标题: | 宽频微带泄漏波天线 Broadband Leaky-Wave Antenna |
作者: | 洪万铸 Wanchu Hong 林育德 Yu-De Lin 电信工程研究所 |
关键字: | 泄漏波天线;宽频天线;宽频之平衡-不平衡电路;微带天线;馈入结构;leaky-wave antenna;broadband antenna;broadband balun;microstrip antenna;feeding network |
公开日期: | 2002 |
摘要: | 由于无线通讯蓬勃的发展,使得人们对频宽的需求逐渐增加,因此设计宽频且高增益的天线提供无线通讯应用所需成为一个很大的挑战。本文提出宽频泄漏波天线设计方法。为能完全展现这些宽频泄漏波天线之宽频特性,本文亦提出以微带线设计宽频平衡-不平衡电路来激发第一高阶漏波模。 首先,在本文中提出反向平衡式微带线设计方法。此反向平衡式微带线乃利用平衡式微带线结构而将基板上下之正负微带位置互易而得。在本文中,将详述如何将正负微带位置互易的方法。由反射损失的量测结果可以看到反射损失小于-10dB的频宽几乎从 DC至17.4 GHz 或从 2.8 GHz至40 GHz。不同的频宽是因为不同的设计参数而定。此反向平衡式微带线跟平衡式微带线结合使用则能形成两对宽频之平衡-不平衡电路,并用来当宽频泄漏波天线之基本馈入结构。 其次,根据微带线之第一高阶漏波模特性,本文提出一新颖演算法则来设计宽频缓变泄漏波微带天线。此方法并可用于分析此类线性缓变之泄漏波微带天线特性和作为近似模型。对此宽频泄漏波天线之馈入结构亦一并提出。利用上述之两对宽频之平衡-不平衡电路,将其中一对馈入微带天线而另一对接微带线之地。此背对背馈入结构之反射损失的量测结果可以看到VSWR£2 的频宽从 2.2 GHz至18.6 GHz。而此宽频缓变泄漏波微带天线反射损失的量测结果,可以看到VSWR£2 的频宽从7 GHz至16.4 GHz,相对的频宽约2.34:1。 另一例子是毫米波宽频缓变结构之泄漏波微带阵列天线,由四个单元所构成之一维阵列。此毫米波宽频缓变泄漏波微带天线反射损失之VSWR£2 的频宽量测结果,从13.3 GHz至35.0 GHz。 由于直线型态的缓变宽频泄漏波微带天线相当消耗面积,为使得天线变得更致密以节省所消耗面积,本文亦提出螺旋状弯曲之缓变泄漏波微带天线设计。此螺旋状弯曲之缓变泄漏波微带天线反射损失之VSWR£2 的频宽量测结果,如同直线型态的缓变宽频泄漏波微带天线,相对的频宽大于2.3:1。 最后,在本文中将提出单一导体带状天线结构。此单一导体带状天线结构在基板上只有单一带状导体而无任何其他实际接地面。对于此结构之第一高阶漏波模特性,利用全波分析之积分方程法作一探讨,发现拥有相当宽频之辐射区段。为能激发此结构之第一高阶漏波模,利用上述之两对宽频之平衡-不平衡电路,将其中一对馈入带状天线而另一对互接并拉回至原先接微带线之地。所有数值计算和量测结果会在本文中做一说明。此单一导体带状泄漏波天线反射损失之VSWR£2 的频宽量测结果,从6.55 GHz至13.75 GHz,相对的频宽大于2.34:1。由于相位常数之特性,此单一导体带状天线结构之主波束位置几乎不会随频率变动并几乎维持在 endfire 方向。此单一导体带状泄漏波天线虽和缓变泄漏波微带天线均同为宽频泄漏波天线并几乎操作在相同频带上,天线长度却短少许多。 This thesis proposes the design methodology of broadband leaky-wave antennas. To exploit fully the broadband feature of these broadband leaky-wave antennas, also presented is the design method of the novel broadband planar balun used to excite the first higher order leaky mode. First, an inverted balanced microstrip line structure is proposed. This inverted balanced microstrip line structure is developed from the balanced microstrip line. The position of the positive strip on the upper substrate side is exchanged with that of the negative strip on the lower substrate side by the method proposed in this thesis. The measured return loss is observed to be better than -10dB over a frequency range extending from DC up to 18.6 GHz or from 2.8 GHz up to 40 GHz depending on the different design parameters. United with the balanced microstrip line, this inverted balanced microstrip line can be used to form into a pair of broadband baluns. Using this broadband balun can realize a broadband leaky-wave antenna. Secondly, based on the characteristics of the first higher order leaky-mode for the microstrip antennas, this thesis proposes a novel scheme for the empirical design of broadband tapered microstrip leaky-wave antennas. This scheme is demonstrated to be able to explain and approximately model the radiation characteristics of a linearly tapered leaky-wave microstrip antenna. Also presented is the broadband feeding structure that uses the balanced and the inverted balanced microstrip lines to form two pairs of broadband baluns. The balun on the upper substrate side feeds the microstrip antenna, while the one on the lower substrate side directly connects with the ground plane of the microstrip antenna. The measured return loss of the back-to-back feeding structures has a VSWR£ 2 from 2.2 GHz to 18.6 GHz. The measured bandwidth of the tapered microstrip leaky-wave antenna has a VSWR£2 from 7 GHz to 16.4 GHz, yielding a relative bandwidth of 2.34:1, more than an octave. Another example is the design of the millimeter-wave broadband tapered microstrip leaky-wave antenna array of 1´4 elements. The measured bandwidth of this millimeter–wave broadband tapered microstrip leaky-wave antenna array with 1´4 elements for a VSWR£ 2 is from 13.3 GHz to 35 GHz. With a straight profile, the broadband tapered microstrip leaky-wave antenna consumes area. To design a more compact broadband antenna, the tapered microstrip antenna is curled to save area. Presented is a compact broadband tapered microstrip leaky-wave antenna with a curled profile that has a bandwidth of more than 2.3:1 for a VSWR£ 2. Finally, proposed is a single-conductor strip antenna with only a single-conductor strip on a substrate without any practical ground plane. By using the full-wave integral equation method, the first higher order leaky mode of this single-conductor strip structure is investigated and found to possess a broadband radiation regime. To excite this first higher order leaky mode, a broadband planar balun is developed from the balanced microstrip lines and the inverted balanced microstrip lines. Like the feeding structure of broadband tapered microstrip leaky-wave antenna, the balun on the upper substrate side feeds the strip antenna with an offset from the edge, while the positive and negative balun strips on the lower substrate side are directly interconnected and returned back to the original ground plane of the microstrip line.Both the numerical simulation and the measurement data are presented. This single-conductor strip leaky-wave antenna has a bandwidth of 2.34:1 (from 6.55 GHz to 13.75 GHz) for a VSWR*2. Owing to the particular characteristics of its normalized phase constant, this single-conductor strip leaky-wave antenna has a fixed mainbeam radiation pattern in the endfire direction. As a broadband leaky-wave antenna, the length of this single-conductor strip leaky-wave antenna is much shorter than that of the tapered microstrip leaky-wave antenna. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#NT910435003 http://hdl.handle.net/11536/70533 |
显示于类别: | Thesis |