On 6/30/23 2:07 PM, Leif M wrote:
I hope this is not a silly question, but where do you need GDO, if you have a VNA? That is, you can measure coils and capacitors with VNA. Measuring resonance frequency is bit harder, because Q gets easily too low, and it depends on firmware how you can find the resonance.
It's hard to measure an assembled trap (or measure self resonance of a coil) with traditional 1 or 2 port fixtures, because the fixture is part of the system. I suppose you could develop some appropriate calibration loads (equiv to Short, Open, Load) to "dembed" the fixture.
But if what you're interested is resonant frequency, then a "loosely coupled" coil hooked to the VNA to measure S11 works pretty well. The loose coupling reduces the loading from the measurement system, and you can support the unit under test well away from other "stuff".
We've used a similar technique at JPL to measure the resonance and Q of a microwave cavity at cryogenic temperatures. You can fill the cavity with, say, liquid methane, or ethane, or mixtures of them, and measure the EM properties. The cavity has two loop probes and we make multiple measurements as the probe orientation changes, and from that can calculate the effect of the probe.
(Why? Because oceans on Titan are likely liquid methane, ethane, etc)
