Field of the invention

The invention relates to a coaxial RF connector system which can be connected or disconnected under load.

Description of the related art

A coaxial RF connector system is disclosed in EP 3 300535 Al. This connector system can couple comparatively high RF power up to a few kilowatts. For con necting and/or disconnecting, the power must be switched off. If these connect- ors are connected or disconnected under load, arcing may occur which may lead to a severe damage of the connectors. Further, there are no precautions to avoid an early connection between the center conductors during connecting or a late disconnection of the center conductors while disconnecting, specifically due to arcing. A center connector contact without shield or ground contact may incur a safety risk, as an ungrounded section of the conductor system may be at a high voltage. This may be harmful for person operating the connectors.

A 3 dB directional coupler is disclosed in US 4,754,241 A. It includes two sets of strip lines which are arranged parallel, close to each other with a small gap be tween the strip lines.

Summary of the invention

The problem to be solved by the invention is to provide an RF connector system which is able to transfer high RF power in the range of multiple kilowatts and which can be safely connected and/or disconnected when RF voltage is applied to at least one side of the connector system.

Solutions of the problem are described in the independent claims. The depend ent claims relate to further improvements of the invention. A connector system according to an embodiment is based on a pair of contact less couplers. The coupler structure is similar to a S dB coupler which has only one input and one output, thus acting as a zero dB coupler. The coupler may be based on strip line technology and may have a strip line having a length of l¼, which is ¼ of the wavelength of the signal to be coupled. In a connected state two strip lines are close to each other. In a disconnected state, the strip lines may be distant from each other such that there is no more any coupling between the strip lines. There may be a guiding mechanism such that the connecting and disconnecting process is made by a linear movement of shifting or displacing the two sets against each other. The strip lines may be bent or folded at least one time or multiple times to reduce the size of the couplers.

In an embodiment, an RF-connector includes two almost symmetrical and/or identical coupler sections. Each coupler section may include a housing which holds a conductor. Each housing may have basically a cuboid shape which may have an open side and which may form an open cavity having a shape of an elon- gated channel for the conductor. The shape of the housing may be comparatively flat. Typical dimensions may be a length and a width in a range of between 20 mm and B00 mm. The height of the housing may be between 3 mm and 50 mm.

The dimensions of the housing are determined by the conductor inside the hous ing, which may have a length corresponding to ¼ of the nominal frequency of a signal to be coupled. Each conductor has an elongated structure of a flat conduc tive material. It may include a strip of copper or brass or even aluminum which may further be coated with a conductive material, e.g., silver or gold on its outer surface. A conductor may have a width in a range of between 1/100 to 1/5 of its length and may have a thickness in a range of between 0.5 mm and 5 mm. The conductor may be wider than its thickness. The conductor may be arranged in the open cavity of the housing and recessed against the outer surface of the housing. Therefore, the conductor may not protrude from the surface of the housing. The conductor may be connected with a first end to a coaxial connector to provide electrical contact. Instead of a connector, a further strip line or any kind of waveguide may be provided. On its second end opposing to the first end, the conductor may be connected to the housing. It may specifically be connected to a sidewall of the housing.

The RF-connector basically is intended to have the function of a switch, and therefore may also be considered as a switching coupler. It may be switched be tween an ON-state and an OFF state. In the OFF state, a first coupler section is distant from a second coupler section. Distant means that the conductors of two opposing coupler sections do not overlap, but edges of the housings may touch.

To achieve a higher isolation, the coupler sections may be distant from each other without touching each other. Further, a cover may be provided to cover at least one or both of the open sides of the coupler sections, when they are in an OFF state and therefore distant from each other. This provides a closed system for each coupler section which cannot radiate, such that there is a higher isola tion between the couplers.

In the ON-state, the first coupler section is in close contact and/or close proxim ity with the second coupler section. Accordingly, the open sides of the housings may be oriented against each other and may be overlapping. This may form a common cavity between the two housings with the conductors facing each other, preferably over their full length and/or width. But normally, the conduc tors would not touch each other. They may for example, be recessed against the surface of the housing. These close facing conductors provide a non-galvanic coupling for RF-signals in the ON-state. In contrast thereto, in the OFF state, each coupler section is a l/4 transformer providing a virtual open circuit at its coaxial connector.

In an embodiment, the conductors may be arranged in separate planes, such that the planes are parallel in an ON-state. The conductors may be mirror-sym metrical about a symmetry plane between the planes of the conductors. The symmetry plane may be parallel to the planes of the conductors.

