Four Naval Research Laboratory
(NRL) researchers have developed and demonstrated a fiber-optic
beamformer for true time-delay steering of a two-dimensional
transmitter array. They report that the beamformer is a cost-effective
method for distributing the microwave signals and for providing
a true time-delay function to antenna sub-arrays.
The research team includes: Drs.
Michael Y. Frankel, Ronald D. Esman, and Paul J. Matthews of
NRL's Optical Sciences Division and 0Mark D. Parent of
NRL's Radar Division.
According to Dr. Frankel,
"Phased-array
antennas are finding increasing applications in modern commercial
and military radar and communication systems. The individual
element control that is possible with array antennas permits
the implementation of such functions as dynamic beam steering
and shaping. The distribution of microwave signals over fiber-optics
is advantageous to metal waveguides in the areas of routing ease;
system size and weight; signal loss and bandwidth; and susceptibility
to electro-magnetic interference. Fiber-optic systems also make
possible signal processing functions such as true time-delay,
which is required for precise beam steering over wide frequency
ranges.
The NRL group has developed a
signal distribution technique that preserves all the advantages
of fiber-optics technology. The speed of light in a material
depends on light color. NRL's approach relies on this property
to control the timing of signals in the system by changing the
color of light. This technique overcomes the limitations typically
associated with optics by providing a system that uses all commercially
available components leveraging off the high-volume production
of the telecommunications industry," says Dr. Frankel. The
NRL approach is compact, affordable, provides for operation stability,
covers a wide signal frequency range, and is based on all commercial
components.
"The NRL team has demonstrated
excellent performance of this approach for controlling one-dimensional
and two-dimensional arrays over the 2 to 18 GigaHertz (GHz) frequency
range. A communications array antenna based on this technology
can directly support OC-192 type signal transmission capable
of 10 Gigabits per second transmission (Gbps) (125,000 simultaneous
voice channels at 64 Kilobits per second (Kbps)). A radar array
antenna can directly support an unprecedented ~ 2 centimeter
(cm) spatial resolution," concludes Dr. Frankel.
The research team reports, "This
technology can be used on any broadband array antenna for both
military and civilian applications." Future plans include
refining this approach to use fiber Bragg gratings (FBG's) instead
of dispersive fibers.
This research is sponsored by
the Office of Naval Research (ONR).
The U.S. Naval Research Laboratory is the Navy's full-spectrum corporate laboratory, conducting a broadly based multidisciplinary program of scientific research and advanced technological development. The Laboratory, with a total complement of nearly 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 85 years and continues to meet the complex technological challenges of today's world. For more information, visit the NRL homepage or join the conversation on Twitter, Facebook, and YouTube.
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