but rather due to the constant communication of small packets in order to maintain network synchronization. This presentation will discuss how wake-up receivers (WuRXs), if designed for bandwidths that support the average expected throughput needs of a given application, can be used to dramatically reduce average power consumption in such applications. Conventional wake-up radio architectures will be reviewed and analyzed for their strengths and weaknesses, followed by detailed discussions on state-of-the-art architecture and circuit techniques that can be used to improve sensitivity and/or reduce WuRX power consumption.

Wearable devices hold considerable promise to diagnose, monitor, and treat various medical conditions and/or track the real-time status of athletes. However, most current generation wearable devices only monitor a limited number of physical and electrophysiological parameters that are, in many cases, only peripherally related to many health conditions or fitness enterprises. Furthermore, many such wearable devices are large, bulky, and rigid, thereby precluding seamless integration into daily life.

Addressing these issues requires:  1) development of new sensor technologies that provide more actionable data in thin, flexible form factors; 2) engineering of supporting electronic infrastructure to condition, digitize, and wirelessly communicate data in an extremely energy efficient manner; and 3) new data analytics to process and understand newly generated data streams. This presentation will discuss emerging sensor technologies that can non-invasively monitor physiochemistry (e.g., glucose, blood alcohol concentration, and lactate) in thin, flexible, and energy-efficiency wearable devices, alongside a brief look at what kind of analytics are necessary to parse and understand this data. We will also cover integrated circuit building blocks and architectures that make acquisition and telemetry of sensed information so energy-efficient that that they can be easily powered from new local energy sources (e.g., wearable glucose biofuel cells). Such net-zero-power operation will ultimately enable devices that are completely autonomous and invisible to the user, to the point where users are virtually unaware of their wearable devices after placement – in other words, they are “unawearable” devices. 

Small, ultra-low-power integrated circuits afford new opportunities to sense and interact with the environment in new and exciting ways – for example by probing brain matter across arbitrary 3D geometries, to sensing temperature, humidity, or chemicals within or around the human body. Over the past several years, our group has demonstrated wireless ion sensing systems than consume less than 10nW of power, wireless glucose sensing systems powered directly by glucose biofuels, single-chip mm-sized neural implants with integrated electrodes, antennas, amplifiers, digitizers, stimulators, and power/telemetry units, and ultra-small and/or ultra-low-power building blocks including reference generators, DC-DC converters, and wake-up radios. This talk will review such contributions, and the challenges and opportunities moving towards self-powered mm-sized electronic systems.

Nowadays use of millimeter-wave spectrum for wireless communication is one of the most important technologies in next generation wireless such as 5G, IEEE802.11ad/ay, IEEE802.15.3d, etc. More than 10Gbps data rate is targeted for satisfying the social demand. This talk will explain basic system-level design of millimeter-wave transceiver as well as modeling and simulation for CMOS technology. Some design examples of millimeter-wave transceivers will be also introduced, which achieves 50Gbps and 120Gbps at 60GHz and 100GHz, respectively. The talk concludes with a discussion on future directions of millimeter-wave wireless communication, based on Shannon and Friis equations.

The wireless communication is one of the key technologies for realizing the future smart society. The conventional omni-directional wireless communication using microwave has been studied so far, and now the directional wireless communication using millimeter-wave (30-300GHz) is opening a new technology field of communication. The directional wireless communication using the millimeter-wave spectrum can accept spatial co-existence and multiplexing as well as use of wide frequency bandwidth. In this presentation, a millimeter-wave CMOS phased-array transceiver design is explained about phased-array architectures, phase shifters, power amplifiers, phase/gain calibration, measurement techniques, etc. The talk concludes with a discussion on future directions of millimeter-wave wireless communication, based on Shannon and Friis equations.

In this presentation, some design techniques for fractional-N digital PLL will be introduced to improve both jitter and power consumption for low-power wireless applications. A highly-linear and low-power DTC and TDC will be presented as well as system-level optimization. An isolated constant-slope DTC realizes 10bit 0.1mW operation with 26MHz reference clock, and sub-ps INL is achieved. The DTC-based AD-PLL achieves FoM of -246dB with 0.98mW power consumption and -56dBc worst-case fractional spur. For further power saving, duty-cycled FLL, sub-sampling/sampling switching, charge-recycling DTC, and transformer-based DCO for impedance peaking will be also explained, which achieves 0.265mw power consumption with FoM of -237dB at 2.4GHz. Finally, a DPLL-based ADC and a BLE transceiver using DPLL will be introduced.

