Dual frequency dual circular polarization fusion antenna for microwave and millimeter wave applications

A dual-band dual-circularly polarized aperturesharing slot antenna with a large frequency ratio is investigated, based on the substrate integrated waveguide (SIW) technology. The overall structure comprises a SIW slot antenna working in the millimeter waveband, which also serves as the top patch of a microwave SIW radiation cavity. The SIW slot antenna employs a $2 \times 2$ SIW slot array unit and employs a sequential rotation process to achieve broadband circular polarization of millimeter wave. The microwave SIW radiation cavity antenna realizes CP radiation by loading two pairs of asymmetric shorting vias. Firstly, a series of short-circuit vias arranged in a diagonal configuration are introduced to construct two symmetrical Quarter mode substrate integrated waveguide (QMSIW) cavities. Subsequently, four short-circuit vias are positioned along the remaining diagonal in order to merge the two distinct orthogonal resonant modes (QM-TE110 and QMT-E220) within the QMSIW cavity, thereby facilitating the generation of circularly polarized radiation. With this design method, the proposed antenna can achieve dual-band CP operation and high aperture reuse efficiency. Besides, the microwave segment adopts differential feeding and 180° sequential rotation units, which can present low cross polarization due to reduce the coupling between two QMISW cavity.