1. Field of the Invention
The present invention relates to a surface mountable chip antenna module for a portable wireless terminal, and more particularly, to a dual-band chip antenna module having elements connected in series to allow a high-band antenna element to utilize a low-band antenna element, such that the antenna module can have an increased current distribution and gain and thereby have an improved radiation performance.
2. Background of the Prior Art
Recently, mobile wireless terminals, such as the Personal Digital Assistant (PDA), the Personal Communication Service (PCS) terminal, the Distributed Communication System (DCS) terminal, Global Positioning System (GPS) terminal, cellular phones and wireless notebook computers, are becoming more popular, and terminals with various functions and designs are being introduced. Further, small-sized, slim, and lightweight terminals are also being introduced, and at the same time the terminals are required to have various functions to satisfy user's demand. Therefore, the designs of the terminals are focused on size reduction while maintaining or improving the functions to satisfy the user's demand.
Specifically, a rod antenna (or whip antenna) and a helical antenna, which protrude outward from the terminal, are easy to break, and deteriorate the external appearance and portability of the terminal. Therefore, an antenna installed within the terminal is becoming more popular (and referred to as a built-in antenna, internal antenna, or intenna), and efforts are ongoing to improve the performance and productivity of the built-in antenna. There are two types of built-in antennas in common use: a planar inverted F antenna (PIFA) module having a feeding point and a ground point, and a chip antenna module suitable for mounting on a ceramic dielectric substance and having a copper coil the turns of which are adjusted according to the operating frequency of the terminal.
Since the chip antenna module is mounted on an RF mainboard of a terminal in the form of surface mounted device (SMD), it takes less space than the PIFA type antenna and thereby enables the terminal to have a slim, simple, and lightweight appearance.
The chip antenna module is commonly used for a dual-band terminal. That is, the dual-band terminal has two antenna elements mounted on its mainboard, for example, a low-band antenna element for a 900-MHz CDMA or GSM application and a high-band antenna element for an 1800-MHz PCS or DCS application.
The arrangement of the low-band and high-band antenna elements of the chip antenna module is disclosed in co-pending U.S. patent application Ser. No. 10/969,589, filed on Oct. 20, 2004, and assigned to the present assignee, in which an RF connector of a mainboard and two antenna elements of different frequency bands are connected in parallel, and a radiation plate is employed to improve a radiation characteristic of the antenna.