Analog, Mixed-Signal, and Radio-Frequency

Electronic Design Group

Electrical and Computer Engineering Department

UNC Charlotte

February 2005

Teaching and Research Faculty

David M. Binkley, Associate Professor, group leader

Arun Ravindran, Assistant Professor

Thomas P. Weldon, Associate Professor

Teaching Faculty (Microelectronics and Optoelectronics Group)

Kasra Daneshvar, Professor

Edward B. Stokes, Associate Professor

Farid M. Tranjan, Professor

Overview

Semiconductor integrated circuits (chips) continually expand beyond digital computer and memory products, requiring analog, mixed-signal, and RF circuits. Analog circuits amplify and condition signals from sensors, actuators, and other devices that interface to the physical world. Mixed-signal circuits combine both analog and digital circuits to provide analog-to-digital, digital-to-analog, and other conversions between analog and digital circuits. RF circuits interface to antenna and wired systems to receive and transmit wireless and wired signals. Analog, mixed-signal, and RF circuits are required in cellular phone, wireless networking, broadband internet access, consumer products, medical imaging, and other high-growth applications. The Semiconductor Industry Association predicts over 60% of all semiconductor chips will contain analog, mixed-signal, or RF circuits.

The analog, mixed-signal, and RF electronic design group at UNC Charlotte is engaged in teaching and research to support the high demand for design professionals in North Carolina and the nation. North Carolina design companies include Analog Devices, RF Micro Devices, Maxim, Linear Technology, Texas Instruments, IBM, International Rectifier, Intersil, Sematech, Sony-Ericson, Rambus, Tality, Triad Semiconductor, and others. In addition to teaching, the group endeavors to enhance the state-of-the-art through novel research published in international conferences and journals.

Faculty

The analog, mixed-signal, and RF electronic design group consists of three, full-time faculty members active in electronic design research. The faculty has over 30 years of industry electronic design experience applied to medical imaging equipment, micropower battery-operated consumer products, and communications products. This assists the faculty in collaborating with and addressing the needs of North Carolina’s considerable semiconductor industry. Additional faculty active in microelectronics device research teach core undergraduate and graduate analog electronics courses.

Research

Faculty in the analog, mixed-signal, and RF electronic design group are engaged in a wide variety of research projects involving design and testing. Technologies utilized include sub-micron bulk CMOS, silicon-on-insulator (SOI) CMOS for extreme temperatures and radiation, and organic and amorphous silicon processes for large-area, lost-cost electronics.

Past research projects include

Present research projects include

Teaching

Analog, mixed-signal, and RF electronic design faculty, assisted by microelectronic device faculty, offer a robust selection of undergraduate and graduate courses in analog, mixed-signal, and RF design. These courses are intended to meet the high demand for design professionals in North Carolina and the nation. Additionally, these courses prepare graduate students to conduct new research. In addition to traditional undergraduate electronics courses, the faculty offers the following undergraduate senior and graduate courses.

4131/5131, Linear Integrated Circuit Design (senior/M.S.). This course prepares students for operational amplifier analysis and design with emphasis on bipolar transistor integrated circuit design. MOS and BiCMOS analog integrated circuit design is also introduced. Students do a large design project and prepare a detailed final report covering analysis and SPICE computer simulations.

4132/5132, Analog Integrated Circuit Design (senior/M.S.). This course prepares students for transistor-level analog CMOS integrated circuit design including MOS strong-inversion modeling and circuit analysis. Emphasis is placed on hand analysis of MOS current mirrors, operational amplifiers, feedback amplifiers, and other analog circuits with SPICE computer simulation used for verification. Course makes extensive use of professor’s notes motivated by industry design experience. Students design an operational amplifier with layout using Cadence.

6437, Mixed-Signal Design (M.S./Ph.D). This project-oriented course prepares students for analog integrated circuit layout, verification, and SPICE simulations using commercial CAD tools. Students develop CAD skills and apply these in a major project where they design, layout, and submit a CMOS, mixed-signal chip for MOSIS fabrication. This course serves to prepare students for graduate research and industry work in analog integrated circuit design, layout, and CAD usage.

6264, Radio Frequency Design, (M.S./Ph.D.). This course presents the architectures of modern RF receivers, transmitters, and transceivers and develops the language of RF design, including noise figure, intercept point, spurious-free dynamic range, and other measures of performance. Cascaded analysis of receiver stages is presented along with s-parameters and Smith-chart matching. Agilent ADS CAD software is utilized for a major design project.

