共查询到20条相似文献,搜索用时 15 毫秒
1.
J. S. Mandeep S. I. S. Hassan 《International Journal of Infrared and Millimeter Waves》2008,29(2):201-206
A propagation experiment has been carried out at Penang using the SUPERBIRD-C satellite beacon. Cloud occurrences were observed
during different months and it is seen that the low cloud occurrences over Penang is very significant from October to January.
The cloud attenuation results that are presented, which include the testing of models, have been obtained from the data gathered
over five years. The specific attenuation of radio wave due to clouds at various frequencies 12 GHz, 20 GHz, 75 GHz, 50 GHz
and 100 GHz has been estimated whereby the values varies from 0.14 dB/km at 12 GHz to 10.1 dB/km at 100 GHz. 相似文献
2.
Ming-Chieh Lin 《International Journal of Infrared and Millimeter Waves》2007,28(5):355-362
A multilayer waveguide window is demonstrated to exhibit wide bandwidth and high transmission for applications in high-frequency
microwave tubes. A transfer matrix approach is employed to discretize the dielectric function profile of the multilayer heterostructure
in a rectangular waveguide. The closed form has been obtained and the corresponding reflection and transmission characteristics
have been carried out. The analytical calculation is also compared with the result of numerical simulation via the finite-element
code HFSS. The exact calculation agrees with the numerical simulation very well. By comparison, the approach not only enhances
the accuracy and efficiency, but also gives a good criterion for the design. The results show that the bandwidth for a transmission
of 99%, i.e., S
11 below –20 dB, can be optimized to be about 8.75 GHz at a central frequency of 35 GHz or about 25%. A wide-bandwidth waveguide
window can be easily designed for Ka-band and W-band tubes, and even for higher frequency ones. 相似文献
3.
Rain Attenuation at Millimeter Wavelengths 总被引:2,自引:0,他引:2
A method of determining the rationality for raindrop size distribution is first presented. The relative volume occupied by raindrops is derived. The attenuation and cross-polar discrimination induced by rainfall at millimeter waves are investigated with the incoming expression and a brief analysis is presented. 相似文献
4.
Guofen Yu Karl H. Schoenbach Wenxiang Wang Shenggang Liu 《International Journal of Infrared and Millimeter Waves》2002,23(7):997-1006
An attempt to measure millimeter wave absorption spectra of E. coli was performed with a commonly used ratio method. The influences of water, which absorbs millimeter wave strongly, and the thickness of a sample holder were greatly reduced in our measurement compared with former reports. Some resonance-like absorption spectra were observed, but the resonance was found not from the absorption by E. coli after carefully examining the measurement. The reasons giving rise to the resonance-like artifacts were discussed. Proposals for making better use of the ratio method are given. 相似文献
5.
D. Maier N. Kämpfer J. de la Noë W. Amacher A. Barcia P. Baron B. Barry G. Beaudin J. Cernicharo B. Ellison J.-D. Gallego M. Gustafsson A. Karpov U. Klein K. Künzi J. Louhi J. Mallat D. Matheson J.-R. Pardo R. Peter A.V. Räisänen P. Ricaud R. Siddans C. Viguerie M. Wüthrich 《International Journal of Infrared and Millimeter Waves》2001,22(11):1555-1575
EMCOR is a heterodyne receiver for the frequency range of 201 to 210 GHz. It has been designed for ground-based measurements of various minor constituents of the stratosphere involved in ozone chemistry. Since the aim was the detection of faint spectral lines, a superconducting tunnel junction has been chosen as mixer element and special care has been taken in developing the calibration unit of the system. The front-end is completed by a quasi-optical system, a solid state local oscillator with electronic tuning and a HEMT pre-amplifier. In the back-end an acousto-optical spectrometer is employed to analyse the signal. A PC controls the whole system. The instrument has been installed at a high mountain site in the Swiss Alps. 相似文献
6.
T Utsunomiya M. Sekine 《International Journal of Infrared and Millimeter Waves》2005,26(11):1651-1660
We have conducted a millimeter wave propagation experiment at 103 GHz (2.9 mm) on a propagation path of 390 m. The results
were compared with the rain attenuation calculations from the Marshall-Palmer, Best, Joss-Thomas-Waldvogel and Weibull distributions
for raindrop-size. It has been shown that the Weibull distribution has a good agreement with the experiments. 相似文献
7.
Jiying Huang Shengli Lin Xuewen Ma 《International Journal of Infrared and Millimeter Waves》2000,21(10):1603-1606
While the millimeter radio wave propagates through rainfall, it will be attenuated heavily due to assimilation and scattering of rain. It is imperative to establish a simple and effective model to predict the rain-induced attenuation. In this paper, the rainfall is taken as a random system that can attenuate the radio wave. The transfer function matrix model is selected to be the random system model. Using experiment rain attenuation data at different rain rate, the correlation entropy and residue error of the system is obtained by system identification method. On the basis of correlation entropy and residue error, we can determine the order of the predication system. At last, the predication model that can forecast heavy rain attenuation by small rain attenuation is gotten by applying the least square method. The comparison shows that the discrepancy between the predication result of the obtained model and the experiment rain attenuation data is relatively minor. 相似文献
8.
