?3? RF?????

1
?3? RF?????
2
???????

• ????(RF)??????
• ?????????????
• ????????????
• ??????????

3
??????????????
4
????(signal)???

• ?????????????
• ??(Analog)
• ??(Digital)
• ?????
• ??(Bandwidth)???????(Data Rate)
• ??????????(radio spectrum)

5
?????(gain)???(loss)
6
????????
7
?????(radio spectrum)
8
???????

• ??????(ground wave propagation)
• ??????(sky wave propagation)
• ??(line-of-sight)???

9
????????

• ??(diffraction, ??shadow fading)
• ??(scattering)
• ??(reflection)
• ??(refraction)

10
?????????????
11
???????(Propagation Mechanism)

• ?????(Multi-Path)
• ?????????????? ????????,??,?????
• ???????????!!

12
Fresnel zones???
13
Fresnel zones???(Cont.)

• ????????????? ????, ????????????
• ?????????????,??????!

14
??????????

• ??????????(free space propagation model) ?
  ????????????
• ????????(large-scale propagation model) ?
  ?????,?????????????? ?????????
• ????????(small-scale propagation model?fading
  model) ? ????(fading)????????,??? ??????????
  ??????

15
?????(Doppler effect)
16
?????(Doppler effect)

• ?????????????????(Shift)
• ?????(Doppler spreading)
• ???????ltgt????????????? ? ????????

17
???????(dispersive characteristics)
???? ? ??????!
18
??????????

• VSWR (voltage standing wave ratio)???
• ? RF?????????, ???????
• ??VSWR??????,????????,??????!
• ????(intentional radiator)
• EIRP??? Equivalent isotropically radiated
  power????????????

19
AP??????
20
?????

• ??????????(W, watts) ?
• 1 watt????1??(V, volt)?1??(A, ampere)???
• ??????????7 watts ?
• FCC??2.4 GHz?????WLAN????????????4 watts?
• ??????(db)

21
??(signal)??????
22
??(signal)??????
23
??(signal)??????
24
??(signal)??????
25
????(intentional radiator) ?EIRP
EIRP (equivalent isotropically radiated
power)??????????????,FCC????????????????????????
26
Questions

• ?????????????????,??????,?????? ?
• Ans. ?????????
• ????????????????????? ?
• Ans. ????????
• ????????????????????????? ?
• Ans. ??????(head-end)????????????????
• ???????????????????? ?
• Ans.????

27
?????

• (2) ?????????????????? ? 1 ??? 2 ???
  3??(line-of-sight)??? 4 ????
• (4) ????????????????,?????????????????? ? 1
  ????????? 2 ????????? 3 ???????????? 4
  ?????????????