Small, Multi-Band, and MIMO Antennas for Mobile Communication Systems

Abstract

This dissertation is dedicated to implementation of slot antenna, meander antenna, reconfigurable antenna, and MIMO antenna. The design details of the proposed antenna, along with computer simulation and measurement results, are given. First, a compact dual-band slot antenna with capacitor loading is proposed for the WLAN bands (2.4 – 2.49 and 5.15 – 5.35 GHz). The antenna is composed of a modified L-shaped slot and a capacitor. The capacitor is used to generate two surface-current paths on the ground and to miniaturize the antenna size. Second, a compact wideband open-end slot antenna is proposed for DCS, PCS, UMTS, WLAN, and WiMAX band applications. The antenna is composed of an open-ended slot and a feed line within the slot. The open-end slot decreases the antenna size in half, compared to a conventional slot-ring antenna. Furthermore, the narrowed slot and feed line miniaturize the antenna and obtain wideband performance using the inherent impedance matching network of the feed line. Third, a planar monopole multi-input multi-output (MIMO) antenna that is small in size (15 mm by 30 mm) and that offers high high-isolation performance is presented. The antenna is miniaturized using inductive coupling within a meander-line radiator and capacitive coupling between a radiator and an isolator. High isolation is achieved by a T-shaped stub attached to the ground plane between two radiators, which also contributes to the small size using a folded structure and the capacitive coupling with radiators. Forth, a frequency reconfigurable multiple- input multiple-output (MIMO) antenna is presented. The proposed MIMO antenna consists of two reconfigurable printed monopole antennas with coupled conductors and an isolation improvement structure located between the two antennas. In order to change the operating frequency, PIN-diodes are embedded in the antennas. According to the on/off state of the PIN-diode, the resonant frequency is changed between the WLAN band (2400-2483 MHz and 5150-5350 MHz) and the m-WiMAX band (3400-3600 MHz). Last, an open-end annular slot antenna is proposed for 1.74-3.0 GHz Wideband MIMO applications. The antenna is composed of an open-ended annular slot and a feed line within the slot. The annular slot and feed line miniaturize the MIMO antenna and obtain wideband performance using the inherent impedance matching network of the feed line. In addition, the orthogonal location achieves orthogonal pattern diversity to improve MIMO performance.