L-band signal refers to satellite downlink signal (C-band: 37GHz~4.2GHz, Ku band: 1225GHz~12. 75GHZ) is the satellite signal output after the frequency reduction processing of the LNB. Its frequency is 950MHz~2150MHz, which is characterized by high frequency and wide bandwidth.There are two transmission modes of L-band signal: cable transmission and optical fiber transmission.[2]
transmission mode
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Cable transmission mode
The cable transmission mode of L-band signal is the most traditional transmission mode, which is also used by most satellite receiving systems, that is, the satellite tuner (LNB) is directly connected to the satellite receiver by coaxial cable.If multiple satellites receive different programs on the same satellite, connect the power divider in front of the satellite receiver.If the antenna is far from the satellite machine room, it must be connected behind the LNBLinear amplifier( LNA)。The high frequency attenuation characteristics of the cable determine that the L-band signal transmitted through the cable should not exceed 100 meters using a thick cable above RG11.
In the L-band signal cable transmission mode, the power supply of the tuner is provided by the satellite receiver.This power supply mode is easy to damage the receiver in the computer room due to surge lightning stroke, and also easy to cause LNB not to work due to the failure of the power supply receiver.
Optical transmission mode
The optical transmission mode of L-band signal is a new type of L-band satellite signal transmission mode commonly used by large satellite receiving systems.Its core technology is to directly modulate L-band signals into optical signals, replace some of the original cables with optical fibers, and use the characteristics of low transmission loss and no distortion of optical signals in optical fibers to transmit L-band signals to places hundreds of meters to tens of kilometers in high quality, greatly expanding the application range of L-BAND signals.The scheme is to use the shortest coaxial cable as far as possible to concentrate the L-band signals of different receiving antennas to a certain place, then directly modulate these concentrated L-band signals to the optical signals, and send the modulated L-band signals to the required places using multimode or single-mode optical fibers.Optical fiber transmission is free from electromagnetic, lightning and other interference. The direct optical modulation makes the phase distortion of the signal almost negligible, the group delay is greatly reduced, the bit error rate of the signal is reduced, the stability, security and reliability of the system are improved, and the cost of the system is also greatly increased[2]。
IEEE Standard for L-Band
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Terrestrial digital audio broadcasting (T-DAB)
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center frequency
LA
1452.960 MHz
LB
1454.672 MHz
LC
1456.384 MHz
LD
1458.096 MHz
LE
1459.808 MHz
LF
1461.520 MHz
LG
1463.232 MHz
LH
1464.944 MHz
LI
1466.656 MHz
LJ
1468.368 MHz
LK
1470.080 MHz
LL
1471.792 MHz
LM
1473.504 MHz
LN
1475.216 MHz
LO
1476.928 MHz
LP
1478.640 MHz
Satellite Digital Audio Broadcasting (S-DAB)
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center frequency
LQ
1480.352 MHz
LR
1482.064 MHz
LS
1483.776 MHz
LT
1485.488 MHz
LU
1487.200 MHz
LV
1488.912 MHz
LW
1490.624 MHz
Infrared astronomy
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stayInfrared astronomyIn the field, L-band is a kind of infrared window, with a wavelength of about 3.5 μ m, belonging to mid infrared window.
