Microwave Propagation in Saline Dust Storms

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  • International Journal of Infrared and Millimeter Waves, Vol. 25, No. 8, August 2004 ( 2004)

    MICROWAVE PROPAGATION IN SALINE DUST STORMS

    Y. Yan

    Department of PhysicsYantai University

    Yantai, Shandong, 264005, People's Republic of ChinaE-mail: yanyi@ytu.edu.cn

    Received April 16, 2004

    Abstract: Dielectric constant of sand-powder sampled from saline dustarea have been measured at W band by means of wave-guide method.Based on the analysis of the characteristics of saline dust storms, themicrowave and millimeter wave attenuation and phase shift in saline duststorms are investigated.

    Keywords: Microwave, millimeter waves, saline dust storms, attenuation

    1. Introduction

    The spread of the deserts affects most countries. Over vast areas of everycontinent, the rainfall and vegetation necessary for life are disappearing.Already more than 40 percent of the earth's land is desert or desert-like.

    Today's problems are caused in great part by distinctly modem factors.People benefited from improvements in public health and modemfarming methods. The population grew. Farmers planted more crops andenlarged their herds of cattle, sheep, and goats. When the drought came,

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    0195 9271/04/0800 1237/0 0 2004 Plenum Publishing Corportion

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    the crops failed and the cattle ate all the grass. The fragile land quicklylost its top soil and become nothing but sand and dust.

    In the north of China, some marsh swamps have become salt marshes,some lakes have already become salinized soil, and some areas are reallydeserts. Saline dust storms will be a new form of sand and dust storms.

    Absorption and scattering from dust particles is one of the possiblecauses of co-polarization attenuation between communication systemslocated in sandstorm operating in the microwave and millimeterwavelength band. Low rainfall volume suggests the promise of terrestriallink using higher millimeter wave frequencies for radio communicationin desert areas [1,2]. A distinction should be made between large sandgrains and fine sand dust. Sand grains of greater than about 0.2mmdiameter are driven as a low flying cloud, with a high of less than aboutseveral meters above the ground. On the other hand, dust like sandparticles can rise in dense clouds to a high of one kilometer or more. Thisletter type of sandstorm, which is essentially a misnomer for dust storm,may lie in the terrestrial and earth-space paths of millimeter wave, hence,path attenuation data are required [3,4].

    In order to study the effects of sand and dust storms on millimeter wavecommunication, radar, and radio wave propagation, it is necessary tomeasure the dielectric characteristics of sand and dust storms [5,6]. Inthis paper, we are concerned with the microwave and millimeter waveattenuation and phase shift in saline dust storms. We use the wave-guidemethod to study the measurement of the dielectric characteristics ofsaline dust storms at W band. It has practicality on researching the effectof saline dust storms on radio wave propagation at W band. Then, themillimeter wave attenuation and phase shift in saline dust storms areinvestigated. This is the first work of studying on millimeter wavepropagation in saline dust storms.

    Yan

  • Propagation in Dust

    2. Measurement method

    The dielectric constant of saline dust storms was measured by means ofwave-guide method. The sample of dust particles was filled in samplewave-guide, decreasing the space of dust particles as small as possible.The sample wave-guide was measured vertically to protect dust levelagainst loose and oblique, the measurement was made with 94GHzslotted line. The results of measurement were shown as Table 1.

    Table 1. Dielectric constant measured from saline dust stormsNo. E' E,

    1 2.204 0.0462 2.317 0.0663 2.235 0.0874 2.244 0.0755 2.132 0.0586 2.246 0.064

    Mean 2.229 0.066Frequency: 94GHzWave-guide transverse section: 2.54 x 1.27 mm2

    Temperature: 20 C

    The dielectric constant with infinite long sample can be given by [7]

    1 1 - j tan(fD)Er- + 2 - ( '

    A+( ,+ , I,-1jptan(f6D) '), l+(

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    (1)

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    in which, A is the cutoff wavelength, Ag is the length of wave-guide,p is the standing wave ratio, /1 is the composite SWR, andD = D, - D,., Dm is the position of smallest point, D,, is the positionof reference point in slotted line.and

    E,12 =Ca+[bp(l +C2 )2 + (p 2 -) 2 2 (2)1+p2C2 ( p2 C2)2

    cb(p2 - 1)(cI = arctan[ cbp2 1)(3)a(l + p2C2)+bp(1 +c 2)

    in which1 1

    a- ) b A c=tan(/D).

