"A study on design method of planar antenna having ultra broad-band characteristics"

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A triplate-type tapered slot antenna (T-TSA) presented here has low cross-polarization characteristics, since the T-TSA element is fed by a center conductor of the shielded triplate line to suppress the influence of an unwanted radiation. This type of a T-TSA,element is printed on both sides of a dielectric substrate and its feeding system consists of a triplate line. Test samples of the antenna were made of Teflon fiberglass substrates (epsilon _r=2.6, tan delta=0.0018, h=0.6mm). The radiation patterns on both E-and H-plane of the T-TSA element at X-band revealed high performances. The cross-polarization level of the T-TSA was suppressed to below-30dB at the boresight direction.The gain of the T-TSA element was higher than 6.8 dBi from 8 GHz to 12 GHz, with a peak level at 9.0 dBi. In the design of an array, it is important to estimate the mutual coupling between the T-TSA elements. As a result of experiment, the H-plane mutual coupling of this type of array was below-20 dB and that of the E-plane was about-15 dB when the element spacing d was 0.5lambda_o. The 4*4 element array was composed of these T-TSA elements. The experimental results of this array demonstrated high performance in both radiation pattern and gain characteristic. Therefor, the T-TSA is considered to be a promising element in an array antenna. Moreover, a wide band dual-polarized array antenna composed of T-TSA elements was also constructed and tested at X-band. An excellent isolation characteristic was achieved at both ports of the dual-polarized array.