Radio frequency device

Technical Field

The invention relates to a radio frequency device with an incoming transmission line and with a transition structure comprising a length matching transition line segment that allows for a transition of a radio frequency signal from incoming transmission line into a transitioned di f ferential pair transmission line with two transitioned di f ferential pair transmission line segments that run parallel and at a distance towards each other, whereby the radio frequency device comprises a substrate layer arrangement with a first substrate layer, whereby at least one incoming transmission line segment of the incoming transmission line is arranged on a first surface of a first substrate layer of the substrate layer arrangement , and whereby the first transitioned di f ferential pair transmission line segment is galvanically connected to the incoming transmission line segment of the incoming transmission line .

Background of the invention

Radio frequency devices that allow for the signal transmission of radio frequency signals are used within many fields of applications . Due to the increasing amount of data communication, radio frequency devices are also used as parts of data communication devices and in particular as phased array antennas that allow for a controlled variable direction of signal emission and signal reception between two data communication devices.

The radio frequency signals that are processed within the radio frequency devices can be transmitted e.g. along waveguides or planar transmission lines. In order to provide for an efficient processing and transmission of the radio frequency signals, it is favorable to be able to switch between different modes of signal transmission, e.g. to switch form signal transmission along e.g. an unbalanced microstrip transmission line segment to signal transmission along a balanced transmission line segment like e.g. a differential line type of transmission line. In order to perform such a switch a transition structure is required that efficiently transfers the signal transmission between different modes of signal transmission.

US 8,022,887 discloses a radio frequency device that comprises a transition structure that provides for a transfer of a signal transmission along an unbalanced microstrip transmission line segment into a signal transmission along a balanced transmission line comprising two coplanar transmission line segments. The first and second balanced transmission line segment, i.e. the two coplanar transmission line segments are arranged at the same surface of a substrate layer. However, for some applications it is considered favorable to provide for the first and second balanced transmission line segment to be arranged on different surfaces . It is known from prior art to provide for a galvanic connection like e . g . a metallic wire or pin that galvanically connects transmission line segments that are arranged at di f ferent surfaces either of the same substrate layer or of di f ferent substrate layers . However, manufacturing such galvanic connections requires additional manufacturing steps and suf ficient precision to provide for a mechanical connection of di f ferent surfaces . Furthermore , i f the galvanic connection passes through a substrate layer additional manufacturing steps for creating holes or a passage through the substrate layer are required .

Thus , there is a need to provide for a transition structure that allows for the transition of a radio frequency signal from an incoming transmission line into a di f ferential pair transmission line with first and second di f ferential pair transmission line segments being arranged on di f ferent surfaces of the substrate layer arrangement that are easy to manufacture .

Summary of the invention

The present invention relates to a radio frequency device with a transition structure as described above , whereby a second transitioned di f ferential pair transmission line segment is arranged at a second surface within the substrate layer arrangement that is at a distance to the fist surface , whereby the transition structure comprises an coupling region in which the second transitioned di f ferential pair transmission line segment comprises an overlapping section that overlaps with the incoming transmission line so that the overlapping section provides for a capacitive signal coupling between the incoming transmission line and the second transitioned di f ferential pair transmission line segment , and whereby the transition structure also comprises the length matching transition line segment that is galvanically connected with and runs into either the first or second transitioned di f ferential pair transmission line segment and that is arranged on the same first or second surface as the first or second transitioned di f ferential pair transmission line segment into which the length matching transition line segment runs into , whereby the length matching transition line segment provides for a 180 ° phase di f ference between radio frequency signals of the first transitioned di f ferential pair transmission line segment and the second transitioned di f ferential pair transmission line segment after the capacitive coupling within the overlapping region . It is considered a main benefit of the transition structure according to the invention that there is no need for a galvanic connection between the incoming transmission line segment on the first surface to the second transitioned di f ferential pair transmission line segment that is arranged on a di f ferent surface within the substrate layer arrangement . For example , the first substrate layer may be made of glass , and there is no need to provide for a galvanic cross-over that traverses the glass layer from the first surface to a second surface that is opposite to the first surface . Even in case that there is no transition required that traverses a glass layer, any galvanic cross-over between di f ferent surfaces within a substrate layer arrangement requires signi ficant ef forts during manufacturing and results in increasing expenses . It has been found that an overlapping section within the transition structure provides for a very ef fective signal coupling that enables to begin with signal transmission along an incoming transmission line segment and to continue with signal transmission along a transitioned di f ferential pair transmission line after the transition structure without undue loss of signal strength . The length of the overlapping section of the length matching transition line segment and the lateral dimensions of the overlapping section may be adapted to optimi ze the signal transition characteristics within the transition structure and thus the intensity of the capacitively transitioned di f ferential pair signal that is transmitted along the transitioned di f ferential pair transmission line . Furthermore , the intensity of the signal that is outcoupled from the incoming transmission line and coupled into the transitioned di f ferential pair transmission line can be preset by appropriately adapting and designing the overlapping section within the coupling region, which also allows for the arrangement of several transition structures along an incoming transmission line and the repeated outcoupling of a radio frequency signal from the incoming transmission line .

