A radar sensing system for a vehicle includes a radar sensor disposed at the vehicle so as to sense exterior of the vehicle. The radar sensor includes a plurality of transmitters that transmit radio signals, and a plurality of receivers that receive radio signals, with the received radio signals being transmitted radio signals that are reflected from an object. A processor is operable to process outputs of the receivers. The radar sensor includes a printed circuit board having circuitry disposed thereat and at least one waveguide having an interface end in electrical contact with the printed circuit board. The at least one waveguide includes at least one notch at the interface end that reduces an area of electrical contact between the at least one waveguide and the printed circuit board and increases pressure at the electrical contact area.