Patent Description:
Wideband-ferrite-couplers are used for a separation and/or combining of transmit signals and receive signals in measurement systems. There is a growing need for the measurement systems, using wideband-ferrite-couplers. The test-systems are used for performing tests on handheld mobile devices using radio communications. Various radio standards are implemented in modern communication-devices. Each of the radio standards may differ in its transmission-frequency, bandwidth, power and duplex modes. Therefore, the signal-separation and signal-combination of a coupler must have a broadband functionality, so that all the radio standards can be applied to the respective frequency bands of transmit and receive signals.

This separation of transmit and receive signals is necessary for measurements of the communications device with two or more individual modules, at least a transmitting and a receiving module. Since the send and receive operations in the mobile networks run at the same time, it must be ensured that the signals of the transmitter section of the measurement system are only passed to the device under test (DUT) and do not reach the receiving module of the DUT. The receiver section of the measurement system can otherwise be degraded in its sensitivity against the DUT signals.

For example, the document <CIT> shows a Broadband directional coupler for measuring an advancing or a returning radio-frequency signal. The directional coupler comprises a rotationally symmetric housing separated in sections and an inner conductor. The housing sections includes milled grooves to receive resistors for realizing the coupling circuit.

The document <NPL> discloses a wideband directional bridge with a range of operating frequencies from <NUM> to <NUM>. An original topology of the directional bridge was designed using a multilayer printed circuit board (PCB) technology.

The state of the art is disadvantageous since it requires a highly complex housing. Furthermore, the integration of the state of the art solution into a measuring-device is challenging.

Accordingly, the object of the invention is to provide a coupler for a separation and/or combining of transmit signals and receive signals, which has a widebandcapability without requiring a complex assembly of the coupler.

This object is solved by the features of claim <NUM> for a novel coupler. The dependent claims contain further developments.

According to one aspect of the invention, the coupler is designed in particular as a resistive coupler. All ports of the coupler are partially or completely arranged at a connector. Alternatively, these ports are partially or completely arranged in the connector. The coupler includes resistors, which are adapted to sum and/or divide the incoming and/or outgoing signal. The resistors are arranged at or in the connector. A sum port and/or at least two dividing ports are arranged on a substrate. This results in a coupler, which is easily integratable in a hardware of a measurement device. Furthermore, the installation of the coupler in a fully automated manufacturing process is enabled.

Advantageously and preferably, the resistors of the coupler are ceramic resistors. At least two resistors may comprise a common ceramic substrate. This allows for a very low complexity of the assembly of the coupler.

Further advantageously and preferably, at least one of the resistors comprises a thin-film resistive element. This results in an enhanced wideband capability of the coupler.

Advantageously and preferably, the connector of the coupler is a coaxial connector comprising a shell, a central conductor and a dielectric material. The dielectric material is configured to separate the shell from the central conductor. This allows for the use of the coupler in a front-end in a measurement device as such a coaxial connector can directly be used as an measurement port connector.

Alternatively, the shell is divided in a length direction to an isolated shell section and a shell section connected to a body of the connector whereby performing a divider section. The interruption of the shell allows an access to the central conductor of the connector.

Advantageously and preferably, at least one part of the shell is connected to ground and the other part is connected to the substrate. This allows the attachment of the sum port in the connector.

Advantageously and preferably, the common ceramic substrate carrying the at least two resistors is arranged within the divided section of the shell. This enhances the termination certainty of the resistors.

Advantageously and preferably, the shell of the connector is fixed to a reference-signal plane of the substrate, and/or a body of the connector and the shell connected to the body of the connector are fixed to a reference-signal plane of the substrate. This enhances the termination certainty of the connector.

Advantageously and preferably, the central conductor of the connector is connected to one of the dividing ports on the substrate. This allows for further accessibility of the incoming and/or outgoing signals.

Advantageously and preferably, the common ceramic substrate carrying the at least two resistors is penetrated by the central conductor of the connector.

Advantageously and preferably, at least one of the resistive elements is arranged circularly with respect to the central conductor of the connector and/or at least one of the resistive elements is formed as at least one segment of a circle with respect to the central conductor. This results in short connection traces, which increases the termination quality of the coupler and thereby increases measuring quality.

Advantageously and preferably, the conductor is connectable to an additional means, and/or the connector is placed in a recess area of the substrate. This leads to a direct contacting between the connector terminals and the conductors of the substrate and therefore the reduction of signal reflexions.

