Study Of The Hourglass Reflector Antenna With Shaped Beam

The far-field pattern analysis and synthesis of the hourglass reflector antenna are presented. As the groundwork, far-field characteristics of the hourglass reflector antenna are studied by Physical Optical (PO) method. Then beam shaping of the hourglass reflector antenna is investigated by an array optimization, a reflector shape synthesis or/and a hybrid method using the real-coded genetic algorithm (RGA).Pattern characteristics of the hourglass reflector antenna are discussed for on-focus and off-focus feed. When the feed is located on the focus, the effects of different radius of rotation R, F/D ratio and edge taper ET on the far-field patterns are discussed. And when the feed is positioned away from the focus, some of the key distortion characteristics of reflectors are presented for both the axial (Zf) and lateral (Xf, Yf) feed defocusings.Based on the radiation characteristics analysis of the hourglass reflector antenna, the synthesis of radiation patterns is studied.First of all, the excitation of feed array elements is optimized to shape far-field patterns. For instance, a pencil or/and a cosecant-squared beam in the horizontal plane is achieved with a 7-element circular array feed. Because only patterns in the horizontal plane can be shaped with a circular array feed, a nonplanar array feed is introduced. And a pencil or/and a rectangle beam is obtained by controlling the element excitation of a 5×7-element array, validated the nonplanar array feed.Then, the patterns in the elevation plane are shaped using shaped reflector. In this thesis, the reflector surface is described by Bernstein or/and Jacobi-Fourier polynomials, and the expansion coefficients are optimized to achieve a cosecant-squared and a flat pattern in the elevation plane. Also, the implementation of these two surface descriptions is compared, and the advantages and disadvantages are summarized.Finally, the array optimization and the shape synthesis are combined to realize patterns shaping both in the elevation plane and horizontal plane at the same time.