Extensive antenna-noise temperature measurements at 1.6 GHz (L-band) were made using a 1.2 m (4 ft. diameter) parabolic dish antenna mounted on the flying bridge of a modern 15,690-ton, commercial-container ship. Both in-harbor and at-sea radiometer measurements were made that indicated a steady background, antenna-noise temperature value slightly less than 70 degrees Kelvin (K) at elevation angles of 5 percent, and greater, at 1.6 GHz. A comparison of theoretical and measured values indicate excellent agreement within about 5K for at-sea data. These measurements are helpful to RF equipment designers of maritime, L-band shipboard terminals for operation with the two, geostationary, maritime satellites, Marisat-A and -B

Hill, J. S.

Taylor, R. E.

English

International Telemetering Conference Proceedings / October 14-16, 1975 / Sheraton Inn, Silver Spring, MarylandExtensive antenna-noise temperature measurements at 1.6 GHz (L-Band) were made using a 1.2 m (4 ft. diameter) parabolic dish antenna mounted on the Flying Bridge of a modern 15,690-ton, commercial-container ship owned by the United States Lines. Both in-harbor and at-sea radiometer measurements were made that indicated a steady background, antenna-noise temperature value slightly less than 70 degrees kelvin (K) at elevation angles of 5°, and greater, at 1.6 GHz. A comparison of theoretical and measured values indicate excellent agreement within about 5K for at-sea data. These measurements should be especially helpful to RF equipment designers of maritime, L-Band shipboard terminals for operation with the two, geostationary, maritime satellites, Marisat-A and -B.International Foundation for TelemeteringProceedings from the International Telemetering Conference are made available by the International Foundation for Telemetering and the University of Arizona Libraries. Visit http://www.telemetry.org/index.php/contact-us if you have questions about items in this collection

Taylor, Ralph E.

Hill, James S.

