In this paper, a novel hybrid metasurface (HMS) is proposed for reducing antenna RCS and maintaining the gain of the antenna. The HMS consists of a polarization-selective absorbing surface (PSAS) and an asymmetric transmission metasurface (ATMS). PSAS can absorb the in-band and out-of-band x-polarized waves, while completely transmitting y-polarized waves. The out-of-band y-polarized waves transmitting the PSAS is reflected by the ATMS with 90° polarization rotation when the ATMS is located under the PSAS, and the reflected wave is absorbed by the PSAS. The in-band y-polarized wave passing through the PSAS can completely pass through the ATMS and the antenna array. Thus the RCS reduction of the antenna can be achieved. Based on antenna reciprocity principle, the in-band y-polarized wave radiated by the metasurface lens antenna can completely pass through the HMS. The measurement results show that the antenna RCS is significantly reduced for x-polarized and y-polarized incident waves in 8∼18 GHz. The 3 dB gain relative bandwidth of stealth antenna is 40% (8∼12 GHz). The realized gain of the antenna at the center frequency reaches 26.3 dB. It is noteworthy that the stealth antenna balances both radiation performance and scattering performance, which makes it have the merits of high gain and excellent stealth performance simultaneously.

This article presents a dual circular polarization (CP) microstrip antenna, emitting electromagnetic waves above and below the substrate, which is fed by the double L-probe. Selecting the L-probe feed increases the bandwidth of the antenna, and different probes control the rotation of CP. The antenna could radiate two polarized waves of the same amplitude and vertical through two square radiation patches; meanwhile, adjusting the phase difference between both waves to 90° will produce a CP wave in the far-field. The simulation and measurement results show that the antenna is in 4.3–4.8 GHz band with S11<−10 dB, S22<−10 dB, and AR<3 dB. Furthermore, a lower axis ratio could be obtained in this work compared with similar antennas of the same type.

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Integration and stealth performance of the antenna system can meet the requirements of modern warfare for communication systems, and significantly improve the survivability of equipment. However, there are still huge difficulties in function-integrated stealth antennas design. In this article, an ultrabroadband function-integrated stealth antenna system is designed based on asymmetric transmission metasurface (ATMS). By the 45 inclined horn antenna exciting the ATMS, the antenna system achieves stable ultrabroadband high-gain directional radiation and frequency scanning function in transmission and the reflection mode respectively. And the ATMS can scatter the y-polarized reflected wave to achieve in-band stealth of the antenna system when y-polarized wave illuminates the ATMS from backside. The experimental results show that the RCS of the antenna system can be reduced more than 10 dB between 11.6 and 20 GHz (relative bandwidth is 53.2%). In addition, the 3 dB gain relative bandwidth of the directional antenna is 57.1% (10-18 GHz). And the 3 dB gain relative bandwidth of the frequency scanning antenna is 62.3% . This strategy has broad application prospects in communication systems and large-scale integrated devices.

In this paper, an ultra-broadband full-space function-integrated stealth antenna is proposed based on metasurface (MS). After x-polarized and y-polarized spherical wave passing through the MS, the MS converts the y-polarized spherical wave into the x-polarized vortex wave in transmission space, deflects and focus the x-polarized spherical wave into x-polarized plane wave in reflection space simultaneously. Moreover, when y-polarized wave illuminates the MS in transmission space, the MS achieves scattering control on the y-polarized reflected wave to realize the diffuse scattering function. Exciting the MS with a horn antenna, the broadband antenna system with full-space function-integration and low backward RCS is realized. The antenna system achieves high-gain vortex wave radiation in transmission space, and high-gain beam frequency scanning in reflection space. Besides, when y-polarized wave illuminates the antenna array in transmission space, diffuse scattering stealth is achieved. Experimental results show that the 3 dB gain relative bandwidth of the vortex wave antenna in the transmission space is 67% (10∼20 GHz), the 3 dB gain relative bandwidth of the frequency scanning antenna in the reflection space is 54% (11.5∼20GHz), and the scanning angle covers 31°. The antenna backward RCS reduces more than 10dB between 11.7 GHz to 20 GHz.