World’s Smallest FM Radio Transmitter

I think this title has changed hands several times already this century. In 2005 we were already down to the the head of a pin [SOURCE] But I think this one stands out as being best smallest and best meeting the definition of a transmitter.  While we are on that topic, let's define transmitter.

"A device or set of components whose primary function is to generate and transmit electromagnetic waves via an antenna." 

To satisfy any semantic arguments, I'm keeping it succinct. It's important to define that an antenna is distinguishable from it's power source, data source and antenna, since they all have different design constraints. It's also important to note that a transmitter may not be used to broadcast a signal, it may be conveyed over a wire, or point to point wirelessly. These devices all still have transmitters. Also many devices emit radio waves as a byproduct of a purpose other than emitting that signal: ex microwaves.

It was produced by a team of Engineering researchers at Columbia Univeristy. It was led by two professors, the Mechanical Engineering Professor James Hone and Electrical Engineering Professor Kenneth Shepard. the device exploits the special properties of graphene to emit a radio wave. Graphene is both strong and conductive.The resulting nano-mechanical system (NEMS) can generate an FM signal. The pictures aren't compelling... it's nano sized. Prof. Hone was quoted as saying "...it’s an important first step in advancing wireless signal processing and designing ultrathin, efficient cell phones. Our devices are much smaller than any other sources of radio signals, and can be put on the same chip that’s used for data processing.” More here.

Their team created a voltage controlled oscillator (VCO) and manipulated graphene’s mechanical ‘stretchability’ to tune it's output frequency. Their NEMS broadcast at about 100 Mhz right in the middle of the FM band. Tests included transmitting low-tones and music. They received the signals with an "ordinary FM radio receiver."  More here.  I'm hoping they try to listen to it on the worlds smallest radio, developed at Berkley back in 2007, here.

Nano Radio

Peter Burke and Chris Rutherglen at the University of California have unveiled a radio made of carbon nanotubes. It's a "detector" only a few atoms across, smaller than a human hair, nearly 1000 times smaller than any preceeding technology. This is the most important and complex part of a radio and it's only a few atoms in diameter. Obviously this lacks a speaker and an amplifer, but it can receive radio waves and convert them into sound.

Much like Shannon's limit (discussed Friday) Every transistor has a maximum speed at which it can function. For silicon, this should be approximately 100 GHz. But current circuits typically operate at less than5 GHz. The speed differnece is only limited by our ability to exploit it. The theoretical maximum speed limit for nanotube transistors should be in the terahertz range. I.E. more than 1,000x faster than silicon.



It was only in 2004 that Burke unveiled transistors made from single-walled carbon nanotubes. Those were aimed at the cell phone market being able to operate into the microwave range. It seemed like a hot item and Burke received a grant from the National Academies Keck Futures Initiative for $75,000 in 2005. So why the hell is he messing around with archaic technology like a radio?