How to interpret the Coefficient Report from the FXP Digital Filter Design

Question

Hi,  I tried to design a low pass IIR filter in cascaded form II. I then pass the filter into the filter structure conversion VI and then pass the filter into the FXP conversion and get the Coefficient Report.
However, I got problem understanding the report. The index of the coefficient does not correspond to the description of the Filter structures in the Labview help:
In the labview help where they describe the filter structures, the coefficients have two indices, one for the stage, and the other for intra stage.
In contrast, the report only gives out coefficients with one indicices.
My question is: how to map the coefficients to the structure.
Attached is the digital filter structures appeared in the Labview help.
The following is the report:
            Reference Value               Quantized Value              Note
Forward Coefficients:
b[0]       +1.0105197822678145E-6       +1.0104849934577942E-6      
b[1]       +2.0210395645356291E-6       +2.0210864022374153E-6      
b[2]       +1.0105197822678145E-6       +1.0104849934577942E-6      
b[3]       +1.0105197822678145E-6       +1.0104849934577942E-6      
b[4]       +2.0210395645356291E-6       +2.0210864022374153E-6      
b[5]       +1.0105197822678145E-6       +1.0104849934577942E-6      
number of Overflows:    0
number of Underflows:   0
number of Zeros:        0
Reverse Coefficients:
a[0]       -1.9962855130669792E+0       -1.9962768554687500E+0      
a[1]       +9.9628955294911659E-1       +9.9627685546875000E-1      
a[2]       -1.9984573661467793E+0       -1.9984741210937500E+0      
a[3]       +9.9846141042409486E-1       +9.9847412109375000E-1      
number of Overflows:    0
number of Underflows:   0
number of Zeros:        0
gain       +1.0000000000000000E+0       +1.0000000000000000E+0       Floating-point
* Gain processing is on the host
Attachments:
IIRcascaded.GIF ‏7 KB

Answer 1

Hi David,
The following Developer Zone article discusses important concepts involved in utilizing the digital filter design toolsets. It specifically address the form in which the design coefficients are expressed.
I hope this helps.
Cheers,
Emilie Kopp | National Instruments