Wideband folded patch antennas
寬頻摺疊貼片天線
Student thesis: Master's Thesis
Author(s)
Related Research Unit(s)
Detail(s)
Awarding Institution | |
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Award date | 15 Jul 2008 |
Link(s)
Permanent Link | https://scholars.cityu.edu.hk/en/theses/theses(36376ef7-6f74-4557-a4e4-32d1ffe0124b).html |
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Other link(s) | Links |
Abstract
This thesis presents the design of three novel small wideband microstrip
patch antennas. Microstrip antennas have the attractive characteristics of
low profile, light weight and simple structure. However, its bandwidth is
limited to a few percent which is not enough for most of the wireless
communication systems nowadays. Some bandwidth enhancement
techniques have been proposed such as using thick foam substrate, cutting
one or two U-slots on the patch, stacking an additional patch on top of the
original one and using shorting pins. For some applications such as indoor
wireless communications, conventional patch antennas may not be suitable
because of its large size especially when operating at lower microwave
frequency. Therefore, many methods have been proposed in the literature to
tackle this problem. One of the most effective methods is to use a shorting
wall. This method can reduce the length of a half wavelength patch by half to a quarter wavelength patch. Based on a combination of these techniques,
three novel antenna designs are presented here.
Firstly, a folded patch with a shorting wall is studied. This antenna consists
of a folded trapezoidal patch with a shorting wall and a shorting pin. By
offsetting the feeding probe from the midline of the patch, one more
resonance is found. Combining this technique with a two-sectioned feeding
probe and a 50% thicker profile, the impedance bandwidth is improved
from 29% to 56% (SWR≤2). To understand the relationship between the position of the coaxial feed and
the bandwidth, an analysis will be presented. For the two-sectioned feeding
probe, a parametric study will be carried out telling how the thickened
diameter of the probe helps improves the bandwidth.
Secondly, a folded shorted patch with two L-slots cut on the main part is
investigated. This design adds the idea of half double U-slots patch into the
folded shorted patch and the two L-slots contributes to the two extra
resonances found on the SWR curve. Moreover, the distance between the
folded part and the main part has to be increased for optimum performance
but the height of the main part is kept low. This approach can prevent from
the high input inductance caused by the coaxial feed. As a result, a very
wide bandwidth of 99% (SWR≤2) and average gain of 6.8dBi are achieved.
Finally, a double folding structure is introduced on a folded shorted patch.
An additional folded part is introduced at the inner part of the half U-slot and can further enhance the bandwidth to 5:1 or 133% (SWR≤2). At the
same time, to assist the impedance matching, a wings-liked wall is used to
connect the folded part and the main part. An average gain of 5.4dBi is
obtained over the pass-band.
To summarize, three small wideband folded patch antennas have been
successfully designed.
- Microstrip antennas, Broadband communication systems