Synchronized microwave energy generation by harmonic filtering

The theoretical and practical aspects of generating synchronized microwave harmonic energy using a dc step source feeding a modified pulse forming network are presented. The results indicate that although the suggested technique introduces some degradation in the build-up time of the output wave packet, it remains economical for generating, at least, third-harmonic energy.     

Axiomatic geometry of conditional models

We formulate and prove an axiomatic characterization of the Riemannian geometry underlying manifolds of conditional models. The characterization holds for both normalized and nonnormalized conditional models. In the normalized case, the characterization extends the derivation of the Fisher information by Cencov while in the nonnormalized case it extends Campbell's theorem. Due to the close connection between the conditional I-divergence and the product Fisher information metric, we provides a new axiomatic interpretation of the geometries underlying logistic regression and AdaBoost     

Absorption by the tails of the oxygen microwave resonances at atmospheric pressures

A variety of methods axe available for calculating atmospheric absorption of microwaves and millimeter waves by oxygen resonances. We compare these methods for the absorption by the tails of the 60 GHz band, the line at 118.75 GHz, and the nonresonant oxygen absorption. For practical, atmospheric calculations the tails of the 60 GHz band consist of frequencies less than 48 GHz and greater than 71 GHz. Gordon's method is selected as being the simplest and most reliable for calculating the absorption by the tails of the 60 GHz band. The interference parameter of the 118.75 GHz line can be chosen such that its high-frequency tail approaches zero as frequency increases.     

RF and microwave energy hots up

Radiofrequency and microwave heating spanning the frequency range 10-3000 MHz has, long since its birth just after the Second World War, embraced areas such as industry, catering, domestic and medicine. The author shows that the advantages of RF and microwaves (such as volumetric heating, rapid and selective heating, compactness of equipment and ease of operation) offer sound economic alternative heating techniques     

Absorption at high microwave power by large-area Tl-basedsuperconducting films on metallic substrates

Microwave surface resistance measurements have been made on large-area Ti-Ba-Ca-Cu-O thick films magnetron-sputtered onto oriented Ag alloy substrates by replacing the end wall of an 18 GHz TE₀₁₁ mode Cu cavity with the superconducting film. The best surface resistance values obtained are 4 and 14 mΩ at 10 K and 77 K, respectively; corresponding Cu values are 8 and 21 mΩ. The dependence of the surface resistance on microwave power was measured in a similar way except that a Nb cavity was used instead of a Cu cavity. Typically, the surface resistance of the film begins to rise in 1-10 Oe of microwave field and saturates in 20-60 Oe. A model is presented relating the observed saturation to critical penetration of Josephson junctions. Films exhibiting the highest degree of c-axis texturing show the weakest dependence of surface resistance on power and also exhibit the sharpest transition to the superconducting state as measured at high frequency     

Absorption and dispersion of low-loss dielectrics measured with microwave transient radiation

Measurements of the frequency-dependent loss and dispersion of low-loss dielectrics, between 10 and 130 GHz, are presented. The data are obtained from a single experiment using the picosecond transient radiation from optoelectronically pulsed integrated antennas.<>     

Space-mapping optimization of microwave circuits exploitingsurrogate models

A powerful new space-mapping (SM) optimization algorithm is presented in this paper. It draws upon recent developments in both surrogate model-based optimization and modeling of microwave devices, SM optimization is formulated as a general optimization problem of a surrogate model. This model is a convex combination of a mapped coarse model and a linearized fine model. It exploits, in a novel way, a linear frequency-sensitive mapping. During the optimization iterates, the coarse and fine models are simulated at different sets of frequencies. This approach is shown to be especially powerful if a significant response shift exists. The algorithm is illustrated through the design of a capacitively loaded 10:1 impedance transformer and a double-folded stub filter. A high-temperature superconducting filter is also designed using decoupled frequency and SMs     

On the potential energy output of a system transporting the electromagnetic energy by means of microwave beams

It is proposed to use such distribution of the radiated field in a wireless energy transportation system that is similar to the distribution of the modified TEM₁₀ mode generated by a laser. It is shown that, in this case, the product of the aperture efficiencies of radiating and receiving apertures substantially exceeds the value of this parameter corresponding to the uniform and optimum Gaussian field distributions. It is found that, in this case, the potential energy output of the energy transportation system increases approximately by a factor of three and can reach about 15 GW at a wavelength of 5 cm for the antenna and rectenna diameters of 1.0 km and 7.4 km, respectively.     

