EECS Colloquium

Wednesday, October 2, 2019

306 Soda Hall (HP Auditorium)
4:00 – 5:00 pm

Eli Yablonovitch

Professor of Electrical Engineering and Computer Sciences
UC Berkeley

Eli Yablonovitch speaks on "How We Got Cellphone Antennas Wrong For 20 Years; and How We Fixed It," 10/02/19


Antenna Physics has been taken for granted in both Engineering and Physics.  Yet when a new technology—cellphones—emerged nobody knew how to proceed.  The result was a hilarious progression of cellphone antenna designs over 20 years, which made no scientific sense, yet were manufactured and distributed in hundreds of millions of units.  The actual physics of antennas is hardly taught, nor is it available in a single text-book.   Given that cellphones and smartphones underpin the wireless connected world this situation was unacceptable.  Finally, in the past decade or so the problem became solved.  The antennas in cellphones, carried by almost every human on the planet, are multi-frequency resonant objects, enabling universal wireless connectivity.


Eli Yablonovitch holds the James & Katherine Lau Chair in Engineering and is the Director of the NSF Center for Energy Efficient Electronics Science (E3S).   He introduced the idea that strained semiconductor lasers could have superior performance owing to reduced valence band (hole) effective mass. With almost every human interaction with the internet, optical telecommunication occurs by strained semiconductor lasers.  He is regarded as a Father of the Photonic BandGap concept, and he coined the term “Photonic Crystal.” The geometrical structure of the first experimentally realized Photonic bandgap is sometimes called “Yablonovite.”  In his photovoltaic research, Yablonovitch introduced the 4(n squared) (“Yablonovitch Limit”) light-trapping factor that is in worldwide use, for almost all commercial solar panels.  His mantra that “a great solar cell also needs to be a great LED,” is the basis of the world record solar cells: single-junction 29.1% efficiency; dual-junction 31.5%; quadruple-junction 38.8% efficiency; all at 1 sun.  He co-Founded Ethertronics Inc., which shipped over 2 billion cellphone antennas while he was on the Board.

Video of Presentation