Broadband terahertz directional coupler

Abstract

The invention relates to a multi-port directional coupler (100) for broadband communication applications, comprising: a half-mirror (110), comprising: a first dielectric slab (101) and a second dielectric slab (102); wherein the first dielectric slab (101) and the second dielectric slab (102) are arranged adjacently in a first plane, and wherein the first dielectric slab (101) and the second dielectric slab (102) each comprise at least one port.

Description

[0001] Broadband terahertz directional coupler

[0002] Background

[0003] The present invention relates to a multi-port directional coupler for broadband communication applications and to devices comprising a multi-port directional coupler.

[0004] Multi-port directional couplers are a key component in many radio frequency (RF) systems such as communication transceivers, and instrumentation equipment, e.g. sensors, vector signal analyzers, etc.

[0005] For example, when inserted between two radiofrequency devices A and B, a multi-port directional coupler allows for an independent and simultaneous sampling and monitoring of the signals going from A to B and from B to A.

[0006] A drawback of current multi-port directional couplers is that they are frequency limited by their design and their manufacturing technology and also can suffer from significant insertion and coupling losses.

[0007] Problem

[0008] It is therefore the object of the present invention to provide an improved multi-port directional coupler for broadband communication applications and devices.

[0009] In particular, it is an object of the present invention to improve the bandwidth and frequency range of a multi-port directional coupler.

[0010] It is further an object of the present invention to provide a more efficient multi-port directional coupler for broadband communications with reduced insertion and coupling losses. Furthermore, it is an object of the present invention to reduce manufacturing costs of multi-port directional couplers.

[0011] Solution

[0012] According to the present invention, said objects are achieved by the subject-matter of the independent claim.

[0013] Advantageous embodiments and further developments are the subject-matter of the dependent claims. An exemplary multi-port directional coupler for broadband communication applications can comprise a half-mirror, wherein said half-mirror can comprise a first dielectric slab and a second dielectric slab and wherein the first dielectric slab and the second dielectric slab can be arranged adjacently in a first plane, and wherein the first dielectric slab and the second dielectric slab each can comprise at least one port.

[0014] Herein, the term half-mirror or dielectric mirror can inter alia be understood as a component of the multi-port directional coupler that reflects part of the incoming signal, e.g. a radio frequency (RF) signal, and at the same time is transmissive to the remaining part of the incoming signal, e.g. an RF signal, and wherein the ratio of the reflected part to the transmitted part of the incoming signal can be any ratio greater than 0, e.g. the ratio of the reflected part and the transmitted part of the incoming signal can be 1 or less than 1 or greater than 1 .

[0015] The term dielectric slab can inter alia refer to a planar disc, e.g. a rectangular shaped disc, of dielectric material. However, other non-rectangular shapes for a dielectric slab of a herein exemplary described multi-port directional coupler are conceivable too. Furthermore, a dielectric slab of the herein exemplary described multi-port directional coupler may comprise a single layer or multiple layers of the same dielectric material or multiple layers of different dielectric materials.

[0016] The term port can refer to a component that can receive and transmit electromagnetic signals, e.g. RF signals.

[0017] The term broadband communications herein may inter alia also be understood as comprising ultra-wideband communications, wherein for example the bandwidth over which communication signals can be transmitted is at least 500 MHz or larger.

[0018] The term broadband communication applications may inter alia refer to instrumentation, sensing and communications applications. More specifically, said broadband communication applications may refer to 6G / 7G communications, millimeter and sub-millimeter frequency transceivers, vector network analyzers, spectroscopy sensing and image sensing applications, radio frequency (RF) characterization and measurement instrumentation systems, test and measurement equipment, data and inspection networks.

[0019] The above and herein exemplary described multi-port directional coupler provides a simplified and robust design that allows easier and more cost-efficient manufacturing of multi-port directional couplers. Furthermore, the above and herein exemplary described multi-port directional coupler is more efficient than current multi-port directional couplers and has lower insertion and coupling losses as compared to common multi-port directional couplers.

[0020] Moreover, the above and herein exemplary described multi-port directional coupler inter alia provides ultra-wideband bandwidth for frequency bands that cover coaxial connector standards, e.g. up to 110 GHz or up to 220 GHz, and frequency bands that cover rectangular waveguide standards, e.g. WR08, from 90 to 140 GHz, and even for frequencies up to 400 GHz and above.

[0021] For example, the above and herein exemplary described multi-port directional coupler can have a lower cut-off frequency of 65 GHz or less and a higher cut-off frequency of up to 300 GHz or higher.

[0022] For example, it is possible that the operating frequency of the above and herein exemplary described multi-port directional coupler can lie in the range of 1 GHz to 1 THz.

[0023] The above and herein exemplary described multi-port directional coupler can further comprise a first rod arranged in a second plane and a second rod arranged in a third plane, wherein the first plane and the second plane and the third plane can be parallel to each other and wherein the first plane can lie between the second plane and the third plane.

[0024] In other words, the first plane, the second plane and the third plane can all be different to each other and can be parallel to each other. The first plane can have the same distance, e.g. the same vertical distance, from the second plane and from the third plane.

[0025] A / the longitudinal axis of the first rod and a / the longitudinal axis of the second rod can be arranged parallel and opposite to each other.

[0026] Furthermore, said longitudinal axes of the first rod and the second rod can be arranged parallel to and opposite to a longitudinal axis lying between a first side of the first dielectric slab and a first side of the second dielectric slab.

[0027] Said first rod and said second rod can be arranged such as being distanced from the first and second dielectric slab.

[0028] However, it is also possible that said first rod and said second rod can at least partially be in physical contact with at least one of the dielectric slabs of the multi-port directional coupler.

[0029] The permittivity of the first dielectric slab of the above and herein exemplary described multi-port directional coupler can be equal to the permittivity of the second dielectric slab. Such an exemplary configuration of the multi-port directional coupler or of the half-mirror may also be referred to herein as fundamentally broadband half-mirror configuration.

[0030] The ratio of the reflected part of a signal, e.g. incoming signal of the multi-port directional coupler, to the transmitted part of the signal can inter alia be set or controlled by a possible gap between the dielectric slabs, and / or the thickness of the dielectric slabs, and / or the shape and geometry of the possible rods, e.g. the length or radius of the rods, and / or by the spatial arrangement / ori- entation between the possible rods and the dielectric slabs, e.g. the distance between the possible rods and the dielectric slabs.

[0031] In an exemplary configuration the ratio of the reflected part of the signal to the transmitted part of the signal can be 50% : 50%, i.e. 1.

[0032] However, the ratio of the reflected part of the signal to the transmitted part of the signal can also be different to 1 .

[0033] Alternatively, the permittivity of the first dielectric slab can be different from the permittivity of the second dielectric slab. For example, the first dielectric slab and the second dielectric slab may comprise different dielectric materials with different permittivities and / or may comprise dielectric materials with different effective permittivities, e.g. dielectric slab materials with different structures, e.g. different porosities.

[0034] Such an exemplary configuration of the multi-port directional coupler or of the half-mirror may also be referred to herein as a Snell’s law half-mirror configuration.

[0035] Herein, the term permittivity inter alia can be understood as a measure of the electric polarizability of a dielectric material. The term permittivity can inter alia be denoted by the Greek letter E (Epsilon) in the following.

[0036] Furthermore, the term permittivity can inter alia refer to absolute permittivity or to relative permittivity, wherein relative permittivity can be defined as the ratio of the relative permittivity to the permittivity of vacuum, denoted as so, and which is defined as being exactly 1 , i.e. unity.

[0037] Having the permittivity of the first dielectric slab being the same or different than the permittivity of the second dielectric slab can limit or confine the propagation of the signal to a two-dimensional plane, e.g. a plane inside the dielectric slab. This can inter alia reduce insertion losses between ports of the multi-port directional coupler, since in said exemplary permittivity configurations, the insertion losses are only proportional to the distance between ports instead of being proportional to the square of the distance as would be the case if the propagation of the signal would be a three-dimensional free-space propagation.

[0038] The permittivities of the dielectric slabs for any configuration of the multi-port directional coupler can be larger than 1 . More specifically, the permittivities of the dielectric slabs for a herein exemplary described multi-port directional coupler can lie between 1 and 8. However, permittivities larger than 8 are possible too.

[0039] The dielectric slabs may for example comprise silicon / silicone materials. The use of silicon / sili- cone materials can facilitate the manufacturing process of the multi-port directional coupler.

[0040] However, other materials, such as semiconductor materials or plastic materials are conceivable too.

[0041] The above and herein exemplary described multi-port directional coupler can have a thickness that is less than the operating wavelength A of the specific broadband communication application.

[0042] The thickness can inter alia be set to boost performance in specific bands or sub-bands of the multi-port directional coupler.

[0043] For example, in any configuration of the multi-port directional coupler, e.g. in said fundamentally broadband half-mirror configuration or in said Snell’s law half-mirror configuration, the thickness of the dielectric slabs can be equal to or less than 500 pm, e.g. in the range of 100 pm to 250 pm.

[0044] Furthermore, the thickness of the dielectric slabs could be chosen in dependence of the permittivities of the dielectric slabs, wherein for smaller permittivities, the thickness of the dielectric slabs is increased and wherein for larger / higher permittivities, the thickness of the dielectric slabs is decreased.

[0045] For example, when using dielectric slabs with silicon / silicone materials and having a thickness of 500 pm, a good performance of the multi-port directional coupler can be obtained from operating frequencies from 60 GHz to 600 GHz. If, for example, higher operating frequencies are desired, the dielectric slabs may have a thickness in the range of 100 pm to 250 pm.

[0046] As previously indicated, the above and herein exemplary described multi-port directional coupler can in any configuration, e.g. in said fundamentally broadband half-mirror configuration or in said Snell’s law half-mirror configuration, comprise: • a first rod arranged in a second plane and a second rod arranged in a third plane, wherein the first plane (the plane in which the first dielectric slab and the second dielectric slab can be arranged adjacently) and the second plane and the third plane can be parallel to each other (or substantially parallel to each other) and wherein the first plane can lie between the second and third plane.

[0047] Stated differently, the presence of said possible first rod / first dowel and said possible second rod / second dowel is entirely optional for any configuration of the multi-port directional coupler, i.e. in particular the presence of said possible rods / dowels is optional for said fundamentally broadband half-mirror configuration and for said Snell’s law half-mirror configuration. However, the optional rods / dowels merely can serve to boost the performance of the multi-port directional coupler at lower frequencies, e.g. frequencies lower than 200 GHz.

[0048] Furthermore, a / the longitudinal axis of the first rod and a / the longitudinal axis of the second rod can be arranged parallel and opposite to each other.

[0049] In addition, said longitudinal axes of the first rod and the second rod can be arranged parallel to and opposite to a longitudinal axis lying between a first side of the first dielectric slab and a first side of the second dielectric slab.

[0050] The above and herein exemplary described multi-port directional coupler may comprise a gap, e.g. an air gap, that can be formed or provided between a / the first side of the first dielectric slab and a / the first side of the second dielectric slab. Furthermore, the longitudinal axes of the first rod and the second rod can be arranged parallel to and opposite to a longitudinal axis lying in the gap.

[0051] Said first sides of the dielectric slabs can be lateral sides of the dielectric slabs that are opposite to each other and the first side of the first dielectric slab can be arranged adjacently to the first side of the second dielectric slab, wherein both dielectric slabs lie in the same plane, i.e. in said first plane of the multi-port directional coupler.

[0052] Said optional and exemplary gap between said in the first plane arranged adjacently dielectric slabs can, in addition to the permittivities of the dielectric slabs, further facilitate controlling the ratio of the reflected part of a signal, e.g. an / the incoming signal of the multi-port directional coupler, to the transmitted part of the signal.

[0053] For completeness it is noted that said possible gap, e.g. an air gap, that can be formed or provided between a / the first side of the first dielectric slab and a / the first side of the second dielectric slab can be present in all above and herein described configurations of the multi-port directional coupler, regardless of the presence of rods.

[0054] In particular, said possible gap, e.g. an air gap, that can be formed between a / the first side of the first dielectric slab and a / the first side of the second dielectric slab can be present in said exemplary fundamentally broadband half-mirror configurations or in said exemplary Snell’s law halfmirror configurations of a possible multi-port directional coupler.

[0055] Furthermore, said possible gap, e.g. air gap, can interrupt well-confined high frequencies.

[0056] Herein, the term well-confined high frequencies can be understood as referring to frequencies for which most, e.g. the majority, of the power of an / the electromagnetic wave signal, e.g. an incoming signal, e.g. an RF signal, resides / propagates inside a / the dielectric slab of the multi-port directional coupler. An exemplary high frequency may refer to a frequency greater than 200 GHz.

[0057] The term interrupt can inter alia refer to the process of at least partially reflecting an / the electromagnetic wave signal, e.g. an incoming signal, e.g. an RF signal.

[0058] Said possible gap can inter alia facilitate the reflection, e.g. a / the partial reflection, of the electromagnetic wave signal at said possible gap or interface between the dielectric slab.

[0059] More specifically, said possible gap can be electrically small, which can ensure a frequency-in- dependent response, in particular for said high frequencies.

[0060] Herein, the term electrically small gap can be understood as a gap with a width of less than the operating wavelength A of a given specific broadband communication application of the multi-port directional coupler. More specifically, said possible gap, e.g. air gap, can have a width of less than A / 4, or less than A / 5 or less than A / 10.

