94 GHz Substrate Integrated Waveguide Dual-Circular-Polarization Shared-Aperture Parallel-Plate Long-Slot Array Antenna With Low Sidelobe Level

In this paper, a 94 GHz substrate integrated waveguide (SIW) parallel-plate long-slot array antenna is presented, which is able to generate dual-circular-polarization (CP) low sidelobe level (SLL) beams from a single radiating aperture. This antenna consists of two layers of substrates. One is used to construct the unequal feeding network and the other is used to construct a 15 × 15 shared-aperture parallel-plate long-slot array antenna. This multilayer topology has a smaller size compared with the single-layer design. A simple and feasible method is applied to control the radiation pattern, which is able to realize dual-CP low SLL beams without a complicated feeding network. Two 1-D sixteen-way unequal dividers are employed to suppress the SLL in two planes of a CP array. Then, a 90° coupler is employed in the feeding network to switch the polarization modes between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). Finally, a prototype of SIW parallel-plate long-slot array antenna is fabricated. Simulation and measured results show that SLLs of the fabricated antenna are under -18.5 dB in two planes.