International Symposium on Antennas and Propagation


Session Number:4C35



Non-Iterative Design of a Waveguide Slot Array with Baffles to Realize Admittance of an Isolated Slot

Takehito Suzuki,  Jiro Hirokawa,  Makoto Ando,  


Publication Date:2008/10/27

Online ISSN:2188-5079


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In design of a waveguide slot array, it is important to take the effect of the external mutual couplings into account because they are large [1], [2]. The analysis including the mutual couplings has received much attention in literatures for more than fifty years [3]. Control of the mutual couplings is so difficult that various kinds of the analysis and design methods have been proposed. In [1] and [2], the design procedures were iterative, where the slot parameters were modified by calculating active admittances in the presence of mutual couplings in order to produce a desired far field pattern . The evaluation of mutual couplings was more time-consuming for a larger number of the slots. In [4], the design procedure with fast convergence was proposed to design a planar array with the feeding part of the tilting slots. This procedure had an advantage of the low variations of the mutual couplings between shunt slots for the offset and the length. In the design of the radiating parts for the single-layer slotted waveguide array antennas [5], [6], the slot unit model to simulate the mutual couplings for an two-dimensional infinite periodic array, was used to determine the initial values of the slot parameters for a desired distribution [7]. The slot parameters were compensated iteratively until realizing the desired excitation by introducing a finite number of magnetic currents at the both sides of the one-dimensional array in the external region. The iterations were required because the situation of the external mutual couplings was different between the infinite periodic array for the initial values and the finite one for the compensations. This paper proposes the non-iterative design of a waveguide slot array with baffles [9] or cavities, shown in Figs. 1 and 2, where their sizes are determined so that the active admittance of each slot is equal to the admittance of an isolated slot with same dimension. In other words, the baffles or the cavities are designed not to affect the external mutual couplings to the slot(s) inside them at all. The baffle region or the cavity region acts as a choke and its surface is open-circuited. Furthermore, we find the size of the baffles or the cavities which is independent on the slot coupling except very strong one. The size is not needed to be changed for the slot coupling, which makes the design simple. This non-iterative design can realize a desired excitation easily. This method is adopted for two types of excitations; a uniform distribution and a Taylor one with -35 dB sidelobes.