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High/Low Frequency Absorbing Materials · Full Frequency Electromagnetic Interference Suppression
The working frequency range of electromagnetic wave absorbing materials is extremely wide - from 9kHz very low frequency to 110GHz millimeter wave. At different frequencies, the physical mechanisms of interaction between electromagnetic waves and matter are completely different, which means that the word "absorption" corresponds to completely different material design logics.
In the low frequency range (MHz to GHz), the wavelength of electromagnetic waves is relatively long, and the magnetic response of magnetic materials dominates. Absorbing materials mainly rely on magnetic loss mechanisms such as hysteresis loss, eddy current loss, and natural resonance to convert electromagnetic energy into thermal energy. The core challenge of low-frequency absorption is that the wavelength is too long - in order to achieve effective impedance matching and sufficient electromagnetic wave propagation path, materials often require a large thickness.
In the high frequency range (GHz to millimeter waves), the wavelength of electromagnetic waves is short, and the magnetic response of materials rapidly decays. At this point, absorption mainly relies on the dielectric loss mechanism - converting electromagnetic energy into thermal energy through dipole polarization, interface polarization, and conductivity loss. The core challenge of high-frequency absorption lies in how to achieve wideband and high-efficiency absorption within an extremely thin thickness.
Core Insights:Understanding the frequency mechanism correspondence is the first step in correctly selecting absorbing materials.
Low frequency absorbing materials mainly target electromagnetic waves at the low frequency range of MHz to GHz, and their core loss mechanism is magnetic loss.
The absorbers of low-frequency absorbing materials are mainly magnetic metal materials. Typical low-frequency absorbing materials include:
The core performance indicators of low-frequency absorbing materials include the real part of magnetic permeability (μ ') and the tangent of magnetic loss angle (tan δ μ). The higher the magnetic permeability, the greater the ability to convert low-frequency electromagnetic waves. For example, NS1000 absorbing material has a magnetic permeability of 110 at 1MHz and excellent absorption conversion effect in the frequency range of 20MHz-2GHz. The applicable frequencies of low-frequency absorbing materials cover the range of 1MHz-3GHz.
13.56MHz RFID/NFC anti metal tags are a classic application of low-frequency absorbing materials. In power electronic devices such as motor control boards, low-frequency absorbing materials can eliminate electromagnetic interference without changing software and hardware. Low frequency absorbing materials are also widely used in electromagnetic shielding, communication equipment protection, and electromagnetic environment improvement scenarios.
High frequency absorbing materials mainly target electromagnetic waves above GHz, and their core loss mechanism is dielectric loss. In the high frequency range, the magnetic permeability of the material rapidly decays, and it is necessary to rely on the dielectric constants (ε′ and ε″) to match the free space impedance and achieve efficient absorption.
The absorbers of high-frequency absorbing materials are mainly dielectric materials:
In the millimeter wave frequency band (above 30GHz), Laird's Eccosorb ™ MMI and JC-S-Nex cover frequency bands of 35-100GHz and above 35-100GHz, respectively.
High frequency absorbing materials pursue wideband absorption, high absorption rate, lightweight, and thinning. Effective absorption bandwidth (EAB, frequency range with reflection loss<-10dB) is an important indicator for evaluating high-frequency absorbing materials. Laird's Eccosorb ™ BSR-C provides high loss absorption in the 6-18 GHz frequency band. The Platinum Tao New Materials HA series covers an ultra wide frequency range of 100MHz-110GHz.
