[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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