Automated microwave oven survey systems: evaluation criteria and procedures

Criteria and evaluation procedures have been established to assess the measurement accuracy of Automated Microwave Oven Leakage Survey Systems. These criteria and procedures are based upon analytical characterizations of the oven leakage fields, measurement data and statistical analysis and experience gained from evaluation of hand-held oven survey instruments. Results of our evaluation of a typical survey system are presented.     

The LPF with improved stopband response designed for wideband microwave detectors

To achieve an improved stopband response including expanded stopband width, increased rejection level, and a smooth S₁₁ phase response, a lowpass filter (LPF) is proposed based on the suspended microstrip line with naturally high characteristic impedance and the radial stub with intrinsic transmission zero. The usually unmentioned phase response, are critical to obtaining a wide and flat operating band for the microwave detector, since a smooth phase response exerts small load effects to the diode. As a demonstration, a detector employing the LPF is fabricated and measured. The measured results show that a wide operating band from 1.8 to 13.5 GHz with flat detection outputs of ripple less than 1 dB is obtained for the detector, which coincides with the smooth-phase range of the LPF.     

Feasibility of focused microwave array system for tumour irradiation

Radiofrequency hyperthermia has been used for treatment of cancer and relies on reduced blood flow through the tumour. Microwave-induced hyperthermia is proposed by means of an orthogonal-array system which produces a focal region for spatially selective internal heating within an attenuating medium.     

微波辐射电镜生物样品制备方法研究

本文报道一种快速微波辐射电镜样品制备方法──水浴法，以及这个方法在动植物样品超薄切片制备中的应用。实验结果表明，水浴法使得样品可以接受相对较长时间的微波辐射而不致造成任何损伤，浸泡液和样品的温度控制简单而且准确，样品处理的结果内外均匀一致，超微结构保存优秀，完全可与常规制样法和Ｌｏｇｉｎ法的结果相媲美，而且在某些方面水浴法要优于常规法和Ｌｏｇｉｎ法。     

Ferrite elements for hybrid microwave integrated systems

Complete realization of the potentialities of hybrid microwave integrated circuits will require both semiconductor and ferrite elements. This paper presents performance data for several microstrip ferrite devices that can play an important role in the exploitation of microwave integrated circuits. Data on both fixed-field and latched microstrip junction circulators are given including a fixed-field circulator with less than 0.4- dB loss and greater than 20-dB isolation over the 6.5- to 9.3-GHz band. The characteristics of microstrip meander-line phasers are discussed, and a simple, rugged technique for fabricating single-crystal YIG devices by embedding the YIG element in the substrate is presented.     

Numerical analysis of transitions for multilayer microwave circuits designed on the basis of electromagnetic crystals

Characteristics of transitions designed for connection of electromagnetic-bandgap (EBG) waveguides situated in different layers of a microwave electromagnetic crystal are analyzed. Two types of transitions (with slot and probe coupling) are considered. Two operating modes of the transition with slot coupling, the propagation mode and the cutoff mode, are studied. It is shown that wider operating band of the device is ensured in the cutoff mode. The possibility of transition from one layer to another with simultaneous power division into two channels is studied.     

微波介电加热合成半导体CuS纳米粒子

在2％的硬脂酸的丁醇溶液中,以硝酸铜和硫代乙酰胺为源村料,通过微波介电加热合成了CuS半导体纳米粒子,并用XRD、TEM进行了表征。     

Temperature dependence of composite microwave cavities

Composite microwave resonant cavities contain several regions of different dielectric materials. The variation of the resonant frequency with temperature is described in terms of a linear model. One part of the frequency variation is caused by the physical expansion of material parts, and the other by the change in the relative dielectric constant. The frequency sensitivity coefficients for both types of variation are obtained with the use of a computer code for numerical analysis of the electromagnetic field inside bodies of revolution     

