Abstract
A novel sum and difference (SD) conical beam-scanning reflector antenna is proposed in this paper. The reflector surface, illuminated by two omnidirectional horns, is a body of revolution obtained by revolving the generating parabola about a symmetry axis. The horns stacked along the symmetry axis of the reflector are fed by a nest coaxial waveguide. Teflon lens is used to improve the side lobe levels and reflection coefficients of the feed horns. By tilting the generating parabola and using the offset feeding method, two conical beams, with different beam pointing angles, were generated. A compact feed network was also designed to feed the two horns, which includes two rectangular TE10 mode-to-coaxial TEM mode transitions and a Magic-T to implement SD beams. The scanning performance of conical beams can be achieved by mechanically moving the feed antennas along the symmetry axis and taking full advantage of offset focus characteristic of the parabolic reflector. The error in angle measurement was also discussed. The SD conical beam-scanning antenna was formed by a parabolic dish with a radius of 18 λ operating at 24 GHz. The proposed antenna was designed, simulated, and fabricated. The measured results show that the difference beam null-depth is -25 dB and the sum beam gain is 15 dBi at 40°. The sum beam gain varies by less than 1.5 dB across the scan coverage from 30.8° to 45.2°. The measured results are found to be in good agreement with the simulated ones.
Highlights
Of late, much attention has been paid to conical beam antennas, because they are good candidates for satellite communication, target detection, tracking or guiding system, and so on
The results show that the sum beam gain varies by less than 1.5 dB, across the scan coverage
The results show that the designed antenna can achieve high-gain sum and difference (SD) conical beam-scanning
Summary
Much attention has been paid to conical beam antennas, because they are good candidates for satellite communication, target detection, tracking or guiding system, and so on. In [15], [16], nested horn antenna is proposed to produce conical beams with different beam-pointing angles by controlling the diameters of coaxial waveguide horn and circular waveguide horn. A comparator network was designed to coordinate with the horns and reflecting surface and to produce the high-gain SD conical beams. The measured gain of the sum conical beam, with 40◦ beam-pointing angle, was 15 dBi, whereas the null depth of the difference conical beams could reach −25 dB at 24 GHz. Moving the feed horns along the symmetry axis allowed the sum conical beam to be scanned from 30.8◦ to 45.2◦. Moving the feed horns along the symmetry axis allowed the sum conical beam to be scanned from 30.8◦ to 45.2◦ This structure can make full use of the antenna aperture to obtain higher aperture efficiency and is easy to fabricate at K band
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