A Compact Millimeter-Wave Planar Directional Coupled Crossover With a Wide Bandwidth

A compact planar directional coupled crossover with a wide fractional bandwidth is proposed in this letter, which is composed of overlapping planar 3-dB couplers based on the substrate integrated waveguide (SIW) and stripline techniques. In the proposed structure, the TE10 mode and TEM mode can be transmitted simultaneously without any interaction, which is helpful to design and integrate the SIW and stripline couplers for realizing a wideband directional coupled crossover with a compact footprint. A prototype with a center frequency of 26 GHz for 5G applications is designed and fabricated. The experimental results show that the measured crossover has high isolation among all ports and good directional coupling performance in orthogonal directions. The proposed crossover has a compact footprint and low loss, which can be a good candidate for developing the miniature feeding networks for multiple beam antennas.