[0061] A further exemplary configuration of the multi-port directional coupler or half-mirror can comprise a third dielectric slab that is arranged such that it passes through said possible gap between a / the first side of the first dielectric slab and a / the first side of the second dielectric slab. Furthermore, said possible third dielectric slab can fully or at least partially fill said possible gap between the first dielectric slab and the second dielectric slab.

[0062] Herein, the expression “passing through” can refer to the case of one part, e.g. a first half, of the third dielectric slab being located on one side, e.g. above or lateral, of said first plane in which the first dielectric slab and the second dielectric slab are arranged and one part, e.g. a second half, of the third dielectric slab being located on another side, e.g. below or lateral, of said first plane. Furthermore, said third dielectric slab can have an orientation that is perpendicular / orthogonal to the first dielectric slab and the second dielectric slab of the multi-port directional coupler.

[0063] For example, assuming an exemplary orthogonal coordinate system with orthogonal axes X, Y, Z, such as denoted by reference numeral 109 in the figures of this application and exemplary placing the origin of said orthogonal coordinate system at the center of a herein described multiport directional coupler, said possible third dielectric slab may lie in the YZ-plane and the first dielectric slab and the second dielectric slab can lie in the YX-plane, as exemplary illustrated in Fig. 2d.

[0064] Stated differently, the cross section of a multi-port directional coupler having three dielectric slabs can be cross-like.

[0065] Said possible, exemplary third dielectric slab may be a lossy dielectric slab. More specifically, said third dielectric may have a dielectric conductivity o less 10000 S / m (siemens per meter), e.g. the dielectric conductivity o can lie between 0 S / m and 10000 S / m.

[0066] Similar to the first dielectric slab and the second dielectric slab, said possible third dielectric slab can have a rectangular shape.

[0067] Said exemplary possible three-slab half-mirror configuration may also be referred to as a possible lossy-slab configuration of the multi-port directional coupler.

[0068] This exemplary possible three-slab half-mirror configuration, like also all other herein described half-mirror configurations / multi-port directional coupler configurations, also provides ultra-wide- band communication capabilities, but its performance is even more frequency-independent.

[0069] Hence, this possible three-slab half-mirror configuration may be of particular interest to communications and / or sensing and / or instrumentation applications since the need for equalization can be mitigated. However, it is noted that also all of the above and herein described exemplary fundamentally broadband half-mirror configurations or Snell’s law half-mirror configurations of the multi-port directional coupler are suited for said applications.

[0070] It is further noted that in all above and herein described exemplary described half-mirror configu- rations / multi-port directional coupler configurations, e.g. in the three-slab half-mirror configurations or in the fundamentally broadband half-mirror configurations or in the Snell’s law half-mirror configurations, the first and second dielectric slabs can have dielectric conductivity o that is as low as possible, preferably with a dielectric conductivity o of 0 S / m or close to 0 S / m, i.e. the first and second dielectric slabs can preferably have a high resistivity p, which is the reciprocal of the conductivity o.

[0071] For example, the dielectric slabs may comprise or may be made of silicon / silicone materials with low dielectric conductivity o, e.g. with a dielectric conductivity o of 0 S / m or close to 0 S / m.

[0072] This can facilitate reducing signal losses for the signals traveling / propagating through the first and second dielectric slabs of the multi-port directional coupler.

[0073] For completeness it is further noted that, aside from the possible three-slab half-mirror configuration, it is possible that in all of the above and herein described exemplary fundamentally broadband half-mirror configurations or Snell’s law half-mirror configurations of the multi-port directional coupler, and regardless of the presence of rods, no gap or nearly no gap is formed at an interface between a / the first side of the first dielectric slab and a / the first side of the second dielectric slab.

[0074] For example, it is possible that no gap or nearly no gap is formed at an interface between a / the first side of the first dielectric slab and a / the first side of the second dielectric slab and wherein the longitudinal axes of the first rod and the second rod are arranged parallel to and opposite to a longitudinal axis lying along the interface between the first side of the first dielectric slab and the first side of the second dielectric slab.

[0075] Equally, for example, it is possible that no gap or nearly no gap is formed at an interface between a / the first side of the first dielectric slab and a / the first side of the second dielectric slab without a / the multi-port directional coupler comprising any rods.

[0076] As indicated above, it is also possible that a possible gap between the first side of the first dielectric slab and the first side of the second dielectric slab can be filled fully or at least partially by a third dielectric slab that passed through said gap.

[0077] Herein, the expression nearly no gap can inter alia be understood as no gap within manufacturing tolerances.

[0078] Herein, the term interface can inter alia be understood as the region between the opposing first sides of the in the first plane adjacently arranged dielectric slabs. More specifically, the term interface can inter alia be understood as the contact region or contact surface between the first side of the first dielectric slab and the first side of the second dielectric slab, wherein the first side of the first dielectric slab and the first side of the second dielectric slab can be in direct physical contact. In such an exemplary gapless multi-port directional coupler, i.e. a multi-port directional coupler having no gap between directly opposing sides of the dielectric slabs that are adjacently arranged in said first plane, the permittivity of the first dielectric slab can be different from the permittivity of the second dielectric slab.

[0079] This can facilitate controlling the ratio of the reflected part of a signal, e.g. incoming signal of the multi-port directional coupler, to the transmitted part of the signal.

[0080] As further explained below, this can further facilitate a multiplexer (mux) functionality and / or a / the demultiplexer (demux) functionality of the multi-port directional coupler.

[0081] The previously described possible exemplary first rod and second rod of a multi-port directional coupler can have a cylindrical shape. However, other shapes, e.g. having non-circular cross sections, are conceivable too.

[0082] The possible two rods can have the same shape and can have the same spatial dimensions and can comprise the same materials.

[0083] However, it is also possible that the possible two rods can have different shapes and / or different spatial dimensions and / or can comprise different materials.

[0084] The term rod may inter alia also be understood as referring to a dowel or bar.

[0085] The material of the first rod and the material of the second rod can comprise a conductive material, e.g. a metallic material.

[0086] Said possible rods or dowels or bars can inter alia be used for boosting the reflection of a signal at lower frequencies.

[0087] Furthermore, said possible rods or dowels or bars can inter alia interrupt poorly-confined low frequencies.

[0088] Herein, the term poorly-confined low frequencies can be understood as referring to frequencies for which a significant fraction, e.g. the majority, of the power an / the electromagnetic wave signal, e.g. an incoming signal, e.g. an RF signal, resides / propagates outside of / externally to a / the dielectric slab of the multi-port directional coupler. An exemplary low frequency may refer to a frequency lower than 200 GHz.

[0089] As previously indicated, the term interrupt can inter alia refer to the process of at least partially reflecting an / the electromagnetic wave signal, e.g. an incoming signal, e.g. an RF signal. Stated differently, the term interrupt may be understood as referring to the splitting of the power of the electromagnetic wave signal.

[0090] Said possible rods or dowels or bars can facilitate the reflection, e.g. a / the partial reflection, of the electromagnetic wave signal external to / outside of the dielectric slab of the multi-port directional coupler, in particular for said poorly-confined low frequencies.

[0091] Furthermore, said possible rods or dowels or bars can improve the frequency response performance of the multi-port directional coupler, in particular improving an ultra-broadband frequencyindependent response of the multi-port directional coupler.

[0092] The possible rods or dowels or bars can comprise a stiff, non-flexible material and can be low- loss materials, e.g. metals such as aluminium or brass.

[0093] This can inter alia avoid the occurrence of unwanted vibrations and thereby avoid unwanted mi- crophonic effects that can be detrimental to the performance of the multi-port directional coupler.

[0094] The above and herein exemplary described multi-port directional coupler can be configured such that the first dielectric slab and the second dielectric slab are both planar slabs and both have a rectangular shape.

[0095] The above and herein exemplary described multi-port directional coupler can have two orthogonal symmetry axes. For example, a first symmetry axis can lie in the first plane and can coincide with an axis of an / the interface or with the / a gap between the first dielectric slab and the second dielectric slab, and with the second symmetry axis being orthogonal to the first symmetry axis.

[0096] For example, assuming an exemplary orthogonal coordinate system with orthogonal axes X,Y,Z, such as denoted by reference numeral 109 in the figures of this application and exemplary placing the origin of said orthogonal coordinate system at the center of a herein described multi-port directional coupler, the XY-plane may be a symmetry plane. Also the XZ-plane and / or the ZY- plane could be symmetry planes of a herein described multi-port directional coupler.

[0097] Such a possible symmetry can avoid performance losses due to avoidance of unwanted higher- order mode excitations in vertical planes inside the dielectric slabs. Furthermore, said possible symmetry can facilitate and simplify manufacturing of the multi-port directional coupler.

[0098] The above and herein exemplary described multi-port directional coupler can be configured as a four-port directional coupler comprising four ports, wherein each of the two adjacent dielectric slabs, i.e. the first dielectric slab and the second dielectric slab, can comprise two ports. In such an exemplary four-port configuration, a first port can be configured as input port, a second port can be configured as transmitted port, a third port can be configured as coupled port and a fourth port can be configured as isolated port.

[0099] However, it is also possible that the multi-port directional coupler can have more than four ports.

[0100] Also it is possible that the multi-port directional coupler may only have three ports, wherein a first port can be configured as input port, a second port can be configured as transmitted port, a third port can be configured as coupled port and wherein no port is configured as isolated port.

[0101] Furthermore, it is possible that the above and herein exemplary described multi-port directional coupler has four or more ports, wherein no port is configured as isolated port, but wherein, aside from having a port being configured as input port and another port being configured as transmitted port, the multi-port directional coupler may comprise multiple further ports that can be configured as coupled ports.

[0102] For example, it is possible that the multi-port directional coupler has a first port configured as an input port, a second port configured as transmitted port, no port configured as isolated port and one or two or more ports configured as coupled ports.

[0103] The distribution and spatial arrangement of the possible ports may obey the above-described symmetry of the multi-port directional coupler. However, it may also be possible that the distribution and spatial arrangement of the possible ports deviates from said exemplary symmetry.

[0104] However, even if the distribution and spatial arrangement of the possible ports are asymmetric, the arrangement of the dielectric slabs and / or the arrangement of the possible rods can still obey / follow said exemplary symmetry of the multi-port directional coupler having two orthogonal symmetry axes.

[0105] In an exemplary case, the multi-port directional coupler can have more than four ports, wherein the first dielectric slab comprises two ports and the second dielectric slab comprises more than two ports.

[0106] For example, the first dielectric slab can comprise a first port that is configured as input port and a second port that is configured as transmitted port and the second dielectric slab comprises a port that is configured as isolated port and at least two further ports that are configured as coupled ports.

[0107] As indicated above, the presence of an isolated port is optional. Hence, in another example, the first dielectric slab can comprise a first port that is configured as input port and a second port that is configured as transmitted port and the second dielectric slab can comprise at least two further ports that are configured as coupled ports.

[0108] In these examples, wherein the multi-port directional coupler can comprise two or more ports that are configured as coupled ports, the permittivity of the first dielectric slab can be different from the permittivity of the second dielectric slab.

[0109] For example, the permittivity of the first dielectric slab can be higher than the permittivity of the second dielectric slab. Alternatively, the permittivity of the first dielectric slab can be lower than the permittivity of the second dielectric slab.

[0110] For example, the permittivity ratio of the two dielectric slabs can be set / chosen to be less than 1 for one of the bandwidth limits and can be set / chosen to be greater than 1 for the other bandwidth limit, i.e. the permittivity ratio may lie between 0 and infinity along the bandwidth of the multi-port directional coupler.

[0111] Said exemplary configurations of a multi-port directional coupler with multiple ports on a dielectric slab, i.e. on the second dielectric slab, being configured as coupled ports, can provide a frequency multiplexer / de-multiplexer functionality, wherein said at least two coupled ports can receive / col- lect electromagnetic wave signals, e.g. RF signals, with different frequencies.

[0112] This advantageously exploits the fact that having a first dielectric slab with a permittivity that is different from the permittivity of the second dielectric slab can lead to a frequency-dependent direction of propagation according to Snell’s law.

[0113] Stated differently, signals, e.g. RF signals, with different frequencies can propagate at different angles / different directions from the interface or gap between the first dielectric slab and the second dielectric slab towards multiple coupled ports, as for example illustrated in Fig. 2c.

[0114] The permittivity and / or material of the two dielectric slabs can further be set or chosen such as to maximize the angular separation / angular distance between the different signal paths directed towards the different coupled ports.

[0115] In other words, a potentially occurring undesired frequency dependence of the multi-port directional coupler can be turned into an advantage for applications that can benefit from the multi-port directional coupler having a frequency multiplexer / de-multiplexer functionality. Furthermore, the exemplary ports of the multi-port directional coupler can each be configured as dielectric rod waveguide ports.

[0116] The above and herein exemplary described multi-port directional coupler can further comprise a plurality of signal launchers, wherein each signal launcher can be spatially associated to one specific port of the multi-port directional coupler.

[0117] At least one signal launcher or all of said signal launchers can be configured for collimating electromagnetic wave signals, e.g. RF signals, received from external sources, e.g. external dielectric rod waveguides, and for injecting the received electromagnetic wave signals into at least one of the dielectric slabs, e.g. the first and / or the second dielectric slab.

[0118] In particular, at least one signal launcher or all signal launchers can be configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs in the form of a single two-dimensional beam for all operating frequencies of the multi-port directional coupler.

