Novel method of DRO frequency tuning with varactor diode

A novel method of electrical frequency tuning for a dielectric resonator oscillator is presented. The idea is to place an opened lambda /4 line, with a varactor diode at one end, onto the screw for frequency tuning which is above the dielectric resonator. The central frequency offset achieved with the DRO realised at 14 GHz was 4 MHz, while the change of RF power was less than 0.5 dBm.