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Rugged
Military Amps Match Power to Power Supply
By BC Systems
RF amplifiers for defense applications operate
in a different world than their commercial and consumer
counterparts. Ruggedness is assumed, along with reliability
under a wide range of operating conditions. BC Systems has
introduced a broad range of RF power amplifier modules designed
for virtually every military application, from jamming to
electronic countermeasures, radar and avionics. In addition
to excellent RF performance, they have another advantage
that sets them apart from amplifiers manufactured by companies
with only RF and microwave expertise. That is, the company
has been a military power supply manufacturer for more than
20 years, so the RF and microwave power amplifiers are designed
side-by-side with the company’s power supplies to
ensure a seamless match of power amplifier to power source.
Spectrally, DC power supplies and high-power RF and microwave
amplifiers are about as far removed as components can be.
However, from a performance perspective, the relationship
between the amplifier and its source of DC power could not
be more closely aligned. Practically speaking, the performance
of the amplifier is only as good as its power source allows
it to be. In addition, both components must function together
without degrading the other’s performance. In fact,
the next generation of jamming systems specifically demand
the highest levels of noise mitigation and reduction.
One example of performance degradation, spectral
regrowth, can result from interaction of the amplifier’s
input signal with component nonlinearities, as well as noise
or voltage ripple in the power supply. If the RF amplifier
has insufficient power supply rejection, supply noise can
degrade system performance as well. The noise can come from
coupling of RF and analog signals to the supply through
bond wires and other parasitics, thermal noise from devices,
or digital switching. An additional source of supply noise
is voltage ripple from switching regulators. Power supplies,
in turn, must be designed to handle the wide range of power
requirements an RF system can demand during varying operating
conditions. These and an array of other potential problems
can best be addressed when both the amplifier and power
supply are designed to work together.
The company’s Advanced RF Amplifier Division manufactures
a wide array of amplifier modules, primarily for military
applications, such as communications, electronic warfare,
electronic countermeasures, and radar, including amplifiers
that form the basis of jamming systems designed to counter
radio controlled improvised explosive devices (IEDs). The
amplifier modules are housed in rugged aluminum enclosures
and are fully shielded.
Technical expertise in both RF power and power
supply technologies allows the company to provide a complete
RF amplification solution, including the amplifier, power
supply, and filtering. This typically allows subsystems
to be smaller and lighter than those created by cobbling
together the various components from several manufacturers,
and more efficient as well. The products are more often
than not required to meet stringent Electromagnetic Compatibility
(EMC) standards.
One of the latest examples of the company’s
amplifiers is the BCPA-500-2500-25J, which delivers up to
25 W in Class AB operation from 500 MHz to 2.5 GHz. It employs
gallium nitride (GaN) power transistors, providing ultra
broadband amplification with appreciable gain, efficiency
and linearity. The BCPA-500-2500-25J is designed for jamming
systems (although it is suitable for many other applications),
and operates with input signals ranging from CW to digital
modulation and Gaussian noise. It measures only 4.0 x 6.0
x 1.1 in. and weighs less than 2.5 lb.
For applications in broadband military radios,
BC Systems has a line of amplifiers that covers 1 MHz to
6 GHz, depending on the model. A good example is the BCPA-20-500-100C
(Figure 1), which delivers 100 W in Class
AB using LDMOS devices, and covers 20 to 500 MHz. The amplifier
is extremely small, measuring only 3.75 x 3.4 x 2.0 in.
and weighing less than 1.5 lb, which makes it well suited
for airborne applications. It employs OSP blind-mate input
and output RF connectors that allow multiple amplifiers
to be combined without the complexity, losses, and discontinuities
encountered when using coaxial cables. Gain at P1dB compression
is 50 dB, second-harmonic rejection is -12 dBc, and spurious
rejection is at least -60 dBc. Both the BCPA-500-2500-25J
and BCPA-20-500-100C operate from 24 to 28 VDC over a temperature
range of -40o C to +85o C (baseplate temperature).
For satellite communications, as well as UHF line-of-sight
and many other applications within the 225 to 500 MHz range,
the BCPA-225-450-100C (Figure 2) offers
100 W output with harmonic rejection of -50 dBc, spurious
rejection of -60 dBc, and gain of 50 dB. It offers fast
transmit enable time of less than 10 µs, can accept
a wide range of input signals, and allows output power to
be selected in 10 steps. It also includes internal transmit/receive
and bypass switching and protection from high VSWR, over-temperature,
out-of-band, and excessive RF input drive. It will operate
over a temperature range of -40o to +65o C. The compact
unit measures 6.0 x 8.5 x 2.0 in. and weighs less than 8
lb.
In addition to its line of amplifier modules,
the company also offers instrumentation laboratory amplifiers
designed for use on the bench or in a 19-in. rack (Figure
3). They are typically employed in EMC testing
and other compliance measurement applications in all stages
of product development and testing. There are three models
in the series, covering 20 MHz to 1 GHz, 1 GHz to 2 GHz,
and 2 to 3 GHz capable of delivering power levels of 100,
250 and 500 W. They can be operated via local or remote
control via RS-232, IEEE-488, or Ethernet. Internal protection
is provided for high VSWR, thermal overload, and excessive
RF input. They accept CW, AM, FM, or PM modulation, have
an ALC range of 40 dB, and are forced-air cooled. They have
a self-contained power supply (90 to 130 VAC or 180 to 270
VAC), and provide front panel status monitoring.
Typical examples of power supplies designed for the amplifiers
include the BC-330 nine-output airborne supply and the BC-750,
which delivers 800 W, has an active PFC three-phase front
end, and is used to power IFF transmitters aboard anti-submarine
(ASW) aircraft. The BC-330 can power an IFF system transmitter
and processor, weighs only 3.2 lb., and measures 9.7 x 6.8
x 1.25 in. The BC-750 meets MIL-STD-461, CE101, and has
10 outputs for 800 W total output (4-kW peak) with 50 ms
holdup time. It weighs 12 lb. More information on the company’s
RF power amplifiers and power solutions can be found at
our website.
BC Systems
Advanced RF Amplifier Division
www.bcpowersys.com
TXTLINX.COM 136
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