基于Butler矩阵的双频双极化多波束天线关键技术研究
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摘要
多波束天线在通信系统中得到了非常广泛的应用,而双频、双极化是其重要的研究方向之一。本文基于传统平面电路工艺加工技术,以C波段无线通信为应用背景,对双频双极化多波束天线系统中的关键技术进行深入系统研究,具体研究内容包括：
1.提出并研制了一种单层微带宽带Butler矩阵结构。在三线宽带耦合器中加载集总分布元件,使得耦合器的尺寸接近减小一半；采用多个U型耦合线代替Schiffman移相器中的单个U型耦合线,可在较宽频带范围内获得良好的传输、相位特性。仿真和测试结果表明该Butler矩阵可实现20%的相对带宽。
2.采用悬置带线设计Butler矩阵的定向耦合器、交叉结和Schiffman移相器,对双面耦合定向耦合器和双面交叉结进行电容加载,实现相速度补偿,从而使得耦合器和交叉结具有良好的宽带性能。仿真和测试结果表明该Butler矩阵在50%的带宽内损耗小和端口一致性好,且具有尺寸紧凑和加工方便等优点。
3.提出了一种微带馈电双频双极化的矩形贴片天线。在矩形贴片加载标语牌形槽,选择在适当的馈入点用单根微带线进行馈电,激励起的TM01模和TM10模分别工作在两个谐振频点,同时引入两个切角来调节交叉极化电平且基本不影响谐振频率。该天线单元具有交叉极化小、频率比(FR)调节方便且可调范围宽、结构紧凑和方便应用于天线阵等优点。
4.在双重特性谐振(DBR)滤波器的基础上,对高隔离度双工器进行研究,分别引入缺陷地结构(DGS)、螺旋型紧致微带谐振单元(SCMRC)和双频分支线(DBS),在不增加原有尺寸的基础上,进一步抑制上寄生通带,进而提高了上阻带抑制度。仿真和测试结果表明本文所研制的三种双工器的隔离度大于65dB,插损小于1.3dB。
5.提出了一种折叠的阶梯阻抗谐振器(SIR)结构,采用折叠SIR设计双工器中的带通滤波器,在T型结中引入SCMRC提高双工器的隔离度和减小了T型结的尺寸。研制的小型化双工器尺寸只有0.87λg×0.23λg,仿真和测试结果表明该双工器的隔离度大于65dB,插损小于1.7dB。
6.采用宽带Butler矩阵、双频双极化微带天线阵列和双工器等构建了基于Butler矩阵的多波束天线,设计并研制波束切换网络——单刀四掷开关(SP4T)和收发前端等关键部件,在此基础上对基于Butler巨阵的双频双极化多波束天线进行了实验研究,为进一步工程化应用奠定了基础。
Multi-beam antennas find wide application in wireless communication systems, and it is one of the most popular research directions to study dual-frequency dual-polarization multi-beam antennas. In this dissertation, for the application of the C-band wireless communication systems, several key techniques of dual-frequency dual-polarization multi-beam antenna systems are investigated based on the conventional planar circuit fabrication techniques. The detailed contents are as follows:
1.A microstrip broadband Butler matrix is proposed and fabricated. A3-branch line wideband coupler with lumped and distributed elements is adopted in the design, which can reduce almost half area. To get good phase and transmission performances during a wide band, an improved Schiffman phase shifter is designed, which uses multi-U-shaped coupled-line instead of the single-U-shaped one. The simulated and measured results show that the bandwidth of the designed Butler matrix is20%.
2. The directional coupler, double-side crossover and Schiffman phase shifters of Butler matrix are designed based on suspended stripline. The double-side coupled directional coupler and double-side crossover are capacitive loaded to implement phase velocity compensation, and the broadband performances are obtained. The simulated and measured results show that the designed Butler matrix is characteristic of low loss and good port consistency over the50%bandwidth, and it is compact and can be fabricated easily.
3. A compact microstrip-feed dual-frequency dual-polarization rectangle patch antenna embedded a placard-shaped slot is proposed. By exciting the patch at an appropriate position using a single microstrip feed line, TM01and TM10modes are both excited, respectively, at the first and second resonant frequencies. By introducing two corner cuts, we can adjust the cross polarization levels with little influence on the resonant frequencies. The simulated and measured results show that the antenna unit has low cross polarization levels, a wider and easily adjusted frequency-ratio (FR) and a compact size, and it is readily used in array configurations.
4.The high isolation diplexers are studied based on the dual behavior resonator (DBR) microstrip filter. The defected ground structure (DGS), spiral compact microstrip resonant cell (SCMRC), and dual-band stub (DBS) are introduced in, respectively, so the upper parasitic passbands are suppressed, and the rejection in the upper stopband could be improved without increasing the original size. The simulated and measured results of the three diplexers designed in this dissertation show that the isolations are better than65dB, and the losses are less than1.3dB.
5. A folded stepped-impedance resonator (SIR) structure is proposed. By applying the proposed resonator, the compact band-pass filters (BPFs) of the diplexer are realized. With the adoption of SCMRC into the T-junction, the diplexer isolation is improved, and the size is reduced. The diplexer is very compact and occupies a small area of0.87λg×0.23λg, The simulated and measured results show that the isolations are better than65dB, and the losses are less than1.7dB.
