Design And Application Of Electromagnetic Soft Surface

electromagnetic soft surface is a kind of metamaterials, has been attracted in the field of microwave, and has a good research significance and application value. Artificial electromagnetic soft surface has the property of zero reflection phase for a polarized wave, 180 degrees reflection phase for another polarized wave, and has the property of blocking the energy transmission of electromagnetic waves on its surface at a certain direction. These two properties, respectively, can be called the properties of reflection phase band-gap and surface wave band-gap. Its original structure is the corrugated metal, which heights a quarter wavelength. On the one hand, when the electric fields of the incident electromagnetic wave are parallel to the direction of the corrugated, it is equivalent to the metal surface and the reflection phase is 180 degrees, and when the electric fields are perpendicular to the direction of the corrugated, it equivalent to the magnetic boundary and the reflection phase is zero; On the other hand in transverse direction of the corrugated, it can block the transmission of the electromagnetic wave energy on its surface. It can be used to control the reflection of electromagnetic waves, such as polarization transformation, on the other hand it can be used to control the surface waves, such as controlling edge scattering and suppressing the mutual coupling between antenna. This paper focuses on the property of the surface wave band-gap, the main content includes the four points:(1) It analyzed the mechanism of surface wave band-gap, the metal belt with the surrounding earth capacitance with the theory of the equivalent circuit and equivalent lumped components. The metal vias form the equivalent inductance, the metal bands and around the metal vias form the another equivalent inductance, and the band-gap occurs near the resonant frequency, which are decided by the equivalent lumped components. The structure of a period will occur a resonance point, multiple periods for multiple resonance points. The capacitors are formed between adjacent metal strips, when the charges at edge of the two adjacent metal strips are opposite sign, it can consider as the additional circuit, and is helpful to reduce the resonant frequency, but when the electric charges are the same sign, the electric field between them will repel each other, and can not produce additional circuit, the resonance frequency will increase.(2) By the method of making slots on the metal strips around the metal vias to influence the current distribution on the surface of the metal strips, we design the miniaturization structures of electromagnetic soft surface, and it has been applied in the decoupling between the antenna, the reduction of decoupling reaches about 10 dB near the center of the operating frequency band.(3) The alternate arrangement of two kinds of electromagnetic soft surface, which have different bandwidth of the metal strips or the different gap of metals vias, and or the different position of metal vias, can form a double band-gap structures. And two different kind of the soft surfaces with slots, which have different size of slots, arranged alternately and also can form double band-gap structure. and it has been applied in the decoupling between the double-frequency antenna, the reduction of decoupling reaches about 7 dB near the center of each operating frequency band.(4) To expand the bandwidth of the electromagnetic soft surface, on the one hand, the method of the cascade of different soft surface, which have metal strip widths, is studied, the other hand, the structure had metal sheets which look like ‘工’ in the metal strips, and it makes the band gap occur two resonant points and make the bandwidth wider.