Design and implementation of 4 bit binary weighted current steering DAC

A compact current-mode Digital-to-Analog converter (DAC) suitable for biomedical application is repesented in this paper .The designed DAC is binary weighted in 180nm CMOS technology with 1.8V supply voltage. In this implementation, authors have focused on calculaton of Non linearity error say INL and DNL for 4 bit DAC having various type of switches: NMOS, PMOS and Transmission Gate. The implemented DAC uses lower area and power compared to unary architecture due to absence of digital decoders. The desired value of Integrated non linearity (INL) and Differential non linearity (DNL) for DAC for are within a range of +0.5LSB. Result obtained in this works for INL and DNL for the case DAC using Transmission Gate is +0.34LSB and +0.38 LSB respectively with 22mW power dissipation

Digitally-Assisted RF IC Design Techniques for Reliable Performance

Semiconductor industries have competitively scaled down CMOS devices to attain benefits of low cost, high performance, and high integration density in digital integrated circuits. On the other hand, deep scaled technologies inextricably accompany a large process variation, supply voltage scaling, and reduction in breakdown voltages of transistors. When it comes to RF/analog IC design, CMOS scaling adversely affects its reliability due to large performance variation and limited linearity. For addressing the issues related to variations and linearity, this research proposes the following digitally-assisted RF circuit design techniques: self-calibration system for RF phase shifters and wide dynamic range LNAs. Due to PVT variations in scaled technologies, RF phase shifter design becomes more challenging with device scaling. In the proposed self-calibration topology, we devised a novel phase sensing method and a pulsewidth-to-digital converter. The feedback controller is also designed in digital domain, which is robust to PVT variations. These unique techniques enable a sensing/control loop tolerant to PVT variations. The self-calibration loop was applied to a 7 to 13GHz phase shifter. With the calibration, the estimated phase error is less than 2 degrees. To overcome the linearity issue in scaled technologies, a digitally-controlled dual-mode LNA design is presented. A narrowband (5.1GHz) and a wideband (0.8 to 6GHz) LNA can be toggled between high-gain and high-linearity modes by digital control bits according to the input signal power. A compact design, which provides negligible performance degradation by additional circuitry, is achieved by sharing most of the components between the two operation modes. The narrowband and the wideband LNA achieves an input-referred P1dB of -1.8dBm and +4.2dBm, respectively

Dynamically Controllable Integrated Radiation and Self-Correcting Power Generation in mm-Wave Circuits and Systems

This thesis presents novel design methodologies for integrated radiators and power generation at mm-wave frequencies that are enabled by the continued integration of various electronic and electromagnetic (EM) structures onto the same substrate. Beginning with the observation that transistors and their connections to EM radiating structures on an integrated substrate are essentially free, the concept of multi-port driven (MPD) radiators is introduced, which opens a vast design space that has been generally ignored due to the cost structure associated with discrete components that favors fewer transistors connected to antennas through a single port. From Maxwell's equations, a new antenna architecture, the radial MPD antennas based on the concept of MPD radiators, is analyzed to gain intuition as to the important design parameters that explain the wide-band nature of the antenna itself. The radiator is then designed and implemented at 160 GHz in a 0.13 um SiGe BiCMOS process, and the single element design has a measured effective isotropic radiated power (EIRP) of +4.6 dBm with a total radiated power of 0.63 mW. Next, the radial MPD radiator is adapted to enable dynamic polarization control (DPC). A DPC antenna is capable of controlling its radiated polarization dynamically, and entirely electronically, with no mechanical reconfiguration required. This can be done by having multiple antennas with different polarizations, or within a single antenna that has multiple drive points, as in the case of the MPD radiator with DPC. This radiator changes its polarization by adjusting the relative phase and amplitude of its multiple ports to produce polarizations with any polarization angle, and a wide range of axial ratios. A 2x1 MPD radiator array with DPC at 105 GHz is presented whose measurements show control of the polarization angle throughout the entire 0 degree through 180 degree range while in the linear polarization mode and maintaining axial ratios above 10 dB in all cases. Control of the axial ratio is also demonstrated with a measured range from 2.4 dB through 14 dB, while maintaining a fixed polarization angle. The radiator itself has a measured maximum EIRP of +7.8 dBm, with a total radiated power of 0.9 mW, and is capable of beam steering. MPD radiators were also applied in the domain of integrated silicon photonics. For these designs, the driver transistor circuitry was replaced with silicon optical waveguides and photodiodes to produce a 350 GHz signal. Three of these optical MPD radiator designs have been implemented as 2x2 arrays at 350 GHz. The first is a beam forming array that has a simulated gain of 12.1 dBi with a simulated EIRP of -2 dBm. The second has the same simulated performance, but includes optical phase modulators that enable two-dimensional beam steering. Finally, a third design incorporates multi-antenna DPC by combining the outputs of both left and right handed circularly polarized MPD antennas to produce a linear polarization with controllable polarization angle, and has a simulated gain of 11.9 dBi and EIRP of -3 dBm. In simulation, it can tune the polarization from 0 degrees through 180 degrees while maintaining a radiated power that has a 0.35 dB maximum deviation from the mean. The reliability of mm-wave radiators and power amplifiers was also investigated, and two self-healing systems have been proposed. Self-healing is a global feedback method where integrated sensors detect the performance of the circuit after fabrication and report that data to a digital control algorithm. The algorithm then is capable of setting actuators that can control the performance of the mm-wave circuit and counteract any performance degradation that is observed by the sensors. The first system is for a MPD radiator array with a partially integrated self-healing system. The self-healing MPD radiator senses substrate modes through substrate mode pickup sensors and infers the far-field radiated pattern from those sensors. DC current sensors are also included to determine the DC power consumption of the system. Actuators are implemented in the form of phase and amplitude control of the multiple drive points. The second self-healing system is a fully integrated self-healing power amplifier (PA) at 28 GHz. This system measures the output power, gain and efficiency of the PA using radio frequency (RF) power sensors, DC current sensors and junction temperature sensors. The digital block is synthesized from VHDL code on-chip and it can actuate the output power combining matching network using tunable transmission line stubs, as well as the DC operating point of the amplifying transistors through bias control. Measurements of 20 chips confirm self-healing for two different algorithms for process variation and transistor mismatch, while measurements from 10 chips show healing for load impedance mismatch, and linearity healing. Laser induced partial and total transistor failure show the benefit of self-healing in the case of catastrophic failure, with improvements of up to 3.9 dB over the default case. An exemplary yield specification shows self-healing improving the yield from 0% up through 80%.</p

