Adjustable Liquid Power Load for RF Systems

Safer and more reliable power load for high-power RF applications
The adjustable liquid power load is a highly safe and reliable system. Rapid power absorption with negligible temperature changes is achieved due to the mass and specific heat properties of the liquid. System matching, which is needed to provide maximum power transfer between the source and the load, is achieved by varying the solution's ionic concentration. Physical dimensions of the container can also be modified for different power handling capabilities. NASA Marshall has successfully developed and used a balanced system version of this technology with loads of up to 16 kW. For commercial application proof of concept, the system was redesigned as an unbalanced system with a much smaller footprint. The unbalanced system has been preliminarily tested at 100 W. For a target operating frequency, the unbalanced load is optimized to work with a VSWR of < 1.5 (Figure 1 ) within a 10% frequency bandwidth or better (Figure 2), which is within the commonly accepted ranges for most commercial applications. The unbalanced system prototype continuously dissipated 84 W for 60 minutes with a temperature rise of less than 2 degrees at the hottest point, proving its high reliability and efficiency. Neither prototype had scale buildup or corrosion issues resulting from the electrolyte-metal interaction at the electrodes.
Abstract: 
NASA Marshall Space Flight Center has developed an innovative radio frequency (RF) power load that absorbs high-power RF in a reliable, safe, and cost-effective way. Conventional, high-power RF power loads consist of a water-cooled carbon pile and are costly, are prone to failure, and require constant maintenance. By simplifying the system and using a liquid electrolyte as the resistive element, a new NASA technology reduces test load expenses substantially and requires little to no maintenance. Initially designed as a dummy load to replace the broadcast antenna during diagnostic testing, tuning, and installation while absorbing full transmitter power, the system can also be used as a reject load to dissipate wasted power in a high-power RF system caused by mismatched voltage standing wave ratio (VSWR). Both balanced and unbalanced system prototypes have been developed and tested as proof of concept and are scalable for any high-power RF application.
Benefits: 

Inexpensive: has a substantially lower cost compared to currently available dry or water-cooled systems

applications: 

Communications: radio, television and cellular

Military: radars, frequency jammers, and communications

Medicine: radiotherapy particle accelerators

Reps: 
Patent Number: 
7,831,225
Internal Laboratory Ref #: 
MFS-TOPS-30
Patent Status: 
Patent Issue Date: 
August 31, 2015
Agency
NASA
Region
Southeast
State: 
Alabama
Phone: 
256-544-9151
Email: 
terry.taylor@nasa.gov
Lab Representatives
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