[sdiy] Walsh bank, was: Re: [sdiy] Micro as a Linear to Exponential converter?

[Aaron Lanterman]

On Aug 15, 2009, at 7:10 AM, Antti Huovilainen wrote:

> On Sat, 15 Aug 2009, Tom Wiltshire wrote:
>
>> Analogously, how many sine waves do you need to make an arbitrary  
>> waveform with standard fourier analysis? I've used 64 in my  
>> oscillator design, as a compromise between quality and feasibility.  
>> I'd say you need at least that many for Walsh synthesis, and  
>> probably more, since you're adding functions with sharp edges and  
>> that will make the results more crunchy. Double or quadruple this  
>> would be better.
>
> You can lower the number of required functions by following the  
> oscillator with a tracking lowpass filter. The situation is then  
> analogous to normal DA converter.

Good point.

Taking a step back, Walsh functions form another basis for  
representing signals, just like short time-shifted pulses form a basis  
for representing signals in a usual sampling scheme.

- Aaron