Prediction models and measurements of microwave signals scatteredfrom buildings

The planning of urban microwave communication systems must consider the harmful interference these systems cause to existing links, and vice versa. Site shielding is an interference reduction technique wherein a building is used deliberately to shield a radio terminal from interfering signal. The site-shielding factor (SSF) is, however, influenced by the arrival of interference on paths caused by reflection and scatter from nearby buildings. Prediction models are needed to estimate the effects arising from the scatter. The paper develops prediction models based on a plane reflector and discusses experimental measurements aimed at the validation of these models. The paper describes the results of the initial stage of a continuing investigation into building scatter aimed at the formulation of a prediction procedure for site shielding suitable for radio system planning and coordination     

微波传能发射系统电磁辐射安全性研究

无线传能系统工作时在周围空间会激发高频电磁场,因此对无线传能系统有较高的电磁兼容性指标要求.文中通过对无线微波传能系统发射天线周围环境的电磁辐射进行建模和分析,以及微波传能基站对周围环境的电磁影响,研究了无线微波传能发射端周围空间电磁辐射的安全性.发射功率为500 W时,通过计算人体头部的比吸收率值,根据国际射频暴露的安全导则,基于理论分析和仿真实验界定了人体电磁暴露的安全区域,划定基站天线主波束、旁瓣、后瓣的安全距离分别为25 m、3 m、2 m,并给出了无线微波传能基站部署的参考方案,对于无线微波传能的实际应用具有重要的参考意义.     

Intercomparison of microwave radiative transfer models forprecipitating clouds

An intercomparison of microwave multiple scattering radiative transfer codes used in generating databases for satellite rainfall retrieval algorithms has been carried out to ensure that differences obtained from retrieval techniques do not originate from the underlying radiative transfer code employed for the forward modeling. A set of profiles containing liquid water and ice contents of cloud and rain water as well as snow, graupel and pristine ice were distributed to the participants together with a black box routine providing Mie single scattering, atmospheric background absorption and surface emissivity. Simulations were to be carried out for nadir and off-nadir (53.1°) observation angles at frequencies between 10 and 85 GHz. Among the radiative transfer models were two-stream, multiple stream and Monte Carlo models. The results showed that there were two major sources of differences between the codes. 1) If surface reflection/emission was considered isotropic, simulated brightness temperatures were significantly higher than for specular reflection and this effect was most pronounced at nadir observation and over ocean-type surfaces. 2) Flux-type models including delta-scaling could partially compensate for the errors introduced by the two-stream approximation. Largest discrepancies occurred at high frequencies where atmospheric scattering is most pronounced and at nadir observation. If the same surface boundary conditions, the same multiple-stream resolution and the same scaling procedures are used, the models were very close to each other with discrepancies below 1 K     

蒸发波导模型与微波超视距传播试验对比

海洋蒸发波导是实现近海面超视距电波传播的重要环境,利用蒸发波导模型和电波传播数值算法是获取路径损耗的主要途径.基于海上平台约7个月测量的水文气象参数,对比了Paulus提出的PJ模型和美国海军研究生院(Naval Postgraduate School,NPS)提出的NPS模型,同时利用约1个月的海上超视距传播测试数据...     

Comparison of two microwave radiobrightness models and validationwith field measurements

This paper compares microwave brightness temperature (T_B) estimated by two radiobrightness models: a multilayer coherent radiative transfer (CRT) model and a single-layer Fresnel reflectance model. Two dielectric mixing schemes were used along with the models to calculate permittivity (real part of the dielectric constant). Model T_B and permittivity estimates were compared and validated against Huntsville, AL 1998 field experiment measurements. Model differences can be attributed to the mixing scheme, the radiobrightness model, or the vertical profile representation. Two sets of simulations were performed to quantify the sources of variation, one using observed son temperature and moisture profiles as input, and another using uniform profiles. Using uniform profiles, systematic differences in permittivity estimated by the mixing schemes resulted in T_B differences as large as 15 K. However, for uniform profiles, differences in T_B estimated by the radiobrightness models for a given permittivity value were less than 2 K. For cases using observed profiles, near-surface drying of the profiles resulted in T_B values from the CRT model 6-10 K higher than estimates from the Fresnel model, which determines T_B based on 0-5 cm mean moisture and temperature. Therefore, the major sources of T_B variations were the dielectric mixing scheme and the shape of the near-surface moisture profile. No radiobrightness/mixing scheme combination exhibited superiority across all plots and times     

Absorption of energy from a large amplitude electromagnetic pulse by a collisionless plasma

A series of experiments in which an electromagnetic pulse (EMP) is propagated through a nitrogen plasma are discussed. The pulse has the general characteristics of an EMP. The pulse is observed as it emerges from the plasma as a function of the plasma parameters. As the electron number density increases, it is found that energy is increasingly absorbed from the pulse, a process due to joule heating. In addition, at higher number densities, ringing of the pulse occurs. The nitrogen pressure in these experiments is sufficiently low so that collisions play only a minor role. Also developed is a theoretical model based on the fluid transport equations. This theory predicts that the electrons of the plasma are attaining a temperature of about 15 eV in that part of the system where the dc magnetic field is about 80 G. More importantly, it is able to predict the output pulse quite well under the conditions that the ambient nitrogen pressure and the electron number density are low. The theory appears to fail as these parameters are increased.     

