To legitimize the
wireless network In the RF, an electromagnetic network operating outside the building, the production area, exceeding the signal power, a fixed threshold, must be registered. The law contains a long series of exceptions concerning the height of the device, the destination. A number of obstacles and double interpretations explain the opinion that has developed among hardware developers: a long-range Wi-Fi antenna must remain passive. Certainly reduces energy costs, makes the electromagnetic background of the area favorable.
How to make a passive radiator amplify a signal has been known for a long time - the radiation pattern is supplied with one or two sharply marked directions: the main part of the energy will be limited.
Reminds a narrow river bed. While the shores are far apart, the flow is calm. It is necessary to hold the flow of a narrow sleeve, water boils, flows faster, the speed increases.
Wi-Fi long-range antenna is guided by a similar principle, transmitting the power reserve in the right direction. The gain, expressed as isotropic decibels( dBi), characterizes the property of the radiator - to increase the energy density of individual directions.
Immediately appears a restriction - the coverage area is sharply narrowed. Dignity is obvious - full liquidity through the eyes of the law, since the total radiated power falls under the restrictions.
Who needs a higher signal level, buy additional amplifiers, legally legitimize the purchase of a fixed order. Avoid forgetting: some transmitters are subject to EIRP restrictions. The parameter from a completely innocuous access point can make an object subject to mandatory licensing. Represented by the product of the total supplied antenna power gain.
For example, with some power emitted by an omnidirectional antenna, a license is not needed. When replacing a narrow model with a model, a situation may arise when the EIRP goes beyond what is permitted. The probability is higher, the greater the gain of the product.
The issue was discussed in detail, since not one organization was penalized for non-compliance with the elementary requirements imposed on wireless networks. Outdoor antenna Wi-Fi can become a real stumbling block ill-considered use.
Principles of operation of long-range antennas
The implementation of narrowed radiation patterns moves in two ways:
- Using special-shaped reflectors.
- Creating phased arrays.
The scientific terms, translated into a language understandable to most, do not look frightening. Reflector - reflector. Satellite dishes use part of the surface of a paraboloid with an emitter placed in focus. The school law of optics is used: rays that fall perpendicular to the lens are collected by one point. The parabolic antenna reflector acts as a lens of electromagnetic waves.
For an engineer, the further course of thought is obvious, most common people ask a curious question: if the rays fall in parallel, how is the phenomenon related to the transmission, the directivity pattern?
Antenna properties are identical in both directions of movement of electromagnetic waves. Radiated energy will be propagated by parallel rays, causing a narrowing of the radiation pattern. The flow goes in the direction perpendicular to the aperture of the reflector, the range of the Wi-Fi antenna increases. To understand this point, it is useful to imagine a searchlight beating thinly over a long distance.
A coherent theory of phased antenna arrays has not been created; practical developments, including the efforts of domestic institutions, will allow us to achieve excellent results using methods based on empirical research. Scientists use well-known tykovy technique. It looks more reasonable from a theoretical point of view, the essence is as follows.
Proved: emitters arranged in a certain order form a total radiation pattern more narrow than individually. It is accepted - there are exceptions - to place in even rows, like the seats of the auditorium. Narrowing occurs in a plane perpendicular to the line of emitters.
Further development of design ideas is clear. For example, four plates — called patches — at the corners of a square narrow the directivity pattern in the vertical and horizontal directions. The principle used by the Wi-Fi TP Link TL-ANT2414A antenna.
Combined Versions of
A well-thought-out combination of a reflector, even rows of emitters gives excellent results. Such is the two-circuit design of the UHF range on square emitters arranged symmetrically with the figure eight.
Due to the equivalence of two perpendicular to the plane of the location of the direction emitters, the antenna radiates( receives) the signal in both directions. The defect reduces the gain, contributing to the manifestation of the multipath effect, which introduces additional overhead in the communication process. Reflector fixes the problem.
Practical implementation examples of long-range antennas
Wi-Fi antennas with a parabolic reflector
The outdoor Wi-Fi antenna TL-ANT5830B is equipped with a truncated paraboloid reflector. Constructors were interested in the narrowing of the radiation pattern in the horizontal plane( azimuth).Vertically( elevation angle), a large width of the main lobe is obtained, the general direction of energy propagation.
The above features are implemented with a reflector, the width of which in the horizontal plane exceeds the vertical dimension - height. The selected form of the reflector will effectively compress the flow in azimuth, giving the elevation angle more room for the receivers of subscribers.
Such outdoor Wi-Fi antennas are suitable for two-way communication, unsuitable for broadcasting. Particular attention is paid to the value of the eirp, the gain of the product is 30 dBi.
Reception and transmission are conducted at a frequency of 5 GHz, the reflector is made of a mesh, reducing the mass, wind load.
In passing, it is worth mentioning two features of antennas with a narrow radiation pattern:
- The stability of communication is made by adjustments to the wind. Despite the significant removal of subscribers, a small angular size, gusts of air masses, rocking the product, can cause a temporary loss of signal.
- Adjusting the exact position of the plate is difficult. Narrow beam should fall on the subscriber. In addition, direct visibility is required to organize the channel.
The range of a Wi-Fi antenna with a parabolic reflector is the maximum possible.
Phased Wi-Fi arrays
The mentioned TL-ANT2414A model achieves a narrowing of the radiation pattern with two horizontal rows of patches of four pieces each. In-phase emitters act as a single unit, receiving and sending a signal.
Wi-Fi router with external antenna TL-ANT2414A narrows the broadcast field to an area within the front lobe of the radiation pattern. Useful when deploying a network in an elongated stadium, the territory of the factory.
The range of the construction will be much inferior to parabolic models, the installation process, the settings are relatively simple, it is permissible to broadcast to a group of subscribers, the plates form a channel with two ends.
The power level of the antenna Wi-Fi
Each electronic product is calculated to skip the permissible power level. Exceeding the threshold allowed by the manufacturer disables the device much faster. The mode of operation is invalid. Powerful Wi-Fi antenna emits tens of watts. For comparison, the registration threshold of devices in the range is in the region of 200 mW( one fifth of one Watt).
Normal adapter works with acceptable( without registration) signal levels. Some consumers need to provide additional power requirements. We'll have to buy a special amplifier. The cost of the device is $ 500 and higher depending on the specific model.
The range of the system increases, the reception becomes more confident. Equipment is required to obtain a license. Expertise is engaged HRCHC where submit an application for research.
Laptops, mostly old models, do not support wireless networks. At times, the internal Wi-Fi antenna is unable to pick up the signal due to its poor performance.
Specially manufactured PCMCIA bus adapters. A distinctive feature of the products is the ability to connect an external antenna. Dramatically improves the quality of reception.
Why is the option good for indoor use? Increasing the length of the wire dramatically reduces effectiveness. Antenna for a Wi-Fi adapter often looks like an appendage. Rod protruding from the board. Increasing the cable length dramatically reduces sensitivity.
Sitting under the window, it is possible to place the antenna in the window, increasing the reception range.