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
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