有耗介质中单极天线的场分布和SAR图

用一段刚性同轴线制作的微细单极天线在医疗上已得到广泛应用。本文给出了单极天线在有耗介质中的近场分布的数值解，进而在有耗介质中测定了温度分布和ＳＡＲ图，利用近场分布计算的ＳＡＲ图和测定和ＳＡＲ图基本相符。     

水冷式微波偶极子辐射器在生物介质中的SAR分布计算

本文从电磁场理论模型出发，分析地腔内水冷式微波偶极子辐射器在生物介质中的近场辐射特性，计算得到有水冷时的比吸收率（ＳＡＲ）分布形态。与无水冷时的ＳＡＲ分布比较表明，水冷可改善热区分布，增加治疗深度。该结果与工程经验和临床实际基本相符。     

平板宽带单极与偶极天线的全波分析

采用时域有限差分法（FDTD）计算圆盘天线及宽带变形vivaldi天线的输入阻抗及方向图。利用镜像原理得到三角形单极、圆盘单极天线的输入阻抗。采取激励源区的准静态模型在保证精度的同时又无须将复杂的具体馈电结构建模，三角形单极天线和圆盘单极天线的计算结果与有关文献的比较验证了该方法具有准确、实用性强等优点，对宽带变形vivaldi天线FDTD分析得到电流分布及输入阻抗，经傅立叶变换由近场值得到天线远场方向图，结果表明变形vivaldi天线具有输入阻抗和方向图的宽带特性。     

一种适于机载前斜视SAR成象处理的Chirp Scaling算法

Ｃｈｉｒｐ Ｓｃａｌｉｎｇ算法是一种高效、高精度的ＳＡＲ成象处理算法，算法解决了在宽天线波束或者天线高斜视角情况下获得高分辨力图象的问题。本文在Ｃｈｉｒｐ Ｓｃａｌｉｎｇ算法的基础上，提出采用新的结构和新的相位函数来接纳机载ＳＡＲ成象处理所需的运动补偿相位，使得Ｃｈｉｒｐ Ｓｃａｌｉｎｇ算法成为机载前斜视ＳＡＲ的一种实用的、高效算法。本文给出了一幅采用该算法处理的德国宇航院（ＤＬＲ）的Ｅ－ＳＡＲ图     

天线/RCS近场测量系统的研究

给出了由ＨＰ８５３０Ｂ组成的天线／ＲＣＳ近场测量系统的有关技术指标。利用该系统对典型天线进行了分析测量。结果表明,所研制的近场系统可提供各种天线的精确测量结果。     

天线尺寸对冲激信号SAR方位向积累的影响

该文分析了冲激信号／极窄脉冲ＳＡＲ成像系统的天线在辐射与接收时存在的时－空耦合问题,结合冲激信号ＳＡＲ成像方法反向投影法（ＢＰ）,本文在时域上分析了天线尺寸对ＳＡＲ６方位向积累的影响,给出了方位向积累与天线尺寸的定量关系,最后给出了关于超宽带ＳＡＲ天线设计及发射信号参数选择的有用的结论。     

机载合成孔径雷达系统的C波段固态双极化T／R组件

以相控阵天线为基础，在合成孔径雷达中使用分布式电源，这一作法对系统操作提供了新的可能性，为未来采用固态发射机并以电子方式操纵相控阵天线的空载ＳＡＲ系统作了准备，建立了ＰＨＡＲＵＳ系统。     

未来X波段SAR的设计

目前，使用有源相控阵天线的未来Ｘ波段ＳＡＲ雷达正在研制开发之中。本文描述了这种ＳＡＲ系统的一般设计考虑，并对拟议中的下一代ＳＡＲ系统的设计提出了一些设想。     

基于GPS干涉仪的机载合成孔径雷达平台姿态控制与运动补偿的研究

分析了ＧＰＳ干涉仪用于飞机姿态测量的原理，给出了四天线的机载合成孔径雷达（ＳＡＲ）平台的ＧＰＳ测姿系统，并在此基础上，结合ＳＡＲ平台的姿态控制要求，给出了采用ＧＰＳ／ＩＮＳ组合的方法树ＳＡＲ平台进行实时的姿态控制和运动补偿的方法。     

腔体内单极天线的电流分布及输入阻抗的研究

本文利用矩量法与并矢格林函数相结合,研究了腔体内单极天线(或探针)的电流分布及输入阻抗。通过选择分段正弦基函数,不但使矩阵阶数大大减小,而且改善了矩阵元素级数的收敛性。本文的数值结果还给出了腔体内有耗介质对输入阻抗的影响。     

The determination of the electromagnetic field and SAR pattern ofan interstitial applicator in a dissipative dielectric medium

The spatial distribution of microwave energy absorbed per unit mass (the specific absorption rate or SAR) in biological tissue is calculated for a class of interstitial antennas. The insulated interstitial applicator is simulated as an asymmetrically drive antenna. An expression for the electric field intensity near the antenna is derived and calculated by direct numerical evaluation of a surface integral over the insulation. The predicted SAR patterns obtained using the calculated electric field intensity and the tissue conductivity agree very well with the measured SAR distributions around three different applicators in muscle-equivalent phantoms     

The calculated and measured temperature distribution of a phasedinterstitial antenna array [invasive applicators]

