Design and measurement of microstrip ferrite coupled line circulators

The design of microstrip ferrite coupled line (MFCL) circulators using normal mode theory and the first proof-of-principle experiments are described. The longitudinally magnetized ferrite slab is positioned on top of a pair of microstrip lines to form the FCL and this is used with a T-junction and a novel hybrid coupler to form a three-port and a four-port circulator, respectively. The results show MFCL circulator behavior for the first time, and impedance levels and discontinuities are discussed. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 121–130, 2001

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