3-D Absorptive Energy-Selective Structures

In this article, an absorptive energy-selective structure (ESS) based on a 3-D structure mounted with p-i-n limiter diodes is proposed for achieving high-power electromagnetic protection and low reflection at the same time. Two separate transmission and absorption paths are constructed by the 3-D structure. They are activated and bypassed, respectively, under a low-power incidence with turned-off diodes generating a high-efficiency transmission window and out-of-band absorption. On the contrary, the diodes are turned on and the structure is then short-circuited under a high-power incidence, leading to high shielding effectiveness and low reflection. To demonstrate the design concept, an absorptive ESS operating at 3 GHz is designed. Cuboid absorbing material with high power-handling capacity is employed to absorb the undesired incident signals. A stepped-impedance resonator structure is constructed as the transmission path to reduce the profile of the 3-D structure. Equivalent circuit models are derived to explain the operating principle and to deduce the design guidelines. Furthermore, the absorptive ESS is fabricated and tested achieving a good agreement between simulated and measured results. High-efficiency transmission with |S
₂₁
| > -0.7 dB under the low-power incidence, high shielding effectiveness with |S
₂₁
| <; -40 dB under the high-power incidence, and low reflection with |S
₁₁
| <; -10 dB are achieved at the operating frequency.