GaN Devices Provide Broadband Power

May 27, 2015
Available in chip and packaged formats, these high-power GaN amplifiers are suitable for CW and pulsed applications through 14.5 GHz.
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Gallium-nitride (GaN) solid-state devices continue to gain in power at increasing frequencies, supporting a growing number of applications for radar, test, and communications systems for both continuous-wave (CW) and pulsed signals. The latest line of GaN devices from Cree provides generous output power levels at frequencies through 14.5 GHz, ideal for use in radars and satellite-communications (satcom) systems that require efficient signal amplification. Designers have numerous options in terms of specifying chip or packaged devices.

1. Supplied in a metal/ceramic flange package, model CMPA1D1E025F is an impedance-matched GaN-on-SiC MMIC amplifier for use from 13.75 to 14.50 GHz.

The lowest-frequency device in the product line is an impedance-unmatched GaN transistor, model CGHV40050, intended for CW applications from DC to 4 GHz. The GaN high electron mobility transistor (HEMT) is designed for +50-VDC supplies and can provide as much as 50 W output power across the frequency range. It can be supplied in one of two package styles: a two-lead flange package or a pill package. Examples of the performance possible with this transistor based on a reference design for 800 MHz to 2.5 GHz include 17.6-dB gain at 800 MHz with 65 W saturated output power and 63% drain efficiency (PAE). The gain remains high at 1.4 GHz, at 17.7 dB, with 63 W saturated output power and 60% PAE. At 2 GHz the gain drops somewhat, to 14.8 dB, although the saturated output power is still 60 W and the PAE is 52%.

For those who prefer an impedance-matched device, model CMPA1D1E025F is a Ku-band GaN monolithic-microwave-integrated-circuit (MMIC) amplifier on silicon-carbide (SiC) substrate that delivers 25 W modulated output power from 13.75 to 14.50 GHz (Fig. 1). The frequency range is well suited for use in satellite-communications (satcom) uplink equipment. The output power was measured with orthogonal quadrature phase-shift-keying (OQPSK) modulation and a +40-VDC supply.

This MMIC amplifier is supplied in a 10-lead 25 × 9.9 mm metal/ceramic flanged package. It is capable of small-signal gain of 26 dB at 13.75 GHz, 27 dB at 14.25 GHz, and 26 dB at 14.50 GHz. The linear output power is 19 W at 13.75 GHz, 20 W at 14.25 GHz, and 18 W at 14.50 GHz, while the PAE is 18% at 13.75 GHz, 17% at 14.25 GHz, and 16% at 14.50 GHz.

2. Model CMPA1D1E030D is a GaN MMIC amplifier chip on a SiC substrate capable of 30 W output power from 13.5 to 14.5 GHz.

Model CMPA1D1E030D is a GaN MMIC amplifier chip on a SiC substrate (Fig. 2). It can provide 30 W output power from 13.5 to 14.5 GHz when running from a +40-VDC supply. The amplifier, which is well suited for CW amplification in satcom uplinks, achieves small-signal gain of 27 dB at 13.5 GHz and 25 dB at 14.5 GHz, with saturated output power of 33 W at 13.5 GHz and 30 W at 14.5 GHz. It boasts PAE of 24% at 13.5 GHz and 22% a 14.5 GHz when measured with +26-dBm input power.

For more broadband pulsed applications at lower frequencies, the model CMPA601CO25D GaN MMIC chip on SiC substrate is capable of 30 W saturated output power from 6 to 12 GHz. Suitable for jamming amplifiers, radar amplifiers, and test equipment amplifiers, it operates with small-signal gain of 40 dB at 6 GHz and 36 dB at 12 GHz.

When evaluated with a 10-μs pulse at 0.1% duty cycle and powered with +19-dBm input power, the MMIC amplifier chip delivers +48-dBm output power at 6 GHz and +47.3-dBm output power at 12 GHz. With the same +19-dBm input signal, the PAE is 33% at 6 GHz and 32% at 12 GHz. The MMIC amplifier is designed for use at +28 VDC. It measures 0.172 × 0.239 × 0.004 in. in chip form.

Essentially the same amplifier, model CMPA601C025F is available in a 10-lead ceramic package for use from 6 to 12 GHz and +28 VDC. When measured with CW signals, it provides small-signal gain of 35 dB at 6 GHz and 31 dB at 12 GHz. When fed with a +22-dBm input signal, the output power is +42 dBm at 6 GHz and +34 dBm at 12 GHz, with PAE of 27% at 6 GHz and 25% at 12 GHz. The packaged amplifier can deliver as much as 35 W typical saturated output power.

These amplifiers and devices represent the latest GaN devices from Cree but only a sampling of what the firm has accomplished with this technology, with and without SiC substrates for enhanced thermal management. GaN is a solid-state technology that is gaining ground in many higher-power pulsed and CW higher-frequency applications, and these devices provide a glimpse of the performance capabilities of this technology.

Cree, Inc., 4600 Silicon Dr., Durham, NC 27703; (919) 313-5300, FAX: (919) 869-2733

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About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

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