1 frequency bands

ATS. CH-1. FREQUENCY BAND. (9-84) 1

ATS. CH-1. FREQUENCY BAND. (9-84)

ANALOG COMMUNICATION

Frequency bands

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Frequency Bands

Infrared

Visible spectrum

DESIRED LEARNING OBJECTIVES

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The frequency spectrum is divided into segments and called frequency bands

The purpose of classifying the various portions and how they are used

These segments are designated in frequency spectrum according to their frequency and wave-length

What is frequency bands?

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Name Frequency Wavelength

Extremely Low Frequencies(ELF)Voice Frequencies (VF)Very Low Frequencies (VLF)Low Frequencies (LF)Medium Frequencies (MF)High Frequencies (HF)Very High Frequencies (VHF)Ultra High Frequencies (UHF)Super High Frequencies (SHF)Extremely High Frequencies(EHF)InfraredThe visible spectrum (light)

30-300 Hz300-3000 Hz

3-30 kHz30-300 kHz

300 kHz - 3 MHz3-30 MHz

30-300 MHz300 MHz - 3 GHz

3-30 GHz30-300 GHz

——

107 – 106 m106 – 105 m105 – 104 m104 – 103 m103 – 102 m102 – 101 m101 – 1 m1 – 10-1 m10-1 – 10-2 m10-2 – 10-3 m0.7 – 10m0.4 x 10-6 to0.8 x 10-6 m

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Extremely low frequencies (ELFs) are those in the 30 to 300Hz range

These include ac power line frequencies (50 and 60 Hz are common)

Frequencies in the low end of the human hearing range

Extreme Low Frequency (ELF)

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Voice frequencies (VFs) are those in the range of 300 to 3000 Hz.

This is the normal range of human speech

Human hearing extends from approximately 20 to 20,000 Hz,

Most intelligible sound occurs in the VF range

Voice Frequency (VF)

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higher end of the human hearing range up to about 15 to 20 (kHz)

Many musical instruments also make sounds in this range as well as in the ELF and VF ranges

Govt and military communications. e.g. VLF radio transmission is used by the navy to communicate with ‘submarines'

Very Low Frequency (VLF)

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Low frequencies (LFs) are those in the 30 to 300 kHz range

Primarily used in aeronautical and marine navigation

Subcarriers are signals that carry the baseband modulating information but which, in turn, modulate another higher-frequency carrier

Low Frequency (LF)

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Medium frequencies (MFs) are in the 300 to 3000 kHz [3-megahertz (MHz)] range

The major application of frequencies in this range is AM radio broadcasting (535 to 1605 kHz)

Other services in this range include various marine and aeronautical communications applications

Medium Frequency (MF)

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High frequencies (HFs) are those in the 3 to 30 MHz range known as short waves (SWs).

All kinds of two way radio communications, some shortwave radio broad casting

Govt and military services for two-way communications. Amateur radio and CB communications also occur in this part of the spectrum.

High Frequency (HF)

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Very high frequencies (VHFs) cover the 30 to 300 MHz range

Extremely popular frequency range used by many services

Mobile radioMarine and aeronautical communicationsFM radio broadcasting (88 to 108 MHz)Television channels 2 through 13Radio amateurs

Very High Frequency (VHF)

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Ultra High Frequencies (UHF) 300 to 3000 MHz range. Frequencies above the 1000 MHz [1 gigahertz (GHz)] range are called microwaves

This is an extremely widely used portion of the frequency spectrum. It includes :

UHF television chan nels 14 through 67mobile communicationscellular telephonesmilitary servicesSome radar and navigation services

Ultra High Frequency (UHF)

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The super high frequencies (SHFs) are in the 3 to 30 GHz range

These are microwave frequencies that are widely used for satellite communications and radar

Some specialized forms of two-way radio communications also occupy this region

Super High Frequency (SHF)

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Extremely high frequencies (EHFs) extend from 30 to 300 GHz

Equipment used to generate and receive signals in this range is extremely complex and expensive

Only a limited amount of activity including satellite communications and some specialized radar

Extremely High Frequency (EHF)

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Frequencies higher than 300 GHz are not referred to as radio waves

Sandwiched between the highest radio frequencies and the visible portion of the EM spectrum

The range between approximately 0.01 millimeter (mm) and 700 nanometers (nm)

Infrared

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Infrared is divided into two areas, long infrared (0.01 mm to 1000 nm) and short infrared (1000 to 700 nm)

Infrared refers to radiation generally associated with heat

Infrared is produced by light bulbs, our bodies, and any physical equipment that generates heat

Infrared signals can also be generated by special types of light emitting diodes

Infrared

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It used for special kinds of communications.

