Microwave VSWR Measurement on Oscilloscope
I have two choices:
one using VSWR Meter,other using CRO.
Can I apply the direct formula (SWR=maximum voltage/minimum voltage) to the square wave
displayed on CRO ?
But according to lab manual (SWR=Square root of maximum voltage/Square root of minimum
voltage). Why we are taking the square root ?
[img=../imgqa/eboard/Antenna/rf-yal4uyeszlk.jpg]
Taken the square root you will get a voltage that is proportional to the RMS voltage of the waveform.
You can use VSWR = (max measured voltage) / (min measured voltage) = (incident wave amplitude + reflected wave amplitude) / (incident wave amplitude - reflected wave amplitude)
Pancho you must be very very young ;) CRO = Cathode Ray Oscilloscope a very old term, much older than me and I feel ancient ;)
Dave
I'm relative old.
Thanks for teaching.
However why is CRO located in such place ?
Where is DUT ?
A Place where Detector Mount(XD-451) is located should be a place where DUT is located.
Even if places of Detector Mount(XD-451) and CRO are proper, what signal should we use as horizontal sweep signal for CRO ?
It is because VSWR meter uses square-detector.
Back to original question.
If you set up VSWR measurement system using Slotted-Line, Detector, DUT and Storage Oscilloscope correctly, you have to take root of a displayed wave since it is a square wave created by square-detector.
Please refer to this http://wireless.ictp.it/handbook/C3.pdf There is a setup for VSWR measurement.
This is a common TDR which every one knows.
The Designer's Guide Community Forum - Frequency Response using a TDR
Time-domain reflectometer - Wikipedia, the free encyclopedia
But I don't think a figure which a starter of this thread shows is for TDR, although there is a CRO.