Does ADS has a easy way to simulate the CLASS-G audio amp THD?

[tony_lth]

I have a Class-G audio amp, ad it has THD issue, so I want to simulate it in ADS.
It's really difficult to simulate THD in ADS?
Does any one has a example?
Audio signal: 100Hz~20KHz, Class-G clock 1.6MHz, load is 16 ohm + 33uH.
The link is audio input-->Class G amp-->load

I know use FFT can do it, but I am not familiar with MATLAB. I guess ADS can also process it.
Any comments is welcome.

 

[BigBoss]

You can of course use ADS for audio amplifier simulations.
THD is the sum of harmonics' amplitudes.( Look at THD formulae)So, if you do a HB simulation, you'll find the amplitudes of the harmonics and ADS won't know how type of circuit you simulate.There is no practical difference to simulate a Microwave amplifier and Audio amplifier from aspect of simulation.There is maybe a measurement expression that computes THD directly,I don't know but you can create an expression if there isn't any.
ADS is essentially general purpose simulator.You can simulate even DC or Lightwave..almost same..

 

[RealAEL]

As BigBoss says there is no reason that ADS couldn't be used to perform this type of analysis as long as a suitable simulator was used. Harmonic Balance could certainly do it as it is able to generate the harmonic output tones that would be generated from a single pure sinusoidal tone at the input of the amplifier. The frequency of that input tone could be anything from 1 Hz to a very large number of Hz. Linear simulation cannot do it as it is single tone in for the same tone out.

The main difference though is that any simulation like this treats any signal spectrum, the audio spectrum in this case, as a series of discrete harmonically related tones and not a continuous spectrum.

Given that THD is the ratio of all higher harmonic output tones to the first harmonic tone the math is quite easy:

THD = (P2nd + P3rd + P4th + ... + PNth)/P1st

as long as N is suitably large. This simplifies to:

THD = (Ptotal - P1st)/P1st

So two power measurement, some simple math and it is done. In the case of the fundimental tone being 1 kHz and the simulation using up to the 20th harmonics, for 20 kHz, something like this would work:

 

[tony_lth]

Hi, Bigboss and RealAEL,

Thank you very much.

 

[tony_lth]

Hi, Bigboss and RealAEL,

Could you do me a favor to answer the questions in this post?
https://www.edaboard.com/threads/286509/

Many thanks.