TriQuint Uses AWR Software for Difficult GaN Discrete Power Amplifier Design
TriQuint is an industry leader in advanced, high-performance RF solutions for mobile devices, network infrastructure and defense and aerospace markets. Besides smartphones and tablets, TriQuint products are found in cellular base stations, satellite and optical networks, defense and aerospace solutions, and countless other high-performance communications and radar systems.
For this hybrid discrete packaged amplifier, the challenge was to provide a highly broadband solution that was inexpensive and had a small footprint, which made implementing multiple stages a difficult task given size constraints. The designer chose to use a bridged-T topology because it allowed him to match the input of a single transistor to 50Ω while minimizing die area. The packaged amplifier needed to demonstrate 5W of output power and 40-50 percent PAE across the 1 – 2.7 GHz range. The transistor was sized such that the 50Ω termination on the output matches well to its target load line, so that the output can be left unmatched. A transistor with 1.24mm periphery was chosen, and, additionally, a transistor with 2.48mm periphery was also designed, which provides a favorable load line and similar die area, but was not used in this design.
“We actually have been able to reuse the design for several MMIC’s of different power levels with the bridge T input match. In fact the product using the 2.48mm is done now, and shows excellent results.”
The linear simulations of this design were done with Microwave office and the board-level layout and simulation with AXIEM. The linear simulation was matched to imported S-parameter blocks using Microwave Office and AXIEM was used for the board-level simulations of the input and output matches. The final MMIC used for the hybrid discrete PA solution.
The designer was more easily able to design the matching networks thanks to the built-in tools and measurements within the AWR Design Environment. The software’s ability to easily construct, compare, and optimize various topologies quickly was another advantage. The highly integrated AXIEM tool was especially helpful with the extraction flow for the board design.
The final device was tested on a board made of Rogers 4350B. The 50Ω-matched input held up well enough to achieve 10 dB return loss from 40 MHz to 2.7 GHz and 7 dB return loss down to 30 MHz. The device achieved a gain of 12 dB at lower frequencies, and 17 dB at higher frequencies.
At 32 V and under pulsed conditions, the amplifier achieved a typical output power of 5 W (or 4 W/mm power density) and 45 percent power added efficiency over 1 to 2.7 GHz. The pulsed operation was chosen over CW, because the evaluation board limited the total power dissipation. Additionally, the data were measured from 1 to 2.7 GHz, because the designer was not able to set up a pulsed test station below 1 GHz.
Why AWR Design Environment?
The designer chose AWR software because he has been an experienced user since he was an engineering student. When compared to several other RF design tools he has used, he prefers AWR due to its ease of use. Of benefit to him in his design effort was the unified database with tightly integrated schematic and layout, which makes it much easier for him to understand projects and what is actually being designed, modeled, and laid out.
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