Cavity slotted-waveguide antenna array, a method of manufacturing a cavity slotted-waveguide antenna array, and a radar antenna module comprising cavity slotted-waveguide antenna arrays
A cavity slotted-waveguide antenna array has several waveguide columns disposed in parallel in a housing. Several of the waveguide columns being provided with cavity slots on the front side of the housing. The housing includes a front part secured to a rear part, with a rear portion of the waveguide columns being formed in the rear part, and with a front portion of the waveguide columns being formed in said front part. The waveguide columns can have a rectangular cross-section, with the columns defined by two opposing wide inner surfaces, a narrow inner back surface, and a narrow inner front surface, with the plurality of cavity slots extending from the front side of the housing to said narrow inner front surface. A signal probe is disposed in the columns. Conductive parallel plate blinds are conductively secured to the front side of the housing.
1. A radar antenna module comprising:
one or more planar radiating narrow sided cavity slotted-waveguide antenna arrays configured for radiating horizontal polarized electromagnetic waves; and
one or more planar receiving narrow sided cavity slotted-waveguide antenna arrays configured for receiving horizontal polarized electromagnetic waves;
wherein each of the radiating and receiving antenna arrays comprises several waveguide columns disposed in a parallel and adjacent position with respect to one another in a respective housing, said housing having a front side and a rear side with the waveguide columns being provided with a plurality of cavity slots on the front side of the housing;
wherein the radiating and receiving antenna arrays are arranged with the waveguide columns of the radiating antenna arrays disposed in a parallel position to the waveguide columns of the receiving antenna arrays;
wherein the radiating and receiving antenna arrays are arranged with the longitudinal direction of the waveguide columns extending in a single horizontal direction;
wherein the cavity slots on the front side of the respective housing of one or more radiating antenna arrays are arranged in a single radiating plane extending in a vertical direction; and
wherein the cavity slots on the front side of the respective housing of one or more first receiving antenna arrays are arranged in a partially upwards facing side of a single, first receiving plane, wherein said partially upwards facing side of the first receiving plane faces a first, slightly upwards inclined direction, and wherein said partially upwards facing side of the first receiving plane forms a first acute angle to the vertical direction.
2. The radar antenna module according to claim 1 , wherein the waveguide columns of the radiating and receiving antenna arrays are of equal length.
3. The radar antenna module according to claim 1 , wherein the cavity slots on the front side of the respective housing of one or more second receiving array(s) are arranged in a partially upwards facing side of a single, second receiving plane, wherein said partially upwards facing side of the second receiving plane faces a second, upwards inclined direction, said second inclined direction being more upwards inclined than the first, slightly inclined direction, and wherein said partially upwards facing side of the second receiving plane forms a second acute angle to the vertical direction with the second angle being larger than the first angle.
4. The radar antenna module according to claim 1 , wherein said one or more first receiving antenna arrays are placed or stacked on top of the one or more radiating antenna arrays, which radiating antenna arrays have the cavity slots on the front side of the housing(s) arranged in the single radiating plane, and
wherein said one or more second receiving antenna arrays are placed or stacked on top of the one or more first receiving antenna arrays.
5. The radar antenna module according to claim 1 , wherein each of the radiating and receiving antenna arrays comprises eight waveguide columns,
wherein said one or more radiating antenna arrays, which have the cavity slots on the front side of the respective housing arranged in the single radiating plane, comprise a total of 24 waveguide columns,
wherein said one or more first receiving antenna arrays comprise a total of 40 waveguide columns, and
wherein said one or more second receiving antenna arrays comprise a total of eight waveguide columns.
6. The radar antenna module according to claim 3 , wherein the first acute angle is in the range of 5-25°, such as in the range of 10-20°, such as about 15°, and wherein the second acute angle is in the range of 30-60°, such as in the range of 35-55°, such as in the range of 40-50°, such as about 45°.
7. The radar antenna module according to claim 1 , wherein the radiating antenna arrays, which are arranged with the cavity slots on the front side in said radiating plane, are connected together by a number of parallel plate blinds secured to the front side of the radiating antenna array housings between the cavity slots and substantially perpendicular to the longitudinal direction of the waveguide columns, and
wherein the first receiving antenna arrays, which are arranged with the cavity slots on the front side in said first receiving plane, are connected together by a number of parallel plate blinds secured to the front side of said first receiving antenna array housings between the cavity slots and substantially perpendicular to the longitudinal direction of the waveguide columns.
8. The radar antenna module according to claim 3 , wherein the one or more second receiving antenna arrays comprises a single second receiving antenna array, which is arranged with the cavity slots on the front side in said second receiving plane, said second antenna array having a number of parallel plate blinds secured to the front side of the housing between the cavity slots and substantially perpendicular to the longitudinal direction of the waveguide columns.
9. The radar antenna module according to claim 1 , wherein the radiating and receiving planar slotted-waveguide antenna arrays are arranged within a protective radome, which radome has a front part with an inner surface and an outer surface, said front part covering the front side of the respective housing of each of the radiating and receiving antenna arrays with a constant spacing between the front side of said array housings and said inner surface of the radome front part.
10. The radar antenna module according to claim 9 , wherein said constant spacing is substantially equal to two times a distance between respective centres of two neighbouring cavity slots of a waveguide column of the waveguide columns, or substantially equal to a guided signal wavelength (λg) of the waveguide columns of the radiating and receiving antenna arrays, and
wherein a thickness of said radome front part is substantially equal to half the distance between the centres of the two neighbouring cavity slots of the waveguide column, or substantially equal to a quarter of a guided signal wavelength (Ag) of the waveguide columns of the radiating and receiving antenna arrays.
11. The radar antenna module according to claim 9 , wherein the radome is made of a thermoplastic material, such as a blend of polymethyl methacrylate and polyvinyl chloride, PMMA/PVC.