Tunable Dual-Band Antennas for 0.7–1.1-GHz and 1.7–2.3-GHz Carrier Aggregation Systems

Abstract

Single- and dual-feed, dual-frequency, low-profile antennas with independent tuning using varactor diodes have been demonstrated. The dual-feed planar inverted F-antenna (PIFA) has two operating frequencies which can be independently tuned from 0.7 to 1.1 GHz and from 1.7 to 2.3 GHz with better than $-10\,{\mathrm{ dB}}$ impedance match. The isolation between the high-band and the low-band ports is ${>}13\,{\mathrm{ dB}}$ ; hence, one resonant frequency can be tuned without affecting the other. The single-feed antenna has two resonant frequencies, which can be independently tuned from 1.2 to 1.6 GHz and from 1.6 to 2.3 GHz with better than $-10\,{\mathrm{ dB}}$ impedance match for most of the tuning range. The tuning is done using varactor diodes with a capacitance range from 0.8 to 3.8 pF, which is compatible with RF MEMS devices. The antenna volumes are $63 \times 100 \times 3.15\, {\mathrm{ mm}}^3$ on $\epsilon_{r}=3.55$ substrates and the measured antenna efficiencies vary between 25% and 50% over the tuning range. The application areas are in carrier aggregation systems for fourth generation (4G) wireless systems.