Reconfigurable small antenna for mobile phone using MEMS tunable capacitor

In this paper we present a tunable PIFA which can be used in a mobile terminal. A NanoMech™ process enabled MEMS digital variable capacitor has been used as a capacitive load to the antenna. The antenna occupies a volume of just 1.3 cc and is targeted to be placed at the bottom corner of the device. With the help of tunability the antenna is able to cover from 704-960MHz in the low-band and 1710-2170MHz in the high-band, thus covering a wide range of frequency bands required for GSM/WCDMA/LTE systems. The MEMS device has an equivalent series inductance of less than 0.1nH hence the variation in the capacitance value with respect to frequency is less than 10%up to 5GHz. Further, the equivalent series resistance (ESR) of the digital variable capacitor is <;0.4Ω across the whole frequency range of interest, hence causing very low insertion loss to the antenna. The tunable antenna is characterized by measuring it in 3D anechoic chamber. The measured total efficiency of the antenna varies from -4 to -2dB for 700MHz-960MHz and -3dB to -2dB for 1710-2170MHz.