Ka-band 32-GHz planar integrated switched-beam smart antenna

This paper presents an integrated planar switched-beam antenna based on rectangular waveguide antenna and Butler matrix network for beamforming, which is implemented by complementary-conducting-strip transmission line (CCS TL). The 32-GHz waveguide antenna with size of 71.5 mm by 4.1 mm, consisting of 20 slots in the broadside wall, is built on the Rogers RO4003 (ε_r = 3.38) substrate. For a compact and reliable design of the Butler matrix beamformer, the branch-line coupler and the crossover of the Butler matrix are designed by CCS TLs with characteristic impedance of 60 and 85 Ω, respectively. The proposed 4-beam smart antenna shows the steered beams in orthogonal direction at 38°, 76°, 106°, and 136°, respectively, and demonstrates a great potential for planar integration of smart antenna for wireless communication application. Measured results agree well with theoretical predictions, validating the design concepts employed in the millimeter-wave smart antenna design.