Bridge Sampling Methods for Admittance Measurements from 500 kHz to 5 GHz

A two-channel time-domain sampler with common time base is used to compare voltages in coaxial lines driven by matched ratio arms from a pulse or sine-wave generator and terminated by unknown and reference admittances. Linear circuit analysis shows that the unknown can be determined from the bridge unbalance sampler outputs by simple calibrations of three frequency-dependent parameters. Design and uses of cells for dielectric measurements and reference terminations are described. Procedures for and results of test measurements are presented for time-domain measurements using a symmetrical power divider as ratio arms and for frequency-domain measurements using a 5O-Ω power splitter and 5-pF capacitative ratio arms.