3. Cell phone antennas

Since the advent of mobile telephony, antennas have come a long way. The first devices on the market were equipped with imposing external antennas, slowly replaced by whip antennas, then helical antennas protected by a plastic chassis or molded in rubber.

Integrating the antenna inside the phone imposes certain constraints on the placement of the antenna on the PCB. In particular, it requires a large opening in the phone's ground plane, as well as the removal of components with high metal content (chassis, vibrator, battery).

In the literature, we find various types of antenna, the most popular of which are IFA-type antennas, partially short-circuited with meanders, slots, capacitive loading, parasitic elements to increase bandwidth, and sometimes even matching circuits.

Many small antennas seem to exceed the fundamental...