New theoretical concept for wide band gyromagnetic devices

In a circulator, the bandwidth is related to the difference of circularly polarized permeabilities of ferrite and the nonreciprocal filling factor which is defined in this paper. The relation is obtained for a general circulator. The measured methods and measured values of the nonreciprocal filling factor are shown for several types of circulators. Wide-band method is to use additional lossless networks such as a lumped circuit and λ/4 transformers. The second is to increase the energy for the same phase excitation. These techniques are described together with their experimental results. Using the latter technique, the arbitral value of the backward loss can be obtained, and an extremely wide-band isolator covering 3 octaves in the UHF band is shown as a practical example.