What is Electronic Systems?
Electronic systems is a physical connection of the electronics components and parts which is used to fulfill the electronic systems requirement.
Electronic Systems have an input and output.suppose as input sensor is connected. The sensor gives a response according to the information and uses the electrical energy and gives the output action which controls the physical device or may perform some mathematical operation on the signal.
Electronic systems transform the one signal into the another which gives you desired system response.You can say that electronic system consists of an input, a process, and an output.
Electronic systems are represented by many ways. For example, electronic systems represented in mathematically, descriptively, pictorially or schematically. Electronic systems are generally represented in schematically in block form.
The most complex electronic systems can be represented by the combination of simple blocks. Each blocks representing an individual component or complete subsystem. This blocks representation are commonly known as ” block-diagram representation”.
Block Diagram Representation of a Simple Electronic System
Electronic systems have both inputs and outputs. You can say that output is produced by the inputs. In other word input signal cause the process to change or cause the operation of the system to change. Therefore you can say that the input signal of the system is the cause of the change while the output signal is called “effect”. Because of the input signal cause effect on an output side.
Lets take an example of an audio system. The audio system has a microphone as an input device which causes sound waves to be converted into electrical signal. This electrical signal is processed by the amplifier, an amplifier amplifies the electrical signal. This electrical signal is fed to the loudspeaker which produces sound waves as an effect of being driven by the amplifiers electrical signals.
Electronic system has not only a single operation but has several operations within the same overall system. our audio system involves connection of CD, DVD player, MP3 player or radio receiver all are multiple inputs to the same amplifier.
Electronic system can not just be a collection of inputs and outputs. Even if you just want to turn on a light which requires sensors. Sensors detect the electrical signal and this signal is processed. A processed electrical signal is fed to the output device called an actuator. Actuator converts the signal into mechanical movement.
Types of Electronic System
Electronic systems operate on two types of signals.One is continuous-time(CT)signals and discrete-time(DT)signals.A continuous time signals are continuous over a period of time. Analog signals are examples of the continuous time signal.
You can say that continuous time signals are periodic in nature which change with a time period. All real-world signals are continuous time signals temperature, humidity, weather changes over a period of time. All these signals are examples of the continuous time signals.
As shown in the above figure temperature of a room can be classed as a continuous time signal. Temperature is measured between the two values. Cold or hot from Monday to Friday have minimum and maximum points. The continuous time signal is represented by an independent variable of time t. Here x(t) represents the input signals and y(t) represents the output signal over a period of time t.
Most of the physical world signals are tend to be continuous time signal for example voltage, current, temperature etc.
Discrete time system is not continuous but discrete in nature. Discrete-Time signals are not continuous but in form of a sequence.
On the other hand, a discrete-time system is one in which the input signals are not continuous but a sequence or a series of signal values defined in “discrete” points of time. This results in a discrete-time output generally represented as a sequence of values or numbers.
Generally a discrete signal is specified only at discrete intervals, values or equally spaced points in time. So for example, the temperature of a room measured at 1pm, at 2pm, at 3pm and again at 4pm without regards for the actual room temperature in between these points at say, 1:30pm or at 2:45pm.
However, a continuous-time signal, x(t) can be represented as a discrete set of signals only at discrete intervals or “moments in time”. Discrete signals are not measured versus time, but instead are plotted at discrete time intervals, where n is the sampling interval. As a result discrete-time signals are usually denoted as x(n) representing the input and y(n)representing the output.
Then we can represent the input and output signals of a system as x and y respectively with the signal, or signals themselves being represented by the variable, t, which usually represents time for a continuous system and the variable n, which represents an integervalue for a discrete system as shown.
Continuous-time and Discrete-time System
Interconnection of Systems
One of the practical aspects of electronic systems and block-diagram representation is that they can be combined together in either a series or parallel combinations to form much bigger systems. Many larger real systems are built using the interconnection of several sub-systems and by using block diagrams to represent each subsystem, we can build a graphical representation of the whole system being analysed.
