Maker Pro
Maker Pro

50 Ohms Dummy Load PCB Layout


May 27, 2020
May 27, 2020
I am designing a 50 ohm 10 watts dummy load for 100-1000MHz frequency range. The signal strength should not exceed -10dBm. The load must be able to dissipate 5 watts minimum, that is +37dBm. The output to the test equipment must be no more than -10dBm. So I need an attenuation of 47dB but to make it easy lets say 50dB.

After the load as you can see in the schematic picture there is 3 different attenuators. The first one is 20dB attenuator for 5W dissipation, second one is 20dB-50mW dissipation and the last one is 10dB-50mW dissipation. You can see the values of the resistors on the schematic picture.

Specification for the PCB board:

Trace thickness : 0.036mm

Substrate height : 0.8mm

Trace Width : 1.5mm for 50ohms

Substrate Dielectric : 4.3

One thing that I couldn't figure out here is the width of the tracks when routing the attenuators as you can see some of them routed with a narrow line. Should it be as thick as 50ohms or something different considering the values, I don't know this because I have never seen it before. Long story short I need help with the circuit and routing the microstrip to have a good impedance match.

I have a problem with appliying this to a PCB board I know I should arrange R3-R6 symmetrically around the input connector, keeping the current path loops as short as physically possible. But I couldn't figure out myself. If you guys can guide me with placing the resistors and routing my problem will be solved.

I did something on my own you can check it below but I am pretty sure that is not the best way to do it. So waiting for your help.

Thank you for your time.


  • sche.PNG
    50.7 KB · Views: 13
  • br1.PNG
    69.7 KB · Views: 13