robin

just been looking at the [freqshift~] object...could this be implemented as a patch (as in how to cancelling out/filtering the sidebands)?

before anyone says it, i am aware the existence of the object negates any need to do this, it's more a synthesis/dsp knowledge-quest

ssb-am

On 15 Dec 2008, at 22:28, robin foster wrote:

> just been looking at the [freqshift~] object...could this be 

> implemented as a patch (as in how to cancelling out/filtering the 

yes, this can (and was) implemented as a patch.

i'd say it consists of two parts: a 90 degree shift and a complex 

the hilbert~ object does the shift. but since this is the most (and 

most interesting) part of the work, you'd have to investigate in this 

check out the hilbert~ help file for a freqshift example.

why this works for canceling the upper or lower sidebands is last but 

not least a 'simple' trigonometry question.

the hilbert~ transformer produces two signals that are 90 degree 

apart and the complex ringmod adds another 90 degree shift between 

the upper and the lower sidebands. if you add or subtract the two 

modulations, one of the sideband parts will cancel out.

the 90 degree shift can be achieved by chaining a set of allpass 

but finding the right coeffs is something you'd probably not do 

the difficult part here is to achieve a constant shift for a wide 

long before the freqshift~ and the hilbert~ object, there existed a 

don't know who did it, maybe miller puckette himself.

On 15 Dec 2008, at 22:28, robin foster wrote:
>
> Hi,
>
> just been looking at the [freqshift~] object...could this be  
> implemented as a patch (as in how to cancelling out/filtering the  
> sidebands)?

yes, this can (and was) implemented as a patch.
i'd say it consists of two parts: a 90 degree shift and a complex  
modulation.
the hilbert~ object does the shift. but since this is the most (and  
most interesting) part of the work, you'd have to investigate in this  
direction.
check out the hilbert~ help file for a freqshift example.

why this works for canceling the upper or lower sidebands is last but  
not least a 'simple' trigonometry question.
the hilbert~ transformer produces two signals that are 90 degree  
apart and the complex ringmod adds another 90 degree shift between  
the upper and the lower sidebands. if you add or subtract the two  
modulations, one of the sideband parts will cancel out.

the 90 degree shift can be achieved by chaining a set of allpass  
filters.
but finding the right coeffs is something you'd probably not do  
yourself.
the difficult part here is to achieve a constant shift for a wide  
frequency range.
long before the freqshift~ and the hilbert~ object, there existed a  
patch from the old ircam days.
don't know who did it, maybe miller puckette himself.

thanks, there's loads for me to investigate further here, volker.

SSB-AM