I know bluetooth works in a 10/20meters range and Bluetooth 2 in a
100meters range. I would like to know if it's possible to modify the
range to and limit it at 3meters or 5meters. What range it is possible
to get ? Is it also possible to send the signal in a specific
direction (like a cone) ?

thanks

Bluetooth works in a circular direction.

Your question has a number of misunderstandings in it.  Ranges are
based on which class (power level) of bluetooth you choose.  Radiation
pattern has nothing to do witht he Bluetooth standard.  Also, sorry
rickyattri, Bluetooth does NOT work in a circular direction.
Directionality in radio communications is based on antenna
characteristics, not protocol.

Bluetooth is a wireless data communications protocol - that is, it is
a set of rules by which two participants exchange information.   The
information is exchanged through a data encoding scheme and a physical
encoding scheme (ie voltages, timings, power levels).

The Bluetooth standard allows for three different power levels, which
are denoted as Class 3, 2 and 1.  Class 3 has a dBm (1 mW) power spec,
, Class 2 is 4 dBm (2.5 mW), and Class 1 is 20 dBm (100 mW).  Most
designs are obsessed with range, so Class 1 is most common (typically
about 100 metres). Class 2 is also common - offering about 10 metres
of range.

Class 3 is rarely explored, but is of interest for very short range
(RFID like) applicaations.  Hence, RFID's or another protocol based on
near-field magnetics can be used too.


Particular radiation patterns are totally independant of the protocol,
so with a smart antenna designer and enough money you can get almost
any radiation pattern you want.

Hope that helps,

RossGK