Effects of Hydrated Water Content on Rectangular and Spherical Shape Sand/Dust Particle at Micro-Wave Signal Attenuation

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1 Effects of Hydrated Water Content on Rectangular and Spherical Shape Sand/Dust Particle at Micro-Wave Signal Attenuation ABSTRACT Sandeep Kumar M.Tech Student-ECE Jasvinder Kaur A.P.-ECE The single attenuation properties (Q.ext and Q.sca) of sand/dust particles assumed to be in Rectangular and Spherical shape with hydrated water content are computed from the discrete dipole approximation (DDA) method at microwave frequencies 14,24 and 37 GHz. The different atmospheric particle shape has different signal attenuation due to the dust particle. When increasing the shape complexity of the particle the attenuation of microwave signal is serially affected at higher frequencies and larger particle sizes. The frequency ranges (14-37) are most commonly used in the communication. The single attenuation properties of sand/dust particles are strongly sensitive to the particle shape and hydrated water content present in the particle. The used particle size is um and hydrated water content is up to 30% for 14 GHz and 24 GHz, 20% for 37 GHz. The signal attenuation is depends on the particle Spectral variation, particle morphology (shape and size) and hydrated water content present in dust/sand particle in the Earth atmosphere. Keywords DDA,, Spherical Shape, Dust Particle, Hydrated Water, Signal Communication. 1. INTRODUCTION In communication radio link the microwave signal is attenuated due to Rain, Ice and Dust. Sand and dust storms play an important role in the Earth atmosphere and communication link performance. In this paper work we focus on Effects of Hydrated Water Content on Rectangular and Spherical Shape Sand/Dust Particle at Micro-Wave Signal Attenuation. Due to sand and dust storms the Earth s radiation balance, rain fall distribution and cloud properties can be changed. To measure the effect of the particle nonsphericity and hydrated water on micro-wave signal attenuation, first the various shapes and sizes of highly nonspherical Sand/Dust particle are taken. The used frequencies are 14, 24 and 37 GHz.The various particle shapes are Spherical and Rectangular. The Rectangular shape attenuates the signal more than the spherical shape. But the Spherical shape has less effect than the other shape of Sand/Dust particle on the microwave signal. Signal attenuation of the microwave signal increases with increase in communication frequency. The attenuation of the microwave signal also depends upon the value of hydrated water content present in the Sand/dust particle. So, 30 samples of the particles have Pardeep Kumar M.Tech Student-ECE Kuldeep Vats M.Tech Student-CSE been collected from the atmosphere. Information in relation to the particle shape has been gathered with the help of Morphology Process. The values of single attenuation properties (Q.ext and Q.sca) for both shapes of sand/dust particles at various values of hydrated water content in particles have been calculated. 2. METHODOLOGY The Discrete Dipole Approximation (DDA) method is used to measure the refractive index for both real and imaginary values at various wavelengths and also various amounts of moisture constant of water for different shapes and size of the Sand/Dust particle. For DDA input we use the particle size (5-100 um), various shapes (Spherical and Rectangle) and different wavelengths (um). The output of the code is extinction and scattering cross-sections (Q.ext and Q.sca). Using DDA, the optical properties have been computed for a given size, wavelength and refractive index. Optical properties such as extinction, absorption and scattering efficiencies of the spherical particle for a given size parameter and index of Refraction is computed using the DDA. We are using the 900 different computational programs in DDA system. More than 100 hundred samples of particle shapes have been taken from Delhi (India) area with the help of Morphology process. The samples have been taken at regular intervals of 4, 8 and 16 hours. With the help of the equations (1and 2) the real and imaginary value (n & k) of Refractive index can be measured by using the real & imaginary constant (E1 & E2) of Dielectric constant (E). The Used equations are,... (1) (2) The various wavelengths (λ) are used to measure the effect of the shape and size of Sand/Dust particle on the microwave signal. And the equation (3) is used to measure the different wavelength. F Frequency C Velocity of Light = (3*10 8 ) meter/second. λ -. (3) 27

