Internal wireless wide area network clamshell mobile phone antenna with reduced ground plane effects

An internal wireless wide area network (WWAN) antenna applied in a clamshell mobile phone having an equivalent band‐stop circuit at the hinge to decrease the upper ground plane effects of the mobile phone on the antenna performances is presented. The internal WWAN antenna in this study is a small‐size printed monopole mounted at the bottom of the main ground. This band‐stop circuit can perform a parallel resonance at around 900 MHz and leads to high impedance seen into the upper ground in the 900 MHz band, which greatly decreases the excited surface currents on the upper ground. At around 1900 MHz, owing to its shorter wavelength, the surface currents on the upper ground excited by the internal antenna on the main ground are small for both the traditional and proposed clamshell mobile phone structures. Hence, over the WWAN operating bands, the presence of the upper ground shows very small effects on the impedance matching and radiation characteristics of the antenna on the main ground. The SAR and HAC studies on the proposed clamshell mobile phone structure are also presented.