Software Defined Radio for Beginners

Transcription

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2 Software Defined Radio for Beginners July 19, 2014 Stephen Hicks, N5AC

3 SDRs for Beginners Agenda What is an SDR? History of Amateur SDR Technologies that make an SDR Examples of SDRs Benefits and uses of SDRs

4 What is an SDR?

5 What is an SDR?

6 What is an SDR? SDR is a spectrum Some radios are clearly NOT Other radios clearly ARE Many permutations is-between So what makes up an SDR?

7 Back to Basics Radio Magic

8 Back to Basics MIXER DEMOD FILTER LO IF AMP AUDIO AMP

9 Multi-Conversion 3 15 khz Roofing Filter 36kHz MHz 455kHz Distortion DEMOD

10 Engineering Design Process Draw a block diagram Simulate Draw a schematic Simulate Build Measure and adjust

11 Engineering Design Process Does the circuit match the simulation exactly? NO WHY? Components are not ideal There are losses not modeled Component variance Component capabilities Result: Never as good as the simulation

12 Can t we account for component differences? In some cases, YES Some materials work better in some cases Compensating circuits can be added In some cases, NO There will always be issues

13 Components and Problems Resistors Capacitors Inductors Transistors Mixers Amplifiers Crystals Filters Lot Variance Parasitics Non-linearities Thermal variance Electrically induced variance IMD Manufacturing variance The list goes on

14 Filtering: The Goal Brick Wall Filter response Block undesired Pass desired frequency

15 Filtering Practical limits to achievable results Suggested capacitor model, Tantalum capacitor

16 Block Diagram Key Yellow blocks are ANALOG Green blocks are DIGITAL

17 Filter Design: Simulation Sampled signals passed through simulated ideal components Results could even be played out a speaker FILTER SIMULATION DAC

18 Filter Design: Simulation Limits Analog: poles Digital: unlimited except for latency. Maybe 200, 1000, more! Could a computer run the simulation IN THE RADIO? ADC FILTER SIMULATION DAC

19 Presto: Software in the Radio MIXER DEMOD FILTER IF AMP AUDIO AMP LO ADC FILTER DAC Is this an SDR?

20 DEFINITIONS: Software Defined vs. Controlled CONTROLLED Computer Control of Fixed Capabilities (frequency, band, etc) DEFINED Modulation, Demodulation, filtering, and processing; as well as Control Capabilities Software Defined and Upgradeable

21 Filter Shape Factor FLEX-5000 Note Brick Wall & Flatness Radio Y Radio Z Radio X

22 500 Hz Brick Wall Filter 6dB Bandwidth 487 Hz, 60dB Bandwidth 660 Hz, Shape Factor ~ Bin FFT and 2048 Tap Filter

23 2.8KHz SSB Filter Spectrum 6dB Bandwidth 2587 Hz, 60dB Bandwidth 2756 Shape Factor ~1.06, 2048 Tap Filter

24 Software Demodulation MIXER ADC FILTER DEMOD IF AMP AUDIO AMP LO FILTER DAC Now, is this an SDR?

25 Software Demodulation and Baseband New demod schemes added later! Precise Filtering Advanced Noise Reduction ADC DEMOD IF AMP AUDIO AMP FILTER DAC

26 PowerSDR - A FlexRadio Original!

27 Economics 101 What is the marginal cost of a 2nd receiver in an analog radio? ANSWER: the cost of the added parts (plus amortized engineering)

28 ADC DEMOD ADC DEMOD MIXER FILTER FILTER What if I want 2 RX? IF AMP LO FILTER DAC AUDIO AMP 2x analog components $2x

29 What are we trying to achieve? Remove distortion Better performance Flexibility to change or add features Ability to tailor the radio quickly Never before possible noise mitigation Never before possible capabilities Can we do more?

30 What about this analog stuff? MIXER ADC FILTER DEMOD IF AMP AUDIO AMP LO FILTER DAC

31 Direct Sampling MIXER DEMOD ADC FILTER AUDIO AMP LO FILTER DAC Now, THAT s an SDR!

32 Why doesn t everyone do Direct Sampling? 192kHz 64bits = 12Mbps MIXER ADC FILTER DEMOD IF AMP AUDIO AMP LO FILTER DAC

33 10Mbps

34 Direct Sampling 250MHz 16bits = 4Gbps MIXER DEMOD ADC FILTER AUDIO AMP LO FILTER DAC Now, THAT s an SDR!

35 4Gbps is Mbps cables 4-1Gbps cables That s a LOT of data! The most modern home networking you can buy, can t handle this

36 Direct Sampling Benefits + Distortion minimized antenna): best signal clarity + n-receivers, n-panadapters and varying widths see more bands, more receivers + Extremely high dynamic range: operate in worst conditions + Extreme flexibility through reprogrammability (ultimate SDR): future benefits Technically challenging to design

37 Economics 101 What is the marginal cost of a 2nd receiver in an digital radio (SDR)? ANSWER: the cost of the extra processing power (plus amortized engineering) think Moore s law Processing Power = FPGA

38 Direct Sampling ALL of HFALL of HF digitized MIXER DEMOD ADC FILTER AUDIO AMP LO FILTER DAC Now, THAT s an SDR!

39 Direct Sampling MIXER DEMOD MIXER FILTER DEMOD ADC FILTER NCO AUDIO AMP DAC How many do you want?

40 We are called to be the architects of the future, not it s victims R. Buckminster Fuller

41 Design Options: #1: ADC and a hose RADIO ADC FPG A PC Radio is ADC FPGA Ethernet Leverage PowerSDR; minimal SW investment

42 Pros & Cons for Remote Processing + Lots of DSP Power in Computer: easy, ubiquitous + Plenty of expertise available Requires a computer always on Control via RDP / VNC / GotoMyPC, etc. Audio via Skype, etc. Hard and not particularly bandwidth friendly

43 Direct Sampled - Remote ANAN-100D Hermes HPSDR HPSDR RF DSP DSP CTRL

44 Design Options: #2: ADC + FPGA + DSP/uP RADIO ADC FPG A CHL BB DSP PC/ OTHER Radio reduces bandwidth to minimum before Ethernet Oh gosh: start over with SW: big investment!

45 Integrating the Baseband Processor Key Benefits Consistent performance independent of PC Minimized network bandwidth (think remote) Minimization of system problems Self-contained, rapid startup platform Spectrum displays (panadapter) independent of available network bandwidth

46 Example Third Generation SDR Architecture 7.9Gbps + 1Gbps dd

47 Spectrum Display BW 10MHz 1MHz <500kbps 10MHz 1MHz 770Mbps 77Mbps 1500:1 150:1 Bandwidth Difference

48 Multi-mode Waterfall

49 Waterfall plus Bandscope

50 Ionosonde trails

51 CW Skimmer x4

52 Digital Modes

53 More Functional Displays

54 WSPR times 4!

55 EasyPAL

56 TX6G: A Picture is worth 1,000 words

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