The length matching transition line segment provides for a predetermined delay of the signal transmission along the length matching transition line segment when compared to the signal transmission into the transitioned di f ferential pair transmission line without the length matching transition line segment , resulting in a 180 ° phase shi ft of the signal transmission along the length matching transition line segment with respect to the signal transmission into the transitioned di f ferential pair transmission line segment without the length matching transition line segment . For many applications such a delay may be caused by a longer length of the length matching transition line segment when compared to the length of the other transitioned differential pair transmission line segment. Thus, usually the length matching transition line segment runs along a U-shaped, J-shaped or meandering course compared to a straight-line course of the other segment.

Many well-known transition structures require several vias, namely galvanic connections between substrate layers that go through the plane of one or more adjacent substrate layers. Contrary thereto, the transition structure according to this invention does not require such vias and does not require a galvanic connection between the two transition line segments, i.e. between the length matching transition line segment and the overlapping transition line segment.

The transition structure with the capacitive coupling allows for the transition of a radio frequency signal from several different types of incoming transmission lines into a transitioned differential pair transmission line with corresponding transmission line segments on different surfaces of a substrate layer arrangement. The type of the incoming transmission line can be either an unbalanced incoming transmission line or a balanced incoming transmission line. Thus, the incoming transmission line can be e.g. a microstrip transmission line or a differential pair transmission line with preferably both, i.e. first and second differential pair transmission line segments on the same surface of a substrate layer. The arrangement of the first and second transitioned differential pair transmission line segments on different surfaces within a substrate layer arrangement allows for many more options during manufacture and subsequent use of such a radio frequency device. In particular, it is possible to arrange for a tunable dielectric material in between the two di f ferent surfaces of the first and second transitioned di f ferential pair transmission line segments which allows for the manufacture and use of the transitioned di f ferential pair transmission line as phase shi fting device for the radio frequency signal that is transmitted along the transitioned di f ferential pair transmission line .

According to a favorable embodiment of the invention, the incoming transmission line is an microstrip transmission line comprising an incoming microstrip line segment and an incoming ground electrode layer, whereby the incoming microstrip line segment is arranged on the first surface of the first substrate layer of the substrate layer arrangement and forms the incoming transmission line segment of the incoming transmission line that is galvanically connected with the first transitioned di f ferential pair transmission line segment , and whereby the ground electrode layer is arranged at a distance to the first surface of the first substrate layer and is galvanically isolated from the second transitioned di f ferential pair transmission line segment . The ground electrode layer can be arranged on the second surface and thus on the same surface as the second transitioned di f ferential pair transmission line segment . However, for many applications it is favorable that the ground electrode layer is arranged at a third surface . Preferably, the third surface is located on an outer layer of the substrate layer arrangement and provides for an electrical shielding of the incoming transmission line and in some cases also of the transitioned di f ferential pair transmission line with respect to the surroundings . The ground electrode layer is usually required for enabling the signal transmission along the unbalanced microstrip transmission line segment . However, the ground electrode layer is usually not required for the signal transmission along the transitioned di f ferential pair transmission line segment . Thus , according to an embodiment of the invention, the ground electrode layer is limited to a region that does not overlap with the transitioned di f ferential pair transmission line . This facilitates the manufacture and arrangement of additional components nearby or along the transitioned di f ferential pair transmission line segments . I f a shielding is required or deemed advantageous , such a shielding can be provided by other means and not necessarily by the ground electrode layer .

