基地台自由空間輻射路逕損失

•自由空間條件
–發射體周圍、接收體周圍、及發射體至接收體有效路逕以空氣為介質，且均無遮蔽物、反射物、折射物、繞射物、散射物
•輻射遠場與輻射近場條件(反之為感應近場條件)
–R>l/2p=(3e8/900e6)/(2x3.14159)=0.0531m (@900MHz)
–R>l/2p=(3e8/1800e6)/(2x3.14159)=0.0265m (@1,800MHz)
•自由空間輻射路逕損失
–L=(4pR/l)^2=[4x3.14159x0.0531/(3e8/900e6)]^2=4.01=6.03dB (@900MHz and R=0.0531m)
–L=(4pR/l)^2=[4x3.14159x0.1062/(3e8/900e6)]^2=16.03=12.05dB (@900MHz and R=0.0531x2=0.1062m)
–L=(4pR/l)^2=[4x3.14159x0.531/(3e8/900e6)]^2=400.7=26.03dB (@900MHz and R=0.0531x10=0.531m)
–L=(4pR/l)^2=[4x3.14159x0.0265/(3e8/1800e6)]^2=3.992=6.01dB (@1800MHz and R=0.0265m)
–L=(4pR/l)^2=[4x3.14159x0.0531/(3e8/1800e6)]^2=16.03=12.05dB (@1800MHz and R=0.0265x2=0.0531m)
–L=(4pR/l)^2=[4x3.14159x0.265/(3e8/1800e6)]^2=399.2=26.01dB (@1800MHz and R=0.0265x10=0.265m)
•結論
–輻射與感應臨界點路逕損失為4times or 6dB
–路逕增減兩倍損失增減4times or 6dB
–路逕增減十倍損失增減100times or 20dB