A high-efficience, low-phase error waveguide lens for a transform feed antenna
Abstract
A parallel-plate waveguide microwave lens, constructed as part of the concept development of completely overlapped subarray antennas, was tested. The lens' function is comparable to that of a Rotman lens with 16 inputs and 60 outputs. However, the input face is linear with uniformly spaced monopole elements, and the output face is circular, with monopole elements spaced uniformly in angle. Using a four-way power divider at the center four inputs connected to a line-source array, low sidelobe patterns were measured over a 22% bandwidth. Two major modifications to the antenna were required: (1) it is shown that when placed in an array, the phase center is closer to the monopole, the focal array was moved farther from the circular lens face to give good focusing at the center frequency; and (2) the mismatch and coupling properties of unequally spaced elements along the circular face varied enough to distort the amplitude taper, causing higher sidelobes, an optimum uniform spacing eliminated the problem, and is shown that it is possible, to find such a spacing that will not degrade the len's performance either as a beamformer or as a transform feed.
- Publication:
-
the 1984 Antenna Applications Symposium
- Pub Date:
- January 1985
- Bibcode:
- 1985anap.symp..235M
- Keywords:
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- Feed Systems;
- Lens Antennas;
- Lens Design;
- Microwave Frequencies;
- Waveguide Antennas;
- Antenna Design;
- Antenna Radiation Patterns;
- Microwave Equipment;
- Communications and Radar