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A new approach for in‐band radar cross section (RCS) reduction of microstrip patch antenna with preserved radiation features is presented. This aim is achieved by the application of highly absorbing unit cells optimized by particle swarm optimization around the radiating patch of the reference antenna. More than 10 dB in‐band RCS reduction is observed from 2.5 GHz to 3 GHz for both x‐ and y‐polarizations with a −26.4 dB maximum RCS reduction at 2.8 GHz, according to measurement results. A close agreement between the measured and the simulated results shows that the proposed absorbing unit cell is a good candidate to enhance antenna in‐band stealth performance. In addition, with a comparative table, it has been shown that the proposed antenna has much lower in‐band RCS and is more compact than the other antennas proposed in previous literature. The basic benefit of this study is to achieve maximum in‐band RCS reduction, especially at the exact desired frequency without long‐term simulations and time‐consuming design studies. [ABSTRACT FROM AUTHOR]

In this study, the use of Split Ring Resonator SRR metamaterial (MM) lens for Ku band micro-strip patch antenna directivity gain improvement is shown. In order to obtain the focus in the Ku band, a SRR metamaterial lens with a negative refractive index in the same band is designed and placed in the half-wavelength distance of the reference antenna in the radial direction, and the simulation and measurement results are obtained separately. Thus, a 1.52 dBi increase in the directivity gain of the reference antenna is shown according to measurement results. In this study, the same dielectric materials are used for the substrate and superstrate, so that the beneficial effect of the lens layer on the directivity gain improvement is shown more clearly. Moreover, for the low antenna profile, the total size of the MM lens layer is almost the same as the patch size of the reference antenna. Another advantage of this study over other similar studies in the literature is the use of a lens layer consisting of a smaller number of metamaterial unit cells. [ABSTRACT FROM AUTHOR]