Microwave communication Technology

The use of microwave communication with large capacity, good quality and can be transmitted to a very long distance, it is a national communication network of an important means of communication, but also widely applicable to a variety of special communications network.

Microwave communication in China is widely used in the frequency bands of L, S, C and X, and the application of K-band is still under development.

Because the microwave frequency is extremely high, the wavelength is very short, the common in the air propagation characteristic and the light wave is similar, is also the straight forward, encounters the barrier to be reflected or is interrupted, therefore the microwave communication main way is the line-of-sight communication, surpasses the visual range to need the relay forwarding.

Generally speaking, due to the impact of the Earth's surface and the loss of space transmission, every 50 kilometers or so, you need to set up relay stations, the radio amplification and forwarding and extension. This kind of communication, also known as Microwave relay communication or microwave relay communication long-distance microwave communication trunk can be transmitted through dozens of times to thousands of km can still maintain a high quality of communication.

Microwave station equipment including antenna, receiver transmitter, modulator, multiplexing equipment and power equipment, automatic control equipment. In order to gather the wave to become beam, sent to the distance, generally using parabolic antenna, its focus can greatly increase the transmission distance. Multiple transceiver can use a single antenna without interference, China's current microwave system in the same frequency band in the same direction can have six six hair at the same time work, can also have eight receive eight hair at the same time to increase the overall capacity of the microwave circuit. Multiplexing devices have analog and digital points. Each transceiver can work in 60-, 960-, 1800-or 2700-channel communication, and can be used in microwave circuits with different capacity levels. Digital microwave System Application of digital multiplexing equipment to 30-way telephone time division multiplexing principle to form a group, then can be composed of two times Group 120 road, three times Group 480, four Times Group 1920, and after the digital modulator modulation on the transmitter, in the receiving end by the digital demodulator to restore the multi-channel telephone. The latest microwave communication equipment, its digital series standard and optical fiber communication Synchronous Digital Series (SDH) exactly consistent, called SDH Microwave. The new microwave device eight beams on one circuit can transmit 30,000 multiplex digital telephone circuits (2.4gbit/s) simultaneously.

Because of its frequency bandwidth and large capacity, microwave communication can be used in various telecommunication services, such as telephone, telegram, data, facsimile and color TV, etc. can be transmitted through microwave circuit. Microwave communication has good resilience, and the microwave communication is generally unaffected by natural disasters such as floods, wind storms and earthquakes. But microwave transmission through the air, vulnerable to interference, in the same microwave circuit can not use the same frequency in the same direction, so the microwave circuit must be in the radio management under the strict management of construction. In addition, because of the microwave line propagation characteristics, in the radio beam direction, there can be no high-rise block, so the urban Planning Department should consider the urban space Microwave channel planning, so that it can not be blocked by high-rise buildings to affect communication.

In recent years, our country has successfully developed point-to-point microwave communication system, its center station adopts omni-direction antenna to launch around, within 50 kilometers, there can be multiple points to place user station, from the user station and then separate multi-channel telephone to each user to use. Its overall capacity is 100 lines, 500 lines and 1000 lines, such as different capacity of the equipment, each user station can be allocated more than 10 or dozens of telephone users, if necessary, can also be extended through the repeater to hundreds of kilometers away from the use of users. This kind of point-to-point microwave communication system is very useful for the users of urban suburbs, county towns, rural villages or coastal islands, and for dispersed settlements.

Microwave communication also has "tropospheric scattering communication", "Meteor trace communication" and so on, is the use of the high atmosphere of the uneven or meteor traces of the waves to the scattering of the radio wave to reach beyond the visual range of communication, these systems, the application in China is less.