Development of a Multi-Shaped Beam Antenna in C-Band

Abstract

This paper describes the development of a 4 GHz transmit antenna generating six shaped beams for covering main areas of Africa. Design and optimisation, hardware activities and performance data are presented. Two polarisation sensitive gridded single offset reflectors (diameter 2..15 m) are fed by two orthogonally polarised feed arrays with 16 and 20 feeds respectively. The antenna generates three independent beams for each polarisation. Frequency reuse by polarisation diversity and by space diversity between two far displaced beams allows for 30 channels in total to be transmitted. A flexible channel to beam allocation is possible (reconfiguration) with a slightly reduced channel number. The three horizontally polarised beams are partly overlappling with five of the 16 feeds to be shared. These feeds are excited via dual mode subnetworks. This feedsystem consisting of 16 compact, high efficiency SCRIMP-Horns, a dual mode beam forming network in barline technique has been manufactured and tested. Measurement results are compared with pattern predictions on the level of primary as well as secondary pattern. The correspondence is in both cases very close. Mutual, coupling between horns has been included exactly into the analysis. This is mandatory for a realistic cross-polar prediction as it is demonstrated by comparison with the measurements.

Hexagonal-Shaped Broadband Compact Scrimp Horn Antenna for Operation in $C$-Band

“…An optimization tool based on the BoR-FDTD solver coupled with a genetic algorithm is applied to Scrimp horns first presented in [11] and [12]. The proposed tool is applied to optimize several antennas with different aperture sizes while minimizing the antenna size and satisfying the given performance requirements of Table I.…”

“…1(b)] is placed at the mouth of the horn with a depth of and it is extended until the antenna aperture . The operating principle of the this antenna is based on the excitation and mixing of higher order modes with the fundamental mode in order to generate low cross-polarization levels [11], [12].…”

“…To optimize the proposed antenna structure, an in-house optimization tool based on a genetic algorithm coupled with Body of Revolution FDTD (BoR-FDTD) method is employed [12].…”

“…Another interesting compact horn configuration, known as Short Circular Ring-loaded horn with Minimized cross-Polarization (Scrimp) horn, was introduced in the late 1990s [11], [12]. Experimental results for a multifeed satellite system showed excellent performance for a horn aperture size of .…”

“…The main characteristics of optimized Scrimp horn antennas are reported for different antenna aperture sizes in Section II. An in-house finite-difference time-domain (FDTD) technique has been used for the optimization [12]. A compact hexagonal-shaped Scrimp horn is presented in Section III for a better integration into a focal array system with a hexagonal lattice.…”