Drahtlose Kommunikation und SDR

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fg.workshop vom 27.03.2014

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Drahtlose Kommunikation und SDR

  1. 1. Introduction modulation Receivers, how do they work? SDR Demo SDR a short introduction Oliver Wisler March 27, 2014 Oliver Wisler SDR a short introduction
  2. 2. Introduction modulation Receivers, how do they work? SDR Demo 1 Introduction 2 modulation amplitude modulation frequency modulation phase shift keying other modulations 3 Receivers, how do they work? simple receiver modern receivers 4 SDR How does it work? legal Boundaries 5 Demo Oliver Wisler SDR a short introduction
  3. 3. Introduction modulation Receivers, how do they work? SDR Demo technical terms RX receiver TX transmitter HF high frequency, general term for radio frequencies LF low frequency, everything audible SNR signal to noise ratio, quantifies the quality of reception Oliver Wisler SDR a short introduction
  4. 4. Introduction modulation Receivers, how do they work? SDR Demo frequency ranges <3 MHz VLF submarines 3-30 MHz HF ham radio, worldwide communication 30-300 MHz VHF broadcasting, handheld radio 300-3 GHz UHF WLAN, microwave, GPS >3 GHz SHF radar, astronomy, satellites Oliver Wisler SDR a short introduction
  5. 5. Introduction modulation Receivers, how do they work? SDR Demo modulation, what’s that? Definition a process of mixing different signals to obtain a new one usually one of these signal is sinusoid tech term for converting LF to HF Oliver Wisler SDR a short introduction
  6. 6. Introduction modulation Receivers, how do they work? SDR Demo amplitude modulation amplitude modulation invented around 1900 one of the first methods to transmit voice easy and cheap to receive (”Volksempf¨anger” in WW2) prone to interference wastes a lot of energy transmitting the carrier has a small bandwidth (even less with SSB) still used for HF (< 30Mhz) broadcasts Oliver Wisler SDR a short introduction
  7. 7. Introduction modulation Receivers, how do they work? SDR Demo amplitude modulation AM problem time amplitude carrier signal Oliver Wisler SDR a short introduction
  8. 8. Introduction modulation Receivers, how do they work? SDR Demo amplitude modulation amplitude modulation time amplitude carrier signal AM Oliver Wisler SDR a short introduction
  9. 9. Introduction modulation Receivers, how do they work? SDR Demo amplitude modulation amplitude modulation minimal schema Oliver Wisler SDR a short introduction
  10. 10. Introduction modulation Receivers, how do they work? SDR Demo amplitude modulation amplitude modulation detail time amplitude carrier signal Oliver Wisler SDR a short introduction
  11. 11. Introduction modulation Receivers, how do they work? SDR Demo amplitude modulation amplitude modulation spectrum frequency power LSB USB signal carrier Oliver Wisler SDR a short introduction
  12. 12. Introduction modulation Receivers, how do they work? SDR Demo frequency modulation frequency modulation patented 1933 better SNR than AM when good reception needs more bandwidth than AM widely used for frequencies above 30Mhz Oliver Wisler SDR a short introduction
  13. 13. Introduction modulation Receivers, how do they work? SDR Demo frequency modulation FM problem time amplitude carrier signal Oliver Wisler SDR a short introduction
  14. 14. Introduction modulation Receivers, how do they work? SDR Demo frequency modulation frequency modulation time amplitude signal FM Oliver Wisler SDR a short introduction
  15. 15. Introduction modulation Receivers, how do they work? SDR Demo frequency modulation frequency modulation spectrum frequency power Oliver Wisler SDR a short introduction
  16. 16. Introduction modulation Receivers, how do they work? SDR Demo phase shift keying PSK problem time amplitude signal 0 1 1 0 Oliver Wisler SDR a short introduction
  17. 17. Introduction modulation Receivers, how do they work? SDR Demo other modulations other types of modulations QPSK PSK with φ = π 2 , each shift encodes 2 bits FSK encode bits with 2 frequencies QAM combination of AM and PSK, up to 12 bits per symbol Oliver Wisler SDR a short introduction
  18. 18. Introduction modulation Receivers, how do they work? SDR Demo simple receiver simple AM receiver schema antenna filter amplifier demodulator amplifier speaker receiver Oliver Wisler SDR a short introduction
  19. 19. Introduction modulation Receivers, how do they work? SDR Demo simple receiver filter frequency power interference Oliver Wisler SDR a short introduction
  20. 20. Introduction modulation Receivers, how do they work? SDR Demo simple receiver amplifier amplifies the signal for demodulation needs to be linear (at least for AM) Oliver Wisler SDR a short introduction
  21. 21. Introduction modulation Receivers, how do they work? SDR Demo simple receiver demodulator a simple diode and two capacitors Oliver Wisler SDR a short introduction
  22. 22. Introduction modulation Receivers, how do they work? SDR Demo modern receivers Improving our receiver how/where can we improve our simple receiver? Oliver Wisler SDR a short introduction
  23. 23. Introduction modulation Receivers, how do they work? SDR Demo modern receivers better filters using 2 bandwidth filters steeper flanks special filters (eg notch) if we could fix the frequency, we could design better filters frequency power interference Oliver Wisler SDR a short introduction
  24. 24. Introduction modulation Receivers, how do they work? SDR Demo modern receivers better receiver antenna preamplifier mixer filter amplifier demodulator amplifier oscillator speaker mixing down fixed frequency Oliver Wisler SDR a short introduction
  25. 25. Introduction modulation Receivers, how do they work? SDR Demo modern receivers better antenna most important part many different designs available Oliver Wisler SDR a short introduction
  26. 26. Introduction modulation Receivers, how do they work? SDR Demo modern receivers receivers today 2nd mixer&filter stage adjustable oscillators (VCO) better demodulator superheterodyne receiver Oliver Wisler SDR a short introduction
  27. 27. Introduction modulation Receivers, how do they work? SDR Demo How does it work? Phasors Oliver Wisler SDR a short introduction
  28. 28. Introduction modulation Receivers, how do they work? SDR Demo How does it work? IQ we could just sample a signal at its Nyquist frequency difficult to process idea two samples short after each other Oliver Wisler SDR a short introduction
  29. 29. Introduction modulation Receivers, how do they work? SDR Demo How does it work? allows extraction of phase information removes ambiguity of frequency mixing Q I Oliver Wisler SDR a short introduction
  30. 30. Introduction modulation Receivers, how do they work? SDR Demo How does it work? FCD Project by HamSat small, relatively cheap SDR Range: 0.150MHz - 206MHz, 403MHz-2GHz (all Ham-radio bands) Resolution: 16Bit / 192kHz Oliver Wisler SDR a short introduction
  31. 31. Introduction modulation Receivers, how do they work? SDR Demo How does it work? FCD schema i2s sound serial bus i2c serial bus Oliver Wisler SDR a short introduction
  32. 32. Introduction modulation Receivers, how do they work? SDR Demo How does it work? FCD filter LNA low noise amplifier Oliver Wisler SDR a short introduction
  33. 33. Introduction modulation Receivers, how do they work? SDR Demo How does it work? Software gnuradio gqrx quisk Oliver Wisler SDR a short introduction
  34. 34. Introduction modulation Receivers, how do they work? SDR Demo DEMO Oliver Wisler SDR a short introduction
  35. 35. Introduction modulation Receivers, how do they work? SDR Demo sources DJ4UF Amateurfunklehrgang http://whiteboard.ping.se/SDR/IQ Datasheet of the FCD Pictures Wikipedia Oliver Wisler SDR a short introduction

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