User`s guide

Variable Fractional Delay
5-491
5Variable Fractional Delay
Purpose Delay an input by a time-varying fractional number of sample periods.
Library Signal Operations
Description The Variable Fractional Delay block delays each channel of the M
i
-by-N input
matrix, u, by a variable (possibly noninteger) number of sample intervals.
The block computes the value for each channel of the output based on the
stored samples in memory most closely indexed by the
Delay input, v, and the
interpolation method specified by the
Mode parameter. In Linear
Interpolation
mode, the block stores the D+1 most recent samples received at
the
In port for each channel, where D is the Maximum delay. In FIR
Interpolation
mode, the block stores the D+P+1 most recent samples received
at the
In port for each channel, where P is the Interpolation filter
half-length
.
See the Variable Integer Delay block for further discussion of how input
samples are stored in the block’s memory. The Variable Fractional Delay block
differs only in the way that these stored sample are accessed; a fractional delay
requires the computation of a value by interpolation from the nearby samples
in memory.
Sample-Based Operation
When the input is sample-based, the block treats each of the M
i
∗N matrix
elements as an independent channel. The input to the
Delay port, v, is an
M
i
-by-N matrix of floating-point values in the range 0 ≤ v ≤ D that specifies the
number of sample intervals to delay each channel of the input.
A 1-D vector input is treated as an M
i
-by-1 matrix, and the output is 1-D.
The
Initial conditions parameter specifies the values in the block’s memory at
the start of the simulation in the same manner as for the Variable Integer
Delay block. See the section on sample-based initial conditions there for
complete information.
Frame-Based Operation
When the input is frame-based, the block treats each of the N input columns as
a frame containing M
i
sequential time samples from an independent channel.