Many IoT devices, especially those with very stringent energy constraints, operate in an intermittent manner. The device wakes up infrequently, performs a burst of activity, and goes back to a sleep/inactive mode. Clocking serves multiple functions in such devices. For example, during the burst of activity, a high frequency stable crystal oscillator may be required for the operation of a wireless transceiver. Alternatively, a low frequency real time clock (RTC) that is always ON may be needed to provide crucial sleep and wakeup timer functionality. As such, overall energy consumption in such IoT devices will remain high unless the clocks themselves consume very little energy. To address this challenge, my group has developed two complementary approaches. The first technique enables rapid startup of high-Q crystal oscillators whereas the second one develops a new low power oscillator sustaining circuit. While the latter reduces the power consumption of always ON oscillators, the former allows the clocks themselves to be aggressively duty cycled along with the other circuitry. This talk will describe both techniques and how they enable low power clocking.

Clever signal processing is capable of effectively resolving many of the challenges in analog, mixed-signal, and RF IC design posed by a variety of factors such as process variability, mismatches, device non-linearity. This approach takes different forms – post-processing of ADCs, pre-processing of DACs, digital pre-distortion of PAs, mismatch shaping, intentional random dithering, calibration etc.,  – invariably exploiting the abundant digital logic capabilities of modern CMOS processes to address the aforementioned errors. We have been developing several such techniques over the years. This talk will illustrate their application to open loop phase modulators which are widely used in wideband polar and IQ modulators, and in frequency synthesis, especially in very fine CMOS processes. Achieving low EVM and/or low spurious content is of great importance to these blocks, but they invariably suffer from device mismatches. The talk will describe an array of signal processing tecniques – dither based signal conditioning, least mean square (LMS) based spur cancellation etc. -  and how they were employed to achieve a sub-100fs fractional frequency synthesizer with spurious tones as low as –100 dBc on a 2.4GHz carrier.

Sharp, programmable, linear, integrated filters are enabling components for software defined and cognitive radio applications. However, they are difficult to realize: SAW and MEMS based filters are sharp and linear but not very programmable; active filters can be sharp and programmable but are not very linear; sampled charge domain filtering is sharp and programmable but the burden of the linearity is on the front end voltage-current converter. My group has developed a unique alternative that purposefully employs periodically time-varying circuit components to realize very sharp, linear, and programmable filters for use in RF front ends. This talk will describe how even simple 1st order RC filters can be converted into very sharp filters just by making one of the components, a resistor, vary periodically with time. The talk will show how our technique goes against conventional wisdom by exploiting sampling aliases rather than struggling to suppress them prior to sampling. It will describe how we applied the technique to realize RF front-ends and spectrum scanners with some of the best reported blocker suppression, linearity, and  power consumption. 

Power electronics can be found in everything from electric vehicles and industrial motors, to laptop power adaptors that hook up to wall outlets. While silicon still dominates the power semiconductor landscape, the recent onset of wide-bandgap semiconductor (WBG) devices promises low loss, higher frequency operation of converters leading to smaller, lighter power supplies. This talk will introduce the properties of high voltage (200-1200V) Si superjunction and WBG devices and discuss their relative merits. The common power converter topologies employed in power systems will be explored along with their associated gate-drive and protection circuits.

Power electronics can be found in everything from cellphones and laptops to gasoline/electric vehicles, industrial motors and inverters that connect solar panels to the electric grid. With close to 80% of electrical energy consumption in the US expected to flow through a power converter by 2030, innovative solutions are required to tackle key issues related to conversion efficiency, power density and cost. This talk will look at the trends in power electronics across different application spaces, describe the ongoing research efforts and highlight the challenges ahead.

With the advent of IoT technology, a wide variety of electronic devices are expected to be deployed in often inaccessible places. Keeping these space-constrained devices powered up for their intended lifetimes is one of the primary concerns in the widespread adoption of this technology. In this talk, I will look at the energy needs of IoT devices, discuss the power delivery architecture and examine the possibility of self-powered operation. The talk will delve into the basics of energy harvesting sources, storage mechanisms (batteries, supercapacitors) and the associated power management circuits needed (low-power DC/DC converters, chargers) to extend the operational lifetime of IoT devices. 

