A study on the feeding system for the tapered-slot-antenna having ultra broadband characteristics and its array

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A tapered slot antenna (TSA) has been investigated by many researchers, because a TSA has several advantages such as high gain, wide bandwidth and simple configuration. Recently, a TSA using an orthogonal feeding technique (O-TSA) has been proposed as a useful element antenna for a TSA array. This type of antenna is constructed in such a way that the TSA element is set perpendicular to the substrate for a feeding network. An array antenna composed of these newly designed O-TSA elements enables the realization of a simple feeding system for a large-scale TSA array. The usual O-TSA element is, however, fed by a microstrip line. It is thought that an O-TSA element fed by a microstrip line will show high cross-polarization characteristics because of unwanted radiation from its feeding system. Therefore, new types of O-TSA elements, in which the feeding systems are constructed by a coplanar waveguide (CPW), are proposed in this study. In order to verify the performances of these antennas, s … More ome O-TSA samples were constructed and tested at the SHF-band. The experimental results showed that the test antennas performed well in terms of both radiation pattern and return-loss characteristics. Next, the new type of O-TSA element using a dual feeding technique was proposed in this study. The two O-TSA elements in this dual feeding system are coupled electromagnetically via one coupling slot to the feeding line. The feeding system of this newly designed O-TSA element was constructed by using a micostrip line. Impedance matching between the dual TSA element and the feeding system was achieved by controlling the length of open stub in the transition. The array antenna using these dual O-TSA elements enables the realization of a simple feeding system for a large-scale TSA array. The optimum geometrical parameters were determined experimentally, and the antennas were made of a usual Teflon fiberglass substrate. The broadband returnloss was achieved in the test antenna using a dual feeding technique. Symmetrical radiation patterns were also obtained for the test antenna. The cross-polarization levels of the antenna were suppressed to below-25 dB in the boresight direction. The peak gain was about 10 dBi in this test antenna. The experimental results confirmed that the proposed O-TSA elements performed well in terms of both radiation patern and returnloss characteristics. Therefore, these O-TSA elements are considered to be useful antenna for a large-scale TSA array. Less