Slot array antenna and radar having the slot array antenna

A slot array antenna for use in at least one of transmission and reception of an electromagnetic wave of a predetermined band, the slot array antenna comprising:

• a first electrically conductive member having a first electrically conductive surface and a plurality of slots arranged in a first direction along the first electrically conductive surface;
• a second electrically conductive member having a second electrically conductive surface that opposes the first electrically conductive surface;
• a waveguide member being interposed between the first and second electrically conductive members and having an electrically-conductive waveguide face that opposes the first or second electrically conductive surface, the waveguide member extending alongside the first or second electrically conductive surface;
• and
• an artificial magnetic conductor extending around the waveguide member, wherein,
• the waveguide face, the first or second electrically conductive surface opposing the waveguide face, and the artificial magnetic conductor define a waveguide;
• the waveguide member includes
• a stem extending along a direction,
• a first joint portion and a second joint portion branching out from an end of the stem, the first and second joint portions each extending into a region between two adjacent slots among the plurality of slots,
• a first branch connected to an end of the first joint portion, the first branch extending from the end of the first joint portion in the first direction and coupling to one or more of the plurality of slots, and
• a second branch connected to an end of the second joint portion, the second branch extending from the end of the second joint portion in an opposite direction of the first direction and coupling to other one or more of the plurality of slots;
• each of the plurality of slots intersects the waveguide member or splits the waveguide member;
• the end of the stem is not located in the region between the two slots as viewed perpendicularly to the first electrically conductive surface;
• and
• a difference between a phase variation to occur when an electromagnetic wave of the band propagates from the end of the stem to a closest slot to the first joint portion and a phase variation to occur when the electromagnetic wave propagates from the end of the stem to a closest slot to the second joint portion is greater than π/4 and smaller than (¾)π.