Military electronics systems generally leverage the latest technologies in order to achieve performance or even tactical advantages. Although systems, such as radar and electronicwarfare (EW) platforms, are comprehensive collections of analog, digital, and RF circuits and devices, it is often the technology in a part as small as a transistor that can have an enormous impact on the overall performance of a military electronics system.

For example, earlier this year Microsemi Corp. (www.microsemi.com) released the model TAN500 power transistor for TACAN avionics transmitters. The transistor delivers 500 W output power from 960 to 1215 MHz when driven with 70-W, 10-microsecond pulses. The Class C bipolar transistor is designed for use at +50 VDC. The transistor die, with at least 9-dB power gain and collector efficiency of at least 40 percent, features gold metallization and integral emitter ballast resistors for maximum reliability.

According to Russell Crecraft, general manager, Power Products Group for Microsemi (Bend, OR), “Customers are continually looking for higher-power transistors for TACAN applications. The challenge for the device supplier is to provide such a device that can cover the broad bandwidth and heavy pulsing requirements for TACAN transmitters. Microsemi has met that challenge with the TAN500. The customer can now greatly simplify the design of KW transmitters.”

Likewise, transistor supplier HVVi Semiconductors, Inc. (www.hvvi.com) earlier this year announced a major advance in silicon RF transistor design that will also benefit pulsed military RF electronics systems, such as Mode S and TACAN transmitters. The company’s latest transistors are based on the firm’s novel High Frequency, High Voltage Vertical Field Effect Transistor (HVVFET) technology, using an architecture that promises wider bandwidth, higher voltage, and higher power levels for radar and avionics applications than traditional silicon bipolar and LDMOS device technologies.

The patent-pending technology is the basis for three new transistor products targeted at high power, pulsed RF applications at L-band frequencies, such as IFF, TCAS, TACAN, and Mode-S, transmitters. All three transistors are designed to operate at +48 VDC. Model PVV1011-300 delivers more than 300 W pulsed output power from 1030 to 1090 MHz while providing 15 dB of gain and 48 percent typical efficiency with 50-microsecond pulses at a pulse period of 1 ms. The device is specified to withstand a 20:1 VSWR at all phase angles under full-rated output power.

Models PVV1214-25 and PVV1214- 100 are enhancement-mode RF transistors for L-band pulsed radar applications from 1.2 to 1.4 GHz. Designed for use at +48 VDC, the devices deliver 25 W and 100 W output power, respectively. With 200-microsecond pulses and a pulse duty cycle of 10 percent, model PV1214-25 provides 17.5 dB gain and model PV1214-100 offers 19.5 dB typical gain. Both transistors are capable of withstanding an output load mismatch corresponding to a 20:1 VSWR at rated output power and nominal operating voltage across the entire frequency band of operation. The 25-W driver transistor is supplied in a surface-mount package while the higherpower devices are housed in standard flange-mount packages (Fig. 1).

As Wil Salhuana, president and CEO of HVVi noted: “While currently used silicon RF transistor technologies such as bipolar and LDMOS have served radar and avionics designers well, they have hit a ceiling in terms of performance. By creating the first high-frequency, highvoltage vertical field effect transistor, we have redefined the performance capabilities of the discrete silicon power transistor and opened the door to a vast array of new applications.”

Earlier this month, Freescale Semiconductor (www.freescale.com) announced the first 50-V silicon LDMOS transistors designed for L-band avionics applications. The 50-V capability greatly simplifies integration into aircraft power-supply systems. The new product line includes two transistors designed to work together in an avionics or radar transmitter circuit: the model MRF6V14300H final stage device and the model MRF6V10010N driver device. The MRF6V14300H delivers 330 W pulsed output power from 1200 to 1400 MHz with extremely high efficiency and gain, and excellent thermal characteristics for good long-term reliability. The model MRF6V14300 device achieves 17-dB gain with 60-percent drain efficiency when amplifying a 300-microsecond pulse at 12-percent duty cycle to its rated 330-W output power. The driver device, model MRF6V10010N, provides 8 W peak output power at 1400 MHz with a 300-microsecond, 12-percent-duty-cycle signal, with 22-dB gain and 60-percent drain efficiency. The new devices are fabricated with Freescale’s six-generation very-high-voltage (VHV6) 50-V LDMOS technology. Both devices incorporate electrostaticdischarge (ESD) protection to guard against improper handling. The highpower model MRF6V14300H is housed in a RoHS-compliant air-cavity ceramic package while the MRF6V10010N driver is supplied in an over-molded plastic package.

In terms of broadband gain, few devices can match the TGA4830 chip amplifier from TriQuint Semiconductor (www.triquint.com). Measuring just 1.79 x 1.00 x 0.11 mm, the amplifier features DC-coupled input and output ports and total coverage of DC to 45 GHz. It provides 13 dB gain at 20 GHz and an automatic gain control (AGC) range of better than 20 dB. Based on 0.15-micron pseudomorphic-high-electron-mobilitytransistor (PHEMT) technology, the amplifier chip is well suited for EW systems as well as test and measurement applications. It delivers +11.5 dBm output power at 1-dB compression with input and output return los of 15 dB. The broadband amplifier draws 50 mA from a +5-VDC supply.

TriQuint recently announced a large order of gallium nitride (GaN) wafers from semiconductor wafer supplier IQE plc (www.iqep.com). The GaN wafers are intended to to support ramping up new commercial and military products at TriQuint. According to TriQuint Research and Development manager, Anthony Balistreri, “IQE’s established track record in providing TriQuint with reliable, high-quality products was a key factor in selecting them to produce and deliver a range of advanced GaN epitaxial materials. We’ve developed a close working relationship with IQE throughout the development phase of our GaN program.” TriQuint’s recent order for GaN epitaxial high-electronmobility- transistor (HEMT) wafers from IQE’s New Jersey facility will be used in ongoing military and commercial R&D efforts while supporting TriQuint’s new products in 2008.

For generating system-level signals, Micro Lambda Wireless (www.microlambdawireless.com) offers its MLOB and MLOS series of wideband YIG-tuned oscillators with integrated militarygrade digital drivers for test and system applications from 700 MHz to 20 GHz. These low-phase-noise oscillators can be supplied with 12-b digital driver circuitry to simplify integration into military electronic systems. The oscillators and drivers are rated for operating temperatures from -40 to +85°C.

For timing applications, the Firefly from Jackson Labs (www.jackson-labs.com) represents true miniaturization in a Global Positioning System Disciplined Oscillator (GPSDO). It measures a mere 1.25 cubic inches even though it is based on oven-controlled-crystaloscillator (OCXO) technology. The GPSDO delivers Stratum-1 long-term frequency-stability performance of better than 10 parts per trillion, or 1 x 10 -11 averaged over a 24-hour time period when locked to a GPS signal. It provides an OCXO-driven 1 pulse per second (PPS) output signal that is phasesynchronized to better than 100-ns root mean square (RMS) to Universal Time Code (UTC) and a synchronized lownoise 10-MHz sinewave output signal at +12-dBm level.

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