According to an aspect of the invention, the length matching transition line segment galvanically connects the microstrip transmission line segment with the first di f ferential pair transmission line segment , and the overlapping section of the second transitioned di f ferential pair transmission line segment overlaps with the incoming microstrip transmission line segment . Each of the microstrip transmission line segment , the length matching transition line segment and the first transitioned di f ferential pair transmission line segment are arranged at the first surface of the first substrate layer . Thus , each of these line segments may be manufactured within a single manufacturing step that modi fies the first surface e . g . by evaporate deposition or printing electroconductive line segments onto the first surface of the first substrate layer . The second transitioned transmission line segment only requires a section, preferably an end section, that forms the overlapping section that overlaps within the coupling region of the transition structure with the incoming microstrip transmission line segment and that then runs into an outgoing section of the transitioned di f ferential pair transmission line .

In yet another embodiment of the invention, the length matching transition line segment is galvanically connected to the second transitioned di f ferential pair transmission line segment and arranged between the overlapping section and an outgoing section of the second transitioned di f ferential pair transmission line segment . Thus , the length matching transition line segment can be formed either as part of the first transitioned di f ferential pair transmission line segment or as part of the second transitioned di f ferential pair transmission line segment . The arrangement of the length matching transition line segment requires some space . Thus , the arrangement and position of the length matching transition line segment can be chosen in order to meet space requirements with respect to additional components of the radio frequency device or in such a manner as to reduce unwanted reflections or radiation away from the transitioned di f ferential pair transmission line .

According to a very favorable aspect of the invention, the incoming transmission line is an incoming di f ferential pair transmission line comprising a first incoming di f ferential pair transmission line segment and a second incoming di f ferential pair transmission line segment , whereby at least the first incoming di f ferential line transmission line segment is arranged on the first surface of the first substrate layer of the substrate layer arrangement and forms the incoming transmission line segment of the incoming transmission line that is galvanically connected with the first transitioned di f ferential pair transmission line segment . Usually, both the first incoming di f ferential pair transmission line segment as well as the second incoming di f ferential pair transmission line segment are arranged on the same surface of the same substrate layer . The transition structure with the capacitive coupling of the second transitioned di f ferential pair transmission line segment allows for a coupling into the transitioned di f ferential pair transmission line with first and second transitioned di f ferential pair transmission line segments on two di f ferent surfaces . Thus , the switch from an arrangement of corresponding transmission line segments on the same surface to the arrangement on two di f ferent surfaces can facilitate or enable for additional possibilities for the design and the function of the radio frequency device . The capacitive coupling allows for an easy and cost-ef fective manufacture of the transition structure without need for a galvanic connection and a mechanical modi fication of the substrate layer by adding e . g . a reach-through through a substrate layer or by adding wires or vias that provide for a galvanic connection of di f ferent levels or surfaces within the substrate layer arrangement .

According to an embodiment of the invention, the overlapping section of the second transitioned di f ferential pair transmission line segment overlaps with the first incoming di f ferential pair transmission line segment that forms the incoming transmission line segment . It is also possible and according to yet another embodiment of the invention, that the overlapping section of the second transitioned differential pair transmission line segment overlaps with the second incoming differential line transmission line segment. The overlapping section of the second transitioned differential pair transmission line segment is arranged on a different surface than the first or second incoming differential pair with which the overlapping section overlaps. Thus, in case that the overlapping section overlaps with the first incoming differential pair transmission line segment, the second transitioned differential pair transmission line segment is arranged on a different surface than the first incoming differential pair transmission line segment. Similarly, if the overlapping section overlaps with the second incoming differential pair transmission line segment, the second transitioned differential pair transmission line segment is arranged on a different surface than the second incoming differential pair transmission line segment. Thus, by selecting the first or second incoming differential pair transmission line segment as match for the overlapping section it is possible to make use of different surfaces that are used for the transitioned differential pair transmission line, which might be useful for the intended design of the radio frequency device and the position and arrangement of additional components.

According to a favorable aspect of the invention, the width of the incoming transmission line segment of the incoming transmission line within a matching region that is arranged along the direction of signal transmission before the incoming transmission line runs into the coupling region is different from and preferably smaller than the width of the corresponding section of the incoming transmission line segment of the incoming transmission line that runs into the coupling region . A variation of the width of the incoming transmission line segment allows for minimi zing unwanted reflections or signal loss when entering into the coupling region of the transition structure . The design of the incoming transmission line segment within the matching region is adapted to optimi ze the signal transmission through the transition structure and into the transitioned di f ferential pair transmission line . It is also possible to adapt the width of the second incoming di f ferential pair transmission line segment to reduce unwanted reflection or signal loss within the coupling region of the transition structure .

