We are selling S-band HPAs for satcom applications.

A customer needs to obtain key RF characteristics of the S-Band HPA, specifically the wideband frequency response of carriers as a function of output level to understand out of band energy levels.

They gave the following example, but I am not sure how that can be done without a modulated input signal.


  • 1 Msymbol carrier at 0 dB, 3dB, 10 dB OBO (wrt 200 W output)
  • 5 Msymbol carrier at 0 dB, 3 dB, 10 dB OBO (wrt 200 W output)
  • 10 Msymbol carrier at 0 dB, 3 dB, 10 dB OBO (wrt 200 W output)

Will the P1dB and OIP3 answer their question? If not, would you please advise on what is needed to be performed and how?

  • \$\begingroup\$ Will the P1dB and OIP3 answer their question? If you also add the gain of the amplifier then I think it should be enough because from those numbers they should be able to determine if the amplifier is "good enough". I think that the "x Msymbol carrier" doesn't tell us anything as the modulation type is unknown. And even if you did know the modulation, for PAs only the bandwidth is important. For an RF system designer, generally the gain, P1dB and IP3 are all that is needed to assess what performance can be achieved. \$\endgroup\$ Sep 24 at 15:14
  • \$\begingroup\$ As a minimum, you need to know the peak to RMS of the signal they're passing through the amplifier. Some signals are designed with this small, to make use of more efficient amplifiers. P1dB is next to useless, OIP3 is better, but still not well correlated to the performance with a real signal. Ideally, you'll measure with the customer's signal to establish the correlation between OIP3 and the signal performance, hiring a specific signal source if necessary. With luck, he'll then trust those figures and you can do future tests with the simpler signal. \$\endgroup\$
    – Neil_UK
    Sep 24 at 20:09

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.