An Ultrawideband Multituned Absorber With Frequency-Agile Characteristic for EMI Shielding

Abstract

A novel synthesis procedure for tunable absorbers is proposed, enabling frequency-agile absorption performance within ultrawide frequency band. Multiple tunable capacitive screens are incorporated to flexibly reconfigure absorption band. This article analyzes the variation in absorption rates concerning the capacitive screen's surface admittance across bands. A metallic patch with different sizes is employed as the first-level capacitive screen to validate the reconfiguration of absorption rates across different bands. To extend the frequency-agile band to lower frequencies, a second-level tunable capacitive screen is proposed. Based on the calculated surface admittance region, appropriate varactor devices are selected and their tuning range are determined. The design incorporates dual-channel independent and continuous control, enabling the structure to flexibly adjust the absorption magnitude across the ultrawide frequency band. The prototype demonstrates seamlessly adjustable absorption capabilities across from 1.42 to 19.0 GHz, achieving a fractional bandwidth of 172.2$\%$ with a reflection coefficient below $-$10 dB. It also features dual polarization and a low-profile height of 0.052$\lambda _{L}$. It offers tunable absorption capability to selectively adjust the absorption characteristics in L-/S-/C-/X-/Ku-bands, making it advantageous for dynamic electromagnetic interference shielding applications.