International Symposium on Antennas and Propagation
A Wideband Single-layer Slotted Waveguide Array with an Embedded Partially Corporate Feed
Shusuke Fujii, Yasuhiro Tsunemitsu, Goro Yoshida, Naohisa Goto, Miao Zhang, Jiro Hirokawa, Makoto Ando,
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Various wireless communication systems for millimetre wave band such as Fixed Wireless Access (FWA) have been developed. An alternating phase fed single-layer slotted waveguide array  as shown in Fig.1 consists of only two components, that is the slot plate and the base plate and they can be screwed together. It is one of the strong candidates for these systems because it has high gain, high efficiency and very low cost due to the simple structure. It works in travelling wave operation and the bandwidth is inversely proportional to the length of waveguide. Therefore, there is trade-off between directivity and bandwidth; the system specification can not always be met. Long line effects should be suppressed in two directions (2D) in the aperture; that is along the directions of the feed waveguide and the radiation waveguide. Partially corporate feeds for 1D suppression introduced in the end feed waveguide have already been reported . Our objective is to realize broadband single-layer slotted waveguide arrays by two-dimensionally embedding partially corporate feed in the aperture . Fig.2 (b) shows the structure of partially corporate feed embedded in the aperture. Whole the aperture is divided into 4 units. The number of cascaded cross junctions  and the length of radiation waveguide in each unit are reduced to 1/2 and the long line effect is suppressed two-dimensionally. In this paper, the bandwidth enhancement of the partially corporate feed is assessed in terms of array factor, by using the simplified model of the small dipole element, where the change of guide wavelength is taken into account. No slots are allocated over the embedded partially corporate feed and the blocking effects become notable as the corporate feed become widespread in comparison to the center feed as shown in Fig.2 (a). Large blocking area results in high side-lobe level and gain/efficiency reduction of the array. The basic design critelia for this unique array is proposed taking the blocking effects into account. E-plane coupler with acceptably small blocking width is proposed and the electromagnetic design is conducted . A small array with embedded partially corporate feed is fabricated and the basic operation is verified. The feasibility of partially corporate feed is confirmed . It is our future work to demonstrate the drastic bandwidth enhancement by testing a larger and higher gain arrays.