Dear All,
it is my first post here on AAC, I hope I am not infringing any forum rule
I am trying to measure by an Vector Network Analyzer (Agilent n9914) the turn ratio of an air-core auto transformer in a frequency range 30kH - 30MHz, since I am looking for some series resonance and voltage overshoot (it may sounds weird but it is an exercise I am doing for another purpose).
The schematic is attached.
I am comparing the value I computed with transmission line model (see first data series in "result") with measured data.
I performed a first comparison applying V1 by a signal generator and measuring the gain V2/V1 by an oscilloscope, see data series "Meas. Oscill" in the same picture. The resonance was confirmed.
Next, I wanted to perform this tedious task by a network analyzer, to have a nice and smooth characteristic swept over the whole frequency range of interest.
The idea is computing the scattering matrix of the auto transformer, seen as a double port element. After performing the matrix, I converted it to the ABCD matrix, since V2/V1 is equivalent to 1/A. The result that I get is the dark orange data-series in the picture "results".
The trend is followed at higher frequency (I get a peak and a valley), despite the agreement is poor (but I already saw by the oscilloscope that I compute the overvoltage well). I am doubting of the results I am getting from the oscilloscope, since the 1/A increases at lower frequency, which does not make sense at all (increasing turn ratio at low frequency?? I do not expect any resonance there).
Do you have any comment, suggestions?
Of course I performed the calibration of the network analyzer before performing my test. Besides, I using the same COAX connection both for the oscilloscope and the network analyzer measurements, so the coil terminals should not matter.
Cheers,
Andrea
it is my first post here on AAC, I hope I am not infringing any forum rule
I am trying to measure by an Vector Network Analyzer (Agilent n9914) the turn ratio of an air-core auto transformer in a frequency range 30kH - 30MHz, since I am looking for some series resonance and voltage overshoot (it may sounds weird but it is an exercise I am doing for another purpose).
The schematic is attached.
I am comparing the value I computed with transmission line model (see first data series in "result") with measured data.
I performed a first comparison applying V1 by a signal generator and measuring the gain V2/V1 by an oscilloscope, see data series "Meas. Oscill" in the same picture. The resonance was confirmed.
Next, I wanted to perform this tedious task by a network analyzer, to have a nice and smooth characteristic swept over the whole frequency range of interest.
The idea is computing the scattering matrix of the auto transformer, seen as a double port element. After performing the matrix, I converted it to the ABCD matrix, since V2/V1 is equivalent to 1/A. The result that I get is the dark orange data-series in the picture "results".
The trend is followed at higher frequency (I get a peak and a valley), despite the agreement is poor (but I already saw by the oscilloscope that I compute the overvoltage well). I am doubting of the results I am getting from the oscilloscope, since the 1/A increases at lower frequency, which does not make sense at all (increasing turn ratio at low frequency?? I do not expect any resonance there).
Do you have any comment, suggestions?
Of course I performed the calibration of the network analyzer before performing my test. Besides, I using the same COAX connection both for the oscilloscope and the network analyzer measurements, so the coil terminals should not matter.
Cheers,
Andrea
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