Best isolation is via a piece of fiber optics. Don Bruce Griffiths > Lux, James P wrote: >>> Actually, it depends on the distance from the hot carrier, the >>> amplitude >>> of the hot carrier and the particular VNA in question. My VNA allows me >>> to change filters as well as integration time. >>> >> >> And especially, where is the selectivity in the VNA's receiver? You >> might >> have a 10 Hz filter, but if the receiver's front end is wide open, then >> the >> dynamic range requirement might be a challenge to meet. >> >> Consider a 30 dB gain amplifier claiming 120dB reverse isolation.. >> >> You put in -30dBm and get 0dBm out in the forward direction. Meanwhile, >> you >> inject 0dBm into the output of the amplifier (from the VNA) and you >> expect >> to see -120dBm appearing at the input. Depending on how good the >> directional coupler/bridge is that feed the port 1 reflected power >> receiver, >> you might be facing measuring a -120dBm signal next to a -30dBm signal, >> which is challenging... >> >> Assuming the DUT is linear (hah!) one could just apply load with >> different >> reflection coefficients to it when measuring S11. This might even be >> harder, though... With -120dBm reverse isolation, you're basically >> looking >> at seeing the effect of adding a coherent signal 90 dB down to the >> signal >> you're already measuring for S11. That's not going to result in a huge >> change in amplitude or phase (e.g. About 1 part in 1E4 or 1E5).. >> >> Maybe for this list, though.. Measuring phase shifts of 1E-5 radian.. >> Walk >> in the park, as it were. >> >> Jim >> >> >> _______________________________________________ >> 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. >> >> > Jim > > Its even more challenging when the isolation amplifier has a nominal > gain of 0dB coupled with a reverse isolation of 120dB or more. > In this case one would be looking at measuring phase shifts on the order > of 1urad or less. > > In this case one could try applying say a +10dBm signal to the input, > modulate the load reflection coefficient and look for a modulation > frequency related sideband at the input port. > > 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. >
-- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com _______________________________________________ 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.
