Hexagonal ferrites for self-biasing circulators integrated in LTCC microwave modules

Abstract

Next-generation microwave LTCC modules for satellite communication systems require the integration of passive components including circulators to manipulate electromagnetic signals at high frequency. Substituted M-type hexagonal ferrites (Ba/Sr)ScxFe12−xO19 are applied as self-biasing microwave magnetic materials at frequencies of about 30 GHz. The ferrites are integrated into LTCC multilayer devices as sintered drop-in bulk samples. Sintered ferrites with preferential orientation of grains were fabricated by compaction of powders in a magnetic field and sintering at 1300 °C. Alternatively, screen-printed ferrite films were dried in an external magnetic field, and cofired at 900 °C. The magnetic texture of the ferrites is characterized using XRD, EBSD, and magnetic measurements. Integrated Y-type circulators were tested and exhibit non-reciprocal behavior. This indicates that hexagonal ferrites are promising candidates for self-biasing circulators embedded in LTCC microwave modules operating at Ka-band frequencies at around 30 GHz.