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In this article, a multi‐beam substrate integrated waveguide (SIW) leaky‐wave antenna (LWA) is proposed for millimeter‐wave radar applications, which owns the advantages of 2‐D scanning capability, high gain, low profile, and single layer configuration. The proposed antenna consists of a beam‐forming network (BFN) based on a 2‐D SIW parabolic reflector with eight waveguide feedings, and a 16‐element LWA array. The open‐stopband of the LWA is suppressed by employing a longitudinal slot into a conventional transverse slot LWA unit. In the E‐plane, the BFN can generate eight desired distributions of the amplitude and the phase gradients which steers beam from −17.3° to 30.8° with the crossover level higher than −5.22 dB. In the H‐plane, the frequency scanning LWA array can offer a continuous beam scanning range from −23° to 19° with operating frequency from 21 to 29 GHz. Finally, the antenna is prototyped and experimentally verified. The measured results are in accord with the simulated ones. The characteristics of the proposed antenna make it a very promising solution for applications in low‐cost millimeter‐wave radar systems.

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In this article, a low-profile and high-gain multi-beam antenna is proposed. The antenna consists of a cylindrical Luneburg lens based planar beamforming network, a folded double-layer guided-wave structure, and a leaky wave antenna (LWA) array. All the three parts are manufactured by 3D printing technology. The lens is realized by an nshaped gradual thickness unit to realize the refractive index variation of Luneburg lens in a parallel plate waveguide. The lens and the LWA array are folded into a double-layer guided wave structure, which transforms the planar wave from the flat Luneburg lens to the LWA array to realize the antenna miniaturization. The antenna is excited by a radially placed microstrip antenna array at the focal plane of the lens. The proposed antenna has seven beams with minimum −2.5 dB crossover level, and the scanning range is AE29 . The broadside gain is 19.8 dB, and the gain variation in scan range is 2.7 dB. The proposed antenna is fabricated and tested, and the measured results agree well with the simulated ones. Due to the advantages including low-profile, high aperture efficiency, high radiation efficiency, and low cost, the proposed design can find its applications in multi-beam radar and communication systems.