2 Q.ext at 14 MHz with various values of hydrated water content Q.ext at 14 MHz with various values of hydrated water content For the input in the Discrete Dipole Approximation (DDA) the following table has been used. (See Ansari et al. [4]) Table 1. Summary of published dielectric constant for sand and other soil types in the microwave range. Frequency Soil type Moisture Content Dielectric Constant (E) Refractive Index Wavelength (GHz) %(gh2o/g Soil) Real (E1) Imaginary(E2) Real (n) Imaginary (k) λ(mm) 14 Sand Sand Loamy fine Sand RESULT ANALYSIS The 900 different computational programs results in DDA system have been used. The result output in form of extinction and scattering cross-sections (Q.ext and Q.sca) have been derived. The values of the Q.ext and Q.sca for all the shapes and sizes of the highly non-spherical particles with various values of hydrated water content have been measured. Different tables and graphs for both Q.ext and Q.sca for different shapes on different Spectral variation have been prepared. The graph has been plotted between the particle size and Q.ext/ Q.sca value on different Frequencies for various shapes. The OriginPro.8 software has been used to plot the graph. 3.1 Variation of Q.ext at 14 GHz for spherical and rectangle shapes relative to variation of Particle Morphology (size) and Hydrated Water content in Sand Particle: - Njoku [14] shows that the variation of complex dielectric constant with frequency and moisture content for sandy soil. The dry-sand has less signal attenuation than the water present in the sand particle. Ghobrial [17] shows that, at 9.4 GHz for water content as low as 4%, the real part of the dielectric constant was increased by 25% and the imaginary by 100%.So, when we increase the value of hydrated water content into the sand /dust the signal attenuation is much higher than dry sand. Fig.1 (a & b) shows that the Q.ext value for the spherical and rectangle shapes at 14 MHz. With change in the value of hydrated water content (0.3, 5, 10, 20 and 30) % and the size also varies. Here the signal attenuation (Q.ext) on 30 % hydrated water for rectangle shape is approximately1.63 times higher than the Signal attenuation (Q.ext) on 30 % hydrated water content for spherical shape of 100 um particle size. Fig.1 (a & b) shows the following results. 1. Signal attenuation is highly dependent of particles shape and value of hydrated water content present in the sand/dust particle. Fig.1(a) Fig.1 (b) Figure 1:- Variation of (a) Q.ext for spherical and (b) Q.ext for rectangular shape with varying particle morphology(shape and size) and hydrated water content in sand particle at 14 GHz 28

3 Q.ext at 24 MHz with various values of hydrated water content Q.ext at 24 MHz with various values of hydrated water content 2. Rectangular particles which are sharp edged show attenuation efficiency more than spherical shapes considered in the study with increase in amount of water. 3. And spherical particles being smooth particles show less attenuation in signal with increase in amount of water. 4. In spherical shape, the signal attenuation (Q.ext) content in particle is approximately times higher than the signal attenuation (Q.ext) content in the particle. 5. In rectangular shape, the signal attenuation (Q.ext) with 30 % water content in particle is approximately times higher than the signal attenuation (Q.ext) with 0.3 % water content in particle. 6. Here the signal attenuation increases with the increasing value of hydrated water in the particle. 3.2 Variation of Q.ext at 24 GHz for spherical and rectangle shape with varying of Particle Morphology (size) and Hydrated Water content in Sand Fig.2(a & b) show that the Q.ext value for the spherical and rectangle shapes at 24 MHz with change the value of hydrated water(0.3,5,10,20 and 30) % and the size is also vary. We see that the signal attenuation (Q.ext) on 30 % hydrated water for rectangle shape is approximately 1.64 times higher than the signal attenuation (Q.ext) on 30 % hydrated water content for spherical shape for 100 um particle size. Fig.2 (a & b) Shows the following results. 1. Signal attenuation is highly dependent of particles shape and value of hydrated water content present in sand/dust particle. Fig.2 (a) Fig.2 (b) Figure 2:- Variation of (a) Q.ext for spherical and (b) Q.ext and hydrated water content in sand particle at 24 GHz 2. Rectangular particle being sharp edged particles show less attenuation efficiency after 20% hydrated water content in sand/dust particle. 3. And spherical particles being smooth particles show decreasing attenuation efficiency after 20% hydrated water content in sand/dust particle. 4. In spherical shape signal attenuation (Q.ext) with approximately times higher than the signal attenuation (Q.ext) with 0.3% hydrated water 5. In rectangular shape, the signal attenuation (Q.ext) with 30 % water content in particle is approximately times higher than the signal attenuation (Q.ext) with 0.3 % water content in particle. 6. The signal attenuation starts to decrease after a particular value of hydrated water content in spherical shape particle as seen. 3.3 Variation of Q.sca at 14 GHz with Fig.3(a & b) show that the Q.sca value for the spherical and rectangle shapes at 14 MHz with change the value of hydrated water(0.3,5,10,20 and 30) % and the size is also vary. We see that the signal attenuation Q.sca values on 30 % hydrated water for rectangle shape is approximately 1.53 times higher than the signal attenuation (Q.ext) on 30 % hydrated water content for spherical shape of 100 um particle size. 29

