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Square Waves - The basics

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masakabassist

Member
Joined
Aug 31, 2005
Location
Wales!!
Square - Waves

Considering we are all using electronics i thought it would be nice if we all know how it works.

Within electronics square waves are used as a time reference, I.e the clock signal (like that used on a latch). Their extremely fast transitions are well suited to switching synchronous logic circuits at very precise intervals.

Square waves have a very wide range of harmonics. Due to these harmonics, electromagnetic radiation can occur which can interfere with other circuits in the vicinity. These errors are called noise errors.

In computing noise can be considered data without meaning. To avoid noise we use very sensitive circuits such as, analogue to digital converters. In these circuits the sine wave(analogue) is used as the timing signal.

Ideal square waves require that their signal changes from high to low instantaneously. For this to occur we need to infinite bandwidth, which sadly is impossible in real world systems (imagine how fast computers would be then :) ).

Since we only have finite bandwidth, square waves are subject to a phenomenon known as the Gibbs phenomenon (ripple effects, depicted in the picture named 'End Result').

For a reasonable approximation of the square wave shape the fundamental and third harmonic need to be present, with the fifth harmonic being desireable.

These bandwidth requirements are extremely important in digital electronics, where finite - bandwidth analogue to square wave like waveforms are used.

The ratio of the high period to the total period of a square wave is called the duty cycle. A square wave has 50% duty cycle - equal high and low ends.

The average level of the square is given by the duty cycle. By changing the on/off periods and averaging them we can now represent any value between the two time limits. This is the basis of pulse width modulation

For the pictures you will have to have some degree of imagination because I'm not very good with paint lol. :cool:
 

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