Advantageously and preferably, at least one ferrite-bead is arranged on or around the connector. This further increases the separation between the signals leading to an enhancement of the quality of measurements.

Advantageously and preferably, the substrate comprises a recess area configured to receive at least one of the at least one ferrite-beads and/or the connector comprises a circular slot adapted to integrate at least one of the at least one ferrite-beads. This assures a simplification of manufacturing of the coupler.

Advantageously and preferably, the at least one ferrite-beads is penetrated by the central conductor of the connector and by the shell conductor of the connector. This enhances the influence of the ferrite beads to the frequency response, as well as the manufacturability.

An exemplary embodiment of the invention is now further explained with respect to the drawings by way of example only, in which.

First, we show a first example of a wideband-jack-ferrite-coupler with regard to <FIG>. Along <FIG>, the construction of a second exemplary embodiment of the inventive wideband-jack-ferrite-coupler is shown. Finally, with regard to <FIG>, a detail of the inventive wideband-jack-ferrite-coupler is described. Similar entities and reference numbers in different figures have been partially omitted.

In <FIG>, a first example of a wideband-jack-ferrite-coupler <NUM> is shown. The exemplarily wideband-jack-ferrite-coupler <NUM> comprises a substrate <NUM>, a connector <NUM>, ferrite beads <NUM> and resistors <NUM>, <NUM>, <NUM>, <NUM>.

The substrate <NUM> carries all components of the exemplary wideband-jack-ferrite-coupler <NUM>. The substrate is preferably made of a material suitable for radio frequency applications. In particular, the substrate <NUM> has preferably a small dissipation factor in RF applications. There is a variety of materials available. A glass filled PTFE is a suitable material as a substrate. If the requirements on behalf of frequency are not that high, a high performance FR4 material is usable. For highest performance applications special RF materials, e.g. ROGER RO3003, are available.

Additionally the substrate <NUM> comprises the wiring structure and the sum port <NUM> and/or two dividing ports <NUM>, <NUM> on the top side of the substrate <NUM>. The ports <NUM>, <NUM>,<NUM> arranged at the connector <NUM> and are guided to the edge of the substrate <NUM>. The ports <NUM>, <NUM> at the edge of the substrate <NUM> represent the electrical interface to a measuring device. The bottom side (not shown in <FIG>) of the substrate <NUM> comprises a conductive layer which is connected to a reference signal plane. Such a reference signal plane can have ground potential. Therefore, the wideband-jack-ferrite-coupler <NUM> is constructed to be placed on a prepared area of a printed circuit board of the measuring device.

The connector <NUM> in the exemplary wideband-jack-ferrite-coupler <NUM> is an edge mounted coaxial connector. This connector <NUM> can be e.g. MMCX, SMA, SMB, SMC, BNC, TNC or N connectors. The invention is not limited to the listed connector types. The connector <NUM> further comprises the ferrite-beads <NUM>. This configuration will be lined out in a following section concerning <FIG>.

The resistors <NUM>, <NUM>, <NUM>, <NUM> are placed on the side of the substrate <NUM> comprising the wiring structure. Preferably, the resistors <NUM>, <NUM>, <NUM>, <NUM> are configured as a Wheatstone-bridge. A first resistor <NUM> is connected with its first connection to the dividing port <NUM> and to the sum port <NUM>. The second connection of the first resistor <NUM> is connected to a first connection of the second resistor <NUM> and the second dividing port <NUM>.

This forms a first branch of the Wheatstone-bridge. The second branch of the Wheatstone-bridge is formed by a third resistor <NUM> and a fourth resistor <NUM> in series configuration in combination with the impedance of a device connected to the sum port <NUM>. The first connection of the third resistor <NUM> is connected to the reference signal plane. The second connection of the third resistor <NUM> is connected to a first connection of the fourth resistor <NUM> and the shell of the connector <NUM>. The ferrite-beads <NUM> placed on the shell of the connector <NUM> form a balun for transforming the asymmetrical signal of the dividing port <NUM> into a symmetrical signal usable for the bridge.

The resistors <NUM>, <NUM>, <NUM>, <NUM> are ceramic-chip-resistor. In high precision applications for RF-measurements these resistors <NUM>, <NUM>, <NUM>, <NUM> have a thin film resistive element. Thin-film resistive elements are characterized by a low noise, a low temperature dependency and low resistance tolerance. Alternatively, thick-film resistive elements can be used for cost sensitive applications. Thick-film resistors have good performance characteristics which are suitable for many measurement applications.

