Planar antenna, planar array antenna, multi-axis array antenna, and wireless communication module

A planar antenna comprising:

• a planar radiation conductor;
• a common ground conductor;
• a first strip conductor located between the planar radiation conductor and the common ground conductor and extending in a direction at an angle of 45±3° with respect to a first axis in a first right rectangular coordinate system including first, second, and third axes;
• a second strip conductor located between the planar radiation conductor and the common ground conductor and extending in a direction orthogonal to a direction of extension of the first strip conductor;
• and
• an antenna ground conductor including in an outer periphery, at least one pair of sides located between the first and second strip conductors and the common ground conductor and being at an angle of 45±3° or −45±3° with respect to the first axis.