The antenna of mobile phones is of fundamental importance, typically with omnidirectional radiation pattern, and there are different types:
External, this was the first antenna configurations for mobile phones, characterized by the possibility to immediately see its positioning in the upper zone of the terminal and generally cylindrical in shape and in some cases telescopic.
Internal, in this situation, the antenna is not visible and can be placed in any position inside the terminal.
Device, this configuration is a particular type of external mobile phone antenna is characterized by a zero footprint comparable to internal antenna, as it plays also a function of the frame of the terminal itself, the quintessential example is the iPhone 4 and 4S.
The choice of the antenna and its location is critical to meet the criteria of reliability of the signal, since this must be efficient in any situation, avoiding the resonance caused by the contact between two different types of antennas (in the case of using multiple antennas) and so-called “hand effect” characterized by the reduction of the signal during use of the device, as the hand covers the antenna.