IEEE Aerospace and Electronic Systems Magazine - July 2020 - 49

Wang et al.

ARGENTINA
Argentina launched the first SAOCOM-1 satellite
equipped with L-band active phased array antennas in
November 2008 [43]. The expected lifespan of the satellite was five years. The adopted microstrip array antenna
with a bandwidth of 50 MHz had the ability to operate in
the stripmap and scanning modes. The SAOCOM project
was a cooperative project between Argentina and Italy,
mainly for the collection of natural disaster data to make
timely disaster predictions. It was also used in the field of
epidemiology.

LARGE APERTURE AND DEPLOYABLE STRUCTURE

CHINA
In China, research on the space active phased array antennas started later, but rapid progress has been made. The
spaceborne S-band phased array antennas carried on the
BeiDou satellite series had provided on-orbit service,
which was equipped with spiral antenna elements [44]. In
2020, China plans to build a global satellite navigation
system, which will be made up of five geostationary orbit
satellites and 30 nongeostationary orbit satellites networks. In recent years, China has carried out the development of the subarray and prototype of the space Ka-band
active phased array antennas, and conducted electromagnetic performance and thermal tests. The project will provide accurate positioning and navigation for missiles,
precision guided weapons, and other military functions.

STRUCTURAL FEATURES OF SPACE ACTIVE PHASED
ARRAY ANTENNA
In contrast to the single aperture reflector antennas, active
phased array antennas are more flexible in design, as the
elements can be arranged in different ways (e.g., linear
arrays, planar arrays, and conformal arrays). Thus, they
can perform many functions, including high gains, narrow
beams, space scanning, SDMA, and autonomous control.
They can be used for multitarget tracking; antimissile
warning; shipborne, airborne, and spaceborne radar systems; electronic countermeasure systems; communications; air traffic control; medical treatment; mineral
resources exploration; antiterrorism; and investigation of
drug smuggling [45]. The space deployable active phased
array antennas have multiple work modes such as stripmap, scanning, spotlight, interference, large viewing
angle, multibeam, and GMTI. These allow flexible beam
scanning to meet the requirements of antenna steering. In
addition, active phased array antennas can achieve high
gain, low-amplitude sidelobe, high resolution, and high
reliability. Due to all these properties, the space deployable active phased array antenna is a form of antenna
JULY 2020

suitable for satellites, with the fast development and the
large application potential. Due to the volume limitation
of the launch platform and loading platform, the spaceborne active phased array antenna has a complicated
deployment mechanism. The longer the operation distance
of satellite antennas, the larger the aperture must be. The
large physical aperture and complex deployment mechanism have a great influence on the design of the antenna
system. Therefore, the lightweight design of the satellite
system is mainly focused on the lightweight structure of
active phased array antennas.

In order to achieve scanning and covering over long
distances and on large scales, the space deployable active
phased array antenna should provide large power aperture product. Thus, the antenna is required to have a large
physical aperture in case there is limited power available
to the satellite platform. In light of the orbit deployment
and performance index, the antenna aperture can be tens
to hundreds of square meters. For instance, the SAR
antenna aperture on the United States ocean satellite
SEASAT-1 [46] is 10:74 m Â 2:16 m. For the LIGHTSAR satellite antenna codeveloped by NASA and JPL
[47], the aperture is 10:8 m Â 2:9 m; The aperture of the
Canadian C-band RADARSAT-2 satellite antenna [48] is
15 m Â 1:37 m. The Japanese L-band ALOS-2 satellite
antenna codeveloped by JAXA and the Mitsubishi Company has an aperture of 9:9 m Â 2:9 m [49]. The aperture
of the L-band phased array lens antenna developed by the
American Northrop Grumman Company is 60 m Â 25 m
[50]. Finally, the engineering prototype of the LEO
deployable active phased array antenna developed by
the United States Ball Company, has an aperture of
60 m Â 25 m [51].
Due to the restricted size of the launch rocket fairing,
the space active phased array has the characteristic of having a deployable structure. The antenna array is usually
divided into several rigid array panels, which are folded
around the satellite before its operation. After the satellite
enters the predetermined orbit, the antenna array is
extended out of the satellite cabin via the deployment
mechanism. For example, Japan's JERS-1 and IGS-1B
satellites, ESA's ERS-2 satellite, and India's RISAT-1 all
use a deployable active phased array antenna.

LIGHTWEIGHT STRUCTURE
A space active phased array antenna with a large aperture
and complex deployment mechanism requires a lightweight structure in order to transmit effectively while
reducing the cost of transmission. Currently, there are two
main types of spaceborne deployable phased array

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