The mobile world has increased dramatically and have to grow with it, but I am determined to make us go to another world called 4G world, a world that includes the merger of two computers and phones. With your team, you can also make calls, and make beautiful. but is a very complex. But do you know about the world of mobile computing. I'll explain below: -
MOBILE WORLD computing
A transmitting antenna are the waves generated by electrical signals within a device such as a radio and converts them into waves traveling in an open space. The waves are generated by electrical signals in radios and other devices are known as guided waves as they travel through transmission lines, as a son or cables. The waves that move in an open space is usually referred to as waves of free space on your journey through the air or space without the need for a transmission line. A receiving antenna is in free space waves and converts them into guided waves.
Radio waves are a type of electromagnetic radiation, a form of rapid change or oscillation of energy. Radio waves have two related properties known as the frequency and wavelength. Frequency refers to the number of times per second that a wave oscillates, or varies in intensity. The wavelength is equal to the wave speed (the speed of light is 300 million m / s) divided by frequency. Radio waves at low frequencies have long wavelengths (measured in hundreds of meters), while the high frequency radio waves have short wavelengths (measured in centimeters).
The antenna can radiate radio waves in free space from the transmitter, or it can receive radio waves and direct them to the receiver, where they are transformed into the original message. For example, sending an AM radio broadcast, radio, first generates an energy carrier wave at a certain frequency. Carrier has been modified to carry a message, such as music or the voice of a person. Amended by radio waves, then along the transmission line inside the radio, like cable or cord, antenna. Transmission line, often referred to as the element of power. When the waves reach the antenna, which oscillate along the length of the antenna and back. Each vibration pushes the electromagnetic energy the antenna radiates energy to space as radio waves.
The antenna of a radio receiver behaves in the same way. Because radio waves travel through space to reach the antenna, they have implemented, or induce a weak electric current in the antenna. The current pushes volatile energy radio waves along the antenna, which is connected to a radio receiver transmission line. Radio waves radio receiver amplifier and sent to a loudspeaker that reproduces the original message.
III. FEATURES antennas
Microwave tower
Microwave transmissions are beamed from point to point through the long antennae. Antennas are in sight of one another, because the microwave signals travel in straight, narrow paths.
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An antenna size and shape depend on the frequency or wavelength for radio waves that are sent or received. The design of the transmitting antenna is usually not different from a receiving antenna. Some units use the same antenna for both purposes.
A. Size
An antenna works best when its physical size is a quantity known as the size of the power antenna. The size of antenna energy depends on the wavelength of radio waves are sent or received. An antenna radiates energy most effectively when its length is a particular fraction of the wavelength design. When the length of an antenna is a large fraction of the corresponding wavelength (quarter-wavelength or half wavelength is often used), radio waves oscillating back and forth along the antenna will meet each other so that the crests of the waves interfere with each other. The waves of resonance, or be in harmony, then the antenna radiates with maximum efficiency.
If the antenna is not long enough or too long for radio frequency, wave crests meet and interfere with each other as they travel back and forth along the antenna, which reduces efficiency. The antenna then acts as a capacitor or coil (depending on the shape of the antenna) and the shop, and radiates energy. Electrical length of the antenna can be changed with the addition of a loop of wire is known as the loading coil the other end of the antenna, which increases the amount of wire antenna. Loading coils are used in a practical antenna length is too long. Adding a short antenna coil increases the length of your power antenna, to improve its resonance with the desired frequency, and increases the efficiency of the antenna.
Radio waves are used by AM radio wavelengths of about 300 m (1000 ft). Most of the AM transmitter antennas are built to a height of about 75 meters (about 250 m), which in this case is a quarter wavelength. When the tower of this height, AM radio antenna emits radio waves more effectively. Since the antenna, which is 75 meters high, it would be impractical portable AM radio receiver, AM radio using the radio antenna wire inside kelakehdoilla. The coil wire is wrapped around the iron as a magnetic material called ferrite. When radio contact with the wire of the coil, creating an electrical charge inside the coil. Magnetic ferrite helps to limit and focus the electric coil and AIDS at the reception.
