A woman in Phoenix uses a computer and webcam to visit nightly with her young grandson in New York. A pediatrician hiking in the Smoky Mountains consults by cell phone on a critical case in Atlanta. Enemy radar sets off warnings in a U.S. military aircraft, which immediately turns away from the danger.

Everyone recognizes such events, and millions like them, as benefits of digital technology of microprocessors and software, of bits and bytes.

Fewer know that these and most other electronic miracles would be impossible without another technology that is also thriving analog electronics.

Designing these ubiquitous circuits which feed information and power to digital components is sometimes called an art form. Thats because analog engineers must choose among a multitude of materials and techniques to best perform a given function. Analog expertise is in high demand globally, and analog microelectronics provide strong revenue for technology companies large and small.

The world is analog, says Joy Laskar, director of the Georgia Electronic Design Center (GEDC), a 250-person center at Georgia Tech that specializes in analog and mixed-signal (analog-digital) research. Analog circuits model the world and capture real-world information so it can be digitally processed.

Analog electronics are especially important in mobile devices, adds Laskar, who is the Schlumberger Chair in Microelectronics in Georgia Techs School of Electrical and Computer Engineering (ECE). Anything thats untethered, from cell phones to hearing aids, will have heavy analog content.

Generally speaking, analog technology plays a crucial role in three major electronic areas:

• Input/Output (IO): Analog microelectronics are essential to radio frequency (RF) and microwave devices, including cell phones and MP3 players; military radar systems and satellites; miniaturized antennas; microphones and temperature sensors; image sensors for cameras and scanners; hard drives and other data-storage devices; biomedical applications, and more.
• Power: Analog technology supports delivery, management and conditioning of power, which is essential in wireless devices where power issues are critical; its especially important for power conservation because analog chips use less power than digital designs.
• New applications: Todays analog research is expanding into novel areas, including analog circuits that can be reprogrammed like digital chips; tiny devices called micro-electromechanical systems (MEMS) that actually move at the microscale; and new analog techniques that combine with digital technology to facilitate extremely high data rates and frequencies in both the wireless and wired domains.The Indispensable Technology 
  Analog technology, once the cornerstone of both electronics and computing, was supposed to be on the endangered-circuits list by now. During the digital revolution of the 1980s, when inexpensive microprocessors brought programmable computing to an eager world, experts proclaimed that the flexible new technology would eclipse older, fixed-function analog approaches.

Those predictions didnt pan out. Not only has analog technology remained essential to microelectronic communications and computing, but todays engineers are extending analogs usefulness in many ways. Through continuing miniaturization and sophisticated new techniques, investigators are utilizing both pure or core analog technology as well as mixed-signal approaches that combine analog and digital functions cooperatively in a single integrated circuit.

Georgia Tech is among a handful of universities that has continued to emphasize analog research and education, even during the 1980s and early 1990s when many were downgrading their analog programs. Today, the number of Georgia Tech faculty who focus on analog and mixed-signal engineering stands at 14, and that total continues to grow. This faculty group combined with numerous research faculty, post-doctoral researchers and hundreds of undergraduate and graduate students pursuing analog degrees mark Georgia Techs analog technology program as probably the largest in the United States.

Georgia Tech professors and researchers are pursuing new analog-based approaches in a variety of areas, including biotechnology and neuromorphic design, reprogrammable analog circuits, power approaches such as microscale fuel cells and power harvesting, and manufacturing reliability and quality. They are designing improved analog and mixed-signal electronics for a host of uses, from optimizing todays civilian and military communications to exploiting underutilized frequencies.

Traditional workhorse analog design is important, too. At the Georgia Tech Research Institute (GTRI), some engineers are using their expertise to replace obsolete analog circuits, typically in military aircraft and communications. By using available parts to develop cheaper and more reliable designs, they help keep U.S. aircraft in the air.

The Georgia Electronic Design Center 

Nowhere at Georgia Tech is the analog focus more intense than at the Georgia Electronic Design Center (GEDC). Established in 2003, the center occupies 42,000 square feet in the Technology Square Research Building. GEDCs assets include 13 professors who serve as research-team leaders, some 200 graduate and undergraduate researchers and more than $20 million in test and other equipment.

The Georgia Electronic Design Centers work is supported by about $13 million in annual research funding. That money comes from federal government agencies, the state of Georgia and more than 40 industry partners, making the center a leader in industry involvement at Georgia Tech.

