Integrated self-biased hexaferrite microstrip circulators for millimeter-wavelength applications

• Published in: IEEE transactions on microwave theory and techniques Vol. 49; no. 2; pp. 385 - 387
• Main Authors: Oliver, S.A., Shi, P., McGruer, N.E., Vittoria, C., Hu, W., How, H., McKnight, S.W., Zavracky, P.M.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-02-2001; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Bonding; Ceramic bonding; Ceramics; Circuits; Circulation; Circulators; Dielectric losses; Glass; Insertion loss; Integrated circuit metallization; Integrated circuit yield; Metallizing; Microstrip; Networks; Noise levels; Silicon; Strontium
• ISSN: 0018-9480; 1557-9670
• DOI: 10.1109/22.903102

Planar microstrip Y-junction circulators have been fabricated from metallized 130-/spl mu/m-thick self-biased strontium hexaferrite ceramic die, and then bonded onto silicon die to yield integrated circulator circuits. The impedance matching networks needed to transform the low-impedance circulator outputs were deployed on low-loss alumina or glass dielectrics to minimize circuit losses. These magnetically self-biased circulators show a normalized isolation and insertion loss of 33 and 2.8 dB, respectively, and a 1% bandwidth for an isolation of 20 dB. Application of small (H<1.5 kOe) magnetic bias fields improved the isolation and insertion loss values to 50 and 1.6 dB, respectively. This design may form the basis for future monolithic millimeter-wave integrated circulator circuits that do not require magnets.