Proximal-Field Radiation Sensors for Dynamically Controllable and Self-Correcting Integrated Radiators

One of the major challenges in the design of integrated radiators at mm-wave frequencies is the generation of surface waves in the dielectric substrate by the on-chip antennas. Since dielectric substrates are excellent surface waveguides with a fundamental mode with no cutoff frequency, there is always some energy trapped in them due to the surface waves and the excited substrate modes. This phenomenon is a significant cause of reduced radiation efficiency for mm-wave integrated radiators. However, in this thesis, we use this as an opportunity. We show that the excited substrate modes in the dielectric substrate of an integrated antenna contain valuable information regarding its far-field radiation properties. We introduce Proximal-Field Radiation Sensors (PFRS) as a number of small sensing antennas that are placed strategically on the same substrate as the integrated antenna and measure electromagnetic waves in its immediate proximity. These sensors extract the existing information in the substrate modes and use it to predict the far-field radiation properties of the integrated antenna in real-time based on in-situ measurements in the close proximity of the antennas, without any need to use additional test equipment and without removing the antenna from its operating environment or interfering with its operation in a wireless system. In other words, PFRS enables self-calibration, self-correction, and self-monitoring of the performance of the integrated antennas. Design intuition and a variety of data processing schemes for these sensors are discussed. Two proof-of-concept prototypes are fabricated on printed circuit board (PCB) and integrated circuit (IC) and both verify PFRS capabilities in prediction of radiation properties solely based on in-situ measurements. Dynamically controllable integrated radiators would significantly benefit from PFRS, These radiators are capable of controlling their radiation parameters such as polarization and beam steering angle through their actuators and control units. In these cases, PFRS serves as a tool for real-time monitoring of their radiation parameters, so that without direct measurement of the far-field properties through bulky equipment the required information for the control units and the actuators are provided. Dynamically controllable integrated radiators can be designed using the additional design space provided by Multi-Port Driven (MPD) radiator methodology. After a review of advantages of MPD design over the traditional single-port design, we show that a slot-based MPD radiator would have the additional advantage of reduced exclusive use area compared to the original wire-based MPD radiator, through demonstration of a 134.5-GHz integrated slot-based MPD radiator with a measured single-element EIRP of +6.0 dBm and a total radiated power of -1.3 dBm. We discuss how MPD methodology enables the new concept of Dynamic Polarization Control, as a method to ensure polarization matching of the transmitter antenna to the receiver antenna, regardless of the polarization and orientation of the receiver antenna in space. A DPC antenna design using the MPD methodology is described and a 105.5-GHz 2x1 integrated DPC radiator array with a maximum EIRP of +7.8 dBm and a total radiated power of 0.9 mW is presented as the first demonstration of an integrated radiator with DPC capability. This prototype can control the polarization angle across the entire tuning range of 0 to 180 degrees while maintaining axial ratios above 10 dB, and control the axial ratio from 2.4 dB (near circular) to 14 dB (linear). We also demonstrate how simultaneous two-dimensional beam steering and DPC capabilities can even match the polarization to a mobile receiver antenna through a prototype 123-GHz 2x2 integrated DPC radiator array with a maximum EIRP of +12.3 dBm, polarization angle control across the full range of 0to 180 degrees as well as tunable axial ratio down to 1.2 dB and beam steering of up to 15 degrees in both dimensions. We also use slot-based DPC antennas to fabricate a 120-GHz integrated slot-based DPC radiator array, expected to have a maximum EIRP of +15.5 dBm. We also introduce a new modulation scheme called Polarization Modulation (Pol-M) as a result of DPC capability, where the polarization itself is used for encoding the data. Pol-M is a spatial modulation method and is orthogonal to the existing phase and amplitude modulation schemes. Thus, it could be added on top of those schemes to enable creation of 4-D data constellations, or it can be used as the only basis for modulation to increase the stream security by misleading the undesired receivers. We discuss how DPC antenna enables Pol-M and also present PCB prototypes for Pol-M transmitter and receiver units operating at 2.4 GHz.</p

