Patent ID: 7532151

Claim:
A proximity sensor comprising: an electrically conductive member integrally or separably mounted on a mounting object, a detection area made of an electromagnetic wave radiation space set at an outside of the said electrically conductive member and accompanying a change of a humidity, a temperature and a barometric pressure, and a microwave circuit making the said electrically conductive member act as an antenna and radiate microwaves of a sufficiently short wavelength relative to a size of the said electrically conductive member so as to detect an existence of a detection object residing in a space inside the said detection area as a change of an eigenvalue of a radio wave propagation, thereby detecting the change of the said eigenvalue by the said microwave circuit as a change of the said detection area, wherein the change of the eigenvalue of the said radio wave propagation is detected by use of a mixer, which makes the frequency of the said electrically conductive member passed through a directional coupler connected to the feeding point of the UWB oscillator and a bandpass filter and thereafter amplified by an amplifying means while inputting a down-converting frequency for mixing, and a recognition circuit detecting the change of the said detection area by a frequency passed through the said mixer.