Power Amplifiers are a key component for any communication system. Combining energy efficiency, output power, gain, bandwidth and linearity in one single circuit requires a profound understanding of the different circuit trade-offs, the various system requirements and the technology limitations.

In this presentation, an overview of system requirements and PA architectures will be given, highlighting the strengths and weaknesses of each solution. Power combining and device stacking, being essential techniques to achieve high output power in low-voltage technologies, will be explained in more detail. Guidelines to design broadband and linear PAs will be discussed, complemented with many examples in nanometer CMOS (65nm-28nm) and FD-SOI (22nm). Finally, various circuit techniques to reduce AM/AM and AM/PM distortion in combination with high bandwidth will be discussed in more details and explained with several examples at 28GHz and 77GHz.

Using polymers or plastics as a flexible guided dielectric channel, together with mm-wave signals and Silicon chips, was recently proposed as a complementary alternative to optical and copper. Often referred to as Polymer Microwave Fibers (PMF), the mechanical robustness and EMI tolerance are key differentiators for this communication approach. Compared to optical communication, no EO/OE conversion is needed since the mm-wave signal is directly launched into the fiber with an antenna. Furthermore, the connectors have a much higher robustness compared to optical connectors. Compared to copper wireline, far less EMI issues arise since no metal is being used in the channel.

Several demonstrators have been developed both at Universities and companies, revealing the strengths and weaknesses of this approach. This presentation will give an in-depth discussion of the topic, discuss some of the implementation challenges and will give a good understanding of the benefits and drawback of PMF, and conclude with an outlook of the future of PMF. 

The maximum operating frequency of CMOS has steadily increased over the past thirty years and extrapolations would predict THz circuits in CMOS soon. Compared to other technologies, CMOS does offer integration complexity paving the road for entire THz systems. As such, potential applications such as near-field scanning, quality control, spectroscopy and imaging could be pushed to the consumer market.

However, CMOS scaling also resulted into thinner interconnects with higher intrinsic resistance which in turn limits the maximum operating frequency. On the other hand, one could go beyond the fmax-limit by exploiting the non-linear behavior of a transistor. This concept is used already in frequency-doubler and -triplers and can be extended to entire transmitters and receivers. This talk will highlight some of these challenges when designing circuits in CMOS in the THz (300GHz-3THz) frequency band. Several examples in 40nm and 28nm CMOS at a frequency range from 200 to 620GHz will be discussed.

The ability to allow predictive, proactive, personalized and preventive and participatory healthcare analytics through complex information extraction from bio-molecular level to physiological signal monitoring can have transformative impact in healthcare in future. However, while wearable technologies are maturing with time, extracting bio-molecular information that relies on protein or genetic material is still largely centralized laboratory based. Dominated by optical-based detection technologies, these end-to-end systems are large, bulky and expensive with a complex arrangement of various optical components such as lenses, filters, collimators whose functionalities haven’t changed fundamentally in the last 50 years.

In this talk, I will present approaches that allow elimination of all external optical elements for mm-scale, fully ‘optics-free’ single chip complex optical systems. In an absolutely no-change in CMOS fabrication we will show how integrated metal interconnects in the deep sub-wavelength regime can allow highly scalable and complex nanoplasmonic elements operating in the visible range and integrated in the same substrate as the integrated electronics.  In a series of demonstrative examples ranging from mm-scale, highly multiplexed, pill-sized bio-versatile molecular sensors 100-fM levels of DNA and protein sensitivity to optical spectrometers, I will try to show how this nano-optics/electronics co-design approach opens up a new co-design space across the optical, electronic and signal processing layers. By allowing new system properties that is greater than sum of its parts, this can eventually lead to a new class of intelligent, distributed, low-power sensors for future diagnostics, health monitoring, environmental safety, food and water quality monitoring. 

Future mm-Wave systems are expected to operate in a complex and heterogeneous environment extending from the electromagnetic propagation channels right up to the network layers. As disjointed spectral bands open up across 28-100 GHz for 5G applications and beyond, spectrally agile, robust mmWave front-ends that can allow dynamic reconfiguration in large scale mmWave MIMO arrays can have a transformative impact in spectrum efficiency and deployment of such 5G systems.

