For its importance nowadays in a wide range of applications such as the anechoic chamber, we introduce a microwave ultra-broadband polarization-independent metamaterial absorber (MA) in the Ultra High Frequency (UHF)/ Super High Frequency (SHF) frequency bands. Through this work, we improved the Relative Absorptive Bandwidth (RAB) of the conventional pyramidal absorber (CPA) by modifying its altitude to a curved shape. As a result, the RAB increased from 25.9 % to 71.82 % with an absorptive level greater than 90% paving the way to an optimized structure for a broader band of absorption. As a second target, we looked for widening the broadband absorption of the CPA in the low-frequency region. To achieve this aim, we introduced two new prototypes. The first with a total thickness of 12.7 cm, consisting of 35 curved resonant layers where numerical simulations show an enhanced design with an absorption band from 0.3 GHz to 30 GHz referring ta a RAB of 182%. The second prototype consists of a cell containing different pyramidal absorbers grouped in-plane in a unit cell; such structures operate in complementary bands. This prototype is dedicated to combining these bands of absorption. After that, an enhancement is presented of this latest to reach a well-combined band with a RAB of 128.69%. We used for simulation, testing, and collecting results the High-Frequency Structure Simulator (HFSS) tool.
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