When subsystems are combined to form a series circuit, the overall output at y(t) will be equivalent to the multiplication of the input signal x(t) as shown as the subsystems are cascaded together.
Series Connected System
For a series connected continuous-time system, the output signal y(t) of the first subsystem, “A” becomes the input signal of the second subsystem, “B” whose output becomes the input of the third subsystem, “C” and so on through the series chain giving A x B x C, etc.
Then the original input signal is cascaded through a series connected system, so for two series connected subsystems, the equivalent single output will be equal to the multiplication of the systems, ie, y(t) = G1(s) x G2(s). Where G represents the transfer function of the subsystem.
Note that the term “Transfer Function” of a system refers to and is defined as being the mathematical relationship between the systems input and its output, or output/input and hence describes the behaviour of the system.
Also, for a series connected system, the order in which a series operation is performed does not matter with regards to the input and output signals as: G1(s) x G2(s) is the same as G2(s) x G1(s). An example of a simple series connected circuit could be a single microphone feeding an amplifier followed by a speaker.
Parallel Connected Electronic System
For a parallel connected continuous-time system, each subsystem receives the same input signal, and their individual outputs are summed together to produce an overall output, y(t). Then for two parallel connected subsystems, the equivalent single output will be the sum of the two individual inputs, ie, y(t) = G1(s) + G2(s).
An example of a simple parallel connected circuit could be several microphones feeding into a mixing desk which in turn feeds an amplifier and speaker system.
Electronic Feedback Systems
Another important interconnection of systems which is used extensively in control systems, is the “feedback configuration”. In feedback systems, a fraction of the output signal is “fed back” and either added to or subtracted from the original input signal. The result is that the output of the system is continually altering or updating its input with the purpose of modifying the response of a system to improve stability. A feedback system is also commonly referred to as a “Closed-loop System” as shown.
Closed-Loop Feedback System
Feedback systems are used a lot in most practical electronic system designs to help stabilise the system and to increase its control. If the feedback loop reduces the value of the original signal, the feedback loop is known as “negative feedback”. If the feedback loop adds to the value of the original signal, the feedback loop is known as “positive feedback”.
An example of a simple feedback system could be a thermostatically controlled heating system in the home. If the home is too hot, the feedback loop will switch “OFF” the heating system to make it cooler. If the home is too cold, the feedback loop will switch “ON” the heating system to make it warmer. In this instance, the system comprises of the heating system, the air temperature and the thermostatically controlled feedback loop.
Transfer Function of Systems
Any subsystem can be represented as a simple block with an input and output as shown. Generally, the input is designated as: θi and the output as: θo. The ratio of output over input represents the gain, ( G ) of the subsystem and is therefore defined as: G = θo/θi
In this case, G represents the Transfer Function of the system or subsystem. When discussing electronic systems in terms of their transfer function, the complex operator, s is used, then the equation for the gain is rewritten as: G(s) = θo(s)/θi(s)
Electronic System Summary
We have seen that a simple Electronic System consists of an input, a process, an output and possibly feedback. Electronic systems can be represented using interconnected block diagrams where the lines between each block or subsystem represents both the flow and direction of a signal through the system.
Block diagrams need not represent a simple single system but can represent very complex systems made from many interconnected subsystems. These subsystems can be connected together in series, parallel or combinations of both depending upon the flow of the signals.
We have also seen that electronic signals and systems can be of continuous-time or discrete-time in nature and may be analogue, digital or both. Feedback loops can be used be used to increase or reduce the performance of a particular system by providing better stability and control. Control is the process of making a system variable adhere to a particular value, called the reference value.
In the next tutorial about Electronic Systems, we will look at a types of electronic control system called an Open-loop System which generates an output signal, y(t) based on its present input values and as such does not monitor its output or make adjustments based on the condition of its output.