(A) study on the wideband built-in antenna with slow-wave feed structure

Abstract

Recently, the rapid growth in mobile communication systems has led to an explosive demand for the development of a small antenna with multi-band functions. Planar Inverted-F Antennas (PIFA) or shorted patch antennas have the attractive features of low profile and light weight in mobile phones as internal antennas. However, for the recent trend such as penta-band (GSM850, GSM900, DCS, PCS, WCDMA2100), the size of PIFA may be too large to cover above all bands simultaneously for practical applications. Especially, in the low frequency bands such as GSM850/GSM900, it is very hard to achieve a wideband performance ranging from 824MHz to 960MHz. In this paper, I propose a wideband built-in antenna solution using novel feed structure for mobile antenna. Generally, the feed part of the PIFA antenna could be substituted as an inductive circuit equivalently. To compensate the inductance of the feed structure, I propose various capacitive-loading feed structure for wideband built-in antenna solution. First, I propose the advanced PIFA solution with a folded feed structure to increase the parasitic capacitance. Using the proposed design scheme, miniature built-in antenna solution can cover the GSM850, GSM900, DCS, PCS, WCDMA2100, WiBro, Bluetooth and Mobile WiMax bands within $38.5mm\times18mm\times6t$ antenna size Second, I propose an ultra wideband built-in antenna with an advanced feed solution including compact coupling feed structure which is implemented between the feed pin and radiators. This feed structure uses a folded finger coupling structure to increase the coupling energy between feed and radiator element. Using the proposed design scheme, we can use a capacitive-loading feed structure with a folded coupling structure instead of inductive PIFA antenna feed mechanism. Last, to maximize the EM coupling coefficient between the feed structure and radiator element, I suggest the slow-wave feed structure for the ultra wideband antenna solution. In this pa...