|Image of the Splash plate reflector .|
The splash plate feed uses backfire radiation to illuminate the dish, and the feeder waveguide doubles as a feed/support structure (see the image below for an illustration of the feed element). This is a compact reflector topology with the feed positioned close to the main reflector requiring no additional support struts. Another advantage is that the feed antenna can be fed from behind the main reflector, reducing unwanted aperture blockage.
The Splash plate feed antenna used here is an intricate design consisting of a matching section inside the waveguide and dielectric lens which is designed with the feed plate for optimum dish illumination.
|Illustration of the Splash plate feed element.|
The Splash plate reflector can be compared with the Horn fed Cassegrain reflector...
already in Antenna Magus. The following image shows one of each of these antennas designed for the same primary dish diameter (0.4m) and F/D of 0.3 at 30 GHz. Note that the Cassgerain's feed horn intersects the primary reflector - Antenna Magus exports simulation models that include a small cut-out in the primary reflector to cater for this.
|A Splash plate and Cassegrain reflector design with primary dish diameter of 0.4m, F/D of 0.3 at 30 GHz.|
The graph below compares the radiation pattern results that were estimated in Antenna Magus. It is important to note that no struts are included in the Cassegrain analysis - these would introduce unwanted blockage, increase sidelobes and reduce performance in the actual antenna. The splash plate result shows better backlobe performance, but slightly higher sidelobes than the Cassegrain reflector - a small compromise to achieve a more compact and mechanically simpler design.
|Normalized gain comparison between the Cassegrain and Splash plate reflectors, designed for similar primary reflector size and F/D.|