A novel approach for improving antenna bandwidth is described using a 6-element Yagi-Uda array as an example. The new approach applies Central Force Optimization, a deterministic metaheuristic, and Variable Z0 technol...A novel approach for improving antenna bandwidth is described using a 6-element Yagi-Uda array as an example. The new approach applies Central Force Optimization, a deterministic metaheuristic, and Variable Z0 technology, a novel, proprietary design and optimization methodology, to produce an array with 33.09% fractional impedance bandwidth. This array’s performance is compared to its CFO-optimized Fixed Z0counterpart, and to the performance of a 6-ele- ment Dominating Cone Line Search-optimized array. Both CFO-optimized antennas exhibit better performance than the DCLS array, especially with respect to impedance bandwidth. Although the Yagi-Uda antenna was chosen to illustrate this new approach to antenna design and optimization, the methodology is entirely general and can be applied to any antenna against any set of performance objectives.展开更多
A six-element Yagi-Uda array is optimally designed using Central Force Optimization (CFO) with a small amount of pseudo randomly injected negative gravity. CFO is a simple, deterministic metaheuristic analogizing grav...A six-element Yagi-Uda array is optimally designed using Central Force Optimization (CFO) with a small amount of pseudo randomly injected negative gravity. CFO is a simple, deterministic metaheuristic analogizing gravitational kinematics (motion of masses under the influence of gravity). It has been very effective in addressing a wide range of antenna and other problems and normally employs only positive gravity. With positive gravity the six element CFO-designed Yagi array described here exhibits excellent performance with respect to the objectives of impedance bandwidth and forward gain. This paper addresses the question of what happens when a small amount of negative gravity is injected into the CFO algorithm. Does doing so have any effect, beneficial, negative or neutral? In this particular case negative gravity improves CFO’s exploration and creates a region of optimality containing many designs that perform about as well as or better than the array discovered with only positive gravity. Without some negative gravity these array configurations are overlooked. This Yagi-Uda array design example suggests that antennas optimized or designed using deterministic CFO may well benefit by including a small amount of negative gravity, and that the negative gravity approach merits further study.展开更多
This paper investigates the effect of adding three extensions to Central Force Optimization when it is used as the Global Search and Optimization method for the design and optimization of 6-elementYagi-Uda arrays. Tho...This paper investigates the effect of adding three extensions to Central Force Optimization when it is used as the Global Search and Optimization method for the design and optimization of 6-elementYagi-Uda arrays. Those exten</span><span><span style="font-family:Verdana;">sions are </span><i><span style="font-family:Verdana;">Negative</span></i> <i><span style="font-family:Verdana;">Gravity</span></i><span style="font-family:Verdana;">, </span><i><span style="font-family:Verdana;">Elitism</span></i><span style="font-family:Verdana;">, and </span><i><span style="font-family:Verdana;">Dynamic</span></i> <i><span style="font-family:Verdana;">Threshold</span></i> <i><span style="font-family:Verdana;">Optimization</span></i><span style="font-family:Verdana;">. T</span></span><span style="font-family:Verdana;">he basic CFO heuristic does not include any of these, but adding them substan</span><span style="font-family:Verdana;">tially improves the algorithm’s performance. This paper extends the work r</span><span style="font-family:Verdana;">eported in a previous paper that considered only negative gravity and which </span><span style="font-family:Verdana;">showed a significant performance improvement over a range of optimized a</span><span style="font-family:Verdana;">rrays. Still better results are obtained by adding to the mix </span><i><span style="font-family:Verdana;">Elitism</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">DTO</span></i><span style="font-family:Verdana;">. An overall improvement in best fitness of 19.16% is achieved by doing so. While the work reported here was limited to the design/optimization of 6-</span></span></span><span><span><span style="font-family:""> </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">element Yagis, the reasonable inference based on these data is that any antenna design/optimization problem, indeed any Global Search and Optimiza</span><span style="font-family:Verdana;">tion problem, antenna or not, utilizing Central Force Optimization as the Gl</span><span style="font-family:Verdana;">obal Search and Optimization engine will benefit by including all three extensions, probably substantially.展开更多
