National Instruments Car Stereo System 320571-01 用户手册

Generates an array containing a sinc
pattern.  If the Sinc Pattern is represented
by the sequence Y, then the pattern is
generated according to the following
formula:

y

i 

 =  a sinc(i

∆

 t - d) ,

for  i = 0, 1, 2, …, n-1 ,

where sinc(x)  =  

sin(

π

x)

π

x

 ,

a is the amplitude,

∆

t is the sampling interval delta t,

d is the delay, and
n is the number of elements in Sinc Pattern.

The main lobe of the sinc function, sinc(x), is the part of the sinc curve bounded by the region -1 

≤

 x 

≤

 1.

When |x| = 1, the sinc(x) = 0.0, and the peak value of the sinc function occurs when x = 0.  You can show using
l'Hôpital's Rule that sinc(0) = 1 and that it is also its peak value.  Thus, the main lobe is the region of the sinc curve
encompassed by the first set of zeros to the left and the right of its peak value.

amplitude defaults to 1.0.

delay shifts the peak value within the Sinc Pattern as the VI generates the pattern.  This condition is
determined from the preceding formula and occurs when i

∆

t  =  d .  delay defaults to 0.0.

delta t is the sampling interval.  It is a floating-point number inversely proportional to the width of the
main sinc lobe.  That is, the smaller the sampling interval, the wider the main lobe, and the larger the
sampling interval, the smaller the main lobe.  Notice that when delta t is 1 and d is an integer value, the
VI sets Sinc Pattern to zero except at the point where i = d, at which point the value is equal to
amplitude.  The recommended range of values for the sampling interval is 0 < delta t 

≤

 1 .  delta t must

be greater than 0.0.  If delta t is less than or equal to zero, the VI returns an error.  delta t defaults to 1.0.

Sinc Pattern in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will
contain the output sinc pattern.

Sinc Pattern out is a DSP Handle Cluster that is identical to the Sinc Pattern in, but with the generated
pattern already stored in the memory buffer on the DSP board.  The largest sinc pattern that can be
generated depends upon the amount of memory on your DSP board.

error in (no error) contains the error information from a previous VI.  If an error occurs, it is passed out
error out and no other calls are made.

error out contains the error information for this call.