Chen Published in IEEE Transactions on Microwave Theory and Techniques
Congratulations to Peiyu Chen, graduate student in Prof. Aydin Babakhani's RISC lab in the Department of Electrical and Computer Engineering (ECE) at Rice University, on having his paper, "A Nonlinear Q-Switching Impedance Technique for Picosecond Pulse Radiation in Silicon," published in IEEE Transactions on Microwave Theory and Techniques (TMTT). The paper can be read in full here.
The paper provides an in-depth theoretical and simulation study of the Nonlinear Q-Switching Impedance Technique (NLQSI) to produce and radiate picosecond pulses. In addition, a novel optical-based characterization method for silicon chips is discussed in details. This is an extended version of Chen's 2016 paper presented at the International Microwave Symposium (IMS), where he won second place in the Student Paper Competition.
In the IMS paper, Chen proposed a new integrated circuit idea, nonlinear Q-switching impedance (NLQSI), which helps to generate an amplitude reconfigurable picosecond impulse. “NLQSI is a kind of smart circuit block. It senses the circuit and tunes itself adaptively. In this work, it is used to control the pulse amplitude, which is crucial for high speed communications links,” he said.
The designed silicon chip also radiates a world-record 4ps impulse. The pulse-width, 4ps, is also important, Chen noted, because shorter impulses produce images with better resolution. The research has many applications in security imaging, high-speed communications, and the oil & gas industry.
“If the image has better resolution, we can produce 3D radar images with better resolution,” he explained. “The shorter pulse has a broader frequency spectrum. Using it we can do better spectroscopy research and then potentially apply the research to detect more materials or explosives in an airport security check, for example.”
In the IMS paper, Chen also demonstrated a novel optical-electronic-mixed measurement technique for picosecond pulse radiations from a silicon chip. In the proposed method, a photoconductive antenna detector is used with an asynchronous optical sampling (ASOPS) scheme, which is achieved by a commercial THz Time-Domain Spectroscopy (THz-TDS) system.
"The current electronic solutions for measuring picosecond pulses have many problems, such as limited bandwidth, measurement complexities of calibration along the entire receiver path. These problems make the current solutions very difficult to accurately measure picosecond pulses. Our proposed idea resolves these issues. This is the novelty of our work,” Chen said.
The current electronic solutions use a very fast sampling oscilloscope. The best one has the rising time of 4.5ps, which is not fast enough to measure the 4ps the group has achieved. Chen notes that the team will demonstrate high-speed wireless communication link, gas spectroscopy, and 3D radar imaging, based on the leading picosecond pulse generation techniques that RISC invented.
“In terms of circuit designs, for the next step we want to build a fully-integrated picosecond pulse transceiver. And we will also spend more time on the novel THz measurement technique,” he said.
Chen is continuing his research on silicon-based mm-wave and THz impulse transceivers for 3D imaging.