Brief introduction of microwave communication technology lifting microwave antenna bracket

Microwave Communication (Microwave Communication) is Communication using electromagnetic waves with wavelength between 0.1mm and 1 m-Microwave. The frequency range corresponding to the electromagnetic wave in this wavelength range is 300 MHz(0.3 GHz)~ 3THz.

Different from the transmission modes of modern communication networks such as coaxial cable communication, optical fiber communication and satellite communication, microwave communication is a communication that directly uses microwave as a medium without solid medium, microwave transmission can be used when there is no barrier within the linear distance between two points. Using microwave for communication has the characteristics of large capacity, good quality and can be transmitted to a long distance. Therefore, it is an important means of communication in the national communication network and is generally applicable to all kinds of dedicated communication networks.

With the development of China's communication technology modernization, the digitalization and informatization construction of communication technology are becoming more and more extensive, and the research on digital microwave communication technology has also made new achievements. In modern communication technology, microwave communication plays a very important role. In recent years, microwave communication has been widely used in many fields, such as mobile communication, satellite communication, etc. The frequency of microwave is very high. Any communication in the frequency range of 300MHz to 300GHz can be called microwave communication.

Microwave communication began to be applied in real life in the middle of the 20th century. It can realize large-capacity communication, with fast construction speed, high quality, stable communication process and convenient maintenance. Due to the above advantages, this makes it an extremely frequent transmission method for current applications. Compared with optical fiber communication and satellite communication, the communication network of microwave communication is easier to establish. Even in remote areas such as mountainous areas and rural areas, microwave communication can be realized.

Microwave communication in China is widely used in L, S, C and X frequency bands, and the application of K frequency band is still under development. Because the frequency of microwave is extremely high and the wavelength is very short, its propagation characteristics in the air are similar to that of light wave, that is, straight forward, and it is reflected or blocked when it encounters blocking, therefore, the main way of microwave communication is line-of-sight communication, which needs relay forwarding after exceeding the line-of-sight. Generally speaking, due to the influence of the Earth surface and the loss of space transmission, it is necessary to set up relay stations every 50 kilometers to amplify and forward the radio waves. This communication mode is also called microwave relay communication or microwave relay communication. Long-distance microwave communication trunk lines can pass through dozens of relays to thousands of kilometers and still maintain high communication quality.

 

Frequency spectrum designation

Frequency range

Band name

Wavelength range

VLF

3 kHz~30 kHz

Ten thousand meters, very long wave

10 km~100 km

Low frequency (LF)

30 kHz~300 kHz

Kilometer wave, long wave

1 km~10 km

Intermediate frequency (MF)

300 kHz~3000 kHz

100 meter wave, medium wave

100 m~1000 m

High frequency (HF)

3 MHz~30 MHz

10 meter wave, short wave

10 m~100 m

Very high frequency (VHF)

30 MHz~300 MHz

Meter wave, ultra short wave

1 m~10 m

UHF

300 MHz~3000 MHz

Decimetre wave

10 cm~100 cm

Ultra high frequency (SHF)

3 GHz~30 GHz

Centimetre wave

1 cm~10 cm

Ultra high frequency (EHF)

30 GHz~300 GHz

Millimeter wave

1 mm~10 mm

300 GHz~3THz

Submillimeter Wave

0.1 mm~1 mm

The development of microwave is inseparable from the development of wireless communication. In 1901marconi, 800kHz medium-wave signals were used to conduct the first trans-Atlantic radio wave communication experiment in the world from Britain to Newfoundland in North America, which ushered in a new era of human wireless communication. In the early days of wireless communication, people used long wave and medium wave to communicate. In the early 1920 s, people discovered short wave communication. Until the rise of satellite communication in the 1960 s, it had always been the main means of international long-distance communication and was still very important to the current emergency and military communication.

The radio wave used for space transmission is an electromagnetic wave whose propagation speed is equal to the speed of light. Radio waves can be classified and named by frequency or wavelength. We call electromagnetic waves with frequencies higher than 300MHz microwave. Because the propagation characteristics of each band are different, it can be used in different communication systems. For example, medium wave mainly propagates along the ground and has strong diffraction ability, which is suitable for broadcasting and maritime communication. Short wave has strong ionosphere reflection capability and is suitable for global communication. The diffraction ability of ultra short wave and microwave is poor, which can be used as line-of-sight or over-line-of-sight relay communication.

In 1931, the first microwave communication circuit in the world was built between Dover, England and Calais, France. After the Second World War, microwave relay communication developed rapidly. In 1955, the test of the stratosphere scattering communication was successful in North America. Satellite communication experiments began in the 1950 s and was put into use in the mid-60s. Because the frequency resources of microwave band are extremely rich, and the spectrum below microwave band is very crowded, mobile communication is also developing towards microwave band. In addition, the development of digital technology and microelectronic technology has also promoted the gradual transition of microwave communication from analog microwave communication to digital microwave communication.

Microwave communication is the product of 1950 s. Due to its large communication capacity, low investment cost (accounting for about one fifth of the cable investment), fast construction speed, Strong disaster resistance and other advantages, it has achieved rapid development. From 1940 s to 1950 s, microwave communication with wide transmission frequency band and stable performance was produced, which became the main means of wireless transmission of long-distance and large-capacity ground trunk lines. The analog frequency modulation transmission capacity was as high as 2700 channels, it can also transmit high-quality color TV at the same time, and then gradually enter the medium capacity and even large capacity digital microwave transmission. Since the mid-1980s, with the discovery of the influence of frequency selective dispersion fading on digital microwave transmission interruption and the development of a series of adaptive fading countermeasures and high-state modulation and detection technologies, it has brought about a revolutionary change in digital microwave transmission. What should be pointed out in particular is the rapid development of a set of high-speed and multi-state adaptive coding modulation and demodulation technology, signal processing and signal detection technology developed from 1980 s to 1990 s. For today's satellite communication, signal Design and signal processing applications in many fields such as mobile communication, all-digital HDTV transmission, universal high-speed wired/wireless access, and even high-quality magnetic recording play an important role.

The proportion of microwave relay communication in foreign developed countries in long-distance communication networks is as high as 50%. According to statistics, it is 66 percent in the United States, 50 percent in Japan and 54 percent in France. Since the introduction of the first set of microwave communication equipment from East Germany in 1956, China has made great achievements through the process of imitation and spontaneous development. In the Tangshan earthquake in 1976, when the coaxial cable between Beijing and Tianjin is completely broken, all six microwave channels are safe and sound. In the worst flood of the middle and lower reaches of the Yangtze River in the 1990 s, microwave communication once again showed its great power. In today's communication revolution, microwave communication is still one of the most promising means of communication.