[0119] According to the reciprocity theorem of antenna systems, said signal launchers also can be configured for receiving / collecting signals, e.g. RF signals, incoming from other ports of the multiport directional coupler.

[0120] Each port of a multi-port directional coupler, e.g. in an exemplary four-port configuration or in a configuration with more than three ports or more than four ports, can then, for example, be connected to another port via a reflected signal path and to another via a transmitted signal path.

[0121] The above described multi-port directional coupler, e.g. having three or four or more ports, can further have a configuration wherein the first dielectric slab and the second dielectric slab are planar slabs and have a rectangular shape and wherein the possible signal launchers and ports are located at or near the corners of the dielectric slabs.

[0122] Different ports can be located at different corners of the first and second dielectric slabs. However, it is also possible that multiple ports can be located at or near the corners of the dielectric slabs. For example, multiple coupled ports could be located at or near the same corner of a dielectric slab, e.g. of the second dielectric slab.

[0123] For example, in the previously described exemplary case of the multi-port directional coupler having a multiplexer / de-multiplexer functionality, the multi-port directional coupler may comprise multiple coupled ports at or near the same corner of a dielectric slab, e.g. of the second dielectric slab. Said corners can be corners of the dielectric slabs that are neither located on the first side of the first dielectric slab nor located on the first side of the second dielectric slab, i.e. said corners are not located at the interface or gap between dielectric slabs.

[0124] Furthermore, at least one port or all ports of any of the above described possible multi-port directional coupler configurations can be configured as dielectric waveguide ports.

[0125] Said possible signal launchers can be of one of the following types: total internal reflection reflectors, e.g. total internal reflection parabolic reflectors, planar elliptic or flat mirrors, and / or tapered dielectric rod waveguides.

[0126] Stated differently, the possible curves formed by the intersections of the dielectric slabs with possible said signal launcher mirrors can be parabolic, elliptic or flat.

[0127] Said possible signal launchers can further each comprise a plurality of mirrors having the same or different configurations, e.g. a signal launcher having an elliptic mirror and a parabolic mirror.

[0128] Furthermore, in all above and herein described exemplary configurations of the multi-port directional coupler, the at least one port of the exemplary multi-port directional coupler or all ports of the exemplary multi-port directional coupler can be configured as dielectric rod waveguides.

[0129] As previously indicated, an exemplary multi-port directional coupler can be configured such that the first dielectric slab and the second dielectric slab have the same size, the same shape and the same dimensions.

[0130] Furthermore, in the possible case of said exemplary multi-port directional coupler also having a first rod / dowel and a second rod / dowel, said first rod / dowel and said second rod / dowel can have the same size, the same shape and the same dimensions.

[0131] Having said first rod / dowel and said second rod / dowel being symmetric, i.e. having the same size, the same shape and the same dimensions, can inter alia improve the frequency-independent performance of the multi-port directional coupler and can avoid exciting unwanted higher-order modes in the vertical plane of the dielectric slabs.

[0132] However, it also possible that said first rod / dowel and said second rod / dowel and / or said dielectric slabs can have different sizes, different shapes and different dimensions.

[0133] An exemplary device for broadband communication applications can comprise at least one multiport directional coupler as exemplary described above and herein, wherein said at least one multiport directional coupler or half-mirror can have any of the above exemplary described features in any configuration, e.g. a multi-port directional coupler in said exemplary fundamentally broadband half-mirror configuration or in said exemplary Snell’s law half-mirror configuration or a multi-port directional coupler in said exemplary three-slab or lossy slab configuration. For completeness, it is noted that said exemplary three-slab or lossy slab configuration may require the presence of a gap between the first dielectric slab and the second dielectric slab, such that said exemplary third dielectric slab can at least partially pass through said gap.

[0134] An exemplary device for broadband communication applications can inter alia be one of the following types: a network analyzer, e.g. a vector network analyzer, a transceiver, a spectrometer or an image detector.

[0135] The following figures illustrate exemplary:

[0136] Fig. 1a: Exemplary multi-port directional coupler in an exemplary fundamentally broadband half-mirror configuration

[0137] Fig. 1b: Exemplary multi-port directional coupler in an exemplary

[0138] Snell’s law half-mirror configuration

[0139] Fig. 2a: Alternative exemplary multi-port directional coupler in an exemplary fundamentally broadband half-mirror configuration

[0140] Fig. 2b: Alternative exemplary multi-port directional coupler in an exemplary

[0141] Snell’s law half-mirror configuration

[0142] Fig. 2c: Alternative exemplary multi-port directional coupler in an exemplary Snell’s law half-mirror configuration with frequency multiplexer / de-multiplexer functionality

[0143] Fig. 2d: Alternative exemplary multi-port directional coupler in an exemplary three-slab or lossy- slab configuration

[0144] Fig. 3: Alternative exemplary multi-port directional coupler with exemplary total internal reflection parabolic reflectors

[0145] Fig. 4: Alternative exemplary multi-port directional coupler with exemplary tapered dielectric rod waveguides

[0146] Fig. 5: Exemplary graph: S-parameters of exemplary multi-port directional coupler

[0147] The figures serve to exemplary illustrate certain exemplary technical aspects of some features of the claims. Fig.1a exemplary shows a simplified perspective view of an exemplary multi-port directional coupler 100 for broadband communication applications that can comprise any of the above discussed features.

[0148] For example, multi-port directional coupler 100 may comprise a half-mirror 110 that can comprise a first dielectric slab 101 and a second dielectric slab 102.

[0149] The first dielectric slab 101 and the second dielectric slab 102 can be arranged adjacently in a first plane.

[0150] For example, said first plane, in which the dielectric slabs 101 , 102 can be arranged adjacently to each other as shown, can be a plane that can be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109 with orthogonal axes X,Y,Z.

[0151] Between the dielectric slabs 101 , 102, in particular between a first side 101a of the first dielectric slab 101 and a first side 102a of the second dielectric slab 102 a gap 105, e.g. an air gap, can be formed. Said sides 101a, 102a of the dielectric slabs 101 , 102 can be arranged opposite to each other.

[0152] Said possible gap 105 can stretch along the whole length of said sides 101a, 102a of the dielectric slabs 101 , 102 and the width of said possible gap can be constant across the whole length of the gap 105.

[0153] The exemplary multi-port directional coupler 100 can further comprise a first rod 103 arranged in a second plane and a second rod 104 arranged in a third plane.

[0154] The second plane and the third plane are different from each other but can be parallel to each other. Furthermore, the second plane and the third plane can also be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109 with orthogonal axes X,Y,Z.

[0155] However, said first plane is also different from both the second plane and the third plane, wherein said first plane lies between the second plane and the third plane.

[0156] In other words, the second plane can lie above the first plane and the third plane can lie below the first plane with reference to the vertical Z-axis of coordinate system 109.

[0157] Said first plane can have the same distance, e.g. the same absolute distance, e.g. measured along the vertical Z-axis of coordinate system 109, from both the second plane and the third plane. The longitudinal axis 103a of the first rod 103 and the longitudinal axis 104a of the second rod 104 can be arranged parallel and opposite to each other.

[0158] In the exemplary configuration shown, the longitudinal axis 103a of the first rod 103 lies in the second plane and the longitudinal axis 104a of the second rod 104 lies in the third plane.

[0159] In the exemplary configuration shown, the rods 103, 104 do not have any physical contact with the dielectric slabs 101 , 102.

[0160] The longitudinal axis 103a of the first rod 103 and the longitudinal axis 104a of the second rod 104 can be arranged parallel to and opposite to the longitudinal axis 105a lying between the first side 101a of the first dielectric slab 101 and the first side 102a of the second dielectric slab 102. Stated differently, the longitudinal axis 105a can lie in the gap 105 and in the first plane.

[0161] The size, shape and dimensions of the first dielectric slab 101 can be the same as the size, shape and dimensions of the second dielectric slab 102. Similarly, the size, shape and dimensions of the first rod 103 can be the same as the size, shape and dimensions of the second rod 104.

[0162] However, it also possible that said first rod / dowel 103 and said second rod / dowel 104 and / or said dielectric slabs 101 , 102 can have different sizes, different shapes and different dimensions.

[0163] The exemplary multi-port directional coupler 100 can have two orthogonal symmetry axes. For example, the first symmetry axis can coincide with longitudinal axis 105a lying in the gap 105, and the second symmetry axis can be defined being orthogonal to said first symmetry axis.

[0164] The permittivity of the first dielectric slab 101 can be equal or different to the permittivity of the second dielectric slab 102.

[0165] In the example illustrated in Fig. 1a, the permittivity of the first dielectric slab 101 is equal to the permittivity of the second dielectric slab 102.

[0166] Hence, the exemplary multi-port directional coupler 100 can be seen as representing an example of a multi-port directional coupler in a fundamentally broadband half-mirror configuration.

[0167] For completeness, it is noted that said first dielectric slab 101 and said second dielectric slab 102 may each comprise at least one port, wherein said ports can further comprise signal launchers, e.g. as illustrated in Figs. 2a, 2b, 2c, 3.

[0168] However, for simplicity and easier readability of Fig. 1a, these possible ports of the dielectric slabs 101 , 102 are not shown in Fig. 1a. The reference numeral 106 exemplary illustrates the direction of an incoming signal, e.g. a RF signal, that can first propagate through the first dielectric slab 101. At the gap 105 and due to the gap 105 and due to the rods 103, 104, some part of the incoming signal is reflected back in the direction marked by reference numeral 107 and some part, e.g. the remaining part, is transmitted through the gap and through the second dielectric slab 102 in the direction marked by reference numeral 108.

[0169] Fig. 1 b exemplary shows a simplified perspective view of a further exemplary multi-port directional coupler 200 for broadband communication applications that also can comprise any of the above discussed features.

[0170] Said multi-port directional coupler 200 for broadband communications is very similar to the multiport directional coupler 200; however, with the following two differences.

[0171] Firstly, the multi-port directional coupler 200 may comprise a half-mirror 210 that can comprise a first dielectric slab 201 and a second dielectric slab 202 having different permittivities, e.g. the permittivity of the first dielectric slab 201 can be lower or higher than the permittivity of the second dielectric slab 202.

[0172] Secondly, no gap is formed between the first side 201a of the first dielectric slab 201 and the first side 202a of the second dielectric slab 202.

[0173] Stated differently, the first side 201a of the first dielectric slab 201 and the first side 202a of the second dielectric slab 202 can be in direct physical contact along a region or contact surface that also can be referred to as an / the interface 205 between the first side 201a of the first dielectric slab 201 and the first side 202a of the second dielectric slab 202.

[0174] Alternatively, it is also possible that a gap, e.g. an air gap, is formed or provided between the first side 201a of the first dielectric slab 201 and the first side 202a of the second dielectric slab 202.

[0175] The reference numeral 205a exemplary denotes a longitudinal axis lying in a first plane along that interface. Said first plane can be a plane that can be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109 with orthogonal axes X,Y,Z.

[0176] Said first plane and said orthogonal coordinate system 109 can be the same as in Fig. 1a.

[0177] Apart from said two differences, the multi-port directional coupler 200 can be essentially identical to the multi-port directional coupler 100 of Fig. 1a. The first dielectric slab 201 and the second dielectric slab 202 can be arranged adjacently in said first plane, that can be a plane that can be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109.

[0178] The exemplary multi-port directional coupler 200 can further comprises a first rod 203 arranged in a second plane and a second rod 204 arranged in a third plane.

[0179] The second plane and the third plane are different from each other but can be parallel to each other. Furthermore, the second plane and the third plane can also be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109 with orthogonal axes X,Y,Z.

[0180] The first plane, the second plane and the third plane can all be parallel to each other. However, said planes can all be different from each other, wherein said first plane can lie between the second plane and the third plane.

[0181] The second plane and the third plane can each have the same distance, e.g. the same absolute distance, e.g. measured along the vertical Z-axis of coordinate system 109, from the first plane, wherein the second plane lies above the first plane and the third plane lies below the first plane.

[0182] The longitudinal axis 203a of the first rod 203 and the longitudinal axis 204a of the second rod 204 can be arranged parallel and opposite to each other.

[0183] In the exemplary configuration shown, the longitudinal axis 203a of the first rod 203 lies in the second plane and the longitudinal axis 204a of the second rod 204 lies in the third plane.

[0184] In the exemplary configuration shown, the rods 203, 204 do not have any physical contact with the dielectric slabs 201 , 202.

[0185] The longitudinal axis 203a of the first rod 203 and the longitudinal axis 204a of the second rod 204 can be arranged parallel to and opposite to the longitudinal axis 205a of the interface 205 between the first side 201a of the first dielectric slab 201 and the first side 202a of the second dielectric slab 202.

[0186] The size, shape and dimensions of the first dielectric slab 201 can be the same as the size, shape and dimensions of the second dielectric slab 202. Similarly, the size, shape and dimensions of the first rod 203 can be the same as the size, shape and dimensions of the second rod 204.

[0187] However, it is also possible that said first rod / dowel 203 and said second rod / dowel 204 and / or said dielectric slabs 201 , 202 can have different sizes, different shapes and different dimensions. As in the case of multi-port directional coupler 100, the exemplary multi-port directional coupler 200 can have two orthogonal symmetry axes.

[0188] For example, the first symmetry axis can coincide with longitudinal axis 205a lying along the interface 205 between the two dielectric slabs 201 , 202, and the second symmetry axis can be defined as being orthogonal to said first symmetry axis.

