Convert a 2x2 MIMO antenna to RHCP

SatNOGS Hardware
1

Hej,

got an antenna newbie question.

Currently i got a 2x2 MIMO 4G antenna i use for my initial little S-Band tests. It got 2 orthogonal linear polarization on individual N connectors. (https://kroksw.com/shop/antennas-gsm-3g-4g-wifi/broadband-mimo-feed-kip9-17002700-dp-for-satellite-dish/)

For now i use only one output.

  • Would it be possible to combine both outputs using a phasing line and a combiner with impedance matching to turn it into RHCP ?
  • Does it depend on the internal build of the antenna or would that be possible for all 2x2 MIMO antennas ?
  • If possible would it bring some benefits ?
  • Or just better build a helix ?

Thanks

Martin HB9FXX

2

Hi Martin,
17:56 Sat 17 Oct 20 , Martin Herren via Libre Space Community wrote:

got an antenna newbie question.

Currently i got a 2x2 MIMO 4G antenna i use for my initial little S-Band tests. It got 2 orthogonal linear polarization on individual N connectors. (https://kroksw.com/shop/antennas-gsm-3g-4g-wifi/broadband-mimo-feed-kip9-17002700-dp-for-satellite-dish/)

Nice idea!

For now i use only one output.

  • Would it be possible to combine both outputs using a phasing line and a combiner with impedance matching to turn it into RHCP ?

Sure, you can use a quadrature ibrid:

https://www.microwaves101.com/encyclopedias/quadrature-couplers

http://microwaveeng.com/product/quadrature-hybrids-couplers-dividers-combiners/

https://www.rfcafe.com/references/electrical/directional-coupler.htm

And is not difficult to built one by yourself but maybe you need a good
substrate: FR4 has too much loss for this purpose, every tenth of dB of loss
became a tenth of dB increase of NF

  • Does it depend on the internal build of the antenna or would that be possible for all 2x2 MIMO antennas ?

I suppose the antenna has two orthogonal dipole or similar so each got a
polarization and can be combined with 90deg phasing to obtain rhcp or lhcp

  • If possible would it bring some benefits ?

If sat is not stabilized signal will not change with attitude using cp

  • Or just better build a helix ?

I’ve no experience with the antenna you mention but for what it cost it could
be a good attempt; I’ve no experience with S-band sats, too…

73, Lapo IK5NAX

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3

Never designed an RF board yet so this could be an interesting projects. but doing it right will take some time and a bunch of prototypes. So maybe i can find an existing hybrid quadrature coupler to start with.

At least i’ll start experimenting with kicad’s rftool suite. Yes, a good substrate will be required.

The internal looks like two ‘leaf’ shaped orthogonal dipoles on a PCB with 2 discs in front that look like directors. Will investigate some more the internals. I guess the ‘leaf shaped’ dipoles are about to provide the wide bandwidth.

Thanks for your valuable input, will definitively try to find more about it and do some tests.

73s de Martin HB9FXX

4

Hi,

Yes, at 2GHz a bit of experience is needed to design even an hybrid coupler. If you can’t find a surplus one you could evaluate something like this:
https://www.digikey.it/product-detail/it/anaren/X3C19F1-03S/1173-1186-1-ND/7724490
or
https://www.mouser.it/ProductDetail/AVX/PC2025A2700AT002?qs=DorwNQD7R7F5qj7y6tTchg%3D%3D

Try qucs: qucs.sourceforge.net/

I’m interested too, let us know

You’re welcome and you made me want to experiment on S band! :slight_smile:

73, Lapo IK5NAX

1 Like