Precipitation determining device

A precipitation determining device mounted to a mobile unit, wherein the device comprises:

• a transmitting means that transmits a radar wave, the radar wave being frequency-modulated such that one measurement cycle has a rising section in which a frequency increases with time and a falling section in which a frequency decreases with time;
• a receiving means that receives an incoming wave which is a reflected wave of a radar wave transmitted from the transmitting means, and mixes the received incoming wave with the radar wave transmitted from the transmitting means to derive respective beat signals for the rising section and the falling section;
• an analyzing means that performs frequency analysis of the beat signals generated by the receiving means and derives respective frequency spectra of the beat signals for the rising section and the falling section;
• and
• a precipitation determining means that determines presence/absence of precipitation when the frequency analysis performed by the analyzing means shows absence of an object from a transmission range of the radar wave, the presence/absence of precipitation being determined based on spectral similarity that is a degree of similarity of the frequency spectra with precipitation reference spectra, the frequency spectra being derived from both sections of the rising section and the falling section generated by the analyzing means, and the precipitation reference spectra exhibiting a lower frequency intensity, meaning a longer distance to a source of the incoming wave and a higher frequency intensity, meaning a shorter distance to the source.