Study of promising internal WWAN antenna for the folder-type mobile phone with various chassis shapes

Stable performances of an internal WWAN antenna applied in the folder-type mobile phone with various chassis shapes are obtained. Six different states of the folder-type mobile phone, wherein the chassis shapes vary greatly, are studied. The WWAN antenna is mounted at the bottom of the main ground, and there are three connecting positions between the two grounds. For each operating states, the upper ground is connected to the main ground at one of the three connecting positions. At each position, a band-stop circuit is designed to excite a parallel resonance at around 900 MHz and leads to high impedance seen into the upper ground in the 900 MHz band. This greatly decreases the excited surface currents on the upper ground, making the presence of the upper ground have small effects on the performances of the WWAN antenna mounted at the bottom of the main ground. At around 1900 MHz, owing to its shorter wavelength, the surface currents on the upper ground excited by the WWAN antenna on the main ground are small. Thus, over both the 900- and 1900 MHz bands, the various orientations of the upper ground to the main ground cause small effects on the WWAN antenna embedded therein. Details of the obtained results are presented.