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kb.jayadev
2010-11-12, 05:26 PM
hai, I am new to this industry. I would like to know what is the structure inside a gsm antenna. any picture representation? can somebody help?

s52d
2010-11-12, 05:52 PM
hai, I am new to this industry. I would like to know what is the structure inside a gsm antenna. any picture representation? can somebody help?

In case of base station antennas:

Sorry, no picture...
It is array of dipoles. In fact, two antennas, +45,-45 degrees polarisation.
Metal backplane acts as relector, so each dipole has directivity in one direction.

There is a lot of wires feeding dipole structure - some antennas has
varibale downtilt made by proper variable phasing of dipoles.

Quite often, there are 4 antennas: two for 900 MHz, and two for 1800 and 2100 MHz.
1.8&2.1 GHz dipoles are quite fat in order to get proper bandwith.

We waited till first 900/1800/2100 with variable tilt antenna failed, then
we cut it into two. Perfect tool to teach antennas composed of groups.

Terminals use patch antennas, quite funny structures to cover wide selection
of frequencies.

BR
s52d

tremalnike
2010-11-12, 07:56 PM
Take a look here (http://www.sdrforum.org/pages/sdr05/5.4%20Reconfigurable%20Antenna/5.4-01%20Yun%20et%20al.pdf) . Picture of antenna-chip is inside pdf