What is Microwave Communication

JasonYoo

What is Microwave Communication [Copy link]

Microwave communication has large capacity, good quality and can be transmitted over long distances. Therefore, it is an important communication means of the national communication network and is also widely applicable to various special communication networks.

　　In China, microwave communication widely uses L, S, C, and X frequency bands, and the application of K frequency band is still under development.

　　Due to the extremely high frequency and short wavelength of microwaves, the propagation characteristics in the air are similar to those of light waves, that is, they move in a straight line and are reflected or blocked when encountering obstacles. Therefore, the main mode of microwave communication is line-of-sight communication, and relay forwarding is required after exceeding line-of-sight.

　　Generally speaking, due to the influence of the earth's curved surface and the loss of space transmission, a relay station needs to be set up every 50 kilometers or so to amplify and forward the radio waves and extend them. This communication mode is also called microwave relay communication or microwave relay communication. Long-distance microwave communication trunk lines can be transmitted to thousands of kilometers after dozens of relays and still maintain high communication quality.

　　The equipment of the microwave station includes antennas, transceivers, modulators, multiplexing equipment, power supply equipment, automatic control equipment, etc. In order to gather the radio waves into a beam and send them to a distant place, parabolic antennas are generally used, and their focusing effect can greatly increase the transmission distance. Multiple transceivers can share an antenna without interfering with each other. In my country's current microwave system, six receivers and six transmitters can work simultaneously in the same frequency band and direction, or eight receivers and eight transmitters can work simultaneously to increase the overall capacity of the microwave circuit. Multiplexing equipment is divided into analog and digital. In the analog microwave system, each transceiver can work on 60, 960, 1800 or 2700 channels of communication, and can be used for microwave circuits of different capacity levels. Digital microwave systems use digital multiplexing equipment to form a primary group with 30 telephones according to the principle of time division multiplexing, and then form a secondary group of 120, a tertiary group of 480, and a quaternary group of 1920. They are modulated on the transmitter by a digital modulator and restored to multiple telephones at the receiving end by a digital demodulator. The latest microwave communication equipment, whose digital series standard is completely consistent with the synchronous digital series (SDH) of optical fiber communication, is called SDH microwave. This new microwave equipment can transmit more than 30,000 digital telephone circuits (2.4Gbit/s) simultaneously on one circuit with eight beams.

　　Microwave communication can be used for transmission of various telecommunication services due to its wide bandwidth and large capacity, such as telephone, telegraph, data, fax and color television, which can all be transmitted through microwave circuits. Microwave communication has good disaster resistance and is generally not affected by natural disasters such as floods, wind disasters and earthquakes. However, microwaves are easily interfered by air transmission, and the same frequency cannot be used in the same direction on the same microwave circuit. Therefore, microwave circuits must be constructed under the strict management of the radio management department. In addition, due to the characteristics of microwave rectilinear propagation, there cannot be high-rise buildings blocking the direction of the radio wave beam. Therefore, the urban planning department should consider the planning of microwave channels in urban space so that they are not blocked by high-rise buildings and affect communication.

　　In recent years, China has successfully developed a point-to-multipoint microwave communication system, in which the central station uses an omnidirectional antenna to transmit in all directions. Within 50 kilometers around, there can be multiple points where user stations are placed, and multiple telephone lines are divided from the user stations and connected to each user for use. Its overall capacity includes equipment with different capacities such as 100 lines, 500 lines and 1000 lines. Each user station can be assigned a dozen or dozens of telephone users. If necessary, it can be extended to users hundreds of kilometers away through relay stations. This point-to-multipoint microwave communication system is also very suitable for users in urban suburbs, county towns to rural towns or coastal islands, and for scattered settlements. It is relatively economical.

　　Microwave communication also has "troposphere scatter communication" and "meteor trail communication", which uses the unevenness of the upper atmosphere or the scattering effect of meteor trails on radio waves to achieve communication beyond line of sight. These systems are rarely used in China.