Patent ID: 12261345

DETAILED DESCRIPTION OF THE INVENTION

InFIGS.1and2, a perspective sectional view of an exemplary part of a radio frequency device1with a transition unit2according to the present invention is shown inFIG.1. The radio frequency device1is with an arrangement of two substrate layers with a planar differential pair transmission line arranged between facing surfaces of the substrate layers, with an end section of a hollow waveguide positioned at a top surface of a substrate layer arrangement comprising the two substrate layers, whereby an end section of the hollow waveguide superposes the radio frequency signal transition pattern of the planar differential pair transmission line, and with a back cavity opposingly attached to a back surface of the substrate layer arrangement. The radio frequency device1comprises a substrate layer arrangement3that comprises a first substrate layer4and a second substrate layer5, each made of an electrically non-conducting material, e.g. glass. The first and second substrate layer4,5are arranged parallel and at a distance towards each other. The volume between the first and second substrate layer4,5is filled with a tunable dielectric material6, e.g. a liquid crystal material with variable and controllable dielectric properties. The volume between the first and second substrate layer4,5can be segmented to allow for many small segments or chambers that are filled with the tunable dielectric material6. The dielectric properties of the tunable dielectric material6can be controlled e.g. by applying a bias voltage to bias electrodes on opposite sides of the volume or of a small segment for which the dielectric properties of the tunable dielectric material are to be preset or modified.

A planar differential pair transmission line7with two parallel transmission line segments8,9of an electrically conducting material is arranged on a first surface10of the first substrate layer4and on a second surface11of the second surface layer5of the substrate layer arrangement3. The first surface10and the second surface11are facing each other and confine the volume between the first and second substrate layer4,5. The planar differential pair transmission line7inFIG.1extends into an end section12inFIG.1that is configured as a radio frequency signal transition pattern13. The transition pattern13as viewed from a top view perpendicular to the first and second surface10,11of the substrate layer arrangement3forms an open loop structure that is oval shaped within this embodiment. InFIG.1the first transmission line segment8is represented by a dashed line and the second transmission line segment9is represented by a dotted line. Both transmission line segments8,9run parallel and with a distance towards each other into the end section12forming an overlapping transition pattern. A small deviation parallel to the first and second surface10,11is shown for clarification only, as both transmission line segments8,9exactly overlap within the end section12.

An end section14of a hollow waveguide15made from an electroconductive material is also arranged on a first outer surface16of the substrate layer arrangement3. An open end17of the end section14of the hollow waveguide15superposes the radio frequency signal transition pattern13of the end section12of the planar differential pair transmission line7, as can be seen inFIG.2. Thus, a radio frequency signal that is transmitted along the planar differential pair transmission line7towards the end section12will be emitted from the frequency signal transition pattern13. A part of the emitted signal power will be directed through the open end17and into the hollow waveguide15. Another part of the emitted signal power will be directed into an opposite direction.

Opposite to the end section14of the hollow waveguide15there is a back cavity18as shown inFIG.2that is mounted onto a second outer surface19of the substrate layer arrangement3, whereby the second outer surface19is opposite to the first outer surface16of the substrate layer arrangement3. A distance between the second outer surface19of the substrate layer arrangement3and a back side20of the back cavity18that opposes the second outer surface19is larger than the distance between opposing parts of the circumferential line of a cross-section of an open end21of the back cavity18, i.e. larger than a distance between opposing wall sections22,23around the open end21of the back cavity18.

A shape of the open end21of the back cavity18equals the shape of the open end17of the hollow waveguide15. Furthermore, the open end21of the back cavity18is positioned opposing to the end section14of the hollow waveguide15in a manner as to fully superimpose the open end17of the hollow waveguide15. A large part of the signal power that is directed into the direction of the back cavity18will be reflected and fed into the hollow waveguide15. By adding the back cavity18to the transition unit2, an unwanted leakage of radio frequency signal emission from the transition unit2can be significantly reduced.

FIGS.3to8show a part of a top view and a respective sectional view of three different embodiments of a transition unit2of the radio frequency device1that is designed according to the invention.FIGS.3and4illustrate an end section12as shown inFIG.3of the planar differential pair transmission line7that forms an oval-shaped open loop transition pattern13as shown inFIG.3. A first end section24of the first transmission line segment8is shown with solid lines, whereas a second end section25of the second transmission line segment9is shown with dashed lines. A small deviation in a direction parallel to the first outer surface16as shown inFIG.3is only for clarification purposes, as both first and second end section24and25exactly overlap each other within the transition pattern13.

FIGS.5and6illustrate another embodiment of the transition unit2as shown inFIG.1of a radio frequency device1as shown inFIG.1. The first and second end section24,25of the respective first and second transmission line segment8,9form a rectangular shaped open loop transition pattern13as shown inFIG.5. The distance between the first and second transmission line segment8,9is larger than with the embodiment that is illustrated inFIGS.3and4. However, it is also possible to arrange both the first and second transmission line segment8,9in such a manner that the first and second transmission line segments run with a smaller distances towards each other into the end section12as shown inFIG.5of the planar differential pair transmission line7as shown inFIG.1and the transition pattern13that is formed by the overlapping first and second end sections24,25.

FIGS.7and8illustrate yet another embodiment of the transition unit2as shown inFIG.1with first and second end sections24,25that form a circular shaped open loop transition pattern13as shown inFIG.7. Each of the first and second end section24,25is electroconductively connected by an electroconductive line segment26,27to a bias voltage source31that is not shown inFIGS.7and8and is shown inFIG.11. The electroconductive line segments26,27are arranged along a symmetry plane28with respect to the cross-section of the end section14as shown inFIG.8of the waveguide15and perpendicular to the one or more surfaces10,11,19(as shown inFIG.8)16, of the substrate layer arrangement3. The open loop transition pattern13formed by the first and second end sections24,25is also designed and arranged to be symmetric with respect to the symmetry plane28.

FIGS.9and10illustrate yet another aspect of the radio frequency device1as shown inFIG.1with several transition units2arranged along a straight line. Three hollow waveguides15are shown that represent a row of transition units2as shown inFIG.1which might comprise more than three hollow waveguides15. At an opposite side of the substrate layer arrangement3there is a common back cavity29that partially overlaps with the end sections14as shown inFIG.10of the hollow waveguides15, but extends over many or all end sections14of the hollow waveguides15that are aligned along the row. An open end of the common back cavity29faces the substrate layer arrangement3and thus the several hollow waveguides15arranged at an opposite side of the substrate layer arrangement3. Most part of a radio frequency signal emission that is emitted by the frequency signal transition pattern13′ as shown inFIG.1of the planar differential pair transmission line7as shown inFIG.1will be directed either into the first hollow waveguide15that is arranged on the first outer surface16as shown inFIG.9of the substrate layer arrangement3or into the common hollow waveguide29that is arranged on the second outer surface19of the substrate layer arrangement3opposing the first hollow waveguide15. The undesired leakage of radio frequency signal emission from the transition unit2will be significantly reduced.