Antenna technology is really being pushed to its limits with all of the different frequencies they have to accommodate in smart phones as they need to connect via multiple cellular bands, WiFi, Bluetooth and receive GPS signals not to mention the coming of mobile TV and video which may require even more frequencies. Tunable antennas seem to be the upcoming technology as a single antenna might be used for all the frequencies by changing its impedance to optimize performance at various frequencies but this can lead to other issues. Most of these tunable antenna are still in development so using the space around the phone body of the phone is an ingenious way to free up board space that would be taken up by multiple antennas. Apparently, the iPad also uses a similar approach where the antenna is the LCD frame around the screen.
One draw back (which must have been considered in the design) is that touching the antenna body will change it characteristics significantly, so I would be curious how that affected the design. There will also be people who will question the radiation being directly in contact with the skin, but I don't think there is much difference in having the antenna touch your skin versus being a few millimeters away inside the phone (the phone is now only 9.3 mm thick).
The new antenna design in the iPhone 4 could revolutionize the way in which antennas are designed in future phones and has enabled Apple to reduce the size of the phone while improving performance to solve the problem of dropped calls and poor reception. Do you think this is the future of antenna design for phones?
On another note, I noticed in the iPhone teardown of the prototype on Gizmodo showed that the Skyworks FEM is again the winner for the RF section last the previous iPhone design. That is a big win for them (I could not make out if there were any additional FEMs on the board).