LINC Transmitter Architecture for Nano-satellites.

Transcription

1 LINC Transmitter Architecture for Nano-satellites. 7 th Anniversary Delfi C-3, Delfi Foundation Information Day. Presenter/Author: Ir. Visweswaran Karunanithi, RF Systems engineer [ISISpace B.V] Supervisors: 1) Ir. Dr. C.J.M. Chris Verhoeven [TU Delft] 2) Ir. Waldemar Lubbers [ISISpace B.V]

2 The work in this thesis was supported by Innovative Solutions In Space B.V Their cooperation is hereby gratefully acknowledged Copyright All rights reserved. 2

3 Presentation outline Current trends in nano-satellite missions. Need for spectral efficient modulation schemes. Nano-satellite missions Case Study. High efficiency transmitters/pa architectures. Architectures trade-off. LINC/Chireix architecture. Measurement setup and results. Thesis conclusion. Scope for further research. Motivation Requirement Architecture trade-off Prototype and measurements Conclusion and scope for future work. 3

4 Nano-satellites timeline Universities - Space system engineering tool/ education. - Simple tech demo AAU Cube-1 Universities collaboration with industries: - Space system engineering tool/ education. - Technology demonstration. - Research test-bed. Delfi-C3 Universities - Space system engineering tool/ education - Simple tech demo Industry missions: - Space startups. - Technology demonstration. - Research test-bed. Universities - Space system engineering tool. - complex science missions. Industry missions: - Technology demonstration. - Research test-bed. - University collaboration. - Remote sensing payloads. Space Agencies: - Technology demonstration. - Research test-bed. CanX-3 (BRITE) Flock 4

5 Current trends: Nano-satellite launches nano-satellites launched between 2003 and nano-satellites considered. (184 downlink RF transmitters) Mission types, downlink data rates, modulation scheme and frequency bands used. 5

6 Current trends: Analysis of nano-satellite launches between 2003 and 2013 Steep increase from 2012 to 2013: 336% increase. Trend expected to continue in coming years (2 to 3 times increase in 2014)[1]. Nano-satellite cluster launches[2]: frequency coordination very challenging. Paradigm shift in the mission types. The paradigm shift led to higher downlink data rates in 2013 leading to higher frequency bandwidth requirements. [1] [2] Minotaur 1 rocket: 29 satellites in single launch, DNEPR (21 st Nov 2013): 32 satellites in a single launch 6

7 Due to the limited availability of bandwidth in VHF and UHF bands, missions have started moving to S-band and X-band. A need to start investigating spectral efficient modulation schemes. Wiser to adopt CCSDS and ECSS, instead of developing something separately for nanosatellite missions. Not very straight forward to implement an efficient transmitter architecture that complies with CCSDS and ECSS standards. CCSDS: Consultative committee for Space Data Systems ECSS: European Cooperation for Space Standardization 7

8 CCSDS and ECSS Recommendations CCSDS and ECSS recommendation Compatible with ESA ground station Bandwidth compliance S-band: 300 khz (Rs<10ksps) 1200 khz (10 < Rs < 60ksps) 6 MHz (Rs < 2 Msps) X band: 10 MHz (Rs > 2Msps) Ka band: No constraints! Spectral emission mask compliance Rs < 2Msps: 43 db/decade Rs > 2Msps: 60 db/decade Recommended modulation schemes Rs < 2Msps: BPSK, QPSK, OQPSK. Rs > 2Msps: GMSK, OQPSK, 8PSK, 16-APSK, 32- APSK and 64-APSK. CCSDS: Consultative committee for Space Data Systems ECSS: European Cooperation for Space Standardization 8

9 High elevation Minimum path-loss Adaptive coding and modulation using SDR for maximum throughput 32-APSK 16-APSK 8-PSK QPSK Low elevation Maximum path-loss 9

