Hi Klaus,Hi,
I´d look for a "power supply rejection ratio diagram" (PSRR)
Or for power supply (filter) recommendations .. and keep on them.
Talking about 1mV or 100mV ripple is useless without knowing the frequency (range).
In detail you also should know whether the 1mV or 100mV are for a single freqency, or a whole frequency range, how weighted, if it is RMS or PP...
Klaus
The first thing to check AM distortion. Power supply ripple mostly manifests itself as AM modulation on an input. You can apply a single tone input and look for sidebands (at the ripple frequency and its harmonics) in the vicinity of the tone frequency in a spectrum analyzer. Consider that it may be down to -80 dBc or below depending on the sensitivity of the DUT. Check the entire spectrum, check the ripple frequency and its harmonics.Is there any test I can conduct on the PA/LNA to see when that PA/LNA will be upset? If so, what exactly do I need to measure? phase noise?
Here is the LNA https://www.minicircuits.com/pdfs/ZFL-500LN+.pdfHi,
Generally, possibly, maybe, I´m guessing...
Why not giving exact informations:
* The exact type and manufacturer and device name
* a link to the datasheet
.. then we don´t need to guess and you get fast answers as precise as can be.
Klaus
Should the ripple's frequency range between 60 to 120Hz?The first think to check AM distortion. Power supply ripple mostly manifests itself as AM modulation on an input. You can apply a single tone input and look for sidebands (at the ripple frequency and its harmonics) in the vicinity of the tone frequency in a spectrum analyzer. Consider that it may be down to -80 dBc or below depending on the sensitivity of the DUT. Check the entire spectrum, check the ripple frequency and its harmonics.
The ripple may cause phase distortions/noise as well, it is another aspect, you should decide what kind of distortion is important for your application.
I'm thinking of adding a filtering capacitor as the last solution.if it is a concern, why not add some honking big capacitors to the DC bias lines? Add 100 uf in parallel with say a 1 uF ceramic cap, and that ripple will be much less.
and yes, ripple WILL show up as additive phase noise on a signal passing thru the amplifier. it will be a small effect, but sometimes you do not have that much tolerance for things like phase noise.
If the ripple is more sinusoidal in nature, the noise added will be more like a single tone phase modulation than actual pseudo random phase noise. Systems respond to a single tone phase modulator spur differently than they do to broadband phase noise
What means "our" and "fundamental tone".to capture our fundamental tone
Yes, I have a SignalHound that is able to measure the phase noise.well, back to the original question, do you have a phase noise test system?
if so send a clear signal through this amplifier, and measure the phase noise at the output of the amplifier (be careful to put a high power load on the amplifier, and measure the output after a directional coupler so you do not blow up your test equipment).
then come back here and post the phase noise result, AND tell us exactly what type of system you are trying to use this in, and we can comment further.
or another way to do it, if it is a communications system, run the system with the transmitter amplifier first run by the good lab supply, and then run by the power supply with ripple, and see if there is a significant increase in bit errors with the 2nd power supply.
Did you really connect the oscilloscope to the output of the amplifier?But, when I used the same setup connecting the oscilloscope instead of the spectrum anaylser, I got something terrible as you can see below
Sorry. It has been connected to the PS outputDid you really connect the oscilloscope to the output of the amplifier?
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