GEDCs research is varied, but much of its work focuses on analog and mixed-signal approaches aimed at improving wireless/RF and wired/fiber-optic performance.

The centers principal research includes four main focus areas:

• Gigabit wireless Led by GEDC Director Laskar and head researcher Stephane Pinel, this effort utilizes analog-digital designs to propel vast amounts of data over short distances using extremely high frequencies in the unlicensed 60 Gigahertz (GHz) range. The record data-transfer rates achieved to date 15 gigabits per second (Gbps) over a distance of 1 meter, 10 Gbps at 2 meters and 5 Gbps at 5 meters could result in desktop computer setups that need no connecting wires, handheld devices able to download entire movies in a few seconds, and wireless in-room transmission from DVD players to screens. This technology represents the first all-digital-controlled analog CMOS radios operating at such frequencies. GEDCs gigabit wireless work is expected to lay a foundation for future digital-controlled applications in the millimeter-wave spectrum frequencies above 20 GHz including digital radar. The work is supported by the Defense Advanced Research Projects Agency (DARPA), the Department of Defense, the National Science Foundation (NSF) and industry.
• Cognitive radio This research, developed in concert with Samsung Electro-Mechanics Co. and led by Laskar and researcher Kyutae Lim, is aimed at forging new international IEEE standards governing more efficient use of wireless frequencies. Cognitive radio (CR) technologies enable wireless transmissions to find low-traffic frequencies and thus bypass bottlenecks or avoid enemy jamming. GEDC recently fabricated a new chip design that could help demonstrate CRs effectiveness.
• Agile Optical/Photonic In partnership with Italian telecommunications giant Pirelli, GEDC is using a testbed equipped with 320 kilometers of special optical fiber to research wired high-speed telecommunications networks. The aim is to use nanotechnology and low-cost mixed-signal chips to design flexible fiber-optic networks with tunable components. The new design would replace outmoded fixed networks based on bulky optical components and help providers meet consumer demand for increased bandwidth. Research faculty working on this project include head researcher Chris Scholz, Stephane Pinel and Edward Gebara.
• RFID/Wireless Sensor Radio-frequency identification technology (RFID) holds great promise in numerous areas including shipping, industry and retail. By enabling inconspicuous circuits that can be placed in cargo containers, automobiles or elsewhere, RFID allows wireless tracking of myriad items. RFID research at GEDC is led by Manos Tentzeris, an associate professor in the School of Electrical and Computer Engineering (ECE). Tentzeris team focuses on using cutting-edge analog techniques to produce low-power devices with high-quality signal performance including low-cost antennas and sensors that can be printed on paper.Teaching Analog New Tricks 
  At the Georgia Tech Analog Consortium (GTAC), a long-established analog-design group that is now part of GEDC, Director John Papapolymerou oversees several groups that are pushing analog-technology boundaries. Papapolymerou, an associate professor in the School of Electrical and Computer Engineering (ECE), is himself involved in several analog-related projects, including research that is helping to develop CAD software for the design of micro-electromechanical systems (MEMS).

Paul Hasler, an associate professor in ECE and a GTAC team leader, has discovered techniques to program analog circuits in ways reminiscent of digital processors. Traditionally, analog circuits have been fixed-function hard-wired to perform a specific task. Working frequently with David Anderson, an ECE associate professor and GEDC researcher who focuses on mixed-signal design, Hasler has been researching core analog capabilities for many years.

Just saying that the world went digital doesnt address the crucial point, Hasler says. Whats key is that a programmable technology overtook a fixed-function technology.

In their research, Hasler and his team have developed programmable analog circuits made with conventional materials and techniques but capable of taking over many functions from digital ICs.

Digital may be a little better for communication, but in terms of computation thats not necessarily the case at all, Hasler says. Programmable analog could be part of the entire-signal processing engine used by mobile devices.

Analog is important, he explains, because analog chips use up to a thousand times less power than their digital counterparts. That makes them far better for mobile uses.

When youre looking at an hour versus a month in terms of your battery life, thats pretty impressive, Hasler says. It just changes the entire game.

Haslers research has led to GTronix, a startup company developing novel technology to extract real-world sensory information for portable consumer electronic products. The company, supported by Menlo Ventures, a major venture capital group, is poised to announce its first product soon.

