A project was made to demonstrate the impact and functionality of the IP2H parameter of the MWO NL_AMP model.
You will see in the schematic that IP2H is set to 40 dBm. In the graph 'pout', the power at the fundamental and the power at the 2nd harmonic are being plotted. The markers are there to get the equation for both curves in the linear region. For the fundamental pout = pin +8. For the 2nd harmonic, pout = 2*pin-24. The intercept point will be where pout and pin are equal for both curves, or in other words, where the two linear lines cross. Solving both equations for pin and pout results in an intercept points pin=32 and pout=40, which was set in the model.
Hopefully this gives some meaning to what IP2H (intercept point 2nd harmonic) really means. To visualize this, tune on IP2H and watch the 2nd harmonic power curve move in the pout graph.
This project shows some basic concepts of nonlinear devices and saturation. Look at the "fundamental_2nd_and_3rd" graph. This is the same as the pout graph but now the 3rd harmonic is added. Notice that the 2nd harmonic will saturate like the fundamental but the 3rd harmonic does not. This can be explained from the waveform at the output. In the linear region, the waveform will be a pure sinusoid (assuming class A operation). However, when the amplifier saturates, the waveform is clipping. If driven hard enough, the sine wave will approach a square wave which means that odd harmonics are being added to the spectrum. This is why the third harmonic rises as the amplifier goes into compression but not the 2nd.