Abstract: A radar sensor includes: a transceiver unit for emitting a radar beam at at least two different wavelengths along a beam path in an outgoing direction and to receive radar radiation along the beam path in an incoming direction; and a reference object placed in the beam path for redirecting part of the outgoing radar beam in the incoming direction. The reference object includes two identical grids, each grid having regularly spaced elements arranged at a distance d from each other in a first direction perpendicular to the beam path, the grids being spaced from one another along the beam path by a distance L. The transceiver unit is operable at a wavelength ? which satisfies L = n ? 2 ? d ? 2 n being an integer.

Abstract: A radar sensor includes: a transceiver unit for emitting a radar beam at at least two different wavelengths along a beam path in an outgoing direction and to receive radar radiation along the beam path in an incoming direction; and a reference object placed in the beam path for redirecting part of the outgoing radar beam in the incoming direction. The reference object includes two identical grids, each grid having regularly spaced elements arranged at a distance d from each other in a first direction perpendicular to the beam path, the grids being spaced from one another along the beam path by a distance L. The transceiver unit is operable at a wavelength ? which satisfies L = n ? 2 ? d ? 2 n being an integer.

Abstract: A radar sensor includes: a transceiver unit for emitting a radar beam along a beam path in an outgoing direction and receiving radar radiation along the beam path in an incoming direction; and a reference object placed in the beam path to redirect part of the outgoing radar beam in the incoming direction. The reference object is one of a plurality of reference objects placed in the radar beam. A size of the reference objects in at least one dimension is smaller than a wavelength of the radar beam.

Abstract: In a fiber-optic sensor for alternating electric fields or voltages, the interference in a bimodal fiber (3) is measured passively. To this end, the mutually phase-shifted near-field and remote-field signals are separated by optical means (15) at the exit end of the bimodal fiber (3), and passed to appropriate detectors (17a, b, c), and the electrical signals created are evaluated by electronic means (18).