Millimeter-Wave Co-Polarized In-Band Full-Duplex Antenna Based on a Mode Superposition Method

In this article, a novel mode superposition method is proposed to implement a millimeter-wave (MMW) shared-radiator co-polarized in-band full-duplex (IBFD) antenna at 29 GHz. The proposed method is realized based on a dielectric resonator antenna (DRA). By simultaneously exciting the TM01 delta and HEM21 delta modes of a DRA, a superposed mode with a field pattern analogous to the TE211 mode can be produced. Since both the transmitter (TX) and the receiver (RX) ports locate at the weak-field regions of the superposed mode, a decoupling performance is therefore obtained without the use of any additional decoupling structures or circuits. For validation, a DRA with artificial electromagnetic boundaries (AEMBs) is employed, so that the TM01 delta and HEM21 delta modes can be simultaneously excited using a simple microstrip proximity coupling. It only needs to properly adjust the geometric parameters of the DRA, and the mutual coupling is substantially suppressed. The experiment demonstrates that the antenna can achieve maximum isolation of 42 dB and peak gain of 8.65 dBi. Due to the simple and integrated architecture, the proposed method is promising for MMW IBFD applications.