This Small Business Innovative Research Phase II project addresses the development of Innovative Ultra-Broadband Ferrite Circulators/Isolators. A conventional 3-port ferrite stripline junction circulator involves a low-Q ferrite stripline resonator so that at the circulation frequencies standing-wave resonant modes are excited dumping microwave energy from the input port to the output port but not the isolation port. Operation of a conventional ferrite circulator is nonreciprocal, and the transmission bandwidth is roughly proportional to the inverse of the Q-factor of the resonator, due to the standing-wave nature of the excited resonant modes. A new picture of ferrite-circulator operation utilizing traveling-wave coupling of microwave signals at the circulation frequencies haa been discovered. This is in contrast to the operation of the conventional circulators employing standing waves for coupling. As such, ultra-broadband operation of the circulators results, whose bandwidth has been measured in Phase I to cover from 1.6 to 16 GHz for a prototype device. It is not possible to acheive this bandwidth with a conventional circulator. This leads to a new generation of ferrite circulators or isolators. Using the LTCC technology facilitates mass production in large quantities. As such, generic microwave circulators and isolators can be fabricated at low costs suitable for universal applications covering across many frequency bands. Ferrite-circulator operation does not require a ferrite resonator anymore. This requirement has been constantly enforced by the operation of a conventional circulator for more than 50 years. There is always a tremendous need for circulators or isolators which are able to provide signal-path separation or protection over many frequency bands, as demanded by the measurement of a broadband signal and by a narrow electromagnetic pulse.
