DESIGN AND MEASUREMENT OF NONUNIFORM FERRITE COUPLED LINE CIRCULATOR

Nonuniform ferrite coupled line constructed by placing section of corrugated coupled lines on longitudinally magnetized ferrite substrates is investigated. Unlike the usual uniform ferrite coupled line, the proposed nonuniform ferrite coupled line is corrugated with different cosinusoidal contours on the coupling slots. Compared with a standard ferrite coupled line designed at 7.6 GHz, the nonuniform ferrite coupled line based on the same ferrite substrate and of the same dimension is found to operate at a higher frequency. The center frequency of operation is up shifted by about 1 GHz. It is also found that the nonuniform ferrite coupled line has a broader bandwidth. The proposed nonuniform ferrite coupled line operates at the center frequency of 8.6 GHz with a bandwidth of about 26.7%, while the standard uniform ferrite coupled line operates at 7.6 GHz with a bandwidth of 14.5%. Two 3-port circulators are built by adding simple T-junctions to the uniform and the nonuniform ferrite coupled lines respectively. The measurements confirm the up shift in center frequency and the broadening in operating bandwidth of the nonuniform ferrite coupled line circulator.