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A slot array in substrate‐integrated waveguide (SIW) technology fed by a microstrip Rotman lens is proposed. This compact multibeam antenna is designed in two layers using a novel transition based on double‐stepped coupling slots on the broad wall of SIWs. Compared with a rectangular transverse coupling slot, this transition is broadband and its coupling power can be controlled for low‐sidelobe applications. The radiating part is a 10 × 10 slot array and the beam‐forming network can generate seven beams with good coverage from −30° to 30° in the azimuthal plane. To validate the proposed concept, an antenna prototype is implemented at 10 GHz. The frequency response and measured radiation patterns are in good agreement with simulated results provided by full wave simulation software. Experimental results show that the sidelobe level is lower than −21 dB for the central beam in both H and E planes and better than −18 dB for the edge beams.

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An X-band dual-polarized Vivaldi antenna with high isolation is proposed. The procedure of this antenna design includes the conventional Vivaldi antenna with regular slot edge (RSE), the dual-polarized Vivaldi antenna with two Vivaldi antennas which have different feeding point positions in a cross-shaped form, and the two Vivaldi antennas with a galvanic contact in soldering point. By applying the RSE, it reduced the dimensions of the Vivaldi antenna and improved its radiation performance. The modified antenna is fabricated and measured. The measured results show that 11 < −10 dB at the entire X-band for the two Vivaldi antennas. The isolation ( 21) between the two feeding ports, which has been improved by applying the different feeding point positions and the galvanic contact in soldering point, is better than 34 dB at X-band. In addition, the cross-polarized discrimination is better than 21 dB for the two Vivaldi antennas, and the measured results also include the gain of two Vivaldi antennas.

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