Basic telecommunications
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BASIC TELECOMMUNICATIONS . RF (Radio Frequency) technology . BASIC TELECOMMUNICATIONS .

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BASIC TELECOMMUNICATIONS

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Basic telecommunications

BASIC TELECOMMUNICATIONS

RF (Radio Frequency) technology


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BASIC TELECOMMUNICATIONS

Radio frequency (RF) is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals. RF usually refers to electrical rather than mechanical oscillations

  • The RF spectrum is very large and encompasses many different types of frequencies, we’re going to concentrate on radio waves


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BASIC TELECOMMUNICATIONS

  • Electric currents that oscillate at radio frequencies have special properties not shared by direct current or alternating current of lower frequencies

  • The energy in an RF current can radiate off a conductor into space as electromagnetic waves (radio waves); this is the basis of radio technology


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BASIC TELECOMMUNICATIONS

In order to receive radio signals an antenna must be used however, since the antenna will pick up thousands of radio signals at a time, a radio tuner is necessary to tune in to a particular frequency (or frequency range)


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BASIC TELECOMMUNICATIONS

This is typically done via a resonator – in its simplest form, a circuit with a capacitor and an inductor forming a tuned circuit, the resonator amplifies oscillations within a particular frequency band, while reducing oscillations at other frequencies outside the band

Simple radio tuner


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BASIC TELECOMMUNICATIONS

Radio frequencies


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BASIC TELECOMMUNICATIONS

  • Visible light is an electromagnetic wave, consisting of oscillating electric and magnetic fields traveling through space.

  • The frequency of the wave determines its color: 4×1014Hzis red light, 8×1014 Hz is violet light, and between these (in the range 4-8×1014 Hz) are all the other colors of the rainbow

    400,000,000,000,000 = 4THz (400 Trillion Hz)


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BASIC TELECOMMUNICATIONS

Here is the visible

light spectrum that

we can see


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BASIC TELECOMMUNICATIONS

  • The audible frequency range for humans is typically given as being between about 20 Hz and 20,000 Hz (20 kHz)

  • Sound is made up of changes in air pressure in the form of waves. Frequency is the property of sound that most determines pitch

  • Mechanical vibrations perceived as sound travel through all forms of matter: gases, liquids, solids, and plasmas, sound cannot travel through a vacuum


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BASIC TELECOMMUNICATIONS

As a matter of convenience, longer and slower waves, such as ocean surface waves, tend to be described by wave period rather than frequency. Short and fast waves, like audio and radio, are usually described by their frequency instead of period. These commonly used conversions are listed below:


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BASIC TELECOMMUNICATIONS

  • A radio communications signal must occupy a range of frequencies carrying most of its energy, called its bandwidth

  • Bandwidth in it’s simplest form is info carrying capacity

  • Allocation of radio frequency ranges to different uses is a major function of radio spectrum allocation


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BASIC TELECOMMUNICATIONS

Now that you know the basics of RF and the frequency spectrum let’s take a look at Modulation.

Modulationis the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted


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BASIC TELECOMMUNICATIONS

Frequency

modulation,

the red signal is

impose on the

green carrier

wave and the

output is the

blue waveform


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