High-Isolation Three-Port Self-Biased Spherical Circulator with Corrugation in Air Waveguide Technology

This paper presents the design and analysis of a three-port, high-isolation, self-biased spherical circulator using air waveguide technology. The spherical geometry minimizes port coupling, and the corrugation improves isolation across the desired frequency band, while quarter-wavelength impedance matching reduces insertion loss. Integrated with an antenna, the circulator maintains the radiation pattern and achieves high isolation between transmitter and receiver, making it suitable for automotive radar applications. Furthermore, its application in MIMO radar as a compact transceiver array, effectively halving antenna count by enabling shared transmit-receive functionality is introduced. Advanced signal processing techniques are used to manage the virtual array, enhancing angle resolution despite side lobe challenges. This setup achieves high angular discrimination and compactness, demonstrating a strong potential for automotive radar systems.