Silicon-Based Terahertz Circuits and Systems

The Terahertz frequency range, often referred to as the `Terahertz' gap, lies wedged between microwave at the lower end and infrared at the higher end of the spectrum, occupying frequencies between 0.3-3.0 THz. For a long time, applications in THz frequencies had been limited to astronomy and chemical sciences, but with advancement in THz technology in recent years, it has shown great promise in a wide range of applications ranging from disease diagnostics, non-invasive early skin cancer detection, label-free DNA sequencing to security screening for concealed weapons and contraband detection, global environmental monitoring, nondestructive quality control and ultra-fast wireless communication. Up until recently, the terahertz frequency range has been mostly addressed by high mobility compound III-V processes, expensive nonlinear optics, or cryogenically cooled quantum cascade lasers. A low cost, room temperature alternative can enable the development of such a wide array of applications, not currently accessible due to cost and size limitations. In this thesis, we will discuss our approach towards development of integrated terahertz technology in silicon-based processes. In the spirit of academic research, we will address frequencies close to 0.3 THz as 'Terahertz'. In this thesis, we address both fronts of integrated THz systems in silicon: THz power generation, radiation and transmitter systems, and THz signal detection and receiver systems. THz power generation in silicon-based integrated circuit technology is challenging due to lower carrier mobility, lower cut-o frequencies compared to compound III-V processes, lower breakdown voltages and lossy passives. Radiation from silicon chip is also challenging due to lossy substrates and high dielectric constant of silicon. In this work, we propose novel ways of combining circuit and electromagnetic techniques in a holistic design approach, which can overcome limitations of conventional block-by-block or partitioned design methodology, in order to generate high-frequency signals above the classical definition of cut-off frequencies (ƒt/ƒmax). We demonstrate this design philosophy in an active electromagnetic structure, which we call Distributed Active Radiator. It is inspired by an Inverse Maxwellian approach, where instead of using classical circuit and electromagnetic blocks to generate and radiate THz frequencies, we formulate surface (metal) currents in silicon chip for a desired THz field prole and develop active means of controlling different harmonic currents to perform signal generation, frequency multiplication, radiation and lossless filtering, simultaneously in a compact footprint. By removing the articial boundaries between circuits, electromagnetics and antenna, we open ourselves to a broader design space. This enabled us to demonstrate the rst 1 mW Eective-isotropic-radiated-power(EIRP) THz (0.29 THz) source in CMOS with total radiated power being three orders of magnitude more than previously demonstrated. We also proposed a near-field synchronization mechanism, which is a scalable method of realizing large arrays of synchronized autonomous radiating sources in silicon. We also demonstrate the first THz CMOS array with digitally controlled beam-scanning in 2D space with radiated output EIRP of nearly 10 mW at 0.28 THz. On the receiver side, we use a similar electronics and electromagnetics co-design approach to realize a 4x4 pixel integrated silicon Terahertz camera demonstrating to the best of our knowledge, the most sensitive silicon THz detector array without using post-processing, silicon lens or high-resistivity substrate options (NEP &lt; 10 pW &#8730; Hz at 0.26 THz). We put the 16 pixel silicon THz camera together with the CMOS DAR THz power generation arrays and demonstrated, for the first time, an all silicon THz imaging system with a CMOS source.</p

