Extensive amplitude scintillation measurements were made simultaneously at 2.075 and 30 GHz on earth-space propagation paths. These measurements were performed as the Applications Technology Satellite (ATS-6) was moved slowly from a synchronous position over India to a new synchronous position over the United States. The variance, path loss, covariance, and spectra are discussed as functions of the path elevation angle. These results are also compared with earlier simultaneous scintillation measurements at 20 and 30 GHz during the movement of ATS-6 to its position over India

Devasirvatham, D. M. J.

Hodge, D. B.

Theobold, D. M.

English

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https://ntrs.nasa.gov/search.jsp?R=19780020356 2020-03-22T02:47:41+00:00Z
y '	 5 C	 r^o ^f^ l4 G J`
MAI l	 -
„';FL ITUCE SC,N I! LATI0-; AT 2 A%0 30 GNz
v.. Er.:iH arW ►+CE i'N7nS
Thectold, e- D. ", J. Devasirvathan
1
The Mlo Sate Ur,iver!itv1o.
Columbus, Ohio 43212
(NASA-CR-156780) AMPLITUDE SCINTILLATION AT
	 N78-28299
2 AND 30 GHz ON EARTH SPACE PATHSC( hio
1	 State Univ., Colurrbus.) 9 p HC A02/MF A01
CSCL 20N	 Unclas
G3/32 27057
Technical Report 4299-3
February 1977
Prepared for
National Aeronautics and Space Administration
GODDARD SPACE FLIGHT CENTER
Greenbelt, Maryland 20771
'iQ; .
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OnTGTNTA T-, p,A ^ r IS
OF
Ll
TECHNICAL REPORT STANDARD TITLE PAGE
1. Report No.	 -^ —_ — ^Z (eOVerwre •nt Attetsrew No	 3 Retrpiewt's Catalog He
f /'ToTo «► S.11adri ..
	 _..	
- i; Repnr ► 6ii^
I
AMPLITUDE SCINTILLATION AT 2 AND 30 GHz 	 +February 1977ON EARTH SPACE PATHS	 A r erforrnrny o•ganrrarren ee4e
' 1 Aulher(sl 	 e- Perlerrnrnq Orgewr+errew Reper r Ne. 1
I D.B. Hodge,_D.M._ Theobold,.D.M.J._Devasiryatham 	 _	 4299`x-1 Ierhrrwrnq Orgonicetiew Nowre end Address 	 10. Merl Unit He	 i
I	 The Ohio State University ElectroScience
Laboratory,p	 (ii Contract ar c:nw1 NoDe artment of Electrical	 ^
Engineering, Columbus, Ohio 43212 	 -NAS5-22575
I	 -	 -	 -	 _ .13 T t pe of Reoorr and Perk! Covered
er12. 3wonsinq Ag"ey I"& end Address
NASA, GSFC	
Type II
Greenbelt, Maryland 20771
	
(Technical Report
1	 I E. Hi rschmann, Code 951, Technical Officer Spow+orrnq Agency Code —
^TS. Swpp l ementory Notes
Extensive amplitude scintillation measurements have been made
simultaneously at 2.075 and 30 GHz on earth-space propagation paths.
1	 These measurements were performed as the Applications Technology
I	 Satellite (ATS-6) was moved slowly from a synchronous position over
India to a new synchronous position over the United States. The
	 I
variance, path loss, covariance, and spectra are discussed as
	 i
functions of the path elevation angle. These results are also
compared with earlier simultaneous scintillation measurements at
20 and 30 GHz during the movement of ATS-6 to its position over
India [1,2].	 I
This report contains the text of a paper to be presented at the
URSI Commission F	 Open Symposium on Propagation in Non-ionized
Media at LaBaule, France, April 28-May 6, 1977.
1
17. Key ward. (Selected by Autfter(s)) - --	 —	 18 Dis ►riburron Storerwent	 -	 ---
Millimeter wave	 ATS-6
Scintillation
Earth Space	 It
Propagation	 __
19. Security Clossil- (of this raper ►► 	 20. Se<uney Clanil, (el this page) 	 J21 No of Peqe+	 12 Price*
e For sole by the CleutoRhoute for FeJerel Scientific and Technical Infotmatton, ^nnpftrld, Slrytnta 2201.
1
TABLE OF CONTENTS
Page
I	 INTRODUCTION
	
