03.29.2005 12:00 AM
UCLA Researchers Capture, Digitize Signals at 1,000 GHz Sampling Rate
While many broadcast engineers would be delighted to have a digital oscilloscope with a 1 GHz sampling rate, researchers developing defenses against energy pulse weapons and scientists studying particle physics need faster sampling rates. Professor Bahram Jalalai and graduate researcher Yan Han at UCLA's Henry Samueli Schools of Engineering and Applied Science have developed a single shot digitizer that works at a one-pico second intervals. What I found interesting is the device uses an optical time-dilation processor to slow the event to the point where it can be applied to a conventional electronic digitizer.

Professor Jalalai explained the process. "Imagine you have a flat rubber band and you draw an arrow on it. The arrow's length reflects the duration of the event. When you stretch the rubber band, the arrow is elongated, meaning that the event now occurs over a longer time--in other words, the event is slowed down in time. With our technique, a laser pulse is the rubber band. An optical modulator writes the ultra-fast waveform onto the optical pulse. The composite signal is then slowed down in a dispersive optical device, such as a chain of optical resonators made on a silicon chip. A photo detector then converts everything to the electrical domain and gives a slowed-down copy of the original electrical waveform."

This time-elasticity can also be used to perform time compression and time reversal, which UCLA said is useful in advanced radar systems.

At least two companies are investigating commercial applications for the technology. Salime Boucher, president of RadiaBeam Technologies LLC said, "We see a market for this breakthrough with research laboratories involved in ultra-fast phenomena and transient events, as well as for future applications by engineering and technology companies in the communication, chemical engineering and life science sectors." Aerospace Corporation is considering use of the time stretch A/D converter for potential space applications. "Direct digitization of signals in the 10 to 100 GHz band and beyond offers incredible opportunities for new applications in communications, spectroscopy and radar. Besides breaking the tera-sample-per-second rate barrier, the results reported by Jalali's group at UCLA beat other photonic analog-to-digital converter technologies by about a factor of 10 in the key figure of merit, bit rate times number of quantization levels," said George Valley, senior scientist at Aerospace.

For more information on this interesting technology, see the article UCLA Researchers First to Capture Elusive Lightning Quick Waveforms.


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