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

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.