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January 25, 2001 Chunyan Wang's invisible inventions



Engineering Professor Chunyan Wang

Engineering Professor Chunyan Wang

Photo by Andrew Dobrowolskyj

by Janice Hamilton

For some people, the word “inventor” conjures up an image of someone who invents gadgets or machines. Concordia engineering professor Chunyan Wang is an inventor with several patents to her credit, but her inventions are so small, they are invisible to the naked eye. Still, like the best technological breakthroughs, they are simple and easy to implement.

Wang, an assistant professor in the Department of Electrical and Computer Engineering, traveled around the world on her way to Concordia. Along the way, she has learned to adapt to new situations, and make the most of available resources, qualities that perhaps helped develop her flair for invention.

Born in Beijing, she did her undergraduate engineering studies at Shanghai Jiaotong University, graduating in 1982. Following university, she worked for several years, first as an engineer, then making educational films. In 1988, she got an opportunity to study television journalism at the University of Leipzig, in East Germany.

“I had an intensive program in the German language before going there,” she recalls, “but when I got off the plane, I didn’t understand a word.”

She studied there for one year, then headed to Paris where, again, she had to learn the language.

“The first year was hard,” she says. “I had no money, no nothing, but I’m always lucky. I get people’s help.” She spent a year learning French and earning some money doing odd jobs like cleaning, as well as making up some engineering courses.

In the fall of 1990, she started her Master’s program at the Université Paris Sud, specializing in integrated circuits. She completed her PhD in 1996, and in January 1997, she was hired by Concordia.

Since coming to Concordia, her research interests have focused on two main areas: analog-mixed VLSI (very large scale integrated circuits) and large scale CMOS optical sensor integration. Through the Faculty of Engineering and Computer Science, she has applied for patents for three inventions with applications in these areas, and she is currently working on several other projects.

“I’m in optical sensor design,” she says, noting that optical sensors are important as an interface between humans and computers — for cameras and for industrial monitoring, for example.

“Light intensity can easily be converted into current,” she explains, “but most signals work in voltage, so you need to convert.” The motivation behind her first invention was the need for an adaptive current-to-voltage converter that can be used in a sensor.

Conventional converters can be made very sensitive so they can catch small variations, but when the signal is large — for example, when the amplitude varies between 1,000 and 1,010 units — a converter can’t detect the variation because it becomes saturated.

“The integrated circuit I designed is very sensitive, but if the input goes very high, my circuit will follow and be able to detect the top variation.”

Like the clothes she designs for herself, Wang likes things that are simple. For example, she notes, many people in the optical sensor field work with expensive semiconductor materials like GaAs. She uses silicon materials in her designs, not only because it is much cheaper, but also because it allows the circuit to be better integrated with the rest of the sensor, rather than having two parts made of different materials.

Together with two colleagues, she has also invented a simple scheme for performing uniform current comparisons simultaneously, without requiring physically identical comparator cells that just cannot be made in practical fabrication processes.

This invention provides an effective solution to a problem that has frustrated engineers: the transistor-mismatch problem in low-power current-mode signal processing circuits, particularly in two-dimensional smart optical sensors.