Radiation Characteristics of Antenna Structures in Clamshell-Type Phones in Wide Frequency Range

In this paper, the radiation and resonance characteristics of open and closed position clamshell-type phone structures are studied at wide frequency range (from 0.6 GHz to 3 GHz) with help of coupling elements. In the closed position of the phone, the lambda/2 resonance of the chassis located close to the operating band of E-GSM900 system shows to be problematic due to low bandwidth potential and a radiation efficiency minimum. To improve the closed position performance of the antenna structure, a novel frequency tunable matching circuitry is proposed and studied with simulations. The results of this paper provide useful and novel information for the designers of antennas for clamshell-type phones. The findings of this paper can be also applied with traditional self-resonant antennas.