In an embodiment, the conductors have a curved shape. Such a curved shape may include angles, bends and edges.

In an embodiment, in an ON state, the conductors may be separated by an es sentially constant distance. So, the conductors may never touch and maintain a galvanic insulation between them. The conductors may have slightly varying dis tances due to manufacturing tolerances or due to minor bending for optimizing coupling characteristics.

In an embodiment, in an ON state, the conductors may be separated by a dis tance smaller than 1/10 of a nominal wavelength of a signal to be coupled.

To perform a proper switching function, further a mechanical support structure may be provided which guides the movement of the coupler sections between the ON- and OFF state. This may be a linear guide system, which may include lin ear rails or similar guiding structures. Further, the mechanical support structure may provide means to hold the coupler section in either ON- and/or OFF state.

In an embodiment, each coupler section may be contained in a housing. Each housing may hold a conductor. Further each housing may have a cuboid shape with an open side forming an open channel, such that each conductor may be lo cated in an open channel. In the ON state the open sides of the housings are ori ented against each other. In another embodiment, both coupler sections are contained in a common hous ing holding both conductors. Here, at least one of the conductors is movable within the housing relative to the other conductor. The housing may be closed completely with only two coaxial connectors for connecting the conductors. In another embodiment, the housing may have one or two open sides, such that it may have a shape of a rectangular waveguide.

Further, a short circuit element may be provided at an off-position of at least one of the coupler sections. The off position is a position where the coupler section is in an OFF state. The short circuit element may be configured to provide capaci- tive coupling between at least one conductor and the at least one housing. There may be multiple short circuit elements which may be arranged close to multiple sections of a conductor (e.g., in a U-shaped conductor or even more complex conductor). At least one further short circuit element may be arranged in parallel to at least one further straight section of a conductor, such that is in close prox- imity to the straight section in an OFF position. Any of the short circuit elements may have a dielectric surface coating, which may include an oxide layer, a pow der coating, a painted coating or a plastic material.

In another embodiment, a short circuit contact may be provided which provides a galvanic contact between the conductor and ground in the OFF position. This contact may be spring loaded. It may be configured such that it is in contact with the conductor only in the final OFF position and not during movement between the conductors. This allows the switching process without involving a galvanic contact, while the galvanic contact is only a safety feature.

In an embodiment, the coupler sections are arranged slidable sidewards against each other on a plane of at least one of the open sides. Both open sides may be on the same plane. This provides a well-defined transition between the ON- and OFF states. Basically, the coupler sections may be movable in any direction as long as the conductors are in close proximity in an ON state and distant in an OFF state.

In another embodiment, each conductor has a U-shape. Such a U-shape may in clude a first straight section and a second straight section parallel to the first straight section. The straight sections may be interconnected by a traverse sec tion. The U-shape is beneficial, as it reduces the overall length of the coupler.

The U-shape basically is a twofold bent coupler. In further embodiments, the coupler may have an unbent linear structure, or it may have multiple bends, like three or four or more bends. A higher number of bends further reduces the size which may be beneficial for lower frequencies.

In an embodiment, the coupler sections are arranged slidable perpendicular to the straight sections. Such a perpendicular movement provides a very smooth transition without having electrical field peaks which may lead to arching during switching of high power levels. In an embodiment, a sealing strip and/or a gasket may be provided at an open side of at least one coupler section, or at both coupler sections to improve the electrical contact between the coupler sections.

In an embodiment, at least one matching plate or a matching structure may be provided between a housing and a conductor of a coupler section. Such a match- ing plate may be adjustable in its distance to the conductor. It may either include a dielectric material or a conductive material which is electrically connected to the housing. Such a matching plate may be used to adjust the impedance of the conductor and/or the frequency response thereof.

In an embodiment, at least one tuning rod is provided, which may be configured to bend at least one of the conductors to modify the distance between the con ductors. This may help to optimize the structure and compensate for manufacturing tolerances. The at least one tuning rod may include a dielectric material. It may further include an outer thread which matches into a threaded hole of a housing.

Description of Drawings In the following the invention will be described by way of example, without limi tation of the general inventive concept, on examples of embodiment with refer ence to the drawings.

Figure 1 shows a coupler section of a first embodiment. Figure 2 shows a full RF connector.

Figure 3 shows a side view of a first coupler section and a second coupler section in a mated state.

Figure 4 shows a basic topology of a twofold coupler.