In this paper, we present a broadband quasi-Yagi antenna. Good impedance matching is obtained by using parasitic elements. The antenna has been designed and successfully measured. Experimental results show that the 10...In this paper, we present a broadband quasi-Yagi antenna. Good impedance matching is obtained by using parasitic elements. The antenna has been designed and successfully measured. Experimental results show that the 10 dB return loss bandwidth of this antenna is 50% operating from 2.3 GHz to 3.8 GHz. We obtain very flat gain (around 5 dB) over the entire bandwidth. For the design and optimization of antennas, we use HFSS CAD software from ANSOFT.展开更多
While the Yagi-Uda array has been studied for decades, one issue appears to have received less attention than perhaps it should, namely, the effects on performance of the array’s driven element length and its length-...While the Yagi-Uda array has been studied for decades, one issue appears to have received less attention than perhaps it should, namely, the effects on performance of the array’s driven element length and its length-to-diameter ratio. This paper looks at that question. It shows that decreasing the L/D ratio increases impedance bandwidth, but it may shift the IBW band sufficiently far from the design frequency that other parameters such as gain and front-to-back ratio probably are adversely affected. It also shows that array performance is not relatively independent of element diameters. This paper also investigates the effect of lengthening the driven element, which can substantially improve IBW. Several iterations of a 3-element prototype and improved arrays are modeled with the Method of Moments and discussed in detail. A five step design procedure is recommended and applied to a Genetic Algorithm-optimized 3-element Yagi at 146 MHz. This array exhibits excellent performance in terms of gain, front-to-back ratio, and especially impedance bandwidth (nearly 14% for voltage standing wave ratio ≤ 2:1 with two frequencies at which 50 ? is almost perfectly matched). While the analysis and recommended design steps are applied to cylindrical array elements, which commonly are aluminum tubing for stand-alone VHF-SHF Yagis, they can be applied to other element geometries as well using equivalent cylindrical radii, for example, Printed Circuit Board traces for planar arrays. One consequence of lengthening the driven element while reducing its L/D ratio is that some reactance is introduced at the array feedpoint which must be tuned out, and two approaches for doing so are suggested.展开更多
2018年第14号台风“摩羯”8月14日北上影响山东期间,在台风东南侧鲁中以东地区出现了台风外围螺旋雨带,导致多地出现短时强降水。基于雷达、逐小时降水量、地面、探空、飞机报资料,并利用美国WRF(Weather Research and Forecasting)模...2018年第14号台风“摩羯”8月14日北上影响山东期间,在台风东南侧鲁中以东地区出现了台风外围螺旋雨带,导致多地出现短时强降水。基于雷达、逐小时降水量、地面、探空、飞机报资料,并利用美国WRF(Weather Research and Forecasting)模式进行数值试验,对螺旋雨带的特征及成因进行了研究。研究结果表明:外围螺旋雨带是由多条线状对流系统合并发展而成。台风外围螺旋雨带表现出较明显的前导层状(LS)降水线状中尺度对流系统(MCS)的特征,即线状MCS由多个对流单体组成,对流为后向发展,且存在多次较强线状MCS由侧面并入线状MCS的过程。强降水主要出现在线状对流系统成熟阶段。强降水水汽主要来自850 hPa以下台风周边的近地层大气。对流发生前,山东上空中低层受高温高湿热力不稳定大气控制,风随高度顺时针旋转,有利于对流系统发展。随着台风缓慢北上,500 hPa高空有冷空气向下侵入,在台风东南侧鲁中地区900 hPa以下出现西南风和偏南风、以及偏南风和东南风气流的局地辐合,辐合动力抬升触发不稳定大气能量释放,激发出多条局地线状对流系统。对流系统沿引导气流向北发展,西侧对流系统向北发展同时向东北方向移动,并与前部线状对流系统多次合并加强,逐渐形成细长的外围螺旋雨带。对流发生过程中上升气流明显强于下沉气流,在成熟阶段对流系统的前方低层出现干冷下沉气流,600 hPa以上高度的对流区随高空引导气流快速东移,对流系统迅速减弱。同化AMDAR飞机报资料可以改进WRF模式台风路径和风场预报,准确预报出对流系统的动力触发机制,从而准确预报出台风外围螺旋中尺度雨带的发生。展开更多
利用降水现象仪、自动气象站观测资料和热带气象最佳路径数据集,以移动路径相似的台风“摩羯”(1814)和“烟花”(2106)初入山东南部时引发的大暴雨过程为例,分析移动路径相似的台风在同一地理位置环境下的雨滴谱和积分参数的变化特征,...利用降水现象仪、自动气象站观测资料和热带气象最佳路径数据集,以移动路径相似的台风“摩羯”(1814)和“烟花”(2106)初入山东南部时引发的大暴雨过程为例,分析移动路径相似的台风在同一地理位置环境下的雨滴谱和积分参数的变化特征,结果表明:①两个台风雨滴谱均为单峰型结构,“摩羯”R(雨强)增大主要受D m(质量加权平均直径)增大、次要受lg N w(标准化截距参数对数)增大的影响,而“烟花”R增大受D m增大的影响。②两个台风的D m随R增大逐渐增大,μ(形状因子)和λ(斜率参数)随R增大逐渐减小,“摩羯”lg N w随R增大稍微增大,“烟花”lg N w随R增大基本不变。③“摩羯”对流降水既有大陆性也有海洋性,其形成机制主要是以暖雨-冰相混合和冰相两类为主;“烟花”对流降水以海洋性为主,其形成机制主要是以碰并增长暖云为主,还有少部分暖雨-冰相混合。④应用Z=300R 1.4会稍高估“摩羯”降水而低估“烟花”降水,“摩羯”、“烟花”对流云降水分别为非典型直径控制和浓度-直径混合控制的雨滴谱特征。展开更多