4 Q.sca at 24 MHz with various values of hydrated water content Q.sca at 14 MHz with various values of hydrated water content Q.sca at 24 MHz with various values of hydrated water content Q.sca at 14 MHz with various values of hydrated water content 3.4 Variation of Q.sca at 14 GHz with Fig.4(a & b) show that the Q.ext value for the spherical and rectangle shapes at 24 MHz with change the value of hydrated water(0.3,5,10,20 and 30) % and the particle size is also vary. Here the signal attenuation (Q.ext) values on 30 % hydrated water for rectangle shape approximately 1.54 times higher than the signal attenuation (Q.ext) value on 30 % hydrated water content for spherical shape of 100 um particle size. Fig.3 (a) Fig.4 (a) Fig.3 (b) Figure 3:- Variation of Q.sca for rectangular shape with varying particle morphology (size) and hydrated water content in sand particle at 14 GHz Fig.3 (a & b) Shows the following results. 1. Scattering efficiency is independent of particles shape till size less than 60 um. 2. Rectangular shaped particles size after 60um, show more scattering efficiency than other shapes of particle considered in the study. 3. In spherical shape, signal scattering (Q.sca) with approximately 5-6 times higher than the signal scattering (Q.sca) 4. In rectangular shape, signal scattering (Q.sca) with approximately 7 times higher than the signal attenuation (Q.sca) 5. All time signals scattering efficiency (Q.sca) increases with the increasing value of hydrated water for all shapes present in the Sand/dust particle at 14 GHz frequency as found. Fig.4 (b) Figure 4:- Variation of (a) Q.sca for spherical and (b) Q.sca and hydrated water content in sand particle at 24 GHz Fig.4 (a & b) Shows the following results. 1. Scattering efficiency is independent of particles shape till size less than 40 um. 30

5 Q.ext at 37 MHz with various values of hydrated water content Q.ext at 37 MHz with various values of hydrated water content 2. Tetrahedral shaped particles size after 40um, show more scattering efficiency than other shapes considered in the study. And Spherical particles being smooth particles show less scattering than other shaped particles. 3. Rectangular and spherical particles show less attenuation in signal after 20% amount of hydrated water content in sand particle. 4. In spherical shape signal scattering (Q.sca) with approximately 6-7 time higher than the signal scattering (Q.sca) 5. In rectangular shape signal scattering (Q.sca) with 30 % hydrated water content in particle is approximately 9-10 time higher than the signal attenuation (Q.sca) with 0.3% hydrated water 6. All times signal scattering efficiency (Q.sca) is increase with increasing the value of hydrated water for all shapes present in the Sand/dust particle at 24 GHz frequency as found. 3.5 Variation of Q.ext at 37 GHz with Fig.5(a & b) shows that the Q.ext value for the spherical and rectangle shapes at 24 MHz with change the value of hydrated water(0,5,10,15 and 20) % and the size is also vary. The signal attenuation (Q.sca) values on 20 % hydrated water for rectangle shape is approximately 1.48 times higher than the signal attenuation (Q.ext) on 20 % hydrated water content for spherical shape of 100 um particle size. 6.0x10-2 Fig.5 (a) 6.0x10-2 Fig.5 (b) Figure 5:- Variation of (a) Q.ext for spherical and (b) Q.ext and hydrated water content in sand particle at 37 GHz Fig.5 (a & b) Shows the following results. 1. Signal attenuation is highly dependent of particles shape and value of hydrated water content present in the sand/dust particle. 2. Rectangular particle are sharp edged particles show attenuation efficiency more than spherical shapes considered in the study with increase in amount of water. 3. Rectangular and spherical particles show less attenuation in signal after 10% amount of hydrated water content in sand/dust particle. 4. In spherical shape signal attenuation (Q.ext) with 20 % hydrated water content in particle is approximately times higher than the signal attenuation (Q.ext) with 0 % hydrated water content in particle. 5. In rectangular shape signal attenuation (Q.ext) with 20 % water content in particle is approximately times higher than the signal attenuation (Q.ext) with 0 % water 6. Here the signal attenuation is highly increase with increasing the value of water in particle at 37 GHz frequency as found. 3.6 Variation of Q.sca at 37 GHz with Fig.6(a & b) shows that the Q.ext value for the spherical and rectangle shapes at 37 MHz with change the value of hydrated water(0,5,10,15 and 20) % and the size is also vary. The signal attenuation (Q.sca) values on 20 % hydrated water for rectangle shape is approximately 1.40 times higher than the signal attenuation (Q.ext) on 20 % hydrated water content for spherical shape of 100 um particle size. 31