Stochastic geometry modeling and energy efficiency analysis of millimeter wave cellular networks

Current wireless networks face unprecedented challenges because of the exponentially increasing demand for mobile data and the rapid growth in infrastructure and power consumption. This study investigates the optimal energy efficiency of millimeter wave (mmWave) cellular networks, given that these networks are some of the most promising 5G-enabling technologies. Based on the stochastic geometry, a mathematical framework of coverage probability is proposed and the optimal energy efficiency is obtained with coverage performance constraints. Numerical results show that increasing the base station density damages coverage performance exceeding the threshold. This work demonstrates an essential understanding of the deployment and dynamic control of energy-efficient mmWave cellular networks.     

Experimental models for the evaluation of microwave biological effects

The theoretical and empirical approaches to biological effects of microwaves are discussed. The bioeffects should be considered as a chain of events: primary interaction analyzed in terms of biophysics and early direct, early indirect, late (delayed) effects analyzed in terms of physiology. Thermal balance experiments are discussed pointing out the necessity to take unequal deep body heating by microwaves into account. The use of physiologic rhythms in microwave bioeffects experimentation is presented. Possible use of pharmacodynamic approaches (simultaneous use of drugs and microwave exposure) is outlined. Possible ways of developing biological response microwave dosimetry are indicated. Unexplained effects are pointed out and the necessity of further experiments to clarify these stressed. Some possible experimental models are presented.     

Efficient electromagnetic optimization of microwave filters and multiplexers using rational models

A method is presented for the efficient optimization of microwave filters and multiplexers designed from an ideal prototype. The method is based on the estimation of a rational function adjusted to a reduced number of samples of the microwave device response obtained either through electromagnetic analysis or measurements. From this rational function, a circuital network having the previously known topology of the microwave device is synthesized and compared to a circuital network with the desired response but including nonidealities. All of the process of analysis and model extraction can be seen as a model function that relates the physical parameters of the microwave device with the extracted circuital network parameters. Then, the error vector of the circuital parameters is used to generate a correction vector of the physical parameters through an estimation of the inverse of the Jacobian matrix of the complete model function. The Jacobian estimation is updated at each iteration of the optimization process with no need for additional evaluations of the model function. Two numerical examples of the proposed technique corresponding to the synthesis of a filter and a diplexer are presented, demonstrating the increased efficiency of the proposed technique with respect to direct electromagnetic optimization.     

Sequential tuning of microwave filters using adaptive models and parameter extraction

This paper describes a sequential procedure for computer-aided tuning and diagnosis of multiple-coupled resonator filters. The method is based on a sequential parameter estimation and a systematic tuning procedure and employs three different filter models. A detuned model represents the initial status of the filter after a well-defined detuning procedure. The target filter is described by an ideal model, whereas the actual state of the filter at each tuning step is represented by a coarse adaptive model. The goal of the procedure is the convergence of the coarse model to the ideal model and will be obtained by systematically centering resonant frequencies and coupling coefficients. Practical examples comprising low- and high-degree filters confirm the effectiveness of the proposed approach in both tuning and fault diagnosis.     

微波通信设备漏能的测试与分析

本文根据九个不同类型微波通信局(站)的微波设备在工作位对工作人员微波辐射量级的测试取得的大量数据,进行了分析处理,得出微波站工作位最大漏能为2.5μW/cm~2。文中还分析了其测试结果,找出了微波通信设备电磁波能量泄漏途径,提出了减少微波通信设备泄漏的防护措施及建议。     

Automatic construction of parts+geometry models for initializing groupwise registration

Groupwise nonrigid image registration is a powerful tool to automatically establish correspondences across sets of images. Such correspondences are widely used for constructing statistical models of shape and appearance. As existing techniques usually treat registration as an optimization problem, a good initialization is required. Although the standard initialization-affine transformation-generally works well, it is often inadequate when registering images of complex structures. In this paper we present a more sophisticated method that uses the sparse matches of a parts+geometry model as the initialization. We show that both the model and its matches can be automatically obtained, and that the matches are able to effectively initialize a groupwise nonrigid registration algorithm, leading to accurate dense correspondences. We also show that the dense mesh models constructed during the groupwise registration process can be used to accurately annotate new images. We demonstrate the efficacy of the approach on three datasets of increasing difficulty, and report on a detailed quantitative evaluation of its performance.