[time-nuts] 8560E DC Coupling phase noise measurements
Loïc MOREAU
Loic.MOREAU at eai.fr
Wed Oct 26 09:53:01 UTC 2011
Thanks, everything is clear now.
I will have a try with a pair of Schottky diodes as 10 db give 3.16 attenuation and so no enough for a +-15V rails , I want to be sure ;=) )
Regards
Loïc
-----Message d'origine-----
De : time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] De la part de John Miles
Envoyé : mardi 25 octobre 2011 22:55
À : 'Discussion of precise time and frequency measurement'
Objet : Re: [time-nuts] 8560E DC Coupling phase noise measurements
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts- bounces at febo.com]
> On Behalf Of Loïc MOREAU
> Sent: Tuesday, October 25, 2011 1:01 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] 8560E DC Coupling phase noise measurements
>
> Hi,
> In the process of measuring phase noise with a 'demphano' gear, I am
> a
bit
> reluctant to connect my 8560E in DC mode to get 30 Hz low frequency
> sensitivity: the SA input is very sensitive to DC voltage and may be
> destroyed by a voltage larger than 200mV.
>
> So with a LNA having no blocking DC output I would like to know the
> best way to protect the SA.
>
> I suppose that putting a 100µF capacitor between LNA and SA is not
> especially a good idea as a charged capacitor to DC rail may have the
> same effect that no caps at all.
>
> I am looking for some advice in that domain to pursue phase noise
> measurements, for now I connect the SA with a caution after PLL lock
> and measuring the SA input with a DC voltmeter before switching to DC
> SA input but this mode of operation is a bit frightening.
>
> Any idea ?
The 200 mV limit is only with 0 dB of RF attenuation. With a quadrature PLL and LNA, you don't need to use 0 dB. 20 dB is probably OK, and if not, you can make up for it with more gain.
A pair of back-to-back Schottky diodes would be another alternative.
-- john
_______________________________________________
time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
More information about the time-nuts
mailing list