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First Fully Digital Radio Transmitter Built Purely From Microprocessor Tech
Zothecula writes For the first time in history, a prototype radio has been created that is claimed to be completely digital, generating high-frequency radio waves purely through the use of integrated circuits and a set of patented algorithms without using conventional analog radio circuits in any way whatsoever. This breakthrough technology promises to vastly improve the wireless communications capabilities of everything from 5G mobile technology to the multitude devices aimed at supporting the Internet of Things (IoT).
The 1620 was an all digital machine built of discrete transistors. As an undergraduate, we wrote programs that caused the machine to alternate between two loops at a variable rate. The computer radiated so many harmonics that this could be heard all across the AM band where no strong station existed. We programmed it to play (mostly) classical music, "Flight of the Bumblebee" was the perennial favorite. Any truly all digital transmitter will generate harmonics outside of the allowable FCC band, so at the very least they need a really good analog bandpass filter on the output.
Most of the people commenting on this story have no clue about signal processing or radios. It is quite possible to feed a "stream of bits" to an analog filter and create a clean analog signal. This is effectively what 1-bit delta-sigma data converters do, and it is close to what Class-D audio amplifiers do. The trick is indeed doing this with wide bandwidth signals and sufficient oversampling to have good signal quality. To get wide bandwidth at 5GHz, they probably are running the sampling rate in the GHz range to get a few 10's of MHz bandwidth and picking off (filtering/selecting) a harmonic at 5GHz. An antenna and matching network are a type of filter network. There's a lot of innovation in these areas, and it's annoying to see uniformed /.'ers dumping on an area they don't understand.