Amplification of RF signal

[amirke]

Hi,

I need to amplify RF signal.

After Receive it goes to LNA with amplification of 15-20dB.
I need to be able to amplify it from 30dB to 60dB.

What is better to do
To take the signal to a VGA of -10dB to 30dB and then to power amplifier or vice verse ?

or in other words, what is the preferable stage before the antenna : VGA or PA ?

Amir

 

[vfone]

If the system is a transmitter, the PA must be the last stage, before the antenna.

 

[jiripolivka]

You give not enough information to get a reliable answer. If you are building a receiver, operation frequency is needed, RF bandwidth, dynamic range, and more.

 

[amirke]

Hey jiripolivka ,

I am asking general question. for every sort of frequency.
I specifically build a PCS and GSM repeater.

I just asked to determine that the final stage before transmitting to the antenna is PA, not VGA.

Thanks

 

[jiripolivka]

Hey jiripolivka ,

I am asking general question. for every sort of frequency.
I specifically build a PCS and GSM repeater.

I just asked to determine that the final stage before transmitting to the antenna is PA, not VGA.

Thanks

For any particular application you should know and specify important parameters.

If you build a repeater, then it has certain center frequency at which it receives, and another or the same (if you use time multiplexing) on which it repeats.
So youd system consists of a receiver and a transmitter.
To design a receiver, one needs to know the bandwidth and noise figure (determining the noise floor), a maximum output power in a linear operation, filtering (to counter interference and crosstalk by adjacent channels); to equalize receiver output power, VGA gain range, AGC response, etc.
To design a transmitter, usually the output power and its control is important, efficiency and antenna matching.

You gave nothing of the above, so do not expect someone to invent all important details.

 

[maurymw]

Rf small-signal amps (as compared to power amplifiers) find many uses around the stereo store as well as in the area. Sometimes, an increased indication level is required to work a analyze device such as a regularity reverse or service observe.

 

[amirke]

Thanks guys.

I understand that final stage before antenna transmitting RF must be a PA.

jiripolivka,
I said that I am workin with GSM and PCS, which has a clear definition of center frequencies and band width.
I just wanted to ask about the correct amplifier in the last stage.
What do you mean by AGC response ? can you give an example ?

Maurymw,
I don't understand your answer .

 

[vfone]

You already got the answer. The PA is the last stage before the antenna, and the VGA is driving the PA.

 

[amirke]

You already got the answer. The PA is the last stage before the antenna, and the VGA is driving the PA.

Yes Vfone.
I understood. I wrote this as well.

Thanks