Maximum Bandwidth Performance for an Ideal Lumped-Element Circulator

A procedure based on the analytical model of a lumpedelement, crossover circulator has been developed to maximize its operating bandwidth. The procedure considers the circulator as a network and employs the circulation impedance - the load associated with perfect circulation - as a metric to optimize the bandwidth. Using this procedure, we find that a maximum 194% bandwidth can be obtained for an ideal circulator for any above-FMR range operation. By applying this same procedure to an actual circulator device in 225-400 MHz frequency range, we achieve a 125% bandwidth from a numerical simulation model. We have verified this result from the measurement of a fabricated device; the measured data reveals a bandwidth of 129%.