Antennas give me a headache

I've studied antenna theory and practice both formally and informally, built and used many designs in many bands, and still they are somewhat of a mystery to me. So many designs, so many different physical structures, it's enough to make your head spin. And how do people come up with some of those bizarre configurations that seem to work so well?

The modern mobile wireless world adds a new priority. Smaller antenna size was always a nice feature, but for mobile devices it's essential. So we have cell phones, laptops, and similar products with antennas that are only small whips, stubs, or even entirely internal. They are so small that it seems that they can't possibly capture enough RF energy, but they do.

I internalize an antenna as a lens, except that it's for RF energy rather than optical energy. So it seems that you'd need a larger antenna to intercept and capture more of that energy, right? In short: More metal spread over a larger area. (Let's just worry about receiving, for now; despite the antenna equivalence principle, transmitting is a more deterministic, less treacherous process.). And yes, serious antennas for tough SNR situations do tend to be larger, with a complex structure, multiple segments, and with a reflecting and focusing elements. Hey, it's not easy to boost the "S" part of the basic SNR equation, but you do what you have to do.

But then I see the other extreme, with a tiny antenna built into a mobile device, and it works, or at least, it works most of the time. My confidence in my lens-equivalent model is shaken. Using a physically tiny antenna, even at short wavelengths where its electrical length is not so small, would be trying to see an image though a pinhole camera (you have fooled around with those, right? Sure, it works, but the image is pretty dim and a long exposure is needed.

It's unresolved conundrums such as these which make me wonder what I really know versus what I only think I know, and that I need to take a long, calming walk.

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