[SOLVED] Receiver antenna selection

[Pheezy]

Hello there,

I am presently trying to select what antenna to purchase for this project I am working on. I am trying to receive 2.4 GHz signals from an access point in my university. Its a Cisco 3600 Series AP operating at dual frequencies (2.4 GHz and 5 GHz) (I am only interested in the 2.4 GHz). Its max transmit power is 23 dBm and the integrated 2.4 GHz antenna has 2 dBi gain.
Also, it is omni directional.

Link:
https://www.cisco.com/c/en/us/produ...ironet-3600-series/data_sheet_c78-686782.html

Based on this information, I am trying to decide what receiver antenna to purchase for my circuit. I know the following:
1) I need an omni-directional antenna
2) length of receiver antenna has to be 1/2 of the wavelength of RF signals I am receiving, so for a 2.4 GHz signal, length of my antenna should be 6.25 cm.

I need assistance in deciding the following:
1) the gain of the antenna
2) the type of antenna (yagi, whip, dipole, etc)

Your suggestions and why?

Regards

Pheezy

 

[davenn]

well you need a dipole or a whip then. Both will have low gain between 1 and ~2.4 dBi

A Yagi is not omni-directional

Dave

 

[jiripolivka]

well you need a dipole or a whip then. Both will have low gain between 1 and ~2.4 dBi

A Yagi is not omni-directional

Dave

From your data I do not see why you need an omnidirectional antenna. To communicate with one particular terminal, you should prefer a directional antenna. Such antenna will also suppress interfering signals from other directions.

To design your antenna you need to calculate with the system pArameters.
1. Transmitter output power (yours and opposite terminal - take the lowest value of both)
2. Receiver noise figure on each side (take the highest of both), and RF bandwidth, to estimate the "noise floor"
3. Distance between antennas, to calculate propagation loss.
4. Required gain of both antennas to achieve signal-to-noise ratio >20 dB for a good error rate.

From the above system analysis get the antenna gain you need. If the gain is > 3 dB, you need a good directional antenna.
Check "www.l-com.com" for more information, they sell good antennas, too.
If you need a gain of 10 dB, use a dipole with a corner reflector. You can use a chicken wire mesh or perforated sheet to make a good antenna for a low cost.
Practical hints: Check also antenna polarization and install your antenna so you can adjust the height. Tin roofs and close objects cause reflections and can affect your error rate

 

[davenn]

don't quite me ... I didn't ask the question
quote the OP


cheers
Dave