2.4Ghz Ultra High Gain Omni Directional Receiver

[chek28]

Hi,

I want to know if someone can help me, knowing how to do an ultra high gain 2.4Ghz Receiver. We want to use the best high gain LNA available and also a good omnidirectional antenna, what do you think is best option for 360° radiation?, 1/2 wave antenna, microstrip?. I know that are many things to take in consideration. Any suggestions are very welcome, also if someone can help us further my email is: chek1977@hotmail.com

Thanks to everyone that take time to read this post

Bernardo

 

[jiripolivka]

You do not specify what "ultra-high" gain you need, and for what.

There are omnidirectional antenna designs, like "twin cone" you can try with your LNA, that have >10 dB gain.
If you want to build a search receiver, a better choice is to use sectorial antennas, e.g. four, each covering 90 deg. and use four LNAs or complete receivers.

 

[chek28]

We have a client that want to put small rfid tags to the animals to verify if they are inside the limit area. We already tried 1/4 wave antenna receiver but the results are not so good, that´s why we want to design or buy a true 360° omnidirectional antenna or as you said, put 4 antennas to cover all degrees with 4 receiver modules connected to one Wifi or GSM master. I saw some 30-50dB gain LNA´s. My question is it that gain is real and increase the range distance or not?. Is better use a high gain antenna, high gain LNA or both?.

Thanks for your reply and time!

 

[mtwieg]

Just to be clear, antenna gain and directionality correlate very closely with each other, and there is a tradeoff between the two. An omnidirectional antenna will always have lower gain than a directional antenna (with the same electrical efficiency). So what you probably want is an omnidirectional and efficient antenna, not an omnidirectional high gain antenna.

For RF localization, time of flight is often preferred to signal intensity measurement, since it's not too sensitive to directionality (though it has problems of its own, and in general is more complicated).

 

[chek28]

Correct, we have to use an omnidirectional efficient antenna but my doubt is the range that we can reach with it, that´s why is better to us have a very powerful receiver RX, because the transfer TX can send it signal at maximum of 0 dBm according to regulations.

Thanks a lot to guide me to a clear way

 

[jiripolivka]

Correct, we have to use an omnidirectional efficient antenna but my doubt is the range that we can reach with it, that´s why is better to us have a very powerful receiver RX, because the transfer TX can send it signal at maximum of 0 dBm according to regulations.

Thanks a lot to guide me to a clear way

This is an interesting problem I tried to solve years ago with UHF. All above colleagues are right in that you need to cover a large area with a low "illumination" power while trying to receive remote answers with a low power.
Using an "omni" at 2.4 GHz is possible but such antenna would have a limited gain and possibly large size. I would prefer to use e.g. four sectorial antennas each covering ~90 deg. in H plane with a narrow beam in E-plane. A simple corner reflector with a dipole feed will do. The reflector should be at least five wavelengths long.
For simplicity I would use one set of such antennas to transmit and another to receive. You can locate one set above the other. The low-noise amplifiers are good in the receivers, only use RF band-pass filters to reduce a possible interference in 2.4 GHz band. If your RFID signal is FM or BPSK, you can use low-cost FM receivers sold with "wireless cameras". They have microvolt sensitivity and with a good antenna, they may allow the system to cover >100 m o a flat terrain.
Be ready to experiment; as the RFIDs have no directional antennas, the range is limited.