According to yet another aspect of the invention, the transition structure comprises a crossing region in which the second transitioned di f ferential pair transmission line segment on the second surface traverses the course of the incoming transmission line segment on the first surface , whereby the width of incoming transmission line segment within the crossing region is less than 1 / 4 and preferably less than 1 / 5 of the width of the incoming transmission line segment at a distance from the crossing region . Due to the arrangement on di f ferent surfaces within the substrate layer arrangement , the second transitioned di f ferential pair transmission line segment is galvanically isolated from the incoming transmission line segment . However, in order to minimi ze interference and disturbance of the radio frequency signals that are transmitted along the incoming transmission line and along the transitioned di f ferential pair transmission line , an overlapping area between the incoming transmission line segment and the traversing second transitioned di f ferential pair transmission line segment is reduced by reducing the width of the incoming transmission line segment . Preferably, also the width of the second transitioned di f ferential pair transmission line segment is less than twice the width of the incoming transmission line segment within the crossing region, or even similar or preferably less than the width of the incoming transmission line segment within the crossing region . According to a preferred embodiment of the transition structure , the width of the incoming transmission line segment is approx . 50 micrometers and the width of the traversing second transitioned di f ferential pair transmission line segment is similar thereto . In general , the overlapping area should be small with respect to the overlapping area of the overlapping section within the coupling region . Preferably, the overlapping area within the crossing region should be small enough so that there will be no or only a marginal signal coupling within the crossing region that interferes with the transition of the radio frequency signal from the incoming transmission line into the transitioned di f ferential pair transmission line .

According to a favorable aspect of the invention, the overlapping section of the second transitioned di f ferential pair transmission line segment that overlaps with the incoming transmission line segment is parallel to and directed in the direction of the incoming transmission line segment of the incoming transmission line . A parallel course and direction of the overlapping section enhances the capacitive coupling between the incoming transmission line segment and the overlapping section of the second transitioned di f ferential pair transmission line segment and thus strengthens the signal coupling and the signal intensity that is transmitted along the transitioned di f ferential pair transmission line . Preferably, the direction of the overlapping section at the beginning of the second transitioned di f ferential pair transmission line segment equals the direction of the signal transmission along the incoming transmission line segment of the incoming transmission line . However, the signal coupling within the overlapping section does not require the overlapping section at the begin of the second transitioned di f ferential pair transmission line segment to run along the direction of the signal transmission along the incoming transmission line segment , but also allows for an orientation and direction that is opposite to the direction of the signal transmission along the incoming transmission line segment . With respect to speci fic embodiments , this might allow for a more compact design of the transition structure .

According to yet another advantageous embodiment of the invention, the first transitioned di f ferential pair transmission line segment is galvanically connected to a first bias voltage line and the second transitioned di f ferential pair transmission line segment is galvanically connected to a second bias voltage line . The first transitioned di f ferential pair transmission line segment is galvanically connected to the incoming transmission line segment . However, as there is no need for a galvanic connection between the incoming transmission line segment and the capacitively coupled second transitioned di f ferential pair transmission line segment in order to provide for the required signal coupling, the first and second transitioned di f ferential pair transmission line segments can be biased separately and independently from each other . Thus , it is possible to provide for a di f ference of the electric potential and thus to create an electric field between the first and second transitioned di f ferential pair transmission line segment . The di f ference in electric potential and the corresponding electric field between the first and second transitioned di f ferential pair transmission line segments can be used to control e . g . a layer of a tunable dielectric material that is arranged in between the first and second transitioned di f ferential pair transmission line segments and preferably in between two substrate layers that confine the tunable dielectric material .

