Doppler motion sensor device with high isolation between antennas

A radar device for detecting a spatial information of an object, comprising:

• a first antenna configured to access a first wireless signal, comprising:
• a first middle point at a centroid of the first antenna;
• and
• a feed zone having a first zone shape centroid, and configured to access a first internal signal corresponding to the first wireless signal between the first antenna and a sensor circuit;
• and
• a second antenna configured to access a second wireless signal, comprising:
• a second middle point at a centroid of the second antenna;
• and
• another feed zone having a second zone shape centroid, and configured to access a second internal signal corresponding to the second wireless signal between the second antenna and the sensor circuit;
• wherein an angle formed between a first straight line and a second straight line is not less than 45 degrees and is not larger than 90 degrees, the first straight line passes through the first zone shape centroid and the first middle point, the second straight line passes through the second zone shape centroid and the second middle point, one of the first wireless signal and the second wireless signal is reflected by the object to form another one of the first wireless signal and the second wireless signal, and the sensor circuit is configured to detect the spatial information of the object according to at least the first internal signal and the second internal signal.