The power deposition pattern of four antennas, positioned on the corners of a 2-cm square array with different driving phases, is computed under the assumption of negligible coupling between the antennas. The spatial SAR (specific absorption rate) distribution is calculated by modeling each interstitial applicator as an insulated, asymmetric dipole. For comparison with the heating patterns measured by a thermal video system, the calculated SAR distributions are converted into temperature patterns through an electric network simulation of the heating in artificial muscle tissue. At each nodal point of a grid in the thermal system, the absorbed microwave power (or SAR times density), thermal resistivity, heat capacitance, and temperature are simulated, respectively, as current source, electrical resistance, electrical capacitance and potential. Therefore, solving the equivalent electric network on a computerized simulation routine (SPICE) yields the temperature distribution. In both the axial and transverse planes, the resulting temperature distributions from the antenna array, with various driving phases, agree very well with the measured temperature patterns     

热疗用微波辐射器长度对其性能影响的理论分析

本文分析了一种带冷却水的用于人体体腔内部热疗的绝缘偶极子微波辐射器的特性。利用辐射器上的电流分布导出辐射阻抗和驻波经与辐射器长度的关系式，探讨了体腔周围被加热生物组织中分布的比吸收率，进而根据热平衡方程得到辐射器长度对温度场分布的影响，为体腔内部热疗用微波辐射器的设计提供了理论依据。     

An insulated dipole applicator for intracavitary hyperthermia

Specific absorption rate (SAR) patterns for an insulated sleeve dipole applicator, operating at 433 MHz, were measured by infrared thermography. The applicator was modeled using classical transmission-line theory, and experimental and theoretical results were compared. In general, agreement between measured and calculated SAR values was good. However, at the antenna feedpoint, the measured values were appreciably higher than the calculated values. This indicates that inclusion of junction effects would improve the model     

Electromagnetic and thermal models of a water-cooled dipoleradiating in a biological tissue

An insulated, water-cooled dipole, radiating in a biological tissue, is analyzed with a theoretical electromagnetic and thermal model. The SAR and temperature distributions are calculated taking into account the effect of the water flowing inside the applicator. The steady-state temperatures in a dissipative medium, interacting with the dipole, are evaluated for several thicknesses of the external casing, water temperatures and blood perfusions. A correct design of the external casing thickness and a proper choice of the temperature and flow velocity of water allows to control the wall temperature of the applicator within physiological limits. The influence of the blood perfusion on the temperature distribution is investigated.     

SAR CHARACTERIZATION OF FOCUSED PLANAR ARRAY OF WATER-LOADED MODIFIED BOX-HORNS FOR HYPERTHERMIA

A 4×4 planar array of modified box-horns as a microwave hyperthermia applicator is theoretically studied to characterize power deposition (SAR) in heating tissue (muscle) at 2450 MHz. A modified box-horn is a novel improved version of conventional box-horn in which horn exciting the box waveguide is flared in both E-and H-planes. Modified box-horn supports TE₁₀ and TE₃₀ modes. The amplitude distribution over the H-plane of the box-horn aperture is a closer approximation to the uniform distribution. It is proposed that the interior of the box-horn be filled with water to provide a better impedance match to biological tissue. By applying Fresnel-Kirchhoff scalar diffraction field theory, the expression for electric field in heating region is derived and distribution of specific absorption rate (SAR) in that region due to planar array of modified box-horns as direct contact applicator is evaluated at 2450 MHz. The results of modified box-horn array are compared with those of a single modified box-horn operating at the same frequency. Results demonstrate that planar array of modified box-horns offers improvement in SAR distribution and penetration depth. It is shown that by changing the phase and amplitude of excitation of the modified box-horns of the array, the relative amplitude and position of the hot spot can be changed. The present analysis is validated through the results obtained by plane wave spectral technique.     

Evaluation of a semi-cylindrical solenoid as an applicator forradio-frequency hyperthermia

A modified solenoid having a semi-circular cross section is evaluated as an applicator for radio-frequency heating of biological materials. The operating efficiency of this applicator and the distribution of the electric field established within a simulated biological sample are determined for a number of modes of excitation. It is shown that uniform heating to a substantial depth is possible at efficiencies in excess of 80 percent.     

Computer-aided design of two dimensional electric-type hyperthermiaapplicators using the finite-difference time-domain method

A hyperthermia applicator design tool consisting of a finite-difference time-domain (FDTD) technique in combination with a graphical display of electric fields and normalized linear temperature rise is described. This technique calculates, rather than assumes, antenna current distributions; it includes mutual interactions between the body and the applicator, and it calculates driving-point impedance and power delivered to the applicator. Results show that the fundamental limitation of 2-D electric-type applicators is overheating of the fat by normal components of the electric field, which exist because of near fields and capacitive coupling with the muscle. Two factors which contribute to the capacitance are the muscle conductivity and the small antenna size in air. Two examples of applicators designed to avoid fat overheating are described: a 27-MHz segmented dipole for heating large tumors to 7 cm depth, and a 100-MHz dipole for small tumors to 5 cm depth. The first uses a water bolus, and the second uses a water bolus with low-permittivity strips to reduce normal fields at the antenna ends. The results of this study describe fundamental limitations of electric field applicators, and illustrate the use of a powerful applicator design tool that allows rapid evaluation of a wide range of ideas for applicators which would require months and years to test experimentally.     

A memory efficient method of calculating specific absorption ratein CW FDTD simulations

Specific absorption rate (SAR) distributions in man models are often calculated using the finite-difference time-domain (FDTD) method. The traditional method of calculating SAR requires calculation and storage of the three electric field components in each cell and is therefore very time- and memory-intensive. A new algorithm, based on the mass-normalized time-averaged energy distribution, is presented here. This new method of calculating SAR requires 1/6 of the memory and a small fraction of the computer time of the traditional method. The accuracy of the two methods is shown to be virtually identical. In addition to improving the efficiency of SAR distribution calculations, the memory requirements are virtually eliminated for calculations of layer-averaged or organ-averaged SAR