[sdiy] Ring Mod (was Re: Hadamard Transform Network)

[Tony K]

Haha, bet the boys had perfect attendance in that class! 

Saturday tutoring at her place ? nudge nudge, wink wink , say no more.

TK

> On May 16, 2017, at 8:48 PM, Tim Ressel <timr at circuitabbey.com> wrote:
> 
> That explains it. There was a girl in my high school trig class that liked tight sweaters...
> 
> --tr
> 
> 
> 
> On 5/16/2017 9:13 AM, Donald Tillman wrote:
>>> On May 16, 2017, at 8:40 AM, Tim Ressel <timr at circuitabbey.com> wrote:
>>> 
>>> But you bring up an interesting point: 4QMs multiply, but they produce x+y, x-y tones. Anyone got the math on that?
>> High school trigonometry.
>> 
>> Trig identity:
>>    cos(a+b) = cos(a)cos(b) - sin(a)sin(b)
>> 
>> Another trig identity, derivable from the first:
>>    cos(a-b) = cos(a)cos(b) + sin(a)sin(b)
>> 
>> Add'm:
>>    cos(a+b) + cos(a-b) = 2 cos(a)cos(b)
>> 
>> Your multiplication operation is on the right, your sum and difference tones are on the left.
>> 
>>   -- Don
>> 
>> --
>> Don Tillman
>> Palo Alto, California
>> don at till.com
>> http://www.till.com
>> 
>> 
>> 
>> 
>> 
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> 
> -- 
> --Tim Ressel
> Circuit Abbey
> timr at circuitabbey.com
> 
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