Hi!
I have a general question. How to measure 100pF thin film capacitor Q-factor versus frequency in kHz - THz range? Using LC-tank would be narrowband and impractical.
The Q-factor is usually defined as the reciprocal of dielectric loss tangent. I operate an Agilent 4294A precision impedance analyzer. It gives directly a lot of impedance/dielectric parameters as a function of frequency (Range: 40 Hz - 110 MHz), including the dispersion of Q-factor. You can use impedance analyzers functional in the required frequency-regime.
I fully agree with Souvik Bhattacharjee to use Impedance analyser. There are other models you could use too not LCR.
Pecision impedance analyzer is surely a very good idea. The problem is what to do above 3GHz, which is typically the limit of such analyzers
Dear Filipp Baron , Yes, you are right. For this problem, there is a separate spectroscopic framework called Terahertz spectroscopy. This needs more sophisticated and expensive instruments, that can even deal with optical frequencies and can probe electronic polarization. But, the measurement scheme is similar.
Dear Souvik, thank you for pointing this out!
What quantity should I measure within the Terahertz spectroscopy framework? Is it S-, Z- parameters or something else? As far as I can see these quantities would let me resolve the resonances and extract Q-factor at those resonance frequencies by measuring resonance width at half peak height. However, what about the nonresonant frequency bands?
A related application note[1], including four methods:
1) Transmission/reflection line method,
2) Open ended coaxial probe method,
3) Free space method,
4) Resonant method,
might help you, dear Filipp Baron.
1. Measurement of Dielectric Material Properties (Application Note) https://cdn.rohde-schwarz.com/pws/dl_downloads/dl_application/00aps_undefined/RAC-0607-0019_1_5E.pdf
Dear Ioannis,
Thank you very much for your reference!
Yes, indeed, the first three techniques are very good for materials (dielectrics) Q-factor characterization. And the last techniques (the 4th) us suitable for narrow band Q-factor extraction of capacitor.
I should elaborate more on the specific details of the cap Q(f). The following usually contribute into it as the device rather than material: dielectric losses, metal skin depth, contact pads ohmic loss and inductance, distributed wave phenomena, EM radiation, plasmonic phenomena, others... Extraction and identification of relative magnitude of each of the above mechanisms would answer my original question exhaustively. So far, I could only think of numeric simulations in COMSOL to capture all those phenomena and try to fit the experimental curves of S-parameters. However, I would appreciate if someone could recommend non-simulations based experimental techniques to quantify individual physical mechanisms contributing into Q(f) dispersion.
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