The University of Arizona

L-Band, 1.2 m Parabolic Antenna-Noise Temperature Measurement

NASA Technical Reports Server

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7
 ^5^/ Q
L-BAND, 1.2m PARABOLIC
ANTENNA-NOISE TEMPERATURE
MEASUREMENT
RALPH E. TAYLOR
JAMES S. HILL
('1ASA-TC-X-70952)	 I-FAND, 1.2 s PA R AEOLIC	 N75-30391
A4TFNNA-N0ISF. TEMFFFAIU r °_ MEASUfiEMT I NT (NVA)
7 p HC $3.25	 CSCL 17E
Unclas
63/32 347U6
915
^	 141402 b	 ,,^
JULY 1975
6^ z IILi^^^^
^hv^ 1:0	 GODDARD SPACE FLIGHT CENTERGREENBELT, MARYLAND
Prepared for presentation at International Telemetering Conference,
ITC/USA/ 1 75, October 14, 15 & 16, 1975.
(Washington, D. C.)
L-BAND, 1.2 m PARABOLIC ANTENNA — NOISE TEMPERATURE MEASUREMENT
By RALPH E. TAYLOR and JAMES S. HILL
Summgq. - Extensive ante , ina-noise temperature measurements a.' 1.6 Gliz
(I.-Band) were made using a 1 2 in 	 ft. diameter) parabolic dish antenna moun',9d
on the Flying Bridge of a modern 15,690-ton, commercial-container ship owed by
the United States lines. Both in-harbor and at-sea radiometer measurements were
made that indicated a steady background, antennu-noise temperature value slightly
leas than 70 degrees kelvin (K) at elevation angles of 5°, and 6Teater, at 1.6 GHz,
A comparison of theoretical and measured values indicate excellent agreement
within about 5K for at-sea data.
These measurements should be especially helpful to RF equipment designers
of maritime, L-Band shipboard terminals for operation with the two, geostationary,
maritime satellites, Marisat-A and -B.
Introduction, - The United States Lines 15,690-ton, commercial-container ship,
"American Alliance," was selected for the installation of an experimental, I. Band,
Shipboard Terminal using a 1,2 m-diameter (4 ft,), parabolic dish antenna for re-
ception of satellite signals at 1.6 GHz (1,21.
Antenna-noise temperature measurements were made at 1.6 GHz, from June
16-20, 1974, onitoard the "American Alliance," while berthed at Port Elizabeth,
New Jersey (USA), and at sea while enroute from Port Elizabeth to intermediate
ports along the Eastern Coast of the United States to as far south as SaVa nnah,
Georgia. While at sea, the ship maintained a minimum of 20 miles distance from
the shoreline to minimize line-of-sight interference from the shore.
Shipboard Installation. - Various subsystems of an operations.] L-Band Ship-
board Terminal provided essential equipment including a 1.2-in-dia. paraboloidal
(dish) reflector, without radome, with 24 dB gain above isotropic at 1.6 GHz. Re-
ceiver subsystems resulted in a system noise figure of 5.9 dB. The 1.2 m antenna
contained a right-hand circularly polarized, prime-focus. RF feed for 1535 - 1660
Mllz operation.
A make-shift antenna stand, and tripod mount with azimuth-elevation swivel
axes, were used to position the dish antenna centerline approximately 2.8 m above
the deck of the Flying Bridge for antenna mainlobe clearance (Fig, 1). The above-	 V5
deck configuration for the vessel, "American Alliance" is given in .Fig. 2. The
antenna stand was positioned on the starboard side of the ship's "Flying Bridge",
in the approximate location selected tentatively for an operational L-Band Ship-
board Terminal. A 12-m-length, low-loss coaxial cable ran from the output termi-
nal of the 1.2 m dish antenna to a radiometer located in the ship's Wheelhouse im-
mediately below the "Flying Bridge."
Antenna-Noise Temperature Measurements. -With the 1.2 m antenna positioned
on the Plying Bridge (Fig. 1), antenna-noise temperature at a center frequency of
1.6 Gliz was measured using an Airborne Instruments Laboratory Type 2392B
Mr. Taylor is with National Aeronautics and Space Administration, t;oddard Space Flight Center, Greenbelt,
Md.
Mr. Hill is with RCA Service Company, Springfield, Va.
41.2 m (4 FT.)
PARABOLIC
ANTENNA
FLYING
BRIDGE ^r
^661FT.
AMERICAN
ALLIANCE
Fig. 1. 1 . 2 m dish antenna tripod and stand on
Flying Bridge
CONTAINER
CARGO
RADAR
ANTENNA
SCANNER
PLATFORM
Fig. 2. Above-•ueck configuration of vessel, "American Alliance."
TA 12m LENGTH
LOW LOSS
CABLE
1.8dB LOSS
A
1.2m DISH ANTENNA COAXAL r
SWITCH
B
VARIABLE
ATTENUATOR
Tref - 80 K 
f
COLD REF
LOAD
LIQUID
NITROGEN
77 K
I DUMMY
LOAD
DUPLEXER
1.6 GHz i RECEIVE PORT
LOW-PASS	 LOW NOISE
FILTER	 AMPLIFIER
50 MHz I F IDOWN
CONVERTER
RADIOMETER F­110^X-Y
RECORDER
Fig. 3. Radicmeter for antenna -noise temperature measurements.
Radiometer (s] , and cold-load reference temperature ( liquid nitrogen, 77 K) located
in the Wheelhouse ( Fig. 3). A continuously-variable precision attenuator (ARRA*
rype 5614-60 L) was adjusted to obtain an equal output reading on the X-Y Recorder
for both switch positions A and B. Measurements were made then for the 1.2 m
antenna azimuth angles from 0 0 - 360 0 , in 20 0
 increments, and for elevation angles
from 0 0 - 90 0 , in 5° and 10° increments.
Since an apparent antenna-noise temperature was measured at the output end of
the 12 m coaxial cable (switch terminal A, Fig. 3), it was nacessary to compute
antenna-noise temperature T A , referenced to the 1.2 m antenna'.; output terminals,
considering the fixed 1 . 8 dB ttranr,mission cable loss. Two methods [4] were neces-
sary: Method 1 was used for computing values of T A less than, or equal to the
cold-load re`.c rence temperature, "1'^ r	 80 K; Method 2 was used for values of
TA ' T,, t = 80 K. A description of each method follows.
Method 1. -The apparent antenna-noise temperature TA, measured at switch
terminal A, is expressed as
T^ = T A, w + (1 - w) To (legs Kelvin (K)	 (1)
*Calibrated at 1.6 GHz both before and after sea tes'_ using calibrated sr u.dard signal generator and RF
power meter.
04
for 0 < w < 1 (dimensionless). Similarly at switch terminal B.
Tn 	T7 of a - ( I - a) To degs K	 (2)
for 0 < a 1 1 (dimensionless) where
antenna transmission line attenuation power loss
a	 = total attenuation (power loss) of variable attenuator, including
miscellaneous losses
T,61	 = cold-load reference noise temperature	 hO K
To = 300 K = ambient physical temperature of all transmission lines
Setting T^ = T,, from (1) and (2), and solving for T A gives,
a
T A 	 To +	 J, 	 To) degs K	 (3)
lim ( a/w) -- 0, TA 'I' o , max. Furthermore, (3) is used only for computing values
of TA < T r@f , corresponding to lower scale readings on the variable attenuator.
Method 2. -On the other hand for higher scale readings of the variable attenu-
ator, corresponding to values T A > T ref , T^ at terminal A is expressed in terms
of the noise temperature of the attenuation (41 as,
	