Tuned optical receivers for microwave subcarrier multiplexedlightwave systems

An analysis of tuned optical-receiver noise performance for microwave subcarrier multiplexed lightwave systems is presented. The effect of correlation between the gate and the drain HEMT noise sources and the design of tuning networks to obtain partial noise cancellation were investigated. Anoptimization algorithm is used to determine the tuning elements values for minimizing noise of 16 dB for a 60-video-channel subcarrier multiplexing (SCM) system, and 12 dB for a 120-channel system, which allows a significant increase in passive optical network distribution capacity. Design results for tuned front-end receivers encompassing the effects of p-i-n, HEMT, and SCM band parameters are presented     

伴随您的一生：长期工作的超低功耗系统之设计

通过降低占空度及减小处理器．软件与模拟接口的功率需求，系统就可达到1μA量级的平均电流消耗。     

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.     

A fast-transient high-PSR output-capacitor-free low-dropout regulator for low-power embedded systems

A low-power fast-transient output-capacitor-free low-dropout regulator (LDO) with high power-supply rejection (PSR) is presented in this paper. The proposed LDO utilizes a non-symmetrical class-AB amplifier as the input stage to improve the transient performances. Meanwhile, PSR enhancement circuit, which only consumes 0.2-µA quiescent current at light load, is utilized to form a feedforward cancellation path for improving PSR over wide frequency range. The LDO has been designed and simulated in a mixed signal 0.13-µm CMOS process. From the post simulation results, the LDO is capable of delivering 100-mA output current at 0.2-V dropout voltage, with 3.8-µA quiescent current at light load. The undershoot, the overshoot and the 1 % settling time of the proposed LDO with load current switching from 50 µA to 100 mA in 300 ns are about 100 mV, 100 mV and 1 µs, respectively. With the help of proposed PSR enhancement technique, the LDO achieves a PSR of ?69 dB at 100 kHz frequency for a 100-mA load current.     

SEM observation of the insect prepared by microwave irradiation

The ptilinum of the fly and the compound eye are among the most fragile organs encountered during conventional procedures of morphological sample fixation. In order to identify a fixative suitable for preparing such samples for scanning electron microscopy, we examined various fixation conditions using microwave irradiation (MWI). The conditions examined were: (i) fixatives; (ii) temperature; (iii) concentration; (iv) duration; (v) dehydration; and (vi) substitution. The identified optimal conditions were 5% glutaraldehyde with MWI (350 W, 5 min). The MWI was continued until the maximal temperature of 75 degrees C was attained, followed by intermittent irradiation to maintain a temperature of 75 degrees C. After irradiation, the sample was left at room temperature for 24 h in the fixative and then dehydrated in increasing concentrations of ethanol. Each step in the ethanol series lasted for 24 h. The final absolute ethanol step included three solution changes, with each incubation lasting 1 h. A subsequent stepwise substitution of t-butyl alcohol for ethanol was conducted by reducing the ratio of 100% ethanol to t-butyl alcohol from 2:1 to 1:1 and then 1:2 (24 h each). The substitution was completed by three solution changes using 100% t-butyl alcohol, 30 min each. The best results were obtained by freeze-drying samples using t-butyl alcohol. The use of MWI improved fixative permeation, which occurred at a uniform rate throughout the sample. Comparison with temperature in a water bath at 75 degrees C indicated that the fixation effect of MWI was due to its heat generation in addition to some unknown mechanism.     

Temperature retrieval algorithm for brain temperature monitoringusing microwave brightness temperatures

A solution to the inverse problem of retrieving temperature from a set of microwave brightness temperatures together with a priori information regarding weighting functions and heat transfer within the infant head is introduced. The method offers the basis for non-invasive temperature monitoring appropriate for hypothermal neural rescue therapy     

