RF signal generators have an output impedance of 50 Ω.

If the load impedance matches the output impedance, the voltage at the signal output connector is at the needed level.



In the preceding figure, the required output voltage is ±5 V. The relationship between the output voltage and the load can be calculated as follows:

V o u t = [ R L ( R L + R O ) ] × [ V S ]

where

  • Vout = the voltage level delivered to RL
  • RL = the load impedance in ohms
  • RO = the output impedance on the NI RF signal generator
  • VS = the voltage level generated by the source previous to RO

By default, RO = 50 Ω.