Absorption-Dominant mmWave EMI Shielding Films with Ultralow Reflection using Ferromagnetic Resonance Frequency Tunable M-Type Ferrites

Abstract

Although there is a high demand for absorption-dominant electromagnetic interference (EMI) shielding materials for 5G millimeter-wave (mmWave) frequencies, most current shielding materials are based on reflection-dominant conductive materials. While there are few absorption-dominant shielding materials proposed with magnetic materials, their working frequencies are usually limited to under 30 GHz. In this study, a novel multi-band absorption-dominant EMI shielding film with M-type strontium ferrites and a conductive grid is proposed. This film shows ultralow EMI reflection of less than 5% in multiple mmWave frequency bands with sub-millimeter thicknesses, while shielding more than 99.9% of EMI. The ultralow reflection frequency bands are controllable by tuning the ferromagnetic resonance frequency of M-type strontium ferrites and composite layer geometries. Two examples of shielding films with ultralow reflection frequencies, one for 39 and 52 GHz 5G telecommunication bands and the other for 60 and 77 GHz autonomous radar bands, are presented. The remarkably low reflectance and thinness of the proposed films provide an important advancement toward the commercialization of EMI shielding materials for 5G mmWave applications.

MXene@c-MWCNT Adhesive Silica Nanofiber Membranes Enhancing Electromagnetic Interference Shielding and Thermal Insulation Performance in Extreme Environments

“…According to the shielding efficiency formula η (%) = 100-100(1/10 SE/10 ) [62], MXene@c-MWCNT 6:4 can shield 99.98% of incident electromagnetic wave. In addition, the SE R values of all films are stable in the range of 15 dB, indicating that more than 90% of the incident electromagnetic wave is shielded by reflection [64].…”

Heterostructure Made of Multilayer MXene (Ti3C2Tx) and Vertically Grown CoFe2O4 Nanosheets for Microwave Absorption at 2–40 GHz

“…Electromagnetic waves (EMWs) originate from the extensive utilization of electronic facilities, ranging from smartphones to household appliances, and threaten the environment and human health. , Particularly, with the increasing expansion of 5G communication technology that typically works in frequency bands (over 26 GHz) that are at least 10 times higher than those needed for 4G long-term evolution communication, more electronic devices now work in high- and multiple-frequency bands . Therefore, there is a growing demand for microwave absorbers with the characteristic of broadband absorption. , Microwave-absorbing materials (MAMs) are a class of emerging materials that has recently garnered considerable attention because it can alleviate the negative effects associated with increased EM pollution issues owing to its ability to sustainably convert EM energy .…”

Liquid Metal Grid Patterned Thin Film Devices Toward Absorption-Dominant and Strain-Tunable Electromagnetic Interference Shielding

“…In lieu of the use of metals, polymer-based EMI shielding materials, with various conductive fillers such as graphene, carbon fibers, carbon nanotubes, and MXenes arranged into segregated structures or preferred orientations within the polymeric matrices, are widely used owing to their distinctive attributes like exceptional corrosion resistance, adequate deformability for application in conformal and wearable electronics, and tunable EMI shielding performances such as modulating the shielding effectiveness, and resonant frequency. [ 11 , 18 – 24 ]. Additionally, the filler properties like surface morphology, aggregation, alignments, etc., can be specifically tuned to target electromagnetic waves in different bands or frequency ranges [ 25 – 28 ].…”

“…As a solution to the second case, foam structures have been widely used as effective absorption-dominant materials, but their high void content increases their thickness [ 49 , 50 ]. A few recent studies suggest an alternative approach of usage of conductive grid patterns to achieve low reflection and high absorption at specific frequencies where the minimum reflection is achieved at the resonant frequency on matching the wavelength of the electromagnetic wave (EMW) with the grid period [ 24 , 29 ]. This method is quite promising in terms of significantly reducing the size of the device, however, certain challenges persist, viz., poor choice of materials that can challenge the structural stability for prolonged use and time-intensive, optimization-critical printing technologies.…”