Realization of coaxial reference air-lines as high frequency capacitance standard at CSIR-NPL

Abstract

The reported work has been carried out in the direction of establishment of metrological traceability of capacitance up to 200 MHz at CSIR-NPL. In this perspective, the set of seven coaxial reference air-lines (Type 900-LZ series) exhibiting capacitance values varying from 2 pF to 20 pF have been realized as a capacitance standard at high frequency (1 MHz–200 MHz). This is principally achieved with reference to the SI base units of the meter and the second. The standard value of capacitance of each of the reference air-line has been computed up to 1000 MHz by employing transmission line theory. The reference capacitance value of each of these air-lines has also been measured at 1 kHz which thereafter extrapolated up to 1000 MHz using resonance technique. RF impedance analyzer has been calibrated up to 200 MHz for capacitance using computed capacitance of reference air-lines as standard. The reported work will be helpful in establishing the calibration services for low value of capacitance standards in a frequency range from 1 MHz to 200 MHz at CSIR-NPL. The work will also bridge the gap between LF and RF impedance metrology.