Farrokh Ayazi, an ECE associate professor and GEDC team leader, is using micro-electromechanical analog technology to develop a frequency-spectrum analyzer and processor on a chip that can offer both the performance and power efficiency needed for mobile use. This technology, known as analog spectral processing, guides an RF signal to lesser-used frequencies and has similarities to GEDCs cognitive-radio work. The research is supported by DARPA.

Ayazi is also researching the integration of microscale MEMS devices with analog, RF and mixed-signal circuits. These micro-mechanical structures could have various applications including minute, highly sophisticated motion sensors.

By converting mechanical signals into electrical signals and processing them using low-power electronics, this motion-sensing technology holds promise in handheld wireless applications such as gaming equipment and for mobile devices that navigate without GPS signals.

Qualtr, a semiconductor-design company based on work at the Integrated MEMS Lab that Ayazi leads, offers six-degree-of-freedom motion sensing devices (three-axis gyroscopes and accelerometers) with low-power integrated read-out and control circuits for consumer products. Qualtr is a member of the Advanced Technology Development Center (ATDC), a startup-company incubator at Georgia Tech.

Ayazi and his team are also investigating silicon arrays of low-power gravimetric gas and bio sensors that are capable of detecting even a single molecule of a target substance. By coating a MEMS device with a molecular-recognition layer, the researchers are bringing the advantages of low-power analog technology to these tiny devices.

In work supported by the National Science Foundation and industry, Ayazi is also studying whether tiny MEMS-based resonators, micromachined into silicon, could replace frequency-producing quartz in mobile devices such as cell phones. The MEMS technology handles higher frequencies than quartz can, while maintaining high performance.

The Silicon-Germanium Connection 

John Cressler, Ken Byers Professor in ECE and a GEDC team leader, develops analog, RF and mixed-signal circuits that exploit the special properties of silicon-germanium (SiGe) alloys. Combining silicon a common microchip material with germanium at nano-scale dimensions, Cressler is helping to develop next-generation microelectronic technologies that promise important gains in speed, flexibility and toughness.

Cressler recently made news when IBM and Georgia Tech research teams collaborated to produce a silicon-germanium transistor able to operate at frequencies above 500 GHz far higher than plain silicon has ever reached. The record was attained at very cold temperatures, but the results suggested that SiGe chips could also attain record speeds at room temperature.

Cressler and his team are also leading a four-year, $14 million NASA program aimed at developing analog/mixed-signal systems for use in exploration of the moon. The work is challenging because of the lunar environments extremely wide, 300-degrees Celsius temperature swings and its exposure to space radiation.

The aim: to use silicon-germaniums robust qualities to replace the bulky, power-hungry, shielded warm boxes currently used in space electronics.

Were taking legacy parts that are the size of a shoebox and putting a single piece of unprotected silicon-germanium in their place, he says.

In the core analog realm, Cressler and his team are investigating the application of silicon-germanium to BiCMOS (SiGe transistors plus CMOS) technology used in very high-performance analog ICs. His team is helping industry researchers understand how to improve the design of these high-end analog circuits and find new applications areas for state-of-the-art analog technologies.

In addition, Cressler is studying the use of SiGe technology to improve data conversion in the very high-speed multi-gigabit range. For years, the problem of converting analog signals into digital code has created a bottleneck because analog-to-digital converters that are extremely fast yet affordable havent existed. New, faster data converters using SiGe could help redefine communications and radar capabilities.

In terms of complexity and challenge in the analog design world, very high-speed data converters are at the top, Cressler says.

Energy and Power Better, Smaller 

Gabriel Rincn-Mora, an ECE associate professor, is focusing analog expertise on powering integrated circuits and other microscale devices, and on using energy and power management to maximize a devices operational life.

Energy/power generation and management for mobile devices will become ever more important in coming years, he says, as new, more capable chips nullify the gains made by advances in power conservation.

Were putting a lot more functionality into a single IC, he says. So we are ultimately increasing power density while maintaining similar power-source levels.

Rincn-Mora is investigating how to provide power to chip-based mobile sensors using a system composed of a proton exchange-membrane fuel cell and a thin-film lithium ion battery. Working with Paul Kohl, a Regents professor in the School of Chemical and Biomolecular Engineering, Rincn-Mora and his team are studying how to manage power throughout the whole system fuel cell, battery and chip in ways that maximize lifetime and minimize footprint.

Rincn-Mora is also investigating microscale techniques to harvest energy from the surrounding environment. In one project, he is working with Texas Instruments to develop an electrostatic harvesting chip that draws power from the kinetic energy in vibrations. He is also working with Sakis Meliopoulos, another ECE professor, to power wireless microsensors in a power grid by using the field that surrounds an electric cable.

