Why isnt 24 GHz ISM band more popular? - Page 1
Forum section: electronics / projects

author: fonograph
author_rank: Frequent Contributor
timestamp: July 14, 2018, 05:19:53 pm
content: You all know the ISM bands,the frequency spectrum avaliable for average Joe to be used for things from microwave ovens,wifi, bluetooth and wireless drones,to alarms and amateour radio.Some of these bands are avaliable wordwide,other varies from country to country.For long time,2.4 GHz is by far most popular.As result this band is overcrowded in densely populated areas,mainly due to wifi.5.8 GHz is also popular these days,most wifi routers can transmit at 5.8,also most modern smartphones,tablets,notebooks and other devices can recieve at this frequency.Currently,new frequency band is on the rise,the 61.25 GHz.This milimeter wave class band requires state of art expensive electronics but its been already standardized in 802.11ad in 2012.There is even Wireless Gigabit Alliance (WiGig) promoting this 60 GHz band.My question is this,why nobody uses the 24 GHz band? It should be cheaper and have better range than 60 GHz,also unlike the 60,24 is avaliable worldwide just like 2.4 & 5.8.If you google 60 GHz,which barrely even started,there is TONS of articles and all kinds of information.On other hand if you google 24,you find there isnt anything,its like this obscure unknown thing,some GaAs amplifier here,some old scientific paper there,some microwave amateur and thats it.Why is 60 so popular and 24 ignored? Why nobody makes 24 GHz wifi? Its almost like that band doesnt even exist,why everybody ignores it?

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 14, 2018, 05:25:32 pm
content: Here's a product at 24 GHz:https://www.ubnt.com/airfiber/airfiber24/The problems I see is for backhaul applications you have to worry about rain fade, while for indoor stuff you get much less antenna gain than at 60 GHz. Many of the 60 GHz parts have on-die antennas that are impractical at 24 GHz.

author: CopperCone
author_rank: Super Contributor
timestamp: July 14, 2018, 05:32:39 pm
content: Because its ridiculously expensive to do anything precise/custom at those frequencies.Like mac said, if the entire RF thing is handled by the fab and you just solder a bit on, its real appealing. No one wants to try to desgin transmission lines, pcb, etc for 24GHz.If you can eliminate a complicated design step then people will flock for something. Look how popular GSM modules are now, no consumer thing is using its own discrete amplifier if it can avoid it. If you can avoid the little antenna cable and RF connectors and stuff its a manufacturing win. Imagine just routing a flat flex to a little chip you put on a little PCB some where in your product. Thats what they want to do. People are happy if they can get rid of the RF engineer in their company that slows everything down etc. Even getting rid of having to design a PCB antenna with a special ground plane is a win, maybe you can save on VIAsIt's kind of nice because for the same reasons we have GPS capabilities in toaster ovens now.Even though its 60GHz, I think these kinds of parts could get SUPER cheap if they work, since its literary on the die, and you dont need a PCB to mount to another PCB. It might mean the factories are smaller, assembly lines shorter, less process steps so higher quality is guaranteed since there is less stuff to manage and there is less interconnects and mechanical engineering.When they get research grants they need to justify why, and everyone wants to be rich.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 14, 2018, 11:15:02 pm
content: I know a little bit about RF Stuff. So does the higher frequency are not dangerous to use?Higher Freq = more energy required for the same result in comparison with a lower?

author: CopperCone
author_rank: Super Contributor
timestamp: July 14, 2018, 11:20:25 pm
content: well THz might do some things to the blood IIRC but microwaves of significant diameter will just result in heating.However what heating the brain at some specific depth does to your neurochemistry/psychology is not really documented. I suspect it might have an effect on thought process etc. You get some kind of unnatual temperature gradient I think. I don't think classical heat sources can match the temperature gradient created by microwaving your brain.On the plus side as power electronics become more efficient you will heat your brain less by conventional heat from holding a cell phone near it. I doubt its as nature intended to hold a hot rock to your head for hours a day.I have a cyst on my leg where my cell phone pocket was for years. Probably random but idk bro

author: fonograph
author_rank: Frequent Contributor
timestamp: July 15, 2018, 12:28:01 am
content: There is nothing inherently dangerous about higher frequencies.There is more losses so more power consumption and higher frequency photons have higher energy per photon but there is nothing extra dangerous going up in frequency.If anything,high frequency is safer due to skin effect.I rather get third degree RF burn than equivalent amount of DC energy through my inner organs,might be forced to do 24/7 Freddy Kruger cosplay for the rest of my life but still better than death.

author: CopperCone
author_rank: Super Contributor
timestamp: July 15, 2018, 01:42:08 am
content: So long you don't burn your brain, thats like a lobotomy.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 15, 2018, 09:18:10 am
content: When the 24Ghz, 60Ghz Freq is use for Directional Connection the maybe could cause trouble when the beam is not 100% alight.The would Transmit 24/7 and when there are some Apartment Buildings are next to.

author: tooki
author_rank: Super Contributor
timestamp: July 16, 2018, 11:09:44 pm
content: Quote from: fonograph on July 14, 2018, 05:19:53 pmFYI, when you say 5.8GHz band, you’re thinking cordless phones, not WiFi. 5GHz WiFi uses everything from about 5.1-5.8GHz, with 4.9-5.1GHz also defined, but currently not used.

