Spoof surface plasmon polariton transmission line structure, circuit board, and electronic device

A circuit board, comprising:

• a spoof surface plasmon polariton transmission line structure, comprising:
• a first dielectric substrate;
• a second dielectric substrate;
• a first metal strip;
• a second metal strip;
• and
• a third metal strip,
• wherein
• the first metal strip and the second metal strip are on two opposite surfaces of the first dielectric substrate,
• the first metal strip and the second metal strip separately extend in a first direction,
• a length of the first metal strip in the first direction is less than a length of the second metal strip in the first direction,
• in the first direction, a cross-sectional area of the first metal strip gradually decreases, at least one side of the second metal strip has a plurality of protrusion parts spaced apart,
• the second dielectric substrate is laminated on a same surface of the first dielectric substrate as the second metal strip,
• the third metal strip is on a surface of the second dielectric substrate and that faces away from the first dielectric substrate,
• the third metal strip extends in the first direction,
• a length of the third metal strip in the first direction is less than the length of the second metal strip in the first direction, and
• a cross-sectional area of the third metal strip gradually decreases in the first direction.