Image Number 11 for United States Patent #7612706.
An antenna unit includes at least one transmission antenna and plural reception antennas. A receiver detects information including azimuth information for a target, based on an output from the antenna unit. An antenna switching unit switches connections between a transmitter and the transmission antenna and between the reception antenna and the receiver. The antenna unit includes a wide-beam array antenna and plural narrow-beam array antennas having a narrower beam width than the array antenna. A monopulse process is performed based on an output of a predetermined pair of array antennas from among the array antennas formed as the narrow-beam array antennas.