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munication between LET and SDR-VSAT1 is from 4.1 dB to 13.3 dB according to the communication mode. Here the Eb/No necessary to be error-free (<10-10) was targeted as Eb/No=10 dB. (e necessary Eb/No was measured as 13 dB for the 1,244 Mbit/s mode that is mentioned later.)2.3622 /1,244 Mbit/s dual rate burst modeme high-speed burst modem was developed for the purpose of establishing high speed terminals. A prototype burst modem that operates at a user data rate of 622 Mbit/s was developed [4]–[7], and it was improved to work at a user rate of 1,244 Mbit/s.e conguration of the 622/1,244 Mbit/s dual rate burst modem is shown in Fig. 6. Its view (two sets of photos) is shown in Fig. 7, and the specications are sum-marized in Table 4. e burst modem consists of four boards: a modulation board, a demodulation board, a turbo product code (TPC) decoding board and a control FiF6　Configuration of 622/1244 Mbit/s high speed burst modemWAN/LANControlBurst ModemLPFIQIQIQLPFIQLPFLPFLANInterfaceTx/RxBufferNetworkAccessControland SyncTX SlotBufferQPSKModQPSKDemodUp/DownConverterTPCCoderTPCDecode3 GHzIF in/outRouterI & QModulatorI & QDemodTCPAcceleratorGbEGbEDigital TerminalMonitor &Control155 Mbit/s Ref. BurstDemod Frame Pulse(LET only)ＪＲＢTabT3　Example of link budgetLET⇒LETLET⇒SDR-VSAT1SDR-VSAT1⇒LETSDR-VSAT1⇒SDR-VSAT1RemarksUp-LinkFrequencyGHz28.0528.0528.0528.05Data RateMbps6221244622124462212446221244EIRPdBW79.379.373.173.1Earth Station 3dB Back-offPointing LossdB0.50.50.50.5Free Space LossdB212.8212.8212.8212.8Atomospheric LossdB0.50.50.50.5G/TdB/K18.0 18.0 18.0 18.0 SatelliteUp-Link C/N0dB/Hz112.1 112.1105.9105.9Down-LinkFrequencyGHz18.2518.2518.2518.25EIRPdBW6868.0 68.0 68.0 Satellite 4dB Back-offFree Space LossdB201.9201.9 201.9 201.9 Atomospheric LossdB0.50.5 0.5 0.5 G/TdB/K32.726.3 32.7 26.3 Earth StationDown-Link C/N0dB/Hz126.4120.0 126.4 120.0 TotalTotal C/N0dB111.9 111.4 105.9 105.7 Transmission RateMbps8241648824164882416488241648QPSK FEC Cording Rate =0.879Required C/N0dB/Hz98.6101.698.6101.698.6101.698.6101.6Eb/N0=10dBMarginC/N0 MargindB13.3 10.3 12.8 9.8 7.3 4.3 7.1 4.1 3 Ultra-High-Speed Satellite Communication Technology104　　　Journal of the National Institute of Information and Communications Technology Vol. 64 No. 2 (2017)