Dual-band circularly polarized antenna structure

A dual-band circularly polarized antenna structure, comprising:

• an antenna unit disposed on a first substrate, the antenna unit comprising:
• a first radiator having a feed-in portion and a first spiral pattern, wherein the first spiral pattern spirals outwardly from a starting point close to the feed-in portion;
• and
• a second radiator having a first grounding portion corresponding to a position of the feed-in portion, and a second spiral pattern, wherein the second spiral pattern spirals outwardly from a starting point close to the first grounding portion in a manner non-overlapping with the first spiral pattern, and one of the first radiator and the second radiator further has a second grounding portion;
• a microstrip line disposed on a second substrate, wherein the second substrate is disposed in parallel with the first substrate and spaced apart by a distance, and the feed-in portion of the first radiator of the antenna unit is coupled to the microstrip line;
• and
• a ground disposed on the second substrate, wherein the second grounding portion and the first grounding portion are coupled to the ground.