[0189] The exemplary multi-port directional coupler 200 can be seen as representing an example of a multi-port directional coupler in a Snell’s law half-mirror configuration.

[0190] For completeness, it is noted that said first dielectric slab 201 and said second dielectric slab 202 may each comprise at least one port. However, for simplicity and easier readability of Fig. 1 b, these possible ports of the dielectric slabs 201 , 202 are not shown in Fig. 1 b.

[0191] The reference numeral 206 exemplary illustrates the direction of an incoming signal, e.g. a RF signal, that can first propagate through the first dielectric slab 201 . At the interface 205 and due to the dielectric slabs 201 , 202 having different permittivities and due to the rods 203, 204, some part of the incoming signal is reflected back in the direction marked by reference numeral 207 and some part, e.g. the remaining part, is transmitted through the interface 205 and through the second dielectric slab 202 in the direction marked by reference numeral 208.

[0192] Fig. 2a exemplary shows a simplified perspective view of a further exemplary multi-port directional coupler 300 for broadband communication applications that also can comprise any of the above discussed features.

[0193] Exemplary multi-port directional coupler 300 can be seen as representing a further example of a multi-port directional coupler in a fundamentally broadband half-mirror configuration, similar to multi-port directional coupler 100.

[0194] The multi-port directional coupler 300 may comprise a half-mirror 310 that can comprise a first dielectric slab 301 and a second dielectric slab 302.

[0195] The first dielectric slab 301 and the second dielectric slab 302 can be arranged adjacently in a first plane, wherein said first plane can be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109 with orthogonal axes X,Y,Z.

[0196] The orthogonal coordinate system 109 of Fig. 2a can be the same as the orthogonal coordinate system of Fig. 1a and Fig. 1 b. Between the dielectric slabs 301 , 302, in particular between a first side 301a of the first dielectric slab 301 and a first side 302a of the second dielectric slab 302 a gap 305, e.g. an air gap, can be formed. Said sides 301a, 302a of the dielectric slabs 301 , 302 can be arranged opposite to each other.

[0197] Said possible gap 305 can stretch along the whole length of said sides 301a, 302a of the dielectric slabs 301 , 302 and the width of said possible gap can be constant across the whole length of the gap 305.

[0198] The exemplary multi-port directional coupler 300 can further comprise a first rod 303 arranged in a second plane and a second rod 304 arranged in a third plane.

[0199] The first plane, the second plane and the third plane can all be parallel to each other. However said planes can all be different from each other, wherein said first plane can lie between the second plane and the third plane.

[0200] In other words, the second plane can lie above the first plane and the third plane can lie below the first plane with reference to the vertical Z-axis of coordinate system 109.

[0201] The second plane and the third plane can each have the same distance, e.g. the same absolute distance, e.g. measured along the vertical Z-axis of coordinate system 109, from the first plane.

[0202] The longitudinal axis 303a of the first rod 303 and the longitudinal axis 304a of the second rod 304 can be arranged parallel and opposite to each other.

[0203] In the exemplary configuration shown, the longitudinal axis 303a of the first rod 303 lies in the second plane and the longitudinal axis 304a of the second rod 304 lies in the third plane.

[0204] In the exemplary configuration shown, the rods 303, 304 do not have any physical contact with the dielectric slabs 301 , 302.

[0205] The longitudinal axis 303a of the first rod 303 and the longitudinal axis 304a of the second rod 304 can be arranged parallel to and opposite to the longitudinal axis 305a lying between the first side 301a of the first dielectric slab 301 and the first side 302a of the second dielectric slab 302. Stated differently, the longitudinal axis 305a can lie in the gap 305 between the dielectric slabs 301 , 302 and in the first plane.

[0206] The size, shape and dimensions of the first dielectric slab 301 can be the same as the size, shape and dimensions of the second dielectric slab 302. Similarly, the size, shape and dimensions of the first rod 303 can be the same as the size, shape and dimensions of the second rod 304. However, it also possible that said first rod / dowel 303 and said second rod / dowel 304 and / or said dielectric slabs 301 , 302 can have different sizes, different shapes and different dimensions.

[0207] The exemplary multi-port directional coupler 300 can have two orthogonal symmetry axes. For example, the first symmetry axis can coincide with the longitudinal axis 305a lying in the gap 305, and the second symmetry axis can be defined as being orthogonal to said first symmetry axis.

[0208] The permittivity of the first dielectric slab 301 can be equal or different to the permittivity of the second dielectric slab 302.

[0209] In the example illustrated in Fig. 2a, the permittivity of the first dielectric slab 301 is equal to the permittivity of the second dielectric slab 302.

[0210] Hence, the exemplary multi-port directional coupler 300 can be seen as representing a further example of a multi-port directional coupler in a fundamentally broadband half-mirror configuration.

[0211] Furthermore, exemplary multi-port directional coupler 300 can be seen as an example of a four- port directional coupler comprising four ports 311 (P1), 312 (P2), 313 (P3), 314 (P4), wherein each of the two adjacent dielectric slabs 301 , 302 comprises two ports.

[0212] In the illustrated example, the first dielectric slab 301 comprises the exemplary first port 311 (P1 ) and the exemplary second port 312 (P2), and the second dielectric slab 302 comprises the exemplary third port 313 (P3) and the exemplary fourth port 314 (P4).

[0213] In the illustrated example, the first port 311 (P1) is configured as input port, the second port 312 (P2) is configured as transmitted port, the third port 313 (P3) is configured as coupled port and the fourth port 314 (P4) is configured as isolated port.

[0214] This shown port configuration is exemplary only, i.e. other port configurations, e.g. wherein the second port 312 (P2) or the third port 313 (P3) or the fourth port (P4) are configured as input port and wherein the ports that are not input ports become either transmitted, or coupled or isolated ports, are conceivable too. Stated differently, setting the configuration of one of the ports as input port can automatically set / determine the configuration of the other remaining ports as transmitted, coupled or isolated ports.

[0215] For example, if a bi-directional communication is intended between port P1 and port P2, port P3 receives a signal proportional to the signal that goes from port P1 to port P2. At the same time, port P4 can extract a signal proportional to the signal that goes from port P2 to port P1. The ports 311 , 312, 313, 314 of each dielectric slab 301 , 302 are exemplary arranged at / in or near the corners of the exemplary rectangular shaped dielectric slabs 301 , 302, wherein said corners are neither located on the first side 301a of the first dielectric slab 301 nor on the first side 302a of the second dielectric slab 302.

[0216] The ports 311 , 312, 313, 314 can further each comprise a signal launcher.

[0217] In the shown example, the first port 311 (P1) comprises the first signal launcher 311a, the second port 312 (P2) comprises the second signal launcher 312a, the third port 313 (P3) comprises the third signal launcher 313a, and the fourth port 314 (P4) comprises the fourth signal launcher 314a.

[0218] At least one signal launcher or all of the signal launchers can be configured for collimating electromagnetic wave signals, e.g. RF signals, received from external sources, e.g. external dielectric rod waveguides.

[0219] Furthermore, the at least one signal launcher or all signal launchers can be configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs.

[0220] In particular, the at least one signal launcher or all signal launchers can be configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs in the form of a single two-dimensional beam for all operating frequencies of the multi-port directional coupler 300.

[0221] Furthermore, according to the reciprocity theorem of antenna systems, the at least one signal launcher or all signal launchers can be configured for receiving / collecting signals, e.g. RF signals, incoming from other ports of the multi-port directional coupler and propagating through the dielectric slabs 301 , 302.

[0222] Due to the specific exemplary arrangements of the ports, signal launchers, dielectric slabs and rods of the multi-port directional coupler 300, a well-defined single signal path between the ports can be realized; in particular, a signal path between the input port (P1) and the transmitted port (P2) and between the input port (P1) and the coupled port (P3).

[0223] In the exemplary shown configuration, the signal launcher 311a of the first port 311 (P1 , the input port) launches / injects an incoming signal, i.e. a received electromagnetic wave signal, e.g. an RF signal, received from an external source (not shown), into the first dielectric slab 301 at an exemplary injection angle 315, as indicated by the arrow 306. At the gap 305 some part of the incoming / injected signal 306 is reflected back in the direction marked by the arrow with the reference numeral 307 towards the transmitted port 312 (P2), where it is collected / received by the signal launcher 312a.

[0224] Another part of the incoming / injected signal 306, e.g. the remaining part, is transmitted through the gap 305 and through the second dielectric slab 302 in the direction marked by the arrow with reference numeral 308 towards the coupled port 313 (P3), where it is collected / received by the signal launcher 313a.

[0225] Hence, the combination of arrows 306, 307 marks an exemplary signal path from the input port 311 (P1) to the transmitted port 312 (P2) and the combination of arrows 306, 308 marks an exemplary signal path from the input port 311 (P1) to the coupled port 313 (P4).

[0226] In the exemplary shown configuration, no signal is received at / by the isolated port 314 (P4).

[0227] For completeness, it is noted that the shown angles at which the electromagnetic wave signals travel within / through the dielectric slabs 301 , 302 is exemplary only, e.g. the signal launcher 311a may inject a received signal also at a different injection angle than the exemplary injection angle 315 shown in Fig. 2a.

[0228] Fig. 2b exemplary shows a simplified perspective view of a further exemplary multi-port directional coupler 400 for broadband communication applications that also can comprise any of the above discussed features.

[0229] Said multi-port directional coupler 400 for broadband communications is very similar to the multiport directional coupler 300; however, with the following two differences.

[0230] Firstly, the multi-port directional coupler 400 may comprise a half-mirror 410 that can comprise a first dielectric slab 401 and a second dielectric slab 402 having different permittivities, e.g. the permittivity of the first dielectric slab 401 can be lower or higher than the permittivity of the second dielectric slab 402.

[0231] Secondly, no gap is formed between the first side 401a of the first dielectric slab 401 and the first side 402a of the second dielectric slab 402.

[0232] Stated differently, the first side 401a of the first dielectric slab 401 and the first side 402a of the second dielectric slab 402 can be in direct physical contact along a region or contact surface.

[0233] Said region or contact surface also can be referred to as an / the interface 405 between the first side 401a of the first dielectric slab 401 and the first side 402a of the second dielectric slab 402. Alternatively, it is also possible that a gap, e.g. an air gap, is formed or provided between the first side 401a of the first dielectric slab 401 and the first side 402a of the second dielectric slab 402.

[0234] The multi-port directional coupler 400 can therefore be seen as representing an example of a multi-port directional coupler in a Snell’s law half-mirror configuration.

[0235] The reference numeral 405a exemplary denotes a longitudinal axis lying in a first plane along said interface between the first side 401a of the first dielectric slab 401 and the first side 402a of the second dielectric slab 402.

[0236] Said first plane can be a plane that can be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109 with orthogonal axes X,Y,Z.

[0237] Said first plane and said orthogonal coordinate system 109 can be the same as in Fig. 1a, Fig. 1 b and Fig. 2a.

[0238] Apart from said two differences, the multi-port directional coupler 400 can be essentially identical to the multi-port directional coupler 300 of Fig. 2a.

[0239] Hence, the first dielectric slab 401 and the second dielectric slab 402 can be arranged adjacently in a first plane, wherein said first plane can be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109 with orthogonal axes X,Y,Z.

[0240] The exemplary multi-port directional coupler 400 can further comprise a first rod 403 arranged in a second plane and a second rod 404 arranged in a third plane.

[0241] The first plane, the second plane and the third plane can all be parallel to each other. However, said planes can all be different from each other, wherein said first plane can lie between the second plane and the third plane.

[0242] In other words, the second plane can lie above the first plane and the third plane can lie below the first plane with reference to the vertical Z-axis of coordinate system 109.

[0243] The second plane and the third plane can each have the same distance, e.g. the same absolute distance, e.g. measured along the vertical Z-axis of coordinate system 109, from the first plane.

[0244] The longitudinal axis 403a of the first rod 403 and the longitudinal axis 404a of the second rod 404 can be arranged parallel and opposite to each other. In the exemplary configuration shown, the longitudinal axis 403a of the first rod 403 lies in the second plane and the longitudinal axis 404a of the second rod 404 lies in the third plane.

[0245] In the exemplary configuration shown, the rods 403, 404 do not have any physical contact with the dielectric slabs 401 , 402.

[0246] The longitudinal axis 403a of the first rod 403 and the longitudinal axis 404a of the second rod 404 can be arranged parallel to and opposite to the longitudinal axis 405a of the interface 405 between the first side 401a of the first dielectric slab 401 and the first side 402a of the second dielectric slab 402.

[0247] The size, shape and dimensions of the first dielectric slab 401 can be the same as the size, shape and dimensions of the second dielectric slab 402. Similarly, the size, shape and dimensions of the first rod 403 can be the same as the size, shape and dimensions of the second rod 404.

[0248] However, it also possible that said first rod / dowel 403 and said second rod / dowel 404 and / or said dielectric slabs 401 , 402 can have different sizes, different shapes and different dimensions.

[0249] As in the case of multi-port directional coupler 300, the exemplary multi-port directional coupler 400 can have two orthogonal symmetry axes. For example, the first symmetry axis can coincide with longitudinal axis 405a lying along the interface 405 between the two dielectric slabs 401 , 402, and the second symmetry axis can be defined being orthogonal to said first symmetry axis.

