Abstract
In this paper we describe the design, theory, implementation, and measurement results of a novel frequency-scanned slow-wave slotted waveguide antenna. The slow-wave antenna is fabricated by periodically loading a standard WR22 waveguide using cylindrical posts. The antenna has a backward radiation and can steer the beam from −72° to −12° by changing the frequency from 32.5 GHz to 37.4 GHz. The gain of the antenna remains within a 3 dB range from the maximum gain of 17 dBi throughout the steering range. The antenna is $29 \lambda $ in length and $0.69 \lambda $ in width. The antenna radiation efficiency is between 74% and 92% throughout its frequency range which allows for further extension of its length in order to achieve a higher gain and a smaller beamwidth. Moreover, the small lateral width of the antenna allows placing several of them side-by-side to either narrow or facilitate scanning the beam in the transverse plane. The antenna has a fast and constant scanning rate of 4.3° over a 1% bandwidth and a return loss of less than −10 dB throughout its operating frequency range.
Highlights
The need for electrical beam-steerable antennas at millimeter and sub-millimeter wave frequencies is growing due to their expanding applications in different fields such as high data-rate communication, high-resolution radars, imaging systems, etc. [1]–[4]
The antenna can be used for applications that need 2D beam-steering and narrow beamwidth in the E and H planes owing to its small lateral profile and high efficiency respectively
The antenna can steer the beam from −72◦ to −12◦ when the frequency is changed from 32.5 GHz to 37.4 GHz
Summary
The need for electrical beam-steerable antennas at millimeter and sub-millimeter wave frequencies is growing due to their expanding applications in different fields such as high data-rate communication, high-resolution radars, imaging systems, etc. [1]–[4]. Another way to achieve a narrow beamwidth in both the E and H planes is to make a low-loss, slow-wave structure in a periodic waveguide with a small lateral profile Using this method, one can increase the dynamics of the propagation constant and achieve a large steering angle within a desired bandwidth by tailoring the dispersion relation. Since the wave is assumed to be concentrated in the middle of the waveguide cross-section as it propagates, we can further simplify the structure by extending the widths of the strips to reach the side walls of the waveguide to form diaphragms (as shown in Fig. 5), without considerably changing the dispersion relation and the fields modal configuration. The analytically calculated eigenmode solution for the simplified structure with diaphragms can be used to explain both the dispersion relation and the modal field configuration with hybrid mode in the designed waveguide with cylindrical posts.
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