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Title: Development of high-efficiency power amplifiers for 704 MHz, Phase II

  1. Green Mountain Radio Research Company, Boone, IA (United States)
Publication Date:
Research Org.:
Green Mountain Radio Research Company, Boone, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Type / Phase:
Resource Type:
Technical Report
Country of Publication:
United States
43 PARTICLE ACCELERATORS; Particle accelerator; radio frequency; power amplifier; high efficiency; UHF

Citation Formats

Raab, Frederick H. Development of high-efficiency power amplifiers for 704 MHz, Phase II. United States: N. p., 2015. Web.
Raab, Frederick H. Development of high-efficiency power amplifiers for 704 MHz, Phase II. United States.
Raab, Frederick H. Sat . "Development of high-efficiency power amplifiers for 704 MHz, Phase II". United States. doi:.
title = {Development of high-efficiency power amplifiers for 704 MHz, Phase II},
author = {Raab, Frederick H.},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat Nov 14 00:00:00 EST 2015},
month = {Sat Nov 14 00:00:00 EST 2015}

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  • The Fermi Lab PIP II (formerly Project X) accelerator will require the generation of over a megawatt of radio-frequency (RF) power at 325 and 650 MHz. This Phase-II SBIR grant developed techniques to generate this RF power efficienly. The basis of this approach is a system comprising high-efficiency RF power amplifiers, high-efficiency class-S modulators to maintain efficiency at all power levels, and low-loss power combiners. A digital signal processor adjusts signal parameters to obtain the maximum efficiency while producing a signal of the desired amplitude and phase. Components of 4-kW prototypes were designed, assembled, and tested. The 500-W modules producemore » signals at 325 MHz with an overall efficiency of 83 percent and signals at 650 MHz with an overall efficiency of 79 percent. This efficiency is nearly double that available from conventional techniques, which makes it possible to cut the power consumption nearly in half. The system is designed to be scalable to the multi-kilowatt level and can be adapted to other DoE applications.« less
  • This Phase-I SBIR grant investigated techniques for high-efficiency power amplification for DoE particle accelerators such as Project X that operate at 325 and 650 MHz. The recommended system achieves high efficiency, high reliability, and hot-swap capability by integrating class-F power amplifiers, class-S modulators, power combiners, and a digital signal processor. Experimental evaluations demonstrate the production of 120 W per transistor with overall efficiencies from 86 percent at 325 MHz and 80 percent at 650 MHz.
  • GaN-based microwave power amplifiers have been identified as critical components in Sandia's next generation micro-Synthetic-Aperture-Radar (SAR) operating at X-band and Ku-band (10-18 GHz). To miniaturize SAR, GaN-based amplifiers are necessary to replace bulky traveling wave tubes. Specifically, for micro-SAR development, highly reliable GaN high electron mobility transistors (HEMTs), which have delivered a factor of 10 times improvement in power performance compared to GaAs, need to be developed. Despite the great promise of GaN HEMTs, problems associated with nitride materials growth currently limit gain, linearity, power-added-efficiency, reproducibility, and reliability. These material quality issues are primarily due to heteroepitaxial growth of GaNmore » on lattice mismatched substrates. Because SiC provides the best lattice match and thermal conductivity, SiC is currently the substrate of choice for GaN-based microwave amplifiers. Obviously for GaN-based HEMTs to fully realize their tremendous promise, several challenges related to GaN heteroepitaxy on SiC must be solved. For this LDRD, we conducted a concerted effort to resolve materials issues through in-depth research on GaN/AlGaN growth on SiC. Repeatable growth processes were developed which enabled basic studies of these device layers as well as full fabrication of microwave amplifiers. Detailed studies of the GaN and AlGaN growth of SiC were conducted and techniques to measure the structural and electrical properties of the layers were developed. Problems that limit device performance were investigated, including electron traps, dislocations, the quality of semi-insulating GaN, the GaN/AlGaN interface roughness, and surface pinning of the AlGaN gate. Surface charge was reduced by developing silicon nitride passivation. Constant feedback between material properties, physical understanding, and device performance enabled rapid progress which eventually led to the successful fabrication of state of the art HEMT transistors and amplifiers.« less