Hi
Could you please help me with **broken link removed**? The Q1 is given below. Thank you very much and please don't forget I'm new to this stuff.
Q1:
A causal system is one which responds only during or after an input signal is applied. Or, as the **broken link removed**, "Any system for which the zero-state response occurs only during or after the time in which it is excited is called a causal system".
But if I were to define it then I would say, a causal system is one whose output, y(t), does not depend on the future value of an input signal, x(t), or its some future output value. A causal system should always use present or previous value of an input signal and/or some previous output value. For instance, this equation is for a causal system, y(t)=x(t)+x(t-1). And this one is for a non-causal system, y(t)=x(t)+x(t+1)+y(t+1); you can see that the x(t+1) and y(t+1) expect future values. In other words, if you want to know the output's value at t=3 then you must first know its input signal's value at t=3 and its output value t=3. Such a system cannot implemented in real-time environment.
Regards
PG