Forums › SM Series Discussions › SM200C Phase Noise with pulsed input
- This topic has 2 replies, 2 voices, and was last updated 5 years ago by rpettingill. 
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 rpettingillParticipant- I am trying to test out the SM200C phase noise measurement capability when the input is a pulsed waveform (5 microsecond pulse with 100 microsecond PRI, 5GHz waveform). I keep getting the “Carrier Not Found” message. I have verified the pulse looks correct on the spectrum analyzer mode, the IQ data mode, as well as using other test equipment to verify its integrity. - In Spike on the Phase Noise page, I have the carrier freq set to 5.0 GHz, and I have played around a ton with the Ampl Thresh setting. - Is the SM200C capable of performing Phase Noise Analysis on this type of signal? If yes, what are some troubleshooting steps to get rid of the “Carrier Not Found” message?  
 AndrewModerator- rpettingill, - No the Spike software is not capable of measuring phase noise on a pulsed signal. There is no synchronization mechanism built in to software to synchronize to a pulse. Additionally, the measurement duration can be > 1 second depending on what phase noise offsets are selected. You wouldn’t be able to get much resolution on a 5us pulse. - If possible, I would recommend using a CW output on your transmitter, or you would need to roll your own phase noise measurement using our API or trying to capture the pulse in zero-span and post-processing the captured I/Q waveform. - Regards, 
 Andrew
 rpettingillParticipant- Okay. Sounds good. Thank you! 
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