WIFI_Antenna_design_and_application参考.ppt

EF AF TOTAL AF EF Case (c) 往相位落後方向發射及接收 N-Element Array Broadside Array 每根天線具相同相位及電流 Endside Array 往相位落後方向發射及接收 Endside Array ? 集中火力 Endside Array應用於雷達 Broadside Array ? 左右分散攻擊 * * Antenna Wireless 1886 HertZ 提出天線理論 1901 Marconi 把天線應用於生活上 Antenna Theory Radiation Mechanism Create radiation (a.) There must be a time-varying current or acceleration charge (b.) The wire must be curved、bent、discontinuous、terminated or truncated Radiation Mechanism Field regions of an antenna Radiation Pattern Def：The radiation pattern is a graphical representation of radiation properties of the antenna as a function of space coordinates Classification 1.Isotropic Pattern 2.Directional Pattern 3.Omnidirectional Patter Main lobe (major lobe) Side lobe Back lobe Half power beamwidth(FNBW) First null beamwidth(FNBW) Radiation Pattern Current distribution on TL 天線是TL的變形 Current distribution on Dipoles Antenna Parameter 1. Radiation Power(輻射功率) 2. Radiation Intensity(輻射強度) 3. Radiation Resistance(輻射電阻) 4. Directivity(方向性) Dipole Dipole Dipole XZ plane ? E plane XY plane ? H plane Radiation Pattern Dipole radiation pattern Half-wavelength Dipole?D=1.64 Isotropic?D=1 Dipole radiation pattern Vertical electric dipole above ground plane 修正項 Vertical electric dipole above ground plane Vertical electric dipole above ground plane 有適當的h 提高天線效能 將金屬板放置天線後適當距離 範例 Monopole Folded Monopole PIFA 電感性，阻抗匹配用 PIFA PIFA變形 全向性 線性極化 PIFA Two-Element Array AF EF AF EF Two-Element Array EF AF TOTAL Case (a) AF EF EF AF TOTAL AF EF Case (b) 往相位落後方向發射及接收