What is the principle of wireless transmission digital microwave transmission?

1. Principle of simulated microwave transmission

Analog microwave transmission is to directly modulate the first signal on the microwave channel (microwave transmitter, HD-630), through the antenna (HD-1300LXB) to transmit, the monitoring center receives the microwave signal through the antenna, and then through the microwave receiver (microsat 600am) to demodulate the original ** signal. If you need to control the PTZ lens, add the corresponding command control transmitter (HD-2050) in the monitoring center, and configure the corresponding command receiver (HD-2060) at the front end of the monitoring.

It is not used in many cases. Its weaknesses are: poor anti-interference ability, susceptible to the influence of weather and surrounding environment, limited transmission distance, and has been gradually replaced by digital microwave, COFDM, 3G, CDMA, etc.

Second, the principle of digital microwave transmission:

Compression (HD-6001D), and then through digital microwave (HD-9500) channel modulation, and then transmitted through the antenna, the receiving end is the opposite, the antenna receives the signal, microwave deexpansion, decompression, and finally restores the analog signal, can also be microwave deexpansion through the computer to install the corresponding decoding software, with the computer soft decompression, and the computer also supports video, playback, management, cloud mirror control, alarm control and other functions; Storage servers, with disk arrays.

Storage; This monitoring method has a resolution of *288 or higher to choose from, and there is a delay of about seconds through the decoded storage method. The digital monitoring price varies greatly according to the actual situation, but there are also some advantages that analog microwave is not comparable, such as more monitoring points, the environment is more complex, there are many cases that need to be relayed, the monitoring point is more concentrated, it can be transmitted in a centralized manner, and the anti-interference ability is a little better than the analog one, and so on.

Digital microwave transmission is to first encode and compress (HD-6001D), and then modulate through the digital microwave (HD-9500) channel, and then transmit it through the antenna, the receiving end is the opposite, the antenna receives the signal, microwave deexpansion, decompression, and finally restores the analog signal, you can also install the corresponding decoding software through the computer after microwave deexpansion, and use the computer to decompress softly, and the computer also supports video, playback, management, cloud mirror control, alarm control and other functions; storage servers, with disk array storage; This monitoring method has a resolution of *288 or higher to choose from, and there is a delay of about seconds through the decoded storage method. The digital monitoring price varies greatly according to the actual situation, but there are also some advantages that analog microwave cannot be compared, such as more monitoring points, more complex environments, more cases that need to be relayed, more concentrated monitoring points, it can be transmitted in a centralized manner, and the anti-interference ability is a little better than the analog one, and so on.

Please refer to it. Thank you.

In the frequency band above 100MHz, radio waves travel in a straight line almost in a straight line, so they can be clustered into a narrow bundle. With a parabolic antenna, all the high energy can be concentrated in a small beam, resulting in an extremely high signal-to-noise ratio, but the antennas at the transmitter and receiver must be precisely aligned with each other. Moreover, this directivity also allows multiple transmitters in a row to communicate with multiple receivers in a row, as long as their spatial rows are regular, and they do not interfere with each other.

MCI has built its entire system with microwave communication technology, and it has built many microwave towers, each tens of kilometers apart.

Since microwaves travel in a straight line, if the two towers are too far apart, the Earth itself will block the path. Therefore, a repeater is needed at intervals in between. The higher the tower, the farther the microwave can go.

The distance between the repeaters is roughly proportional to the square root of the trespass.

Unlike low-frequency wireless telegraphy, microwaves do not penetrate buildings very well. And, even if the microwaves have gathered at the point of launch, there will still be some divergence in the air. Under certain conditions, the effect of path attenuation will occur.

In summary, microwave communications are widely used in long-distance communications, mobile, television broadcasting, and other applications where there is a severe shortage of spectrum. It has several important advantages over fiber optics. The main advantage is that there is no need for the right of way.

And microwaves are relatively cheap, such as building two simple towers is easy.

The transmission process is generally generated by the transmitting equipment and converted into electromagnetic waves by the transmitting antenna, which is propagated to the receiving end through the space medium, and the electromagnetic waves are received by the receiving antenna and restored into electrical signals to complete the transmission.

Direct wave propagation (line-of-sight propagation): Generally used in the ultra-short wave and microwave bands. Direct wave propagation is the most important mode of radio wave propagation.

Ionospheric reflected wave propagation (skywave propagation): refers to the propagation mode of radio waves radiating to the sky and returning to the ground after being reflected by the ionosphere, mainly used in the medium wave and short wave bands, referred to as sky waves.

Surface wave propagation: This is a type of electromagnetic wave that travels along the earth's surface, referred to as ground wave. It is mainly used in the medium and long wave bands and the low frequency bands of short waves.

Since the earth absorbs the energy of radio waves, it is possible to use ground waves as a propagation method that can only communicate in close proximity at a lower frequency band.

Scattered wave propagation: This propagation is mainly due to the scattering of electromagnetic waves when they are projected onto an inhomogeneous air mass in the atmosphere (such as the troposphere) or onto the aftermath of a meteor, and a portion of the electromagnetic wave reaches the receiving site.

Ground Reflection Wave Propagation: The propagation mode in which radio waves are reflected from the ground to the receiving location.

Straight-line transmission. If the distance is long, a relay station can be added to the transmission line for relay transmission.

Waves refer to electromagnetic waves with a frequency of more than 1 GHz, with wavelengths in the order of millimeters and centimeters, and their wavelengths are shorter than ordinary radio waves. Wireless microwave transmission is similar to the linear transmission of light, which is a relay transmission within the line-of-sight range. It has the characteristics of linear transmission and multipath transmission within the line-of-sight range, and wireless microwave transmission is divided into:

Analog microwave transmission and digital microwave transmission.

"Microwave" usually refers to electromagnetic waves with a wavelength of m1-mm1, and the corresponding frequency range is: MHz300-GHz300, which is between radio waves and infrared, and can be divided into decimeter waves, centimeter waves, millimeter waves, and submillimeter waves. Microwaves, like low-frequency electromagnetic waves, have all the characteristics of electromagnetic waves, but because of the short wavelength and high frequency of microwaves, they have many unique properties, which are mainly manifested in:

1. Description method: because the wavelength of electromagnetic waves is extremely short, the size of the components and equipment used can be compared, and the propagation nature of the energy concentration in the low frequency band is described by the concept of "road", and the components used are called concentrated parameter elements (resistance, capacitance, inductance, etc.); The propagation of microwaves should be handled using the concept of "field", and the elements used are distributed parameter elements (waveguides, resonators, etc.). Therefore, the current, voltage, resistance, etc. of low-frequency circuits are no longer applicable, but are treated by equivalent methods; Microwave measurements replace current, voltage, resistance, etc., with power, wavelength, and impedance.

2. Generation method: The period of microwave is 910 - s1210 and the transition time of electrons in the tube (about s910) is similar, so the generation and amplification of microwave can no longer use ordinary electronic devices, but are completely different structures and principles of microelectronic components - klystron, magnetron, traveling wave tube and microwave solid-state devices.

3. Optical similarity: Since microwaves are between radio waves and infrared rays, they not only have the properties of radio waves but also have the properties of light waves: linear propagation at the speed of light, reflection, refraction, interference, diffraction, etc.

4. Strong energy: due to the high frequency of microwaves, the available frequency bandwidth, large information capacity, and can penetrate the atmosphere, so it can be widely used in satellite communications, satellite radio and television, space communications and astronomy research. Due to these characteristics of microwaves, microwaves are widely used in communications, radar, navigation, remote sensing, astronomy, meteorology, industry, agriculture, medical treatment, and medicine.