Radio frequency device providing a transition unit for coupling a hollow waveguide to a differential pair transmission line having overlapping open loops
A transition unit of a radio frequency device provides a transition between a planar differential pair transmission line and a hollow radio frequency waveguide. It comprises a substrate layer arrangement with a planar differential pair transmission line arranged on one or more surfaces of at least one substrate layer, whereby an end section of the differential pair transmission line is configured as a radio frequency signal transition pattern. It further comprises an end section of a waveguide that is attached to the substrate layer arrangement and that superposes the radio frequency signal transition pattern. The waveguide is directed perpendicular to the substrate layer arrangement. An open end of the end section of the waveguide is attached to a first outer surface or a second outer surface of the substrate layer arrangement. The transition pattern comprises open loop shaped end sections of a first and second transmission line segment.
1. A radio frequency device ( 1 ), comprising:
a substrate layer arrangement ( 3 ) with a planar differential pair transmission line ( 7 ) arranged on one or more surfaces ( 10 , 11 ) of at least one substrate layer ( 4 , 5 ) of the substrate layer arrangement ( 3 ); and
a transition unit ( 2 ) providing a transition between the planar differential pair transmission line ( 7 ) and a hollow radio frequency waveguide ( 15 ), comprising
an end section ( 12 ) of the planar differential pair transmission line ( 7 ) that is configured as a radio frequency signal transition pattern ( 13 ),
an end section ( 14 ) of the waveguide ( 15 ) for radio frequency electromagnetic waves that is attached to the substrate layer arrangement ( 3 ) and that superposes the radio frequency signal transition pattern ( 13 ),
wherein the end section ( 14 ) of the waveguide ( 15 ) is directed perpendicular to the one or more surfaces ( 10 , 11 ) of the substrate layer arrangement ( 3 ) with the planar differential pair transmission line ( 7 ),
wherein an open end ( 17 ) of the end section ( 14 ) of the waveguide ( 15 ) is attached to a first outer surface ( 16 ) or a second outer surface ( 19 ) of the substrate layer arrangement ( 3 ),
wherein the end section ( 12 ) of the planar differential pair transmission line ( 7 ) comprises
a first end section ( 24 ) of a first transmission line segment ( 8 ) and
a second end section ( 25 ) of a second transmission line segment ( 9 ) are arranged towards each other at a distance in a direction perpendicular to the one or more surfaces ( 10 , 11 ) of the substrate layer arrangement ( 3 ), and
wherein the first end section ( 24 ) of the first transmission line segment ( 8 ) overlaps the second end section ( 25 ) of the second transmission line segment ( 9 ) across an overlapping section to form a capacitive coupling of the first and second end section ( 24 , 25 ) that enhances an inductive coupling between the radio frequency electromagnetic wave within the waveguide ( 15 ) and the end section ( 12 ) of the planar differential pair transmission line ( 7 ),
wherein the first and second end sections ( 24 , 25 ) of the first and second transmission line segments ( 8 , 9 ) each form an open loop,
wherein both the open loops of the first and second transmission line segments overlap each other to form the transition pattern ( 13 ).
2. The radio frequency device ( 1 ) according to claim 1 ,
wherein the radio frequency device ( 1 ) comprises several transition units ( 2 ) arranged adjacent to each other.
3. The radio frequency device ( 1 ) according to claim 2 ,
wherein opposite to the end section ( 14 ) of the waveguides ( 15 ) of the several transition units ( 2 ) a common back cavity ( 29 ) that extends along the several transition units ( 2 ) is arranged next to the substrate layer arrangement ( 3 ) with an open end ( 30 ) of the common back cavity ( 29 ) facing the substrate layer arrangement ( 3 ).
4. The radio frequency device ( 1 ) according to claim 1 ,
wherein a length of the overlapping first and second end sections ( 24 , 25 ) is less than ¼λ with λ being the wavelength of a radio frequency signal that is transmitted within the radio frequency device ( 1 ).
5. The radio frequency device ( 1 ) according to claim 1 ,
wherein a length of the overlapping first and second end sections ( 24 , 25 ) is less than 1/10λ with λ being the wavelength of a radio frequency signal that is transmitted within the radio frequency device ( 1 ).
6. The radio frequency device ( 1 ) according to claim 1 ,
wherein the first and second end sections ( 24 , 25 ) of the first and second transmission line segments ( 8 , 9 ) is electroconductively connected to a bias voltage source.
7. The radio frequency device ( 1 ) according to claim 6 ,
wherein the first and second end sections ( 24 , 25 ) of the first and second transmission line segment ( 8 , 9 ) form a symmetric pattern with respect to a cross-section of the end section ( 14 ) of the waveguide ( 15 ), and
wherein an electroconductive connection is positioned in a symmetry plane ( 28 ) with respect to the cross-section of the end section ( 14 ) of the waveguide ( 15 ) and perpendicular to the one or more surfaces ( 10 , 11 ) of the substrate layer arrangement ( 3 ).
8. The radio frequency device ( 1 ) according to claim 1 ,
wherein opposite to the end section ( 14 ) of the waveguide ( 15 ), a back cavity ( 18 ) is attached with an open end ( 21 ) of the back cavity ( 18 ) to the substrate layer arrangement ( 3 ),
wherein the back cavity ( 18 ) prevents a part of a radio frequency signal emission that is emitted from the transition pattern ( 13 ) from leaking outside of the end section ( 14 ) of the waveguide ( 15 ).
9. The radio frequency device ( 1 ) according to claim 1 ,
wherein the first and second transmission line segment ( 8 , 9 ) each having a portion which is curved at least in sections and arranged with respect to each other to form the overlapping first and second end section ( 24 , 25 ).