1
REFERENCES
	
5
ii
i
30 GMs
W'FL:7 :C SC1(IlIll;,'(t,: , 	 ViO 3:1 GI': X LA4TP S p% CE D;'11S •
U. D. (lodge, U. 11. Theobold and U. Ii. J. UevasirvathamT l^e Uojo State University LlectroScience Laboratory
Uepartment of Clectricd1 Lngineering
Columbus. Ohio USA 43212
SUiiIARY
Extensive amplitude scintillation tieasurer,ents
have been nade simultaneously at 2.075 and 30 Gllz on
earth-space propagation paths. These measurenents
were perfo m ed as the Applicatinns Technology
Satellite (ATS-6) was moved slowly from a synchronc-;
position over India to a new synchronous position
over the 'rited States. The variance, path loss,
covariance, and spectra are discussed as functions of
the path elevation angle. Tlcse results are also'
compared with earlier simultaneous scintillation
measurements at 20 and 30 Gllz during the novenent of
ATS-6 to its position over India [1.2].
1 - 111TP.ODUCTIOiI
The novenent of ATS-G fron a synchronous
position over India to a nes, synchronous position
over the United States was such that the change in
the elevation angle of the propagation path was less
than one degree per day. Thus, a unique opportunity
was presented to neasure scintillation characteris-
tics as a function of elevation angle. Phase-locl:-
loop receivers were irplenented at Columbus, Ohio,
U.S.A. to receive the 2.075 and 30 Gllz ATS-6 beacon
signals. 4.6 and 9.1 n Cassegrainian t ype horn fed
parabolic reflector antennas were used. The neasured
system ilargins were 48 and 55 dB, respectively. The
received signals 1+ere digitally recorded at a rate
of 10 samples per second at all tines during the
experiment and at a rate of 200 samples per second
on demand; all of the data presented in this paper
were derived from the 10 sample per second recordings.
Thirty hours of simultaneous two frequency data
were collected between August 29 and October 25,
1976; these data corresnond to elevation angles
ranging from -0.7° to 43.9° (not corrected for re-
fraction). Samples of these raw data are shown in
Figures 1, 2 and 3 for elevation angles of 0.38°,
2.82° and 22.34°, respectively; in these Figures the
2.075 and 30 Gllz signals are shown with respect to
the mean over the 30 minute data period presented.
At the lower elevation an g le the peal • -tn-peak scin-
tillation exceeded 7 dB at 2.075 Gllz and 20 dB at
30 Gllz. These peak-to-peal. scintillation values
decreased with increasing elevation angle except that
enhanced scintillations were often observed during
the presence of non-preci p itatinn cumulus clouds
along the propagation path. Althounl, the character
of the scintillation appears to change as the ele-
vation angle increases, examination of the spectra
of these signals, presented later in this paper, do
not show significant differences other than the
general reduction of all frequency components. These
scintillations were found to occur at all tines
during the experiment regardless of prevailing
atrospheric conditions. All of the data presented
in this pa per correspond to tines when there was no
discernible precipitation on the propagation path.
'Th e
 .or reports in this Pa per WAS suppnrted in part
by Contract VSO-2557; Letuenn ;lational Aeronautics
and S pace Adl inistratlon and The w0 o State
University pesearci, Foundation.
OAT 243 H q 17 MIN 24 SEC 3 45EC 679
EL - 0.38•
2 GH:
a
of
lu	 is	 20	 25	 30
TIME (MiN)
Figure 1. Received signal on day 243.
OAT 246 HR 1	 MIN 59 5EC 20 MSEC 663
°_-	 EL-2.82•
2 GHe
_o
o I
0	 30 GHz
I	 I
J
o	 ^	 ^
i
^I
IJ	 15	 20	 is	 X
TIME IM IN)
Figure 2. Received signal on day 246.
^ rw+^ uu AbEf ^
CE MR 011AIATY
I;:Qr '53 -01 19 MIN 13 SEC 0 M - t'_ ?79
EL - 22.34-
	
1	 2 CHI
	
m' I	 r .ro
	o 	 -
30 CHI
o
°
	
J	 S	 10	 Is	 2u	 25	 30
TIME I M I N I
Figure 3. Received signal on day 263.
	