Astronomy to detect starsGuidance in weapons systemsNew TV remote-control

Infrared

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The visible spectrum we ordinarily refer to as light

Light is a special type of electromagnetic radiation that has a wavelength in the 0.4- to 0.8m range

Light wavelengths are usually expressed in terms of angstroms (Å). An angstrom is one ten- thousandth of a micron.

The visible range is approximately 8000 Å (red) to 4000 Å (violet)

Visible Spectrum

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Light waves can be modulated and transmitted through glass fibers just as electrical signals

Fiber optics is one of the fastest growing specialties of communications electronics

It has ability to handle a tremendous amount of information. That is, the bandwidth of the base band signals may be very wide

Visible Spectrum

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Light signals can also be transmitted through free space

A laser that generates a extremely narrow light beam at a specific visible frequency

Easily modulated with voice, video and data

Visible Spectrum

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Beyond the visible region are the x-rays, gamma rays, and cosmic rays

These are all forms of electromagnetic radiation, but they do not use for communications systems

X, Gamma & Cosmic rays

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Frequency Bands

Infrared

Visible spectrum

Recap

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What is frequency band?

Which is the most popular frequency band in the EM Spectrum?

What is the use of light in communication?

What are microwave frequencies?

Consolidation

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CONCLUSION

In next period we will discuss Band Width

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ANALOG COMMUNICATION

Bandwidth


What is bandwidth?

Bandwidth & Channel bandwidth

DESIRED LEARNING OBJECTIVES


What is Bandwidth?


Bandwidth is that portion of the electromagnetic spectrum occupied by a signal

It is also the frequency range over which an information signal is transmitted

More specifically, bandwidth (BW) is the difference between the upper and lower frequency limits of the signal or the equipment operation range

What is Bandwidth?


The bandwidth of the voice frequency range from 300 to 3000 Hz

The up per frequency is f2 and the lower frequency is f1. The bandwidth then is

BW = f2 - f1 = 3000 - 300 = 2700 Hz

What is Bandwidth?


What is Bandwidth?

Upper limitLower limit


When information is modulated, the resulting signal occupies a small portion of the spectrum surrounding the carrier frequency

For example, in AM broadcasting, audio signals up to 5 kHz may be transmitted

The modulation process generated sidebands at frequencies above and below the carrier frequency by an amount equal to the modulating frequency

What is Bandwidth?


If the carrier frequency is 1000 kHz and the modulating frequency is 5 kHz,

Then sidebands will be produced at 1000 - 5 = 995 kHz and at 1000 + 5 = 1005 kHz

The modulation process generates other signals which take up spectrum space

It is not just the carrier at 1000 kHz that is transmitted

What is Bandwidth?


The term channel band width is used to describe the range of frequencies required to transmit the desired information

The bandwidth of the AM signal described above is the difference between the highest and lowest transmitting frequencies

BW = 1005 kHz - 995 kHz = 10 kHz


What is channel bandwidth?


An AM broadcast signal, therefore, takes up a 10 kHz chunk of spectrum space

Signals transmitting on the same frequency or on over lapping frequencies will, and interfere with one another

Only a limited number of signals can be transmitted in the frequency spectrum



What is bandwidth?


Recap


Q & A


What is bandwidth?

Which is the difference b/w bandwidth and channel bandwidth?

What is bandwidth if f2 = 100 khz and f1 = 3 khz?

Consolidation


In next period we will discuss More space at higher frequency

Conclusion

1 frequency bands

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