Waveform-Selective Metasurface Absorber With a Single-Patch Structure and Lumped Nonlinear Circuit for a Higher-Order Mode

Microwave absorbers (MAs) play an important role in protecting sensitive electronic devices from electromagnetic (EM) interference by absorbing the energy of incoming waves and reducing unnecessary reflection or transmission. Here, we numerically and experimentally demonstrated two types of waveform-selective microwave metasurface absorbers (MMAs) with a single square-patch structure and a lumped nonlinear circuit. Our MMAs were designed to preferentially absorb signals at the same frequencies, including a higher-order mode. The proposed capacitor-type MMA was comprised of a single square-patch structure connected with a diode bridge containing a capacitor paired with a resistor in parallel, which could effectively absorb short pulses at two distinct frequencies. Similarly, the proposed inductor-type MMA was comprised of the same square-patch structure, except for the internal circuit replaced with an inductor paired with a resistor in series, which could effectively absorb continuous waves (CWs) at the same two frequencies. The effects of the parameters of lumped circuit components (resistor, capacitor, and inductor) and geometrical parameters on the waveform-selective absorptance of these two types of MMAs for normal incident short pulses and CWs were systemically studied. Both the simulation and experimental results showed selective absorption for specific waveforms at the same two frequencies, including a high-order mode. Thus, the waveform-selective MMAs can provide a wide application range, such as EM shielding, detection, sensing, and wireless communications.