Question WIFI Antenna Question (Dual Band or 2x Dedicated) & MIMO Antennas ??

Mar 13, 2021
Thanks for reading... Hopefully, someone can help answer these questions for me...
Okay these questions may sound a little strange but I really would like to know the answer, I have searched for hours and hours over the course of days and I can not find any information in regards to my questions.
Let me start by telling you I have 2 Identical USB 3.0 Wifi Adapters AC1200 They use the Realtek 8812BU Chipset (Chipset Info at Bottom Included in case)

Question 1) Is it better to have 2x Dual-Band Antennas (2/4&5Ghz) or
would it better to have 1 antenna dedicated 2.4Ghz and the other a dedicated 5Ghz Antenna?

Image of the Unit with 2 Antennas

So Imagine

One is an AC1200 USB 3.0 Wifi Adapter and it uses 1x 2.4GHz antenna and 1x 5GHz Antenna

The second is an AC1200 USB 3.0 Wifi Adapter BUT it uses 2x Dual-Band Antennas (2.4&5Ghz)

Is 2x Dual Antennas The Same as 1x 2.4 and 1x 5Ghz?
2ND QUESTION WIth Wifi Antennas Do You Need a MIMO Antenna? I included the Realtek Chip Info and it says it supports MIMO.
How do you take advantage of MIMO does it Matter what Type of Antenna? Does it have to say MIMO on it when being Sold? How is a MIMO antenna different from a 2.4Ghz or 5GHz or how is it different from a Dual-Band Antenna???
Very Confusing Info on the Antenna part with MIMO and what is needed?


Detailed Info on the Realtek 8812BU Chipset
General Description -
The Realtek RTL8812BU-CG is a highly integrated single-chip that supports 2-stream 802.11ac solutions with multi-user MIMO (Multiple-Input, Multiple-Output) and Wireless LAN (WLAN) USB interface controller. It combines a WLAN MAC, a 2T2R capable WLAN baseband, and RF in a single chip. The RTL8812BU-CG provides an outstanding solution for a high-performance integrated wireless device.

Features -
TFBGA 6.5x6.5mm package
802.11 ac/abgn
802.11ac 2x2, Wave-2 compatible with MU-MIMO
Host interface

USB3.0 for WLAN controller
I seriously doubt that one unit uses only 1 antenna for 2.4 and a different one for 5 especially if they use the same chipset.

Doing that would be really stupid. These type of adapters only have 1 radio chip it switches between 2.4 and 5. It can not run both at the same time. So why would a manufacture leave a antenna unused.

Now even if you had mulitple radio chips like a router one running 2.4 and the other 5 they can both connect to the same antenna because the radio frequinces are different enough that they do not interfere. You have to remember a antenna is just a piece of wire it has no electronics.

You can really do nothing about mimo. The chip in your nic will negotiate with the chip in the router and if they both support mimo and the signal is good enough they will use mimo. You might be able to disable the function but that is hard to say. Everything is locked up in the radio chips with almost no end user access to prevent people from violating the FCC licenses the chips are required to meet.
Reactions: Krotow
Mar 13, 2021
Thanks for answering.
What got me thinking about that was an image I saw on a web page about MIIMO technology.
After doing crap load of reading I also found this page just recently about MIMO
This was just like the other image I saw which made me wonder about 2 different antennas,
This one has 4 antennas with 2 different types of antennas.

Because MIMO splits the antennas so 2x2, 3x3 or 4x4 it splits the data streams to each antenna, so I would image you need not necessarily the same antennas but if you are transmitting on 2.4 the antenna must be rated for it
The ass-kicker is how the heck do you even know if you are getting or using MIMO its not like you can see that info at all. Like the Realtek chip supports it but I have never seen any app yet that shows you are using MIMO... Maybe I need to see if there is an app for that.... never thought to look until writing this. The technology is used on cell phones as well and you wouldn't know on a cell either
This is a link to the page Scroll all the way to the bottom for the article image...
The reason that one has 2 different types of antenna is because LTE many times operates on a very different frequency than wifi. Wifi can use the same antenna for 2.4 and 5 because it is almost a exact mulitple of 2. You will have to read on antenna design to know why that is signification.

Go look up the MCS table for wifi.

People mistakenly think...well the marketing guys lie to them...that this value is the speed. This is where you see stuff the numbers like 150,300,450 etc. This represent how the data is encoded and one of the things in that encoding is the mimo. You can see the MCS value in interface status...many times it is called speed there also,