TV and FM radio transmission towers, and tall, but use shorter wavelengths, but much higher than AM radio frequencies. That's why FM and TV radio waves have wavelengths of only 3 m (10 m). As a result, appropriate antennae are much shorter. Buildings and other obstacles near the ground to prevent these high-frequency radio waves. This tower is used to raise the antennas above these obstacles, so that a higher transmission range. Receiving antennas of televisions and FM radio is small enough to install these devices themselves, but the antennas are often mounted high above the rooftops for better reception.
Form B.
Antennas come in a variety of ways. One of the simplest types of antenna is called a dipole. A dipole consists of two pieces of metal, each connected to one of the child, leading to a radio or communication device. The two pieces of metal are generally arranged end to end with the cable receiver or transmitter power of each length of the dipole in the center. The dipoles can be adjusted to form a straight line or V-shaped for better reception. Each length of metal in the dipole is usually a quarter wavelength, so the total length of the dipole from end to end is a half wavelength. The familiar "rabbit-ear" antenna on top of a television antenna is a dipole.
Another common form of half-dipole antenna is an antenna or a monopoly, which uses one quarter wavelength of a piece of wire connected to a transmitter or receiver twin. Other cables connected to the ground, or point, which is not connected to the rest of the circuit. Case for radio or cell phone is often used in the country. Portable telescopic antenna FM radio is a monopoly. This provision is not effective as using both ends of the dipole, but the monopoly is usually enough to take a nearby FM signals.
Satellites and radar telescopes use microwave signals. Microwaves are very high frequencies, and therefore the very short wavelengths (less than 30 cm). The microwaves travel in straight lines, such as light waves do. Satellite dishes are often used to collect and focus the microwave signals. The dish focuses the microwave and aim an antenna in the middle of the plate. Horn antennas are also used to focus microwaves for transmission and reception.
C. Directivity
Directivity of the antenna is an important quality. It describes how well the antenna would be the seal or beams of radio waves in a certain direction. Dipole send or receive the majority of its perpendicular energy to the lengths of metal, but just a bit 'of energy is transferred along them. If the dipole is mounted vertically, as usual, is so far from the center of the antenna radiates in all directions. However, commercial radio or television station, the transmitting antenna is often designed to concentrate the energy radiated in certain directions and suppress it in others. For example, many of the dipole can be used together if placed close to each other. This provision is called a multi-tank-containers, antenna, also known as a string.
The elements used in a table is generally the same type. Some tables have the ability to move, or to scan beam in different directions. These tables are commonly known as scanning tables.
The tables are usually electrically large and directivity than single antenna element. From its high directivity, the tables can be captured and delivered to beneficiaries a greater amount of energy. Two communal tables that are used for television reception on the roof are the table of Yagi-Uda and log-periodic array.
A Yagi-Uda consists of one or more dipoles mounted on a crossbar. The dipoles are of different lengths, corresponding to different frequencies used in the transmission of television. Additional pieces of metal, called directors and reflectors that are placed on the crossbar at the front and back of the dipoles. Directors and reflectors are not physically connected to the supply element of the antenna at all, but simply to reflect and concentrate the radio waves against the directors. Yagi-Uda antennas are highly directional and receive antennas of this type are often mounted on towers of rotation or bases, such as those antennas can be turned to the source of the requested transfer. Log-periodic arrays are similar Yagi-Uda arrays, but all the elements of an array log-periodic dipole is active elements of different lengths. The dipoles are carefully spaced to allow signal reception over a wide frequency spectrum.
Although the dipole, monopole, a microwave dish, Horn, Yagi-Uda and log-periodic antennas are the most common, and many other models also exist to communicate on different frequencies. Underwater diving trip can receive coded radio commands to the beach, with extremely low frequency (ELF) radio waves. To receive these signals, the submarine landed very long wire antenna on the back, because it goes underwater. Crews of television transmission systems in locations outside the studio, a powerful transmitter of microwave antennas, which can send signals from satellites or directly to the television station. Amateur or "ham" radio enthusiasts, who tend to use the frequencies between AM and FM antennas are often built their own, adapting them to send and receive signals from the desired frequencies.
Properly organizing the individual elements, and good supply signals to the elements, the waves spread may be better to focus on a particular audience, for example, without loss of broadcast signals on uninhabited areas.
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