Fig. 1 System Block Diagram
SSC13-II-2
300 Mbps Downlink Communications from 50kg Class Small Satellites
Hirobumi Saito Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS)
Naohiko Iwakiri , Atsushi Tomiki, Takahide Mizuno, Hiromi Watanabe, Tomoya Fukami, Osamu Shigeta, Hitoshi Nunomura, Yasuaki Kanda , Kaname Kojima, Takahiro Shinke, and Toshiki Kumazawa Contents
1. Purpose : 320Mbps down link for small sat 2. Onboard segment: high effiency transmitter. small antenna 3. Ground segment : 3.8m S/X band antenna powerful receiver 4. Total simulation : SPW software + link calculation 5. EM test finished. FM maunfacturing now. 6. On-orbit demonstration : 2014 with 50kg sat.
Limits of Small Satellites for Earth Observations • Mass Limit（<100kg）, Power Limit (<100W) ー Telescope Resolution （5m vs. 0.5m)
ー Down link Speed (10Mbps vs. 800Mbps)
・ What is the Bottleneck of Down Link Speed ? － Power !
Down link bit rate VS. satellite mass
for low earth orbit.
1.0E+12
） 1T
bps TerraSAR-X Hodoyoshi #4 （ (2014) WorldView1 1.0E+09 EROS-B Formosat2 GeoEye-1 1G Orbview3Kompsat2 ALOS Orbview4 JERS1 EOS-PM1 Ikonos2 Radarsat1 TopSat QuickBird2 ERSEnvisat1 Lewis Landsat ADEOS Spot RazakSat-1 UK-DMC2 MOS 1B MOS 1A Terra IRS-1A,1B,1C UK-DMC1 EROS-A AS1000 AlSat Orbview2 TRMM 1.0E+06 データ伝送速度 1M EarlyBird MicroLabSat
Cute-1.7 PRISM TOMS-EP
Cute-I Down Link Bit Rate(bps) Link Bit Down
観測衛星の 1.0E+031K
1 10 100 1000 10000
Satellite衛星質量 Mass（kg） (kg) High Speed Down Link for Small Sat • Purpose of This Research： High-speed Down Link System with Low Power Consumption ―Goal 50kg Sat @600km orbit DC power <20W, 320Mbps Small Ground Antenna < 4m
System block diagram of high-data-rate downlink. Satellite Transmitter FPGA Cal A Cal B Cal C
I CCSDS- Pulse Low I/Q Pre- I-Q UP- RF Formated Shaping D/A Pass Map Distortion Mod Con Amp Data Q Filter Filter
Simple digital circuit Simple memoryless GaN Amplifier Small X band X2.5 oversampling look – up - table high efficiency & small distortion antenna with analog filter
Ground Data Demodulator
Turbo equalizer, Small S/X dual band Turbo decoder parabolic antenna Performance of High - Data - Rate Down Link
Instruments Mass Power Remarks (g) (W)
On-board Transmitter 1330 18 16QAM, 348Mbps GaN Power Amp. Antenna MGA 69 0 13.5 dBi Iso-flux 150 0 5dBi(60°），-2dBi(0°） Ground Station Antenna 3.8m Dia. S/X Cassegrain, 47.5dBi(X), 36dBi(S), Sys. Noise temp. 100K Demodulator 100Msps, (348-144Mbps), 16QAM, QPSK SCCC Turbo Equalizer CCSDS 131.2-B-1 High-Speed 16QAM Down Link
with Nonlinear Amplifier
Input IQ Constellation Output I-Q Constellation Q Nonlinear Amplifier
18
2 10 位相回転 I
AM & PM 1 sumbol transmits 4 bits Distortion Inter Symbol Interference
High efficiency RF amplifier may degrade bit error rate Digital Pre-distortion compensates Nonlinearity
Pre-Distortion Nonlinear RF amplifier
Pulse Mod RF out Shape AM - PM Filter AM compensation Small Distortion
PM compensation AM - PM X Band Power Amplifiers
Amplifier GaAs AB GaN AB GaN F Maximum Power 38dBm 37dBm 36dBm Maximum Gain 10dB 11dB 12dB Maximum PAE 37% 46% 60% PAE at 3dB OBO 23% 36% 38% Maximum Phase Shift 10° -2° -34°
Newly Developed 2W GaN HEMT AB Class
3cm AM/AM AM/PM IQ Constellation Without
Pre-distortion
]
GaAs dBm
(AB)
Output[ Phase Shift Shift [degree] Phase
Input [dBm] Input [dBm]
]
GaN dBm
(AB)
Output[ Phase Shift Shift [degree] Phase
Input [dBm] Input [dBm]
]
GaN dBm
(F)
Output[ Phase Shift Shift [degree] Phase
Input [dBm] Input [dBm] AM/AM AM/PM IQ Constellation Without With
