William R. Eisenstadt - US grants

Even in today's increasingly digital world, analog continuous time circuits are needed in many applications. Current approaches to analog processing are running up against fundamental limitations. Log-domain filtering is a relatively new approach that offers wide dynamic range and excellent high-frequency response using simple, low-voltage circuits. Log-domain filters exploit the translinear current-voltage characteristics of bipolar transistors or weak-inversion MOSFETS to achieve overall linearity. The basic signal processing elements can be quite simple in form and their high-frequency performance can be excellent while distortion can be low because most of the transistor non-linearities are cancelled within the circuit. This research has three major thrusts: The first thrust is toward fundamental, design-oriented analysis of log-domain circuits. Design methodologies and fundamental understanding of the limitations of log-domain filters are in an early stage. Fundamental analyses allow development of figures of merit for evaluating and comparing log-domain circuits. The second thrust focuses on developing new log-domain circuit topologies. Based on an understanding of fundamental limitations, new circuits are being designed to improve performance. The third thrust is toward applications of log-domain circuits. Integrated circuits are being built and tested to demonstrate the usefulness of log-domain circuits in practical applications. Initial focus is on two application areas: low-voltage wireless communications, to exploit the performance potential of log- domain circuits and adaptive and biologically inspired circuits, to build on their fundamental simplicity.

PROJECT TITLE: ITR: Built-In Test of High Speed/RF Mixed Signal Electronics

PROPOSAL NO.: 0325555
INSTITUTION: Georgia Inst. Technology, GA
PRINCIPAL INVESTIGATOR: Abhijit Chatterjee (lead PI)

PROPOSAL NO.: 0325371
INSTITUTION: U. Texas, Austin, TX
PRINCIPAL INVESTIGATOR: Jacob Abrahams (coPI)

PROPOSAL NO.: 0325426
INSTITUTION: Auburn University, Alabama
PRINCIPAL INVESTIGATOR: Adit D. Singh (coPI)

PROPOSAL NO.: 0325340
INSTITUTION: University of Florida
PRINCIPAL INVESTIGATOR:William R. Eisenstadt (coPI)

ABSTRACT:
In the recent past, there has been a tremendous surge in the wired communications/wireless/high-speed IC manufacturing sector. While the design community has pushed the design envelope far into the future, the test barriers have not kept pace with the test requirements of high speed, integrated wireless and wired communications designs. Every IC that is manufactured, needs to be tested against its design specifications before shipment to the customer. As the speeds of these ICs increase, so do the requirements of the testers needed to test these ICs in manufacturing production. High-speed testers above 2 GHz are prohibitively expensive. Consequently, for speeds beyond a few GHz (2 - 25 GHz), built-in test (BIT) of high-speed/RF systems is a very attractive solution. Built-in test involves incorporation of test circuitry in the IC itself to facilitate the manufacturing test process. In this way, many of the test functions are performed "on-chip," alleviating the need for a high-speed (expensive) external tester. Since test cost is projected to escalate to about 40% of the total manufacturing cost of complex communications ICs in the near future, the use of built-in test is expected to significantly impact the cost of the manufactured ICs themselves and the ability of companies to compete in the marketplace.
The core concept behind the proposed built-in test methodology is easy to follow. Instead of directly measuring the high-speed test specifications of the IC-under-test, a new paradigm for BIT of high-speed/RF circuits using alternate tests is proposed. Alternate tests are compact tests that are much more simpler to run than the original specification tests but contain as much information (or more) about the performance of the circuit-under-test as the original tests themselves. Furthermore, it is possible to design these tests so that pass-fail decisions can be made, based on analysis of analog signals using analog circuitry. In this way, two problems are solved: (a) that of being able to measure complex high-speed test specifications using simple on-chip test resources and a low-cost external tester, and (b) that of being able to analyze very high-speed signals (> 2 Ghz) without the need to digitize them (such digitizers are not available or are very expensive at these frequencies). The proposed work is interdisciplinary and will involve the use of concepts from computer algorithms, analog/RF circuit design, mathematics and statistics and fundamental electrical engineering and device physics.

The objective of this research is to establish a millimeter-wave high frequency electronic device characterization system. To meet the demand for increased information bandwidth and operating frequency, scientists and engineers are trying to understand the issues associated with various electronic devices operating at millimeter-wave frequencies. In the near future, the reduction in device feature sizes will result in the use of millimeter-wave frequencies in many communication systems and computers. University of Florida will use the proposed electronic device characterization system, including a 67GHz network analyzer, a 50GHz spectrum analyzer, and an existing high frequency probe station to establish research and educational programs that will benefit our nation's millimeter-wave industry for next 10 years.