文摘A novel approach for improving antenna bandwidth is described using a 6-element Yagi-Uda array as an example. The new approach applies Central Force Optimization, a deterministic metaheuristic, and Variable Z0 technology, a novel, proprietary design and optimization methodology, to produce an array with 33.09% fractional impedance bandwidth. This array’s performance is compared to its CFO-optimized Fixed Z0counterpart, and to the performance of a 6-ele- ment Dominating Cone Line Search-optimized array. Both CFO-optimized antennas exhibit better performance than the DCLS array, especially with respect to impedance bandwidth. Although the Yagi-Uda antenna was chosen to illustrate this new approach to antenna design and optimization, the methodology is entirely general and can be applied to any antenna against any set of performance objectives.
文摘A six-element Yagi-Uda array is optimally designed using Central Force Optimization (CFO) with a small amount of pseudo randomly injected negative gravity. CFO is a simple, deterministic metaheuristic analogizing gravitational kinematics (motion of masses under the influence of gravity). It has been very effective in addressing a wide range of antenna and other problems and normally employs only positive gravity. With positive gravity the six element CFO-designed Yagi array described here exhibits excellent performance with respect to the objectives of impedance bandwidth and forward gain. This paper addresses the question of what happens when a small amount of negative gravity is injected into the CFO algorithm. Does doing so have any effect, beneficial, negative or neutral? In this particular case negative gravity improves CFO’s exploration and creates a region of optimality containing many designs that perform about as well as or better than the array discovered with only positive gravity. Without some negative gravity these array configurations are overlooked. This Yagi-Uda array design example suggests that antennas optimized or designed using deterministic CFO may well benefit by including a small amount of negative gravity, and that the negative gravity approach merits further study.
文摘This paper investigates the effect of adding three extensions to Central Force Optimization when it is used as the Global Search and Optimization method for the design and optimization of 6-elementYagi-Uda arrays. Those exten</span><span><span style="font-family:Verdana;">sions are </span><i><span style="font-family:Verdana;">Negative</span></i> <i><span style="font-family:Verdana;">Gravity</span></i><span style="font-family:Verdana;">, </span><i><span style="font-family:Verdana;">Elitism</span></i><span style="font-family:Verdana;">, and </span><i><span style="font-family:Verdana;">Dynamic</span></i> <i><span style="font-family:Verdana;">Threshold</span></i> <i><span style="font-family:Verdana;">Optimization</span></i><span style="font-family:Verdana;">. T</span></span><span style="font-family:Verdana;">he basic CFO heuristic does not include any of these, but adding them substan</span><span style="font-family:Verdana;">tially improves the algorithm’s performance. This paper extends the work r</span><span style="font-family:Verdana;">eported in a previous paper that considered only negative gravity and which </span><span style="font-family:Verdana;">showed a significant performance improvement over a range of optimized a</span><span style="font-family:Verdana;">rrays. Still better results are obtained by adding to the mix </span><i><span style="font-family:Verdana;">Elitism</span></i><span style="font-family:Verdana;"> and </span><i><span style="font-family:Verdana;">DTO</span></i><span style="font-family:Verdana;">. An overall improvement in best fitness of 19.16% is achieved by doing so. While the work reported here was limited to the design/optimization of 6-</span></span></span><span><span><span style="font-family:""> </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">element Yagis, the reasonable inference based on these data is that any antenna design/optimization problem, indeed any Global Search and Optimiza</span><span style="font-family:Verdana;">tion problem, antenna or not, utilizing Central Force Optimization as the Gl</span><span style="font-family:Verdana;">obal Search and Optimization engine will benefit by including all three extensions, probably substantially.
文摘In this paper, we present a broadband quasi-Yagi antenna. Good impedance matching is obtained by using parasitic elements. The antenna has been designed and successfully measured. Experimental results show that the 10 dB return loss bandwidth of this antenna is 50% operating from 2.3 GHz to 3.8 GHz. We obtain very flat gain (around 5 dB) over the entire bandwidth. For the design and optimization of antennas, we use HFSS CAD software from ANSOFT.
