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A really good article! The telecoms world is fascinating, it's a whole separate parallel stack that doesn't get talked about anything like as much as the web wo
by snops 8y ago
A really good article! The telecoms world is fascinating, it's a whole separate parallel stack that doesn't get talked about anything like as much as the web world.
One section caught my eye, and I wanted to add some detail:
>In order to efficiently send and receive signals, antennas should be no smaller than half the size of the radio waves they’re dealing with. If cell waves are 6 to 14 inches, their antennas need to be 3-7 inches. Now stop and think about the average height of a mobile phone, and why they never seem to get much smaller.
A common neat trick is to take advantage of the fact that this is only true in air, and the wavelength depends on the material around the antenna. Some modern antennas (especially common in GPS and Bluetooth) are built as a metal foil around a ceramic element, which has a much shorter wavelength and allows them to be shrunk[1].
You can also "fold" the antenna a bit, and hence get away with a quarter wavelength in return for reduced performance in other areas. A common example in phones is the Inverted F antenna [2].
Finally, a large "invisible" component of many antennas is the size of the ground plane attached. Shrinking this can affect antenna performance a lot. Generally, this is an internal copper layer of the PCB that is used by other components too, but it's important to realise its an important part of the RF performance. Therefore, you can't judge how good an antenna is from the visible size of it alone, the form of the whole device matters.
[1] https://electronics.stackexchange.com/a/245245 https://electronics.stackexchange.com/a/245245
[2]
http://www.antenna-theory.com/antennas/aperture/ifa.php http://www.antenna-theory.com/antennas/aperture/ifa.php
- VBprogrammer 8y agoI spent a couple of days playing with antennas and an RTL-SDR dongle. It's quite an interesting subject which I'd love to learn more about one day. I mostly used it for listening in on ATC. It was cool to make an Antenna (in this case a half wave dipole) which could hear aircraft out over the English channel from my livingroom in London.
- kevincennis 8y agoWe used these at Aereo: https://en.wikipedia.org/wiki/Electrically_small_antenna https://en.wikipedia.org/wiki/Electrically_small_antenna
- scottbot 8y agoThat's fascinating. I'm the author of the piece, and the material trick and its ramifications is new to me, thank you! This entire subject is not my area of expertise - I'm an historian of 17th century astronomy - but it's been fun dipping my toes into this world.
- sizzle 8y agoWhat are some of your favorite topics from 17th century astronomy, you would recommend to anyone interested in learning more about it. Sounds fascinating thanks!
- vvanders 8y agoIf you want to dive into the deep pool of antennas the experimentation side of ham radio is dedicated to this, among other interesting technical topics. Personally I find it a fascinating hobby and never run out of fun things to research/build/test.
- trumped 8y ago> In order to efficiently send and receive signals, antennas should be no smaller than half the size of the radio waves they’re dealing with. If cell waves are 6 to 14 inches, their antennas need to be 3-7 inches. Now stop and think about the average height of a mobile phone, and why they never seem to get much smaller. over the last few years, phones have gotten a lot larger on average... maybe we'll get to one wavelength soon...
- xxpor 8y agoOn the other hand, LTE bands are moving down the spectrum (longer wavelength). T-mobile for example are rolling out 600 mhz service right now, meanwhile while I sit here in Downtown Seattle I'm connected to 1900 mhz, so less than 1/3 of the length.
- axaxs 8y agoI wouldn't say that. TMobile is the outlier. Most 5G deployments will have mich, much shorter wavelengths.
- blattimwind 8y agoAnd a lot heavier, too.
- DonHopkins 8y agoSo will we ever have tiny cell phones like Zoolander?
- voltagex_ 8y agoYes - search "mini phone" on AliExpress or similar.
- fourmii 8y agoAlthough I did have one of these in the early 2000s: https://www.mobilegazette.com/siemens-sl55-08x10x26.htm https://www.mobilegazette.com/siemens-sl55-08x10x26.htm
- lultimouomo 8y agoWe already have, and they're apparently very popular in prisons: https://www.vice.com/en_uk/article/zngpz4/prison-phones-that-go-up-your-bum https://www.vice.com/en_uk/article/zngpz4/prison-phones-that...