Proving System is Time Invariant (T.I.) or Not

In summary, the conversation is about proving whether a system is time-invariant (TI) or not. The input signal is denoted as x(n), the output signal as y(n), and the system as h(n). The attempt at a solution involves inputting x(n-n0) into the system and getting x(n-n0)*h(n) as the output. However, it is pointed out that the output should actually be x(n-n0)*h(n-n0) to determine if the system is TI. The conversation also mentions the need for the transfer function or impulse response function to accurately determine if the system is TI or not.
  • #1
SpaceDomain
58
0

Homework Statement


Prove that the system is either T.I. or is not T.I.


Homework Equations


y(n) = x(n)*h(n)

x(n) is the input signal
y(n) is the output signal
h(n) is the system


The Attempt at a Solution


Inputing x(n-n0) into the system I get out:
as the output x(n-n0)*h(n)

Since y(n-n0) = x(n-n0)*h(n-n0) != x(n-n0)*h(n) the system is not T.I.

I think I am doing this wrong.
 
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  • #2
SpaceDomain said:
Inputing x(n-n0) into the system I get out:
as the output x(n-n0)*h(n)
how can you get this output for x(n-n0) input ?
 
  • #3
reddvoid said:
how can you get this output for x(n-n0) input ?

So should it be that an input of x(n-n0) results in x(n-n0)*h(n-n0)?
 
  • #4
no,
you are telling
x(n) is input of the system
y(n) is out put of the system
h(n) is its transfer function

in-order to check whether the system is TV or TIV we need the relation between input and output.
for example if you tell y(t) output =sin times input x(t)
then we can check whether its TV or TIV
or we need the impulse response function h(t) to decide whether it is TV or TIV

you have not given anything
for every system y(t) is equal to x(t)*h(t)
but their response depends on the function h(t) which is different for different systems

P.S.
I hope you understood
 
  • #5


Your approach is correct, but your conclusion is not entirely accurate. Let's break it down step by step.

First, let's define what it means for a system to be time-invariant (T.I.). A system is T.I. if a time shift in the input signal results in the same time shift in the output signal. Mathematically, this can be represented as:

x(n) --> h(n) --> y(n) (original input x(n) results in output y(n))
x(n-n0) --> h(n) --> y(n-n0) (input shifted by n0 results in output shifted by n0)

Now, let's apply this to your solution. You correctly input x(n-n0) into the system and get the output x(n-n0)*h(n). However, your conclusion that y(n-n0) = x(n-n0)*h(n-n0) is not entirely accurate.

If the system is T.I., then the output should be x(n-n0)*h(n-n0), but if the system is not T.I., then the output will not be the same. Therefore, your conclusion should be that the system is not T.I. because the output does not match the expected output x(n-n0)*h(n-n0).

In summary, your approach is correct, but your conclusion should state that the system is not T.I. because the output does not match the expected output when the input is shifted.
 

Related to Proving System is Time Invariant (T.I.) or Not

1. How is time invariance defined in a system?

Time invariance in a system means that the output of the system does not change when the input to the system is delayed or advanced in time. In other words, the behavior of the system remains the same regardless of when the input is applied.

2. What is the importance of proving a system is time invariant?

Proving that a system is time invariant is important because it allows us to predict the behavior of the system in the future based on its past behavior. It also enables us to use mathematical tools and techniques to analyze and design the system.

3. How can we prove that a system is time invariant?

To prove that a system is time invariant, we can use the time-shifting property. This property states that if the input to a system is delayed by a certain amount of time, the output will also be delayed by the same amount of time. By analyzing the input and output signals of the system, we can determine if this property holds true.

4. What are some common misconceptions about time invariance in systems?

One common misconception is that a system is time invariant if it has a constant output. This is not always the case, as a system can have a constant output and still not be time invariant. Another misconception is that a system is time invariant if it has a linear relationship between its input and output. While linearity is a necessary condition for time invariance, it is not sufficient on its own.

5. Can a system be both time invariant and time varying?

No, a system cannot be both time invariant and time varying. A system is either time invariant, meaning its behavior does not change with time, or it is time varying, meaning its behavior changes with time. It is not possible for a system to exhibit both behaviors simultaneously.

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