Improving the mechanistic study of neuromuscular diseases through the development of a fully wireless and implantable recording device

Neuromuscular diseases manifest by a handful of known phenotypes affecting the peripheral nerves, skeletal muscle fibers, and neuromuscular junction. Common signs of these diseases include demyelination, myasthenia, atrophy, and aberrant muscle activity—all of which may be tracked over time using one or more electrophysiological markers. Mice, which are the predominant mammalian model for most human diseases, have been used to study congenital neuromuscular diseases for decades. However, our understanding of the mechanisms underlying these pathologies is still incomplete. This is in part due to the lack of instrumentation available to easily collect longitudinal, in vivo electrophysiological activity from mice. There remains a need for a fully wireless, batteryless, and implantable recording system that can be adapted for a variety of electrophysiological measurements and also enable long-term, continuous data collection in very small animals. To meet this need a miniature, chronically implantable device has been developed that is capable of wirelessly coupling energy from electromagnetic fields while implanted within a body. This device can both record and trigger bioelectric events and may be chronically implanted in rodents as small as mice. This grants investigators the ability to continuously observe electrophysiological changes corresponding to disease progression in a single, freely behaving, untethered animal. The fully wireless closed-loop system is an adaptable solution for a range of long-term mechanistic and diagnostic studies in rodent disease models. Its high level of functionality, adjustable parameters, accessible building blocks, reprogrammable firmware, and modular electrode interface offer flexibility that is distinctive among fully implantable recording or stimulating devices. The key significance of this work is that it has generated novel instrumentation in the form of a fully implantable bioelectric recording device having a much higher level of functionality than any other fully wireless system available for mouse work. This has incidentally led to contributions in the areas of wireless power transfer and neural interfaces for upper-limb prosthesis control. Herein the solution space for wireless power transfer is examined including a close inspection of far-field power transfer to implanted bioelectric sensors. Methods of design and characterization for the iterative development of the device are detailed. Furthermore, its performance and utility in remote bioelectric sensing applications is demonstrated with humans, rats, healthy mice, and mouse models for degenerative neuromuscular and motoneuron diseases

An Adaptive Modular Redundancy Technique to Self-regulate Availability, Area, and Energy Consumption in Mission-critical Applications

As reconfigurable devices\u27 capacities and the complexity of applications that use them increase, the need for self-reliance of deployed systems becomes increasingly prominent. A Sustainable Modular Adaptive Redundancy Technique (SMART) composed of a dual-layered organic system is proposed, analyzed, implemented, and experimentally evaluated. SMART relies upon a variety of self-regulating properties to control availability, energy consumption, and area used, in dynamically-changing environments that require high degree of adaptation. The hardware layer is implemented on a Xilinx Virtex-4 Field Programmable Gate Array (FPGA) to provide self-repair using a novel approach called a Reconfigurable Adaptive Redundancy System (RARS). The software layer supervises the organic activities within the FPGA and extends the self-healing capabilities through application-independent, intrinsic, evolutionary repair techniques to leverage the benefits of dynamic Partial Reconfiguration (PR). A SMART prototype is evaluated using a Sobel edge detection application. This prototype is shown to provide sustainability for stressful occurrences of transient and permanent fault injection procedures while still reducing energy consumption and area requirements. An Organic Genetic Algorithm (OGA) technique is shown capable of consistently repairing hard faults while maintaining correct edge detector outputs, by exploiting spatial redundancy in the reconfigurable hardware. A Monte Carlo driven Continuous Markov Time Chains (CTMC) simulation is conducted to compare SMART\u27s availability to industry-standard Triple Modular Technique (TMR) techniques. Based on nine use cases, parameterized with realistic fault and repair rates acquired from publically available sources, the results indicate that availability is significantly enhanced by the adoption of fast repair techniques targeting aging-related hard-faults. Under harsh environments, SMART is shown to improve system availability from 36.02% with lengthy repair techniques to 98.84% with fast ones. This value increases to five nines (99.9998%) under relatively more favorable conditions. Lastly, SMART is compared to twenty eight standard TMR benchmarks that are generated by the widely-accepted BL-TMR tools. Results show that in seven out of nine use cases, SMART is the recommended technique, with power savings ranging from 22% to 29%, and area savings ranging from 17% to 24%, while still maintaining the same level of availability