- System analysis
:"See also

systems analysis .":"MISO redirects here, for the data line seeSerial Peripheral Interface Bus ."**System analysis**is the branch ofelectrical engineering that characterizes electrical systems and their properties. Although many of the methods of system analysis can be applied to non-electrical systems, it is a subject often studied by electrical engineers because it has direct relevance to many other areas of their discipline, most notablysignal processing and communication systems.**Characterization of systems**A system is characterized by how it responds to input signals. In general, a system has one or more input signals and one or more output signals. Therefore, one natural characterization of systems is by how many inputs and outputs they have:

* "SISO " (Single Input, Single Output)

* "SIMO" (Single Input, Multiple Outputs)

* "MISO" (Multiple Inputs, Single Output)

* "MIMO " (Multiple Inputs, Multiple Outputs)It is often useful (or necessary) to break up a system into smaller pieces for analysis. Therefore, we can regard a SIMO system as multiple SISO systems (one for each output), and similarly for a MIMO system. By far, the greatest amount of work in system analysis has been with SISO systems, although many parts inside SISO systems have multiple inputs (such as adders).

Signals can be continuous or discrete in time, as well as continuous or discrete in the values they take at any given time:

* Signals that are continuous in time and continuous in value are known as "analog signal s".

* Signals that are discrete in time and discrete in value are known as "digital signal s".

* Signals that are discrete in time and continuous in value are called "discrete-time signals". While important mathematically, systems that process discrete time signals are difficult to physically realize. The methods developed for analyzing discrete time signals and systems are usually applied to digital and analog signals and systems.

* Signals that are continuous in time and discrete in value are sometimes seen in the timing analysis of logic circuits, but have little to no use in system analysis.With this categorization of signals, a system can then be characterized as to which type of signals it deals with:

* A system that has analog input and analog output is known as an "analog system".

* A system that has digital input and digital output is known as a "digital system".

* Systems with analog input and digital output or digital input and analog output are possible. However, it is usually easiest to break these systems up for analysis into their analog and digital parts, as well as the necessary analog to digital ordigital to analog converter .Another way to characterize systems is by whether their output at any given time depends only on the input at that time or perhaps on the input at some time in the past (or in the future!).

* "Memoryless" systems do not depend on any past input.

* Systems "with memory" do depend on past input.

* "Causal" systems do not depend on any future input.

* "Non-causal" or "anticipatory" systems do depend on future input. Note: It is not possible to physically realize a non-causal system operating in "real time". However, from the standpoint of analysis, they are important for two reasons. First, the ideal system for a given application is often a noncausal system, which although not physically possible can give insight into the design of a derivated causal system to accomplish a similar purpose. Second, there are instances when a system does not operate in "real time" but is rather simulated "off-line" by a computer.Analog systems with memory may be further classified as "lumped" or "distributed". The difference can be explained by considering the meaning of memory in a system. Future output of a system with memory depends on future input and a number of state variables, such as values of the input or output at various times in the past. If the number of state variables necessary to describe future output is finite, the system is lumped; if it is infinite, the system is distributed.

Finally, systems may be characterized by certain properties which facilitate their analysis:

* A system is "linear" if it has the superposition and scaling properties.

* A system that is not linear is "non-linear ".

* If the output of a system does not depend explicitly on time, the system is said to be time-invariant; otherwise it is time-variant

* A system that will always produce the same output for a given input is said to bedeterministic .

* A system that will produce different outputs for a given input is said to bestochastic .There are many methods of analysis developed specifically for linear time-invariant ("LTI") deterministic systems. Unfortunately, in the case of analog systems, none of these properties are ever perfectly achieved. Linearity implies that operation of a system can be scaled to arbitrarily large magnitudes, which is not possible. Time-invariance is violated by aging effects that can change the outputs of analog systems over time (usually years or even decades).

Thermal noise and other random phenomena ensure that the operation of any analog system will have some degree of stochastic behavior. Despite these limitations, however, it is usually reasonable to assume that deviations from these ideals will be small.**LTI Systems**As mentioned above, there are many methods of analysis developed specifically for LTI systems. This is due to their simplicity of specification. An LTI system is completely specified by its

transfer function (which is arational function for digital and lumped analog LTI systems). Alternatively, we can think of an LTI system being completely specified by itsfrequency response . A third way to specify an LTI system is by its characteristiclinear differential equation (for analog systems) or lineardifference equation (for digital systems). Which description is most useful depends on the application.The distinction between lumped and distributed LTI systems is important. A lumped LTI system is specified by a finite number of parameters, be it the zeros and poles of its transfer function, or the

coefficient s of its differential equation, whereas specification of a distributed LTI system requires a complete function**See also****Important concepts in system analysis***

Transfer function

*LTI system theory

*Feedback andstability

*Frequency response

*Steady-state andtransient behavior

* Filters

*Noise (physics)

* Transforms

**Fourier transform :Continuous Fourier transform &Discrete Fourier transform

**Laplace transform

**Z-transform

*Information theory **Related fields***

Control system andcontrol theory

*Digital signal processing

*Digital image processing

*Telecommunications

*Wikimedia Foundation.
2010.*

### Look at other dictionaries:

**system analysis**— sisteminė analizė statusas T sritis automatika atitikmenys: angl. system analysis vok. Systemanalyse, f rus. системный анализ, m pranc. analyse systématique, f … Automatikos terminų žodynas**system analysis**— sisteminė analizė statusas T sritis Politika apibrėžtis Teorija, politinę sistemą nagrinėjanti kaip susireguliuojančią sistemą. D. Eastonas siekė sukurti visa apimančią politikos teoriją, kur politika suprantama kaip dinamiškas, nenutrūkstamas,… … Politikos mokslų enciklopedinis žodynas**system analysis**— analysis and suggestions for improvement of computer or organizational systems … English contemporary dictionary**System analysis**— Системный анализ … Краткий толковый словарь по полиграфии**Object Oriented System Analysis**— (OOSA) ist eine der früh im Softwareentwurf eingesetzten Modellierungssprachen und wurde von Sally Shlaer und Stephen Mellor entwickelt. Sie enthält eine Vielzahl von Diagrammarten, um die Funktionalität und Struktur von Softwaresystemen zu… … Deutsch Wikipedia**System safety**— The system safety concept calls for a risk management strategy based on identification, analysis of hazards and application of remedial controls using a systems based approach.cite book|title= System Safety Engineering and… … Wikipedia**System of systems**— is a moniker for a collection of task oriented or dedicated systems that pool their resources and capabilities together to obtain a new, more complex, meta system which offers more functionality and performance than simply the sum of the… … Wikipedia**System of Physical Quantities**— of Nikolay A. Plotnikov (SPQ) the classification of physical quantities or physical operators, that makes it possible to reveal their dependence on the geometry of space time and fundamental physical constants in the form of differential… … Wikipedia**Analysis**— (from Greek ἀνάλυσις , a breaking up ) is the process of breaking a complex topic or substance into smaller parts to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle,… … Wikipedia**System**— (from Latin systēma , in turn from Greek polytonic|σύστημα systēma) is a set of interacting or interdependent entities, real or abstract, forming an integrated whole. The concept of an integrated whole can also be stated in terms of a system… … Wikipedia