David C. Partridge wrote: > 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 > The phase noise wont be particularly low especially for low output frequencies.
A diode double balanced mixer with dc current applied to the IF port is useful as a wideband current controlled AGC device. NB mixer IF response must extend to dc. Bruce _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
