A Novel Magnetless Nonreciprocal Differential Filtering Isolator With Common‐Mode Suppression

This paper presents a novel magnetless nonreciprocal differential filtering isolator with common‐mode (CM) suppression. The proposed differential isolator comprises a six‐port differential filtering coupling network and a nonreciprocal active path, enabling differential‐mode (DM) low‐loss forward transmission and high reverse isolation while preserving CM suppression. The embedded filtering sections introduce two transmission zeros to enhance frequency selectivity without additional resonators. A mixed‐mode S ‐parameter analysis is developed to clarify the isolation mechanism and stability condition. A fabricated prototype exhibits a forward DM insertion loss of 0.14 dB at 2.43 GHz, a 3‐dB fractional bandwidth of 6.98%, a 20‐dB DM reverse isolation bandwidth of approximately 100 MHz, a peak isolation of 50 dB, and greater than 40 dB CM suppression.