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tech.com Safer Radar... Continued from page 1
coming enemy aircraft or weapon. Mechanical-scan radars are also
susceptible to damage. If the servo motors that cause the antenna to ro- tate, or stabilize it, fail or the anten- na is damaged, the radar is rendered inoperable. As a result, later genera- tions of radar moved away from me- chanical scanning toward fixed, phased array radar systems in which all movement is eliminated.
Fixed Phased Arrays Phased arrays are composed of
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evenly spaced antenna elements, each of which emits a signal that incorpo- rates a phase shift to produce a phase gradient across the array. The ampli- tudes of the signals radiated by the in- dividual antennas and the construc- tive and destructive interference caused by objects determine the effec- tive radiation pattern of the array. By digitally varying the signal
phases and amplitude of the ele- ments in an array — a process known as digital beamforming — the main beam can be “steered” to determine the direction of the signal source, even though the antenna does not physically move. Because of the rapidity at which
the beam can be steered, phased ar- ray radars can perform search, track and missile guidance functions si- multaneously with a capability of over a hundred targets. Phased array systems vary in
size and complexity. For several dec - ades, massive planar arrays have been used aboard Navy warships and are at the heart of the ship-borne Aegis com- bat system and the Patriot Missile Systems. Smaller phased array anten- nae can be built to conform to specific shapes, like missiles, infantry support vehicles, ships, and aircraft. Although there are several
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ways to accomplish electronic beam steering, one such technique involves varying the phasing between elements in a fixed, multi-element array. This is typically accomplished with power di- viders that emit signals of varying phase and amplitude to the antennae. As an example of the hardware
improvements required in next gen- eration systems, power dividers serve as a prime example.
Hardware Improvements Power dividers are passive com-
ponents that divide an input signal in- to two or more identical output signals. For phased array systems that require a range of signal amplitudes, the input signal is often altered using attenua- tors to vary the signals prior to output to deliver the desired signal level. The traditional way of accom-
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plishing this is to utilize a standard multi-channel power divider with at- tenuators at each of the output ports. Attenuators, however, increase the overall size and weight of the unit while drawing additional precious watts of power. The size and weight of the power divider with attenuators made it difficult to deploy on jet planes that could benefit from more sophisticated radar. Renaissance Electronics & Com -
munications, a manufacturer of RF and microwave sub-systems and com- ponents, has designed a power divider that splits power from 6.7 to 18.4dB across the output ports that does not require attenuators. Operating be- tween 1100 and 1500MHz, this 8-way
divider is optimized for space con- strained applications at only 8 x 5 x 0.5 in. (203 x 127 x 12.7 mm). The divider can handle 350W Peak and 35W CW. The output signal is staggered
in fixed amplitudes that begin at 18.4dB at ports 1 and 8; 12.4dB at 2 and 7; 8.6dB at 3 and 6 and 6.7dB at ports 4 and 5. The 8 output ports are each connected to a fixed antenna. The Renaissance power divider
December, 2015
Power divider that splits power from 6.7 to 18.4dB across the output ports that does not require attenuators.
provides 35 to 40 percent more reso- lution and extends the coverage from one mile to several miles. According to a spokesperson at
Renaissance Electronics, the next generation of phased array systems along with advanced signal process- ing techniques could have significant benefits for many branches of the military. For example, higher resolution
radar could be used to initiate a com- puter takeover in the event of a mis- sile attack on a jet plane. Using so- phisticated evaluation of the mis- sile’s speed and trajectory millisec- ond to millisecond, computer-con- trolled micro adjustments could be used to evade the threat. In an intense battlefield with
numerous vehicles and personnel, advanced radar could be used not just to track high-speed targets, but also slow-moving targets like ground troops. Armed with this information, the command center could have com- plete, real-time visibility of all mov- ing components of a battlefield. Contact: Renaissance Electron-
ics & Communications, 12 Lancaster County Road, Harvard, MA 01451 % 978-772-7774 Web:
www.rec-usa.com r
PCB Sales... Continued from page 1
positive sales growth, the result of strong order growth in most months of 2015. Orders contracted in Sep- tember bringing the book-to-bill ratio down from a 5-year high in August to a more moderate level,” said Sharon Starr, IPC’s director of market re- search. “The book-to-bill ratio re- mains positive for the 12th consecu- tive month,” she added, “which is a strong indicator of positive sales growth in the fourth quarter of this year and into next year.” IPC’s monthly PCB industry
statistics are based on data provided by a representative sample of both rigid PCB and flexible circuit manu- facturers selling in the USA and Canada. IPC publishes the PCB book-to-bill ratio at the end of each month. Statistics for the current month are available in the last week of the following month. Info:
www.ipc.org r
Please register to attend
Attend our presentation “PCBs with Embedded RFID Technology” and visit our booth #209 at PCB West, Santa Clara, CA Sept. 15th
-17th
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