Propagation Effects Handbook for Satellite Systems - DESCANSO ...

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s ~ z 0 1.00 BEAMWIDTH (DEG) 0.10 0.01 80 Ill 1 I I I I 111’ 111 I I 80 — 70 60 — 5o— PATH LENGTH L my) 1 I I 1 11111 I I I 1 1 1 40”’ 9,.0 2 3 4 5 6789,.1 2 3 4 5 6 7 APERTURE DIAMETER (M) FOR 30 GHz Figure 6.5-15. Realized Gain Versus Beamwidth or Aperture Diameter at 30 GHz 6-100
. . 6.5.5.2.2 Spatial Diversity. Paths operating at very low elevation angles with narrow beamwidth antennas may experience unacceptable fading due to scintillation and multipath effects. The required reliability may be regained by the use of spaced site diversity. A site separation greater than 300 m transverse to the propagation path has been suggested (CCIR-1986b, Rpt 564-3) as necessary to alleviate severe turbulence-induced effects. In effect, separation on the order of or larger than the scale size of the largest inhomogeneities in refractive index along the propagation path, and especially near the surface where refraction is greatest~ results in decorrelation of the instantaneous signal fluctuations and hence improved performance. The aperture effects of large antennas may be circumvented if several phase-locked antennas, each with relatively wide beamwidthl are employed in an array to achieve the desired system gain. Of course, overall fade margins will be on the order of that for a single element, but angle-of-arrival effects are eliminated. In addition, such an array alleviates the need to mechanically track a geosynchronous satellite, as is necessary with large aperture, narrow beamwidth antennas. 6.5.6 A Sample Computation of Siqnal Fluctuations and Gain Degradation In this section examples of the parameters described in Section 6.5 are worked out for a hypothetical ground station located at Columbus, Ohio with a 4.6m (15 ft) diameter parabolic antenna observing a 28.56 GHz COMSTAR beacon at 10 degrees elevation angle. Actually, the COMSTAR satellites are not at that low an angle, but in order to demonstrate the effects of gain reduction this value has been arbitrarily selected. 6.5.6.1 Amplitude Fluctuations. The variance of the received signal amplitude is calculated using the expression in Section 6.5.2.2. The full half-power beamwidth c/fda = (70)(3x108m/see)/(28.56x10gsec - B in degrees is 70A /da = 70 1) (4.6m) = 0.16 degrees. The 6-101
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1 6.1 INTRODUCTION 6.1.1 purpose CH
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,s Table 6.1-1. Guide to Sample Cal
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I . . 6.1.4 Other Propagation Effec
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. . collisions at normal atmospheri
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D 1000 100 10 1 U.S. Standard Atmos
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Frequency (GHz) 10 15 20 30 40 80 1
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If PW is not available from local w
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. . The equivalent heights for oxyg
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m t TEMPERATURE rC) o 5 10 15 20 25
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6.3 PREDICTION OF CUMULATIVE STATIS
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LSTATION LOCATION AND ELEVATION STE
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The models require the following in
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I z za E 100 g w ~ z z K 50 a) ALL
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B . . . t- I I I I I 1 11/1 - . . .
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.- . 9 s@EQ - If Z S D, compute the
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1 0.02 0.05 0.2 0.5 4. Compute D: U
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I . ,. . ~ q 8 H v ~ 1.0 0.8 0.6 0.
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Step 6 Calculate the attenuation ex
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m I : STEP 1 SELECT CLIMATE ZONE FR
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9 10.OOOO 1.0000 0,1ooo 0.0100 0.00
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1 6.3.3 Estimates of Attenuation Gi
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● We now proceed exactly as in th
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STEP 1 GIVEN: STATION PARAMETERS SA
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. B . . . 4. Repeat the process for
Page 49 and 50: . . ● 100 10 1.0 .1 .01 . . RAIN
Page 51 and 52: not normally available~ but empiric
Page 53 and 54: ● The intensity-duration-frequenc
Page 55 and 56: - GIVEN: STATION PARAMETERS OPERATI
Page 57 and 58: m I s 70 2(J I 10 0 a) BY SEASONS
Page 59 and 60: .“ ● change in rain rater the r
Page 61 and 62: m To x o 6 x(n wux!- (5 zawwvxw x 1
Page 63 and 64: ● ✎ ✎ ✎ 10 1 0.1 0.01 0 . -
Page 65 and 66: ● ✎ ✎ ✎ appears to be gener
Page 67 and 68: 6.4.2.3 Statistics of Microwave Eff
Page 69 and 70: ● For each hour’s observations,
Page 71 and 72: Plots of noise temperature and atte
Page 73 and 74: .- I where Lf is the fog extent~ in
Page 75 and 76: than a minute and on spatial scales
Page 77 and 78: . . . 022 = angle-of-arrival varian
Page 79 and 80: B . . Figure 6.5-2 represents the a
Page 81 and 82: - . . , 1 I t , 3 , I 1 # 1 1 aJ 0a
Page 83 and 84: I . . -. % i ! ~ * 76.00 I h 60.00
Page 85 and 86: I where the constants are the same
Page 87 and 88: .U . . \ Table 6.5-1. Fading Data P
Page 89 and 90: o -5C \ A — . \ \ \ \ N- ● ●
Page 91 and 92: I 1 \ 0,, FADE DEPTHS I 1 l.d 0.1 1
Page 93 and 94: 9 m ELEVATION ANGLE [DEGREESI ELEVA
Page 95 and 96: Figure 6.5-12 is an example for thi
Page 97 and 98: equal. The fade distributions resul
Page 99: m . ANTENNA BEAMVVID~ (DEG) d o 0 w
Page 103 and 104: fluctuation power at 1 Hz is on the
Page 105 and 106: develops (Pruppacher and Pitter-197
Page 107 and 108: .8 where: f = frequency, in GHz r =
Page 109 and 110: B . k 11.7 26 \ QHz DATA, CTS A VPl
Page 111 and 112: \ for the 11.7 GHz CTS beacon at 50
Page 113 and 114: ● these do not correlate well wit
Page 115 and 116: . However the XPD dependence on ele
Page 117 and 118: -. 50 40 30 20 10 0 . T(XPD < ABCIS
Page 119 and 120: 9 electrostatic fields discharge ra
Page 121 and 122: , f w m I
Page 123 and 124: . XPD 2 = XPD1 - 20 lo91~ f ~ 1 0.4
Page 125 and 126: ● 3.0 14 0.6 0.3 0,1 0.0s 0.03 0.
Page 127 and 128: where, for example, for the frequen
Page 129 and 130: L .- . ., not appear to be sufficie
Page 131 and 132: D ‘1 may be considered to be rece
Page 133 and 134: D - 0 m a 80 60 40 20 0 -20 \ — i
Page 135 and 136: m I s 1 \\ I , t Frequency (GHz) Fi
Page 137 and 138: -. Table 6.8-1. Cumulative Statisti
Page 139 and 140: D - The propagation margin is then
Page 141 and 142: 1- * w -180 -190 -m -21 / ---+---4~
Page 143 and 144: - . . 6.9 UPLINK NOISE IN SATELLITE
Page 145 and 146: 280 260 240 220 200 180 160 140 120
Page 147 and 148: 6.10 REFERENCES Ahmed, I.Y. and L.J
Page 149 and 150: ● International Telecommunication
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Atmospheric Emission observations,
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8.6 and 3.2 mm Radio Waves by Cloud
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I Strickland, J.I. (1974), “Radar
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D Wulfsberg, K.N. (1964), “Appare
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