When it comes to wireless products, many people pay more attention to the signals of wireless products. The general AP has a theoretical coverage of 100 meters to 300 meters in an open environment, and 35 meters to 100 meters in an office environment. In fact, the theory is a little different from reality. The wireless range of an AP cannot be determined uniformly. Different products have different scopes. Everyone knows that wireless APs have antennas. The main purpose is to greatly enhance the gain of the signal and increase the transmission distance. We can often see that many products have an antenna AP and two antenna APs. Many people will doubt, in the end, one Is the antenna of the antenna transmitting a wide range of signals or is the transmission range of the two antennas wide? Is the transmission signal range of the AP of the two antennas necessarily wider than that of an antenna? With these questions, we have focused on this aspect.
Factors affecting signal coverageThe signal coverage of a wireless AP is related to many factors, in addition to environmental factors, as well as the parameters of the AP itself. Among them, the transmit power of the AP and the transmit power of the antenna are the two dominant factors, and are related to the processing and coding of the signal by the entire AP.
The AP's transmit power directly affects the signal coverage. This is also the difference between a high-priced AP and a low-priced AP. The price at which the transmit power is large will be higher. Vendors need to improve the function of the AP, mainly in the research and development of the AP's transmit power. We can take a look at this simple formula: the signal level (dB) at the input of the amplifier = device output power (dB) - cable attenuation (dB) - connector attenuation (1dB), as can be seen from this formula, the amplifier input The signal level of the terminal is directly related to the output power of the device. For example, the output of the device is 64mW (180dBm), the attenuation of the 40m LMR400 cable is 8.8dB, and the signal at the input of the power amplifier is: 18dBm-8.8dB-1dB=8.2dBm≈32mW
On the other hand, the transmit power of the antenna also affects the signal coverage. There are many standards for classification of antennas, which can be roughly divided into omnidirectional antennas and directional antennas. For the same network segment, directional antennas are generally used. For different network segments, omnidirectional antennas are used. In general, most APs currently use a dual-antenna design. It can be said that a newer AP uses a dual-antenna design. Previously produced APs have a suitable antenna design.
AP analysis with two antennasThe dual-antenna AP can improve the effective coverage. The professional Access Point will provide two high-frequency plugs, which are respectively connected to two antennas of the same type. The installation distance of the two antennas is not strict, about one meter. When transmitting a signal, the wireless component will only pass one of the plugs (the main plug), but when receiving the signal, the wireless component will select a signal noise RaTIo to receive the signal between the two antennas. Based on multi-path reflection, two antennas separated by more than one meter will have different receiving signal-to-noise ratios. If the wireless client computer transmits wireless signals to Access Point, in a complicated environment, one antenna design will also Receive direct signals and reflected signals. If the two signals have a certain degree of "inversion", the final received signal will attenuate the signal-to-noise ratio due to energy cancellation. At the same time, the antenna with one antenna design and one antenna will be used. Since there is more than one meter away from the other antenna, there may be some degree of "in-phase" when receiving direct signals and reflected signals, so that the final received signal has a better signal-to-noise ratio.
Since the wireless client computer moves around in the field, the signal sent by it is reflected by multiple channels, and the signal arriving at the Access Point must be constantly changing. Therefore, among the two antennas, there will always be different receiving signal-to-noise ratios. You can continually choose the antenna that receives the better reception to receive the wireless signal. The dual antenna setting results in an average of about 3dB of signal-to-noise ratio gain, which increases the effective coverage.
In general, the simple dipole antenna used on the AP has a gain of approximately 2.2 dBi. However, the two sets of antennas do not receive a gain of 4.4 dBi, but they can support dual antenna automatic diversity to improve the performance of the WLAN network through a special technique.
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