transmission distance

We often buy a wireless router in the Internet, the product specification will be similar to the following description: "the transmission distance of the farthest indoor 100/200 meters; outdoor far 300/800 meters (environmental factors have influence on the distance); RF power 17dBm (typ), 3dBi antenna gain, antenna type dipole antenna" these instructions, explain exactly what they mean?

In fact, the various manufacturers in the WLAN wireless equipment distance marked not identical, consumer radio equipment power (RF power) is constant, may not exceed the standard infinite, although some products nominal transmission distance of 200 meters farthest indoor and outdoor 830 meters farthest (varies with the environment), but the actual distance in the case of the standard equipment is difficult to reach the distance.

Because the transmission distance, medium or other factors (such as weather) will cause the loss of a radio signal, wired and wireless network are the signal attenuation, compared with wired network, wireless LAN technology for transmission in the air, influenced by the environment more, with the increase of distance or obstacle signal will decline. The actual transmission distance is often less than the maximum limit, especially in many indoor obstacles, frequent use of electrical equipment, which greatly shorten the distance.

So we think that the range of WLAN to cover the open environment should be considered or not, without the external antenna, in view of about 300 meters; in the case of semi open space (regional partition, thin wall blocking), can reach 35 ~ 50 meters. Of course, if plus external antenna, distance can be further, this is related to the gain of the antenna itself (the gain of the antenna is used to measure the ability of the antenna in a specified direction receiving signal it is one of the most important parameters of wireless antenna selection), so for the customer demand and decide.

antenna

In addition, the use of wireless equipment antenna wire length, material (the current trend is the use of printed antenna, printed on the card or on the Tag and to replace the aluminum copper alloy as the material of the antenna, in order to improve the sensitivity of impedance matching (), the input impedance of the antenna is the antenna feed ratio of input voltage and input current the.

Connect the antenna and feeder, the best case is the input impedance of the antenna is pure resistance and is equal to the characteristic impedance of the feeder, the feeder terminal has no power reflection, not standing on the feeder, the input impedance of the antenna with frequency changes gently) and polarization (electric field intensity direction of the antenna polarization, the so-called refers to the antenna radiation. When the direction of the electric field is perpendicular to the ground, the wave is called a vertical polarized wave. When the electric field intensity is parallel to the ground, the wave is called a horizontal polarized wave.

At present there has been dual polarization / dipole antenna, generally divided into vertical and horizontal polarization and polarization of plus or minus 45 degrees in two ways, the general performance of the latter than the former, so most of the current use is plus or minus 45 degree polarization) will affect the signal, but the most obvious is the gain attenuation. Usually 20 feet in length, the signal will be attenuated by about 1.2dBi, while the average attenuation of 8dBi will make the original transmission distance is reduced by about half.