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This study presents a planar single‐layer metasurface, with tri‐band 10 dB radar cross‐section (RCS) reduction under normal incidence for both polarisations, by employing optimised multi‐element phase cancellation. The designed artificial magnetic conductor (AMC) unit cell is composed of an upper metal structure, a dielectric layer, and a bottom metal ground. When the dielectric constant and thickness of the substrate are fixed, regardless of any upper structure, the reflection coefficients of AMC are the same as the perfect electric conductor (PEC) at the short‐circuit frequencies. Taking into account the multiple reduction bands that avoid short‐circuit frequencies, a RCS reduction surface with a large frequency ratio is achieved. The optimised planar metasurface obtains 10 dB RCS reduction in the tri‐band frequency (3.81–7.33, 19.16–22.83, and 35.63–38.37 GHz) with bandwidths of 63, 17, and 7.4%, respectively. Moreover, the bistatic scattering patterns between the proposed surface and the equal‐sized PEC are investigated. The theoretically predicted, simulated, and measured results are in good agreement and provide a new strategy for achieving multi‐band RCS reduction. [ABSTRACT FROM AUTHOR]

An ultra‐wideband (UWB) array is presented for UHF‐S band (0.19–2.3 GHz) communications with an emphasis on dual‐linear polarisation and wide‐angle scanning. The array achieves 12:1 impedance bandwidth for a voltage standing wave ratio (VSWR) <3 at broadside with low‐angle scanning off broadside to 0°, 45°, 60° in the E‐plane (VSWR < 3, 4, 3.1) and 0°, 45°, 60° (VSWR < 3, 3.8, 5.5) in the H‐plane. A 7 × 11 prototype was fabricated and tested for verification. In addition, finite effects with respect to mounting UWB arrays in airborne platforms are discussed. Specifically, the effect of radomes, perfect electric conductor shielding walls and resistive walls on the gain of the designed tightly coupled dipole antenna was studied, showing that losses can approach 2 dB. [ABSTRACT FROM AUTHOR]