MATLAB SIGNAL PROCESSING BLOCKSET 7 Guide de l'utilisateur télécharger pdf (Page 335)

100

101

FFT

5-178

in Equation 5-2. This parameter has two settings, each

with its advantages and disadvantages, as described in the following table.

Optimizing the Table of Trigonometric Values

When you set the Twiddle factor computation parameter to Table lookup,

you need to set the

Optimize table for parameter. This parameter optimizes

j– 2π m 1–()k 1–()M⁄

Twiddle factor computation

Parameter Setting

Sine and Cosine Computation

Method

Effect on Block Performance

Table lookup The block computes and stores

the trigonometric values before

the simulation starts, and

retrieves them during the

simulation. When you generate

code from the block, the

processor running the generated

code stores the trigonometric

values computed by the block,

and retrieves the values during

code execution.

The block usually runs much

more quickly, but requires

extra memory for storing the

precomputed trigonometric

values. You can optimize the

table for memory

consumption or speed, as

described in “Optimizing the

Table of Trigonometric

Values” below.

Trigonometric fcn The block computes sine and

cosine values during the

simulation. When you generate

code from the block, the

processor running the generated

code computes the sine and

cosine values while the code

runs.

The block usually runs more

slowly, but does not need

extra data memory. For code

generation, the block

requires a support library to

emulate the trigonometric

functions, increasing the size

of the generated code.

1 2 ... 330 331 332 333 334 335 336 337 338 339 340 ... 737 738

Commentaires sur ces manuels

Pas de commentaire

MATLAB SIGNAL PROCESSING BLOCKSET 7 Guide de l'utilisateur Page 335

Commentaires sur ces manuels

Produits connexes et manuels pour Logiciel MATLAB SIGNAL PROCESSING BLOCKSET 7