RF Noise Generator

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NoiseGen-P783-720px.jpg

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

tinySA Measurements

  • 1-30 MHz
  • Power Off

NoiseGenOnTinySA Off.PNG

  • Power On

NoiseGenOnTinySA On.PNG

  • 100 KHz-1 MHz
  • Power Off

NoiseGenOnTinySA Off 100KHz-1MHz.PNG

  • Power On
  • Lot more energy at ~400 KHz
  • -30 dB

NoiseGenOnTinySA On 100KHz-1MHz.PNG

Rigol DS1054Z Measurements

    • 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)

Better Design

  • C1 is connected Emitter of Q1 to GND to reduce power supply noise
  • Higher noise than EMiRFD design
  • Falls off quickly with frequency
    • Usable from 1-10 MHz
    • ~ -60 dBm

Better Noise Gen schematic.png

  • Off

V2-NoiseGenOnTinySA OFF 1MHz-10MHz.PNG

  • On

V2-NoiseGenOnTinySA On 1MHz-10MHz.PNG

Build / Enclosure

  • Used very old, but high quality chassis mount BNC connector
    • Silver connector has a nice patina
  • Built onto Single Side PCB material
    • Acts as ground plane
    • Pads cut from PCB material and superglued down onto the Base PCB
  • Hot glued down into plastic enclosure

NoiseGen-P783-720px.jpg

NoiseGen-P790-720px.jpg

NoiseGen-P787-720px.jpg

Assembly Sheet

RF Noise Generator Rev 1