logbook
Electrical
- Sep 8, 2003
- 764
I thought I had understood waveguide offsets (an empty waveguide spacer section) to estimate mismatch errors, but it seems I was over-confident. I bought a quarter wave offset waveguide section to reverse the mismatch error in my scalar measurement system and therefore give me an uncertainty limit. But if the mismatch phasor is at right angles to the incident phasor, 180 degrees on the mismatch gives the same scalar answer!
I guess that is why calibration kits have lamda/8, lamda/4 and 3 lamda/8 offsets. It looks like any single offset can always be phased up to give no change at all between the normal and offset readings. Hence I would need to use at least two offsets.
Is there some simple rule concerning the use of offsets and the resulting scalar changes in the measured quantity?
I guess that is why calibration kits have lamda/8, lamda/4 and 3 lamda/8 offsets. It looks like any single offset can always be phased up to give no change at all between the normal and offset readings. Hence I would need to use at least two offsets.
Is there some simple rule concerning the use of offsets and the resulting scalar changes in the measured quantity?