S-波段:提高集成度,降低成本

2012-03-15

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Title: Advances in S-Band Radar Technology:

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Reducing overall system cost through higher levels of integration

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Author: Brian D. Battaglia, Jeff Burger and John Titizian

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Introduction:

The S-band has long been an application space
servicing both commercial and military radars. Many of the
radar systems required very high peak power levels with
low to medium pulse widths that were best served by silicon
bipolar technology. Silicon Bipolar Junction Transistor
(BJT) technology has demonstrated very high power
density under pulsed conditions and established ease of use.
A true measure of power density must include a very dense
die delivering a very high power level in a small package
footprint combined with a small matching circuit wrapped
around the device. The RF power devices were biased in
Class C mode of operation to maximize efficiency at
maximum power with little regard for linearity which
wasn’t a critical factor. The small matching circuits and
simple bias circuitry make the BJT devices easy to
implement into complex systems [1]. The growing S-band
market grew to demand wider bandwidths and higher power
levels which were both well served with silicon BJT
technology.
In the last few years the trend in radar systems
requires longer pulse widths and some measure of linearity.
A new technology was required to satisfy these advanced
requirements. Although most MOSFET (Metal Oxide
Semiconductor Field Effect Transistor) technologies would
provide the functionality being sought, the simplest solution
is a LDMOS (Laterally Diffused MOSFET) process which
is silicon-based and therefore the most cost effective in a
price sensitive market. Silicon LDMOS technology has
many advantages including higher gain, better ruggedness
[2], and is inherently more linear while running in Class AB
mode of operation.
Even more recently, the market has demanded not
just higher power or wider bandwidth devices, but products
that reduce the design time of the complex radar systems.
Due to fewer resources and more focus on system level
design features, the RF portion of the system is being
designed at the semiconductor vendor more and more often.
Integrating several power transistors in parallel and
matching the module to 50 ohms creates pallets that
customers can drop-in to their systems. Combining several
pallets together for any power level is straight forward and
reduces the design time. Higher levels of integration have
been provided by combining more than one stage cascaded
together to provide a high gain pallet that offers a complete
solution and eases the work load on the busy radar system
design engineer.
Leveraging their long history in the S-band and RF
expertise, the designers at Integra have developed another
product that offers a complete 50 ohm RF power solution in
a single package. Miniaturized Power Amplifiers utilizing
LDMOS (MPALs) are matched to 50 ohms at the package
leads and only need a bias circuit to complete the solution.

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Download Full Document:

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www.integratech.com/technicalpapers/SBANDwp5NOV09.pdf

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