Thursday, 17 December 2020

Microwave technology


Microwave technology, microwave communication is a communication that uses electromagnetic waves with a wavelength between 0.1 mm and 1 meter. Microwave communication does not require a solid medium, and microwave transmission can be used when the distance between two points is unobstructed.


Use microwave technology

The use of a microwave to connect has great capacity, good quality, and can be transported over long distances. Therefore, it is an important communication medium for the national telecom network, and it is generally applicable to various communication networks.


In China, microwave communications are widely used in the L, S, C, and X frequency bands, and the application of the K band is still under development.


Since the frequency of microwaves is very high and the wavelength is very short, the properties of its propagation in the air are similar to that of the light wave, that is, it is straight forward, and is reflected or blocked when it encounters blocking.


The style of microwave technology

Therefore, the main method of communication with a microwave is line-of-sight communication, and the LOS relay bypass is required. In general, due to the effect of the isolated surface of the earth and the loss of space transmission, it is necessary to establish a relay station every 50 km or so to extend and extend the electric wave.


This type of communication, also known as microwave relay connections or microwave relay connections. Long-range microwave communication trunks can be transported thousands of kilometers after dozens of relays to maintain high communication quality.


The microwave station equipment includes an antenna, transmitter, receiver, rectifier, multiplexer, power supply device, automatic controller, and the like.


In order to collect the electric waves in a beam and send them to a distant place, a parabolic antenna is generally used, and the focus effect can greatly increase the transmission distance.


Multiple transmitters and receivers can use one antenna together without interference.


In China, the current microwave system can work with six receivers and six transmitters in the same direction in the same frequency range, or eight transmitters can operate simultaneously to increase the overall capacity of the microwave circuit.


Multiplexers are available in analog and digital. Analog microwave system Each transmitter/receiver can operate on 60, 960, 1800, or 2700 channels and can be used for microwave circuits of different amplitude levels.


The digital microwave system uses digital multiplexing equipment to form a group through the three-way telephone according to the principle of time-division multiplexing, and then it can form a second group of 120 channels, the third group of 480 channels, and a three-way group of 1920 channels, which is formed by the digital modulator On the transmitter.


At the receiving end, the digital demodulator is restored to a multi-channel phone. The latest microwave communication equipment, the digital chain standard is exactly the same as the synchronous digital chain (SDH) for optical fiber communication, called the SDH microwave.


This new microwave device can transmit more than 30,000 digital telephone circuits (2.4 Gb / s) simultaneously on a single circuit.


Due to the wide bandwidth and large capacity, microwave communication can be used to transmit various communication services, such as telephone, telegraph, data, fax, and color television, which can be transmitted via microwave circuits. Communication microwave has good disaster resistance.


The microwave connection is generally unaffected by natural disasters such as floods, windstorms, and earthquakes. However, microwaves travel through the air and are subject to interference. The same frequency cannot be used in the same direction on the same microwave circuit.


Therefore, the microwave circuit should be established under the strict management of the radio management department. In addition, due to the linear diffusion characteristics of the microwaves, there should not be any significant blockage in the direction of the beam.


Therefore, the urban planning department should consider planning the urban microwave satellite channel so that it is not affected by high building barriers and affects communication.



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