Automotive sensor module with absorptive and/or non-reflective layer
Antenna assemblies for vehicles, such as RADAR sensor antenna assemblies. In some embodiments, the assembly may comprise a waveguide block defining an array of waveguide grooves and an array of antenna slots. Each antenna slot in the array of antenna slots may be at least partially aligned with a waveguide groove of the array of waveguide grooves of the waveguide block. The assembly may further comprise an absorptive layer comprising an array of openings corresponding with the array of antenna slots. The absorptive layer may be configured to dissipate surface currents on the waveguide block such as, for example, by way of the material used to form the absorptive layer and/or the thickness of the absorptive layer and/or to suppress fascia reflections.
1 . A vehicle sensor module, comprising:
a waveguide block defining an array of waveguide grooves;
an array of antenna slots, each antenna slot in the array of antenna slots at least partially aligned with a waveguide groove of the array of waveguide grooves of the waveguide block, wherein each antenna slot of the array of antenna slots extends from a first side of the waveguide block to a second side of the waveguide block to allow electromagnetic radiation to travel through the array of antenna slots;
an absorptive layer comprising an array of openings corresponding with the array of antenna slots, wherein the absorptive layer is configured to suppress surface currents on the waveguide block;
a radome layer positioned on top of the absorptive layer, wherein the radome layer lacks openings so as to provide a seal for the waveguide block, wherein at least a subset of the antenna slots is positioned on raised islands comprising elevated walls extending above a recessed region, and wherein the absorptive layer is positioned within the recessed region; and
a raised lip extending about a perimeter of the waveguide block, wherein the radome layer is positioned within the recessed region and below the raised lip, and wherein the radome layer and the absorptive layer are positioned adjacent to each other within a recessed region of the waveguide block.
2 . The vehicle sensor module of claim 1 , wherein the radome layer comprises a laminated layer comprising a plurality of sub-layers, wherein at least one of the sub-layers is configured to adhere the radome layer to the absorptive layer, and wherein at least one of the sub-layers is configured to increase a strength of the radome layer.
3 . The vehicle sensor module of claim 1 , wherein the array of waveguide grooves comprises a plurality of waveguide grooves.
4 . The vehicle sensor module of claim 1 , wherein the absorptive layer has a thickness equal to about an odd integer multiple of one-quarter of a wavelength of electromagnetic radiation used in the vehicle sensor module.
5 . The vehicle sensor module of claim 1 , wherein the absorptive layer comprises a lossy material.
6 . The vehicle sensor module of claim 5 , wherein the absorptive layer comprises a material having a dielectric constant of between 6 and 14 and a dielectric loss tangent of between 0.2 and 0.6.
7 . A vehicle sensor antenna assembly, comprising:
a metallic waveguide block defining an array of waveguide grooves;
an antenna assembly comprising at least one antenna slot configured to receive electromagnetic radiation from the array of waveguide grooves therethrough; and
an absorptive layer configured to generate a destructive interference pattern to reduce reflectivity of the electromagnetic radiation incident upon the vehicle sensor antenna assembly, wherein the antenna assembly is part of the metallic waveguide block such that the at least one antenna slot is formed within the metallic waveguide block and extends between opposite surfaces of the metallic waveguide block, wherein the metallic waveguide block comprises a recessed region, wherein the absorptive layer is positioned within the recessed region, wherein the recessed region is defined by a lip extending about a perimeter of the metallic waveguide block and elevated walls extending about the perimeter of each antenna slot of the at least one antenna slot, and wherein the recessed region comprises a height that is more than a thickness of the absorptive layer.
8 . The vehicle sensor antenna assembly of claim 7 , wherein the antenna assembly comprises an antenna slot corresponding to each waveguide groove of the array of waveguide grooves.
9 . The vehicle sensor antenna assembly of claim 7 , wherein the absorptive layer comprises one or more openings positioned such that each antenna slot of the at least one antenna slot is positioned below an opening of the one or more openings.
10 . The vehicle sensor antenna assembly of claim 7 , wherein the absorptive layer comprises a dielectric constant of between about 6 and about 14.
11 . The vehicle sensor antenna assembly of claim 7 , wherein the absorptive layer comprises a dielectric loss tangent of between about 0.2 and about 0.6.
12 . The vehicle sensor antenna assembly of claim 7 , further comprising a radome layer positioned within the recessed region.
13 . The vehicle sensor antenna assembly of claim 7 , further comprising a radome layer, wherein the recessed region comprises a height that is greater than a thickness of the absorptive layer and the radome layer combined.
14 . A vehicle RADAR module, comprising:
a metallic waveguide block defining a waveguide groove and comprising a recessed region;
an antenna slot at least partially aligned with the waveguide groove of the metallic waveguide block, wherein the antenna slot extends entirely through the metallic waveguide block from a first surface of the metallic waveguide block to a second surface of the metallic waveguide block opposite the first side to allow electromagnetic radiation to travel therethrough;
an absorptive layer seated in the recessed region, the absorptive layer comprising a lossy material, wherein the absorptive layer comprises an opening at least partially aligned with the antenna slot and the waveguide groove, wherein the absorptive layer is configured to contact the metallic waveguide block to suppress surface currents on the metallic waveguide block, and wherein the absorptive layer comprises a thickness configured to suppress reflections of the electromagnetic radiation by generating destructive interference between reflections of the electromagnetic radiation above the absorptive layer with reflections of the electromagnetic radiation below the absorptive layer; and
a radome layer configured to provide a weather seal to the vehicle RADAR module, wherein the radome layer is seated in the recessed region, wherein the recessed region is defined by a lip extending about a perimeter of the metallic waveguide block, and wherein the recessed region comprises a height that is more than a thickness of the absorptive layer.
15 . The vehicle RADAR module of claim 14 , wherein the absorptive layer has a thickness equal to about an odd integer multiple of one-quarter of a wavelength of electromagnetic radiation used in the vehicle RADAR module.
16 . The vehicle RADAR module of claim 14 , wherein the absorptive layer is formed from a liquid cured within the recessed region of the metallic waveguide block.
17 . The vehicle RADAR module of claim 14 , wherein the recessed region comprises a height that is greater than a thickness of the absorptive layer and the radome layer combined.