Signal Classification - GATE Study Material 
                                  in PDF 
           
          In the previous articles, we discussed Time Signals & Signal Transformation as well 
          as some Standard Time Signals. In these free GATE 2018 Notes, we will discuss some 
          Signal Classification based on Properties. These study material are useful for 
          GATE EC and GATE EE as well as other exams like BARC, BSNL, DRDO, ISRO, 
          IES etc. These notes may also be downloaded in PDF so that your exam 
          preparation is made easy and you ace your exam.  
          You are strongly advised to go through previous articles before starting off with this 
          module.  
          Recommended Reading – 
                            Laplace Transforms 
                   Limits, Continuity & Differentiability 
                           Mean Value Theorems 
                               Differentiation 
                           Partial Differentiation 
                            Maxima and Minima 
               Methods of Integration & Standard Integrals 
                              Vector Calculus 
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                            Vector Integration                  
                  Time Signals & Signal Transformation 
                          Standard Time Signals 
          
         Signals are basically classified in the following categories:  
         1. Continuous & Discrete Time Signals  
         2. Deterministic & Non-Deterministic (Random) Signals  
         3. Left-Sided & Right-Sided Signals  
         4. Causal, Anti–Causal & Non-Causal Signals  
         5. Even & Odd Signals  
         6. Periodic & Non-Periodic Signals  
         7. Energy & Power Signal  
          
          
         Continuous & Discrete Time Signals   
         The variable of time is continuous in a continuous time signal. A speech signal as a 
         function of time is a continuous-time signal. 
                                                 
                               Continuous Time Signal 
         The variable of time is discrete. The weekly Dow Jones stock market index is an 
         example of discrete-time signal. 
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                                 Discrete Time Signal 
          Deterministic & Non-Deterministic Signals   
          Signals which can be completely represented graphically or mathematically are known 
          as deterministic signals. This means that the nature and value of the signal can be 
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          predicted at any point of time. For instance, x(t) = sin t  and x(t) = t   
          Signals which take random value i.e. signals whose occurrence is random in nature 
          are known as non-deterministic signals. These signals are quite irregular and we 
          cannot represent these signals mathematically.  
          Example: Noise generated in a communication channel and thermal noise generated 
          in an electrical circuit.  
           
          Left-Sided & Right-Sided Signal   
          Signal extending form -∞ to some finite point of time (let’s say t ) is known as left-
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          sided signal. Some of the examples of left sided signals are shown below. 
                                                   
                                 Left −Sided Signal (1) 
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                                 Left −Sided Signal (2) 
                                                     
                                 Left −Sided Signal (3) 
                                       
          Signals extending from any finite point of time t  to +∞ are known as right-sided 
                                           0
          signals.  
               non zero  ;to < t < ∞
          ( )
          x t = {               
               o                ;  otherwise
          Here are some examples: 
                                                   
                                Right−Sided Signal (1) 
                                       
                                                  
                                Right−Sided Signal (2) 
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