【作者】 王辰；

【导师】 胡斌杰；

【作者基本信息】 华南理工大学 ， 通信与信息系统， 2012， 博士

【摘要】 伴随着无线通信系统的高速发展，天线作为发射和接收电磁波信号的前端设备，也顺应着发展的要求，不断地朝多频化、小型化等方向演进。而复合左右手传输线（CRLH-TL）结构，为新型天线的多频、小型化设计提供了新的思路和方法。复合左右手传输线是一种同时具备左手传输线和右手传输线性质的特殊传输线。它在较低的左手频率区域，呈现出相位和能量的传播方向相反的左手特性；而在较高的右手频率区域，则呈现出右手特性，即相位和能量的传播方向相同。除此之外，复合左右手传输线结构，能够在较低的左手频率区实现较大的传播常数值，且传输线的相位关系可以通过独立地调节复合左右手传输线的单元结构的相关尺寸参数，来获得期望的目标值。正是由于复合左右手传输线结构的这些特性，使其能够实现在一定范围内任意频率比的多频天线的设计，同时还能够实现天线的小型化。本文首先研究分析了左手材料的相关理论，主要性质以及左、右手区域的判断方法。接着，从等效电路的角度，在理论上提出了改进复合左右手传输线单元结构的两种方法。在此基础上，设计了新型的复合左右手传输线单元结构，并将其应用于微带天线，实现了新型多频、小型化天线的设计应用。本论文的主要工作以及创新成果如下：(1)提出了等效电路元件参数的提取方法，以及两种改善复合左右手传输线特性的方法。根据等效电路的特点，提出了一种较为准确的等效电路元件参数的提取思路，即通过ABCD矩阵与S参数的关系，从仿真的S参数得到复合左右手传输线等效电路模型中的各个元件参数值。从电磁波的仿真结果以及电路模型的仿真结果可知，得到的等效电路的元件参数值是准确、有效的。同时，根据对复合左右手传输线等效电路以及色散关系曲线的研究，得出了利用分布参数实现左手特性的设计理念以及改进方向：单独或者同时增大等效电路中并联电感LL以及串联电容CL的数值，均能增大复合左右手传输线的传播常数β，进而使单元结构的物理尺寸减小。(2)基于多层的蘑菇结构状的复合左右手传输线单元结构，设计了一款新型的三频、小型化微带天线。多层左手结构通过在原始的蘑菇结构的复合左右手传输线单元中增加金属夹层，来增大左手串联电容CL的值。对比分析了单层和多层的单元结构，通过理论分析以及仿真验证的方式得出，多层的结构通过单独地增大左手串联电容的方式，提高了复合左右手传输线在左手频率区内的传播常数值。并在此基础上，设计出了一款新型的三频、小型化天线。这款新型的天线工作在三个频段内：最低的谐振频段工作在模式n=1的情况下，属于左手频率区，可以通过调节天线中央的左手结构来升高或者降低最低频的大小；较高的两个谐振频率属于右手频段，和传统的微带天线类似，它的工作频段可以通过改动天线外围的贴片尺寸的大小来调节。仿真与测试结果表明，这款天线能够在较大的频率范围内实现任意的频率比。(3)提出了一种带有螺旋开槽的多层复合左右手传输线单元结构，并基于该新型结构，设计出一款多频、小型化微带天线。在多层蘑菇结构的基础上，引入了螺旋电感，同时增大了左手串联电容CL以及并联电感LL的值。采用这种方法，设计出一种新型的多层、带有螺旋电感的复合左右手传输线单元结构，进一步实现了较低频率下的较大β值。在此基础上，设计了一款多频、小型化的微带天线，并采用传输线的分析方式对此款天线的谐振特性进行了分析，从理论上给出并通过仿真及测试验证了天线的各个工作模式。通过天线的加工与仿真测试，得出天线的贴片尺寸仅为λ0/9.5×λ0/5.88×λ0/32.9。此款带有螺旋开槽的复合左右手传输线结构的天线能够实现四个工作频段，且具有明显的尺寸优势。同时，可以通过调整天线不同结构的尺寸大小，来实现不同的频率比。(4)基于螺旋开槽、多层的复合左右手传输线结构，设计出一款三频、小型化的圆极化微带天线。这款新型设计的圆极化微带天线通过天线中央的左手结构，实现了多频；同时采用的是双馈电点的方式，利用Wilkinson功分器对天线进行馈电，实现了圆极化。天线工作在三个频段内：较低的两个频段工作在模式n=1以及模式n=0的情况下，属于左手频率区。最高的工作频率属于右手区。这款三频、圆极化天线可以通过调整天线不同结构的尺寸大小，来实现不同的频率比。天线的贴片边长相比于第一个工作频率点2.4GHz仅为λ0/6.6。与传统的圆极化微带天线相比，除了多频特性外同样具有明显的尺寸优势。最终的测试结果与仿真结果吻合。更多还原

