Gallium nitride (GaN) semiconductor material, considered promising but still developmental just a few years ago, is now a favored RF power amplifier technology for many commercial and defense systems. The substrate's high power density and efficiency coupled with its capability to cover broad bandwidths at high frequencies makes it the de factor choice for power amplifiers employed in new electronic warfare (EW), electronic countermeasures (ECM), radar, and communication systems. The performance of GaN is being fully utilized in two new amplifiers from BC Systems, which combine the benefits of GaN with proprietary DC-to-DC converters to deliver as much as 100 W of RF power in miniature modules.
The DA Module (Fig. 1) measures only 4.5 x 3 x 0.6 in., weighs less than 1 lb., and delivers at least 20 W output power from 25 to 1000 MHz. Its compact size makes it well suited for manpack and man-portable communications systems and EW systems. The model RF40015 amplifier (Fig. 2) delivers 100 W or more output power from 20 to 305 MHz, measures 5.5 x 4.5 x 1.6 in., and weighs less than 2 lb. Both amplifiers deliver greater than 30 percent efficiency in Class AB mode with blanking speed of less than 5 s, which ensures very good noise performance and low standby power consumption. The fast blanking capability also results in less unwanted generation of spurious and residual signal power, to maintain low probability of detection from hostile detection systems.
The amplifiers can deliver their rated power continuously into a load VSWR of 2.5:1, are unconditionally stable over all combinations of load impedance and phase conditions, and incorporate circuits that provide protection from over-current and over-voltage conditions. Their operating temperature range is -20 to +85C and storage temperature range is -45 to +95C. The amplifiers benefit from integrated DC-to-DC converters for which a patent is pending. The converters for the DA module and model RF40015 amplifier operate with supply voltages of +22 to +34 VDC and +26 to +30 VDC, respectively. The converters are fabricated by BC Systems using discrete components rather than an off-the-shelf "brick" power supply, which gives the company's designers much greater flexibility in matching them to each amplifier, reduces delivery time, and results in more predictable performance.
Other GaN-based amplifiers in the family include the BCPA-1600-2800-15 that delivers at least 15 W CW from 1.6 to 2.8 GHz, and the BCPA-3400- 3600-5 that produces at least 5 W from 3.4 to 3.6 GHz. Both have the same self-protection and other features as the RF40015 and DA module, measure 3 x 2 x 0.6 in., weigh about 8 oz., and operate from 22 to 34 VDC supply voltages. The company's amplifier line ranges in output power from 2-W to more than 100 W and 20 MHz to 6 GHz.
One of its newer compact GaN power amplifiers well suited for a variety of military electronics applications is model RF40003, which delivers 100 W minimum output power from 20 to 305 MHz. It also delivers the better than 5-s blanking speed of the DA Module and the RF40015 amplifier, with at least 30-percent efficiency. It weighs less than 2 lbs. and measures only 5.5 x 4.5 x 1.6 in. The amplifier is designed for use with input voltages from +26 to +30 VDC and has a builtin DC-to-DC converter for that purpose.
The amplifier division of BC Systems is unique in that it is part of a company that has been designing and manufacturing power supplies exclusively for military systems (and more specifically to support RF power amplifiers) for more than 25 years. The product line ranges from tiny, space-qualified supplies such as the BC-26, which delivers 30 W from a 28 VDC source, to the BC-11K model used in ground-based radar systems that delivers 12 kW average and 30 kW peak power from a 115-VAC source.
The BC-751 is one of the company's latest AC-to-DC converters designed to provide power for solid-state RF amplifiers and was designed for airborne Identification Friend or Foe (IFF) applications. The converter provides more than 800 W with eight outputs, and accepts a three-phase 155 VAC, 400 Hz input with a power factor of at least 0.88 and maximum inrush current of less than 13 A. Its overall efficiency is 77 percent. The BC-751 has protection for over-current, over-voltage, and over-temperature conditions, operates over a temperature range of -40 to +85C (-55 to +85C nonoperating storage temperatures), and uses forced-air cooling. It meets CE101 and CE102 conducted emissions requirements per MIL-STD-461 and shock and vibration to IAW MIL-STD- 810D. The unit measures 8.51 x 8.43 x 3.69 in. and weighs less than 12 lb.
Standard BC Systems power amplifier models can be modified to meet specific sets of physical, electrical, and RF performance parameters as well as military standards for shock and vibration. They can also be specified with an integrated low-power sampling port for RF output monitoring as well as a directional coupler. BC Systems, 200 Belle Mead Rd. Setauket, NY; (631) 751-9370; e-mail: firstname.lastname@example.org, Internet: www.bcpowersys.com.