About RF conditioning
I am quite new to RF conditioning. In order to solve the problems like BTS co-location or in other cases, which has a tighter requirements on certain bands, my task is to specify the duplexer/triplexer or the additional filter specifications. So I wonder if some of you who are familiar with this can provide some suggestion or advice on the rules to follow. It is better some book or slides can be provided.
Thanks a ton!
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I think, you cannot change the duplex spacing as the standard specifies duplex spacing for each band. may be you will be needing additional filters . For that you need to check for spurious and out of band components and check with standard specification. Find out how much they are exceeding the limits and make or buy filters according to that.
http://www.powerwave.com/basestationfilter.asp
This is related to system design.
You can restrict the unwanted or condition at various levels like Duplexer and filter after LNA, filter before and after mixer, Digital filters after ADC, filter before demodulation.
You can fix for the one if you know the rest as it is cascaded effect.
yes, that is right. Here I get another question that if I have found out how much they are exceeding the limits, then how can we get/ caculate the specifications of the filter? would you please set an example?
As Kspalla wrote , if you are a designer you can correct for the unwanted frequencies at different stages. But if you are converting an existing system to some other band you have only duplexer and additional filters to play with.
how much rejection you need ... say you have a spuious at 2300 MHz which is above limit by 6 dB. you may need a band pass filter which passes ur desired frequency band and has a rejection of atleast 9db (including an additional 3dB margin) at 2300 MHz. If you can find the source of spurious and reduce there itself it will be the best method .
Based on the application let say it need to qualify the ETSI standard.
You know when it fails for out off band blocker requirement.
From this you will find the required attenuation at various offsets.
Hope this information helps you.
yes, that hits the point. My task is mainly related to converting an existing system to certain requirements in some bands. and thanks for the examples.
I tried to search some materials about RF conditioning, but it is really difficult, especially those contain a lot of practical examples.
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