T^ = TA + (L, - 1) 'ro degs K	 (4)
for 1 < L" < .. Similarly at terminal B,
Tn	 Tref + (L, - 1) To degs K	 (5)
forl <L,,,<	 where
L, = antenna transmission line loss power ratio
L Q = total attenuation power loss ratio for cold-load reference arm
Again setting T^ = T Q in (4) and (5), gives a value of T A as,	 0
TA 	 Tref + To (La - Lj degs K	 (6)
Note that when L a
 = L,,, T A = T ,.f . Whereas Method 1 is used only for values of
T A < Tr e f , Method 2 is used only for values of T A > T r e f .
Test Reswi.. - Antenna-noise temperature measurements at 1.6 GHz were
made both at sea and in the harbor (Figs. 4, 5); in general, antenna-noise tempera-
tures were lower at sea. This is especially true of "hot spot"* noise temperatures
resulting from harbor-generated EMI (e.g., loading cranes, dock rotating machinery,
etc.). Also, a series of "hot spots" were identified as 1.6 GHz signals from the
NASA Applications Technology Satellite (ATS-6), in geostationary orbit at 94 W.
longitude (Fig. 4).
*Noise temperature greater than steady background noise temperature.
The majority of the "hot spot" noise temperatures, above 5° elevation angle,
disappeared as she "American Alliance" went to sea (Fig. 5). Exceptions are the
two "hot spot'' noise temperatures resulting when the 1.2 m antenna mainlobe
pointed toward the radar - scanner platform on the meet (65° elevation angle, Figs. 4
and 5, and when the Sun entered the mainlobe at 75 elevation angle (Fig. 5).
in general, the measured steady background noise temperature increased
sharply below 5' elevation angle (Figs. 4, 5). Lorwever, at angles greater than 10%
the steady component remains fairly constant vs, elevation angle from 10• - W.
The average background noise temperature varies, within this range of migies, from
50 K to 60 K, at sea; and from 65 K to 75 K, in harbor. Each data point ( dot), in
general, represents 18 independent measurements, obtained at azimuth angles from
0 0 - 360% in 20° increments. Antenna -noise temperatures not averaged include all
"hot spot" noise temperatures identified by circled X's.
Blake 1 51 gives theoret..:al values of T A for a ground-based antenna, at
1.6 GHz, as given in Table 1. A grot ad-based antenna within a few hundred feet
of the earth ' s surface is assumed. Steady backgrounds noise temperature data
points from Figs. 4 and 5 indicate close agreement, except at 0° elevatiw, angle.
Table 1
Comparison of theoretical vs, measured antenna-noise temperature at 1.6 GHz
Antenna-Noise Temperature (degs K)
Elevation Blake ' s 161	 In-Harbor Data At-Sea Data
Angle Theoretical Value	 (Fig. 4) (Fig. 5)
00 125 K	 150 K 95 K
5° 70 K	 68 K 68 K
10 0 62 K	 64 K 56 K
90 0 55 K	 65 K* 55 K•
*Actually 09 85° elevation angle
P kt ^
Since the antenna-noise temperature ('fable 1) is only 70 K, or less, for elevation
angles of 5% and greater, it is worthwhile for RF equipment designers to strive for
improving receiving system noise temperature. For example, modern low-noise
bipolar transistor amplifiers have noise figures as low as 2.0 dB at 1.6 GHz. As-
suming T A = 70 K and 1.0 dB transmission loss between the antenna output termi-
nals and the preamplifier input terminals, gives a receiving system noise tempera-
ture of only 300 K — a significant improvement of 5 dB in received carrier-to-noise
spectral density ratio compared to 950 K (noise figure = 5.9 dB).
The component parts of Blakes' 161 theoretical value of antenna-noise tem-
perature T A = 70 K, for 5° elevation angle at 1.6 GHz, indicate contributions of
9 K for average cosmic noise, 10 K for quiet-sun noise in the antenna's sidelobes,
18 K for tropospheric (atmosphere) noise, leaving a remaining estimated 33 K
average antenna sidelobe noise from the ship's structure. 'Phis is roughl%
equivalent to a ground-based, directive antenna.
A comparison o` theoretical and measured values for T A , in Table 1, for
at-sea data at elevation angles of 5% and above, indicate agreement within
about 5 K.
1 387 K
z 280
JW •	 AT&O
Y SATELLITE
240W
W
IZ
Uj
O 200
•
•
W
cc M
180
«	 x	 HARBOR
cc _	 SIGNALS	 • ONBOARD
2 120 «	 •	 RADARS«	 «W
^'
«
x
W
z
^ s
T
Q STEADY BACKGROUND
WNOISE TEMPERATURE
za
0,
0	 10	 20	 30	 40	 50	 80	 70	 80	 90
ELEVATION ANGLE — LEGREES ABOVE HORIZON
Fig. 4. 1.2 m (4 ft) dish ante na-noise temperature vs. elevation
angle in harbor 1.6 GHz data "American Alliance."
Y
	 SUN
IN MAINLOSE
Z 140
J
W
Y
!!? 120
	
