Microwave VCO Oscillator

In this video, we are going to take a look at a microwave VCO oscillator that can be tuned from 700MHz to . The design uses an active device, in common emitter configuration, and a variable tuned phasing network. The phasing network is tuned using three varactos diode, spreading the capacitance variation across the network. Oscillation is maintained by the S21 transfer of the active device. Unlike a negative impedance oscillator, this topology has greater phase performance, because the contribution of phase shift from the active device is smaller. 00:16 - Introduction 00:46 - Negative Impedance Oscillators 01:26 - Oscillators using two port devices 03:11 - Circuit description 05:42 - Usage for signal generators 06:57 - Final considerations Matjaz also use this topology with an interdigital microstrip resonator, providing greater phase noise and higher maximum frequency. An interdigital phase network can provide higher phase shift than 360degrees, making the contribution of the low Q phase shift of the active device low. The topology shown was first published by Matjaž Vidmar.