Modulation signal modulation is a fundamental concept in communications and is to use a base signal (which carries the information that we wish to convey) to modify the properties of a carrier signal (typically a pure frequency much higher frequency). In the simplest case, the base signal adjust the amplitude of the carrier, and we have a AM (amplitude modulation). In other methods used to modify the original signal frequency (FM) or phase (PM) of the carrier.
Consider a speech signal v (t) whose Fourier transform is V (). Let's see what happens if we take an ideal carrier, a complex exponential of frequency c and amplitude 1, and we make our voice signal to determine the extent of the carrier:
For properties of the TF we see that the TF of the new signal keeps its shape V () but now is focused on! C, instead of 0. By keeping the way it is clear that we can recover the original signal just going to multiply (ie, demodulating).
In the real world things are a little more complicated. We must work with real signals, so that we can not multiply by complex exponential to modulate or demodulate. Instead we use real sinusoids, for example cos (ct), to modulate our signals. Modular
a signal to amend any of the characteristics of that signal, called carrier, according to the characteristics another called modulating signal.
In the figure, we can see that the carrier signal is modified based on the amplitude of the modulating signal and the resulting signal is shown on the right side of the figure.
The aim of modulating a signal, you have control over it. The control is done on certain elements of a continuous oscillation, these are modified according to the waveform signal to be transmitted.
parameters or fundamental values \u200b\u200bof an analogue signal: Amplitude, Frequency and Phase.
Modulated Signals Continuing
AM: Amplitude Modulation
FM: Frequency Modulation
PM:
Discontinuous Phase Modulation (Pulse)
PAM: Pulse Amplitude Modulation
PWM: Pulse Width Modulation
PPM: Pulse Position Modulation
Frequency Modulation (FM):
Frequency Modulation (FM) is the process of combining a sign of AF (Audio Frequency) with a RF (Radio Frequency) in the frequency range between 88MHz and 108MHz, so that the amplitude of the AF frequency varies RF.
If the modulating signal varies in frequency, has no effect on the maximum and minimum excursions of the carrier frequency, but only determines how quickly or slowly occurring changes in frequency. That is, a lower frequency modulation causes changes to occur at a rate slower, and a higher frequency modulation does occur at a faster rate. However, the variations in amplitude modulation signal if they affect the maximum and minimum excursions of the carrier frequency. A broader signal causes a greater change in frequency and a smaller signal causes a minor change in frequency.
Frequency Bands:
The electromagnetic spectrum is divided into bands of radio frequency links under the rules of regulatory authorities global communications, which are part of the International Telecommunication Union (ITU). The radio frequencies are defined between limits established and respected designers and users. The bands that fit the radio options are described below.
Why is Modula?
modular There are several reasons, including:
• facilitates the spread of the information signal by cable or by air.
• Order the radio spectrum, distributing information channels to each other. • Decreases DIMENSIONS
antennas.
• Optimizes bandwidth of each •
channel to avoid interference between channels.
• Protect Information by NOISE degradations.
• Define the quality of information conveyed.
• Modulation
Kinds Are There?
There are basically two types of modulation: analogue modulation, which is made from analog signal information, such as the human voice, audio and video in electrically and digital modulation, which takes place from signals generated by digital sources, such as a computer.
• Analog modulation: AM, FM, PM
• Digital Modulation: ASK, FSK, PSK, QAM
•
Canal How does the signal?
depends on the medium or channel, as there are some better than others, but also depends on the modulation type and application. The main effects
gets the signal to propagate are
• Attenuation • Fainting • White Noise Additive
• External interference
• phase noise signal
• Reflection Refraction
• • • Scattering Diffraction
What relationship between the modulation and channel?
channel strongly influences the choice of modulation of a communication system, mainly due to noise.
• CHANNEL: Noise, distortion, interference and attenuation.
• MODULATION noise immunity, protects the quality of information, avoids interference.
Definition of Convolution 
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