RF amplifier problem, resonant? ET? equipment problem?
时间：04-09
整理：3721RD
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Hi everyone,
I am doing a 3.8G low power pre-amp
which also bandstop 900M,1.8M and 5.8M
everything is ok when using a network analyzer to check. Figure 1
(power = -10dBm), 15dB gain at 3.8G and there is already back off from P1dB
However, once i use Signal generator + spectrum analzyer to check the gain.
I realized there is also some "gain" for the noise floor too
my input was single carrier and power would be -10dBm(@1.9G). Figure 2
(the 3.8G is 2nd harmonics generated by my signal generator)
When i try to lower the carrier to -20~30dBm, the "noise floor gain" become less.
Figure 3
I am not sure whether it is a resonant or anything else.....
I am doing a 3.8G low power pre-amp
which also bandstop 900M,1.8M and 5.8M
everything is ok when using a network analyzer to check. Figure 1
(power = -10dBm), 15dB gain at 3.8G and there is already back off from P1dB
However, once i use Signal generator + spectrum analzyer to check the gain.
I realized there is also some "gain" for the noise floor too
my input was single carrier and power would be -10dBm(@1.9G). Figure 2
(the 3.8G is 2nd harmonics generated by my signal generator)
When i try to lower the carrier to -20~30dBm, the "noise floor gain" become less.
Figure 3
I am not sure whether it is a resonant or anything else.....
figure 2
figure 3
The observation is correct only, nothing to worry about it.
Check the power level of Sig Gen with SA with and with out the amplifier. The difference will give you the gain.
Make the simple setup with SA, like FC at 3.8GHz and span 10KHz RBW 1KHz etc. Then you will notice the same.