[0250] Similar to the multi-port directional coupler 300 of Fig. 2a, the multi-port directional coupler 400 of Fig. 2b can be seen as an example of a four-port directional coupler comprising four ports 411 (P1 ), 412 (P2), 413 (P3), 414 (P4) wherein each of the two adjacent dielectric slabs 401 , 402 comprises two ports.

[0251] In the illustrated example, the first port 411 (P1) is configured as input port, the second port 412 (P2) is configured as transmitted port, the fourth port 414 (P4) is configured as isolated port and the third port 413 (P3) is configured as coupled port.

[0252] This shown port configuration is exemplary only, i.e. other port configurations, e.g. wherein the second port 412 (P2) or the third port 413 (P3) or the fourth port (P4) are configured as input port and wherein the ports that are not input ports become either transmitted, or coupled or isolated ports, are conceivable too. Stated differently, setting the configuration of one of the ports as input port can automatically set / determine the configuration of the other remaining ports as transmitted, coupled or isolated ports. The ports 411 , 412, 413, 414 of each dielectric slab 401 , 402 are exemplary arranged at / in or near the corners of the exemplary rectangular shaped dielectric slabs 401 , 402, wherein said corners are neither located on the first side 401a of the first dielectric slab 401 nor on the first side 402a of the second dielectric slab 402.

[0253] The ports 411 , 412, 413, 414 can further each comprise a signal launcher.

[0254] In the shown example, the first port 411 (P1) comprises the first signal launcher 411a, the second port 412 (P2) comprises the second signal launcher 412a, the third port 413 (P3) comprises the third signal Iauncher413a, and the fourth port414 (P4) comprises the fourth signal Iauncher414a.

[0255] At least one signal launcher or all of the signal launchers can be configured for collimating electromagnetic wave signals, e.g. RF signals, received from external sources, e.g. external dielectric rod waveguides.

[0256] Furthermore, the at least one signal launcher or all signal launchers can be configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs.

[0257] In particular, the at least one signal launcher or all signal launchers can be configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs in the form of a single two-dimensional beam for all operating frequencies of the multi-port directional coupler 400.

[0258] Furthermore, according to the reciprocity theorem of antenna systems, the at least one signal launcher or all signal launchers can be configured for receiving / collecting signals, e.g. RF signals, incoming from other ports of the multi-port directional coupler and propagating through the dielectric slabs 401 , 402.

[0259] Due to the specific exemplary arrangements of the ports, signal launchers, dielectric slabs and rods of the multi-port directional coupler 400, a well-defined single signal path between the ports can be realized; in particular, a signal path between the input port (P1) and the transmitted port (P2) and between the input port (P1 ) and the coupled port (P3).

[0260] In the exemplary shown configuration, the signal launcher 411a of the first port 411 (P1 , the input port) launches / injects an incoming signal, i.e. a received electromagnetic wave signal, e.g. an RF signal, received from an external source (not shown), into the first dielectric slab 401 at an exemplary injection angle 415, as indicated by the arrow 406. At the interface 405 between / along the first sides 401a, 402a of the dielectric slabs 401 , 402, some part of the incoming / injected signal 406 is reflected back in the direction marked by the arrow with the reference numeral 407 towards the transmitted port 412 (P2), where it is col- lected / received by the signal launcher 412a.

[0261] Another part of the incoming / injected signal 406, e.g. the remaining part, is transmitted through the interface 405 and through the second dielectric slab 402 in the direction marked by the arrow with reference numeral 408 towards the coupled port 413 (P3), where it is collected / received by the signal launcher 413a.

[0262] Hence, the combination of arrows 406, 407 marks an exemplary signal path from the input port 411 (P1) to the transmitted port 412 (P2) and the combination of arrows 406, 408 marks an exemplary signal path from the input port 411 (P1) to the coupled port 413 (P4)

[0263] In the exemplary shown configuration, no signal is received at / by the isolated port 414 (P4).

[0264] For completeness, it is noted that the shown angles at which the electromagnetic wave signals travel within / through the dielectric slabs 401 , 402 is exemplary only, e.g. the signal launcher 411a may inject a received signal also at a different injection angle than the exemplary injection angle 415 shown in Fig. 2b.

[0265] Fig. 2c exemplary shows a simplified perspective view of a further exemplary multi-port directional coupler 800 for broadband communication applications that also can comprise any of the above discussed features.

[0266] Said multi-port directional coupler 800 for broadband communications is very similar or identical to the multi-port directional coupler 400, aside from a different number and configuration of the ports of the second dielectric slab 802.

[0267] Hence, the multi-port directional coupler 800 may comprise a half-mirror 810 that can comprise a first dielectric slab 801 and a second dielectric slab 802 having different permittivities, e.g. the permittivity of the first dielectric slab 801 can be lower or higher than the permittivity of the second dielectric slab 802.

[0268] Furthermore, the first dielectric slab 801 and the second dielectric slab 802 can be arranged adjacently in a first plane, wherein said first plane can be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109 with orthogonal axes X,Y,Z. A gap or no gap can be formed or provided between the first side 801a of the first dielectric slab 801 and the first side 802a of the second dielectric slab 802.

[0269] The exemplary multi-port directional coupler 800 can be seen as representing a further example of a multi-port directional coupler in a Snell’s law half-mirror configuration.

[0270] The exemplary multi-port directional coupler 800 can further comprise a first rod 803 arranged in a second plane and a second rod 804 arranged in a third plane.

[0271] The first plane, the second plane and the third plane can all be parallel to each other. However said planes can all be different from each other, wherein said first plane can lie between the second plane and the third plane.

[0272] In other words, the second plane can lie above the first plane and the third plane can lie below the first plane with reference to the vertical Z-axis of coordinate system 109.

[0273] The second plane and the third plane can each have the same distance, e.g. the same absolute distance, e.g. measured along the vertical Z-axis of coordinate system 109, from the first plane.

[0274] The longitudinal axis of the first rod 803 and the longitudinal axis of the second rod 804 can be arranged parallel and opposite to each other.

[0275] In the exemplary configuration shown, the longitudinal axis of the first rod 803 lies in the second plane and the longitudinal axis of the second rod 804 lies in the third plane.

[0276] In the exemplary configuration shown, the rods 803, 804 do not have any physical contact with the dielectric slabs 801 , 802.

[0277] The size, shape and dimensions of the first dielectric slab 801 can be the same as the size, shape and dimensions of the second dielectric slab 802. Similarly, the size, shape and dimensions of the first rod 803 can be the same as the size, shape and dimensions of the second rod 804.

[0278] However, it also possible that said first rod / dowel 803 and said second rod / dowel 804 and / or said dielectric slabs 801 , 802 can have different sizes, different shapes and different dimensions.

[0279] The port configuration of the first dielectric slabs 801 can be similar or identical to the port configuration of the first dielectric slabs 401 of the multi-port directional coupler 400 of Fig. 2b.

[0280] In the illustrated example, the first port 811 (P1) is configured as input port, the second port 812 (P2) is configured as transmitted port. Also similar or identical to the multi-port directional coupler 400 of Fig. 2b, the second dielectric slab 802 can comprise a port 814 (P4) that is configured as isolated port. As previously noted, the presence of an isolated port is optional, i.e. said port 814 (P4) that is configured as isolated port is optional only.

[0281] However, different from the multi-port directional coupler 400 of Fig. 2b, the second dielectric slab 802 can have multiple coupled ports.

[0282] In the illustrated example, the multi-port directional coupler 800 has three coupled ports, namely a first coupled port 813 (P3), a second coupled port 813’ (P3’) and a third coupled port 813” (P3”).

[0283] Said number of coupled ports is exemplary only; any other number greater than two is possible.

[0284] Stated differently, aside from the different number and configuration of the ports of the second dielectric slab 802, the multi-port directional coupler 800 can be identical to the multi-port directional coupler 400 of Fig. 2b.

[0285] Each of the ports 811 , 812, 814, 813, 813’ and 813” can comprise a signal launcher 811a, 812a, 814a, 813a, 813a’ and 813a”.

[0286] In the exemplary shown configuration, the signal launcher 811a of the first port 811 (P1 , the input port) launches / injects an incoming signal, i.e. a received electromagnetic wave signal, e.g. an RF signal, received from an external source (not shown), into the first dielectric slab 801 at an exemplary injection angle as indicated by the arrow 806.

[0287] At the interface 805 between / along the first sides 801a, 802a of the dielectric slabs 801 , 802, some part of the incoming / injected signal 806 is reflected back in the direction marked by the arrow with the reference numeral 807 towards the transmitted port 812 (P2), where it is col- lected / received by the signal launcher 812a.

[0288] Another part of the incoming / injected signal 806, e.g. the remaining part, is transmitted through the interface 805 and through the second dielectric slab 802.

[0289] Due to the second dielectric slab 802 having a different permittivity than the permittivity of the first dielectric slab 801 , the direction of propagation of the part of the signal that is transmitted through the interface 805 is frequency-dependent. Hence, signals with different frequencies propagate at different angles / different directions from the interface 805 in the second dielectric slab 802, as indicated by arrows 808, 808’ and 808”.

[0290] For example, the permittivity of slab 802 can be higher or lower than the permittivity of slab 801 . Said signals transmitted through interface 805 and with a frequency-dependent propagation direction 808, 808’ and 808” can then be received and collected by the different coupled ports 813 (P3), 813’ (P3’) and a third coupled port 813” (P3”).

[0291] In the example shown, the signal with direction 808 is received / collected by the first coupled port 813 (P3), the signal with direction 808’ is received / collected by the / a second coupled port 813’ (P3’) and the signal with direction 808” is received / collected by the third coupled port 813” (P3”).

[0292] This way the multi-port directional coupler 800 can provide a frequency multiplexer (mux) / de- multiplexer (demux) functionality.

[0293] For completeness, it is noted that in the exemplary shown configuration, no signal is received at / by the isolated port 814 (P4).

[0294] Fig. 2d exemplary shows a simplified perspective view of a further exemplary multi-port directional coupler 900 for broadband communication applications that also can comprise any of the above and herein discussed features.

[0295] Said multi-port directional coupler 900 for broadband communications is very similar to the multiport directional coupler 200; however, with the following differences.

[0296] A gap 905, e.g. an air gap, is formed or provided between the first side 901a of the first dielectric slab 901 and the first side 902a of the second dielectric slab 902.

[0297] In addition to having two dielectric slabs 901 , 902 and which are arranged adjacently in a first plane, that can be a plane that can be oriented parallel to a plane spanned by the X,Y axes of the exemplary orthogonal coordinate system 109, the multi-port directional coupler 900 has a third dielectric slab 903.

[0298] Said third dielectric slab 903 is arranged such that it passes through the gap 905 and said third dielectric slab 903 has an orientation that is perpendicular / orthogonal to both the first dielectric slab 901 and the second dielectric slab 902.

[0299] For example, said third dielectric slab 903 can lie in a plane that is parallel to or coincides with the plane spanned by the Y,Z axes of the exemplary orthogonal coordinate system 109.

[0300] The thickness of said third dielectric slab 903 can be equal to or less than the width of the gap 905. Also the third dielectric slab 903 can have an extension, e.g. width or length, that can correspond to the length of the gap 905.

[0301] Hence, the dielectric slab 903 can partially or fully fill the gap across the full width and / or across the full length of the gap 905.

[0302] When placing the origin of the orthogonal coordinate system 109 at the center of the described multi-port directional coupler 900, said possible third dielectric slab 903 may lie in the YZ-plane and the first dielectric slab 901 and the second dielectric slab 902 can lie in the YX-plane.

[0303] The third dielectric slab 903 may form a symmetry plane for the multi-port directional coupler 900 and wherein a first half 903a of the third dielectric slab 903 can lie above the dielectric slabs 901 , 902, i.e. measured along the positive Z-axis, and a second half 903b of the third dielectric slab 903 can lie below the dielectric slabs 901 , 902, i.e. measured along the negative Z-axis.

[0304] Hence, the cross section of the multi-port directional coupler 900 can be cross-like.

[0305] Similar to the first dielectric slab 901 and the second dielectric slab 902, said possible third dielectric slab 903 can have a rectangular shape.

[0306] The multi-port directional coupler 900 does not have any rods or dowels. In particular, the multiport directional coupler 900 does not have any rods or dowels that are arranged to sandwich the dielectric slabs 901 , 902.

[0307] The exemplary third dielectric slab 903 may be a lossy dielectric slab. More specifically, said third dielectric slab 903 may have a dielectric conductivity o less than 10000 S / m (siemens per meter), e.g. the dielectric conductivity o can lie between 0 S / m and 10000 S / m.

[0308] The shown exemplary multi-port directional coupler 900 can be understood as representing a possible lossy-slab configuration of a multi-port directional coupler.

[0309] Apart from the above discussed differences, the multi-port directional coupler 900 can be similar or identical to the multi-port directional coupler 200.

[0310] Hence, the first dielectric slab 901 and the second dielectric slab 902 of half-mirror 910 can have different permittivities, e.g. the permittivity of the first dielectric slab 901 can be lower or higher than the permittivity of the second dielectric slab 902.

[0311] The size, shape and dimensions of the first dielectric slab 901 can be the same as the size, shape and dimensions of the second dielectric slab 902. The two halves or sides 903a, 903b of the third dielectric slab 903 can also have the same size, shape and dimensions as the first dielectric slab 901 and as the second dielectric slab 902.

[0312] This may inter alia facilitate the manufacturing process of the multi-port directional coupler 200.

