[ Huaqiang Security Network News ] In the development of infrared waterproof cameras, video anti-jamming devices have an irreplaceable role. 
Since the transmission mode of the infrared camera has the advantage that the transmission system has a simple structure, but the transmission distance cannot be too far, the infrared smart ball must be transmitted within the range required by the cable characteristics, and one video coaxial cable can only transmit at the same time. All the way to the TV signal.
Because this transmission mode has high stability to the infrared waterproof camera, the equipment used in the system is simple, and the wiring is convenient, and thus has been widely used in real life. However, the use of high bandwidth and low frequency of the cable causes the amplitude and phase of the signal to be transmitted in the cable to be very different between the low frequency band and the high frequency band, especially when the phase distortion is too large. The circuit is compensated. And the low frequency part of the baseband transmission is easily interfered by interference sources such as strong electricity, transmission towers, base stations, motors, and inverters. For example, common sources of interference for infrared waterproof cameras:
1. Broadcast interference:
When the cable is erected in the air, the cable itself is equivalent to a long antenna. As a result of the antenna effect, a considerable amount of broadcast interference voltage is generated in the cable, and an interference current is generated on the cable sheath. This current forms a loop through the grounding point at both ends of the cable and the ground, so that broadcast interference occurs at the terminal load. The voltage of the signal causes the interfering signal to mix into the video signal. This kind of interference signal appears as dense horizontal stripes, vertical stripes, twill, etc. on the image, and even floods the entire video image in severe cases.
2, high frequency interference:
The cable shield has a poorer shielding effect on signals with lower frequencies. The high-frequency interference signals introduced for this reason include carrier phones, radio signals, and the like. They cause horizontal streaks on the image.
3. Power interference:
When the system needs to be grounded at the same time as the beginning and end, due to the different ground potentials at both ends and the presence of the cable sheath resistance, a ground potential difference of 50 Hz is caused between the two places, thereby generating an interference signal voltage. When the interference signal is superimposed on the video signal, a wide horizontal dark band or the like appears on the normal image.
4, harmonic interference:
Harmonic interference is mainly manifested around a high-current or high-voltage power line. It is a radiation signal to the surrounding of the power cable. Its frequency is 2500 Hz and 125000 Hz, which mainly interferes with the low frequency band of the video signal.
5. Transmission line interference:
The quality of the video cable is not good, the shielding performance is poor (the shielding layer is sparse or the non-copper dielectric shielding layer, etc.), the cable resistance is too large, and the video signal is seriously attenuated.
6, unclean power interference:
For example, the power grid has high-power thyristor frequency modulation speed regulation device, thyristor rectifier device, thyristor AC/DC converter device, etc., which will pollute the power supply. Unclean power sources can make cameras and other active devices unstable, creating interference.
The above parts make the video image on the scene subject to strong interference. We can use the video anti-jamming device to solve the common interference sources above the infrared waterproof camera. The specific solution is as follows:
1. Frequency shift: The frequency signal is used to shift the video signal (0-6MHZ) to a range of 49-300MHZ; the video signal is transmitted remotely through the anti-jamming transmitter, and the signal is restored to the normal video at the receiving end. Signal output. Due to the increased frequency, a variety of interference signals are effectively avoided while transmitting over long distances;
2. Encoding: After the video signal enters the anti-jamming device, it is digitally encoded and processed before reaching the monitoring center device. Thereby avoiding interference of the interference source with the video signal and crosstalk and attenuation of the video signal itself;
3. Enhancement: Since the signal transmission distance is larger, the signal attenuation is larger, so we must strengthen the signal carrier capability at the transmitting end so that it can transmit farther;
4. Adaptive: The device automatically adjusts and adapts the signal strength, so the device has the automatic adaptability of transmission from 0 to its longest distance;
5, free of debugging: a good device should not have a lot of debugging parts, so our equipment has 90% market adaptability at the factory, basically it can be used on the connection, no need for redundant debugging;
6. Safety: The design concept of wide voltage (12V-24V) avoids the sudden increase or sudden drop of the power supply voltage to protect the equipment and the safety of the operator.