100	
x ONBOARD
	
W# I
i
	
RADARS
i 80
i 80
STEADY BACKGROUND
	40	 NOISE TEMPERATURE
PhWj	 20
	
o .	 }
0	 10	 20	 30	 40	 50	 80	 70	 so	 90
ELEVATION ANGLE — DEGREES ABOVE HORIZON
Fig. 5. 1.2 m (4 ft) dish antenna-noise temperature vs. elevation
angle at sea 1.6 GHz data "American Alliance."
Conclusions. -Extensive antenna-noise temperature measurements at 1.6 GHz
(L-Band) were made with a radiometer, and liquid nitrogen 77 K cold-temperature
reference load, using a 1.2 m-diameter parabolic dish antenna positioned on a
commercial-container cargo ship. Both in-harbor and at-sea antenna-noise tem-
perature measurements were made at 1.6 GHz. Steady background, antenna-noise
temperature measurements, slightly less than 70 K, were obtained at elevation
angles of 5`, and grestar, at 1.6 GHz, being equivalent o a ground-based antenna.
A comparison of theoretical and measured values, for at-sea data, indicate excellent
agreement within about 5 K.
Acknowledgment. - The authors would like to thank Mr. Daniel Brandel, National
Aeronautics and Space Administration, Goddrrd Space Flight Center for his helpful
suggestions.
Also, the authors would like to thank Mr. Harry A. Feigleson, Research and
Development Program Manager, U.S. Maritime Administration; Captain W. F.
Kolbe, Jr., Marine Superintendent, and Captain Hance E. Heather, Master, SS Amer-
ican Alliance, United States Lines, Inc. for their cooperation and support.
REFERENCES
I1) "In-Harbor and At-Sea Electromagnetic Compatibility Survey for Maritime
Satellite L-Band Shipboard Terminal." Prepared for NASA/Goddard Space
Flight Center, Greenbelt, Maryland (USA) under sponsorship of U.S. Depart-
ment of Commerce, Maritime Administration under NASA Contract NAS 5-
24035 by RCA Service Corporation, Springfield, Virginia (USA); August 1974.
1 2 1 R. E. Taylor and J. S. hill, "EMI Survey for Maritime Satellite, L-Band Ship-
board Terminal," 1st Symposium and Technical Exhibition on Electromagnetic
Compatibility, Montreux, IEEE 75CH1012-4 MONT, pp. 381-387; May 20-22,
1975.
31 R. H. Dicke, "The Measurement of 'Thermal Radiation at Microwave Fre-
quencies," The Review of Scientific instruments, Vol. 17, No. 7, pp. 268 - 275;
July 1948.
141 John D. Kraus, "Radio Astronomy." McGraw-Hill Book Company, Chapter 7:
Radio-Telescope Receivers; 1966.
51 L. V. Blake, "Antenna and Receiving-System Noise-Temperature Calculation."
U.S. Naval Research Laboratory (NRL) Report 5668, (USA National Information
Technical Service Report No. N63-80893, Springfield, Virginia 22151), Wash-
ington, D.C. (USA); 19 September 1961.
t


L-band, 1.2 m parabolic antenna-noise temperature measurement

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