Varactor-Tuned Lumped-Element Circulators (Correspondence)

In the case of lumped-element circulators, the center frequency of the device can be tuned by altering the lumped capacitance only. It is the purpose of this paper to describe a new voltage-tuned circulator which is obtained by replacing the usual lumped capacitances by varactor diodes. Such a circulator has been tuned over an octave band from 250 to 500 MHz.