6. A Butler matrix-based multi-beam antenna is constructed using the broadband Butler matrix, the dual-frequency dual-polarization microstrip array and the diplexer. The beam switching network (SP4T) and the Rx/Tx are designed and fabricated. And an experiment was carried out to verify the idea.
1.提出并研制了一种单层微带宽带Butler矩阵结构。在三线宽带耦合器中加载集总分布元件,使得耦合器的尺寸接近减小一半；采用多个U型耦合线代替Schiffman移相器中的单个U型耦合线,可在较宽频带范围内获得良好的传输、相位特性。仿真和测试结果表明该Butler矩阵可实现20%的相对带宽。
2.采用悬置带线设计Butler矩阵的定向耦合器、交叉结和Schiffman移相器,对双面耦合定向耦合器和双面交叉结进行电容加载,实现相速度补偿,从而使得耦合器和交叉结具有良好的宽带性能。仿真和测试结果表明该Butler矩阵在50%的带宽内损耗小和端口一致性好,且具有尺寸紧凑和加工方便等优点。
3.提出了一种微带馈电双频双极化的矩形贴片天线。在矩形贴片加载标语牌形槽,选择在适当的馈入点用单根微带线进行馈电,激励起的TM01模和TM10模分别工作在两个谐振频点,同时引入两个切角来调节交叉极化电平且基本不影响谐振频率。该天线单元具有交叉极化小、频率比(FR)调节方便且可调范围宽、结构紧凑和方便应用于天线阵等优点。
4.在双重特性谐振(DBR)滤波器的基础上,对高隔离度双工器进行研究,分别引入缺陷地结构(DGS)、螺旋型紧致微带谐振单元(SCMRC)和双频分支线(DBS),在不增加原有尺寸的基础上,进一步抑制上寄生通带,进而提高了上阻带抑制度。仿真和测试结果表明本文所研制的三种双工器的隔离度大于65dB,插损小于1.3dB。
5.提出了一种折叠的阶梯阻抗谐振器(SIR)结构,采用折叠SIR设计双工器中的带通滤波器,在T型结中引入SCMRC提高双工器的隔离度和减小了T型结的尺寸。研制的小型化双工器尺寸只有0.87λg×0.23λg,仿真和测试结果表明该双工器的隔离度大于65dB,插损小于1.7dB。
6.采用宽带Butler矩阵、双频双极化微带天线阵列和双工器等构建了基于Butler矩阵的多波束天线,设计并研制波束切换网络——单刀四掷开关(SP4T)和收发前端等关键部件,在此基础上对基于Butler巨阵的双频双极化多波束天线进行了实验研究,为进一步工程化应用奠定了基础。
Multi-beam antennas find wide application in wireless communication systems, and it is one of the most popular research directions to study dual-frequency dual-polarization multi-beam antennas. In this dissertation, for the application of the C-band wireless communication systems, several key techniques of dual-frequency dual-polarization multi-beam antenna systems are investigated based on the conventional planar circuit fabrication techniques. The detailed contents are as follows:
1.A microstrip broadband Butler matrix is proposed and fabricated. A3-branch line wideband coupler with lumped and distributed elements is adopted in the design, which can reduce almost half area. To get good phase and transmission performances during a wide band, an improved Schiffman phase shifter is designed, which uses multi-U-shaped coupled-line instead of the single-U-shaped one. The simulated and measured results show that the bandwidth of the designed Butler matrix is20%.
2. The directional coupler, double-side crossover and Schiffman phase shifters of Butler matrix are designed based on suspended stripline. The double-side coupled directional coupler and double-side crossover are capacitive loaded to implement phase velocity compensation, and the broadband performances are obtained. The simulated and measured results show that the designed Butler matrix is characteristic of low loss and good port consistency over the50%bandwidth, and it is compact and can be fabricated easily.
3. A compact microstrip-feed dual-frequency dual-polarization rectangle patch antenna embedded a placard-shaped slot is proposed. By exciting the patch at an appropriate position using a single microstrip feed line, TM01and TM10modes are both excited, respectively, at the first and second resonant frequencies. By introducing two corner cuts, we can adjust the cross polarization levels with little influence on the resonant frequencies. The simulated and measured results show that the antenna unit has low cross polarization levels, a wider and easily adjusted frequency-ratio (FR) and a compact size, and it is readily used in array configurations.
4.The high isolation diplexers are studied based on the dual behavior resonator (DBR) microstrip filter. The defected ground structure (DGS), spiral compact microstrip resonant cell (SCMRC), and dual-band stub (DBS) are introduced in, respectively, so the upper parasitic passbands are suppressed, and the rejection in the upper stopband could be improved without increasing the original size. The simulated and measured results of the three diplexers designed in this dissertation show that the isolations are better than65dB, and the losses are less than1.3dB.
5. A folded stepped-impedance resonator (SIR) structure is proposed. By applying the proposed resonator, the compact band-pass filters (BPFs) of the diplexer are realized. With the adoption of SCMRC into the T-junction, the diplexer isolation is improved, and the size is reduced. The diplexer is very compact and occupies a small area of0.87λg×0.23λg, The simulated and measured results show that the isolations are better than65dB, and the losses are less than1.7dB.
6. A Butler matrix-based multi-beam antenna is constructed using the broadband Butler matrix, the dual-frequency dual-polarization microstrip array and the diplexer. The beam switching network (SP4T) and the Rx/Tx are designed and fabricated. And an experiment was carried out to verify the idea.
引文
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