Basic Knowledge of Antenna

A long-term transmission line of the antenna

In the case of high frequency, when the electromagnetic wave transmits along the transmission line, since the wavelength of the electromagnetic wave is very short, then the different phenomena with the transmission of audio signals will occur on the transmission line of lte antenna. When the wavelength of the electromagnetic wave propagating along the transmission line can be compared with the geometric length of the transmission line, the transmission line typically refers to the long line.



The characteristics of long line antenna

First, the current and voltage are distributed unevenly on the long line: use a transmission line with a length of 10 m, when the high-frequency current passing through line, such as F = 150MHz. (Wavelength) = 2 m, due to the shorter wavelength, there are several changes in the cycle in this transmission line current. Second, long line is a distributed parameter system: for the long line, with the different length of the transmission line or the different wavelengths, distributed capacitance and inductance parameters are distributes on the transmission line. While in the case of long line, with the difference in line length or wavelengths, the transmission line will exhibit a different nature of the impedance (capacitance, inductance or pure resistance), while the short line only has an electric field in the capacitor and the coil.

The Open-ended transmission line

When the transmission line receives the signal, the electric signal will be transmitted at the speed of light and by the cosine distribution law to the terminal. Due to open termination, signals cannot be transmitted forward continuously, and forms the total reflection to the direction of the starting end, which is equivalent to access a signal source to the transmission line terminal so that electrical signals travel from the terminal to the end at the speed of light. In general, the waves transmit from the beginning to the end of the terminal are called incident wave, and the waves reflected back from the terminal are called reflected wave. Both incident and reflected waves in the wifi panel antenna are traveling waves, which means the voltage and current are the same.

Terminal short-circuited transmission line

The terminal short-circuited transmission line is totally different from the open-end of the transmission line, it's VSWR characteristics is that the incident current and the reflected wave current are the same, while the opposite phase of the incident voltage and the reflected voltage wave. Its impedance is less than a quarter-wavelength transmission line, equal to a quarter of wavelength, and reactance is zero when it is equal to the half wavelength.

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Analysis of WiFi Antenna

Introduction of WiFi and WiFi Antenna

WiFi is widely used in our daily life, because the rapid development of wireless networks at present, antenna and its applications are getting better and better. WiFi make use of a short-range wireless transmission technology. When you come to a coffee shop, or even a restaurant, you can also find the WIFI logo. The wifi antenna are often used in these places. The WiFi antenna has different shapes, sizes and materials, and the specific process of the WiFi antenna. Compare the performance of WiFi antenna with the antenna system. The computer does not have an internal wireless network to connect to a wireless network, when we need to use an external antenna. Without this antenna, computer users cannot connect his own computer to the modem to access the Internet by using a network cable. If your computer does not have built-in WiFi antenna, then you must install an external WiFi antenna to your computer.


The Advantages of WIFI Panel Antenna

There are many various kinds of WiFi antenna in the market. A wifi panel antenna is a parabolic reflector, the parabolic cross-sectional shape of the curved surface, in order to direct the radio wave, antenna is established. The most common type of shaped like a dish is commonly known as a dish antenna or parabolic. The main advantage of the panel antenna is that it has a high directivity, the narrowest beam width. These provide some of the highest gains, and they may be generated. There must be much larger than the wavelength of the radio waves being used in order to obtain a narrower beam width, panel reflector, so the use of the radio spectrum in the panel antenna is frequent portion in the UHF and microwave. As a panel antenna, high-gain antenna has the point-to-point communications, in the application, such as a microwave relay link, telephone and television signals, wireless WAN / LAN connections for data communications, satellite communications and spacecraft communications antenna near the cities. They can also be used in the radio telescope.

Other Usages of WiFi Antenna

With the development of home satellite television channels, panel antenna has become a common feature in the landscape of the modern state. The extensive use WiFi antenna becomes also more and more popular, where there is a need to transmit radio waves in to the extremely narrow beam positioning objects, such as ships, aircraft and missiles.

This article is come from: http://www.storage-battery.com/index.php/analysis-of-wifi-antenna.htm