The purpose of this study is to verify that a digital single sideband modulator can he incorporated into a Digital Radio Frequency Memory (DRFM). The single sideband modulator is designed to use digital multiplying integrated circuits to produce the frequency shift rather than analog mixers. The circuit also employs a digital Hilbert transform filter to shift the phase of the incoming signal by 90 degrees. The circuit was tested with simulated S-band radar signals ranging from 3.012 to 3.038 GHz. The circuit, running in double sideband mode, proved its ability to shift the frequencies of the radar signals by frequencies in the range of-25 to +25 kHz. All the spurious outputs of the system were found to be more than 28 dB below the carrier.
The moment I walked into the newsroom, I could tell that something was wrong. A group of editors were huddled around the city desk, talking. The televisions were on. People didn't just look tense; they looked genuinely worried. As I walked over to my desk, I saw the image of a burning building. It was the World Trade Center. I was standing there when the second tower fell. I had the same thought that I'm sure a lot of people had: How could this be happening? But I'm also a newspaper reporter, and I realized that there was a science story to be done: Why did the towers fall? Six or seven hours later, I needed to have a finished story that answered that question. It is hard enough to successfully translate the arcane jargon of science into a story for the general reader. A ticking clock makes it that much more difficult—the words “exciting” and “terrifying” come to mind. For a science reporter, this type of breaking news situation doesn't happen very often. One of the great surprises when I moved to science writing a few years ago was that many of the news stories that appear in daily papers were not, in fact, written on deadline. I used to be in awe that someone had the ability to boil down some complex journal article on human origins or supernovas, reach all the important people, and write a clear, elegant article in a day. Many of the big journals, of course, operate on an embargo system, in which reporters are given advance copies and allowed to report ahead of time on the understanding that they won't publish a story until the journal appears in print. But there are still times when science news must be delivered on a daily deadline, either because news breaks or because you have a scoop you don't want to lose. In these cases, I think that everyone who does this for a living develops his own set of tools for coping. Success requires a ruthless attention to where you are in the process, where you are in the day, and what you still need.
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