User`s guide

FIR Decimation

5-196

samples K+1, 2K+1, and so on. See the example below for an illustration of this

case.

See “Excess Algorithmic Delay (Tasking Latency)” on page 3-91 and “The

Simulation Parameters Dialog Box” in the Simulink documentation for more

information about block rates and Simulink’s tasking modes.

Examples Example 1

Construct the frame-based model shown below.

Adjust the block parameters as follows:

•Configure the Signal From Workspace block to generate a two-channel

signal with frame size of 4 and sample period of 0.25. This represents an

output frame period of 1 (0.25

∗4). The first channel should contain the

positive ramp signal 1, 2, ..., 100, and the second channel should contain the

negative ramp signal -1, -2, ..., -100.

Signal = [(1:100)' (-1:-1:-100)']

- Sample time = 0.25

- Samples per frame = 4

•Configure the FIR Decimation block to decimate the two-channel input by

decreasing the output frame rate by a factor of 2 relative to the input frame

rate. Use a third-order filter with normalized cutoff frequency, f

, of 0.25.

(Note that f

satisfies f

≤ 1/K.)

FIR filter coefficients = fir1(3,0.25)

- Downsample factor = 2

- Framing = Maintain input frame size