6 Q.sca at 37 MHz with various values of hydrated water content Q.ext with various frequency and shapes for 100 um particle Q.sca at 37 MHz with various values of hydrated water content 8.0x x x10-5 attenuation (Q.sca) with 0 % hydrated water content in sand/dust particle. 6. All time signals scattering (Q.sca) efficiency is increase with increasing the value of hydrated water for all shapes present in the Sand/dust particle at 37 GHz frequency as found. 3.7 Variation of Q.ext at 14,24 and 37 GHz with variation of Particle Morphology (shape) and Hydrated Water content in 100um Sand/Dust Fig.7 shows that the Q.ext value for the spherical and rectangle shapes at 14, 24 and 37 MHz with change in the value of hydrated water (0.3,5,10,20 and 30) % for 14 and 24 GHz and (0,5,10,15 and 20) for 37 GHz the size is 100um. Fig.6 (a) 8.0x x x GHz Sphrical 14 GHz Rectangle 24 GHz Sphrical 24 GHz Rectangle 37 GHz Sphrical 37 GHz Rectangle 4.0x10-5 Fig.6 (b) Figure 6:- Variation of (a) Q.sca for spherical and (b) Q.sca and hydrated water content in sand particle at 37 GHz Fig.6 (a & b) Shows the following results. 1. Scattering efficiency is independent of particles shape for particles with size less than 40 um. 2. Rectangular shaped particles with size > 40um, show more scattering efficiency than that of other shapes considered in the study. And Spherical particles being smooth particles show less scattering than other shaped particles. 3. Rectangular and spherical particles show less attenuation in signal after 20% amount of hydrated water content in sand particle. 4. In spherical shape signal scattering (Q.sca) with 20 % hydrated water content in particle is approximately 5 time higher than the signal scattering (Q.sca) with 0 % hydrated water content in particle. 5. In rectangular shape signal scattering (Q.sca) with 20 % hydrated water content in particle is approximately 6-7 times higher than the signal Hydrated water value (%) presant in 100 um particle Fig.7 Figure 7:- Variation of Q.ext at 14, 24 and 37 GHz with varying Particle Morphology (shape) and Hydrated Water content in 100um Sand/Dust Particle. Fig.7 Shows the following results. 1. Rectangular particles being sharp edged particles show higher attenuation efficiency then spherical shape sand/dust particles. 2. The spherical shape particles show decrease in attenuation efficiency after 20% hydrated water content in sand/dust particle at 24 MHz frequency. 3. After a particular value of hydrated water, the signal attenuation (Q.ext) starts to decrease as it is depends on the complexity of a particle shape. 4. Here the signal attenuation (Q.ext) highly increases till 10% value of hydrated water content but the degree of increase slows down post 10% value of hydrated water content. 4. CONCLUSION Based on research done, it has been observed that microwave signal attenuation depends upon particle morphology (shape and size), wavelength and the hydrated water content in particle. On increasing the content of hydrated water in the 32

7 sand/dust particle the loss of the microwave signal was found to increase. The signal attenuation was found to increase on decreasing wavelength and increasing size of the particle.the microwave signal attenuation depends on the article nonsphericity. Rectangle shaped particle have maximum value of extinction and scattering (Q.ext and Q.sca) as rectangle shaped particles are sharp edged particles. While the spherical shaped particles have lesser value of extinction and scattering (Q.ext and Q.sca) as these are smooth particles. We see that at a certain particle size the value of scattering (Q.sca) starts increasing sharply. That certain size is called the size threshold of particle. The size threshold of particle, where attenuation increases exponentially is the function of the wavelength (λ), particle shape and hydrated water content. The size threshold decreases with the increase in frequency, particle shape complexity and hydrated water content present in the sand/dust particle. Here it has been found that all time signals scattering (Q.sca) efficiency increases with the increasing value of hydrated water for all shapes present in the Sand/dust particle. In a conclusive remark, the signal attenuation (Q.ext) is maximum in microwave region. It has been found to be significant for higher content of hydrated water, maximum value of particle size and shorter the wavelength (λ) for rectangular shape particle. But in the case of spherical shape particle, the signal attenuation (Q.ext) is maximum in microwave region which is subject to maximum value of particle size, shorter the wavelength (λ) and a limited % value of hydrated water content. After that value of hydrated water content the signal attenuation (Q.ext) starts to decrease in case of 24GHz frequency. The effect of hydrated water content on signal attenuation (Q.ext and Q.sca) starts to minimize after a particular value of hydrated water content in sand/dust particle as seen. 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