10 Challenges in implementing spectral efficient modulation schemes Modulation M-PSK 16-APSK 16-QAM 32-APSK 32-QAM PAPR 0dB 1.1dB 2.6 db 1.4 db 3.9 db PAPR contribution by the constellation alone. Roll-off PAPR 7.5dB 5.8dB 4.6dB 3.7dB 3.4dB PAPR contribution due to SRRC filter for different roll-off factors. Non-constant envelope profile of PSK due to SRRC filters. Amplitude and Phase modulation improves spectral efficiency but PAPR increases. Efficiency of the PA drops due to amplitude modulation. PAPR (Peak to Average Power Ratio): which is the ratio between peak power of the signal envelope to the average power of the envelope 10

11 Transmitter architecture 100 % Fig1. General transmitter architecture. Transmitter can be the most power hungry subsystem (Peak power). Thus the need to choose a power efficient architecture. Conventional PA classes not suitable to amplify spectral efficient schemes. Fig2. Efficiency vs Linearity for conventional PA modes. 11

12 Efficiency and linearity enhancement architecture Efficiency/linearity enhancement technique. Doherty Kahn/EER (Envelope Elimination and Restoration) Envelope Tracking (ET) Switched Capacitor Digital Power Amplifier (SCDPA) LINC (Linear Amplification using Nonlinear Components) Fig3. Efficiency and linearity enhancement techniques. 12

13 Trade-off Fig4. performance trade-off between different transmitter/pa architectures. Complexity/cost given the highest weight: Keep it simple for space application. Circuit over-head: Additional circuitry for biasing, signal synchronization etc. Form-factor: Smaller form factor preferred for nano-satellites. Performance in Power back-off: Not given a very high priority because, not dealing with very high PAPR. Efficiency and linearity: Given lowest priority. All the discussed architectures perform equally good for the specified PAPR. 13

14 LINC architecture Signal Component Separation Amplification Power Combiner Fig5. General LINC architecture Separate non-constant envelope into two constant envelope signals. Amplify using high efficiency, non-linear PA. Combine the amplified signals to reproduce the amplified non-constant envelope signal. 14

15 LINC: Principle of operation Fig6. (red dots) 16-APSK modulation Scheme, (blue circle) constant envelope signals. sin (t ) r(t)e j( t ( t )) r(t) rmax j ( t ) j ( t ) e e Fig7. (blue dots) 16-APSK modulation Scheme through SRRC filter(roll-off = 0.5), (red circle) constant envelope signals. sin (t ) rmax j ( t ( t ) ( t )) e e j ( t ( t ) ( t )) 2 sin (t ) S1(t ) S 2(t ) 15

16 LINC PA: Amplifier cell Drain Efficiency (DE) for different Classes Class AB B C CMCD VMCD E F F -1 J DE (%) Class-E has the highest efficiency, but needs signal pre-distortion when implemented in LINC. - Class-D (current mode) provides high efficiency and considerable ACPL but implementation requires two transistors/cell. - Class-F, F -1 are the most suitable choices for LINC based on this study. Fig8. Output spectrum of 16-QAM for different classes of operation. Ref: Montesinos, Ronald, Corinne Berland, Mazen Abi Hussein, Olivier Venard, and Philippe Descamps. "Analysis of RF power amplifiers in LINC systems. International Journal of Microwave and Wireless Technologies 4, no. 01 (2012):

17 LINC combiners RF power combining for LINC. Wilkinson power combiner Hybrid coupler/ 180 deg rat-race Chireix combiner Power recycling using RF to DC convertors. Spatial power combining using antenna array. Lossy combining: Wilkinson Power Combiner, Hybrid coupler, Rat-race. Lossless combining: Chireix combiner, Spatial power combiner. 17

18 LINC combiners Fig10. Efficiency vs outphasing angle For WPC and Chireix combiner. Fig11. Isolation between the input ports of WPC and Chireix combiner. 18

19 LINC/Chireix Architecture Fig12. LINC/Chireix PA from CATENA microelectronics B.V 19

20 LINC Measurement setup to measure the linearity and efficiency. Fig13. LINC measurement setup 20

21 Measurement Results Fig QAM with 20 degrees compensation stub. EVM: 0.3% Fig APSK with 20 degrees compensation stub. EVM: 0.27% 21

22 Measurement summary Modulation scheme 16-QAM 16-APSK 32-QAM 32-APSK 64-QAM Compensation angle EVM RMS % ACLP (dbc) o/p power dbm PAE % 0 deg deg deg deg deg deg deg deg deg deg