6263/8263, Advanced Analog Integrated Circuit Design (M.S./Ph.D.). This course prepares students for advanced transistor-level, analog CMOS integrated circuit design. This course presents techniques for optimizing gain, bandwidth, thermal noise, flicker noise, dc mismatch, and other analog tradeoffs from weak through strong inversion. Course notes include material from Optimizing Analog CMOS Design, to be published by John Wiley and Sons. The course also includes a review of contemporary literature from the IEEE Journal of Solid-State Circuits and a major design project.

6157/8157, Data Converter Design, (M.S./Ph.D.)

This course presents z-domain analysis, analysis of switched capacitor circuits, performance specifications of data converters, and architectures of modern data converters. Analysis of flash, interpolating, folding, cyclic, sigma-delta and other converters are presented. Students utilize Cadence CAD software for circuit and behavioral modeling and layout of a major data converter project.

Integrated-circuit technologies utilized for teaching and research

The analog, mixed-signal, and RF electronic design group utilizes AMI’s 0.5‑mm CMOS process for classroom projects and graduate research. Fabrication is provided by the MOSIS educational service. Additionally, the group utilizes TSMC’s 0.18‑mm CMOS process for advanced, low-voltage research. Here, fabrication is provided by the MOSIS research service. Research sponsors provide additional fabrication in specialty processes, including Honeywell’s 0.35‑mm PD SOI CMOS process.

Laboratory and CAD Facilities

Within the new Science and Technology building, the analog, mixed-signal, and RF electronic design group will share a 2,500 square-foot laboratory with related digital integrated circuit design and testing. There will also be faculty and graduate student office space, and additional research laboratories devoted to microelectronics device research and clean-room operations. At present, laboratory and office space is shared between the Cameron Research and Smith buildings.

Dedicated research instrumentation supports signal excitation, measurement, and spectral/network analysis from DC up to 18 GHz. Additionally, instrumentation supports device I-V, C-V, noise, and s-parameter measurements, including measurements over extreme temperatures in a cryostat. Software includes the Mentor Graphics and Cadence design suites for schematic capture, integrated-circuit layout, and simulations along with Agilent’s ADS RF simulation package. Computing equipment includes numerous office and laboratory PC and Sun computers, all networked through the college-of-engineering MOSAIC system.

Research Highlights

Figure 1. Analog CMOS Optimization Tool (sponsored by DARPA neoCAD program). The designer selects MOS drain current, inversion coefficient (a numerical measure of inversion from weak through strong inversion), and channel length and observes the design tradeoffs of bias voltages, small-signal parameters, gain, bandwidth, dc mismatch, and noise. Circuit performance goals may be set where green bargraph displays denote goals are met while red bargraph displays denote goals are not met. This CAD tool minimizes trial-and-error SPICE simulations by providing design guidance and intuition.

10 x 10 element MEMS probe (left) and variable-gain preamplifier architecture (right). Each neural probe is connected to a separate preamplifier, requiring micropower low-noise operation.

Preamplifier schematic notated with low-noise design techniques. Resistive noise degeneration ensures input pair devices dominate both thermal and low-frequency flicker noise. Input pair devices are operated in moderate inversion for high transconductance efficiency and minimum input-referred thermal noise voltage for the bias current of 1 mA

Figure 2. Micropower, low-noise 0.35‑mm CMOS preamplifier for neural implant (sponsored by Jet Propulsion Laboratory). 100 preamplifiers amplify low-level voltage signals from a MEMs neural probe. Scientists at California Institute of Technology are conducting experiments with monkeys to process and decode signals corresponding to desired arm movements. If successful, this research could lead to human, thought-controlled artificial limbs.

Figure 3. Experimental integrated circuits in linearization research (sponsored by MixSig Labs, Inc., and National Science Foundation). Upper left is layout of 0.18-mm CMOS, linearized RF integrated circuit; upper right is simplified block diagram of patented linearization method; middle is measured gain up to 5 GHz; bottom is two-tone linearized spectrum measured at 1 GHz.

Figure 4. Experimental research in micropower analog-to-digital converters. Upper left is microphotograph of CMOS 0.5-mm 10-bit, 500 Ksps CMOS, Micropower ADC; upper right is ADC test setup; bottom is the post-calibration FFT spectrum