Signals and Systems Overview

Signals

• • Signals can be continuous-time or discrete-time.

  • Continuous-time signals are defined for all time values.

  • Discrete-time signals are defined only at specific time points.

  • Digital signals have discrete values; analog signals have continuous values.

  • A digital image represents a discrete-time signal.

  can be continuous-time or discrete-time

• Continuous-time signals are defined for all values of time

• Discrete-time signals are defined only at discrete points in time

• Digital signals have discrete values

• Analog signals have continuous values

• A digital image is a discrete-time signal, even if the independent variables are not time

• Examples of continuous-time signals include: voltage, current, electrocardiograms, speech, music, position, velocity, acceleration, forces, torques, and flow rates

• Examples of discrete-time signals include: digital video, digital photographs, and digital audio data

• Discrete-time signals can correspond to a sampled version of a continuous-time signal

• The Dow Jones Industrial Average stock market index is an example of a discrete-time signal because it is only defined on daily intervals

• The nth element of a sequence x is denoted as either x(n) or xn

Systems

• A system processes one or more input signals in order to produce one or more output signals
• A system can be classified based on the number of inputs and outputs
• A system can be classified based on the types of signals it interacts with
• A system that deals with continuous-time signals is called a continuous-time system
• A system that deals with discrete-time signals is called a discrete-time system
• A system that handles both continuous- and discrete-time signals is called a hybrid system
• A system that deals with digital signals is referred to as digital, while systems that handle analog signals are referred to as analog
• A one-dimensional system interacts with one-dimensional signals
• A multi-dimensional system handles multi-dimensional signals
• Systems can manipulate signals in many different ways and serve many useful purposes
• Systems can extract information from their input signals, such as speaker identification or voice recognition
• Systems can analyze electrocardiogram signals to detect heart abnormalities
• Systems can amplify signals and reduce noise

Basic Systems

• An RC network has a source voltage vs as input and a capacitor voltage vc as output
• Signal-processing systems can use a discrete-time system (like a digital computer) to process a continuous-time signal

Communications Systems

• Elements of a communication system include: message signal, transmitted signal, received signal, transmitter, channel, receiver
• The system can process the received signal to extract the message signal

Feedback Systems

• A feedback control system uses a sensor to measure an output signal
• The feedback system uses a controller to compare the measured output to a desired input signal
• The controller generates an error signal
• The controller uses the error signal to adjust the plant (the system being controlled), to reduce the error

This quiz covers the fundamental concepts of signals and systems, focusing on the differences between continuous-time and discrete-time signals. You'll explore examples of both analog and digital signals, as well as the characteristics of various systems that process these signals. Test your understanding of key concepts in this foundational topic.