Preferably, the length of the overlapping section of the second transitioned di f ferential pair transmission line segment is adapted to provide for a good signal coupling ef ficiency from the incoming transmission line segment into the second transitioned di f ferential pair transmission line segment and thus into the transitioned di f ferential pair transmission line . For many applications , it is considered favorable that a length of the overlapping section of the second transitioned di f ferential pair transmission line segment is equal or more than X/20 of the wavelength X of the radio frequency signal that is transmitted along the transition structure of the radio frequency device . It has been found that a length of the overlapping section that is less or equal X/ 8 of the wavelength X of the radio frequency signal is usually suf ficient for the required signal coupling but does not require much space for the transition structure . However, it is also possible to predefine the length of the overlapping section to be any value between X/ 32 and X/2 or to be even larger, depending on the fraction of the intensity of the incoming radio frequency signal that shall be coupled into the transitioned di f ferential pair transmission line . Usually, the longer the length of the overlapping section, the greater the intensity of signal transition from the incoming transmission line into the transitioned di f ferential pair transmission line will be . Similarly, the lateral overlapping also af fects the amount of coupling intensity as well . I f there are several transition structures arranged along the incoming transmission line with repeated signal transitions into the respective transitioned di f ferential pair transmission lines that branch of f from the incoming transmission line , the length or the lateral overlap or both parameters of the respective overlapping sections of the successive transition structures can be preset and designed to outcouple a similar signal intensity within each of the successive transition structures , which requires a di f ferent length or lateral overlap of the overlapping sections within the successive transition structures .

According to yet another embodiment of the invention, the radio frequency device comprises a second substrate layer arranged at a distance to the first substrate layer, whereby the second surface is arranged on the second substrate layer . Due to the signal coupling within the transition structure that does not require any galvanic connection, the second surface can be arranged on a second substrate layer that is at a distance to the first layer . The second substrate may be made from the same material or a di f ferent material than the first substrate layer . For many applications related to phased array antennas it is considered advantageous to provide for the first substrate layer and the second substrate layer to be made from glass , resulting in a transparent structure . For example , such a transparent structure may be used to create a phased array antenna with a large number of transition structures , phase shi fting units and radiation emission units that allow for a controllable direction of signal transmission or signal reception with respect to the orientation of the phased array antenna . Such a phased array antenna may have a footprint of approx , one square meter or less and can be arranged on a surface of obj ects without interfering with the design or aesthetical perception of these obj ects . Furthermore , such phased array antennas may be arranged on transparent obj ects like e . g . windows or transparent car roofs without signi ficantly interfering with the transparency of such obj ects , which favors and increases the user acceptance for using large scale phased array antennas .

According to a very advantageous aspect of the invention the radio frequency device comprises at least one layer of a tunable dielectric material that is arranged between the first and second substrate layer and that extends at least partly over the transitioned dielectric pair transmission line . The dielectric properties of the tunable dielectric material can be controlled and modi fied in order to af fect the signal transmission along the transmission lines . Preferably, the tunable dielectric material is a liquid crystal material which can be tuned by application of an electric field with di f ferent field strength to the liquid crystal material . By modi fying the tunable dielectric material , the dielectric properties in the vicinity of the electrical conductors that form the respective transmission lines will be modi fied accordingly which af fects the signal transmission along the transmission lines . Thus , it is possible to provide for transmission lines that can be used as phase shi fting devices , whereby the phase relationship between the incoming radio frequency signal and the outgoing radio frequency signal can be controlled by appropriate tuning of the tunable dielectric material . For many applications it is considered advantageous to provide for a layer of a tunable dielectric material that is sandwiched by the first and second substrate layer and that is arranged between the first and second transitioned di f ferential pair transmission line segments , as the transitioned di f ferential pair transmission line allows for easy manufacture and operation of e . g . a phase shi fting device with tunable phase shi fting characteristics .

The extension of the layer of the tunable dielectric material may be limited to a region in the vicinity of the transitioned di f ferential pair transmission line segment .

Brief description of the drawings

The present invention will be more fully understood, and further features will become apparent , when reference is made to the following detailed description and the accompanying drawings . The drawings are merely representative and are not intended to limit the scope of the claims . In fact , those of ordinary skill in the art may appreciate upon reading the following speci fication and viewing the present drawings that various modi fications and variations can be made thereto without deviating from the innovative concepts of the invention . Like parts depicted in the drawings are referred to by the same reference numerals . Figure 1 illustrates a schematic top view representation of a part of a radio frequency device with an incoming microstrip transmission line, with a transition structure and with a transitioned differential pair transmission line as outgoing transitioned transmission line,

Figure 2 illustrates a schematic sectional view along the line II-II in Figure 1 showing the incoming microstrip transmission line,

Figure 3 illustrates a schematic sectional view along the line III-III in Figure 1 showing the transitioned differential pair transmission line,

Figure 4 illustrates a schematic representation of a part of the radio frequency device with an incoming microstrip transmission line, with a transition structure and with a transitioned differential pair transmission line and an outgoing remaining microstrip transmission line,