    The effective dielectric constant of simulative saline dust storms canbe calculated with the mathematical model given by Hallikainet [81. Thedielectric constant of media can be given by

    Ce =E e'+JE , (4)in which

    1 + 3V(e'-1)('+2) + e"(+2)2 + E29Ve'

    (E"+2)2 + 'and, V is the volume ratio occupied by dust particles.

    3. Millimeter wave attenuation and phase shift

    Based on the theory of equivalent media propagation, the saline duststorms can be seen an even media, in which all particles has same radius.The propagation constant of saline dust storms is given by

    Yan

  • Propagation in Dust

    a = a + j, (5)in which,

    a= 3.431xl6 f Nr3 22(1,+2)2 + ,2'

    = 7.545 x 106 f N r3 (E'-1)(e'+2) + 2(69+2)2 + Er2

    In which , f is the frequency of millimeter system, N is the number ofdust particles in unit volume, and r is the radius of dust particle.

    If the density of dust particles is 30 g / m3 , the attenuation coefficient

    El l

    c - 1.89 x 106 f W 2 ,2 dB / km , (6)

    and, the phase shift coefficient

    p = 4.15xl0 6 fW ('-)('+2)+ deg/km. (7)('+2)2 + 2

    in which, W is the content of dust particles per unit volume.Figure 1 shows the calculation result of the attenuation coefficient at

    different content of dust particles. Figure 2 shows the calculation resultof the phase shift coefficient at different content of dust particles.

    10 - -- -

    0.1 1 10 100

    W/ g.m3

    Fig. 1 The relation between the attenuation coefficientand the content of dust particles(f=94GHz).

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    100

    o . ..

    10 _

    1 10 100

    w/ g.i

    Fig. 2 The relation between phase shift coefficientand the content of dust particles(f=94GHz).

    4. Conclusion

    Some of the properties of saline dust storms were reviewed. Thedielectric constant of saline dust storms was measured by means ofwave-guide method. The dielectric characteristics of saline dust stormswas used to calculation the attenuation coefficient and phase shiftcoefficient of saline dust storms.

    Then, the millimeter wave attenuation and phase shift in saline duststorms were investigated. This is the first work of our studying onmillimeter wave propagation in saline dust storms.

    REFERENCES

    [1] Chu T. S., Effect of sand storms on microwave propagation, Bell Syst.Tech. 1979, 58, pp.549-555

    [2] Bashir S. O., and Mcewan N. J., Microwave propagation in duststorms: a review, IEE Proc., 1986, 3, pp.2 41-24 7

    [3] Ahmed A. S., Role of perticle-size distribution on millimeter wave

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    propagation in sand/dust storms, IEE Proc. 1987, 134, Pt. H. pp.55-59[4] Ghobrial S. I., and Sharief S. M., Microwave attenuation and cross

    polarization in dust storms, IEEE Trans. 1987, AP-35, pp.4 1 8-425[5] Shuyi dong, et al, Measurement of sand-powders and analogical

    analysis on sandstorm at W band, Proceedings of the InternationalConference on Millimeter and Submillimeter Waves and Applications,SPIE 1994, Vol. 2211, pp. 8 3 -8 6

    [6] Dong Q. S., MM wave propagation experiments in sand dust stormand smoke, ICMWFIT'92, 1992, pp. 78 - 81

    [7] Shuyi dong, Technology of Microwave Measurement, Beijing Scienceand Engineering University Publishing House, Beijing, 1990

    [8] Hallikainet M. T. et al, Microwave dielectric behavior of wet soil,IEEE 1985, Trans. On GE-23