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 17, 2018, 01:12:25 am
content: Quote from: fonograph on July 14, 2018, 05:19:53 pmbecause thats expensive regardless of who is looking at it be it manufacturer or hobbyist. it will be popular, when others below are really saturated. due to expensive and congestion, some of us even look back to 30 - 400MHz band because easier to build and equipments, low power and less affected by weather.

author: Marco
author_rank: Super Contributor
timestamp: July 17, 2018, 01:30:11 am
content: All the problems of optical as far as LoS goes, none of the ease of use.

author: fonograph
author_rank: Frequent Contributor
timestamp: July 18, 2018, 01:49:02 pm
content: Quote from: tooki on July 16, 2018, 11:09:44 pmI thought wifi is only in 5.725 to 5.875 GHz ISM band,I googled it and yout right! Is the 2.4 GHz wifi wider too than the 2.4 to 2.5 ISM band?Does anybody understands these RF bandwidth allocation maps? Wifi and Bluetooth are the "FIXED" category or "AMATEUR"?

author: tooki
author_rank: Super Contributor
timestamp: July 18, 2018, 02:40:46 pm
content: Quote from: fonograph on July 18, 2018, 01:49:02 pmNo. (Surely the same page that confirmed what I said would have answered your question?!?)https://en.wikipedia.org/wiki/List_of_WLAN_channels

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 18, 2018, 02:50:29 pm
content: @fonographSo where are you from? The US?

author: fonograph
author_rank: Frequent Contributor
timestamp: July 18, 2018, 04:22:12 pm
content: Quote from: Lord of nothing on July 18, 2018, 02:50:29 pmMaybe

author: fonograph
author_rank: Frequent Contributor
timestamp: July 18, 2018, 04:25:41 pm
content: Quote from: tooki on July 18, 2018, 02:40:46 pmWhat do you mean same page would have answered my question? I just found some picture on google images that showed the 5 GHz wifi bandwidth.Anyway,thanks for that wiki wlan link,didnt saw it before.

author: Lord of nothing
author_rank: Super Contributor
timestamp: July 18, 2018, 09:10:57 pm
content: https://www.rtr.at/de/tk/Spektrum5GHz

author: AE7OO
author_rank: Regular Contributor
timestamp: July 21, 2018, 04:52:11 am
content: Does anybody understands these RF bandwidth allocation maps? Wifi and Bluetooth are the "FIXED" category or "AMATEUR"?Neither. They both fall under a license exemption based on their use of spread spectrum tech. That is why they are both channel based. They also may not interfere with a licensed service (Such as Amateur radio) and may not complain if interfered with by anyone else(microwaves, some medical equipment, Hams, etc, etc). They are also power limited.On other hand, if my son and I wanted to set up a point to point link, I could run a Kilowatt(If I could fund that kind of amp, talk about money...) into whatever antenna I wanted and as long as I did not interfere with another licensed service I would be fine. I did some high power (45 watts) 2.4Ghz using FHSS for Field Day one year while I lived in Houston, and only had that kind of power because a buddy had picked up some Navy surplus down in Corpus Christi; It did not hurt that I was a Navy ET that worked on S band equipment.One of these days I'll get my tower setup here in Phoenix, mount the SatComm antennas (146, 440, 1.2, and 2.4) and get back on the birds... sigh...

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: July 21, 2018, 05:36:25 am
content: Quote from: fonograph on July 14, 2018, 05:19:53 pmI think there is a good reason why you don't find too much people working on 24 GHz in research - it is too easy. By that I mean that unlike 60 GHz (though even there it's pretty much just an industry problem) pretty much any CMOS technology can do it without too much issues.Another issue is the bandwidth. At the new 60 GHz standards, the channels themselves are more than 2 GHz wide. This means that at 60 GHz we have a much easier time of getting high datarates. And if you need to get microwave engineers in your team anyways (as neither at 24 nor 60 GHz you can just blindly implement a application schematic) there is little difference between the two.And while there are examples of 60 GHz chips with on-chip antenna in research, I was not aware that they existed yet in production. I would be interested if radar_macgyver could share some examples? Pretty much all work I have seen into on-chip antennas is that they are not worth it because the silicon space they take up is just /way/ to expensive. Keep in mind that even with the high effective permittivity in silicon, at 60 GHz we are still dealing with wavelengths of over a millimeter - so your quarter wave antenna will still take up /massive/ silicon area.Another interesting thing about 60 GHz is the atmospheric absorption. This means low range, which is what these WiFi applications target (low interference with other networks, small per-room microcells).

author: Marco
author_rank: Super Contributor
timestamp: July 21, 2018, 05:49:33 am
content: The biggest market opportunity in consumer electronics for 60 GHz was VR ... and it's losing to 5GHz and compression.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 21, 2018, 12:31:08 pm
content: The parts I thought about was the HMC8326/27 and HMC7584/85, these operate at 71-76 and 81-86 GHz respectively. Their inputs are waveguide-coupled, not a true antenna on chip; I stand corrected.

author: LaserSteve
author_rank: Super Contributor
timestamp: July 21, 2018, 08:17:58 pm
content: 24 is a real pain unless your using horn antennas. Nearly any conductive object will act as a beamforming or diffracting object in the near field of a 24 Ghz omni. 24 also has some pretty tight out of band specs to meet.60 can get by with a onchip / on module antenna and is intended for very short distances by designMind you a few ham radio operators have some very long distance records at millimeter wave, but the antenna and feed fabrication needs CNC and some exotic amplifier techniques. The use of narrowband SSB to gain range doesn't make it easier.General rule, if you want to set a distance record with microwaves, use SSB and drop the bandwidth and phase noise to as near zero as possible.Under 10 Ghz, pcb design is easy. Get much above 10 in a consumer product and R&D gets expensive.Steve

author: troyosaurus2014
author_rank: Newbie
timestamp: July 28, 2018, 06:20:02 am
content: Here's another product as well. It's use case seems somewhat limited to base station/facility surveillance.http://spotterrf.com/products/ground-radar/This fairly recent article on EDN also supports the previous posts.https://www.edn.com/design/automotive/4458884/Moving-from-24-GHz-to-77-GHz-radar