Radar signal device where a projection of a feed structure at least partially overlaps with an opening on a metal layer

A radar signal device comprising:

• an antenna unit configured to transmit a transmission signal and receive a reception signal concurrently during a time interval, the antenna unit comprising:
• a first metal layer, where a first opening and a third opening are formed on the first metal layer and pass through the first metal layer;
• a first feed structure configured to receive a first internal signal, where the transmission signal is generated according to at least the first internal signal, and a first projection of the first feed structure on the first metal layer at least partially overlaps with the first opening;
• and
• a second feed structure configured to transmit a second internal signal, where the second internal signal is generated according to at least the reception signal, and a second projection of the second feed structure on the first metal layer at least partially overlaps with the third opening;
• a transmission circuit configured to generate the first internal signal;
• and
• a reception circuit configured to generate a processed signal related to the second internal signal;
• wherein the antenna unit is configured to form a first radiation pattern and a second radiation pattern, the first radiation pattern is used to transmit the transmission signal and has a first co-polarized electric field direction, the second radiation pattern is used to receive the reception signal and has a second co-polarized electric field direction, and an angle between the first co-polarized electric field direction and the second co-polarized electric field direction is between 45 degrees and 135 degrees.