Patent ID: 7755534

Claim:
A radar sensor which receives a radar wave, reflected from a target object and transmitted through a wave transmission member in each of a plurality of antenna elements corresponding to a plurality of receiving channels, as a received signal while judging existence of a wave attenuator attenuating at least one of the radar waves directed toward the wave transmission member, the radar sensor comprising: a preparation block that sets each of a preliminary judgment variable and a final judgment variable at an initial value, assigns the preliminary judgment variable to each of the receiving channels, and sets a first period of time and a second period of time including one first period of time or a plurality of first periods of time; a detecting block that detects an electric power level of the received signal received in each antenna element as the level of the corresponding receiving channel every first period; a maximum level channel extracting block that extracts a maximum level channel, having a maximum level among the levels of the receiving channels, from the receiving channels every first period; a difference calculating block that calculates a channel level difference between the maximum level of the maximum level channel and the level of each of the receiving channels other than the maximum level channel every first period; a candidate channel setting block that sets one receiving channel corresponding to one channel level difference, which is calculated in one second period and is equal to or larger than a candidate threshold value, as a candidate channel for each of the receiving channels other than the maximum level channel every second period; a non-candidate channel setting block that sets one receiving channel corresponding to one channel level difference, which is calculated in one second period and is smaller than a non-candidate threshold value being lower than the candidate threshold value, as a non-candidate channel for each of the receiving channels other than the maximum level channel every second period; a preliminary judgment variable incrementing block that increments the preliminary judgment variable of each receiving channel each time the receiving channel is set as the candidate channel and initializes the preliminary judgment variable of each receiving channel each time the receiving channel is set as the non-candidate channel; a final judgment variable increasing block that increases the final judgment variable by a renewal value each time the preliminary judgment variable of at least one receiving channel reaches or exceeds a preliminary judgment value in one second period; and an outputting block that outputs information indicating existence of the wave attenuator in response to the final judgment variable reaching a final judgment threshold value.