433 MHz chip antenna - Page 1
Forum section: electronics / rf-microwave

author: nali
author_rank: Frequent Contributor
timestamp: August 08, 2019, 07:59:40 pm
content: I have a requirement for a compact 433 MHz antenna so I was doing some general searching, and I came across these SMD chip antennas (link below). Only 12x4mm and a specified "gain" of only -1.7dB? Seriously?Does anyone know what principle these work on, or are they just snake oil? I've ordered a couple to have a look at, but I'm curious if anyone has an opinion on them.Datasheet here:https://abracon.com/datasheets/ACAG1204-433-T.pdf

author: ogden
author_rank: Super Contributor
timestamp: August 08, 2019, 08:50:11 pm
content: Not snake oil at all. Ceramic chip antennas are widely used in space-constrained applications. Principle:https://en.wikipedia.org/wiki/Dielectric_resonator_antennaAppnote with some antenna considerations that includes chip some antennas:http://www.ti.com/lit/an/swra161b/swra161b.pdf

author: radiolistener
author_rank: Super Contributor
timestamp: August 09, 2019, 02:33:04 am
content: you can use even a household pin as an antenna. Any piece of wire can be used as antenna. The difference is in efficiency.The antenna on your link doesn't have gain. If you look more close to datasheet, you can see -1.72 dBi. Note, there is a "minus". It means that this is not gain, but actually attenuation!It means that this antenna efficiency is 40% worse than usual half-wavelength dipole, which gain is +2.15 dBi.According to datasheet it has 10 MHz bandwidth at 433 MHz, it means it's Q = 43.3. It leads to 4 times higher field strength than for usual half wavelength dipole, so this antenna will have high loss and you're needs to place it away from field sensitive components.So, there is nothing unusual. This antenna is just a small household pin with circuit for impedance match

author: chrisl
author_rank: Regular Contributor
timestamp: August 09, 2019, 05:06:06 am
content: Quote from: nali on August 08, 2019, 07:59:40 pm-1.7dB is the peak gain. The average gain is more like -5dB.

author: nali
author_rank: Frequent Contributor
timestamp: August 09, 2019, 08:34:54 am
content: Quote from: ogden on August 08, 2019, 08:50:11 pmThanks, I'll take a read of that when I've got a bit of time.Quote from: radiolistener on August 09, 2019, 02:33:04 amI get that, that's why I put "gain" in quote marks. I was a bit surprised that it was so high. (Er, maybe that should be not low?) however...Quote from: chrisl on August 09, 2019, 05:06:06 amI missed that! Guilty of skimming the spec sheet (I should know better, leave it till the morning)The application normally uses "puck" type antennas something likethesewhich normally contain a small helix. They are normally mounted on a metal chassis so have a nice groundplane but are severely limited in height so a common whip or helical is out of the question. It's RX only and short range so quite forgiving in terms of absolute performance but size/shape constraints make it a near impossible task at such a low frequency.

author: ogden
author_rank: Super Contributor
timestamp: August 09, 2019, 08:49:39 am
content: Quote from: nali on August 09, 2019, 08:34:54 amIn case of short range higher freq ISM bands are better choice than 433MHz. 2.4GHz for example.

author: nali
author_rank: Frequent Contributor
timestamp: August 09, 2019, 09:08:14 am
content: Quote from: ogden on August 09, 2019, 08:49:39 amSure although I forgot to mention (sorry) it's a legacy system we've inherited so I don't really have a choice. You're right of course and we're dragging things into the 21st century by moving to BLE but I expect the inertia of the 433MHz system means it'll be sold for the next year or two (and maintained for some time after that)I can't really discuss the end application in a public forum but let's just say it's a form of proximity detection...

author: Gribo
author_rank: Frequent Contributor
timestamp: August 09, 2019, 04:24:52 pm
content: There are better alternate chip antennas for 433. Lynx technologies Splatch is one (Bigger) and Rainsun's 1603 (Similar in size) is another.There is also a ceramic antenna made by Mitsubishi that covers this band, but it is relatively hard to find.

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 11, 2019, 04:10:42 pm
content: Well 433 is in the Middle of the Amateur Radio Band.Why does no Amateur Radio Hobbist make an DVB-T Transmission there?I would use only 868 because its Made for and there are no other Transmission.