Besides using ceramic-chip-resistors, a direct application of the resistive element on the substrate <NUM> can be used. The direct applied resistive elements is able to further enhance the termination quality of the wideband-jack-ferrite-coupler.

A bridge arrangement as described above has a good decoupling characteristics for both of the dividing ports <NUM>, <NUM>. Additionally, the attenuation between the sum port <NUM> and one of the dividing ports <NUM>, <NUM> preferably is about <NUM> dB.

<FIG> shows a sectional top view of the first example of the wideband-jack-ferrite-coupler <NUM>. The sectional view in particular makes the construction of the connector <NUM> in combination with the ferrite-beads <NUM> visible. The connector <NUM> comprises a body <NUM>. The body <NUM> has a circular slot <NUM>. The circular slot <NUM> is dimensioned in a way that the ferrite-beads <NUM> can be integrated into the connector <NUM>. It is noted that a shell <NUM> is formed at the inner side of the circular slot <NUM>. A central conductor <NUM> penetrates die centrum of the connector <NUM>. This central conductor <NUM> is separated from the shell <NUM> as well as from the body <NUM> by an insulator <NUM>. This insulator <NUM> is dimensioned so that the connector <NUM> comprises a good impedance matching.

The ferrite-beads <NUM> are fixed in the slot of the connector <NUM> preferably by using an adhesive. The adhesive can be a resin, an epoxy resin, a cyan-acrylate adhesive or any adhesive with suitable electrical characteristics. Beside this, the ferrite-beads <NUM> can be formed directly into the slot of the connector <NUM> using the sintering process of ferrite production.

The perspective view of the first example of the wideband-jack-ferrite-coupler <NUM> is shown in <FIG>. The perspective view shows the integration of the connector <NUM> into the substrate <NUM>. The connector <NUM> is placed in a recess area of the substrate <NUM>. Further, it can be seen that the ferrite-beads <NUM> are also integrated into the substrate <NUM>. Additionally, the ferrite-beads <NUM> are placed in a circular slot of the connector <NUM>. The central conductor <NUM> is attached to the sum port <NUM>.

<FIG> shows a side view of the wideband-jack-ferrite-coupler <NUM>. Here it can be seen in more detail, that the connector <NUM> include the ferrite-beads <NUM> whereby penetrating the substrate <NUM>. The central conductor <NUM> is connected to the dividing structure of the substrate <NUM> at the top side. The flat connection of the central conductor <NUM> reduces the reflection on the connection point. Advantageously, the bandwidth of the coupler is increased.

<FIG> shows are sectional side view of the wideband-jack-ferrite-coupler <NUM>. In this view it more obvious how the connector <NUM> is integrated into the substrate <NUM>. The central conductor <NUM> reaches from the dividing port <NUM> to the sum port <NUM>. The shell <NUM>, the dielectric material <NUM> and the central conductor <NUM> are assembled as a coaxial line. The ferrite-beads <NUM> are fixed on this coaxial line. This configuration leads to a balun circuit. This balun is responsible for a conversion of a symmetrical signal into a unsymmetrical signal and of a unsymmetrical signal into a symmetrical signal. This is an essential part in a measuring bridge for the wideband-jack-ferrite-coupler <NUM>. One of the dividing ports, here dividing ports <NUM>, is not related to a reference potential. Therefore, it has to be converted into a signal free of reference potential.

<FIG> and <FIG> shows the top view a second exemplary embodiment of the inventive wideband-jack-ferrite-coupler <NUM>. For simplifying purposes <FIG> and <FIG> are discussed together. The functionality of the wideband-jack-ferrite-coupler <NUM> is basically the same as the wideband-jack-ferrite-coupler <NUM> described for the first example. The exemplarily wideband-jack-ferrite-coupler <NUM> comprises a substrate <NUM>, a connector <NUM>, ferrite beads <NUM>, resistors <NUM>, <NUM> and a common ceramic substrate <NUM>.

The substrate <NUM> carries all components of the exemplary wideband-jack-ferrite-coupler <NUM>. The substrate <NUM> is preferably made of a suitable material having a small dissipation factor in RF applications. A suitable material is e.g. a glass filled PTFE, a high performance FR4 material or ROGER RO3003.

