The Effects of Driving Frequency and Antenna Length on Power Deposition Within a Microwave Antenna Array Used for Hyperthermia

The theory of the linear, insulated antenna embedded in an electrically dense medium is applied to microwave antennas used for hyperthermia cancer therapy. The pattern of power deposition is computed for a square array of four antennas with a side length of 3 cm under the assumption of no coupling among antennas. The driving frequency is set to seven values between 300 and 915 MHz, and the antenna halflength is set to three values: 3 cm, 6 cm, and the resonant value.     

一种覆盖半空域相控阵天线方向图计算

介绍棱台形相控阵天线在不同空间位置的天线方向图分析计算方法，通过建立数学模型和理论分析，计算的结果与实测结果非常一致，从而为相控阵天线的阵列单元初始相位设置和相位控制提供了设计依据。     

SAR Patterns from an Interstitial Microwave Antenna-Array Hyperthermia System

In recent years, a number of groups have been investigating the use of interstitial microwave antenna-array hyperthermia (IMAAH) systems for the treatment of superficial and deep-seated tumors. A critical parameter in any hyperthermia system is the SAR (specific absorption rate) pattern, which gives information about the energy absorption in the tumor and surrounding tissue. In this paper, we compare the theoretical and measured values of the SAR distribution for an array of four 915-MHz antennas implanted on the corners of a 2-cm square array. The overall length of the antennas was assumed to be 7 cm theoretically and was either 6 or 7 cm for the measurements. In general, there was good agreement between the theoretical predictions and the experimental results. In particular, both theory and experiment demonstrated that the maximum SAR occurred in the junction plane of the antenna array and at the center of the square array. Similarly, both showed that the Iongitudinal extent of the heating pattern is about 5 cm for a single antenna, but closer to 3 cm for an array where the Iongitudinal extent is defined by the length in the longitudinal direction where the SAR is greater than 50 percent of the maximum. The experiments showed that the SAR patterns were quite reproducible, and that the use of double stub tuners to minimize the reflected power for each antenna resulted in poorer SAR patterns due to phase variations created by the tuners. However, the use of an attenuator with each antenna to equalize the maximum SAR from each antenna did improve the SAR distributions slightly.     

基于方向图和多普勒相关系数的天基阵列SAR通道相位误差补偿方法

随着对地观测技术的发展,要求SAR系统能够同时实现高分辨率和宽测绘带,天基阵列多通道SAR结合数字波束形成(DBF)技术为解决该问题提供了很好的思路,但各个通道之间相位误差会很大程度上降低DBF的性能,常规通道误差补偿方法估计精度不足,应用场景受限。针对上述问题,该文提出一种基于方向图和多普勒相关系数的天基阵列SAR通道相位误差补偿方法,不仅利用天线方向图先验信息,还充分利用场景不同多普勒相关性信息,通过最小化天线方向图和多普勒的组合差异,实现对通道之间相位误差的估计。结合RADAR-SAT数据的仿真试验结果验证了该算法的有效性。     

基于遗传算法的任意布阵天线方向图优化

建立了一种通用的适应度函数式，通过遗传算法对八元阵优化，逼近二项式分布和切比雪夫分布，验证了算法的正确性。通过对八元阵方向图不同目标的优化，说明该算法及适应度函数的设计对任意布阵天线方向图多目标优化的有效性。     

Antenna Pattern Correction Technique Based on an Adaptive Array Algorithm

An antenna pattern correction technique is presented that is based on an adaptive array algorithm. In the method, the antenna pattern of the antenna under test (AUT) is measured several times at different positions in the quiet-zone. The corrected antenna pattern is obtained by taking a weighted average of the measured patterns. An array synthesis algorithm is employed for obtaining the averaging weights at each rotation angle of the AUT. The weights are adapted specifically for a given AUT. The adaptive array correction technique is demonstrated in a hologram based compact antenna test range (CATR) at 310 GHz with both a synthetic antenna and a physical test antenna. For verification, the accuracy provided by the adaptive array correction technique is compared to that provided by uniform weighting.     

遗传算法在阵列天线方向图综合中的应用

遗传算法是一种高效的搜索算法。本文采用遗传算法对18元天线阵列方向图进行综全优化设计，并与用Woodward法得到的结果进行了比较。     

相位和差单脉冲相控阵天线方向图仿真与性能分析

以相位和差相控阵为例对和差方向图仿真进行研究,给出了相位和差单脉冲相控阵天线方向图仿真模型。以幅度加权为例,给出了和差方向图的数值仿真结果,并分析了方向图波瓣分布特点。对相位和差相控阵单脉冲测角原理、测角性能曲线和测角误差原因进行了分析。天线方向图计算机数值仿真方法可以为天线系统设计和天线参数测试提供参考。实践证明该仿真方法是非常有效的,并在实际天线测试和性能分析中得到应用。     

A Computer Calculation of the Far Field Radiation Pattern of an Antenna Array

A computer program has been investigated and developed for the calculation of the far field radiation pattern of an antenna array. This paper contains an IBM 360/65 program for the calculation of the far field pattern with accuracy checks on the pattern obtained by using radio stations KXIC and WSUI, both located in Iowa City, Iowa, as assumed normals. Two theories of solving the far field calculation problem with the SDS-92/TR-48 hybrid computer are submitted.     

