Selecting an Impulse Response Length (System Identification Toolkit)

Theoretically, the length of the impulse response might be infinite. For some systems, the impulse response quickly reaches zero, and the number of nonzero points is finite. For other systems, the impulse response never reaches zero. Realistically, you can obtain only the first N points of the impulse response due to limited signal length and limited memory size. Therefore, the SI Estimate Impulse Response VI has inputs to specify how many points of the impulse response to observe. With the least squares method, you must ensure the sum of num of points (t<0) and num of points (t>=0) is no larger than the signal length. With the correlation analysis method, you can set num of points to be as large as the signal length.