Summary: Take advantage of the relationship between them, the development space of infrared cameras should be huge.
Because this transmission mode has high stability to the infrared waterproof camera, the equipment used in the system is simple, and the wiring is convenient, and thus has been widely used in real life. However, the use of high bandwidth and low frequency of the cable causes the amplitude and phase of the signal to be transmitted in the cable to be very different between the low frequency band and the high frequency band, especially when the phase distortion is too large. The circuit is compensated. And the low frequency part of the baseband transmission is easily interfered by interference sources such as strong electricity, transmission towers, base stations, motors, and inverters. For example, common sources of interference for infrared waterproof cameras:
1. Broadcast interference:
When the cable is erected in the air, the cable itself is equivalent to a long antenna. As a result of the antenna effect, a considerable amount of broadcast interference voltage is generated in the cable, and an interference current is generated on the cable sheath. This current forms a loop through the grounding point at both ends of the cable and the ground, so that broadcast interference occurs at the terminal load. The voltage of the signal causes the interfering signal to mix into the video signal. This kind of interference signal appears as dense horizontal stripes, vertical stripes, twill, etc. on the image, and even floods the entire video image in severe cases.
2, high frequency interference:
The cable shield has a poorer shielding effect on signals with lower frequencies. The high-frequency interference signals introduced for this reason include carrier phones, radio signals, and the like. They cause horizontal streaks on the image.
3. Power interference:
When the system needs to be grounded at the same time as the beginning and end, due to the different ground potentials at both ends and the presence of the cable sheath resistance, a ground potential difference of 50 Hz is caused between the two places, thereby generating an interference signal voltage. When the interference signal is superimposed on the video signal, a wide horizontal dark band or the like appears on the normal image.
4, harmonic interference:
Harmonic interference is mainly manifested around a high-current or high-voltage power line. It is a radiation signal to the surrounding of the power cable. Its frequency is 2500 Hz and 125000 Hz, which mainly interferes with the low frequency band of the video signal.
5. Transmission line interference:
The quality of the video cable is not good, the shielding performance is poor (the shielding layer is sparse or the non-copper dielectric shielding layer, etc.), the cable resistance is too large, and the video signal is seriously attenuated.
6, unclean power interference:
For example, the power grid has high-power thyristor frequency modulation speed regulation device, thyristor rectifier device, thyristor AC/DC converter device, etc., which will pollute the power supply. Unclean power sources can make cameras and other active devices unstable, creating interference.
The above parts make the video image on the scene subject to strong interference. We can use the video anti-jamming device to solve the common interference sources above the infrared waterproof camera. The specific solution is as follows:
1. Frequency shift: The frequency signal is used to shift the video signal (0-6MHZ) to a range of 49-300MHZ; the video signal is transmitted remotely through the anti-jamming transmitter, and the signal is restored to the normal video at the receiving end. Signal output. Due to the increased frequency, a variety of interference signals are effectively avoided while transmitting over long distances;
2. Encoding: After the video signal enters the anti-jamming device, it is digitally encoded and processed before reaching the monitoring center device. Thereby avoiding interference of the interference source with the video signal and crosstalk and attenuation of the video signal itself;
3. Enhancement: Since the signal transmission distance is larger, the signal attenuation is larger, so we must strengthen the signal carrier capability at the transmitting end so that it can transmit farther;
4. Adaptive: The device automatically adjusts and adapts the signal strength, so the device has the automatic adaptability of transmission from 0 to its longest distance;
5, free of debugging: a good device should not have a lot of debugging parts, so our equipment has 90% market adaptability at the factory, basically it can be used on the connection, no need for redundant debugging;
6. Safety: The design concept of wide voltage (12V-24V) avoids the sudden increase or sudden drop of the power supply voltage to protect the equipment and the safety of the operator.
Summary: Take advantage of the relationship between them, the development space of infrared cameras should be huge.
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