A monitoring and alert system for a radar-based object detection device has a blockage detection circuit including elements that detect and warn of radar blockage from dirt or debris on a radome. Environmentally-applied or human-applied material becoming attached to a surface of the radome can block the radar signal from being radiated, or a target return/echo from being received, at a sufficient power level. The monitoring and alert system prevents a vehicle operator from assuming that the unit is functioning properly and that no targets exist in the radar field of view, when the radar is actually blocked by the dirt and debris. One electrode, or multiple spaced-apart electrodes, on the radome may be monitored for each electrode's respective “self-capacitance”. Thus, different regions of the radome may be separately and independently monitored for alerts when one or more regions of the radome are negatively-affected by the dirt or debris.
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