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HF-VFO using an AD9854

HF-VFO using an AD9854. Direct Digital Synthesizer. Craig Johnson, AAØZZ. FDIM 2003. May 15, 2003. AGENDA Introduction What Does A DDS Do? Block Diagram Hardware Description Software Description Results HF-VFO with an R2Pro Extensions Concluding Remarks Questions. AAØZZ. FDIM 2003.

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HF-VFO using an AD9854

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  1. HF-VFO using an AD9854 Direct Digital Synthesizer Craig Johnson, AAØZZ FDIM 2003 May 15, 2003

  2. AGENDA • Introduction • What Does A DDS Do? • Block Diagram • Hardware Description • Software Description • Results • HF-VFO with an R2Pro • Extensions • Concluding Remarks • Questions AAØZZ FDIM 2003 May 15, 2003

  3. Block Diagram LEDs Clock LP Encoder DDS Amp I out Main Filter Encoder PIC PIC LP Q out Amp Filter Push Buttons Display AAØZZ FDIM 2003 May 15, 2003

  4. What Does A DDS Do? DDS D A C F T W 01101011 Clock AAØZZ FDIM 2003 May 15, 2003

  5. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word AAØZZ FDIM 2003 May 15, 2003

  6. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word 248 AD9854 FTW = Desired Freq X ------------------ Frequency (Hz) AAØZZ FDIM 2003 May 15, 2003

  7. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word 248 AD9854 FTW = Desired Freq X ------------------ Frequency (Hz) 232 AD9850 FTW = Desired Freq X ------------------ Frequency (Hz) AAØZZ FDIM 2003 May 15, 2003

  8. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word Examples (125 MHz Clock) AAØZZ FDIM 2003 May 15, 2003

  9. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word Examples (125 MHz Clock) 1 Hz 1 MHz AAØZZ FDIM 2003 May 15, 2003

  10. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word Examples (125 MHz Clock) 1 Hz 1 MHz AD9850: 34 AAØZZ FDIM 2003 May 15, 2003

  11. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word Examples (125 MHz Clock) 1 Hz 1 MHz AD9850: 34 ~34 Million AAØZZ FDIM 2003 May 15, 2003

  12. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word Examples (125 MHz Clock) 1 Hz 1 MHz AD9850: 34 34.359738 x 106 AAØZZ FDIM 2003 May 15, 2003

  13. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word Examples (125 MHz Clock) 1 Hz 1 MHz AD9850: 34 34.359738 x 106 AD9854: AAØZZ FDIM 2003 May 15, 2003

  14. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word Examples (125 MHz Clock) 1 Hz 1 MHz AD9850: 34 34.359738 x 106 AD9854: ~2.25 x 106 AAØZZ FDIM 2003 May 15, 2003

  15. What Does A DDS Do? DDS D A C F T W 01101011 Clock Frequency Tuning Word Examples (125 MHz Clock) 1 Hz 1 MHz AD9850: 34 34.359738 x 106 AD9854: ~2.25 x 106 ~2.25 x 1012 AAØZZ FDIM 2003 May 15, 2003

  16. What Does A DDS Do? DDS D A C F T W 01101011 Clock - On each clock pulse the DDS performs calculations AAØZZ FDIM 2003 May 15, 2003

  17. What Does A DDS Do? DDS D A C F T W 01101011 Clock - On each clock pulse the DDS performs calculations based on: Frequency Tuning Word AAØZZ FDIM 2003 May 15, 2003

  18. What Does A DDS Do? DDS D A C F T W 01101011 Clock - On each clock pulse the DDS performs calculations based on: Frequency Tuning Word Current phase AAØZZ FDIM 2003 May 15, 2003

  19. What Does A DDS Do? DDS D A C F T W 01101011 Clock - On each clock pulse the DDS performs calculations based on: Frequency Tuning Word Current phase - The DDS does look-up in sine table AAØZZ FDIM 2003 May 15, 2003

  20. What Does A DDS Do? DDS D A C F T W 01101011 Clock - On each clock pulse the DDS performs calculations based on: Frequency Tuning Word Current phase - The DDS does look-up in sine table - The D-to-A Converter (DAC) sets output voltages to desired levels AAØZZ FDIM 2003 May 15, 2003

  21. Quadrature AAØZZ FDIM 2003 May 15, 2003

  22. Block Diagram LEDs Clock LP Encoder DDS Amp I out Main Filter Encoder PIC PIC LP Q out Amp Filter Push Buttons Display AAØZZ FDIM 2003 May 15, 2003

  23. Hardware Description • 2 PIC Microcontrollers • AD9854 DDS • 5-v Regulator • 3.3-v Regulator • 125 MHz Reference Clock • Low Pass Filter (30 MHz) • RF Amplifier (ERA-3 MMIC) • Optical Encoder (or Mechanical) • Pushbuttons, LEDs • Display (LCD) AAØZZ FDIM 2003 May 15, 2003

  24. Prototype – Front AAØZZ FDIM 2003 May 15, 2003

  25. Prototype – Back AAØZZ FDIM 2003 May 15, 2003

  26. Software Description • Encoder PIC microcontroller • Main PIC Microcontroller • Display (LCD) • Pushbuttons and LEDs • Dual VFO (Split Operation) • Calibrate • AD9854 Initialization AAØZZ FDIM 2003 May 15, 2003

  27. Results • 2 Outputs – Quadrature (900) • 2-v p-p (10 dBm) I and Q • 0 - 30 MHz • Used in R2Pro (Don Huff, W6JL) • - “It’s HOT!” • 40 dB Opposite Sideband Rejection • -“40 dB sounds astonishingly good” • Spurs? • - “Low” (need more measurements) • Phase Noise? AAØZZ FDIM 2003 May 15, 2003

  28. Prototype – Operational AAØZZ FDIM 2003 May 15, 2003

  29. Prototype – LCD AAØZZ FDIM 2003 May 15, 2003

  30. HF-VFO with an R2Pro Receiver (Rick Campbell, KK7B) VFO Antenna Q I Analog Audio RF Audio Downconverter Signal Speaker Filters Amp Amp RF in Processor AAØZZ FDIM 2003 May 15, 2003

  31. Early Prototype Running R2Pro Don Huff, W6JL AAØZZ FDIM 2003 May 15, 2003

  32. Extensions • Add a Phase Lock Loop (PLL) • Upgrade the 125 MHz reference clock • Try different filter(s), amplifiers • Add a CW sidetone • Add Transmit/Receive keying delay logic for dual VFO operation • Change the 5-V Regulator • Add circuitry to change USB/LSB • Experiment with spread spectrum AAØZZ FDIM 2003 May 15, 2003

  33. Conclusion • Stable, usable VFO - as is • Ready for your extensions • Learning tool • PIC microcontrollers • DDS AAØZZ FDIM 2003 May 15, 2003

  34. Questions? AAØZZ FDIM 2003 May 15, 2003

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