Microwave transition device between a strip line and a rectangular waveguide where a metallic link bridges the waveguide and a mode converter
For associating different technologies of a microstrip line and of a rectangular waveguide, for example on a ceramic, in a transition device including a mode transformer between the line integrated into a printed circuit board, and the waveguide, the board includes a housing containing the waveguide with a large sidewall coplanar and coaxial to the strip of the line and another large sidewall fixed onto a metallic layer of the board at the bottom of the housing. A linking metallic element bridges a mechanical tolerance gap between the transformer and one of the line and the waveguide. The transformer can be integrated into the board, or into the waveguide in a microwave component.
1. A transition device comprising a mode transformer between a conductive strip line integrated into a printed circuit board, and a rectangular waveguide, characterized in that the board comprises a housing containing the waveguide having a large sidewall coplanar to the strip line and another large sidewall fixed onto a portion of a metallic layer of the board at a bottom of the housing, and the device comprises a gap bridged by a linking metallic element and located between the mode transformer and the waveguide.
2. The device according to claim 1 , wherein the linking metallic element comprises one or more side by side strips of metallic sheet, or several side by side metallic wires.
3. The device according to claim 1 , wherein the mode transformer comprises strip line segments having strip widths and thicknesses increasing from the strip line to the waveguide and having lengths approximately equal to one quarter of wavelength.
4. The device according to claim 3 , comprising shielding metallic layers extending along the strips of the strip line segments and coplanar to those strips and linked to the shielding metallic layers extending along- and coplanar to the strip of the line.
5. The device according to claim 1 , wherein the permittivities of a substrate of the board and the permittivities of a substrate of the waveguide are different.
6. The device according to claim 1 , wherein the waveguide is integrated into a dielectric substrate, said dielectric substrate being ceramic.
7. The device according to claim 1 , wherein the waveguide includes small sidewalls each comprising rows of staggered metallized holes.
8. A method for manufacturing a transition device comprising a mode transformer between a strip line integrated into a printed circuit board, and a rectangular waveguide, characterized by the following steps: arranging in the board a housing having a bottom consisting in a portion of metallic layer internal to the board, introducing the waveguide into the housing so that a large sidewall of the waveguide be coplanar to the strip line and another large sidewall of the waveguide be fixed onto the portion of the metallic layer, and forming and fixing a thin linking metallic element bridging a gap between the mode transformer and the waveguide.
9. The method according to claim 8 , comprising integrating strip line segments to the board so as to form the mode transformer, the strip line segments respectively including ground metallic layers superimposed in the board and metallic strips on a face of the board and having strip widths and thicknesses increasing from the strip line to the waveguide and lengths approximately equal to one quarter of wavelength, and fixing the linking metallic element to the widest strip of the line segments and to a large sidewall of the waveguide.
10. The method according to claim 8 , comprising integrating strip line segments to the waveguide structure so as to form the mode transformer, the strip line segments respectively including ground metallic layers superimposed in the structure of the waveguide and metallic strips on a face of the structure of the waveguide and having strip widths and thicknesses increasing from the strip line to the waveguide and lengths approximately equal to one quarter of wavelength, and fixing the linking metallic element to the strip of the line and at least large strip of the line segments.