Lattice ARMA Structures (Digital Filter Design Toolkit)
June 2008
NI Part Number:
371988B-01
»View Product Info
For an infinite impulse response (IIR) filter, you can implement one of the following section types of lattice autoregressive-moving average (ARMA) filter structures:
- Basic section type
- One multiplier section type
- Normalized section type
The following figure represents the basic section type of a lattice ARMA filter structure. Refer to the Understanding Filter Structure Graphs topic for information that helps you read and understand a filter structure graph.
The total number of the lattice reflection coefficients k is M, where M is the filter order. The total number of the lattice ladder coefficients v is M+1. The total number of multipliers is 3M+1.
The following figure represents the one multiplier section type of a lattice ARMA filter structure.
The total number of coefficients k and v is 2M+1, which is the same as in the basic section type. However, the total number of multipliers is only 2M+1, which is less than the number of multipliers in the basic section type. Therefore, the one multiplier section type of a lattice ARMA structure involves fewer multipliers than other section types. Fewer multipliers require less hardware resources.
The following figure represents the normalized section type of a lattice ARMA filter structure.
You can derive k' from k in the normalized section type by using the formula 
.
One advantage of the normalized section type structure is that this structure automatically scales the internal signals in each lattice section. Unfortunately, scaling the internal signals increases the implementation complexity.