0/10/20/30 dB Attenuator

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ATTEN4 CHINA PCB.PNG

Specs

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

  • 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

ATTEN 0DB 1MHz TO 900MHz.png

10 dB

ATTEN 10DB 1MHz TO 900MHz.png

20 dB

ATTEN 20DB 1MHz TO 900MHz.png

30 dB

ATTEN 30DB 1MHz TO 900MHz.png

Calibrating NanoVNA through the card

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

0 dB

ATTEN 0DB 1MHz TO 900MHz Cal.png

10 dB

ATTEN 10DB 1MHz TO 900MHz CalOnBoard.png

20 dB

ATTEN 20DB 1MHz TO 900MHz CalOnBoard.png

30 dB

ATTEN 30DB 1MHz TO 900MHz CalOnBoard.png

Analysis of Results

  • 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