Phase Locked BWO System for Open Resonator Measurement in D-Band

The combination of a D-Band phase-locked backward-wave oscillator (BWO) with a spectrum analyzer for measurement of permittivity and low loss-tangent is presented. For measuring low loss tangent material, such as CVD diamond and high purity semi-insulating (
HPSI
) 4
H
-SiC , at millimeter wave ranges, it is necessary to precisely measure an increase of a few kHz in a line-width of 200 kHz. We describe a phase-locked loop with frequency conversion that combines a BWO source and a microwave spectrum analyzer to obtain line-width measurements with less than 2 kHz (less than 1%) standard deviation in D-Band millimeter wave.