antenna-theory.com

[Xyldor]

If you have a piece of equipment (say a mobile phone) which incorporates a PIFA antenna, is it possible to incorporate the equipment into the position of the driver dipoles on a Yagi-Uda antenna in such a way as to make the phones response more directional but with a higher gain.
Assume the Yagi-Uda is designed for the correct phone frequency.

If so, would the distances between the directors and reflector dipoles remain the same as a standard Yagi-uda, or would the distances change to accomodate the different geometry of the PIFA ? How would this be calculated?

These questions were prompted by frequently experiencing areas with no or low mobile phone signal and wondering if there was a method of passively boosting the signal without modifying the phones internal antenna system. I note that loop antenna have been used sucessfully with yagi type directors and reflectors so I wonder if other types of antenna can be used too.

[E Kafeman]

A cellphone GSM antenna is often designed as a misshaped dipole antenna with less well defined polarization. It is a dipole, created by the the internal antenna as one pole and its internal ground as the other pole.

It is maybe possible to improve reception by using a phone as dipole element in a Yagi-antenna but it would require some experimenting to find out best orientation, and no external wires or hands around phone as it will make the dipole even less defined and it would still not be as good result as connecting an Yagi antenna to the phone with a coax cable.

A somewhat less complicated antenna improvement, is a corner antenna.
Very simple antenna design but can result in good improvement of received signal. Place phone in front of the reflector and adjust distance from corner until max signal is found.

Most modern cellphones have weaker GSM antennas then older phones and have no connector for external antenna-> Get hold of something old with a real antenna connector for an external antenna, for the rural situations.