I have a N9010A spec an with N9063A analog demodulation and N9064 VXA signal analyzer software installed. I am trying to use the spec an to demodulate a phase modulated signal and send it out the BNC analog out port. The signal is a short duration pulse with a low duty cycle. The problem is that the spec an sends noise out the back port when the signal is not present (in between pulses) and the noise waveform is larger peak to peak than the signal waveform is. This makes it difficult/impossible to catch the signal on an o-scope or capture the data in the signal.
*Is there a way to make the spec an analog out only output a signal if there is a signal coming in or if the input power is past a certain threshold?* I've tried the RF Burst setting under the Trigger menu, and this triggers the display just fine when a pulse comes, but the Analog Out port still puts out noise when no signal is present. Thanks for your help.
*Is there a way to make the spec an analog out only output a signal if there is a signal coming in or if the input power is past a certain threshold?* I've tried the RF Burst setting under the Trigger menu, and this triggers the display just fine when a pulse comes, but the Analog Out port still puts out noise when no signal is present. Thanks for your help.
The N9063A Analog Demodulation measurement application uses a software demodulator to make its metrics measurements. It is the output of that demodulator that you see in the Demod Waveform window. But the Analog Out port, when it is providing the Demod Audio signal, is making use of a hardware demodulator. The reason for the difference is that the Demod Audio signal will also be fed to the audio amplifier and from there to the speaker and headphone jack, and this signal needs to be real-time.
The software demodulator is more flexible and more accurate, but is not real-time.
The hardware demodulator is real-time, but is not calibrated. Also, since the hardware demodulator sets the gain of the Demod Audio signal based upon a short (time-wise) acquisition, if the burst is not present at the time of the acquisition, the gain will be set very high, causing the noise that you see. The hardware demodulator was not intended to be used for bursted signals.
Also, the Demod Audio signal may have a DC offset (depending upon which of two Digital IFs are installed) and the demodulated waveform may be clipped in some cases. This is part of the uncalibrated nature of the Demod Audio signal.
If you want to capture the demodulated waveform, I suggest querying the Demod Waveform data using the FETCh:PM2, FETCh:PM3, FETCh:PM4, or FETCh:PM5 SCPI command, depending upon whether you want the demod minimum, demod maximum, demod, or demod average trace data.
There is no way to cause the Demod Audio signal to only appear when a signal is present at the analyzer input or is above a certain threshold.
Regards -