[odin-devel] sinusoidal gradients

[Lazar F. <laz...@gm...>]

Hello everybody,

I can not seem to be able to make sinusoidal-shaped gradients.
I was thinking about using trapesoidal gradients and set the rapmtype
to "half_sinusoidal".
Then I made a calculation for the integral, max gradient and
rampduration so that the
shape of the gradient will be a sinus (with horizontal part of the
trapezoid equal to zero, only ramps).
Instead, I seem to observe that some horizontal part of the gradient
is kept and the gradient amplitude
is reduced to produce correct gradient intergral. I know that if I set
the total length of the gradient to
a very short one, I will exceed the allowed gradient slewrate and this
would happen. But I have done
checking and the slewrate is 1/3 of the maximum. This indicates that
there is some sort of hard limit
on the minimum duration of the horizontal part of the gradient which
is substantial. I could not find where
it was set in the code.

Am I trying to do something illegal? maybe it is a design feature
based on some limits which I do not understand,
but then, how to make sinusoidal gradients?

Thanks a lot for your help

Lazar