Hello,
Let us assume we have a cellular antenna. I consider the frequency 800 MHz. I want to co-locate next to my antenna GNSS and SDARS antennas. The 2nd and 3rd harmonics of 800 MHz fall in the L1 band of GPS and SDARS range, respectively. What considerations must be taken regarding the isolation between antennas? is it enough to have a large isolation, or would I need ,too, to have a strong attenuation at the 1600 and 2400 MHz?
Thank you1
1- Isolation, as detailed in document presented by Mohamed Azab
2- Upon application: if application is very sensitive for any spurious in the workng frequency band, some more attenuation is required for unwanted signals.
Montaha,
Adding to the colleagues above, i would like to comment your question from the fundamental point of view. You have three antennas which lay near to each other,
One transmit antennas and two receiving antennas. Every antenna has its own port to connect it to its rf front end. Assume these ports are P1,P2,and P3, respectively.
If the antennas are coupled, you can measure the coupling between them by the transmission coefficients S21,and S31 with antenna 1 is the transmitting antenna. In order to measure how far the antennas are isolated from each other you have to measure S21 and S31 at the intended frequency.
As isolation between antennas increase, S21 and S31 will get smaller. For complete isolation S21 and S31 will be zero and the attenuation will be infinity.
So, things are put in its context.
Best wishes
Thank you M. Azab, M. Jaamour, M. Zekry for taking the time to answer my question.
The ITU document (mainly dealing with isolation between antennas in BS) is interesting, but unfortunately it does not bring the answer to my question especially about the harmonics. I needed more information about the contribution of filtering, in addition to the antenna isolation, to avoid any desensitization of receivers.
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