Pre-distortion Pre-distortion
]
GaAs dBm
(A)
Output[ Phase Shift Shift [degree] Phase
Input [dBm] Input [dBm] Pre-distortion
]
GaN dBm
(AB) ⇒
Output[ Phase Shift Shift [degree] Phase
Input [dBm] Input [dBm]
]
GaN dBm
(F)
Output[ Phase Shift Shift [degree] Phase
Input [dBm] Input [dBm] EM of 348 Mbps Transmitter
Modulation:16QAM/QPSK Mass : 1330g RF Power: 2W DC Power :20W
AM-AM, AM-PM Characteristics X-band Transmitter (EM) Efficiency(PAE) 47% (PA, GaN-HEMT) Output Backoff 2dB Phase Shift 2 deg (average)
EM Input-Output characteristics EM Input-Phase shift characteristics 36 7 8085MHz 8085MHz 34 8110MHz 6 8110MHz 8135MHz 8135MHz 5 32 8160MHz 8160MHz 8185MHz Average 4 8185MHz 30 8210MHz power 8210MHz 8235MHz 3 8235MHz 28 2 26
1 Phase shift [deg] Output Level [dBm] 24 0 Average 22 -1 power 20 -2 0 5 10 15 20 0 5 10 15 20 Baseband Input Level [dB] Baseband Input Level [dB] 16QAM I/Q Constellation @ 33dBm (EM RF block)
Without Predistortion With Predistortion
Inner Points Improved By predistortion Bit Error Rate v.s. Eb/No EM RF Block, uncoded 16QAM
-2 When Uncoded BER < 5x10 at Eb/No =10dB, SCCC + Turbo Equalizer / Deoder achieves BER < 10-6.
Requirement For Uncoded BER Onboard Small Antenna Body-Fixed Medium Gain Antenna 14 dBi, 68g Satellite
3.8m Ground 14 dBi, 68g, 7x7cm Station Active Passive element element
For 320Mbps high bit rate Feed mode, point Satellite points earth station
Onboard Small Antenna Body-Fixed Iso-flux Antenna 5dBi max, 150g
qaudrafilar helix 150g, D=10mm, H=20m
For Earth-Pointing Satellite, D Antenna pattern compensates range variation α feed H points Ground Antenna 3.8m Ground Antenna for S / X Band S band : Telemetry & Command X band : Mission Data Down Link (320Mbps) Ring-Focus Cassegrain Block diagram of high-data-rate downlink and ground receiver
Transmitter Receiver Frequency tracking loop (FTL)
Complex Loop Phase Freq. Phase NCO filter detector shift noise AWGN
Packet SRRC Pre- Power RF Signal Matched r SCCC ↓2 n ˆ ai generator filter distortion amplifier BPF resampler filter turbo equalizer ai
Signal Loop Timing searcher filter detector
Timing tracking loop (TTL) Developing 400Mbps 16QAM ground receiver Block diagram of high-data-rate downlink and ground receiver
Transmitter Receiver Frequency tracking loop (FTL)
Complex Loop Phase Freq. Phase NCO filter detector shift noise AWGN
Packet SRRC Pre- Power RF Signal Matched r SCCC ↓2 n ˆ ai generator filter distortion amplifier BPF resampler filter turbo equalizer ai
Signal Loop Timing searcher filter detector
Timing tracking loop (TTL) Simulation Required Eb/N0 for BER = 10-6 GaN AB Amplifier without with pre-distortion pre-distortion linear channel
16QAM
B)
ｄ
（
o
/N
b E QPSK
Coding Rate CCSDS 131.0 SCCC Link margin of high-data-rate down (2W GaN HEMT of AB class with pre-distortion)
320 Mbps 14 dBi MGA +3.8m Groun Ant EL＝ 30°
1 2 3 4 5 6 13 14 15 16 ACM Project Schedule
Onboard Tranmitter Now ! ’13 June T EM test ‘13 June-Sep. FM manufacturing ‘13 Oct. FM test Ground Antenna ’13 March Installation Ground Receiver ’13 Aug. First test ‘13 Nov. Complete ? Hodoyoshi - #4 (60kg) Launch Goal ! ’14 March by Dnepr ’14 Demonstration 320Mbps 16QAM test on orbit
Conclusions
1. Developing 320Mbps 16QAM down link for 50kg satellite. 2. Power-efficient transmitter (GaN HEMT amp with predistortion) small antenna (MGA, isoflux) 3. Small ground antenna, powerful receiver (turbo equalizer & decoding) 4. On-board demonstration in 2014 with 50kg sat.