Derivative

Overview

Discrete-time derivative

Discussion

Computes the derivative of a discrete-time signal. The derivative is defined as:

\(y[n] = K/T * (x[n] - x[n-1])\) where T is the sample period and K is the optional gain parameter. The module sets the default starting value to x[-1] = 0.

The discrete derivative is similar to the continuous time derivative. For example, if the input is a sine wave at 1 kHz, then the output will be a cosine at 1 kHz scaled by 2pi1000.

The hidden internal array .lastValue stores the previous value x[n-1] between blocks. The length of the array is set by the prebuild function to the number of channels.

Module Pack

Advanced

ClassID

classID = 1259

Type Definition

typedef struct _ModuleDerivative
{
ModuleInstanceDescriptor instance;            // Common Audio Weaver module instance structure
FLOAT32 gain;                                 // Additional gain.
FLOAT32* lastValue;                           // Previous value x[n-1].
} ModuleDerivativeClass;

Variables

Properties

Name	Type	Usage	isHidden	Default Value	Range	Units
gain	float	parameter	0	1	-10:10	linear
lastValue	float*	state	1	[1 x 1]	Unrestricted

Pins

Input Pins


Name	in
Description	Input signal
Data type	float
Channel range	Unrestricted
Block size range	Unrestricted
Sample rate range	Unrestricted
Complex support	Real

Output Pins


Name	out
Description	Output signal
Data Type	float

Matlab Usage

File Name: derivative_module.m 
 M=derivative_module(NAME)  
 This module computes the derivative of the input signal.  Mathematically, 
 this is: 
   y[n] = 1/dt * (x[n] - x[n-1]) 
 where dt is the time step, dt = 1/SR.  The module has a multichannel 
 input and computes the derivative per channel.  Arguments: 
    NAME - name of the module.