[0313] In any case, the size, shape and dimension of the third dielectric slab 903 may be set or may be chosen such that it can collect the majority of the signal power of the incoming signal 906, e.g. of a RF signal, e.g. more than 50% or more than 90% of the signal power of the incoming signal 906.

[0314] For completeness, it is noted that said first dielectric slab 901 and said second dielectric slab 902 may each comprise at least one port, wherein said ports can further comprise signal launchers, e.g. as illustrated in Figs. 2a, 2b, 2c, 3.

[0315] However, for simplicity and easier readability of Fig. 2d, these possible ports of the dielectric slabs 901 , 902 are not shown in Fig. 2d.

[0316] The reference numeral 906 exemplary illustrates the direction of an incoming signal, e.g. a RF signal, that can first propagate through the first dielectric slab 901. At the gap 905 and due to the dielectric slabs 901 , 902 having different permittivities and due to the third dielectric slab 903, some part of the incoming signal is reflected back in the direction marked by reference numeral 907 and some part, e.g. the remaining part, is transmitted across the gap 905 and through the third dielectric slab 903 and through the second dielectric slab 902 in the direction marked by reference numeral 908.

[0317] Fig. 3 exemplary shows a simplified perspective view of a further exemplary multi-port directional coupler 500 for broadband communication applications that also can comprise any of the above discussed features.

[0318] The orthogonal coordinate system 109 of Fig. 3 can be the same as the orthogonal coordinate system of Fig. 1a, Fig. 1b, Fig. 2a, Fig. 2b and Fig. 2c.

[0319] However, the angle of the perspective view shown in Fig. 3 is different from the angles of the perspective views of the previous figures Fig. 1a, Fig. 1 b, Fig. 2a, Fig. 2b and Fig. 2c, as also indicated by the different orientation of coordinate system 109 of Fig. 3 with respect to the coordinate systems of Fig. 1a, Fig. 1 b, Fig. 2a, Fig. 2b and Fig. 2c.

[0320] Alternatively, the orthogonal coordinate system 109 can be oriented such that the X-axis is parallel to a line that connects port P2 and port P3 (or port P1 and port P4), and such that the Y-axis is parallel to the axes of the rods 503, 504 and such that the Z-axis is orthogonal to a / the surface of the dielectric slabs 501 , 502.

[0321] Exemplary multi-port directional coupler 500 can be seen as representing a further example of a multi-port directional coupler in a fundamentally broadband half-mirror configuration, similar to multi-port directional coupler 300.

[0322] However, as explained further below, the configuration of the ports 511 , 512, 513, 514 and its signal launchers 511a, 512a, 513a, 514a can also apply to a possible Snell’s law half-mirror configuration of the multi-port directional coupler 400.

[0323] The multi-port directional coupler 500 may comprise a half-mirror 510 that can comprise a first dielectric slab 501 and a second dielectric slab 502.

[0324] The first dielectric slab 501 and the second dielectric slab 502 can be arranged adjacently in a first plane.

[0325] Said first dielectric slab 501 and the second dielectric slab 502 can have the same permittivity.

[0326] However, it is also possible, e.g. in a possible Snell’s law half-mirror configuration, that the first dielectric slab 501 and the second dielectric slab 502 can have different permittivities.

[0327] Between the dielectric slabs 501 , 502, in particular between a first side 501a of the first dielectric slab 501 and a first side 502a of the second dielectric slab 502 a gap 505, e.g. an air gap, can be formed.

[0328] Said sides 501a, 502a of the dielectric slabs 501 , 502 can be arranged opposite to each other.

[0329] Alternatively, e.g. in a possible Snell’s law half-mirror configuration of the multi-port directional coupler 500, it is possible that no gap is formed between the first side 501a of the first dielectric slab 501 and the first side 502a of the second dielectric slab 502.

[0330] Stated differently, the first side 501a of the first dielectric slab 501 and the first side 502a of the second dielectric slab 502 can be in direct physical contact along a region or contact surface.

[0331] Said region or contact surface also can be referred to as an / the interface between the first side 501a of the first dielectric slab 501 and the first side 502a of the second dielectric slab 502.

[0332] Regardless of the multi-port directional coupler 500 being in a fundamentally broadband halfmirror configuration or in a Snell’s law half-mirror configuration, the multi-port directional coupler 500 can comprise a first rod 503 arranged in a second plane and a second rod 504 arranged in a third plane.

[0333] The first plane, i.e. the plane in which the dielectric slabs 501 , 502 are adjacently arranged, the second plane in which the first rod 503 is arranged and the third plane in which the second rod 504 is arranged, can all be parallel to each other.

[0334] However, said planes can all be different from each other, wherein said first plane can lie between the second plane and the third plane.

[0335] The second plane and the third plane can each have the same distance, e.g. the same absolute distance, e.g. measured along an orthogonal axis perpendicular to the first plane, from the first plane.

[0336] The longitudinal axis of the first rod and the longitudinal axis of the second rod can be arranged parallel and opposite to each other.

[0337] In the exemplary configuration shown, the longitudinal axis of the first rod 503 lies in the second plane and the longitudinal axis of the second rod 504 lies in the third plane.

[0338] In the exemplary configuration shown, the rods 503, 504 do not have any physical contact with the dielectric slabs 501 , 502.

[0339] The longitudinal axis of the first rod 503 and the longitudinal axis of the second rod 504 can be arranged parallel to and opposite to the longitudinal axis lying in the gap 505 between the dielectric slabs 501 , 502.

[0340] Alternatively, e.g. in a Snell’s law half-mirror configuration, the longitudinal axis of the first rod 503 and the longitudinal axis of the second rod 504 can be arranged parallel to and opposite to the interface between the first side 501a of the first dielectric slab 501 and the first side 502a of the second dielectric slab 502.

[0341] The size, shape and dimensions of the first dielectric slab 501 can be the same as the size, shape and dimensions of the second dielectric slab 502. Similarly, the size, shape and dimensions of the first rod 503 can be the same as the size, shape and dimensions of the second rod 504.

[0342] However, it is also possible that said first rod / dowel 503 and said second rod / dowel 504 and / or said dielectric slabs 501 , 502 can have different sizes, different shapes and different dimensions. Similar to the multi-port directional couplers 300, 400 of Fig. 2a and Fig. 2b, the multi-port directional coupler 500 of Fig. 3 can be seen as an example of a four-port directional coupler comprising four ports 511 (P1), 512 (P2), 513 (P3), 514 (P4), wherein each of the two adjacent dielectric slabs 501 , 502 comprises two ports.

[0343] In the example of Fig. 3 an exemplary scale 516 of an exemplary maximum length of multi-port directional coupler 500 is provided, said exemplary length being a length of 73.08 mm between port 511 and port 514 and which is the same as the length between port 512 and port 513.

[0344] It is emphasized that this absolute scale is exemplary only, as are the relative scales of the previous figures.

[0345] In the illustrated example, the first port 511 (P1) is configured as input port, the second port 512 (P2) is configured as transmitted port, the third port 513 (P3) is configured as coupled port and the fourth port 514 (P4) is configured as isolated port.

[0346] This shown port configuration is exemplary only, i.e. other port configurations, e.g. wherein the second port 512 (P2) or the third port 513 (P3) or the fourth port 514 (P4) are configured as input port and wherein the ports that are not input ports become either transmitted, or coupled or isolated ports, are conceivable too. Stated differently, setting the configuration of one of the ports as input port can automatically set / determine the configuration of the other remaining ports as transmitted, coupled or isolated ports.

[0347] The ports 511 , 512, 513, 514 of each dielectric slab 501 , 502 are exemplary arranged at / in or near the corners of the exemplary rectangular shaped dielectric slabs 501 , 502, wherein said corners are neither located on the first side 501 a of the first dielectric slab 501 nor on the first side 502a of the second dielectric slab 502.

[0348] All the ports 511 , 512, 513, 514 of the multi-port directional coupler 500 are exemplary configured as dielectric rod waveguide ports or channel waveguide ports.

[0349] The ports 511 , 512, 513, 514 can further each comprise a signal launcher.

[0350] In the shown example, the first port 511 (P1) comprises the first signal launcher 511a, the second port 512 (P2) comprises the second signal launcher 512a, the third port 513 (P3) comprises the third signal launcher 513a, and the fourth port 514 (P4) comprises the fourth signal launcher 514a. At least one signal launcher or all of the signal launchers can be configured for collimating electromagnetic wave signals, e.g. RF signals, received by the ports from external sources, e.g. from other waveguides that can be connected to the waveguide ports.

[0351] Furthermore, the launchers can be configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs in the form of a single two-dimensional beam for all operating frequencies of the multi-port directional coupler 500.

[0352] Furthermore, according to the reciprocity theorem of antenna systems, the at least one signal launcher or all signal launchers can be configured for receiving / collecting signals, e.g. RF signals, incoming from other ports of the multi-port directional coupler and propagating through the dielectric slabs 501 , 502.

[0353] The signal paths between the ports can inter alia be similar or identical to the signal paths described for the ports of multi-port directional couplers 300 (Fig. 2a) or 400 (Fig. 2b) or 600 (Fig. 4).

[0354] In the example shown, all signal launchers 511a, 512a, 513a, 514a are exemplary configured as total internal reflection parabolic reflectors.

[0355] Said exemplary signal launchers 511a, 512a, 513a, 514a that are configured as total internal reflection parabolic reflectors can be inter alia characterized by each having a curved cloven edge 511aa, 512aa, 513aa, 514aa.

[0356] However, is also possible that said signal launchers are non-parabolic total internal reflection reflectors mirrors or tapered dielectric rod waveguides (cf. Fig. 4).

[0357] By tuning the half-mirror 510, it is possible to set a specific directivity, which can be defined as the ratio of the signal amplitudes of transmitted port 512 (P2) and the coupled port 513 (P3).

[0358] The here described exemplary multi-port directional coupler 500 can inter alia be tuned such that the same signal amplitudes in the transmitted port 512 (P2) and the coupled port 513 (P3) can be achieved.

[0359] The term tuning herein can be understood as tuning or changing the spatial dimensions of the half-mirror of the multi-port directional coupler. In particular, this may comprise changing the diameters of the rods, and / or changing the distance of the rods to the dielectric slab, and / or changing the width of a / the possible gap between the dielectric slabs. Furthermore, this can include changing the length of the rods and / or the length of a / the possible gap between the dielectric slabs.

[0360] Fig. 4 exemplary shows a simplified perspective view of a further exemplary multi-port directional coupler 600 for broadband communication applications that also can comprise any of the above discussed features.

[0361] The orthogonal coordinate system 109 of Fig. 4 can be the same as the orthogonal coordinate system of Fig. 1a, Fig. 1b, Fig. 2a, Fig. 2b and Fig. 3 and the viewing angle and orientation of the exemplary multi-port directional coupler 600 can be similar or identical to the viewing angle and orientation of the exemplary multi-port directional couplers 100, 200, 300, 400.

[0362] Exemplary multi-port directional coupler 600 can be seen as representing a further example of a multi-port directional coupler in a fundamentally broadband half-mirror configuration, similar to multi-port directional coupler 300 or multi-port directional coupler 500.

[0363] However, as explained further below, the configuration of the ports 611 , 612, 613, 614 and their signal launchers 611a, 612a, 613a, 614a can also apply to a possible Snell’s law half-mirror configuration of the multi-port directional coupler 600 or the multi-port directional coupler 500.

[0364] The multi-port directional coupler 600 may comprise a half-mirror 610 that can comprise a first dielectric slab 601 and a second dielectric slab 602.

[0365] The first dielectric slab 601 and the second dielectric slab 602 can be arranged adjacently in a first plane.

[0366] Said first dielectric slab 601 and the second dielectric slab 602 can have the same permittivity.

[0367] However, it is also possible, e.g. in a possible Snell’s law half-mirror configuration, that the first dielectric slab 601 and the second dielectric slab 602 can have different permittivities.

[0368] Between the dielectric slabs 601 , 602, in particular between a first side 601a of the first dielectric slab 601 and a first side 602a of the second dielectric slab 602 a gap 605, e.g. an air gap, can be formed.

[0369] Said sides 601a, 602a of the dielectric slabs 601 , 602 can be arranged opposite to each other.

[0370] Alternatively, e.g. in a possible Snell’s law half-mirror configuration of the multi-port directional coupler 600, it is possible that no gap is formed between the first side 601a of the first dielectric slab 601 and the first side 602a of the second dielectric slab 602. Stated differently, the first side 601a of the first dielectric slab 601 and the first side 602a of the second dielectric slab 602 can be in direct physical contact along a region or contact surface.

[0371] Said region or contact surface also can be referred to as an / the interface between the first side 601 a of the first dielectric slab 601 and the first side 602a of the second dielectric slab 602.

[0372] Regardless of the multi-port directional coupler 600 being in a fundamentally broadband halfmirror configuration or in a Snell’s law half-mirror configuration, the multi-port directional coupler 600 can comprise a first rod 603 arranged in a second plane and a second rod 604 arranged in a third plane.

[0373] The first plane, i.e. the plane in which the dielectric slabs 601 , 602 are adjacently arranged, the second plane in which the first rod 603 is arranged and the third plane in which the second rod 604 is arranged, can all be parallel to each other.

[0374] However, said planes can all be different from each other, wherein said first plane can lie between the second plane and the third plane.

[0375] The second plane and the third plane can each have the same distance, e.g. the same absolute distance, e.g. measured along the vertical Z-axis of coordinate system 109, from the first plane.

