Re: Crystal detector with 10dB attenuator in series - is it for matching purposes?
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Very good! This what I was getting at.?
I have a little slide rule from HP that does the 20 LOG(1+rho1*rho2)^2? for the mismatch. Nice calculation tool. Helps when relating VSWR effects to amplitude ripple, especially in big system, where I started 50 years ago. I realize generator return loss degrades at higher frequency (what doesnt?).? J. Kruth
In a message dated 9/2/2024 6:44:52 PM Eastern Standard Time, jmrhzu@... writes:
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If it helps to add some numbers to all this then consider the case up around 22GHz where the sig gen source VSWR might be 1.8:1 typical.?
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This is poor enough to add significant mismatch uncertainty even if you connected it to a decent 26GHz power meter to calibrate the level. The sensor VSWR might be 1.2:1 at this frequency.
The poor source VSWR of the signal generator would give an overall mismatch uncertainty of +/- 0.23dB for the signal level calibration before it gets connected to the HP 8473C.
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If the input VSWR of the 8473C is 2:1 at 20GHz then the mismatch uncertainty is going to be about +/- 0.8dB when the sig gen is connected to it.
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However, if a decent isolating attenuator is used for the calibration stage, the source VSWR of the sig gen might be improved to 1.2:1.? Therefore, the calibration phase using the power meter would benefit from having the mismatch uncertainty reduced to about +/- 0.07dB.
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When the connection is then made to the 8473C the mismatch uncertainty (with the isolating attenuator ahead of it) should reduce to about +/- 0.27dB.
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In both cases, adding the isolation attenuator provides a substantial improvement in mismatch uncertainty.
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