Indus-1 RF circulator bias control system

Different approach has been adopted here to keep the circulator tune to the working frequency with the change in the temperature. This is a noble scheme in which processing on the phase difference between forward and reflected signal is done rather then the amplitude. Use of this scheme does not requires the direction sensing of the corrector coil current. This scheme detects the phase difference between the Reflected and the forward signal using the phase detector SRA 1WH and the proper operating point selection gives the advantage of higher sensitivity and the direction sensing depending upon the shift from resonance frequency. Current through correcting coil is made to flow using integrator control to keep to circulator tuned to resonance frequency this system is designed in such a way that it keeps the circulator close to the resonance even if the RF is off so that as soon as the RF is switched on reflected power does not increase too much. This is a general scheme which is independent of frequency and the make of the circulator therefore it can be used with any circulator at any frequency range with the proper selection of the phase shifter and the phase detector. (author)