__	 VARIANCE
	
I	 • 50 CHI 1976
	c iY'	 o 50 CHI 1975
2 CHI 1976
	
-0p
	
L POWER LAW
mQ
o	 •t	
-
	
^w	 •	 p	 0
0	 ••
v	 p
o
pJ
	
r	
'
°a-
	
0	 S	 10	 IS	 20	 .S	 30	 SS	 Y0	 Ys
ELEV. (DEG)
Figure 4. Variance of received signal amplitude.
The variances of these signals have been
averaged over each data period and are shown in
Figure 4 as functions of elevation angle. These
variances were defined as
21^' (Vi-Vi)2
o - 10 
109101172
	
(1)
i
VVtjGVAL PAGE [4
Qj rMjt QUALITY
where the V 1 are the sdr p les of the received signal
amplitude corrected for receiver nunlinearitlrs and
71 is the average over the N samples. The variances
were calculated for data Intervals of 3.4 minutes,
and these variances were then averaged over edCh data
period of 30 to 60 minutes. The spread of the
variance over such a data period was often as hign as
10 d0. The variance defined in this manner represents
the ratio of the power contained in the non-zero fre-
quency components to the power contained in the zero
frequency component of the signal, Also Shown In
Figure 4 are the 30 GHz variance data derived from the
earlier set of measurements; these agree well with the
current tieasurenents. Theoretical curves have been
included to demonstrate the variance behavior under
U1e assumption that the variance is proportional to
the 11/6 power of the path length through a 9 km
spherical, hocogeneous atmosphere. It can be noted
that the Measured variance agrees well with this
model.
A plot of the variance of the log amplitude of
the received signal is shown for comparison in
Fi gure 5. here the variance of the log amplitude is
defined by
11
aloq	 i1l 
(V log i	1P 
ogi)2/N	 (2)
where V ion - 20 log l0 V i ;	 (3)
f
the subsequent processing was identical to that
described above. It is interesting to note that the
variance in log amplitude reveals a rather abrupt
reduction in level for elevation angles above 6- that
is not found in the variance of the amplitude pre-
sented earlier. This difference can lead to substan-
tially different interpretations of the same data
depending only on the method of data processing
chosen.
LOG vARIAniCE
J
. 2 GHz
r }O CHI
i
J	 .^
ccQ
I.
G
u	 s	 10	 1s	 20	 2s	 w	 3s	 to	 +.
ELEv. 10E61
Figure 5. Variance of log amplitude.
t	 i
I
1
t
I
;I
r
1The c,-Naridn^:e	 the 2.07j and 31 utli
signals is shown in Figure 7 along wit h that for the
G0 a 1 4	 ,i,2 data I ea',^ied earner L,'] and the
theoretical covariance p redicted Dy Lee and harp (J].
Although the spread of the covariance is large, the
avera ,le over t he entire data base agrees well with
ve t enretical prediction. Tile covariance is shown
in Figure d as a function of elevation angle; here it 	
4 
1
is noted that the covariance decreases as the ele-
vatinn angle i ncreases. Both the covariance of the
amplitudes and the covariance of the log amplitudes
are shown in this figure for comparison; though some	 (,'
divPrgencr. is found at the lowest elevation angles
they are found to agree well at higher elevation 	 k
angles.
g,	 POWER
0
N ^ • 1 n 	 Q
m	 •
• 2 GNs
n 30 Gms
O TEXAS POINTING
n
s.
r ^
	 ^
o I
0	 S	 10	 IS	 20	 2S	 !0	 JS	 VO	 Vs
ELEV. (DEG)
Figure 6. Average power in zero frequency component
Tile average power contained in the zero fre-
quency component of the received signal is plotted as
a function of elevation angle in Finure G; the
reference in this figure is arbitrary. The dramatic
reduction in level at an elevation of 9.3' is due to
the fact that the s pacecraft antennas were directed
toward Texas rattier than Ohio during this data period.
A substantial reduction in the received power level
below that predicted by simple atmospher i c path loss
calculations at lower elevation angles is also noted;
this behavior nas been observed earlier by 11cComicl:
and Maynard [3].
0,
•
COVAR I&NCE Or'
0.!
o LOG AMPLITUDE
X AMPLITUDE
0. 2
U	 IN
.4	 nn
i0.1	 X	 r	
r
o'	 •	 n 	 r r	 r
°	
r r	 •	 r
 10	 20	 !0	 40
	
ELEVATION (DEGREES)
	 all
-0.1
n
-0.2
Figure H. Covariance versus elevation angle.
4
Spectra of the received signals are shown in
Figures 9, 10 and 11; these correspond to 3.1 minute
intervals from the data periods shown in Figures I,
2 and 3, respectively. These spectra all stiow a
characteristic decay with frequency in the range from
ap p roximately 0.1 to 1.0 Hz. The spectra tend to be
relatively flat for frequencies above and below that
range.
Additional processing of these data is in
progress and will be reported in a future publi-
cation.
to
	