低频UWB SAR天线方向图的校准

低频UWB SAR系统具有较大的方位向处理角，因此天线方向图对系统性能的影响不能忽略。本文首先给出接收信号空间和场景空间的对应关系，结合成像模型定性地讨论了天线方向图对系统冲激响应的影响。在实际条件下考虑了距离校正因子、杂波、噪声和目标响应等因素，利用实际数据对天线方向图做了定量分析。最后结合成像处理模型，使校正后的图像质量得到提高。     

量化相移对阵列天线的分析

研究了数字移相器提供的量化相移对正六边形相控阵天线扫描方向图的影响。使用一定精度移相器可降低馈源阵列的量化误差,而天线的方向图和增益只有微小的变化。分别选择2位、4位和6位移相器,比较采用连续相移和不同精度的量化相移时,天线辐射方向图的变化。通过对比分析可选择合适的数字移相器。     

低频USAR天线方向图的校准

低频U SAR系统具有较大的方位向处理角,因此天线方向图对系统性能的影响不能忽略.本文首先给出接收信号空间和场景空间的对应关系,结合成像模型定性地讨论了天线方向图对系统冲激响应的影响.在实际条件下考虑了距离校正因子、杂波、噪声和目标响应等因素,利用实际数据对天线方向图做了定量分析.最后结合成像处理模型,使校正后的图像质量得到提高.     

Synthesis and Validation of a Cu Meta-BasedWideband Microwave Absorber on an Antenna Array

Meta copper (Cu) material called nanotwin crystalline copper metal (C2101, Kopu Tharma Loham) fabricated on the basis of ancient Indian metallurgical techniques has been originally used here as an absorbing material. The research attempted here is to explore the electromagnetic properties experimentally over a wide range of frequency covering X, Ku, K and Ka bands. The dielectric constant and loss tangent of Cu meta material are high in the X range making it a good candidate for the successful design of an absorber. Along with that, the melting point of Cu meta is also increased to 1135°C which is otherwise 1085°C as per international copper standards, hence making the absorber thermally stable. The particle size of Cu meta material, when measured with the x-ray diffraction method, is decreased from 50 μm to 100 nm, placing it in a nanomaterial category. An absorption bandwidth of 35.58 GHz is obtained, ranging from 1 GHz to 36.58 GHz. After testing, the absorber is finally integrated with a two-element rectangular patch array for substantial applicability. The radiation pattern plot shows a remarkable reduction in side lobe level of the array from 3.737 dB to 1.158 dB after placing the Cu meta material absorber. The beam width narrows down from 70° to 44° with a slight increase in the amplitude of the major lobe from 5.494 dB to 6.341 dB while retaining the pattern symmetry.     

大规模阵列天线方向图成形预编码性能仿真*

大规模阵列天线技术可用于解决下一代无线通信的频谱有效性和功率有效性问题,对大规模阵列天线成形性能进行了仿真,得出了天线数目增加对均匀线阵方向图成形的影响,并通过计算比较了不同规模天线阵列的波瓣宽度,并仿真分析了不同规模均匀圆阵的方向图,最后研究了信道估计准确度对大规模天线阵列方向图成形性能的影响,仿真得出了信道估计矩阵存在误差时阵列天线方向图的变化。     

基于遗传算法的阵列天线方向图综合技术

提出了一种改进的遗传算法,该算法采用了简单灵活的十进制编码,并对遗传参数进行了一些改进,使搜索效率有了较大的提高,有效地避免了早期收敛。应用这种方法,成功地实现了阵列天线的方向图综合。良好的计算结果表明遗传算法是目前求解此类问题的有效方法。     

高频雷达天线阵的相位噪声分析

高频雷达天线阵受风的作用会产生随机晃动,导致发射和接收信号的相位噪声一定程度的恶化,从而降低高频雷达系统的目标检测性能。针对高频雷达发射天线阵相位噪声恶化的情况,从天线单元和反射网2个主要方面对恶化原因展开了分析,得出了相位噪声恶化原因为天线单元阻抗变化和反射网晃动所引起的信号相位调制结论。根据结果分析,提出了相应的改进方案,并对改进后的天线阵相位噪声进行了测试,测试结果表明相位噪声比改进前降低了10 dB。     

共形微带天线相控阵阵列的仿真优化设计

针对平面阵列天线的诸多缺点,设计了适用于工作频段34～36GHz的共形相控阵天线。依据共形微带天线阵列的设计思想及方法,选取了柱面微带贴片天线做阵列辐射单元,通过CST软件对天线的几何尺寸进行仿真和优化设计,得出了共形天线阵的各种性能指标。仿真结果表明：在该毫米波波段下设计的共形相控天线具有优良的性能,为今后设计出最优的天线阵提供了依据。     

星载SAR相控阵天线一体化热设计

介绍了星载相控阵天线一体化热设计的方法,利用不同的仿真软件分析了天线热分布、结构变形等情况,通过建立热变形对天线电性能影响的仿真模型,验证热设计是否能满足电性能要求,并以电性能最优为目标实现最优的热设计。最后,针对星载SAR天线产品验证文中设计方法的工程可实现性。     

相位误差对相控阵天线影响分析与改进

为减少相位误差对相控阵天线的影响,介绍了相控阵天线数字移相器相位量化误差产生的原理,分析了相位量化误差对相控阵天线波束指向精度和天线波束性能的影响。为改善这一情况,提出采用递推比较补偿馈相法代替传统的确定性馈相法,通过对2种方法进行比较分析,证明在不改变硬件的条件下,递推比较补偿馈相法能够减少相位量化误差的影响,降低波束指向误差的极大值和均方差,提高相控阵天线的指向精度和波束性能。     

阵列天线的切比雪夫方向图综合

阵列天线是指由多个离散的辐射元,按一定规律排列组成的天线系统.其具有高增益,强方向性,主瓣可控等特性.文中研究了利用切比雪夫法对阵列天线输入不同参数:馈源单元数N,馈源间距d,副瓣电平SLL,得出参数改变对阵列天线方向图的综合影响,通过工程示例论证出切比雪夫法用于方向图综合的优缺点.为切比雪夫法用于天线方向图综合比较提供了一种有效的参考方法.