This performance verication test must be performed with the EMC analyzer set in the spectrum analyzer mode.
This test is performed in two parts. Part 1 measures second harmonic distortion; part 2 measures third order intermodulation distortion.
To test second harmonic distortion, a 50 MHz low pass lter is used to lter the source output, ensuring that harmonics read by the EMC analyzer are internally generated and not coming from the source. To measure the distortion products, the power at the mixer is set 25 dB higher than specied. New test limits have been developed based on this higher power.
With 045 dBm at the input mixer and the distortion products suppressed by 70 dBc, the equivalent Second Order Intercept (SOI) is +25 dBm
(045 dBm + 70 dBc). Therefore, with 020 dBm at the mixer, and the distortion products suppressed by 45 dBc, the equivalent SOI is also +25 dBm (020 dBm + 45 dBc).
For third order intermodulation distortion, two signals are combined in a directional bridge (for isolation) and are applied to the EMC analyzer input. The power level of the two signals is 8 dB higher than specied, so the distortion products should be suppressed by 16 dB less than specied. In this manner, the equivalent third order intercept (TOI) is measured.
With two 030 dBm signals at the input mixer and the distortion products suppressed by 70 dBc, the equivalent TOI is +5 dBm (030 dBm + 70 dBc/2). However, if two 022 dBm signals are present at the input mixer and the distortion products are suppressed by 54 dBc, the equivalent TOI is also +5 dBm (022 dBm + 54 dBc/2).
Performing the test with a higher power level maintains the measurement integrity while reducing both test time and the dependency upon the source's noise sideband performance.