So... What is RF?

I've found a lot of people working on the outskirts of the RF field ask this important, fundamental question. Whether that be business leaders, managers, and even other engineers supporting the field, this is a question us RF engineers must have an immediate answer to when asked. Here's what I say whenever I get asked this question...

There are four forces of nature. Gravity, the strong nuclear force, the weak nuclear force, and the electromagnetic force. 

Electromagnetism in particular is the study of how electrically charged particles interact with each other as well as electric and magnetic fields. Electromagnetism is the physical force, and the electromagnetic spectrum is the range of waves that come from it - spanning everything from radio waves, to visible light, to gamma rays. "RF" is a slice of that electromagnetic spectrum with frequencies ranging from roughly 3kHz to 300GHz. At the very core, radio frequency is just a band of frequencies within electromagnetism. 

Now, why is this slice of the spectrum so important when designing RF based tech? At these frequencies, wavelengths become a lot smaller. Small enough that the physical size of the circuits, wires, and components start to matter. Signals no longer behave like simple voltages moving through wires. Instead, they behave like traveling electromagnetic waves.

Wires can radiate.

Traces can reflect energy.

Geometry becomes part of the circuit.

This is the point where classical circuit theory begins to mesh with electromagnetic wave behavior. That's the world RF engineers operate in.

So, what is it? Applied electromagnetics used to move energy and information through space.