A wiring structure and the sum port <NUM> and/or two dividing ports <NUM>, <NUM> are applied on the top side of the substrate <NUM>. The ports <NUM>, <NUM> arranged at the substrate <NUM> are guided to the edge of the substrate <NUM>. The bottom side of the substrate <NUM> comprises a conductive layer which is connected to a reference signal plane.

The connector <NUM> in the exemplary wideband-jack-ferrite-coupler <NUM> is an edge mounted coaxial connector. The connector <NUM> has a shell which preferably is divided in a length direction to an isolated shell section <NUM> and a shell section connected to a body <NUM> of the connector <NUM>. The shell of the connector connected to a body <NUM> also is connected to a reference-signal plane of the substrate <NUM>. The reference-signal plane is connected to a reference potential of the signals. Preferably, the reference-signal plane has a ground potential. The body <NUM> of the connector <NUM> and the shell connected to the body <NUM> of the connector <NUM> are also fixed to a reference-signal plane of the substrate <NUM>.

A common ceramic substrate <NUM> is arranged at the isolated section of the shell <NUM>. The divided section of the shell is in between the isolated section of the shell <NUM> and section of the shell connected to the body of the connector <NUM>. The common ceramic substrate <NUM> is penetrated by the central conductor <NUM>. Preferably at least two resistors are integrated on the common ceramic substrate <NUM>. The resistors <NUM>, <NUM> are placed on the top side of the substrate <NUM>.

Preferably, the resistors <NUM>, <NUM> in combination with the at least two resistors of the common ceramic substrate <NUM> are configured as a Wheatstone-bridge. The resistors placed on the common ceramic substrate <NUM> form a first branch of a Wheatstone-bridge. The second branch of the Wheatstone-bridge is formed by a third resistor <NUM> and a fourth resistor <NUM> in series configuration in combination with the impedance of a device connected to the sum port <NUM>. The first connection of the third resistor <NUM> is connected to the reference signal plane. The second connection of the third resistor <NUM> is connected to a first connection of the fourth resistor <NUM> and the isolate section of the shell <NUM> of the connector <NUM>.

A first dielectric element <NUM> is applied between the central conductor <NUM> and the isolated section of the shell <NUM>. A second dielectric element <NUM> separates the central conductor from the shell connected to the body of the connector <NUM>. The dimensions of the dielectric elements are selected such that the resulting coaxial structure has a desired line-impedance of for example 50Ω.

The ferrite-beads <NUM> are placed on the isolated section of the shell <NUM>. This construction forms a balun for transforming the asymmetrical signal of the dividing port <NUM> into a symmetrical signal usable for the bridge.

<FIG> shows the perspective view of the second exemplary embodiment of the inventive wideband-jack-ferrite-coupler <NUM>. The perspective view shows the integration of the connector <NUM> into the substrate <NUM> comprising the ferrite-beads <NUM> and the common ceramic substrate <NUM>. This connector assembly is placed in a recess area of the substrate <NUM>.

<FIG> shows a side view of the wideband-jack-ferrite-coupler <NUM>. Here it can be seen in more detail that the connector <NUM> including the ferrite-beads <NUM> on the isolated section of the connector's shell <NUM> is penetrating the substrate <NUM>. The central conductor <NUM> is connected to the dividing port <NUM> on the substrate <NUM> at the top side in a flat manner. The flat connection of the central conductor <NUM> reduces the reflection on the connection point. Advantageously, the bandwidth of the coupler is increased.

<FIG> shows a side view and <FIG> shows are sectional side view of the wideband-jack-ferrite-coupler <NUM>. Herein, it is more obvious how the connector <NUM> is integrated into the substrate <NUM>. The central conductor <NUM> reaches from the sum port <NUM> to the dividing port <NUM>. The shell is divided into an isolated section of the shell <NUM> and a section connected to the connector <NUM>. A first portion of the dielectric material <NUM> is placed beneath the isolated section of the shell <NUM>. A second portion of the dielectric material <NUM> is placed beneath the section of the shell connected to the body of the connector <NUM>. The gap between the two portions of the dielectric material <NUM>, <NUM> corresponds to the distance between the two shell portions of the connector <NUM>. Beside the electrical separation of the shells <NUM>, <NUM> the gap is intended to integrate the common ceramic substrate <NUM>.

