"ALGORITHMS: Ultra-Wideband scheme banishes the delay line"

A new breed of ultrawideband radio that uses a mixer instead of a delay line could solve longstanding deployment problems, its developers say. The technique, invented by engineers at the University of Massachusetts (Amherst), was unveiled last week at the International Conference on Ultra-Wideband in Waltham, Mass. One of the most promising approaches to UWB was to send a nanosecond reference pulse before each data pulse, giving the radio a time frame in which to search its spectrum for data bits. However, after nearly a decade of attempting to use delay lines to synchronize data collection, most research into that approach has come to a halt. The new approach scraps the delay line idea for a mixer, which is easy to build even for ultrashort pulses. A reference pulse is still sent, but is mixed together with the data bit and multiplied by a cosine. On the receiving end is another mixer, with one input coming from the antenna and one from a sine wave generator.
Text: http://www.eetimes.com/showArticle.jhtml?articleID=193006315