Optimization of antenna aperture distribution with ground reflection

✍ Scribed by Hirohisa Tajima

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 645 KB
• Volume: 79
• Category: Article
• ISSN: 8756-6621
• DOI: 10.1002/ecja.4410790405

✦ Synopsis

In general, the radiation pattern in the vertical plane of an antenna requiring a low elevation angle coverage is made to have sharp cutoff characteristics so that the reduction of the electric field intensity by ground reflection, known as "the lobbing effect," can be avoided. However, the lobbing effect depends on the installation of height of the antenna, and therefore the determination of the optimal antenna pattern for a certain installation environment is difficult.

In this paper, an aperture distribution that takes into consideration the ground reflection is optimized in the case where the height of the top of the DME/P antenna for distance measurement of MLS for aircraft landing is restricted to 3 m. The aperture distribution was evaluated by the minimum values of the electric field intensity at many sampling points around the required coverage area in the presence of ground reflection. The optimization was carried out by maximizing these minimum values using the steepest descent method. As a result, the minimum values of the electric field intensity within the covered region became uniform so that the electric field distribution was improved. In the optimized aperture distribution, the phase center of the antenna is shifted to the upper part of the aperture so that the lowest electric field intensity at the lower coverage edge was improved by 6.5 dB.