[0376] In other words, the second plane can lie above the first plane and the third plane can lie below the first plane with reference to the vertical Z-axis of coordinate system 109.

[0377] The longitudinal axis 603a of the first rod 603 and the longitudinal axis 604a of the second rod 604 can be arranged parallel and opposite to each other.

[0378] In the exemplary configuration shown, the longitudinal axis 603a of the first rod 603 lies in the second plane and the longitudinal axis 604a of the second rod 604 lies in the third plane.

[0379] In the exemplary shown configuration, the rods 603, 604 do not have any physical contact with the dielectric slabs 601 , 602.

[0380] The longitudinal axis 603a of the first rod 603 and the longitudinal axis 604a of the second rod 604 can be arranged parallel to and opposite to the longitudinal axis 605a lying in the gap 605 between the dielectric slabs 601 , 602.

[0381] Alternatively, e.g. in a Snell’s law half-mirror configuration, the longitudinal axis 603a of the first rod 603 and the longitudinal axis 604a of the second rod 604 can be arranged parallel to and opposite to the interface between the first side 601a of the first dielectric slab 601 and the first side 602a of the second dielectric slab 602.

[0382] The size, shape and dimensions of the first dielectric slab 601 can be the same as the size, shape and dimensions of the second dielectric slab 602. Similarly, the size, shape and dimensions of the first rod 603 can be the same as the size, shape and dimensions of the second rod 604.

[0383] However, it also possible that said first rod / dowel 603 and said second rod / dowel 604 and / or said dielectric slabs 601 , 602 can have different sizes, different shapes and different dimensions.

[0384] Similar to the multi-port directional couplers 300, 400, 500 of Fig. 2a, Fig. 2b and Fig. 3, the multiport directional coupler 600 of Fig. 4 can be seen as an example of a four-port directional coupler comprising four ports 611 (P1), 612 (P2), 613 (P3), 614 (P4), wherein each of the two adjacent dielectric slabs 601 , 602 comprises two ports.

[0385] In the illustrated example, the first port 611 (P1) is configured as input port, the second port 612 (P2) is configured as transmitted port, the third port 613 (P3) is configured as coupled port and the fourth port 614 (P4) is configured as isolated port.

[0386] This shown port configuration is exemplary only, i.e. other port configurations, e.g. wherein the second port 612 (P2) or the third port 613 (P3) or the fourth port 614 (P4) are configured as input port and wherein the ports that are not input ports become either transmitted, or coupled or isolated ports, are conceivable too. Stated differently, setting the configuration of one of the ports as input port can automatically set / determine the configuration of the other remaining ports as transmitted, coupled or isolated ports.

[0387] The ports 611 , 612, 613, 614 of each dielectric slab 601 , 602 are exemplary arranged at / in or near the corners of the exemplary rectangular shaped dielectric slabs 601 , 602, wherein said corners are neither located on the first side 601 a of the first dielectric slab 601 nor on the first side 602a of the second dielectric slab 602.

[0388] All ports 611 , 612, 613, 614 of the multi-port directional coupler 500 can be configured as dielectric rod waveguide ports or channel waveguide ports.

[0389] The ports 611 , 612, 613, 614 can further each comprise a signal launcher.

[0390] In the shown example, the first port 611 (P1) comprises the first signal launcher 611a, the second port 612 (P2) comprises the second signal launcher 612a, the third port 613 (P3) comprises the third signal Iauncher613a, and the fourth port614 (P4) comprises the fourth signal Iauncher614a. At least one signal launcher or all of the signal launchers can be configured for collimating electromagnetic wave signals, e.g. RF signals, received by the ports from external sources, e.g. from other waveguides that can be connected to the waveguide ports.

[0391] Furthermore, the at least one signal launcher or all signal launchers can be configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs.

[0392] In particular, the at least one signal launcher or all signal launchers can be configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs in the form of a single two-dimensional beam for all operating frequencies of the multi-port directional coupler 600.

[0393] Furthermore, according to the reciprocity theorem of antenna systems, the at least one signal launcher or all signal launchers can be configured for receiving / collecting signals, e.g. RF signals, incoming from other ports of the multi-port directional coupler and propagating through the dielectric slabs 601 , 602.

[0394] The signal paths between the ports can inter alia be similar or identical to the signal paths described for the ports of multi-port directional couplers 300 (Fig. 2a) or 400 (Fig. 2b) or 500 (Fig. 3).

[0395] In the example shown, all signal launchers 611a, 612a, 613a, 614a are exemplary configured as tapered dielectric rod waveguides.

[0396] However, it is also possible that said signal launchers are configured for example as total internal reflection reflectors, e.g. total internal reflection parabolic reflectors (cf. Fig. 3).

[0397] In the exemplary shown configuration, the signal launcher 611a of the first port 311 (P1 , the input port) launches / injects an incoming signal, i.e. a received electromagnetic wave signal, e.g. an RF signal, received by the port 611 from an external source (not shown), into the first dielectric slab 601 at an exemplary injection angle and with the exemplary direction indicated by the arrow 606.

[0398] This injection signal has an exemplary signal beam width 606a, wherein said beam width can diverge as it travels along / within the dielectric slabs.

[0399] At the gap 605 between the dielectric slabs (or in case of a possible Snell’s law half-mirror configuration at the interface between the dielectric slabs), some part of the incoming / injected signal 606 is reflected back in the direction marked by the arrow with the reference numeral 607 towards the transmitted port 612 (P2), where it is collected / received by the signal launcher 612a. The beamwidth 607a of this reflected signal 607 can be larger / wider than the beamwidth 606a of the injected signal 606. This is due to the use of tapered dielectric rod waveguides as signal launchers.

[0400] Another part of the incoming / injected signal 606, e.g. the remaining part, is transmitted through the gap 605 (or in case of a possible Snell’s law half-mirror configuration said part is transmitted through the interface between the dielectric slabs) and through the second dielectric slab 602 in the direction marked by the arrow with reference numeral 608 towards the coupled port 613 (P3), where it is collected / received by the signal launcher 613a.

[0401] The beamwidth 607a of this reflected signal 607 can again be larger / wider than the beamwidth 606a of the injected signal 606. This again is due to the use of tapered dielectric rod waveguides as signal launchers.

[0402] The combination of arrows 606, 607 marks an exemplary signal path from the input port 611 (P1 ) to the transmitted port 612 (P2) and the combination of arrows 606, 608 marks an exemplary signal path from the input port 611 (P1) to the coupled port 613 (P3).

[0403] In the exemplary shown configuration, no signal is received at / by the isolated port 614 (P4).

[0404] The use of tapered dielectric rod waveguides instead of total internal reflection parabolic reflectors can inter alia enable a more compact structure and design of the multi-port directional coupler.

[0405] This can be in particular beneficial for use cases in which the slightly higher insertion losses of tapered dielectric rod waveguides as compared to total internal reflection parabolic reflectors is less relevant.

[0406] Fig.5 shows an exemplary S-parameter plot 700 illustrating some exemplary performance characteristics of a multi-port directional coupler that can have some or all of the above and herein described features.

[0407] The abscissa axis 701 of the plot 700 refers to the working frequency or operating frequency of an exemplary multi-port directional coupler in units of gigahertz (GHz) and has an exemplary range of 50 to 450 GHz.

[0408] The ordinate axis 702 of the plot refers to the S-parameter amplitude in units of decibel (dB).

[0409] Adopting standard conventions in the field of microwave engineering, antennas and wireless networks, a measure of how much power of injected electromagnetic wave signal, e.g. an RF signal, is reflected or scattered back at the input port (P1) of the multi-port directional coupler and not delivered or transmitted to the transmitted port (P2) of the multi-port directional coupler can be denoted by the S-parameter S11 .

[0410] The S-parameter S21 amplitude |S21 | expressed in dB can be understood as the electromagnetic wave signal power transferred from the input port (P1) to the transmitted port (P2) of the multiport directional coupler.

[0411] Stated differently, S21 represents the relationship of the power of the electromagnetic wave signal at the transmitted port (P2) relative to the power of the electromagnetic wave signal at the input port (P1).

[0412] The S-parameter S31 amplitude |S31 | expressed in dB can be understood as the electromagnetic wave signal power transferred from the input port (P1) to the coupled port (P3) of the multi-port directional coupler.

[0413] Stated differently, S31 represents the relationship of the power of the electromagnetic wave signal at the coupled port (P3) relative to the power of the electromagnetic wave signal at the input port (P1).

[0414] The S-parameter S41 amplitude |S41 | expressed in dB can be understood as the electromagnetic wave signal power transferred from the input port (P1) to the isolated port (P4) of the multi-port directional coupler.

[0415] Stated differently, S41 represents the relationship of the power of the electromagnetic wave signal at the isolated port (P4) relative to the power of the electromagnetic wave signal at the input port (P1).

[0416] In the exemplary S-parameter plot 700, the curve or graph describing the S11 parameter amplitude for an exemplary multi-port directional coupler in dependence of the working / operating frequency of the multi-port directional coupler is denoted by the reference numeral 703.

[0417] The curve or graph describing the S21 parameter amplitude for an exemplary multi-port directional coupler in dependence of the working / operating frequency of the multi-port directional coupler is denoted by the reference numeral 704.

[0418] The curve or graph describing the S31 parameter amplitude for an exemplary multi-port directional coupler in dependence of the working / operating frequency of the multi-port directional coupler is denoted by the reference numeral 705. The curve or graph describing the S41 parameter amplitude for an exemplary multi-port directional coupler in dependence of the working / operating frequency of the multi-port directional coupler is denoted by the reference numeral 706.

[0419] As can be seen in the S21 curve 704, the transmission between ports P1 and P2 stays flat from 90 GHz to at least 450 GHz, with low insertion losses of lower than approximately 5 dB.

[0420] As evident from the S31 curve 705, the coupling between ports P1 and P3 is almost frequency independent.

[0421] If an application requires an even more frequency-independent (flat) amplitude response and a linear phase response, due to the smoothness of the curves, this can be easily achieved by a path calibration.

[0422] For example, for vector network analyzers said calibration can include measuring a plurality reference load, e.g. short, open or matched loads, in the to be analyzed instrument to compensate for instrument non-idealities.

[0423] The S11 amplitude is lower than -10 dB for the whole range of the operating frequency of the multi-port directional coupler and lower than -20 dB for frequencies greater than 100 GHz

[0424] As evident from the S41 curve, the isolation between input port P1 and isolated port P4 is greater than 20 dB in the whole band, i.e. across the whole range of the operating frequency of the multiport directional coupler.

[0425] These exemplary S-parameter characteristics can be representative of any of the above-described multi-port directional couplers, e.g. multi-port directional coupler 500.

[0426] Followed by Fig. 1a, Fig. 1b, Fig. 2a, Fig. 2b, Fig. 2c, Fig. 2d, Fig. 3, Fig. 4 and Fig. 5, wherein the reference numerals identify the following exemplary and optional components:

[0427] 100 Exemplary multi-port directional coupler

[0428] 101 Exemplary first dielectric slab, lying in exemplary first plane

[0429] 101a Exemplary first side of first dielectric slab

[0430] 102 Exemplary second dielectric slab, lying in exemplary first plane

[0431] 102a Exemplary first side of second dielectric slab

[0432] 103 Exemplary first rod / first dowel

[0433] 103a Exemplary longitudinal axis of first rod / first dowel, lying in exemplary second plane

[0434] 104 Exemplary second rod / second dowel

[0435] 104a Exemplary longitudinal axis of second rod / second dowel, lying in exemplary third plane Exemplary gap, e.g. air gap, between first dielectric slab and second dielectric slaba Exemplary longitudinal axis along gap or interface between first dielectric slab and second dielectric slab Exemplary incoming signal Exemplary reflected signal Exemplary transmitted signal Exemplary three-dimensional orthogonal coordinate system Exemplary half-mirror Exemplary multi-port directional coupler Exemplary first dielectric slab, lying in exemplary first plane a Exemplary first side of first dielectric slab Exemplary second dielectric slab, lying in exemplary first plane a Exemplary first side of second dielectric slab Exemplary first rod / first dowel a Exemplary longitudinal axis of first rod / first dowel, lying in exemplary second plane Exemplary second rod / second dowel Exemplary interface or region or contact surface between first dielectric slab and second dielectric slab a Exemplary longitudinal axis along interface between first dielectric slab and second dielectric slab a Exemplary longitudinal axis of second rod / second dowel, lying in exemplary third plane Exemplary incoming signal Exemplary reflected signal Exemplary transmitted signal Exemplary half-mirror Exemplary multi-port directional coupler Exemplary first dielectric slab, lying in exemplary first plane a Exemplary first side of first dielectric slab Exemplary second dielectric slab, lying in exemplary first plane a Exemplary first side of second dielectric slab Exemplary first rod / first dowel a Exemplary longitudinal axis of first rod / first dowel, lying in exemplary second plane Exemplary second rod / second dowel a Exemplary longitudinal axis of second rod / second dowel, lying in exemplary third plane 305 Exemplary gap, e.g. air gap, between first dielectric slab and second dielectric slab

[0436] 305a Exemplary longitudinal axis along gap or interface between first dielectric slab and second dielectric slab

[0437] 306 Exemplary incoming signal I exemplary injected signal, exemplary arrow indicating injection of incoming signal

