The Aeronomy Laboratory recently installed a 100 x 100 meter array antenna with limited beam steering on Christmas Island as a part of the TOGA (Tropical Ocean and Global Atmosphere) program. The array and the associated beam steering and indicating hardware are described

Balsley, B. B.

Carter, D. A.

Ecklund, W. L.

English

NASA Technical Reports Server

N87-10500 "
379
7.1.1 THE NOAA TOGA ANT_qNA ARRAY
W. L. Ecklund, D. A. Carter and B. B. Balsley
Aer onomy Laboratory
NOAA
Boulder, O0 80303
NOAA's Aeronomy Laboratory has recently installed a 100 by 100 meter array
antenr_ with limited beam steerin E on Christmas Island as part of the TOGA
(Tropical Ocean and Global Atmosphere) prosrsm. In this report, we describe
the array and the associated besm stearin 8 and indicating hardware. The array
consists of center-fed 48-dipole coaxlal-collinear antenna strings. Thirty-two
of these strings are installed parallel to each other at one-half wavelength
spacing to make a 100 by 100 meter array. A second set of 32 antenna strings
are physically superimposed perpendicular to the first set to form the other
polarization. The TOGA antenna strings are aligned north-south and east-west
geographic.
Figure 1 shows the feed network for the TOGA array. Each string of 48
dipoles is indicated at the top of the figure by numbered open circles. The
antenna strings are fed in a repeating pattern of 8 (a spacing of 4 wave-
lengths) by equal lengths of transmission line. Antenna strings 1, 9, 17 and
25 are fed through phase shift module 1 in the field box. Strings 2, 10, 18,
and 26 are fed by module 2, etc. In this way, only 7 phase shift modules
provide 5 usable beam positions (vertical, and 15 or 30 degrees east and west
of the zenith). In the initial TOGA installation, one polarlzation is switched
between vertical and 15 degrees east of zenith. The other polarization is
hard-wired to 15 degrees north of zenith, but a second field box can be
installed later to provide steering in the north-south direction as well. A
coaxial SPDT vacuum relay selects either the east-west or north-south array.
• Each basic phase shift module consists of 2 SPDT vacuum relays mounted in
a block with clamp fixturee to attach 2 fixed lensths of RG-213 coaxial cable.
Seven of these basic modules allow any 2 of 5 beam positions to be selected.
Addition of a second module set in series (in the same field box) provides 4
positions. One set of cables in the seven modules and the fixed cable shown in
Figure 1 are cut for identical phase shifts to form the vertical be-re. The 15-
degree east beam is formed by switching in a second set of cables in modules 1
through 7 that are longer than the vertical set by progressive one-eighth wave-
length increments.
The phase shift modules and the polarization switch are driven via a
multiconductor cable by the bean selector-indicator box located in the
equipment shelter at the edge of the array. Beam positions can be selected by
computer control or by manual control from either the shelter or the field box
located in the center of the array. Beam positions and possible vacuum relay
faults are indicated by logic circuitry located in the field box. The position
of each SPDT vacuum relay is monitored by checkin 8 continuity of the
transmission line center conductor through the 2 or 4 SPDT relays in each
module and the polarization switch to the shorted quarter-wavelength stub shown
in Figure 1. This position information is decoded, indicated in the field box
and equipment shelter, and compared with the selected position. Any
discrepancies (indicating a relay problam) are indicated by fault llghts. The
beam position and fault lights are read and logged by the system computer.
https://ntrs.nasa.gov/search.jsp?R=19870001067 2020-03-23T14:36:57+00:00Z
38O
TOGA ANTENNA SYSTEM
"=v------WEST EAST -'---'-_
I POLARIZATIONSWITCH
I
SHORTED _4 STUB
BEAM I I
SELECTOR- TRANSMITTER-
INDICATOR RECEIVER
Figure i.


The NOAA TOGA antenna array

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