EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Leo Bodnar on November 04, 2018, 04:59:50 pm
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I am using E4435B as a voltage controlled reference source in phase noise test set . Typical set up - DC coupled FM modulation mode with control voltgae fed into Ext.1 input.
However, I have found this in the manual:
EFC Lock, Off / On (ESG-AP and ESG-DP Models)
This softkey enables an Electronic Frequency Control mode that is for use with phase noise systems.
It is provided for use by service personnel only.
Softkey Location: Utility > Instrument Adjustments > Reference Oscillator Adjustment > EFC Lock Off On
Relevant part of the service manual shows that internal 10MHz OCXO can be tuned with "EFC CONTROL" voltage, which would be perfect way of injecting PLL steering voltage from the phase noise testset.
The question is where is the input port for "EFC CONTROL"? Any ideas?
Cheers
Leo
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Why aren't you using phase modulation to inject phase noise into the output signal? The advantage is that the base frequency doesn't change. When using FM modulation with DC coupling you'll get a (tiny) frequency offset which may not be what you want.
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Why aren't you using phase modulation to inject phase noise into the output signal?
I am tracking quadrature condition in the phase detector, not injecting phase noise.
(http://hpmemoryproject.org/pict/technics/3048/diag_pd.jpg) (http://hpmemoryproject.org/technics/bench/3048/basic_01.htm#two_source)
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The A11 reference block diagram in the service guide E4400-90335 shows the EFC control input coming from MOD1
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I can only find MOD1_OPAMP which is, I assume, buffered MOD1 input (EXT 1 INPUT BNC jack on the front panel.)
So if this is right, OCXO offset can be controlled by turning EFC Lock = On and keeping modulation turned off.
EXT 1 INPUT needs to be in DC coupling mode as well.
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That would also be my conclusion.
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I have just tried it and it works indeed like expected.
Thanks
Leo