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EMI absorber
EMI absorbing materials are commonly found amongst high-tech products such as LCD electronic devices, laptop and desktop computers. Electromagnetic wave absorbing materials are composed of dielectric materials mixed with ferrite, a magnetic material, with varying shapes and sizes. It should be capable of absorbing electromagnetic energy at normal and large incident angles over a wide range of frequencies. This requires the material to possess a large relative complex dielectric constant (permitivity εr), as well as a large relative complex magnetic permeability constant (μr).
We optimize one-dimensional multi-layered of material design for radio wave absorbing, designed by using a constrained optimization searching technique. Included in the thesis are two complete, practical, optimal designs considering available material parameters (finite loss tangent) as well as their actual manufacturing limitations (layer thickness).
EMI absorber Introduction:
SG absorber / SB absorber is designed to function as a near-field absorber. In simple terms it is intended to be placed close to the source of electromagnetic (EM) radiation. Because it can be made very thin (as slim as 0.15mm), it is especially well suited for use in tight spaces. Suppressing undesirable emissions in a mobile phone is certainly a near field application.In the near field the EM wave has not developed into a plane wave. With a plane wave the value of the electrical component of the energy (E), divided by the magnetic component (H) = 377O, which is the impedance of free space. In the near field the energy is present as spherical waves where E/H is unequal to 377 ohms. In the case of mobile phone frequencies the wavelength of the EM energy is quite large. For example at 1.9GHz the wavelength is just under 16cm. This big wavelength makes it virtually impossible for the energy to radiate through small openings.
In a mobile phone the compartment of the phone case is essentially a cavity. Within the cavity circuits are radiating EM energy which bounce around against the reflective surfaces inside the cavity, as what are called "standing waves". Quite likely currents are also conducting along the reflective (conductive) surfaces. In essence the phone generates a high level of multi-frequency energy which must be brought under control.
By introducing SG absorber and SB absorber into the phone, near an emission source, design engineers have provided a mechanism whereby the resonances, standing waves and creeping surface currents are converted from harmful electromagnetic energy to minute levels of heat. In a sense SG/SB acts as a sponge to soak up the energy and attenuate it.
QuanYi Electronics has engineered SG/SB with complex permittivity and high magnetic permeability values such that it is very effective at controlling unwanted EM energy. SG/SB should not be viewed as a barrier which prevents the energy from escaping, but rather as a structure which, over its entire dimensions, absorbs the energy and attenuates it. The polymer binder of the SG/SB is merely a means to suspend and orient the countless, highly refined and precisely oriented metal particles which do the actual work.