Figure 5 discloses a single-line coupler. Figure 6 shows a threefold coupler.

Figure 7 shows a fourfold coupler.

Figure 8 shows a second embodiment in an OFF state Figure 9 shows the second embodiment in an ON state Figure 10 shows a side view of the second embodiment.

Figure 11 shows a basic topology of a twofold coupler.

Figure 12 discloses a single-line coupler. Figure 13 shows a threefold coupler.

Figure 14 shows a fourfold coupler.

Figures 1 to 7 relate to a first embodiment. In Figure 1, a coupler section 200 is shown. In a full connector, two preferably identical sections are arranged symmetrically. Here, a first coupler section 200 is described in detail. The coupler section 200 includes a housing 210 holding a conductor 220. The conductor is in an open cavity 212 slightly recessed below the surface of the housing 210, such that it does not protrude outside of the housing. The housing may be of solid metal or any other suitable conductive ma terial, forming the cavity 212 for the conductor. In the embodiment shown in this Figure, the cavity 212 has a U-shape for holding a U-shaped conductor. This U- shape has been selected to reduce the length of the housing. Therefore, the con ductor has a first straight section 222 and a second straight section 224 coupled by a traverse section 223. The traverse section 223 may have chamfered edges to minimize reflections. The conductor 220 has a total length including the first straight section 222, traverse section 223, and second straight section 224. All sections having a total length of about ¼ of the wavelength of a signal to be transmitted. The conductor 220 has a short circuit 228 at one end to the section housing 210. At the opposing end, it has a connector section 221 which may be connected to a coaxial connector 240.

Further, matching components may be provided, like a first matching plate 231 and/or a second matching plate 233. These matching plates are optional and may be adjusted such that the coupler provides a desired impedance like 50 Ohm in a desired frequency range. The coupler may be designed for an operating frequency anywhere in a range between 10 Megahertz and 10 Gigahertz. The length of the conductor has to be matched accordingly. The relative operating bandwidth may be between 2% and 20% of the nominal bandwidth, for which the length of the conductor has been designed.

Figure 2 shows a full RF connector 100 including a first coupler section 200 and a second coupler section B00. The internal structure of the first coupler section 200 and the second coupler section 300 is the same. Therefore, they have the same cavity 212, the same conductor 220, and they may also have the same matching plates 231, 233. Both couplers may be mechanically coupled by a hous ing (not shown) or by a guiding system or by any other suitable coupling means. Here, for example, a first guide rail 170 and a second guide rail 180 are shown.

The guide rails may basically be the same. Here, the second guide rail 180 has a first guide slot 182 and a second guide slot 184. The first guide rail 170 may have the same slots. Further, the second coupler section 300 may have a pair of pins including a first guide pin 382 which may be guided by the first guide slot 182, and a second guide pin 384 which may be guided by the second guide slot 184.

This pin and slot mechanism allows sliding of the second coupler section 300 in a direction 190 towards and over the first coupler section, such that it may cover the first coupler section completely. In the configuration as shown, the first cou pler section 200 and the second coupler section 300 are distant from each other, such that there is no coupling between these coupler sections. After the second coupler section 300 has been moved in direction 190 over the first coupler sec tion 200, such that it fully covers the first coupler section 200, there is a good coupling with very low coupling losses.

As this RF connector 100 is symmetrical, either coaxial connector at the first cou- pier section 200 or the second coupler section 300 may be used as an input whereas the other may be used as an output. This configuration basically allows for two different states, an ON-state, where the coupler sections cover each other, and an OFF state, where the coupler sec tions are distant. This may be used for switching signals and/or RF power. As the coupling is without galvanic contact, switching is also without interrupting a me chanical contact. Therefore, there is no contact and no arcing. Further, the con nection has a very low passive intermodulation.

Figure 3 shows a side view of a first coupler section 200 and a second coupler section 300 in a mated state, where the coupler sections cover each other. Here it is shown that due to the symmetrical arrangement, above the location of the second coaxial connector 340 of the second coupler section 300 is the short cir cuit 228 of conductor 220 of the first coupler section 200. Further, it is shown that the conductor 220 of the first coupler section 200 is slightly distant from the conductor 320 of the second coupler section 300. Due to the recessed position of the conductors in the cavity, there remains a gap between the conductors. This results in a contactless coupling between the coupler sections. Here, the coupler sections are held by a housing 110 which may also allow sliding them against each other. The matching plates may have a support like support 234 at match ing plate 233. This support may allow height adjustment, such to move the matching plate closer or more distant to the conductor 220. Support 234 may in clude a dielectric material. It may further include a thread.

