[time-nuts] OT: Levelled sine wave generator

[Didier]

Dave,

You may want to look at the SG-503 Tektronix plug-in for a levelled sine
generator. It goes to 250 MHz, and the full service manual with schematics
is on my web site in the Manuals pages:

http://www.ko4bb.com/cgi-bin/manuals.pl

I have one and it works as advertised. Great for scope calibration, not so
great as a signal generator :-)

Didier KO4BB 

> -----Original Message-----
> From: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] On Behalf Of David C. Partridge
> Sent: Monday, December 15, 2008 4:04 AM
> To: 'Discussion of precise time and frequency measurement'
> Subject: [time-nuts] OT: Levelled sine wave generator
> 
> Sort of related, but only just - however the signal to noise 
> ratio here is so good that I feel impelled to ask.
> 
> For 'scope calibration I'm considering building a levelled 
> sine wave generator.
> 
> Ideally the specs I'm looking for are:
> 
>  o Close to DC (10kHz or 100kHz would be fine) up to at least 1GHz.
>  	more would be better but not critical
> 
>  o Output levels from 0.5Vp-p(-2dBm) to at least 
> 4Vp-p(+16dBm) into 50R
> 	 (up to >6Vp-p(say +20dBm) would be better)
> 
>  o Output flatness levelled within 2% of desired output level 
> (+/- 0.086dB)
> 	across the entire frequency range at the final 
> connector to the DUT
> 	This will almost certainly mean an external levelling head.
> 
>  o Modulation - not critical, FM or AM might be useful.
> 
>  o A logarithmic sweep capability might be nice, but isn't necessary.
> 
>  o Frequency display - nice to have but output to external 
> counter is OK.
> 
> Generating the basic signal is probably just a case of using 
> something like an HP VTO-8200, mixing it with 2GHz 
> (Mini-Circuits RMS30?), low pass filter, an AGC stage (see 
> below) and then amplify probably using an MMIC like the 
> Mini-Circuits ERA-2SM followed by an additional stage to get 
> the extra few
> dB.   For more accurate frequency control some sort of 
> synthesiser locked to
> a reference might be in order (I had to get a time-nuts hook 
> in here somehow).
> 
> The question is what should go in the sensor head?
> 
> Logically I need to sample a proportion of the signal 
> delivered to the output connector, compare the output of the 
> sensor against a DC reference level telling it the desired 
> output level, and feed back a voltage to a
> wideband AGC stage (any suggestions for this?) in the main 
> unit.   I also
> need to be able to detect that output is not levelled.
> 
> Or should I just forget the whole idea and go talk to R&S 
> with a large cheque in hand?
> 
> Cheers
> Dave
> 
> 
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