In many examples we take square waves as digital signals. But a digital signal should be discontinuous in time and must have a finite amplitude level. Another explanation that negates a square wave being digital is " According to fourier analysis a square wave can be represented as the sum of harmonics of infinite number of sinusoidal signal". Hence we can say that a square wave is not digital in nature. As it has only two level of amplitude it would be wrong if one says that it is analog because an analog signal must have an infinite number of amplitudes, i.e. be continuous in amplitude.
Is it correct to say that a pure squarewave is a "signal"?
I rather think that a squarewave does not carry any information and, hence, cannot be regarded as a "signal". The same applies to a sinusoidal wave.
Square wave signal is considered 100% digital.Digital Signal carries only two state, zero or one, hence in the square wave, if lower edge consider reference zero level, then the higher level is considered as one, in all digital ICs (I/O, Memory, Buffer or CPU etc, on mother board) operates on, the common raferance clock (square wave), to synchronize the digital operations, of all to gather. Other signals, on data(BDB), control or address bus are also square but with different time period, working on common raferance, the synchronizing clock signal.
The transition from zero to one or from one to zero, if not immediate generate impurity (harmonics) which is avoided, by considering signal, after certain delay, for accuracy and reliability of mother board operation.
Perhaps you need to be more specific when you say "digital"
First of all, with regard to the dependent variable (e.g. voltage level) the square wave signal is discrete because it only can take a finite number of values (two = digital). However, with regard to the independent variable (e.g., time) this signal is continuous as you can see by using an oscilloscope.
@bhupendra desai: can we store a square wave in memory?
Definitely a square wave used as clock in synchronous circuit, it doesn't implies that a square wave is digital in nature
Lutz von Wangenheim:
In a pure square wave at each discontinuity it has information that a sudden change in input occurs at periodic interval. And a sinusoidal wave can carry information in its envelope ( As in Amplitude modulation )
@ Nandan Kumar Jha:
I know that a modulated wave carries information because this is the reason for modulation.
By mentioning a "sinusoidal wave" I mean, of course, an unmodulated waveform. The questioner uses the term "square wave as digital signal" - and thefore I still believe that neither an unmodulated squarewave nor an unmodulated sinusoidal wave can be regarded as a "signal".
Only after variation of one suitable property of such a wave (amplitude, phase, frequency) we can speak of a "signal" that carries some information which is contained in these deviations.
This is a definition in accordance with the system theory.
By the way: By suitable modulation a squarewave can carry an analog signal.
Would you describe such a system as a "digital signal" carrying an "analog information"?
Lutz von Wangenheim
can you please tell me that why a unit step signal is treated as signal . I mean which type of information it has ?
It is not easy to give a satisfying answer.
Is there really a common agreement that a unit step is to be "treated as a signal"?
I am not sure about this. And - as you know, everyday used technical language is not always in concidence with (sometimes abstract) definitions.
I know that it is common to speak about a "step signal" or a "squarewave signal".
But if we try to be exact and in accordance with corresponding definitions, I think the unit step is NOT a signal. According to my knowledge, only a time-varying quantity that carries any kind of information can be called a "signal". May be I am wrong?
On the other hand, a voltage step CAN be considered as a signal if its pure existence carries the information.
Example:
* A input step for measuring the step response of a system is not a "signal"
* If within a certain communication system the existence of such a step at a certain time gives the user an information, it must be seen as a "signal".
What about the frequency of the square wave? Could this not be considered information? Perhaps not intentional, but as Lutz von Wangenheim has stated, if it is intended to be treated as a signal, than it must be seen as a signal.
If we call DC as signal then we have to consider unit step as signal... and as far as square wave is consider.. i think we can consider it as a DC signal modulated by discrete values
Digital signal is a square wave signal which contains encoded information which is represented by bit 1 and 0 ....... then square waves that do not contain binary information cannot be categorized as digital signals. (TW Wisjhnuadji 2019).
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