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IMD

Measuring harmonics

After activating the harmonics measurement a keypad appears for entering the approximate frequency of the fundamental. This does not have to be an accurate number as the tinySA will search for the strongest signal

Next the IMD measurement screen appears

Four markers are activated

1. automatically finds the strongest signal and should be the fundamental and the marker is set to a tracking REFERENCE marker
2. automatically finds the second harmonic and the marker is set to a DELTA marker and level is displayed in dBc
3. automatically finds the third harmonic and the marker is set to a DELTA marker and level is displayed in dBc
4. automatically finds the fourth harmonic and the marker is set to a DELTA marker and level is displayed in dBc

The level of the fundamental should not exceed -20dBm, preferably below -30dBm. If the signal is too strong the attenuation should be increased. As harmonics could be created inside the tinySA it is advised to verify this is not the case by changing the attenuation and observe if there is no impact on the level of the harmonics. Remember the delta levels of the various harmonics and increase the attenuation with 5 or 10 dB. In high mode apply extra external attenuation. After this increase of attenuation the noise floor should go up but the fundamental and all the harmonics should stay on the same level. If the harmonics go down they where, at least partially, generated inside the tinySA. If this happens increase attenuation till you see no more change and use this level of attenuation as the starting level for the measurement.

As harmonics are at multiple of the frequency of the fundamental the measurement range of the applied input mode limits the harmonic that can be measured. In low mode the second harmonic can be measured of fundamentals up to half the maximum low input frequency