In this paper, we introduce a new method, support vector regression (SVR) method, to model millimeter wave transitions. SVR
is based on the structural risk minimization (SRM) principle, which leads to good generalization ability for regression problem.
The SVR model can be electromagnetically developed with a set of training data and testing data which produced by the electromagnetic
simulation. Two Ka-band millimeter wave transitions, i.e., waveguide to microstrip transition and coaxial to waveguide adapter,
are used as examples to validate the method. Experimental results show that the developed SVR models have a good predictive
ability, and they are useful for interactive CAD of millimeter wave transitions. 相似文献
9.
在深入了解遮蔽物的特性对军事对抗、环境保护和森林防火等具有重大现实意义的基础上,针对目前室外测量遮蔽物激光透过率常用方法没有考虑激光脉冲发射能量起伏而导致测量精度低的问题,设计了一种新的试验方案和数据处理方法。新的试验设计考虑脉冲能量起伏,在早期设计方案的基础上增加了1个光分束器和1个激光接收机。这样设计的目的是为了得到遮蔽物释放后无法获得没有遮蔽物时测量处接收机所接收的每个激光脉冲的能量,从而消除脉冲能量起伏对测量精度的影响。提出监测激光脉冲发射能量并用其对远场接收处能量进行反演的数据处理方法,从而明显改善了透过率测量的精度,增强了决策的科学性和可靠性。 相似文献
10.
11.
推导出了基于高斯分布的毫米波的功率分布函数,并分别根据传统的pennes方程和新提出的HBHE方程以及毫米波在动物皮肤内的传播特性,建立了33.5 GHz毫米波不同辐照强度下的大鼠皮肤的非稳态多层传热模型,在二维柱坐标下进行离散计算,得到了长时间辐照条件的温度变化规律,并将理论结果与实验数据进行了比较,发现HBHE的结果与实测结果更为吻合,特别是在高功率条件辐照下,与实测结果基本一致,验证该理论模型的优越性。 相似文献
12.
A. O. Salman D. Dibekci S. Gavrilov A. Alexei Vertiy 《International Journal of Infrared and Millimeter Waves》2008,29(5):465-485
In this paper, investigation of radiation properties of the traveling-wave sinusoidal wire antennas is extended to the millimeter-wave
frequencies (Ka-band) for the antennas whose geometrical dimensions vary in a wide range. Far-field patterns and S-parameters
of composed three antenna sets were measured. A mathematical model was constructed for the structure and a MATLAB code based
on this theoretical approach was written to calculate patterns, phase and attenuation constants of all investigated antennas.
Frequency characteristics and the relation of antenna dimensions with wave parameters were investigated. Measured and calculated
patterns were also compared with the constructed far-field patterns obtained by MoM (method of moments) and the MoM current
distributions were used to explain the loss mechanisms of antennas. A directive, undistorted and smooth radiation can be achieved
only choosing small undulated antennas whose peak-to-peak amplitude to period ratio κ is smaller than 0.4 (κ < 0.4). It is
shown that wavelength of broadside radiation is not equal to antenna period for all antennas, except for very small undulated
antennas (κ < 0.2). This antenna type can be used as a frequency-scan antenna for millimeter wave radars.
相似文献
A. O. SalmanEmail: |
13.
P. Mali S. K. Sarkar A. B. Bhattacharya 《International Journal of Infrared and Millimeter Waves》2001,22(1):153-171
Radio wave operating in millimetrewave and microwave frequency bands are adversely affected due to rain. Particularly the attenuation is of immense significance for sensitive remote measurements by satellites using frequencies greater than 10 GHz. Maintenance of an uninterrupted communication link requires a precise knowledge of the attenuation effect due to rain for commissioning right kind of transmitting sources for various purposes required in present day situation. Precise measurement of attenuation at various frequencies will enable us to choose the right frequency, polarization, incident angle and power of the source for different purposes. In this paper we have compared the results of earlier works using aRb Olsen et al, (1) and the formulation by Moupfouma, (2) on the basis of theoretical analysis for explaining the observed results. Effect of temperature, considered in detail in this communication, has contributed the necessary correction factor of the rain attenuation for explaining the observed results. Theoretical analyses to measure the attenuation of the propagating wave due to temperature variation in the rain path have been presented. Correction factor due to temperature profile (temperature from the ground to the rain height within which the radio wave traces its path) has been incorporated in two models by using the concept of dipole energy changes. The effect of this temperature is noted to be quite significant and incorporates an error to the extent of 7–8%. 相似文献
14.
J. S. Mandeep S. I. S. Hassan 《International Journal of Infrared and Millimeter Waves》2008,29(3):225-231
Based on radar range height indicator (RHI) measurements, cloud characteristics in relation to radiowave propagation over
three locations in different geographical region in western Malaysia have been presented. It is seen that low cloud occurrence
over these locations are quite significant. Cloud attenuation and noise temperature can result in serious degradation of telecommunication
link performances. This paper presents cloud coverage in different months, 0°C isotherm height and cloud attenuation results
at 12 GHz, 20 GHz, 36 GHz, 50 GHz, 70 GHz and 100 GHz over measurement site. The low level cloud over the measurement sites
has been found to occur for many days and nights and particularly in the months of April to May and October to December. Such
results are useful for satellite communication and remote sensing application in Malaysia. 相似文献
15.
