Microwave Systems

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    04-Jul-2015

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  • 1. Microwave Systems Microwave Engineering CHO, Yong Heui

2. Microwave Engineering1. Microwave SystemsTransmission Information - Channel bandwidth - Base band - Inefficient wave radiation Modulation center frequency : RFDH.com Time domain Frequency domain2 3. Microwave Engineering1. Microwave SystemsWhys modulation need? Transmission efficiency - Multiplexing - Antenna length: wavelength - Wave radiation: comparison with DC Battery: DCAntenna: AC3 4. Microwave Engineering1. Microwave SystemsFriis power transmission formula Microwave radio linkR Pt Pr4 5. Microwave Engineering1. Microwave SystemsFriis power transmission formulaPt Power density: S2 Gt W / m 2 4 R Antenna gain: anisotropic radiation (G > 1) isotropic radiation (G = 1) Radiation pattern [dBi]: dB isotropic 5 6. Microwave Engineering1. Microwave SystemsFriis power transmission formula Received power: Pr SAe Effective area 2 Gr - Ae42 Pr Gt GrW Pt4 R Friis transmission formula6 7. Microwave Engineering1. Microwave SystemsMicrowave transmitter (Tx) Up-conversion: frequencyf BB f LO f BB f LOf BB : RFDH.com1cos(x) cos(y)2cos(xy ) cos(x y) 7 8. Microwave Engineering1. Microwave SystemsMicrowave receiver (Rx) Down-conversion: frequency: RFDH.com f f LO f IF f f IFf LO f BB f IF f BBf BB 1cos(x) cos(y) 2 cos(x y ) cos(x y) 8 9. Microwave Engineering1. Microwave SystemsMicrowave transceiver Duplexer: bandpass filter or switch - Loss, tx suppression, channel selection : RFDH.comIF: superheterodyneNo IF: direct conversion 9 10. Microwave Engineering1. Microwave SystemsUplink and downlink Pt 10[ W ] R40,000[km] fd12[GHz ] 3dB 20.55Pt 100[ W ]fu 14[GHz ]4m diameter dish 0.610 11. Microwave Engineering1. Microwave SystemsUplink calculation 4DrPr EIRPLFS Gr [dB] 1 2GrDr EIRP Pt Gt 4 2 DtAe4 R2 LFS Gt Dt 11 12. Microwave Engineering1. Microwave SystemsDownlink calculationEIRP Pt GtPr EIRPLFS Gr [dB]4Dt1 2GtDtDr4Am ax22 4 RLFS Gr Dr12 13. Microwave Engineering1. Microwave SystemsThermal Noise or Johnson Noise Thermal noise: white noise, Nyquist formulaPn kTBNTNN0 B kB Noise power Noise temperature13 14. Microwave Engineering1. Microwave SystemsCarrier to noise ratio C/No: related to carrier to noise ratio G/T: Figure of merit Carrier to noise ratio C CC NN0 B TkB G/T: sensitivity of receiver C EIRPLFSGr [dB]14 15. Microwave Engineering1. Microwave SystemsMultiplexing: resources FDM (Frequency Division Multiplexing) TDM (Time Division Multiplexing) CDM (Code Division Multiplexing)Communication 15 16. Microwave Engineering1. Microwave SystemsFDMA (FDM Access) Resource: frequency Guard band Simple transceiver Interference 16 17. Microwave Engineering1. Microwave SystemsTDMA (TDM Access) Resource:time Guard time Complicatedtransceiver GSM: Global System for Mobile commo17 18. Microwave Engineering1. Microwave SystemsFH(Frequency Hopping)-CDMA Resource: code Precise clock Very complicated transceiver Bluetooth, military applications18 19. Microwave Engineering1. Microwave SystemsDS(Direct Sequence)-CDMA QPSK: Quadrature Phase Shift Keying19 20. Microwave Engineering2. ApplicationsFrequency spectrum NameFrequency[Hz]Wavelength Application EHF 30G-300G 1cm-1mmCar radar SHF 3G-30G 10cm-1cmRadar, satellite UHF 300M-3G1m-10cmTV, PCS, IMT2000 VHF30M-300M10m-1mFM, TVHF 3M-30M 100m-10mShortwave AM, HAMMF 300k-3M1km-100mAMLF 30k-300k 10km-1kmNavigation VLF3k-30k100km-10km Submarine, navigation ELF30-30010000km-1000kmSubmarine 20 21. Microwave Engineering2. ApplicationsAttenuation HF application Attenuation by water and oxygen 21 22. Microwave Engineering2. ApplicationsELF application Skin depth: long wavelength Long antenna: 104km at USA Unidirectional communication Slow bit rate: redundancy Information: code table2 1 22 23. Microwave Engineering2. ApplicationsEHF application Short antenna Absorption: air, water(60 GHz) Anti-collision radar: 76 GHz ITS: Intelligent Transport SystemRadarITS23