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for underground stations micro or pico Base transceiver Station (BTS) can be used.
For coverage along a railway undeground there is a solution using "leaky feeders" which is a special kind of RF feeder (like the one used between the TRX and antenna) but with apertures or slots along the length such that it radiates power in the process. Usually this solution comes complete with repeaters and fiber optic distribution systems for the transmission.
in general, leaky waveguides is used in these situations. one of them is leaky cables, but i think leaky circular and leaky rectangular waveguides are also suitable, but it is depend on the frequency used. for GSM900, they are big, so leaky cables are used.
leakage is via slots on the waveguide wich excite a magnetic curent on the slot, and radiate as a simple slot antenna, which could be refered to in any standard antenna handbook. the array is assumed to have a uniform excitation, which depends on the slots, and becouse of small apertures generally used, the whole antenna could be used in a long distance without repeaters (but adjastments is neede).
some methods is used to enhance the performance of the antenna, such as using screwed apertures, or zigzag apertures.
I think you should find literature on the subject on the RFS site mentioned above. Also try searching for "Radiating cable", "Leaky feeders" & "Radiating-mode cable"
In my country operator uses directional antenna positioned towards tunnel . It is works up to some extend . But mainly it is not hard to get in touch when tunnel length is about few kms .
Radiating cables must be much more expensive than single directional antenna
in fact ,the most chepaer is to use the repeater to solve the coverage of the railway,the syatem as the following accessory!
the repater is the two-ways amplifier like the satelliate transponder!
Dear all,
do you have any experience in using leaky cable for mobile satellite communication.
RF Power Output: 400 mW maximum (+26 dBm)
Frequency Range: Globalstar Reverse Link: 1610.73 to 1625.49 MHz
Globalstar Forward Link: 2484.39 to 2499.15 MHz
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