On Broadband Antenna Arrays

Broadband antenna array is a research hot in the antenna design field. For a traditional antenna array, wideband characteristic is realized by using volume-type wideband antenna as its element and reducing the coupling between array elements at the same time. The tightly coupled antenna array(TCA) is a new kind of wideband antenna array. The TCA takes the advantage of the coupling between array elements, employs miniaturized narrowband cell, and has small array spacing. It can solve the contradiction between the coupling and the pattern grating lobes. Although the theoretical analysis of TCA is relatively mature, its application in practice has not yet invested extensively. This is because in the transition from theory to large-scale applications, there are still a lot of difficulties to be resolved, such as the truncation effect along with array back-end processing and so on. In this paper, a tightly coupled antenna array is proposed. The antenan has the characteristics of broadband(3.5 frequency multiplication), wide scanning angle domain(±45), and dual-polarization. Moreover, since there is no additional matching dielectric layer, the whole antenna array has the merit of low-profile, light weight and ease of fabrication. Specifically, the major contributions of this thesis are summarized as follows:1. The element of a infinite array and a 4×7 TCA are designed. The treatment of the edge truncation effect is studied. The 4×7 TCA is fabricated and measured based on the simulation model. The results show that the tightly coupled array maintain active VSWR?3 overall the operation range, even when the scanning angle reached 45°.2. A four-way powerdivider working from 100 MHz to 350 MHz is presented. Due to the low working frequency range, it is inappropriate to use the microstrip line when designing the powerdivider. The 4-way splitter is designed using the high permeability material. It has the advantages of small volume and light weight. It is fabricated and measured. The measured results satisfy performance requirement with VSWR?1.4, isolation less than 20 d B, amplitude balance better than 0.5d B and phase balance better than 3°.