影响Salisbury屏高频响应的若干因数

High frequency response of Salisbury screen and its related factors

应用传输线理论研究了金属薄膜Salisbury屏的反射率频谱特性 ,得到了Salisbury屏的反射系数公式和带宽系数的表达式 .理论和数值分析表明 ,Salisbury屏的反射频谱是谐振型的 ;在谐振频率处 ,反射率的大小仅与金属薄膜的归一化面电阻α有关 ,而在其他频率处则取决于α和隔离层波阻抗 η2 .反射率带宽系数Δ取决于反射率的考察值Γα,η2 和α .当α→αc,η2 →η0 时 ,Δ取得极大值 ,αc 的大小与Γα 有关 ,且通常αc≠ 1.

In this work, the high-frequency response of the Salisbury screen made of metallic thin film was investigated. The formulas of reflectivity and bandwidth coefficient were derived. Theoretical and numerical studies show that the spectrum of reflectivity presents a resonance type, which is symmetric to the resonance frequency. The reflectivity is determined only by the normalized surface resistance α of the metallic film at resonance, and by both α and wave impedance η 2 of the isolation layer at other frequencies. For the bandwidth coefficient Δ, it is determined by the examined reflectivity Γ a, η 2 and α. Bandwidth coefficient can be improved by changing the wave impedance η 2, and tuning the surface resistance to the optimum value α c which is correlated to Γ a and not equal to the one in most cases. It is also noted that the thickness of the metallic thin film should be in the order of sub-micron or nanometers.