Chapter 2 reless communication Technology (第2章[l, or Part Two in[2
Chapter 2 Wireless Communication Technology (第2章[1], or Part Two in [2])
Outline 2.aNtennas, Propagation and Propagation Characteristics(天线、传输、 传输特性) 22 Spread Spectrum(扩频)
Outline ◼ 2.1Antennas, Propagation and Propagation Characteristics (天线、传输、 传输特性) ◼ 2.2 Spread Spectrum(扩频)
2.aNtennas and Propagation Reading material: 1. Antenna Tutorial 2. Chapter 5 in [2]
2.1Antennas and Propagation Reading material: 1.Antenna Tutorial 2.Chapter 5 in [2]
2.1.1 Classifications of Transmission Media(2.4 in (21) Transmission medium(传输媒介) Physical path between transmitter and receiver a Guided media(导波介质) Waves are guided along a solid medium E.g., copper twisted pair, copper coaxial cable, optical fiber Unguided Media Provides means of transmission but does not guide electromagnetic signals a usually referred to as wireless transmission g, atmosphere, outer space
2.1.1 Classifications of Transmission Media (2.4 in [2]) ◼ Transmission Medium(传输媒介) ◼ Physical path between transmitter and receiver ◼ Guided Media(导波介质) ◼ Waves are guided along a solid medium ◼ E.g., copper twisted pair, copper coaxial cable, optical fiber ◼ Unguided Media ◼ Provides means of transmission but does not guide electromagnetic signals ◼ Usually referred to as wireless transmission ◼ E.g., atmosphere, outer space
Unguided media a Transmission and reception are achieved by means of an antenna a Configurations for wireless transmission a directional Omnidirectional
Unguided Media ◼ Transmission and reception are achieved by means of an antenna ◼ Configurations for wireless transmission ◼ Directional ◼ Omnidirectional
交通传输介质:铁路、公路、河 流、天
交通传输介质：铁路、公路、河 流、天空
无线电波波长与频率 波长(λ小:西个桐年的波峰之河的距离 口波长和频率的关系 ○光速(c):电磁波在真空中的传播速度(③3*10m/s) ○频率(:电磁波每秒震动的次数 c△ λf=c △f〓 波段越高,数据传输率越高
无线电波波长与频率
可见光 100102104106108101010121014/10161018102010221024f(Hz) Radio Micro- Wave linfraredUv X-ray Gamma ray 电磁频谱及在通信中的使用 194105106107108109101010111012101310141015~1016 双绞线 卫星 光纤 同轴电缆 AM无线FM无线陆地微波 Band LF MF HF VHF UHF SHF EHF THF
无线频谱的分配 口频率统一分配(FCC/TUR/各个国家) ○根据信息类型分配频谱(AMFM无线电台、TV、蜂窝 电话 口工业科学医学频段(IsM) ○可自由使用但限制功率 O专用于非许可的商业用途 ◇救护车、警察、出租车、无线遥控玩具、无线电家 用设备等)
无线频谱的分配
ISM 令蓝牙和80211 ◆受微波炉和雷达干扰 令工作最好 今设备昂贵 令但太拥挤 ÷802.11a MHz 835Mz 125 MHZ 902MHz-928MHz 2 4GHz-2 4835GHZ 5.735GHz-5.860GHz
ISM