Design of VHF lumped-element circulator

Includes bibliographical references (pages 72-78)This thesis discusses the ferrite circulator, theory of operation of the Y-junction and the derivation of the junction inductance of the lumped-element circulator. A three port lumped- element circulator was designed as an on-reciprocal transformer for operation in the VHF region of the r.f.spectrum and is described. Wire coiled around the ferrite was used as a Y-junction to give junction inductance. Circulator parameters such as the saturation magnetization of ferrite, the diameter of the ferrite disc, number of turns of wire in the coil and the externally applied magnetic field were varied one at a time and extensive tests were performed at various frequencies. Lumped-parameter capacitance was used to tune the resonator. The device was tested for bandwidth availability at frequencies where optimum performance was noted. The experimental data was tabulated and used to establish design curves and to compare the device's electrical characteristics such as the voltage standing wave ratio, forward insertion loss, isolation and bandwidth with the calculated values. Factors possibly contributing to discrepancies in theoretical and experimental results are indicated and discussed at the end of the thesis