Polarization‐independent reconfigurable frequency selective rasorber/absorber with low‐insertion loss

Abstract

A polarization-independent reconfigurable frequency selective rasorber (FSR)/absorber with low-insertion loss (IL) based on diodes is proposed in this article. The presented structure consists of a lossy layer based on square loops and a bandpass frequency-selective surface. These two layers are separated by an air layer. Each layer has an embedded bias network that provides the bias voltage to the diodes through metallic via. This configuration can avoid undesirable effects associated with the additional biasing wire. When the diodes are in off-state, the structure is in FSR mode and exhibits a transmission window at 4.28 GHz with only 0.69 dB IL within the absorption bands. While diodes are in on-state and the structure switches to absorber mode, it achieves perfect absorption with absorptivity of over 90% ranging from 2.8 to 5.2 GHz. An equivalent circuit model is developed to analyze the physical mechanism of the structure. A prototype of the proposed architecture is fabricated and measured, where reasonable agreements between simulations and measurements are observed, verifying the effectiveness of this design.

Metamaterial Absorbers: From Tunable Surface to Structural Transformation

“…Further, with careful design of periodic patterns, the impedance of MAs will be matched to free space at resonant frequencies, resulting in a minimized reflection. [46][47][48] Then, the dielectric dissolves the incident wave through either Ohmic losses in periodic patterns or dielectric losses in spacer. [4] To understand the mechanism of absorption, equivalent circuit theory has been widely used.…”

“…In the past two decades, lumped elements, such as PIN diodes, varactor diodes, resistors, and capacitors, have been extensively studied as tuning strategy in tunable/reconfigurable MAs due to the mature technology, easy operation, wide tuning range, and fast shifting speed. [4,63,64,67,[105][106][107] PIN diodes have been widely used for a variety of circuits and are very useful for RF switching in microwave frequency band. As a switch, it works as a resistor with a very high resistance (nearly insulating) under zero bias voltage (i.e., OFF state), while it has a very low resistance (about 1 Ω, similar to metal) at a higher forward bias voltage (i.e., ON state), as illustrated in Figure 3a,b.…”

Miniaturised frequency selective surface‐based rasorber with wideband two‐sided absorption and switchable transmission/reflection band

“…For further flexibility, reconfigurable FSR-ATA has been investigated. By regulating the bias voltage of the active elements embedded in the configuration, the working states of the elements are altered, which consequently changes the frequency response [20,[23][24][25][26]. They can be classified into two categories: FSR with a switchable transmission band that can be switched between two states, and FSR with a tunable transmission band that has an adjustable transmission frequency.…”

Polarization‐insensitive frequency selective rasorber with broad absorption band and two‐sided transmission bands

“…11,12 In order to overcome the communication limitation of FSS based absorbers, frequency selective rasorbers (FSRs) with dual characteristics of absorption and transmission have gained much popularity in the recent years. [13][14][15][16][17][18][19] The FSR are generally obtained by integrating the bandpass application of FSS with the absorbers, where the ground layer of the absorber is replaced with a bandpass FSS such that both the transmission and absorbance characteristics are retained. Moreover, the FSR structures are also used to achieve low out-of-band radar cross section.…”