Figure 5 illustrates a schematic representation of a part of the radio frequency device with an incoming differential pair transmission line, with a transition structure and with a transitioned differential pair transmission line and a remaining outgoing differential pair transmission line,

Figure 6 illustrates a schematic sectional view along the line VI-VI in Figure 5 showing the incoming microstrip transmission line, Figure 7 illustrates a schematic sectional view along the line VI I-VI I in Figure 5 showing the transitioned di f ferential pair transmission line ,

Figure 8 illustrates a schematic sectional view along the line VI I I-VI I I in Figure 5 showing the remaining outgoing di f ferential pair transmission line ,

Figure 9 illustrates a top view of a radio frequency device with a substrate layer arrangement comprising an incoming microstrip transmission line segment , a transition structure and a transitioned di f ferential pair transmission line with two transitioned di f ferential pair transmission line segments that run parallel and at a distance towards each other,

Figure 10 illustrates a sectional view of a part of the radio frequency device along the line X-X in figure 9 showing the incoming microstrip transmission line of the radio frequency device ,

Figure 11 illustrates a sectional view of a part of the radio frequency device along the line XI-XI in figure 9 showing the transition structure of the radio frequency device ,

Figure 12 illustrates a sectional view of a part of the radio frequency device along the line XI I-XI I in figure 9 showing the transitioned di f ferential pair transmission line of the radio frequency device ,

Figure 13 illustrates a top view of another embodiment of the radio frequency device with the substrate layer arrangement comprising the microstrip transmission line segment , another embodiment of the transition structure and the balanced transmission line with two balanced transmission line segments that run parallel and at a distance towards each other,

Figure 14 illustrates a sectional view of a part of the radio frequency device along the line XIV-XIV in figure 13 showing the incoming microstrip transmission line of the radio frequency device ,

Figure 15 illustrates a sectional view of a part of the radio frequency device along the line XV-XV in figure 13 showing the transition structure of the radio frequency device ,

Figure 16 illustrates a sectional view of a part of the radio frequency device along the line XVI-XVI in figure 13 showing the balanced transmission line of the radio frequency device ,

Figure 17 illustrates a top view of a radio frequency device with a substrate layer arrangement comprising an incoming di f ferential pair transmission line , a transition structure , a transitioned di f ferential pair transmission line and a remaining outgoing di f ferential pair transmission line ,

Figure 18 illustrates a schematic sectional view along the line XVI I I-XVI I I in Figure 17 showing the incoming di f ferential pair transmission line ,

Figure 19 illustrates a schematic sectional view along the line XIX-XIX in Figure 17 showing the transitioned di f ferential pair transmission line , Figure 20 illustrates a schematic sectional view along the line XX-XX in Figure 17 showing the remaining outgoing di f ferential pair transmission line , and

Figure 21 illustrates a schematic representation of a top view of a radio frequency device with a transmission line with several transition structures and several transitioned di f ferential pair transmission lines , whereby each transitioned di f ferential pair transmission line is coupled to the same transmission line and whereby each transitioned di f ferential pair transmission line transmits an outgoing coupled radio frequency signal away from an incoming radio frequency signal that is transmitted along the transmission line .

Figures 1 to 8 schematically illustrate di f ferent embodiments of a radio frequency device 1 with a substrate layer arrangement 2 . The radio frequency device 1 also comprises several transmission line segments that are designed and arranged for transmitting a radio frequency signal along the consecutively arranged transmission line segments .

Each of the figures 1 and 4 and 5 illustrates a schematic top view of an embodiment of a radio frequency device 1 with an incoming transmission line and at least one outgoing transmission line . Figures 2 and 3 illustrate sectional views of the embodiment shown in figure 1 , and figures 6 to 8 illustrate several sectional views of the embodiment shown in figure 5 . Many aspects and features of the three embodiments shown in figures 1 and 4 and 5 are similar and will be referenced with same reference numerals . Di f ferences between the two embodiments will be described in the following . The substrate layer arrangement 2 comprises a first substrate layer 3 and a second substrate layer 4 that are arranged parallel and at a distance to each other . Both first and second substrate layer 3 , 4 are made of glass . However, the first and second substrate layer 3 , 4 may also be made of a material that is di f ferent to glass , but that is electrically insulating and provides for a good support and mounting of the several transmission line segments .

