5GHz - 3x3 MIMO Antenna - 3x3 MIMO Feeder

In the past three months me, nikolas_350, and other members of the AWMN community have been trying to design Antennas for Long Range 3x3 Multiple Input Multiple Output MIMO Wireless links.

When Atheros based 3x3 MIMO miniPCI express cards were made available at reasonable prices we decided to come up with a 3x3 MIMO 5GHz feeder design or at least a practical 3x3 MIMO Antenna System and after one, heated at times, discussion we concluded to construct three types of Feeders and run a series of tests. We chose to try out combinations of polarizations , single & multiple offset dish antennas and feeders , and LMR cable lengths until we achieve a practical way to differentiate the three streams enough to achieve 3x3 MIMO above MCS20 on long range links.

We started our quest confident that we can create a four dish-four feeders per link system, hopping that in the process we will come up with a practical two dish-two feeders per link system.

In the AWMN we use mostly offset dish Antennas with 5GHz copper feeders we make ourselves.



We have single ( one polarization ) feeders and double ( horizontal and vertical polarization ) feeders. Our double feeders have been working great in Long 2x2 MIMO 802.11N Links.

classic AWMN 5GHz Feeders







We decided to use RouterOS powered devices in our tests since many people in this group were familiar only with this operating system. Also we had heard rumors that RouterOS works OK with the Atheros based 3x3 MIMO miniPCI express cards and we wanted to try out the Nv2 protocol with 3x3 MIMO.



The Feeders we constructed


The tough parts were made by nvac. We are not a factory --yet.

The 0,90,225 feeder

The 0,120,240 degrees feeder from behind


The 0,120,240 feeder
The 0,120,240 degrees feeder without n-types from above



The 0,90,270 feeder



Our Tests

Our tests were simple.
It works means three spatial streams registered with a sustainable index above MCS20 and bandwidth throughput greater than the 2x2 MIMO upper limit. The 2x2 MIMO maximum bandwidth throughput is approximately 210Mb/s UDP for a 40MHz channel.



Test 1)
Indoor
Three small antennas on each node
A few centimeters up to 10 meters distance between the nodes

When I say small, I mean it, the antennas were λ/4 copper wires.

In the few centimeters up to 2 meters distances the results were excellent and we saw the wireless registration locking at 450Mb/s, and bandwidth tests reporting more than 300Mb/s UDP traffic.





Test 2)
Indoor
One 0,90,225 feeder on each node
5m and 10m distance between the nodes
In a nutshell, it did not work.
We saw momentarily rates above the MCS20 index.



Test 3)
Indoor
One 0,120,240 feeder on each node
5m and 10m distance between the nodes
In a nutshell, it did not work.
We saw momentarily rates above the MCS20 index.



Test 4)
Indoor
One 0,90,270 feeder on each node
It did not work.



Test 5)
Indoor
Two Feeders on each node
One feeder with horizontal and vertical polarization and one feeder with diagonal polarization
It works.
However, we are indoors and away from practical.



The Long Outdoor Tests were made in the ipduh-nikolasc link ~3,5 Km distance.

The offset parabolic dish we are using are 80cm Gilbertini.

Test 6)
Outdoor
One offset parabolic dish with a 0,90,225 feeder on each node
It does not work.
We saw momentarily rates above the MCS20 index.



Test 7)
Outdoor
One offset parabolic dish with a 0,90,270 feeder on each node
It does not work.



Test 8)
Outdoor
One offset parabolic dish with a 0,120,240 feeder on each node
It does not work.
We saw momentarily rates above the MCS20 index.



Test 9)
Outdoor
Two offset parabolic dish with two feeders on each node
One Feeder with vertical & horizontal polarizations and the other with a diagonal 45 degree polarization.
We did not test it yet.


Test 10)
Outdoor
1 offset parabolic dish with the 0,90,225 feeder on each side and variable length LMR cables.
We may achieve to differentiate one stream enough this way.
We did not test it yet.


Test 11)
Outdoor
1 offset parabolic dish with the 0,120,240 feeder on each side and variable length LMR cables.
We did not test it yet.




Waiting for nikolas_350 to recover from the Summer Vacation and get back to business.


to be continued ...



5GHz - 3x3 MIMO Antenna - 3x3 MIMO Feeder