High frequency absorbing materials play a key role in radar stealth, electromagnetic compatibility (EMC), and communication interference suppression. High frequency absorbing materials are used to suppress cavity resonance and harmonics in RF amplifier cavities and phased array radar T/R modules. In 5G communication and millimeter wave radar, high-frequency absorbing materials are used to suppress surface wave and sidelobe interference.
| Dimension | Low frequency absorbing material | High frequency absorbing materials |
|---|---|---|
| Typical frequency range | 1MHz–3GHz | 800MHz–110GHz |
| Core loss mechanism | Magnetic losses (hysteresis, eddy current, natural resonance) | Dielectric loss (dipole polarization, interface polarization, conductivity loss) |
| Typical absorbent | Ferrite (NiZn/MnZn), flake FeSi/FeSiAl, magnetic metal micro powder | Carbonyl iron powder, carbon nanotubes, graphene, nanomaterials |
| Key performance parameters | Magnetic permeability real part μ ', magnetic loss tangent tan δ μ | Dielectric constant ε′/ε″, effective absorption bandwidth EAB, reflection loss RL |
| Thickness characteristics | Low frequency absorption generally requires a larger thickness | Can be made very thin |
| Typical Applications | RFID/NFC anti metal tags, motor control board EMI suppression | Radar stealth, 5G millimeter wave, cavity resonance suppression |
Advanced Institute (Shenzhen) Technology Co., Ltd. (referred to as "Advanced Institute Technology") was established in 2016. It is a national high-tech enterprise specializing in shielding materials, absorbing materials, flexible substrate coatings, and precious metal pastes. It has the independently registered trademark "Research Platinum".
The high and low frequency absorbing materials produced by the company cover a wide frequency range from 1MHz to 110GHz, and can provide targeted material selection solutions based on the electromagnetic interference characteristics of different frequency bands.
Using carbonyl iron powder, nanomaterials, and carbon based composite materials as core absorbents, it is suitable for scenarios such as radar stealth, 5G communication equipment, millimeter wave radar, and RF amplifier cavity resonance suppression. The average reflection coefficient of composite absorbing materials can reach -25dB in the frequency range of 2-18GHz.
Using ferrite and magnetic metal micro powder as core absorbents, it is suitable for RFID/NFC anti metal tags, motor control board EMI suppression, electromagnetic shielding, and communication equipment protection scenarios. Maintain high magnetic permeability characteristics in the frequency range of 1MHz-3GHz.
Specially designed for microwave cavities, it can effectively attenuate cavity resonance and reduce Q factor within the frequency range of 1-20GHz.
Firstly, it is necessary to clarify the electromagnetic interference frequency bands that need to be addressed. Low frequency interference (MHz to GHz low-frequency end) prioritizes the use of magnetic loss materials; For high-frequency interference (above GHz), dielectric loss materials are preferred.
The low-frequency range is mainly dominated by magnetic losses, with priority given to ferrite and magnetic metal micro powder systems; In the high frequency range, dielectric loss is the main factor, with priority given to carbonyl iron powder, carbon nanotubes, and nanomaterial systems.
Low frequency absorbing materials usually require a large thickness to achieve effective absorption; High frequency absorbing materials can achieve thin design. In space constrained scenarios, a trade-off needs to be made between absorption performance and thickness.
Broadband absorbing materials cover a wide frequency range and are suitable for complex electromagnetic environments; Narrowband absorbing materials have extremely high reflection losses (up to 20dB or more) at specific frequencies, making them suitable for scenarios where a single interference frequency is known.
The essential difference between high and low frequency absorbing materials lies in the different physical mechanisms by which electromagnetic waves interact with matter at different frequencies. The low-frequency band relies on magnetic losses for "thick accumulation and thin development", while the high-frequency band relies on dielectric losses for "thin, light, and wide bandwidth" - both together constitute a full frequency range electromagnetic interference suppression system from MHz to 110GHz.
From RFID anti metal tags to 5G millimeter wave radar, from motor control board EMI suppression to RF amplifier cavity resonance elimination - high and low frequency absorbing materials are pushing the electromagnetic protection concept of "absorption" rather than "reflection" from the laboratory to every corner of the real engineering world. Understanding the correspondence between frequency mechanism material is the core prerequisite for correctly selecting absorbing materials.
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