Development of a planar helix slow-wave structure based on ball-grid array technology

Abstract

The fabrication process for a planar helix slow-wave structure (SWS) based on ball-grid array (BGA) technology is developed to be used in the traveling wave tube (TWT). The planar helix layers are structured on two printed circuit boards and the solder ball is used to connect each other upside down. The material properties of the used substrate and also the solder ball connection for being used by TWT are described. Additional to previous work, filled via paths are applied inner side of the RF-substrate as an enhancement of thermal management. A typical planar helix is modeled, and the parameters of the cold and hot tests are calculated in CST microwave studio. The simulation results show that the proposed structure has high interaction impedance and wide bandwidth. The fundamental space harmonic mode overlaps with a 5.5 kV electron beam in the dispersion diagram. The scattering parameters are reported for 100 periods of the proposed structure that 1−15 GHz frequency range has a minimum reflection. The maximum gain of 22 dB is achieved at 10 GHz frequency.

Keywords:

• Traveling wave tube
• planar helix
• solder ball connection
• ball-grid array

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Akbar Babaeihaselghobi

Akbar Babaeihaselghobi is currently pursuing a Ph.D. degree with the Sahand University of Technology, Tabriz, Iran. He was with the Department of Micro- and Nanosystem Technology, University College of Southeast Norway, Borre, Norway as visiting research (August 2018- January 2019). His current research interests include the vacuum electronic terahertz source, slow-wave structures, traveling wave tube amplifiers, RF-MEMS systems.

Habib Badri Ghavifekr

Habib Badri Ghavifekr he received his M.Sc. and Ph.D. both in electrical engineering from Technical University of Berlin. Since 2005 he is at Sahand University of Technology, Tabriz, Iran and nowadays he serves as an associate professor. His research interests are microsystem technologies, microelectronic packaging, MEMS, and electronic measurement systems for industrial applications.