Help to understand/ explore small sized 3G and GPS Antenna Design
These things are all PIFA (planar inverted F) antennas.  They all perform exactly the same, though they have to be carefully designed to fit into the enclosure and have the correct resonances.  The basic idea is to add cuts in such a way that the path the current takes through the antenna cause it to resonate at a lower frequency than the overall size would normally allow.  This is called electrical lengthening.  It results in a low efficiency, low gain, but compact antenna.  They are designed with EM simulation software, and they have to model not only the antenna but also the circuit boards and case as they sit in the antenna near field and affect the performance.  The antennas themselves are simply pressed out of metal, but they have to get the precise shape figured out in simulation and probably have to go through a few rounds of prototypes to get it working correctly.