Dielectric constant characterization of large-area substrates in millimeter wave band

A possibility of the dielectric constant epsilon' measurement for substrates with permittivity epsilon = epsilon' + i epsilon'' without an essential restriction on their area has been shown experimentally. The method uses frequency measurement of quasioptical, dielectric resonator (QDR) with two dole oriented along the QDR radius with a dielectric substrate in one of them. Taking QDR of teflon in 8mm waveband as an example it is found that measurable values of epsilon' can ran up 15 epsilon(q)', where epsilon(q)' is the QDR material permittivity. Absolute error of the measurements is determined by an accuracy with which the permittivity of calibrated (standard) samples is known. The relative measuring error is determined by the accuracy of the QDR frequency measurement and can be quite a small. As an example the method is demonstrated for LaAlO3 single crystals.