Bidirectional reflectance one-dimensional rough distribution function modeling of surface in the microwave band

In this study, the bidirectional reflectance distribution function （BRDF） of a one-dimensional conducting rough surface and a dielectric rough surface are calculated with different frequencies and roughness values in the microwave band by using the method of moments, and the relationship between the bistatic scattering coefficient and the BRDF of a rough surface is expressed. From the theory of the parameters of the rough surface BRDF, the parameters of the BRDF are obtained using a genetic algorithm. The BRDF of a rough surface is calculated using the obtained parameter values. Further, the fitting values and theoretical calculations of the BRDF are compared, and the optimization results are in agreement with the theoretical calculation results. Finally, a reference for BRDF modeling of a Gaussian rough surface in the microwave band is provided by the proposed method.

SIMPLIFICATION OF THE OXYGEN-ABSORPTION COEFFICIENT FORMULA IN MICROWAVE BAND

Study of the oxygen-absorption coefficient in 5mm wave band is important for remote sensing of the atmospheric temperature profile from satellites or ground.In order to obtain the atmospheric temperature profile rapidly and accurately,it is necessary to have a simple,but accurate formula of the oxygen-absorp- tion coefficient.In this paper,formulae of the oxygen-absorption coefficient in a certain range of tempera- ture-pressure and at a standard isobaric surface have been derived.These formulae may substitute for Meeks- Lilley formula in remote sensing of the atmosphere.

Radiation Losses in the Microwave X Band in Al-Cr Substituted Y-Type Hexaferrites

We present a study on radiation losses in the microwave X band in Al-Cr substituted Y-type hexaferrites, namely Ba2Mg2Alx/2Crx/2Fe12-xO22 （x = 0, 0.5 and 1.0）. The study is performed by means of a vector network analyzer, Fourier transform infrared spectroscopy, a vibrating sample magnetometer and x-ray powder diffraction. Ba2Mg2Fe12O22 hexaferrite shows radiation loss of -37.25dB （99.999% loss） at frequency 9.81 GHz, which can be attributed to its high value of saturation magnetization, i.e., 22.08emu/g. Moreover, we obtain that magnetic properties have strong influence on the radiation losses.

Triple-Band L-Shaped Monopole Antenna with Defected Ground Plane for WLAN and WiMAX Application

This paper presents the simulation and measured results of a triple-band L-shaped monopole antenna with defected ground plane for applications in wireless local area networks（WLANs） and worldwide interoperability for microwave access（WiMAX） bands.The triple-band L-shaped monopole antenna with defected ground plane was fabricated on a FR4 substrate. The lower band is associated with the shorted parasitic strip in the protruding stub of the ground plane; the middle band is expected to be controlled by the longer strip of L-shaped monopole in the front side,while the higher band is associated with the short strip of L-shaped monopole in the front side. The proposed antenna has a good agreement between the measured and the simulation results. It has a 10 d B return loss with the bandwidth of 250 MHz（2270 MHz to 2520MHz） in the lower band, 600 MHz（3320 MHz to 3,920MHz） in the middle band, and 1110 MHz（5030 MHz to6140 MHz） in the higher band. The proposed antenna covers the ISM（industrial, scientific and medical）,HIPERLAN（high performance radio local area network）, UNII（unlicensed national information infrastructure）, and WiM AX bands.

Mechanism analysis of radiation generated by the beam-plasma interaction in a vacuum diode

When we were studying the vacuum switch,we found that the vacuum diode can radiate a broadband microwave.The vacuum diode is comprised of a cathode with a trigger device and planar anode,there is not a metallic bellows waveguide structure in this device,so the radiation mechanism of the vacuum diode is different from the plasma filled microwave device.It is hard to completely imitate the theory of the plasma filled microwave device.This paper analyzes the breakdown process of the vacuum diode,establishes the mathematical model of the radiating microwave from the vacuum diode.Based on the analysis of the dispersion relation in the form of a refractive index,the electromagnetic waves generated in the vacuum diode will resonate.The included angle between the direction of the electromagnetic radiation and the initial motion direction of electron beam is 45 degrees.The paper isolates the electrostatic effect from the beam-plasma interaction when the electromagnetic radiation occurs.According to above analyses,the dispersion relations of radiation are obtained by solving the wave equation.The dispersion curves are also obtained based on the theoretical dispersion relations.The theoretical dispersion curves are consistent with the actual measurement time-frequency maps of the radiation.Theoretical deduction and experiments indicate that the reason for microwave radiating from the vacuum diode can be well explained by the interaction of the electron beam and magnetized plasma.