RF Noise Generator

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Design

  • Useful as a filter test signal source
    • Pass filters
    • Crystal filters
  • From Experimental Methods in RF Design
    • Fig 7.72
    • Described as "not flat"
  • "Junk box" parts
    • (2) 2N3904 transistors
    • (2) 5V (nominal) zener diodes
  • Noise figure -50 dBm @ 10 MHz

Schematic

Ng-sch-prototype.PNG

Prototype

  • Unique nodes in red
  • Prototype on single sided copper clad PCB
  • KiCAD zener packages have backwards silkscreen (will need to fix on OshPark PCBs)

NG-layout.PNG

Meaurements

  • 12V, 43mA current draw
  • Rigol DS1054Z
    • 50 MHz scope with mods
    • UltraScope settings
      • SCAL 1.00 V
      • H 200nS
    • FFT settings
      • CF = 16 MHz
      • 2 MHz start, 50 MHz stop
  • RBW 416.6 KHz
  • Background noise
  • Generator off
  • Average ~ -64 dB

NG OFF.PNG

  • Noise Generator On
  • Falls off with frequency, but better than -50 dB

NG ON.PNG

  • Measured performance per EMiRFD (predicted - 50 dB)

High Pass Filter

Assembly Sheet

RF Noise Generator Rev 1

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