Digital VS Analog Signal

Definition of Digital and Analog;- 

Data can be analog or digital.. The term analog data refers to information that is continuous; digital data refers to information that has discrete states. Analog data take on continuous values Digital data take on discrete values.To be transmitted, data must be transformed to electromagnetic signals.

Data can be analog or digital.

Analog data are continuous and take continuous values.

Digital data have discrete states and take discrete values.

A signal is an electromagnetic or electrical current that carries data from one system or network to another. In electronics, a signal is often a time-varying voltage that is also an electromagnetic wave carrying information, though it can take on other forms, such as current. There are two main types of signals used in electronics: analog and digital signals. This article discusses the corresponding characteristics, uses, advantages and disadvantages, and typical applications of analog vs. digital signals..

In data communications, we commonly use periodic analog signals and nonperiodic digital signals.

Analog and digital signals are used to transmit information, usually through electric signals. In both these technologies, the information, such as any audio or video, is transformed into electric signals. The difference between analog and digital technologies is that in analog technology, information is translated into electric pulses of varying amplitude. In digital technology, translation of information is into binary format (zero or one) where each bit is representative of two distinct amplitudes..

Analog Signal

An analog signal is time-varying and generally bound to a range (e.g. +12V to -12V), but there is an infinite number of values within that continuous range. An analog signal uses a given property of the medium to convey the signal’s information, such as electricity moving through a wire.. In an electrical signal, the voltage, current, or frequency of the signal may be varied to represent the information. Analog signals are often calculated responses to changes in light, sound, temperature, position, pressure, or other physical phenomena..

When plotted on a voltage vs. time graph, an analog signal should produce a smooth and continuous curve. There should not be any discrete value changes..

Definitions of Analog vs. Digital signals

An Analog signal is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, that is ., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are meaningful.

holi

A digital signal uses discrete (discontinuous) values. By contrast, non-digital (or analog) systems use a continuous range of values to represent information. Although digital representations are discrete, the information represented can be either discrete, such as numbers or letters, or continuous, such as sounds, images, and other measurements of continuous systems..

Properties of Digital vs Analog signals

Digital information has certain properties that distinguish it from analog communication methods. These include

·         Synchronization – digital communication uses specific synchronization sequences for determining synchronization.

·         Language – digital communications requires a language which should be possessed by both sender and receiver and should specify meaning of symbol sequences.

·         Errors – disturbances in analog communication causes errors in actual intended communication but disturbances in digital communication does not cause errors enabling error free communication. Errors should be able to substitute, insert or delete symbols to be expressed.

·         Copying – analog communication copies are quality wise not as good as their originals while due to error free digital communication, copies can be made indefinitely.

·         Granularity – for a continuously variable analog value to be represented in digital form there occur quantization error which is difference in actual analog value and digital representation and this property of digital communication is known as granularity.

Differences in Usage in Equipment

Many devices come with built in translation facilities from analog to digital. Microphones and speaker are perfect examples of analog devices. Analog technology is cheaper but there is a limitation of size of data that can be transmitted at a given time.

Digital technology has revolutionized the way most of the equipment work. Data is converted into binary code and then reassembled back into original form at reception point. Since these can be easily manipulated, it offers a wider range of options. Digital equipment is more expensive than analog equipment.

Comparison of Analog vs Digital Quality

Digital devices translate and reassemble data and in the process are more prone to loss of quality as compared to analog devices. Computer advancement has enabled use of error detection and error correction techniques to remove disturbances artificially from digital signals and improve quality.

Differences in Applications

Digital technology has been most efficient in cellular phone industry. Analog phones have become redundant even though sound clarity and quality was good.

Analog technology comprises of natural signals like human speech. With digital technology this human speech can be saved and stored in a computer. Thus digital technology opens up the horizon for endless possible uses.

Digital vs. Analog Transmission

Two forms of transmission:

•    digital transmission: data transmission using square waves

•    analog transmission: data transmission using all other waves

Four possibilities to consider:

•    analog data via analog transmission

→ “as is” (e.g., radio)

•    analog data via digital transmission

→ sampling (e.g., voice, audio, video)

•    digital data via analog transmission

→ broadband & wireless

•    digital data via digital transmission

→ baseband (e.g., Ethernet)

Why consider digital transmission? Common to both: problem of attenuation.

•    decrease in signal strength as a function of distance

•    increase in attenuation as a function of frequency

Rejuvenation of signal via amplifiers (analog) and re- peaters (digital).

Delay distortion:   different frequency components travel at different speeds.

Most problematic: effect of noise

−→ thermal, interference, ...

•    Analog:   Amplification also amplifies noise—filtering out just noise, in general, is a complex problem.

•    Digital: Repeater just generates a new square wave; more resilient against ambiguitity. 

Analog transmission of digital data

Three pieces of information to manipulate:   amplitude, frequency, phase.

•    Amplitude modulation (AM): encode bits using am- plitude levels.

•    Frequency modulation (FM): encode bits using fre- quency differences.

•    Phase modulation (PM): encode bits using phase shifts.

Digital and Analog Quantities

⚫   An analog quantity is one having continuous values.

⚫   A digital quantity is one having a discrete set of values

⚫   The real world is analog!

⚫   Most things that can be measured quantitatively occur in nature in analog form.

⚫   Examples: air temperature, pressure, distance, sound.

⚫   Interfacing between analog and digital is important.

⚫   Digitization

1.      Sampling: Discretize the time

⚫  Get sampled values of the analog signal.

2.            Quantization: Discretize quantity  values

⚫  Convert each sampled value to a binary code.