Design of frequency selective surface superstrates for scanning microstrip patch array antenna

Abstract

We investigate the directivity, sidelobe level (SLL) and maximum radiation angle characteristics of a frequency selective surface (FSS) superstrate placed above a 5 X 1 patch array antenna for different scan angles. We find that the frequency at which a high directivity is achieved moves higher as the scan angle of the array is increased, and that the size of the original FSS superstrate needs to be increased along the direction of the scan angle, in comparison to that of the broadside case (0 degrees), to effectively enhance the directivity and suppress the SLL. A. rectangular FSS superstrate with enlarged dimension in the scan direction is proposed, and the radiation patterns of the original and elongated FSS composites are compared. For a 20 degrees scan angle of the array antenna, the directivity, and the SLL of the changed FSS composite are enhanced by 1.3 and 3.9 dB, respectively, relative to those of the original FSS composite. We compare and summarize the results,for the directivity and SLL characteristics of four different antenna prototypes, namely a single antenna; a conventional 5 X 1 array antenna; the FSS antenna composite with a single patch antenna; and an FSS array composite comprising of a 5 X I array antenna designed for a scan angle of 0 degrees. (c) 2007 Wiley Periodicals, Inc.