In another project, Rincn-Mora is studying how to scavenge energy from the human body. The aim is to power a biomedical implant called a vestibular prosthesis, a device being co-developed by ECE Assistant Professor Pamela Bhatti to help patients regain their sense of balance. Rincn-Mora plans to power the tiny device through piezoelectric harvesting generating power from the motion of tiny materials that bend as bodily fluids in the inner ear flow around the implant.

Bhatti is also collaborating with Shreyes Melkote, a professor in the Woodruff School of Mechanical Engineering, to develop an electrode array that would provide better results to patients with a cochlear prosthesis, used to treat total deafness.

Cutting Costs with Analog 

Analog expertise is an important asset at the Georgia Tech Research Institute (GTRI), Georgia Techs nonprofit applied-research arm. Several GTRI laboratories focus on the analog-heavy field of radar and RF technology for military and civilian applications. And GTRI researchers are often tasked with finding ways to replace older analog circuits, in aircraft and elsewhere, that are no longer manufactured.

Were developing applications as opposed to developing new technologies in analog, says Richard Levin, a GTRI senior research engineer. We find new ways to apply existing technology so that we can meet the customers needs.

Levin has been performing analog design thats helping to re-engineer an older circuit board in an Air Force radar-warning receiver. Key components in the all-analog board are no longer made, and obtaining custom replicas promised to be very expensive. Levin is part of a team that has crafted a plug-in replacement board, using mixed-signal technology that combines analog and digital functions.

Basically, its a more modern, work-alike circuit made from available parts, says Levin.

Mark Mitchell, a GTRI principal research engineer, reports that his group is working on numerous projects that employ analog-intensive technology to design and develop low-cost phased-array antennas.

Phased-array antennas have historically been extremely expensive, he says. Thats limited the number of applications where they can be used.

In one program, Mitchell and his colleagues are collaborating with ECEs Cressler to create a single-chip, phased-array module using cutting-edge silicon-germanium technology.

Current phased-array antennas, which use many multi-chip modules, are bulky. Mitchell and Cressler want to pack that functionality into a single silicon-germanium chip.

You cant get the kind of high-frequency performance we want out of these analog circuits with conventional silicon, Mitchell says. Only silicon germanium can give us that performance and also cut the cost per element down by a couple of orders of magnitude.

Communicating with the Body 

At the Laboratory for Neuroengineering (NeuroLab), the team of Steve DeWeerth, a professor in the Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, is designing custom analog circuits. The twofold aim: to use analog systems to mimic biological performance and to interface with biological systems for medical applications development.

I think Georgia Techs analog design strengths will provide some real opportunities to develop new areas in the biomedical field with real potential biomedical devices, prosthetics and implants, says DeWeerth.

Among other things, the NeuroLab team has developed circuitry for stimulation of neural tissue in vitro. They are using novel analog designs to minimize data loss caused by applying electric-stimulus power, and also to enable accurate feedback.

Thanks to the proliferation of foundries that serve circuit designers, the team now pursues its research using analog circuits made to its own specifications.

One of the advantages of designing our own ICs is that were not confined to what exists out there, says Edgar Brown, a research engineer on DeWeerths team. It would be very difficult to do the kinds of things that were doing with off-the-shelf circuitry.

Maysam Ghovanloo, an assistant professor with ECE and GEDC, focuses on design of integrated circuits and microsystems for implantable biomedical applications. His research involves state-of-the-art neuroprosthesis technology that could communicate with the human nervous system to address serious impairments ranging from from blindness to paralysis.

In his recently established lab, GT-Bionics, Ghovanloo is developing a multi-channel neural recording system to wirelessly monitor freely moving animal brain activities. He is also trying to establish a bidirectional telemetry link with the central nervous system at the cellular level for brain-computer interfacing.

At GEDC, Ghovanloo is initiating collaborations on wireless/RF and MEMS technologies to develop electrodes, antennas and packaging needed for implantable microelectronic devices.

Clearly, analog technology is here to stay. Analog engineers are likely to remain in short supply worldwide for years, says GEDC Director Laskar, as demand for both analog research and applications continues to grow.

Analog and mixed-signal technologies are going to become more important, not less, he says. For the entire microelectronic revolution to proceed robustly, analog research has to keep pace and here at Georgia Tech its an ongoing mission to supply the research and the people to help make that happen.