[digital signal processing] discrete time signal (discrete time signal knowledge points | signal definition | signal classification | classification according to certainty | classification according t

One 、 Main knowledge points of discrete-time signals

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Discrete time signals Basic signal sequence yes Periodic sequence ;

Discrete time signals Of Time domain analysis :

• LTI ( Linear and Time-invariant System ) Linear systems are invariant
• Discrete time systems Input And Output Relationship
• from Time domain angle Judge Causal stability
• Constant coefficient difference equation

Discrete time signals Of Correlation function :

• Correlation function Definition
• Correlation function And linear convolution Relationship
• Correlation function application

Two 、 Signal profile

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1、 Signal definition

The signal yes The carrier of information , from Mathematical angle see , Can be regarded as With A number of Physical parameters change and change Of function ;

The signal $f(t)$ , The argument is $t$ It can be Time , distance , temperature , weight And so on ;

stay Discrete time signal system in , The independent variable of the signal generally defaults to Time $t$ ;

2、 Signal classification

(1) Classify according to whether the signal value is determined ( Deterministic signals | Random signals )

① Deterministic signals : The value of the signal at a certain time is certain ; Such as : Sine wave , Sawtooth wave The signal ;

② Random signals : The signal value is random ; Such as : Noise signal ;

(2) Classify according to signal periodicity ( Periodic signal | Aperiodic signal )

Periodic signal : The signal has a periodic pattern , Such as : Sine wave signal ;

Aperiodic signal : The signal has no periodic regularity , Such as : Noise signal ;

(3) Classify according to signal discreteness ( Discrete time signals | Continuous time signal )

Discrete time signals : digital signal ;

Continuous time signal : analog signal ;

(4) Classify according to signal energy ( Energy signal | Power signal )

Energy definition of signal : The energy on the whole axis is squared first , And then integral ;

Signal power definition : In one signal cycle , Perform integral summation operation ;

If energy Less than infinite , Then the signal yes Energy signal ; A signal in a finite interval is called an energy signal ;

If power Less than infinity , Then the signal yes Power signal ; Periodic signal , Random signals Power signal ;