A Compact Low-Profile Multilayer Log-Periodic Metasurface Patch Antenna With Broadside Radiation

A multilayer log-periodic metasurface patch antenna (LPMPA) operating in the 4-9-GHz frequency range with broadside radiation is presented. This antenna array is characterized by its compact size and low profile. Each element of the LPMPA consists of a 2-D periodic structure of 4 & times; 4 square patches, which can be viewed as a metasurface. The array is excited through aperture coupling in the ground plane beneath the radiators. The proper phase progression of the currents for a broadside radiation of the LPMPA ' s elements in the active region is obtained by increasing the length of the feed line placed between adjacent radiators. The structure ' s stop-band caused by the excess of length between radiators is eliminated by increasing the characteristic impedance of the feed line to 70 Omega in the proximity of each slot. A prototype of the proposed antenna, consisting of four 2-D periodic structures, is fabricated and tested. The obtained results show a 76% fractional bandwidth with gain ranges between 8 and 13 dB.