Practical design of wide-stopband filters utilizing asymmetric circulators

Wide-stopband filters in which the stopbands extend two octaves of the fundamental transmission frequencies have been realized in terms of asymmetrical Y-junction circulator designs. These filters have been tested at microwave frequencies from 0.05 to 18 GHz. The calculated biasing field requirement, insertion loss, isolation, and stopband frequency range are in reasonable agreement with the corresponding measured values. Since this filter is an off-resonant device, high power handling capability may be assumed. The filters show two octaves of stopband and, hence, can be used extensively as stopband filters in radome applications.<>