[0438] 307 Exemplary reflected signal, arrow indicating reflected signal

[0439] 308 Exemplary transmitted signal, arrow indicating transmitted signal

[0440] 310 Exemplary half-mirror

[0441] 311 Exemplary first port, P1

[0442] 311a Exemplary first signal launcher

[0443] 312 Exemplary second port, P2

[0444] 312a Exemplary second signal launcher

[0445] 313 Exemplary third port, P3

[0446] 313a Exemplary third signal launcher

[0447] 314 Exemplary fourth port, P4

[0448] 314a Exemplary fourth signal launcher

[0449] 315 Exemplary injection angle, exemplary angle at which a signal is injected into dielectric slab 301

[0450] 400 Exemplary multi-port directional coupler

[0451] 401 Exemplary first dielectric slab, lying in exemplary first plane

[0452] 401a Exemplary first side of first dielectric slab

[0453] 402 Exemplary second dielectric slab, lying in exemplary first plane

[0454] 402a Exemplary first side of second dielectric slab

[0455] 403 Exemplary first rod / first dowel

[0456] 403a Exemplary longitudinal axis of first rod / first dowel, lying in exemplary second plane

[0457] 404 Exemplary second rod / second dowel

[0458] 404a Exemplary longitudinal axis of second rod / second dowel, lying in exemplary third plane

[0459] 405 Exemplary interface or region or contact surface between first dielectric slab and second dielectric slab

[0460] 405a Exemplary longitudinal axis along interface between first dielectric slab and second dielectric slab

[0461] 406 Exemplary incoming signal I exemplary injected signal, exemplary arrow indicating injection of incoming signal

[0462] 407 Exemplary reflected signal, arrow indicating reflected signal

[0463] 408 Exemplary transmitted signal, arrow indicating transmitted signal Exemplary half-mirror Exemplary first port, P1 a Exemplary first signal launcher Exemplary second port, P2 a Exemplary second signal launcher Exemplary third port, P3 a Exemplary third signal launcher Exemplary fourth port, P4 a Exemplary fourth signal launcher Exemplary injection angle, exemplary angle at which a signal is injected into dielectric slab 401 Exemplary multi-port directional coupler Exemplary first dielectric slab, lying in exemplary first plane a Exemplary first side of first dielectric slab Exemplary second dielectric slab, lying in exemplary first plane a Exemplary first side of second dielectric slab Exemplary first rod / first dowel Exemplary second rod / second dowel Exemplary gap, e.g. air gap, between first dielectric slab and second dielectric slab, or exemplary interface or region or contact surface between first dielectric slab and second dielectric slab Exemplary half-mirror Exemplary first port, P1 a Exemplary first signal launcher aa Exemplary curved cloven edge Exemplary second port, P2 a Exemplary second signal launcher aa Exemplary curved cloven edge Exemplary third port, P3 a Exemplary third signal launcher aa Exemplary curved cloven edge Exemplary fourth port, P4 a Exemplary fourth signal launcher aa Exemplary curved cloven edge Exemplary scale, exemplary length between ports from different dielectric slabs Exemplary multi-port directional coupler Exemplary first dielectric slab, lying in exemplary first plane a Exemplary first side of first dielectric slab Exemplary second dielectric slab, lying in exemplary first plane a Exemplary first side of second dielectric slab Exemplary first rod / first dowel a Exemplary longitudinal axis of first rod / first dowel, lying in exemplary second plane Exemplary second rod / second dowel a Exemplary longitudinal axis of second rod / second dowel, lying in exemplary third plane Exemplary gap, e.g. air gap, between first dielectric slab and second dielectric slab, or exemplary interface or region or contact surface between first dielectric slab and second dielectric slab a Exemplary longitudinal axis along gap or interface between first dielectric slab and second dielectric slab Exemplary incoming signal I exemplary injected signal, exemplary arrow indicating injection of incoming signal a Exemplary beam width of injected signal Exemplary reflected signal, arrow indicating reflected signal a Exemplary beam width of reflected signal Exemplary transmitted signal, arrow indicating transmitted signal a Exemplary beam width of transmitted signal Exemplary half-mirror Exemplary first port, P1 a Exemplary first signal launcher, exemplary tapered dielectric rod waveguide Exemplary second port, P2 a Exemplary second signal launcher, exemplary tapered dielectric rod waveguide Exemplary third port, P3 a Exemplary third signal launcher, exemplary tapered dielectric rod waveguide Exemplary fourth port, P4 a Exemplary fourth signal launcher, exemplary tapered dielectric rod waveguide Exemplary graph, exemplary S-parameter graph Exemplary abscissa axis in units of gigahertz (GHz) Exemplary ordinate axis in units of decibel (dB) Exemplary S11 curve, amplitude |S111 704 Exemplary S21 curve, amplitude |S21 |

[0464] 705 Exemplary S31 curve, amplitude |S31 |

[0465] 705 Exemplary S41 curve, amplitude |S41 |

[0466] 800 Exemplary multi-port directional coupler

[0467] 801 Exemplary first dielectric slab, lying in exemplary first plane

[0468] 801a Exemplary first side of first dielectric slab

[0469] 802 Exemplary second dielectric slab, lying in exemplary first plane

[0470] 802a Exemplary first side of second dielectric slab

[0471] 803 Exemplary first rod / first dowel

[0472] 804 Exemplary second rod / second dowel

[0473] 805 Exemplary interface or region or gap or contact surface between first dielectric slab and second dielectric slab

[0474] 806 Exemplary incoming signal I exemplary injected signal, exemplary arrow indicating injection of incoming signal

[0475] 807 Exemplary reflected signal, arrow indicating reflected signal

[0476] 808 Exemplary transmitted signal, arrow indicating transmitted signal, exemplary first transmitted signal at exemplary first frequency

[0477] 808’ Exemplary transmitted signal, arrow indicating transmitted signal, exemplary second transmitted signal at exemplary second frequency

[0478] 808” Exemplary transmitted signal, arrow indicating transmitted signal, exemplary third transmitted signal at exemplary third frequency

[0479] 810 Exemplary half-mirror

[0480] 811 Exemplary first port, P1

[0481] 811a Exemplary first signal launcher

[0482] 812 Exemplary second port, P2

[0483] 812a Exemplary second signal launcher

[0484] 813 Exemplary first coupled port, P3

[0485] 813’ Exemplary second coupled port, P3’

[0486] 813” Exemplary third coupled port, P3”

[0487] 813a Exemplary signal launcher of port 813, P3

[0488] 813a’ Exemplary signal launcher of port 813’, P3’

[0489] 813a” Exemplary signal launcher of port 813”, P3”

[0490] 814 Exemplary fourth port, P4

[0491] 814a Exemplary signal launcher of port 814, P4 Exemplary multi-port directional coupler Exemplary first dielectric slab, lying in exemplary first plane a Exemplary first side of first dielectric slab Exemplary second dielectric slab, lying in exemplary first plane a Exemplary first side of second dielectric slab Exemplary third dielectric slab a Exemplary first half of third dielectric slab b Exemplary second half of third dielectric slab Exemplary interface or region or gap between first dielectric slab and second dielectric slab Exemplary incoming signal Exemplary reflected signal Exemplary transmitted signal Exemplary half-mirror

Claims

CLAIMS1. Multi-port directional coupler (100) for broadband communication applications, comprising: a half-mirror (110), comprising: a first dielectric slab (101) and a second dielectric slab (102); wherein the first dielectric slab (101) and the second dielectric slab (102) are arranged adjacently in a first plane, and wherein the first dielectric slab (101) and the second dielectric slab (102) each comprise at least one port.

2. Multi-port directional coupler (100, 200) according to claim 1 , wherein the permittivity of the first dielectric slab (101) is equal to the permittivity of the second dielectric slab (102) or wherein the permittivity of the first dielectric slab (201) is different from the permittivity of the second dielectric slab (202).

3. Multi-port directional coupler (900) according to one of the preceding claims, wherein a gap (905), e.g. an air gap, is formed between a first side (901a) of the first dielectric slab (901) and a first side (902a) of the second dielectric slab (902), and wherein the multi-port directional coupler (900) further comprises a third dielectric slab (903) that is arranged such that it passes through the gap (905) and wherein said third dielectric slab (903) has an orientation that is perpendicular to the first dielectric slab (901) and the second dielectric slab (902).

4. Multi-port directional coupler (100, 200) according to claim 1 or claim 2, further comprising: a first rod (103) arranged in a second plane and a second rod (104) arranged in a third plane; wherein the first plane and the second plane and the third plane are parallel to each other and wherein the first plane lies between the second plane and the third plane; and wherein a longitudinal axis (103a) of the first rod and a longitudinal axis (104a) of the second rod are arranged parallel and opposite to each other; and wherein said longitudinal axes (103a, 104a) of the first rod and the second rod are arranged parallel to and opposite to a longitudinal axis (105a) lying between a first side (101a) of the first dielectric slab and a first side (102a) of the second dielectric slab.

5. Multi-port directional coupler (100) according to claim 4, wherein a gap (105), e.g. an air gap, is formed between a first side (101a) of the first dielectric slab and a first side (102a) of the second dielectric slab and wherein the longitudinal axes (103a, 104a) of the first rod and the second rod are arranged parallel to and opposite to a longitudinal axis (105a) lying in the gap or a multi-port directional coupler (100) according to claim 1 or claim 2, wherein no gap or nearly no gap is formed at an interface (205) between a / the first side (201a) of the first dielectric slab and a / the first side (202a) of the second dielectric slab.

6. Multi-port directional coupler (200) according to one of the preceding claims 1 or 2 or 4, wherein no gap or nearly no gap is formed at an interface (205) between a / the first side (201a) of the first dielectric slab and a / the first side (202a) of the second dielectric slab and wherein the longitudinal axes (203a, 204a) of the first rod and the second rod are arranged parallel to and opposite to a longitudinal axis (205a) lying along the interface between the first side (201a) of the first dielectric slab and the first side (202a) of the second dielectric slab, and wherein the permittivity of the first dielectric slab (201) can be different from the permittivity of the second dielectric slab (202).

7. Multi-port directional coupler (100, 200) according to one of the preceding claims 3 to 6, wherein the first rod and the second rod have a cylindrical shape and / or wherein the material of the first rod and the material of the second rod comprises a conductive material, e.g. a metallic material.

8. Multi-port directional coupler (100, 200, 500, 600) according to one of the preceding claims, wherein the first dielectric slab and the second dielectric slab are planar slabs and have a rectangular shape, and / or wherein the operating frequency of the multi-port directional coupler lies in the range of 1 GHz to 1 THz, and / or wherein the at least one port of the exemplary multi-port directional coupler is configured as a dielectric rod waveguide, or wherein all ports of the exemplary multi-port directional coupler are configured as dielectric rod waveguides.

9. Multi-port directional coupler (300, 400, 500, 600) according to one of the preceding claims, wherein the multi-port directional coupler is configured as a four-port directional coupler comprising four ports, wherein each of the two adjacent dielectric slabs comprises two ports, and wherein a first port is configured as input port, a second port is configured as transmitted port, a third port is configured as coupled port and a fourth port is configured as isolated port.

10. Multi-port directional coupler (800) according to one of the preceding claims 1 to 8, wherein the permittivity of the first dielectric slab (801) is different from the permittivity of the second dielectric slab (802), and wherein the first dielectric slab comprises a first port that is configured as input port (811) and a second port (812) that is configured as transmitted port, and wherein the second dielectric slab comprises at least two further ports that are configured as coupled ports (813, 813’, 813”).

11. Multi-port directional coupler (300, 400, 500, 600, 800) according to one of the preceding claims, further comprising a plurality of signal launchers, wherein each signal launcher is spatially associated to one specific port of the multi-port directional coupler and wherein at least one signal launcher is configured for collimating electromagnetic wave signals received from external sources and wherein said at least one signal launcher is further configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs, wherein, in particular, the at least one signal launcher is configured for injecting the received electromagnetic wave signals into at least one of the dielectric slabs in the form of a single two-dimensional beam for all operating frequencies.

12. Multi-port directional coupler (300, 400, 500, 600, 800) according to the preceding claim, wherein the first dielectric slab and the second dielectric slab are planar slabs and have a rectangular shape, and wherein the multi-port directional coupler comprises a plurality of ports, with each port having a signal launcher, and wherein the signal launchers and ports are located at or near the corners of the dielectric slabs, wherein said corners are the corners of the dielectric slabs that are located not on the first side of the first dielectric slab and not located on the first side of the second dielectric slab; and / or wherein at least one port is configured as a dielectric rod waveguide port.

13. Multi-port directional coupler (300, 400, 500, 600, 800) according to one of claims 11 or 12, wherein the signal launchers are of one of the following types: total internal reflection reflectors, e.g. total internal reflection parabolic reflectors, planar elliptic or flat mirrors, and / or tapered dielectric rod waveguides.

14. Multi-port directional coupler (300, 400, 500, 600, 800) according to one of the preceding claims, wherein the first dielectric slab and the second dielectric slab have the same size and the same dimensions, or a multi-port directional coupler (300, 400, 500, 600, 800) according to one of claims 3 to 13 wherein the first rod and the second rod have the same size and thesame dimensions and wherein the first dielectric slab and the second dielectric slab have the same size and the same dimensions.

15. Device for broadband communication applications comprising at least one multi-port directional coupler according to one of the preceding claims, wherein the device can be, for example, of one of the following types: a network analyzer, e.g. a vector network analyzer, a transceiver a spectrometer or an image detector.

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