0/10/20/30 dB Attenuator

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ATTEN4 CHINA PCB.PNG

Specs[edit]

DC-4.0GHz 200mW DC 4.0GHz RF Fixed Attenuator SMA Double Female Head 0dB 10dB 20dB 30dB


  • From the AliExpress listing
    • $5 with shipping (2021-10)
  • Frequency range: DC - 4.0GHz
  • Maximum power: 23dBm (200mW)
  • Standing wave ratio: ≤ 1.20
  • System impedance: 50Ω
  • RF interface: SMA double female head (Outer screw inner hole)
  • Attenuation:
    • Direct: 0dB (reference)
    • Level 1: 10 ± 0.8 dB
    • Level 2: 20 ± 1.1 dB
    • Level 3: 30 ± 1.5dB

Measurements[edit]

  • Characterized filters uinf NanoVNA
    • 1 to 900 MHz (card spec is up to 4 GHz)
    • Through-calibrated with SMA barrel and same cables was flat

0 dB[edit]

ATTEN 0DB 1MHz TO 900MHz.png

10 dB[edit]

ATTEN 10DB 1MHz TO 900MHz.png

20 dB[edit]

ATTEN 20DB 1MHz TO 900MHz.png

30 dB[edit]

ATTEN 30DB 1MHz TO 900MHz.png

Calibrating NanoVNA through the card[edit]

  • Calibrate on card 0 dB (pass-through connections)

0 dB[edit]

ATTEN 0DB 1MHz TO 900MHz Cal.png

10 dB[edit]

ATTEN 10DB 1MHz TO 900MHz CalOnBoard.png

20 dB[edit]

ATTEN 20DB 1MHz TO 900MHz CalOnBoard.png

30 dB[edit]

ATTEN 30DB 1MHz TO 900MHz CalOnBoard.png

Analysis of Results[edit]

  • Board uses 5% (3-digits) resistors
    • Can result be 1dB with 5% resistors?
  • Tracks are wide but 50 Ohms?
  • 0805 resistors limit power handling to 200 mW max
  • Lots of ground stitching
  • Compared to Homebrew attenuator
    • Homebrew is more accurate in DC-100 MHz range
    • Leads may act as inductors/capacitors

ATTEN 30DB(HOMEBREWvsPURCHASED) 1MHz TO 900MHz.png

Improvements in design[edit]