【Abstract】 With the rapid development of the wireless communication systems, antennas aredeveloping towards the trend of multi-frequency and miniaturization as the front-enddevices for transmitting and receiving electromagnetic signals. The compositeright/left-handed transmission lines (CRLH-TL) structures provide a conceptual routefor implementing novel multi-frequency and compact antennas. CRLH-TL is anartificial transmission lines which both has the left-handed (LH) and right-handed(RH) characteristics at the same time. The LH characteristics dominate the lowerfrequency band, and at this LH band the phase velocity and the group velocity areanti-parallel. While the RH characteristics dominate the higher frequency band, atwhich band the phase velocity and the group velocity are parallel. In addition,CRLH-TL can realize a larger propagation constant at lower LH frequency region,and the phase relations of the CRLH-TL can be controlled by the element values oftheir constructing unit cell to obtain a desired result. Because of these characteristics,CRLH-TL can be used to realize multi-frequency antennas with arbitrary frequencyratios. They also can be used to obtain the compact antennas.The thesis studied the main theory of left-handed metamaterials (LHMs),including the characteristics and the determination methods. And then it also providedtwo methods to improve CRLH-TL unit cell structure. Based on this, the thesis alsodesigned novel CRLH-TL unit cell structures and applied them to realize multibandand compact antennas. The main work and contributions of this thesis are as follows:(1) Proposed a method to extract the circuit parameters and two approach toimprove the characteristics of the proposed CRLH-TL structure. Accordingto the characteristics of the equivalent circuit model, the thesis provides amethod to extract the circuit parameters from simulated S parameters.Electromagnetic simulation and circuit simulation show that the circuitmodel and the extraction method are reliable and correct. Based on the research of the circuit model and the dispersion relation, an approach toimprove the characteristics of the CRLH-TL structure is obtained: increasingseries capacitance CLor shunt inductance LLseparately or simultaneously,which both can enlarge the propagation constant and decrease the size of theunit cell structure.(2) Proposed a novel tri-band compact patch antenna based on the multi-layermushroom CRLH-TL structures. The multi-layer mushroom structureenhances the LH series capacitance CLby loading middle metal caps into theoriginal mushroom structure. The comparison research on the single layerand multi-layer structures demonstrate that, the multi-layer structure hasenlarged the propagation constant in the LH region. Anovel tri-band compactpatch antenna is designed based on the multi-layer mushroom CRLH-TLstructures. The novel antenna works at three operating frequencies. Thelowest resonant frequency belongs to mode n=1, which is in LH frequencyregion. The LH resonant frequency can be adjusted by tuning the size of thecentral CRLH-TL structure. The two higher resonant frequencies belong toRH frequency region, which can be adjusted by changing the patch size.Different scale of frequency ratio can be arbitrarily chosen by adjusting thedimensions of patch and CRLH-TL structures.(3) Proposed a novel multilayer and spiral-slot CRLH-TL structure andimplemented a multiband compact patch antenna based on it. The proposedCRLH-TL structure simultaneously enhances shunt inductance and seriescapacitance by loading spiral-slot and middle metal caps into originalmushroom structure. By this way, the multi-layer and spiral-slot structure hasfurther enlarged the propagation constant of the CRLH-TL in the LH region.In addition, a novel compact multi-frequency patch antenna with multilayerand spiral-slot CRLH-TL structures is designed and proposed. The operatingmodes of the multiband patch antenna is analysed and explained by transmission line theory and the simulated results prove the theory analysis.A novel antenna prototype with four resonances is fabricated, which has thedimensions of λ0/9.5×λ0/5.88×λ0/32.9at the first working frequency.Frequency ratio can be chosen by adjusting the dimensions of the outer patchand the central CRLH-TL structures.(4) Proposed a compact tri-band circularly polarized (CP) patch antenna withmultilayer and spiral-slot CRLH-TL structures. This novel CP antenna canrealize multiband by loading CRLH-TL structures and circular polarizationby Wilkinson divider. A CP antenna working at2.4GHz,3.1GHz and3.5GHz is fabricated. The lower two operating frequencies are controlled by thecentral CRLH-TL structure and the highest operating frequency is influencedby both the outer patch and the central CRLH-TL structures. Compared withthe previous multiband CP antennas, the frequency ratio between differentbands can be set arbitrarily in a wide range, by adjusting the size of differentparts of the proposed antenna. The length of the top patch is λ0/6.6at2.4GHzand it is much smaller than the conventional CP antenna. The measured andsimulated reflection coefficient curves are well matched.更多还原