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How To Lower Noise&VSWR In Distributed Amplifier?

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liuzhili

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I found that In my distributed amplifier,the VSWR is very High,if I try to low it ,the noise will rise,How can I do? Is there any way to lower the VSWR at the same time lower the noise?
Thank you very much.
 

You might want to tell more about what did you do to lower the VSWR, perhaps others can see are there rooms for improvement.

Standard advises would be check the matching and grounding.
 

also

happy123 said:
You might want to tell more about what did you do to lower the VSWR, perhaps others can see are there rooms for improvement.

Standard advises would be check the matching and grounding.
Click to expand...

Right...

maybe the info about frequency range, used Tr tech, and special constraints.. etc.
 

It is not a good idea to obtain knowledge, while hiding your own ones...
 

input line

The noise is a function of the input line impedance and the number of active devices. The minimum noise is a function like 1 +kN where N is the number of stages and k is a function of many other device and line parameters.

The optimum input line impedance reduces value as N is increased.

This means that you probably will not get the lowest F with any reasonable line Z. Your best bet would be to design for minimum noise and the put some impedance transforming network at the input of the amplifier to make the impedance the outside world sees.
 

Try to use active terminations

One effective way to reduce noise, especially at very low frequency: MHz, and get the required VSWR is to use active terminations for the gate and the drain. You can achieve the required rf equivalent resistance (tipically 50 ohm) with lower noise than a resistance with equivalent value.
 

Input VSWR is same well to noise ,but sometime there is no chance to get the optimize in the best output VSWR and best NF in the same time when you use just only one level transistor.

Normally,feedback circuit can get more NF.
 

liuzhili said:
I found that In my distributed amplifier,the VSWR is very High,if I try to low it ,the noise will rise,How can I do? Is there any way to lower the VSWR at the same time lower the noise?
Thank you very much.
Click to expand...

try to put coil from source to gnd.
it will change the gama opt ,
look that your s21 is became lower, and your stability became unstability
 

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