Broadband High Efficiency Mobile Antennas Using Parallel Resonant Loop Feeding

Abstract

In wireless device, antenna technology is known as an important technology for determining wireless performance. With the demand for miniaturization of wireless terminals and the rapid diversification of services, the demand for antenna performance is becoming very strict. In particular, the wireless terminal antenna has a very large demand for miniaturization, and the demand for broadband characteristics is great to satisfy various services. Currently, a wireless planar inverted-F antenna (PIFA) technology, which is advantageous for miniaturization, is widely used as a wireless terminal antenna. PIFA, however, has narrow impedance band characteristics. Recently, a new broadband wireless handset antenna technology called a planar inverted-E (PIE) antenna has been introduced to attract a lot of attention. PIE antennas are expected to be widely used as broadband wireless terminal antenna technology because they can improve impedance bandwidth 2-3 times compared to PIFA. Impedance bandwidth refers to the frequency band where the input impedance, an important characteristic of the antenna, satisfies the specification. In addition, the efficiency, which is another very important characteristic of the wireless terminal antenna, also varies with frequency, and a frequency region satisfying the specification can be defined as the efficiency bandwidth. Currently, PIE technology has been found to increase the impedance bandwidth more than two to three times compared to PIFA, but no research on efficiency bandwidth has been conducted. Radiation efficiency of the mobile handset antenna is recognized as a very important performance that determines the transmission and receiving distance of the wireless system, so there is a need for a study on the broadband technology of the efficiency bandwidth.

The PIE antenna technology can obtain a wide impedance bandwidth by utilizing a feeding structure existing in the antenna without the need of an additional radiator and an RF switch, so that the antenna can be miniaturized and have broadband characteristics without degradation in efficiency. Above all, using the PIE technique is economically advantageous because it saves additional development time and costs. Therefore, the PIE technology is expected to be an innovative technology that has great economic and technical advantages in the broadband antenna technique.

This doctoral thesis modeled the actual mobile handset antenna as a system ground plane, antenna element and feed structure including a source, and analyzed the coupling between each part. Theory of ground characteristic modes (TCM) were used to create optimal coupling between the ground plane and antenna elements, and the method of designing the optimal antenna using the reaction concept was described. The method of designing broadband characteristics and high radiation efficiency antenna while analyzing the mechanism coupled from the source to the feed structure and antenna element using two-port network analysis was described. This approach will provide a lot of convenience to design the high radiation efficiency broadband antenna needs in mobile device.