Further, at least one tuning rod may be included, like a first tuning rod 235 at the first conductor 220 and a second tuning rod 236 at the second conductor 320. There may be multiple tuning rods. A tuning rod may be configured to bend at least one of the conductors to modify the distance between the conductors.

Figure 4 schematically shows a basic topology of a twofold coupler 420, as de scribed above. In Figure 5, a single-line coupler 410 which is a modification of the twofold cou pler 420 shown above but based on the same coupling principle. Such a coupler may be used at shorter wavelengths corresponding to higher frequencies, where it is not necessary to fold the line to reduce the length of the coupler. Figure 6 shows a threefold coupler 4S0, where the line is folded into three sec tions. This allows further reduction of space, specifically for lower frequencies.

Figure 7 shows the basic concept of a fourfold coupler 440 which is similar to the couplers shown before, but with a line folded four times to further reduce size of the coupler. Figures 8 to 14 relate to a second embodiment which is very similar to the first embodiment, such that only differences are explained.

In Figure 8, the second embodiment is shown in an OFF state. In this embodi ment, a first coupler section 200, a symmetrical second coupler section 300 are held in a common housing 510. For switching between an OFF state and an ON state, at least one of the coupler sections is moved relative to the other coupler section within the common housing. In the OFF state shown in this figure, the first coupler section 200 is displaced e.g., upwards, such that the first conductor 220 of first coupler section 200 is distant form, e.g., not overlapping the second conductor 320 of second coupler section 300. Further, at least one of the con- ductors may be in proximity of a short circuit element 230, such that there is a capacitive coupling between the common housing 510 and the at least one of the conductors via the short circuit element 230. There may be multiple short circuit elements which may be arranged close to multiple sections, which may be the straight sections of a conductor in the position of an OFF state. The first conductor 220 includes first straight section 222, traverse section 223, and second straight section 224. All sections having a total length of about ¼ of the wavelength of a signal to be transmitted. The first conductor 220 has a short circuit 228 at one end to the housing 510. At the opposing end, it has a con nector section 221 which may be connected to a coaxial connector 240. The con nector section 221 may be variable in length.

The second conductor 320 includes first straight section 322, traverse section 323, and second straight section 324. All sections having a total length of about ¼ of the wavelength of a signal to be transmitted. The second conductor 320 has a short circuit 328 at one end to the housing 510. At the opposing end, it has a connector section 321 which may be connected to a coaxial connector 340. The connector section 321 may be variable in length.

In Figure 9, the second embodiment is shown in an ON state. In this state, the first coupler section 200 is in close proximity to the second coupler section 300 such that the conductors 220, 320 are facing each other.

Figure 10 shows a side view of the second embodiment. It shows the conductors 220, 320 facing each other in an ON state, resulting in a small gap between the conductors.

Figure 11 schematically shows a basic topology of a twofold coupler 520, as de scribed above. Here, for clarity only one coupler section is shown. The second coupler section is symmetrical thereto. In the following also only one coupler section is shown.

In Figure 12, a single-line coupler 510 which is a modification of the twofold cou pler 520 shown above but based on the same coupling principle. Such a coupler may be used at shorter wavelengths corresponding to higher frequencies, where it is not necessary to fold the line to reduce the length of the coupler.

Figure 13 shows a threefold coupler 530, where the line is folded into three sec tions. This allows further reduction of space, specifically for lower frequencies. Figure 14 shows the basic concept of a fourfold coupler 540 which is similar to the couplers shown before, but with a line folded four times to further reduce size of the coupler.

List of reference numerals

100 RF connector

110 housing

170 first guiderail

180 second guiderail

182 first guide slot

184 second guide slot

190 direction of movement

200 first coupler section

210 first section housing

212 cavity

220 first conductor

221 connector section

222 first straight section

223 traverse section

224 second straight section

228 short circuit

230 short circuit element

231 first matching plate

233 second matching plate

234 matching plate support

235 tuning rod at first conductor

236 tuning rod at second conductor

240 first coaxial connector

300 second coupler section

310 second section housing

320 second conductor

321 connector section

322 first straight section traverse section second straight section short circuit second coaxial connector first guide pin second guide pin single line coupler two fold coupler three fold coupler fourfold coupler common housing cavity