[time-nuts] 35601A as stand-in for 11848A ?

SAIDJACK at aol.com SAIDJACK at aol.com
Sat Jan 5 19:15:49 EST 2008


 
In a message dated 1/5/2008 15:31:00 Pacific Standard Time,  
bruce.griffiths at xtra.co.nz writes:

>Thats why its phase noise floor is relatively  high.
>Saturating both mixer ports and using a capacitive IF port  termination
>should achieve a lower phase noise floor.
>The  tradeoff is that careful calibration of the mixer phase  sensitivity
>frequency response needs to be done.
>However the  offset frequency limit for such techniques is about 50KHz or  
so.

>Bruce



Hi Bruce, John,
 
thanks for the hints, I don't have much time right now, but some feedback  to 
the questions:
 
I am using resistive 50 Ohms termination out of the IF port, then followed  
by an inductive input 1.5MHz  LC filter.
 
I will try to AC couple the 50 Ohm termination and see if that helps.
 
The PLL works fine, and the noise floor doesn't change when I connect  it to 
the OCXO or if I leave the EFC input to the reference disconnected  and the 
OCXO EFC input just terminated, so I am quite sure that's not causing  the issue.
 
The reference is a Wenzel Ultra low Noise OCXO with a noise floor  
<-170dBc/Hz.

I am trying the setup using an E1938A DUT. The noise floor out of the  Mixer 
is about -120dBc/Hz, way too high. Tried other sources with known noise  
floors of about -160dBc/Hz as well, similar results.
 
Will write more later,
bye,
Said
 
 



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