Small‐size wireless wide area network loop chip antenna for clamshell mobile phone with hearing‐aid compatibility

A loop chip antenna with an FR4 chip base suitable for clamshell mobile phone application to achieve wireless wide area network operation and hearing‐aid compatibility (HAC) is presented. The loop chip antenna is formed by a loop strip excited by a capacitively coupled feed, all printed on the surfaces of the FR4 chip base to achieve a small size of 1.35 cm 3 only. Two resonant loop paths are provided by the antenna and each loop path can generate its 0.5λ and 1.0λ resonant modes with good impedance matching. The excited loop resonant modes are formed into two wide operating bands for the antenna to cover GSM850/900 and GSM1800/1900/UMTS operations for both the open (talk) and closed (idle) states of the clamshell mobile phone. Furthermore, the loop antenna also excites small surface currents on the two ground planes of the clamshell mobile phone. In this case, weak near‐field EM fields in the vicinity of the mobile phone can be generated. Results show that the strengths of the near‐field E‐field and H‐field fall in the M3 or M4 Category, making the clamshell mobile phone with the proposed antenna to be an HAC communication device. The obtained specific absorption rate values in 1‐g and 10‐g head tissues also meet the limit of 1.6 and 2.0 W/kg, respectively.