[timewizard]

"Variable duty cycle?"

So just PWM?

Also, if you needed to exceed 50%, you could have just combined two different square waves, out of phase, and you'd be there.

[nayuki]

> if you needed to exceed 50%, you could have just combined two different square waves

I don't think this is possible. A balanced square wave has no even harmonics in the frequency domain. Anytime the duty cycle is not 0%, 50%, or 100%, you will have non-zero even harmonics.

A linear combination (scaled sum or difference) of two balanced square waves will necessarily still have all even harmonics at zero, and thus cannot emulate a square wave with a duty cycle different from 50%.

[timewizard]

> Anytime the duty cycle is not 0%, 50%, or 100%, you will have non-zero even harmonics.

The article is specifically trying to achieve those harmonics. This is the initial problem.

> A linear combination (scaled sum or difference) of two balanced square waves will necessarily still have all even harmonics at zero

Yea, that's why you need the phase offset, as I mentioned.

> and thus cannot emulate a square wave with a duty cycle different from 50%.

You can /synthesize/ a square wave at any duty cycle you like. We're still doing Fourier just without the whole transform.

[iamdan]

That's true, I'm coming into the audio and signals world as a beginner so I'm still picking up the lingo but totally! For my purposes I only want to keep track of a single source for a channel so I've gone down this wave transformation path rather than composition but that also would get the job done

[dimatura]

Yeah, at least in the context of music synthesis, everyone just says PWM. (The term even being subject of a meme with a certain youtuber who seems to be fond of it ;)).