High Power Directional Coupler with Equal Tunable Coupling Value at 352MHz and 704MHz

This paper shows design details of a high-power directional coupler, with adjustable coupling factor within the range from -13 dB to -26 dB, equally at two frequencies 352 MHz and 704 MHz, maintaining the level of return losses below -27 dB. The coupling value is adjustable with the use of a tuning mechanism allowing for changing the distance between the coupled line and the central coaxial line core. The application of the coupler is to work in high radiation environment (particle accelerator), therefore instead of typically used dielectric materials, e.g., teflon, PEEK (Polyether Ether Ketone) is used. The coupler has been manufactured and measured, showing high performance for coupling values within the whole tunable coupling range.