An Energy Selective Cancellation Line Integrated on Microstrip Patch Array for Protection Against High-Power Microwave Threats

This article proposes an energy selective cancellation line (ESCL) integrated on patch antenna array, in which signals above a threshold power level are adaptively canceled between array elements to protect sensitive front-end circuits from high-power microwave threats. For incident signals exceeding the power threshold, ESCLs adaptively excite the antenna mode on adjacent array elements with phases opposite to those induced by electromagnetic irradiation. Compared with existing approaches, the proposed energy-selective cancellation array (ESCA) achieves high protection levels (PLs) which scale with the array size without an additional circuit layer. Therefore, the ESCA is fully compatible with digital beamforming techniques, which is essential for active phased arrays. Operating mechanism of ESCL is explained using the cavity mode theory, and a comprehensive design methodology is proposed for microstrip patch arrays. To validate this concept, a prototype using rectangular patch elements was fabricated and measured. The prototype operates in the frequency range of 2.55–2.65 GHz and provides a maximum PL of ∼49 dB for normally incident signals. The insertion loss introduced by ESCL remains ∼0.3 dB. Owing to its simple structure and extraordinary PL, this method offers a promising solution for passive and active phased antenna arrays.