23 Conclusions and recommendations for future work-1 Need for spectrally efficient modulation scheme justified. CCSDS and ECSS standards instead of developing something new for nanosatellites. Efficiency and linearity enhancement technique needed for adaptive coding and modulation architectures. LINC architecture, most feasible solution for nano-satellites. A proof-of-concept was validated using a LINC/Chireix PA designed by CATENA. Chireix combiner needs appropriate compensation component based on the PDF of the modulation scheme for best performance. LINC architecture ideal for single chip solution. 23

24 Scope for future work-1 The best PAE achieved was ~ 51% in the case of 16-QAM and 16-APSK. The harmonic tuning circuit in the present system can be improved. Inverse-F PAs, a better choice compared to Class-F PAs at lower frequencies. Alternate power combining techniques need to be investigated further. (spatial power combining, use of hybrid-chireix) Fig17. Impedance seen by the drain of the PA 24

25 Scope for future work-2 Improvement in the measurement circuit: Proposed change in measurement setup to improve temperature drifts. Fig18. proposed measurement setup 25

26 Spatial power combining: Simulations were performed on a crossed dipole configuration: Rx Antenna S: +I,-I,+Q,-Q MAXIM 2021 S(t) Tx Antenna 1 RIO1 RIO0 S1: +I,-I,+Q,-Q MAXIM 2021 S1(t) Driver + PA1 Tx Antenna 2 PXI National Instruments S2: +I,-I,+Q,-Q MAXIM 2021 S2(t) Driver+PA2 VSG Power Divider/Combiner Power Divider/Combiner Fig19. Spatial power combining LINC. 26

27 Thank you! 27

28 Case study Nano-satellite mission cases Telemetry downlink Remote sensing payload Data services Spacecraft housekeeping data - Nano-satellite telemetry. - Full orbit data required subsystems. - Sampling rate: 10 sec. - Total data/day: 7.7 Mbits. - Data-rate: 36 kbps Optical sensor payload: - Optical payload. - Resolution: 16MP - Number of images/day: Required downlink data-rate for 3 satellites and 1 ground station: 7Mbps VDE-Sat: - VHF data exchange for maritime service. - Freq: MHz. - Max bandwidth: 50 khz. - Symbol rate: 40 ksps 28

29 Transmitter requirement based on case study Spacecraft housekeeping data MISC-1 payload downlink [Remote sensing payload] VDE-sat downlink. Frequency Band UHF 8.4 GHz [X-band] MHz [VHF] Available bandwidth Downlink data rate Occupied bandwidth if BPSK used. Modulation scheme Occupied bandwidth 25 khz 10 MHz 50kHz 36 kbps 7 Mbps 40 ksps (160 kbps) 50 khz 10 Mhz 200 khz QPSK/OQPSK 16-APSK 16-APSK 23.3 khz 6.3 MHz 50 khz Transmit power 500 mw 3 W 6 W PAPR [db] Peak to Average Power Ratio calculated including a SRRC filter with a roll-off of

30 Appendix. VDE-Sat concept 30

31 Market study and launch forecast done by SpaceWorks in

32 Link budget: Telemetry downlink 32

33 Link budget: MICE-1 33

34 Link budget: VDE-Sat 34

35 PDF of 16-APSK 35

36 Class-F PA 36

37 0 degrees out-phasing angle Antenna combiner Fig. (left) 3D radiation plot (peak gain:3 db), (Right) Polar plot at Phi-90 degrees, 3dB beam-width ~140 deg 37

38 30 degrees out-phasing angle. Fig. (left) 3D radiation plot (peak gain:3 db), (Right) Polar plot at Phi-90 degrees, 3dB beam-width ~100 deg 38

39 60 degrees out-phasing angle. Fig. (left) 3D radiation plot (peak gain:3 db), (Right) Polar plot at Phi-90 degrees, 3dB beam-width ~120 deg 39

40 90 degrees out-phasing angle. Fig. (left) 3D radiation plot (peak gain:3 db), (Right) Polar plot at Phi-90 degrees, 3dB beam-width ~180 deg 40

41 LINC/Chireix architecture 41

42 Hybrid-Chireix combiner 42