Electronic – Is an omnidirectional antenna a must for a cell phone

antennagsm

I have read somewhere (but unfortunately I am not able to remember where) that cell phones do need an omnidirectional antenna.

If it is so, what are the reasons for that? Why a normal directional loop antenna could not be (efficiently) used ?

Best Answer

There are no antennas that are truly omnidirectional without a lot of complication especially for a cell-phone. However, if you think about it, you do want to be able to hold your handset and turn in any direction to face north, south, east or west and expect it to work. A directional loop antenna defeats the objective of being able to face any direction and still work.

You could argue that laying flat on the ground (whilst on the phone) is "not a requirement" and therefore you shouldn't expect this to work in all directions. However, the reception and transmission of radio waves is quite complex to understand (and a bit unpredictable) and these can make the "normal" expectations better or worse. Here's what a dipole's field looks like: -

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You can see that it extends in all directions horizontally the same but in the vertical direction there is no field (receiving or transmitting).

The design of the "system" also provides different frequencies for any particular handset to operate on and sometimes when reception might be poor at one frequency, moving to an adjacent frequency might make a significant improvement. Ditto for transmission.

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