An integrated miniaturized self-biased circulator based on the low-temperature D2W bonding technique

A high-quality, high-yield integration of oriented M-type thick ferrite film with a SiC substrate through a simple and robust low-temperature thermocompression bonding technique is reported, solving the issue that ferrite devices, particularly ferrite circulators, cannot be integrated with planar RF circuits. Based on this bonding technique, a miniaturized self-biased circulator is successfully integrated onto a SiC substrate. This circulator, measuring 3.0 mm × 2.8 mm and operating at 35 GHz, exhibits a relatively low insertion loss of 1.2 dB, a bandwidth of 2.5 GHz, and a maximum isolation of 17 dB.