While this involves a series of challenges from the antenna to the transceivers I will highlight two specific directions in this talk. These emerge through a multi-port transceiver and multi-port antenna framework that allow each element to assume properties distinct from classical array architectures. Firstly, I will discuss the challenges of enabling a transmitter front-end particularly the power amplifier for such a spectrally-agile mmWave system. I will discuss multiport architectures that can allow simultaneously broadband, high power and high back-off efficient transmitter front-end, properties that typically strongly trade-off with each other. In the next part of the talk, we will discuss how such multi-port transceivers can be co-design and co-integrated with multi-port antennas to allow such spectrally-agile architectures, In addition to extremely high bandwidths, these architectures allow element level programmability needed for multi-band periodic arrays. These include the ability to reject interferers passively directly at the element antenna surface, reconfigure individual antenna patterns, and allow frequency, spatial, pattern and polarization diversity in scalable arrays.

Silicon-based Terahertz systems is a field that is only about a decade old. In this time, we have seen a phenomenal growth of silicon systems operating at THz frequencies for a wide range of applications in sensing, imaging and communication. It can be argued that both the ‘THz gap’ and the ‘technology and applications gap’ is closing in meaningful ways in the THz range. Technologies beyond 100 GHz focusing on sensing, imaging and wireless back-haul links are getting attractive as we enter into a new area of highly dense network of autonomous systems requiring ultra-high speed and reliable links.

In order to move beyond this inflection point as Moore’s law continue to slow, I will discuss why we need to look beyond the classical ‘device’-level metrics of efficiency and sensitivity of THz sources and detectors towards holistic ‘system’ level properties such as scalability and programmability. Such properties are critically important for applications in sensing and imaging, as evidenced across sensor fusion technologies across mmWave, IR and optical frequencies. The ultimate programmability in THz sources and sensors is one that can synthesize or receive THz fields with arbitrary configuration and spectrum. In this talk, I will highlight approaches that cut across electromagnetics, circuits, systems and signal processing, to allow for such reconfigurability in THz signal synthesis and sensing, yet realized with devices that are themselves not very efficient. Incorporating, such programmability across the three field properties of spectrum, beam pattern and polarization, I will comment on what could be the major directions for the field in the coming decade.

A gate driver IC is an important circuit bridging the voltage gap between control ICs operating at less than 5V and the power electronics operating above 100V. The conventional gate driver IC, however, just turns on/off the power transistors and shows the trade-off between the switching loss and the switching noise of the power transistors. In addition, the conventional gate driver IC need to be customized for a large variety of power transistors. To solve the problems, we proposed a programmable general-purpose digital gate driver IC, which dynamically changes the gate drive current during the turn-on/off transient with digital control bits. In the developed gate driver IC fabricated with 40V, 0.18um BCD process, the 6-bit gate control signals with four 160-ns time steps are globally optimized using a simulated annealing algorithm, reducing the switching noise by 37% and the switching loss by 47% at the double pulse test of 300V, 50A insulated gate bipolar transistor (IGBT). The gate driver is also applied to a half-bridge inverter, where the gate driving waveform is changed depending on the load current.

Integrated voltage regulation is critical to the energy efficiency in every systems ranging from high-end processors to ultra-low power IoT devices. Challenges of the integrated power management circuits include the large number of voltage domains, DVFS per domain, large current transients, and wide dynamic range of current loads. In addition, IoT systems present new challenges to the voltage regulators, keeping the high power conversion efficiency at the ultra-low input voltage ( < 0.1V) and/or the ultra-small output current ( < 1uA). In this talk, I will present several circuit designs of voltage regulators for IoT systems, including a sub-0.5V digital LDO / digital-analog hybrid LDO, a sub-0.5V-input buck converter, and a sub-0.1V-input boost converter for the thermoelectric energy harvesting.

The organic electronics enables flexible, large-area, and distributed sensor and/or actuator array and is suitable for the wearing-unconscious devices used in biomedical and healthcare applications.

Power delivery to ultra-thin flexible devices with the thickness of 1um to 10um, however, is a challenge, because wired connections and rigid battery are not allowed. To solve the problem, novel flexible devices for wearable healthcare applications with the energy harvesting or the wireless powering using organic circuits are proposed and demonstrated. In this talk, I will show an insole pedometer with piezoelectric energy harvesters, a fever alarm armband with solar cells, and a wet sensor sheet in a diaper with wireless powering.