<FIG> allows a closer look at the common ceramic substrate <NUM> and its application to the wideband-jack-ferrite-coupler <NUM>. Therefore, <FIG> depicts a further sectional view of the wideband-jack-ferrite-coupler <NUM>. In <FIG>, the cutting plane is the bottom side of the common ceramic substrate <NUM>. The bottom side of the common ceramic substrate <NUM> is plated with a conductive layer <NUM>. This conductive layer <NUM> is made of cooper, gold plated cooper or silver plated cooper. The selection of materials is not restricted to the listed ones. The conductive layer is isolated from the shell <NUM> of the connector. The area in proximity to the central conductor <NUM> is also isolated. Additionally and preferably, the common ceramic substrate <NUM> comprises vias <NUM> for a connection of the bottom side conductive layer <NUM> with a top side conductor (not shown in <FIG>). This construction allows a shielding of the resistive elements from the influence of the electromagnetic fields within the coaxial connector.

<FIG> shows a detailed sectional perspective view of the resistive elements on the common ceramic substrate <NUM>. Therefore, the cutting plane used in <FIG> is moved to the resistive elements <NUM> and <NUM> of the common ceramic substrate <NUM>. The common ceramic substrate <NUM> comprises a first resistive element <NUM>, a second resistive element <NUM>, vias <NUM> and a wiring structure. The first resistive element <NUM> is arranged circularly with respect to the central conductor <NUM> of the connector as a ring. The inner diameter of the first resistive element <NUM> starts from the central conductor <NUM> and the outer diameter is in proximity to a wiring ring connecting the vias <NUM>. The first resistive element is connected with its first terminal to the central conductor of the connector at its inner diameter. The second terminal of the first resistive <NUM> element is connected to the wiring ring connecting the vias <NUM>. The second resistive element <NUM> is a segmented ring arranged circularly with respect to the central conductor <NUM> of the connector.

The second resistive element <NUM> starts with its inner diameter from the wiring ring connecting the vias <NUM> and ends in a proximity to the outer diameter of the common ceramic substrate <NUM>. The second resistive element <NUM> is connected with a first terminal to the wiring ring connecting the vias <NUM>. The second terminal of the second resistive element is the outer diameter of the resistive element <NUM> and is connected with the isolated part of the shell. The ring connecting the vias <NUM> is connected to land-patterns <NUM>. These land-patterns <NUM> are placed within the isolated parts of the segmented second resistive element <NUM>. In connection for the central point the voltage divider comprising the first resistive element <NUM> and the second resistive element <NUM> is made contactable to the substrate <NUM> with these land-patterns <NUM>.

These resistive elements <NUM>, <NUM> preferably consist of a thin-film resistive element. Such a thin-film resistive element <NUM>, <NUM> is applied by a sputtering process followed by laser trimming.

Claim 1:
A coupler (<NUM>,<NUM>), in particular a resistive coupler,
wherein a port (<NUM>, <NUM>) comprises a connector (<NUM>, <NUM>),
wherein resistors (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) configured as a Wheatstone-bridge, which are adapted to sum or divide incoming or outgoing signals, are arranged at or in the connector (<NUM>, <NUM>),
wherein a sum port (<NUM>, <NUM>) and/or at least two dividing ports (<NUM>, <NUM>, <NUM>, <NUM>) are arranged on a substrate (<NUM>, <NUM>),
at least two resistors are formed on a ceramic substrate (<NUM>), wherein the resistors placed on the ceramic substrate (<NUM>) form a first branch of a Wheatstone-bridge,
wherein a second branch of the Wheatstone-bridge is formed by a third and a fourth one of the resistors (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) in series configuration in combination with the impedance of a device connectable to the sum port (<NUM>),
wherein the connector (<NUM>, <NUM>) is a coaxial connector comprising a shell (<NUM>, <NUM>, <NUM>), a central conductor (<NUM>, <NUM>) and a dielectric material (<NUM>, <NUM>, <NUM>) configured to separate the shell (<NUM>, <NUM>, <NUM>) from the central conductor(<NUM>, <NUM>),
characterised in that
the shell (<NUM>, <NUM>) is divided in a length direction to an isolated shell (<NUM>) section and a shell section connected to a body of the connector (<NUM>),
wherein the interruption of the shell (<NUM>, <NUM>) configured to allow an
access to the central conductor (<NUM>, <NUM>) of the connector (<NUM>), and
wherein at least one ferrite-bead (<NUM>, <NUM>) is arranged on or around the connector (<NUM>, <NUM>) on the isolated section of the shell (<NUM>) forming a balun for transforming an asymmetrical signal of a dividing port (<NUM>, <NUM>, <NUM>, <NUM>) into a symmetrical signal.