1. Define Signal. What are types of signals?

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A signal is defined as any physical quantity that varies with:
→ Time
→ Space or
→ any other independent variable
Mathematically, a signal is a function of one or more independent variables. Types of signals- Analog and Digital Signals

2.What is a signal processing system and give its types.

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A signal processing system is defined as a device that performs an operation on a signal.
Types: → Analog Signal Processing System (e.g.- Voice Amplifier) → Digital Signal Processing System (e.g. - DSP chip)

3.What are Discrete Time Signals? Name the basic elementary DTS.

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The signals, which are defined at discrete times are known as discrete signals. Therefore, every independent variable has a distinct value. Thus, they are represented as sequences of numbers.
1. Unit Impulse Signal
2. Unit Step Signal
3. Unit Ramp Signal
4. Exponential Signal

4.What operations can be performed on DTS?

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Independent variable (Time)-
→ Time shifting
→ Time reversal (folding)
→ Time scaling
Dependent variable (Amplitude)-

→ Amplitude scaling
→ Signal addition and multiplication

5.What is a Discrete Time System? Give its Classification.

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Discrete time system is a device or algorithm that operates on a discrete time signal
- Represented as y (n) = T [x (n)]
1. Static and Dynamic systems
2. Causal and Noncausal systems
3. Linear and Nonlinear systems
4. Time variant and Time invariant systems
5. Stable and unstable systems
6. FIR and IIR systems

6.Define: i) Periodic and Non-Periodic Signal ii) Even and Odd Signal iii) Energy and Power Signal

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i) A signal is said to be periodic ,if it exhibits periodicity.i.e., X(t +T)=x(t), for all values of t. Periodic signal has the property that it is unchanged by a time shift of T.A signal that does not satisfy the above periodicity property is called an aperiodic signal.
ii) A discrete time signal is said to be even when, x[-n]=x[n]. The continuous time signal is said to be even when, x(-t)= x(t) For example,Cos(n) is an even signal. The discrete time signal is said to be odd when x[-n]= -x[n]. The continuous time signal is said to be odd when x(-t)= -x(t). Odd signals are also known as non symmetrical signals. Sine wave signal is an odd signal.
iii) An energy signal has zero average power, whereas a power signal has infinite energy

7. What do you mean by Causality?

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A system is said to be causal, if the system's response should depend on present and past inputs only and not on the future inputs. That is, causal systems are physically realizable systems. Non causal systems response depends on the future input values. Hence, non causal systems are physically unrealizable systems.

8. What do you mean by aliasing in digital signal processing? How can it be avoided?

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Aliasing refers to an effect due to which different signals become indistinguishable. It also refers to distortion in the reconstructed signal when it is reconstructed from the original continuous signal.
To avoid aliasing we can simply filter out the high frequency components of the signal by using an antialiasing filter like optical antialiasing filter.

9.What is convolution?

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Convolution is the technique of adding two signals in the time domain. This is achieved by changing the domain of signals from time domain to frequency domain using Fast Fourier Transform (FFT).