Everything about Analog Signal totally explained
An
analog or
analogue signal is any time
continuous where some time varying feature of the signal is a representation of some other time varying quantity. It differs from a
digital signal in that small fluctuations in the signal are meaningful. Analog is usually thought of in an
electrical context; however,
mechanical,
pneumatic,
hydraulic, and other systems may also convey analog signals.
An analog signal uses some property of the medium to convey the signal's information. For example, an
aneroid barometer uses rotary position as the signal to convey pressure information. Electrically, the property most commonly used is
voltage followed closely by
frequency,
current, and
charge.
Any information may be conveyed by an analog signal; often such a signal is a measured
response to changes in physical phenomena, such as
sound,
light,
temperature,
position, or
pressure, and is achieved using a
transducer.
For example, in sound recording, fluctuations in air
pressure (that is to say,
sound) strike the diaphragm of a
microphone which causes corresponding fluctuations in a voltage or the current in an electric circuit. The voltage or the current is said to be an "analog" of the sound.
Since an analogue signal has a theoretically infinite resolution, it'll always have a higher resolution than any digital system where the resolution is in discrete steps. In practice, as analogue systems become more complex, effects such as non linearity and noise ultimately degrade analogue resolution to such extent that digital systems surpass it. In analogue systems it's difficult to detect when such degradation occurs, but in digital systems, degradation can not only be detected, but corrected as well.
Disadvantage
The primary disadvantage of analog signaling is that any system has
noise – for example, random variation. As the signal is copied and re-copied, or transmitted over long distances, these random variations become dominant. Electrically, these losses can be diminished by shielding, good connections, and several cable types such as
coaxial or
twisted pair.
The effects of
noise make signal loss and distortion impossible to recover, since amplifying the signal to recover attenuated parts of the signal amplifies the noise as well. Even if the resolution of an analog signal is higher than a comparable digital signal, in many cases, the difference is overshadowed by the noise in the signal.
Modulation
Another method of conveying an analog signal is to use
modulation. In this, some base signal (for example, a
sinusoidal carrier wave) has one of its properties modulated:
amplitude modulation involves altering the amplitude of a sinusoidal voltage
waveform by the source information,
frequency modulation changes the
frequency. Other techniques, such as changing the
phase of the base signal also work.
Analog circuits don't involve
quantisation of information into digital format. The concept being measured over the circuit, whether sound, light, pressure, temperature, or an exceeded limit, remains from end to end.
Clocks with hands are called analog; those that display digits are called digital. However, many analog clocks are actually digital since the hands don't move in a smooth continuous motion, but in small steps every second or half a second, or every minute.
See
digital for a discussion of
digital vs. analog.
Sources: Some of an earlier version of this article was originally taken from
Federal Standard 1037C in support of
MIL-STD-188.
Further Information
Get more info on 'Analog Signal'.
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