EVENTUAL ENGINEER

What is Signal? Signal is a time varying physical phenomenon which is intended to convey information. OR Signal is a function of time. OR Signal is a function of one or more independent variables, which contain some information. Example:  voice signal, video signal, signals on telephone wires etc. Note:  Noise is also a signal, but the information conveyed by noise is unwanted hence it is considered as undesirable. What is System? System is a device or combination of devices, which can operate on signals and produces corresponding response. Input to a system is called as excitation and output from it is called as response. For one or more inputs, the system can have one or more outputs. Example:  Communication System

Systems are classified into the following categories: Liner and Non-liner Systems Time Variant and Time Invariant Systems Liner Time variant and Liner Time invariant systems Static and Dynamic Systems Causal and Non-causal Systems Invertible and Non-Invertible Systems Stable and Unstable Systems Liner and Non-liner Systems A system is said to be linear when it satisfies superposition and homogenate principles. Consider two systems with inputs as x 1 (t), x 2 (t), and outputs as y 1 (t), y 2 (t) respectively. Then, according to the superposition and homogenate principles, T [a 1  x 1 (t) + a 2  x 2 (t)] = a 1  T[x 1 (t)] + a 2  T[x 2 (t)] ∴ ,  T [a 1  x 1 (t) + a 2  x 2 (t)] = a 1  y 1 (t) + a 2  y 2 (t) From the above expression, is clear that response of overall system is equal to response of individual system. Example: (t) = x 2 (t) Solution: y 1  (t) = T[x 1 (t)] = x 1 2 (t) y 2  (t) = T[x 2 (t)] =...