Abstract
The design of a 112-element millimeter-wave waveguide slot array antenna to reduce the grating lobe level is presented. A hybrid-phase feeding technique combining a cophase feed and an alternating-phase feed is applied to facilitate the suppression of grating lobes. In addition, a stepped feed waveguide and offset coupling slots aligned in a line are employed to realize a tapered aperture distribution. As a result, grating lobe suppression of 8.1 dB was achieved on the diagonal planes compared to a conventional alternating-phase-fed waveguide slot array antenna. A prototype of the proposed antenna was fabricated and measured. The measured results show that the proposed antenna exhibits a −15 dB reflection bandwidth of 3.4%and an average realized gain of 26.72 dBi within the measured frequency range. Good agreement between the simulated and measured radiation patterns is also observed.
Highlights
Waveguide slot array antennas have been excellent candidates for commercial and military applications in millimeter-wave frequency bands due to their advantages of high efficiency, high gain, and precise control of the aperture distribution [1,2,3]
A well-known and accurate design procedure for linear and planar arrays of the longitudinal slots on waveguides was developed by Elliott [4,5,6], taking into account external and internal mutual coupling effects
The alternating-phase displacement displays more broadband characteristics, the slot arrays are associated with the disadvantage of exhibiting undesirable −18 dB grating lobes on the diagonal planes [11]
Summary
Waveguide slot array antennas have been excellent candidates for commercial and military applications in millimeter-wave frequency bands due to their advantages of high efficiency, high gain, and precise control of the aperture distribution [1,2,3]. In order to demonstrate the feasibility of the proposed hybrid-phase feeding technique to reduce the grating lobe, a comparison with a waveguide slot array antenna fed by the conventional alternating-phase feed is conducted with Chebyshev aperture tapering of 25 dB. NAdltthhoeugphroapo2s5eddBanCthenebnyashatevf0taopneritnhge was applied, the conventional alternating-phase-fed slot array antenna produces a high grating lobe level of −17.2 dB at θ = ±63∘. The grating lobe level of the proposed waveguide slot array antenna incorporating the hybridphase feed is decreased to −25.3 dB, which is 8.1 dB lower than the conventional alternating-phase-fed antenna. The broadside gains of the proposed antenna are slightly higher than those of the conventional alternating-phase-fed antenna
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