文摘While the Yagi-Uda array has been studied for decades, one issue appears to have received less attention than perhaps it should, namely, the effects on performance of the array’s driven element length and its length-to-diameter ratio. This paper looks at that question. It shows that decreasing the L/D ratio increases impedance bandwidth, but it may shift the IBW band sufficiently far from the design frequency that other parameters such as gain and front-to-back ratio probably are adversely affected. It also shows that array performance is not relatively independent of element diameters. This paper also investigates the effect of lengthening the driven element, which can substantially improve IBW. Several iterations of a 3-element prototype and improved arrays are modeled with the Method of Moments and discussed in detail. A five step design procedure is recommended and applied to a Genetic Algorithm-optimized 3-element Yagi at 146 MHz. This array exhibits excellent performance in terms of gain, front-to-back ratio, and especially impedance bandwidth (nearly 14% for voltage standing wave ratio ≤ 2:1 with two frequencies at which 50 ? is almost perfectly matched). While the analysis and recommended design steps are applied to cylindrical array elements, which commonly are aluminum tubing for stand-alone VHF-SHF Yagis, they can be applied to other element geometries as well using equivalent cylindrical radii, for example, Printed Circuit Board traces for planar arrays. One consequence of lengthening the driven element while reducing its L/D ratio is that some reactance is introduced at the array feedpoint which must be tuned out, and two approaches for doing so are suggested.
文摘2018年第14号台风“摩羯”8月14日北上影响山东期间,在台风东南侧鲁中以东地区出现了台风外围螺旋雨带,导致多地出现短时强降水。基于雷达、逐小时降水量、地面、探空、飞机报资料,并利用美国WRF(Weather Research and Forecasting)模式进行数值试验,对螺旋雨带的特征及成因进行了研究。研究结果表明:外围螺旋雨带是由多条线状对流系统合并发展而成。台风外围螺旋雨带表现出较明显的前导层状(LS)降水线状中尺度对流系统(MCS)的特征,即线状MCS由多个对流单体组成,对流为后向发展,且存在多次较强线状MCS由侧面并入线状MCS的过程。强降水主要出现在线状对流系统成熟阶段。强降水水汽主要来自850 hPa以下台风周边的近地层大气。对流发生前,山东上空中低层受高温高湿热力不稳定大气控制,风随高度顺时针旋转,有利于对流系统发展。随着台风缓慢北上,500 hPa高空有冷空气向下侵入,在台风东南侧鲁中地区900 hPa以下出现西南风和偏南风、以及偏南风和东南风气流的局地辐合,辐合动力抬升触发不稳定大气能量释放,激发出多条局地线状对流系统。对流系统沿引导气流向北发展,西侧对流系统向北发展同时向东北方向移动,并与前部线状对流系统多次合并加强,逐渐形成细长的外围螺旋雨带。对流发生过程中上升气流明显强于下沉气流,在成熟阶段对流系统的前方低层出现干冷下沉气流,600 hPa以上高度的对流区随高空引导气流快速东移,对流系统迅速减弱。同化AMDAR飞机报资料可以改进WRF模式台风路径和风场预报,准确预报出对流系统的动力触发机制,从而准确预报出台风外围螺旋中尺度雨带的发生。
文摘利用降水现象仪、自动气象站观测资料和热带气象最佳路径数据集,以移动路径相似的台风“摩羯”(1814)和“烟花”(2106)初入山东南部时引发的大暴雨过程为例,分析移动路径相似的台风在同一地理位置环境下的雨滴谱和积分参数的变化特征,结果表明:①两个台风雨滴谱均为单峰型结构,“摩羯”R(雨强)增大主要受D m(质量加权平均直径)增大、次要受lg N w(标准化截距参数对数)增大的影响,而“烟花”R增大受D m增大的影响。②两个台风的D m随R增大逐渐增大,μ(形状因子)和λ(斜率参数)随R增大逐渐减小,“摩羯”lg N w随R增大稍微增大,“烟花”lg N w随R增大基本不变。③“摩羯”对流降水既有大陆性也有海洋性,其形成机制主要是以暖雨-冰相混合和冰相两类为主;“烟花”对流降水以海洋性为主,其形成机制主要是以碰并增长暖云为主,还有少部分暖雨-冰相混合。④应用Z=300R 1.4会稍高估“摩羯”降水而低估“烟花”降水,“摩羯”、“烟花”对流云降水分别为非典型直径控制和浓度-直径混合控制的雨滴谱特征。