00
	
w 1 915 DATA	
• AVE FOR EACH DATA PERIOD
•	 0 AVE OVER ALL DATA PERIODS
i
1 06
0
^i LEE a HARP
0,
1
	
02
	 1f 1916 DATA
n
	
I	
,	 6 1 10	 20	 40 60 10 DO
r REDUE •rc ♦ RATIO
Figure 7. Covariance versus freLuency ratio.
0lt1G1NAI: PI MA	 3
^.	
OF POOR QU,}1L1TN
I
II
-smuk_	 v
G ^
P OWER 5PECTRUM
2	 GHZ RECEIVER	 x
^NEL.	 0.38
o T:ME
	
243	 1724Z	 cr2
cr Q
^°^ l	 uaI	 l	 t	 I
m I	 ^Itb ! I	 ; )J	 J t
m^
m^
POWER SPECTRUM
2	 GHZ RECEIVER
EL.	 2.82
TIME
	 246 0209 Z
'
44 1 0' 2 367631 0'^	 3+	 fO	 0	 +iWo	 d
FRED. IN HZ	 FRED. IN HZ
Figure 9a. Power spectrums - day 243.
	 Figure 10a. Power spectrum - day 246.
0
POWER 5PECT9U4
30 GHZ RECEIVER	 cr-
EL. 	 0.38 Cr
TIME	 243	 17247
I,II	 J
iI!	 ^`^ ^ I ^
	 I	 z
► h	 IM^I ' 
ILL,
dill i	 ^ r.	 /^ ^,	 ^	 III ^ I	 1^+ !I
iil
	
„	 1	 ^.	 ^ 	 I ^^ 	 ^ I I^
o_	 I^
+	 9 p	 2	 3+ S G J63'1 Q`	 !+	 Q'	 u	 76	 ^" 2	 + 5 6 7B	 [(' 2	 3 r
FRED. IN HZ	 FRED. IN M1
Figure 9b. Power spectrurs - day 243.
	 Figure 10b. PoweP spectrum - day 246.
0
Cr
U.j o
Y'?
cr
u
0
3 ^
OJW
QJ
O
co
J
J
^ n
+ S
POWER 5PECI9UM
3U GHZ 9E;,_ IVER
EL.	 2.82
TIME	 246 0209 1
plat Aim PAGE L1
j ^l.l'C'tl
	 Qg ZWR QUALITY
4
v
r0
POWER 5PECI9J4
Cr	 2	 GHZ RECEIVER
~ ti	 EL. 22.34
Q	 TIME	 263	 Lb32t
CJ
3 7
nJ
U.1
M
CLUJ Ilia	 ^'t
a-
i^
FO, u	 -a ,^	 2	 u	 CP	 +
FREU• IN HZ
W
REFERENCES
[1] "Scintillations Observed on the ATS-6 20 and 30
Gllz Damlinls," D. B. (lodge and L, n, The000la,
URSI/US11C Meeting, Boulder. Colorado, October
1975.
[2] "ATS-6 Millimeter Wavelength Propagation
Expe riment," D. B. Hodge, D. M. Theobold, and
R. C. Taylor, Ohio State University Electro-
Science Report 3863-6, January 1976.
[3] "neasurerents of S.H.F. Tropospheric Fading Along I
Earth-Space Paths at Low Elevation Angles,"
K. S. McCormick and L. A. Maynard, Electronics
Letters, Vol, 8. P. 274, 1972.
[4] "heal: Scatterinn in Random Hedia. With Appli-
cations to Remote Probing," R. W. lee and
J. C. harp. Proc. IEEE, Vol. 57. p. 375, 1969.
a
Figure Ila. Power spectrum - Jay 263.
J
POWER SPECTRUM
r	 I
u o l
30	 GHZ	 RECEIVER
— 
v EL.	 22.34
Cr TIME	 263	 18327
u
3
OJ
I'	
^^^^^'^'
co
+	
I
II I I '	
II	 r
li	 I	 i+ r^O)	 I
^ I I	 III	 ,,	 t^^;	 I I
0
i	 •^
p'p' ?	 3	 + 56te9 , 0	 2	 +
FREQ.
	 IN	 HZ
•
Figure llb. Power spectrum - dW 263.
.,
4


Amplitude scintillation at 2 and 30 GHz on earth space paths

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