High-Power Water-Cooled RF Load

Abstract

This paper presents the design of a water-cooled radio-frequency(RF) load with simple structure, for use in the ultrahigh-frequency (UHF) band. After establishing a formula to obtain the physical properties that affect RF matching, we measure the permittivity and tanδ(Loss tangent) of tap water. Because the temperature of tap water increases upon applying high power, we measure the permittivity and tanδ for all changes in the temperature of tap water. In order to reduce the length of the water-load, molybdate with high tanδ is mixed with tap water. The loss tangent of the mixture is found to be approximately 26 times higher than that of tap water. Finally, we manufacture a water-cooled RF load and measure its characteristics. A reflection coefficient of −19 dB and bandwidth of 15 % is obtained at 460 MHz.