convert sum of two sines to square wave?

Paul Russell wrote:

> Funky wrote:
> 
>>
>> But how do I use this to get the same output as multiplying the sum by
>> infinity and clipping?
>> Yes, I'm being stupid here.
>> Funky
>>
> 
> The output only has 2 states: +1 and -1.
> 
> (Actually there is probably at least one pathological condition where 
> the output will always be zero, but I leave this kind of detail as an 
> exercise for the reader.)
> 
> Paul

The state switches when the magnitudes of one becomes larger than the 
other and they have opposite signs. How is that time determined?

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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Jerry Avins wrote:
> 
> The state switches when the magnitudes of one becomes larger than the 
> other and they have opposite signs. How is that time determined?
> 

Good point - I /thought/ I had this covered but maybe I need to try a 
simple implementation and see if it actually works before shooting my 
mouth off further.

Paul

Jerry Avins wrote:
> 
> 
> The state switches when the magnitudes of one becomes larger than the 
> other and they have opposite signs. How is that time determined?
> 

OK - I missed out a step - sorry.

We need to use the identity:

sin(A) + sin(B) = 2 * sin((A + B) / 2) * cos((A - B) / 2)

All we care about is the sign of the result, so we use the periods and 
initial phases of the (A + B) / 2 and (A - B) / 2 terms from which we 
can predict their signs based on zero crossings. The sign of the output 
is then just the product of these two individual signs.

The pseudo code I posted earlier is still more or less correct, but the 
periods and phases come from the identity above, not the original sine 
wave periods and phases.

Paul

"Paul Russell" <prussell@sonic.net> wrote in message
news:cowYb.1882$_3.30739@typhoon.sonic.net...
> Funky wrote:
>
> >
> > Yes. I still think you need to exploit the trig identity that sum of
sines
> > equals product of sin and cos, unless you're thinking of another way.
>
> I don't think so. Given the intial phases and the periods all you need
> is a simple state machine. (As others have noted, it gets more
> complicated if the amplitudes of the two sine waves are different, but
> apparently that is not the case in this instance.)
>
> Paul

He he he. Don't we sometimes wish we could turn back the clock;)
Funky

Funky wrote:
> 
> 
> He he he. Don't we sometimes wish we could turn back the clock;)
> Funky
> 
> 

Nope - read the whole thread.

Paul