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Class F PA questions

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senmeis

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Hi,

This description is taken from the first attached presentation slide about class F PA: “Typical topologies attempt to present an open load to harmonics to reduce distortion.” As far as I understand “typical topologies” refer to conventional PAs such as A, B, AB or C. Is it correct?

From the second slide this can be read: “high Z for odd harmonics, low Z for even harmonics”
This statement about the odd harmonics is different to the first slide. Do I get a wrong understanding?

Senmeis
Class_F_PA_1.jpgClass_F_PA_2.jpg
 

Class F is all about using pulses to "re-create" the desired waveform after the necessary filtering, as the mosfets are either hard on or hard off with resonant haversine currents the efficiency can be really high - the freq needs to be high too for fidelity reasons ...
 

As far as I understand “high Z for odd harmonics” = block odd harmonics. Is it correct?

Senmeis
 

Only "trap" filters can selectively filter out particular even or odd harmonics, there is no low pass ( or high pass) filter that will only do odd harmonics, unless it has branches tuned to those harmonics ...
 

But what about this sentence “high Z for odd harmonics, low Z for even harmonics”? It seems odd and even harmonics are handled differently.

Senmeis
 

Our early arithmetic lessons told us 2 goes into 4 evenly, meaning no fraction was in the result. Perhaps the authors mean 'even' harmonics in the same way. Namely as integer multiples (2, 3,4,5, etc.), because an exact number of cycles fits within one cycle of the fundamental frequency.

- - - Updated - - -

Whereas a non-integer multiple is regarded as an 'odd' harmonic? It isn't the clearest use of the English language but sometimes we have to make accommodations.
 

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