The acquisition of the electronic device characterization system will benefit many interdisciplinary research programs such as RF/High-Speed System-On-Chip Integration, High-Performance Computer Architecture, Wireless Sensors, and Advanced Devices and Circuits in Silicon and III-V Technologies. The equipment will be used to advance knowledge of materials, devices, circuits, and systems across multiple disciplines in different departments. The project will also make impacts on advancing multidisciplinary research and training of graduate and undergraduate students. Students from different disciplines will have opportunities to learn how the new materials and device technologies improve electronic device performance, and how to use the instrument to characterize device performance. The project will benefit many minority students in UF and reach out to state and nation's engineering community.

The objective of this research is to develop efficient millimeter-wave chip-to-chip data communications for multicore processors. The approach is to develop small CMOS compatible antennas for data transfers. The project involves design, analysis, and measurement of millimeter wave antennas on silicon and the interface electronics for on-chip communications. This includes electromagnetic modeling, circuit simulation and measurement on prototypes. Special antennas will be created to ensure minimal interaction between the antennas used for data transfers and the nearby CMOS circuitry used for processing.

The project's intellectual merits lie in its innovative approach to high-speed data transfers between integrated circuits in multicore computers. In processors with upwards of 100 cores, physical connections are complex and severely restrict performance. The use of the air-interface above the processors is a new concept for efficient data communications. High efficiency on-chip multi-antenna arrays will enable programmable direct processor-to-processor communications. The antenna links will increase data rates, conserve power, and consume an extremely small area.

The broader impacts of this research include potentially completely new computer architectures that enable fast computation of the world's largest problems, such as predictive models for severe weather forecasting. The research results will be used for a project for freshman college engineering courses and for elementary school demonstrations. Small low-profile antennas integrated onto Lego Mindstorms robots will be created so that the robots can communicate to one another wirelessly. Creation of this hands-on project is expected to improve recruitment and retention of a diversity of students in engineering.

Excess fertilizer application from farm fields results in nitrogen runoff which causes major drinking water contamination as well as commercial fishing and tourism industry decline. Therefore, it is vitally important to have accurate predictive nitrogen soil models that can help farmers reduce fertilizer use by knowing exactly what type of fertilizer to use and precisely when and where in a field to apply. However, the accuracy of these soil models is lacking because soil nitrogen concentration data acquired at numerous points within a field is currently cost prohibitive and technically challenging. This research will create low-cost sensors that can electrically transmit soil nitrogen levels (ammonium and nitrate ion concentration levels) from various soil depths and locations to a central hub so that data can be transmitted through the internet and analyzed remotely. Sensors that can be fitted with low-cost data transmission electronics will be made of low-cost graphene (carbon) that is disposable and can be created using scalable manufacturing protocols. The completed sensors will be tested in the soils surrounding tomato plants to acquire high resolution spatial and temporal nitrogen data for improving soil nitrogen models that can be utilized by farmers.

The objective of this project is to develop bury-and-forget nitrogen sensors coupled with remote sensing technologies for real-time analysis of soil health. The sensors will be developed with flexible graphene electrodes functionalized with ionophore membranes for sensing of ammonium and nitrate ions in soils using laser inscribing and inkjet printing techniques (Aim 1). A network of these sensors will be developed using commercial Bluetooth-based mesh network modules for sensor power, computing, and communications (Aim 2). This project will elucidate the sensor depth and broadcast frequency that is capable/needed for successful in-soil nitrogen monitoring using a bucket brigade approach. This sensor network will be merged with existing crop models developed and challenged with in-field relevant conditions using a model tomato system in a testbed facility (Aim 3). The testbed facility will be used for collecting high resolution nitrogen sensor data from the soil coupled with monitoring of the Normalized Difference Vegetation Index of the plants as benchmarks to integrate remote sensing and real-time field measurements. The proposed project will lead to new: 1) wireless nitrogen sensors (both labile and mobile); 2) knowledge of spatiotemporal dynamics of soil nitrogen coupled with above ground plant physiology; 3) knowledge of scaling micro/nanosensor subsurface soil data, long-duration signal acquisition/curation, and pinpointing the maximum wireless data transmission depth in soil; and 4) best management practices for coupling soil sensor results to current field-scale tools such as remote sensing. The project will be the first to connect in-situ nanosensors, remote sensing, and crop modeling for the same sample, therein establishing a platform for improving understanding of soil biogeochemistry, sensor networks, and fundamental spatiotemporal scaling principles. This project will facilitate rapid studies for improving empirical model parameters (crop coefficients), as well as to validate assumptions in remote sensing (links between yellowing leaves and nutrient stress) and in-situ soil sensors (nutrient fate and transport). In addition to testing the developed sensor systems, this project will establish strategies and best practices for the development, testing, and deployment of soil nutrient sensors that can be reproduced anywhere for sensor testing and/or hypothesis testing, leading to improved models and observation networks to manage soil health. Such sensor networks and resultant models are expected to lead to precision agriculture where fertilizers are spread onto specific locations of the field in a metered fashion only when needed.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.