Study of Microstrip-fed Ring Slot Antennas with Harmonic Suppression

• Main Author: 張明軒
• Other Authors: 沈昭元
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/83282950870305764792

碩士 === 逢甲大學 === 電機工程所 === 101 === Recently, it is a pre-requisite requirement for hand-held communication products to possess the advantages such as light in weight, compact size and low manufacturing cost. To satisfy these requirements, a single structure design that comprised of an antenna integrated with the front-end circuit of the communication system is presently attracting many attentions. However, higher-order resonant modes excited by the antenna can cause EMI problems on the active circuit, which lead to degrading the performances of the system. Hence, the common solution to solve this problem is to use low-pass or band-pass filter. However, this method will increase the circuit size, manufacture cost, and insertion loss. To resolve these disadvantages, harmonic suppression antenna design is now an attractive topic of research interest. This thesis are divided into two parts, the first part presents a harmonic suppression annular-ring slot antenna that operates in the 2.4 GHz WLAN band. Here, the inverted U-shaped ground defect structure (DGS) is used as a low-pass filter, and it is integrated into an annular-ring slot antenna, so that it can suppress unwanted higher-order resonance modes (return loss < 3 dB) within the frequencies range between 3 and 9 GHz. In the second part of this thesis, a circularly polarized (CP) annular-ring slot antenna with harmonic suppression is proposed. It is noteworthy that this CP annular-ring slot antenna with harmonic suppression design has never been discussed or reported elsewhere in the open-literature. In this design, a novel CP annular-ring slot antenna operating at WLAN 2.4 GHz is initially studied with axial ratio (AR) bandwidth of 210 MHz (8.79%). Here, the main advantage of this CP slot antenna design is that during the process of integration with the harmonic suppression structure (DGS) discussed in the part 1, there is no need to alter the antenna’s feed terminal. By integrating the DGS into the proposed CP annular-ring slot antenna structure, a 2.4 GHz WLAN antenna with wide harmonic suppression bandwidth between 3 and 10 GHz is achieved, and the AR bandwidth is 223 MHz (9.33%).