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Electrical and Computer Engineering


Assefzadeh Wins 2nd at 2016 IEEE AP-S Student Paper Awards

In his paper he introduces a trigger-based beamforming technique, the first time the method has been used.

July 8, 2016

Mahdi and HimarshuCongratulations to Mahdi Assefzadeh, graduate student in electrical and computer engineering, on winning 2nd Place in the IEEE Antennas and Propagation Society (AP-S) Student Paper Competition. Assefzadeh is a PhD student in Dr. Aydin Babakhani’s Rice Integrated Systems and Circuits (RISC) Laboratory, and his paper was selected as one of the three finalists out of 158 submissions. He also presented his paper during the regular sessions, in addition to the poster session.

“The paper focuses on a radiating array, a generic radiator that can be used in multiple applications – wireless communication, hyperspectral 3D imaging and THz spectroscopy,” Assefzadeh said.

In his paper, Assefzadeh introduces a trigger-based beamforming technique, the first time the method has been used. By using this technique, the distortive effects of the conventional narrowband method are eliminated by separating the delay path from the information path.

“Conventional techniques are narrowband. They delay the RF signal and this introduces non-linearity and disperses the signal, so there are problems with conventional arrays,” he said. “This new idea will enable generation of high-power THz pulses through a massive number of synchronized elements.”

Assefzadeh’s method generates broadband THz pulses with high repetition rates. He can spatially combine the signals at a specific point by delaying a digital signal using a trigger, effectively eliminating any distortion typically found in the narrowband techniques.

“With this method we can have widely spaced arrays with a large number of elements. If you want to combine the signal from multiple radiators, then this method can perform this beamforming in a broad manner,” he said. “It’s important because all conventional ways are narrowband and so it is not possible to beamform signals with large bandwidth.”

“That is what is really interesting to me, is that our group is about circuits and systems, and this paper was selected as a finalist at an antenna conference,” Assefzadeh said. “This shows that the boundaries between areas in engineering are eroding,” he noted. “Everything in engineering is integrated and there is a lot of overlap in these different communities.”

The competitors to Assefzadeh’s chip are high-powered photonic chips, but he notes their abilities are limited. “They need a bulky high-powered laser, optical alignments, and also their repetition rate is limited, which means they are slower, and they simply cannot be integrated in something like a cell phone,” he explained. “Ours is a fully-electronic chip that is low-cost, accessible, and can be built with a high yield. We are really pushing this technology because of the boundaries it breaks through.”

“The uniqueness of this technique is that you can combine signals from individual radiators that do not have much power, but when added up you can defeat the power of more costly technologies. A colony of ants can take down an elephant if they are numerous enough,” he said. “We are generating really high-powered THz signals. Recently we demonstrated signals up to 1.1 THz from a silicon chip using this new beamforming technique.”

-Jennifer Hunter (originally posted May 9, 2016)