(4)阵列在通信中的应用 ·卫星通信：跟踪和数据中继卫星TDRSS, DSCS III系统等 移动通信：智能天线 Solar Array Single Access Antenna Omni Antenna Solar Array (S-Band) Multiple Access Antenna Space-to-Ground-Link Antenna Single Access Antenna 2020-01-18 TDRSS 1-7 16
2020-01-18 16 (4) 阵列在通信中的应用 • 卫星通信： 跟踪和数据中继卫星TDRSS， DSCS III系统等 • 移动通信：智能天线 TDRSS 1-7
卫星通信系统示意图 Satellite Array antenna Antenna dish Nul for S4 ( Ku Band LBand FDMA/SCPC FES S2 S3 2020-01-18 17
2020-01-18 17 卫星通信系统示意图
智能天线系统示意图 Past Smart Antenna Space Division Multiple Access (SDMA) Now Past Now Beam Same Time and Tracking Frequency Smart Antenna Technology 2020-01-18 18
2020-01-18 18 智能天线系统示意图
Channel Problem Multipath channel In terrestrial wireless communications,the transmitted signal is reflected or diffracted by large buildings between transmitter and receiver,creating propagation paths having different time delays. Strong channel frequency-selectivity ■ For signal transmissions using 12.5MHz bandwidth,1 symbol length in time is equivalent to the distance of 24 m.So,many distinct multipaths exist which have time delays of longer than the transmitted symbol length. Large obstacles Transmitter Local scatterers Reflection/ 0.6 Receiver diffraction B目 d.5 2020-01-18 19
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Transmit Power Problem Peak power is in proportion to "transmission rate"x "f 2.6 [Hata-formula]"where f is the carrier frequency. Assume that the required transmit power for 8kbps@2GHz is 1Watt for a communication range of 1,000m. The required peak transmission power for 1Gbps@3.5GHz needs to be increased by 1Gbps/8kbps x(3.5GHz/2GHz)2.6=535,561 times,that is, 536kWatt. Obviously,this cannot be allowed. To keep the 1W power,the communication range should be reduced by 43 times(i.e.,1,000m >23m).>Femto cellular network. 8kbps@2GHz 1Gbps@3.5GHz M.Hata,"Empirical formula for propagation loss in land mobile radio services",IEEE 23m 1000m Trans.Veh.Technol.,VT-29, pp.317-325,1980.28 2020-01-18 20
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