Determining the value of reference air capacitors at high frequencies

Conclusions

Reference three-terminal capacitors are affected by frequencies to a greater extent than the two-terminal capacitors and, therefore, the range of their application is limited to several megahertz.

The effect of distributed parameters appears in air capacitors with a rising frequency, thus raising their inductance measured at a high frequency as compared with its low-frequency value. The extent of this difference depends on the capacitor's design features and nominal value. The maximum difference amounts to about 20%.

The applicability limit of (1), which corresponds to the simple equivalent circuit of the capacitor (Fig. 1) and is used for calculating its effective value, depends on the tolerated error in determining that value and on the capacitor's parameters. For an error of 1% the value of the frequency correction ω²LC_o must not exceed 10%, and this approximately corresponds to the upper frequency boundary of 1/3 of the capacitor's natural resonant frequency.