1. Additional RF system issues: Amplifier linearization Reference Phase distribution Master Clock Anders J Johansson Lund University

2. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Low Level RF (LLRF) A/D D/A LO LOAD Klystron FPGA Modulator LLRF

3. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Linearization of power amplifiers Linearization of PA common in mobile communications Makes it possible to use efficient amplifiers and still fulfill transmitt spectrum masks.

4. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Amplifier compression Power Amplifier Linearization Techniques, an Overview, Joel L. Dawson

5. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Why linearization in mobile communications Increased demands due to: –Complex modulation schemes –Muliple channels per amplifier –Running at compression/class C for efficiency

6. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 List of linearization techniques Power backoff Predistortion Adaptive predistortion Feedforward Linearization Envelope elimination and restoration (EER) LINC (LInear amplification with Nonlinear Components) Cartesian feedback List by Joel L. Dawson

7. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Power backoff Pin Pout 1st 3rd

8. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Predistortion Linearization High Power Amplifiers, Allen Katz, Linearizing Technologies

9. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Adaptive predistortion Power Amplifier Linearization Techniques, an Overview, Joel L. Dawson

10. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Feedforward Linearization Power Amplifier Linearization Techniques, an Overview, Joel L. Dawson

11. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 RF and Microwave Power Amplifier and Transmitter Technologies — Part 3, F. H. Raab et. Al. Envelope elimination and restoration

12. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 RF and Microwave Power Amplifier and Transmitter Technologies — Part 3, F. H. Raab et. Al. Envelope tracking

13. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 RF and Microwave Power Amplifier and Transmitter Technologies — Part 3, F. H. Raab et. Al. LINC

14. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Indirect Feedback Linearization High Power Amplifiers, Allen Katz, Linearizing Technologies

15. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Power Amplifier Linearization Techniques, an Overview, Joel L. Dawson LINCartesian Feedback

16. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 LLRF with linearization A/D D/A LO LOAD Klystron FPGA Modulator A/D

17. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Some details Method I: Power backoff –Classical in accelerators –Expensive in terms of efficinecy, especially with klystrons Method II: Predistortion/adaptive predistortion –Either at baseband or RF –Depends on having a good amplifier model Method IV: Cartesian feedback –Needs good phasematching between mixers –Stability concerns

18. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Benefits for Accelerators Narrowband signal, i.e. less worries about broadband performance.

19. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Investigate the different options from the viewpoint of ESS –Klystrons / IOTs –Narrow bandwidth –Huge power Overhead from FPGA/DSP minimal Needs accurate non-linear models of amplifiers! Development of Linearization for ESS

20. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Time and Synchronization ESS needs: –A common clock to timestamp events –Stable generation and distribution of pulse events –Stable reference phase for RF

21. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Phase reference Crystal oscillators –Very low phase noise –Big drift –Cheap Atomic clocks (cesium /rubidium ) –Low drift –Large phase noise –Costly Maser –Very Low drift –Expensive

22. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Stability and phase noise Two main measures of oscillators and clocks –Allen variance or stability Slow variations ” Allan variance is defined as one half of the time average of the squares of the differences between successive readings of the frequency deviation sampled over the sampling period” –Phase noise Fast variations

23. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Phase noise dBc/Hz vs. Offset frequency in Hz

24. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Stability Allan stability versus integration time (seconds)

25. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 OCXO: Oven Controlled Crystal Oscillators Stabilize a crystal oscillator by putting it inside a temperature controlled oven (which in turn may be inside an temperature controlled oven etc.) May still be tuned by voltage and/or temperature Typically 10 MHz.

26. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 PLL: Phase Locked Loop How to use a stable low frequency oscillator to control a high frequnecy source. Phase Detector ref VCO Low Pass filter Divide by M

27. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Master clock schematic (tentative) GPS 1pps OCXO PLL Frequency Divider/ Distribution 10MHz 1pps Tuning Real time clock Timestamps 10MHz Reference Frequency Generation 704 MHz 352 MHz Control system GPS Time delta logger

28. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Reference phase distribution The reference phase needs to be distributed to all LLRF stations Taken from the master clock Linear or star topology Example: linear distribution

29. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Reference phase distribution Master Oscillator LLRF PID

30. Lund University / Dept. Of Electrical and Information Teechnology / ESS RF Workshop / 14 Dec. 2012 Conclusions Investigate possibility of running the power amplifiers (klystrons) close(r) to saturation. Design a master clock Design a phase distribution network