National Instruments Car Stereo System 320571-01 用户手册

Performs IIR filtering on the
X input array  and reports the
result in Y.  It uses the arrays
a and b of sizes sza and szb
respectively in implementing
the linear difference equation
that describes IIR filtering:

         k = sza - 1          k = szb-1
 y[i] = 

∑

 a(k) * x(i-k)   -  

∑

 b(k) * y(i-k)                    i = 0,1 ..... ,n-1

         k = 0                     k = 1

where:

a is the array of forward coefficients describing an IIR filter (obtained from DSP Butterworth Coefficients
VI for example)
b is the array of feedback coefficients describing an IIR filter (obtained from the same filter design VI)

(0) = 1.0

 in the above equation.

This VI may be called in a loop to perform filtering on data frames that are part of the same data stream.

At time i = 0, the initial conditions on X (for example, X(1-sza

)

 through X(-1)) are obtained from the array

Initial Conditions on input.  At exit (the end of the VI execution), this array holds the final conditions on
X that could be used as the initial conditions for the next DSP IIR Filter VI call if you were to call it in a
loop.

At time i = 0, the initial conditions on Y (for example, Y(1-szb) through Y(-1)) are obtained from the array
Initial Conditions on output.  At exit (the end of the VI execution), this array holds the final conditions on
Y that could be used as the initial conditions for the next DSP IIR Filter VI call if you were to call it in a
loop.

X is a DSP Handle Cluster that indicates the memory buffer on the DSP board that contains the input
signal array.

Y in is a DSP Handle Cluster that indicates the memory buffer on the DSP board that will contain the
output array of filtered data.

Initial Conditions on input is a DSP Handle Cluster that indicates the memory buffer on the DSP board
that contains the initial conditions on input at time zero.

Initial Conditions on output is a DSP Handle Cluster that indicates the memory buffer on the DSP
board that contains the initial conditions on output at time zero.

Forward Coefficients is a DSP Handle Cluster that indicates the memory buffer on the DSP board that
contains the forward coefficients of the IIR filter.

Feedback Coefficients is a DSP Handle Cluster that indicates the memory buffer on the DSP board that
contains the feedback coefficients of the IIR filter.