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 China
E-mail: [email protected]
Received April 16, 2004
Abstract: Dielectric constant of sand-powder sampled from saline dust
area have been measured at W band by means of wave-guide method.
Based on the analysis of the characteristics of saline dust storms, the
microwave and millimeter wave attenuation and phase shift in saline dust
storms are investigated.
Keywords: Microwave, millimeter waves, saline dust storms, attenuation
1. Introduction
The spread of the deserts affects most countries. Over vast areas of every
continent, 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 modem
farming methods. The population grew. Farmers planted more crops and
enlarged their herds of cattle, sheep, and goats. When the drought came,
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the crops failed and the cattle ate all the grass. The fragile land quickly
lost 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 really
deserts. Saline dust storms will be a new form of sand and dust storms.
Absorption and scattering from dust particles is one of the possible
causes of co-polarization attenuation between communication systems
located in sandstorm operating in the microwave and millimeter
wavelength band. Low rainfall volume suggests the promise of terrestrial
link using higher millimeter wave frequencies for radio communication
in desert areas [1,2]. A distinction should be made between large sand
grains and fine sand dust. Sand grains of greater than about 0.2mm
diameter are driven as a low flying cloud, with a high of less than about
several meters above the ground. On the other hand, dust like sand
particles can rise in dense clouds to a high of one kilometer or more. This
letter 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 wave
communication, radar, and radio wave propagation, it is necessary to
measure the dielectric characteristics of sand and dust storms [5,6]. In
this paper, we are concerned with the microwave and millimeter wave
attenuation and phase shift in saline dust storms. We use the wave-guide
method to study the measurement of the dielectric characteristics of
saline dust storms at W band. It has practicality on researching the effect
of saline dust storms on radio wave propagation at W band. Then, the
millimeter wave attenuation and phase shift in saline dust storms are
investigated. This is the first work of studying on millimeter wave
propagation in saline dust storms.
Yan
Propagation in Dust
2. Measurement method
The dielectric constant of saline dust storms was measured by means of
wave-guide method. The sample of dust particles was filled in sample
wave-guide, decreasing the space of dust particles as small as possible.
The sample wave-guide was measured vertically to protect dust level
against loose and oblique, the measurement was made with 94GHz
slotted line. The results of measurement were shown as Table 1.
Table 1. Dielectric constant measured from saline dust storms
No. E' E,
1 2.204 0.046
2 2.317 0.066
3 2.235 0.087
4 2.244 0.075
5 2.132 0.058
6 2.246 0.064
Mean 2.229 0.066
Frequency: 94GHz
Wave-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+(
1239
(1)
1240
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 position
of 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 can
be calculated with the mathematical model given by Hallikainet [81. The
dielectric constant of media can be given by
Ce =E e'+J£E , (4)
in which1 + 3V(e'-1)('+2) + e"
(£+2)2 + E2
9Ve'
(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 dust
storms 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 of
dust 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 result
of 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 coefficient
and the content of dust particles(f=94GHz).
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1242
100
o . ..
10 _
1 10 100
w/ g.i
Fig. 2 The relation between phase shift coefficient
and the content of dust particles(f=94GHz).
4. Conclusion
Some of the properties of saline dust storms were reviewed. The
dielectric constant of saline dust storms was measured by means of
wave-guide method. The dielectric characteristics of saline dust storms
was used to calculation the attenuation coefficient and phase shift
coefficient of saline dust storms.
Then, the millimeter wave attenuation and phase shift in saline dust
storms were investigated. This is the first work of our studying on
millimeter 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 dust
storms: 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 Dust 1243
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 International
Conference 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 storm
and smoke, ICMWFIT'92, 1992, pp. 78 - 81
[7] Shuyi dong, Technology of Microwave Measurement, Beijing Science
and Engineering University Publishing House, Beijing, 1990
[8] Hallikainet M. T. et al, Microwave dielectric behavior of wet soil,
IEEE 1985, Trans. On GE-23
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