Huilai Liu Bing-Zhong Wang Wei Shao 《International Journal of Infrared and Millimeter Waves》2007,28(1):25-31
A novel dual-band bi-directional reconfigurable antenna based on Koch patch is presented in this paper. By controlling the
switches in the slots etched on the Koch patch, different far field bi-directional patterns at the dual-band around 60 GHz/80 GHz
could be achieved. And full azimuthal coverage at this dual-band is possible by electronically controlling the switches in
the slots of the patch.
This work was supported by the National Natural Science Foundation of China (No. 60371008, No. 90505001) and the CRT Program
of UESTC. 相似文献
16.
Pinpin Yan Wei Hong Jixin Chen 《International Journal of Infrared and Millimeter Waves》2008,29(3):282-290
A millimeter wave phase locked and frequency multiplying source is proposed in this paper. The design includes an X-band phase
locked loop (PLL) frequency synthesizer as the base frequency source, and a monolithic millimeter wave frequency tripler,
which is developed by using OMMIC 0.18μm pHEMT process. The PLL and the tripler are integrated in a single circuit board to
make a low-cost and compact frequency source with the size of 6cm × 5cm. Measurement shows an output power of more than 4.8dBm
at the frequency range from 35 to 36.7GHz. A phase noise of about -92dBc/Hz at 100kHz offset is achieved. 相似文献
17.
Yang Ju Yo Hirosawa Masumi Saka Hiroyuki Abé 《International Journal of Infrared and Millimeter Waves》2003,24(3):391-397
We developed a compact equipment working at 94 GHz to replace the commonly used network analyzer for nondestructive testing of materials. The compact equipment was designed to measure the variations in the amplitude and phase of the reflected signal from the material relative to a reference signal. A good accuracy of the amplitude and phase measurement of the equipment was obtained in the confirmative experiments. The distribution of a drop of water in a wood plate is clearly visible in the millimeter wave images obtained by the amplitude and phase measurement. 相似文献
18.
S. I. Hwang S. Ishii S. Sayama M. Sekine 《International Journal of Infrared and Millimeter Waves》2007,28(1):79-86
Sea-ice clutter was measured using a millimeter wave radar (MWR) with a frequency of 34.86 GHz, the beamwidth of 0.25° and
pulsewidth of 30 ns which is located at Mombetsu in Hokkaido, Japan. In this paper, targets are an iron tower and a breakwater
which are embedded in sea-ice clutter. We have found that the sea-ice clutter amplitude obeys the Weibull distribution. As
a result of this, we obtained target to clutter ratio improvement of 22.6, 17.2 dB for an iron tower and a breakwater, respectively,
by considering the modified LOG/CFAR system which is the transformation from Weibull to Rayleigh distribution. 相似文献
19.
Yonghong Zhang Yong Fan Zhengde Wu 《International Journal of Infrared and Millimeter Waves》2007,28(4):299-304
In order to estimate the phase noise of millimetre wave (MMW) phase-locked oscillator (PLO), the phase noise relation of signals
in MMW phase-locked loop (PLL) with frequency conversion is analyzed. The signals include output of MMW PLO, intermediate
frequency (IF) output of harmonic mixer and output of microwave oscillator serving as local oscillator (LO). A method to estimate
the phase noise of MMW PLO is presented, which is based on the phase noise of LO and IF. At the same time, a W-band PLO is
achieved, and the phase noise values of the three signals are measured. It is shown that the experimental result is well coincident
with the analysis of phase noise relation. 相似文献
20.
Yang Ruike Wu Zhensen Yang Zhiyong Guo Lixin 《International Journal of Infrared and Millimeter Waves》2004,25(3):503-512
In this paper, the general formulations of two-frequency mutual coherence function, , for a pulse wave propagating in random discrete media are summarized. The relations of the amplitudes and phases of the to d are given by Ishimaru et al, based on average particle in cloud and rain. In practice, since the particles sizes in random discrete media are in a size distribution spectrum, the ought to be derived from a particles size distribution. Based on an approximately solution, we describe these examples of millimeter waves (94, 220GHz) pulse propagating in rain and show that the 's amplitudes and phases obvious varies as rainfall and frequency. For a kind of rain, considering raindrops size distribution and average raindrop size, respectively, the 's amplitudes and phases are calculated. The numerical results show that the differences between the results calculated by raindrops size spectrum and by average size are remarkable, especially for heavy rainfall. Therefore, It is shown that the calculated by a particles size distribution is more reasonable than by average size. For the numerical analyses, particles size distribution ought to be adopted. This study is important for us to provide adequate bandwidths to achieve high-rate pulse communications and improve MMW radar system performances and atmospheric remote-sensing techniques. 相似文献