Superconducting microwave filter systems for cellular telephone base stations

In the second decade following the discovery of high-temperature superconductivity (HTS), wireless communications has emerged as the earliest large commercial market. The enormous growth of the wireless industry coupled with its increasing technology demands has created a significant opportunity for HTS technology in wireless base stations. These systems combine high-performance HTS RF filters with cryocooled semiconductor preamplifiers to offer enhanced sensitivity to improve signal reception and exceptional selectivity to reject interfering signals. There are now thousands of installed HTS systems and the prospects are good for widespread future deployment. This paper discusses the underlying technologies that support HTS wireless applications, based upon the characteristic microwave properties of HTS thin films and substrates. HTS filter design technology has been under development for a decade and has gained a fair measure of maturity in terms of design tools, simulation techniques, and available topologies. The need for extremely narrow-band filters, highly selective filters, frequency-agile filters, and very compact filter designs has led to many technology advances. On the system level, comparable advances in cryocooler technology and cryopackaging have enabled the development of a broadly deployable technology. We discuss industry trends and the methodologies and results of simulations and real-world measurements of HTS filter systems.     

New type of dynamic frequency divider for microwave systems operation

A new type of dynamic frequency divider has been demonstrated successfully: a maximum dividing frequency of 8 GHz at room temperature was achieved. As a result of the new proposed design, a maximum toggle frequency of 30 GHz could be obtained after optimisation of various technological parameters. The design and the first experimental results are described and discussed.     

Experimental evaluation of microwave field-effect-transistor noisemodels

Extensive GaAs field-effect-transistor noise measurements are used to compare noise models with the aim of recommending the most useful one for monolithic-microwave integrated-circuit design. The evaluation is based on noise and S-parameter measurements of metal-semiconductor field-effect transistors and high electron-mobility transistors with different gatewidths in the frequency range of 0.05-26 GHz. The models under investigation differ in the number of independent coefficients necessary to calculate the four noise parameters of the device. The broad frequency range including radio-frequency frequencies down to 50 MHz requires two different noise measurement systems with special modifications for optimum performance. In conclusion, the two-parameter Pospieszalski model turns out to be the most suitable one     

Complementary-transistor wideband path for the compensation of analog ICs designed to operate under pulsed ionizing irradiation

For analog ICs exposed to pulsed ionizing radiation, a parallel wideband path is proposed as a means of compensation to reduce the recovery time, increase the bandwidth, and prevent parasitic oscillations and latchups.     

An evaluation of materials and processes for integrated microwave circuits

This paper presents an evaluation of materials and processes applicable to the fabrication of hybrid microstrip microwave circuits. Substrate materials evaluated included aluminas, beryllias, quartz, and glass of varying purities and surface finishes. Conductor materials evaluated included silver, copper, gold, and aluminum. Fabrication processes studied included vacuum deposition sputtering electroless and electroplating, thick-film screening and firing, and photoetching. Sapphire and high-purity alumina (99.5 percent pure or better) substrates were found superior as substrates for microstrip circuits. Conductor materials and processing methods found best were 1) vacuum deposited chromium-gold thin film which was gold electroplated and photoetched; 2) thick-film silver which was photoetched to delineate the microwave pattern.     

微波辐射的糖元PA-TCH-SP电镜特染

在显示糖元等多糖类物质 (碳水化合物 )的众多染色法中 ,PA- TCH- SP染色法是一种较理想的方法[1] ,其显示糖元颗粒清晰 ,尤其是染色背景较干净 ,非特异性沉淀少 ,但染色时间长 ( 1～3d) [2 ]。为缩短染色时间 ,作者探索用微波技术辅助染色 ,取得较好效果 ,并应用于寄生原虫、人睾丸支持细胞中的糖元显示[3,4 ] 。材料与方法标本包埋、切片 :鼠肝、阴道毛滴虫、人睾丸用戊二醛固定 ,不经锇酸固定或固定 5 min,常规电镜包埋 ;超薄切片 90 nm。染色试剂 :1 %过碘酸 ( PA) ,2 %硫卡巴肼 ( TCH) - 2 0 %醋酸 ( HAc) ,1 %蛋白银 ( SP)。微…