Antenne wi-fi Définition Caracteristiques

Antenna wi-fi Defining Characteristics

  2. TheWiFi antenna is a computer accessory of the most important. It aims to achieve your WiFi network. TheWiFi antenna is defined as follows: Thewireless antenna is part of a set of walkie -Fi, or facility receiving wireless (radio), designed to radiate or receive waves wireless (radio) .
    TheWiFi antenna is a device for radiating or remote capture waves Fi (electromagnetic) in a device or a transmitting station and receiving wireless (eg a wireless access point)

    This obliges us to give you the definition of the radio wave or rather electromagnetic

    1. Perturbation propagating in a medium so that at any point of this medium size used to measure the disturbance is a function of time, while at all times, moving at a point depends on the coordinates of this point .
    2. or
    3. Changing the physical state of a propagating medium following a local disturbance.
    4. or
    5. Oscillation, that is to say periodic variation of a physical state, which propagates in space or in matter.
    6. An outline will be most telling:
      antenne wifi antenne wifi omnidirectionnelle: Being the wavelength.

    WiFi :   Group of techniques that can wirelessly transmit data from a network using Ethernet.

    Systems implemented using a frequency band located around 2.4 GHz or 2489 (GHz) and flows can vary between 2 and 54 megabits per second (Mbps). The technology of wireless Ethernet been developed in the United States by the WECA (Wireless Ethernet Compatibility Alliance). The work of this association that brought together several companies gave birth to standard Wi-Fi (802.11b). The abbreviation Wi-Fi is wireless fidelity. After the huge success of this new standard, whose name was later also used to designate the 802.11a and 802.11b, WECA in 2002 became the Wi-Fi Alliance.

  4. The wifi antenna is an electrical conductor more or less complex, generally placed in an open area so that the waves WiFi can reach it without impediment ..

    TheWiFi antenna is defined by the following characteristics:
    • Frequency of use of thewifi antenna2.4Ghz
    • Type ofantenna wifi
    • Power handling issue of thewifi antenna
    • Directivity, gain and radiation pattern before thewifi antenna
    • Size and shape of theantenna wifi
    • Polarization of theantenna wifi
    • Feeding method and feed point impedance of theantenna wifi
    • Strength of thewifi antenna

Shape and dimensions of theantenna wifi

The shape and dimensions of a WiFi antenna in general is extremely variable: that of a cell phone is limited to a small protrusion on the camera body while the parable of the radio telescope exceeds 100 m in diameter. Very roughly we can say that for the same frequency, the dimensions of a WiFi antenna will be even greater than his gain will be high due to the use of reflective elements, as for the dish , for example. These antennas wifi no exception to the rule. The half-wave antenna, as its name implies, has a length almost equal to half the wavelength at which it was manufactured.

Antenna types

There are dozens of types of antennas, different in function, geometry, technology ... Some examples:
  1. antenna or umbrella tablecloth LF
  2. loop antenna (loop) of different shapes (square, triangle, rhombus ...), vertical or horizontal.
  3. wire dipole antenna for HF.
  4. yagi-uda to parasitic elements, highly directional and high gain.
  5. quarter-wave vertical antenna omnidirectional very high frequency (VHF or VHF).
  6. curtain or collinear antenna directivity to very marked.
  7. magnetic loop antenna of reduced size.
  8. dielectric antenna or surface waves.
  9. helical antenna for UHF, very directive.
  10. satellite dish to centimeter wave (microwave).
  11. slot antenna at millimeter wave
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Antennas Wi-Fi - WLAN Antenna

Omnidirectional Antennas 

Antenna rod basic omnidirectional 2.4 GHz.

For this type of antenna are:

  • the dipole looks like a pen and is the basic antenna rod (¼ wavelength) is most encountered. It is omnidirectional, 0 dBd gain, and is dedicated to serving nearby. She also team Wireless Camera Wireless Digital 2.4 GHz (CE compliant) for an EIRP (Equivalent Isotropic Radiated Power) of maximum 100 mW, 20 dBm. (Standard D code = 500 m sight).
  • Thecollinear antenna is often installed on the roof. It is omnidirectional, its gain, 7 to 15 dBi, is related to its vertical dimension up to 2 meters.

These first two descriptions, operating in bias V, can be regarded as antennas or docking base as compatible with a 360 ° environment.

Ex directional antennas: Yagi

  • Theantenna panel may be an internal network ofquad antenna orpatch antenna, or an array of dipoles. Begins to gain 8 dBi (8 × 8 cm) to achieve 21 dBi (45 × 45 × 4.5 cm). It's the antenna that provides the best value gain / bulk and also the best performance, which is around 85 to 90%. Beyond this maximum gain, it is no longer manufactured, problems arise because of coupling (losses) between the dipoles and floors should also consider doubling the surface. The volume of a panel antenna is minimal.
  • The antenna type dish solid or perforated (mesh). His interest in employment lies in the pursuit of profit obtained from a theoretical diameter of approach as follows:
    • 18 dBi = 46 cm,
    • 19 dBi = 52 cm,
    • 20 dBi = 58 cm,
    • 21 dBi = 65 cm,
    • 22 dBi = 73 cm,
    • 23 dBi = 82 cm,
    • 24 dBi = 92 cm,
    • 25 dBi = 103 cm,
    • 26 dBi = 115 cm,
    • 27 dBi = 130 cm,
    • 28 dBi = 145 cm,
    • 29 dBi = 163 cm,
    • 30 dBi = 183 cm.

The yield of the dish is average, 45 ~55%. The volume of the antenna, which takes account of the hinge, so the focusis significant.

A satellite dish (eg GST / CS Headless 11 -12 GHz) is usable with Wi-Fi, provided you provide a suitable source: horn, patch or quad single or double, etc..

Antenna selection 

Gain antennas are omni-directional or intended for "longer range" as possible, a few kilometers.

The panels and parabolic antennas are directional only, that is to say they favor a preferred direction (more or less open) at the expense of other undesirable.

It finds that the panel antennas are often preferred (even better) when the link budget is favorable, but as soon as the system must be more efficient, the parables are required. The balance point at 21 dBi, is done with a square of side panel 45 cm and the other a dish d = 65 cm.

In conclusion, directional, or point to point, it is interesting to equip themselves with a first panel and, if circumstances require, a parable.

The Wi-Fi antennas are usually equipped with SMA, RP-SMA or N according to the manufacturer. However, the antenna gain (in dBi or dBd) used to broadcast (receive free) must comply with regulations EIRP (Equivalent Isotropic Radiated Power).

Other antennas [

There are other antennas, less known, and those designed by wifistesas thehorn antenna, the antenna 2.5 GHz amateur embodiment, the Yagi, angles, dihedrals, the "discones" etc.. but only rods, panels and satellite dishes are significantly used.

To enhance trade, it can be mounted closer to the antenna an antenna preamplifier (RX) with or without amplifier

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