Following to designing a fixed-point multirate filter, fixed-point quantization occurs for the coefficients and for the intermediate operands and results. By using the DFD FXP MRate Modeling VI, only the quantizers for the input and output signals require configuration.

The DFD FXP MRate Modeling VI automatically configures the quantizers for intermediate operands.

Setting the Input Word Length, Input Integer Word Length, and Output Word Length

Use the DFD FXP MRate Modeling VI to specify input word length, input integer word length, and output word length. These word lengths determine the number of bits to use in representing the input and output signals. The DFD FXP MRate Modeling VI automatically configures the integer word length of the output signal.

Setting the Rounding Mode

Fixed-point numbers have limited word lengths, so the available dynamic range of fixed-point numbers is lower than the range available with double-precision and floating-point numbers. Therefore, fixed-point numbers can approximate floating-point numbers only. In the LabVIEW Digital Filter Design Toolkit, the Multirate Fixed-Point Tools VIs use up to 48 bits for internal operations. Use the output rounding mode input of the DFD FXP MRate Modeling VI to configure the output quantizer.