The first substrate layer 3 comprises a flat first surface 5 , and the second substrate layer 4 comprises a flat second surface 6 facing the first surface 5 on the first substrate layer 3 . A ground electrode layer 7 that is made from an electroconductive material is arranged on a third surface of the first substrate layer 3 opposing the first surface 5 and facing away from the second substrate layer 4 , resulting in a distance of the ground electrode layer 7 to the first surface 5 of the first substrate layer 3 .

The embodiment of the radio frequency device 1 that is shown in Figure 1 comprises an incoming microstrip transmission line that forms an incoming transmission line 8 , a transition structure 9 and a transitioned di f ferential pair transmission line 10 that are consecutively arranged within the substrate layer arrangement 2 . Transmission line segments are made of an electrically conductive material like e . g . metal or indium tin oxide or a material with characteristics similar thereto . For clari fication purposes , transmission line segments that are arranged at the first surface 5 are illustrated with solid lines and transmission line segments that are arranged at the second surface 6 are illustrated with dashed lines . Obviously, the position of the respective transmission line segments on the first and second surface 5 , 6 can be interchanged provided that the arrangement of the respective transmission line segments with respect to each other is maintained . The ground electrode layer 7 is required for the incoming microstrip transmission line , but not required for the transitioned di f ferential pair transmission line 10 . Thus , the ground electrode layer 7 covers the region of the incoming microstrip transmission line that forms the incoming transmission line 8 . the ground electrode layer 7 may also cover at least a part of or all of the transition structure 9 .

The incoming transmission line 8 comprises an incoming microstrip transmission line segment 11 that is arranged at the first surface 5 of the first substrate layer 3 and faces the second substrate layer 4 . The incoming microstrip transmission line segment 11 and the ground electrode layer 7 form the incoming microstrip transmission line as a speci fic type of incoming transmission line 8 .

The transitioned di f ferential pair transmission line 10 comprises a first transitioned di f ferential pair transmission line segment 12 and a second transitioned di f ferential pair transmission line segment . The first and second transitioned di f ferential pair transmission line segments 12 and 13 run parallel and at a distance towards each other along the substrate layer arrangement 2 and form the transitioned di f ferential pair transmission line 10 that is designed for and intended for a di f ferential pair signal transmission along the transitioned di f ferential pair transmission line 10 . The transition structure 9 comprises a coupling region 14 and a length matching transition line segment 15 . In the embodiment shown in figure 1 , the length matching transition line segment 15 is arranged at the second surface 6 and galvanically isolated from the incoming microstrip transmission line segment 11 . Part of the incoming microstrip transmission line segment 11 runs parallel to an overlapping section 16 of the second transitioned di f ferential pair transmission line segment 13 and at least partially overlaps with said overlapping section 16 of the overlapping section 16 of the second transitioned di f ferential pair transmission line segment 13 . A lateral gap between the incoming microstrip transmission line segment 11 and the overlapping section 16 of the second transitioned di f ferential pair transmission line segment 13 that is visible within the schematic representation of figure 1 is shown for clari fication purposes only . The overlap of the incoming microstrip transmission line segment 11 and the overlapping section 16 of the second transitioned di f ferential pair transmission line segment 13 provides for a capacitive coupling of a signal that is transmitted from the incoming transmission line towards the transition structure 9 . This generates a matched signal transmission along the overlapping section 16 of the second transitioned di f ferential pair transmission line segment 13 that runs parallel to the direction of signal transmission along the incoming microstrip transmission line segment 11 . The incoming microstrip transmission line segment 11 is galvanically connected or runs into the first transitioned di f ferential pair transmission line segment 12 . Thus , a radio frequency signal that is transmitted along the incoming microstrip transmission line segment 11 will continue and will be subsequently transmitted along the first transitioned di f ferential pair transmission line segment 12 .

Due to the shape and course of the length matching transition line segment 15 , both signals will be transmitted to an output side of the transition structure 9 , but with a 180 ° phase shi ft between both signals that are further transmitted along the first and second transitioned di f ferential pair transmission line segments 12 , 13 .

Figure 4 illustrates another embodiment of the radio frequency device 1 . Similar to the embodiment shown in figure 1 , the incoming transmission line 8 is formed by an incoming microstrip transmission line with an incoming microstrip transmission line segment 11 . The transition structure 9 comprises the coupling region 14 and the length matching transition line segment 15 . However, the incoming transmission line segment 11 continues as an outgoing remaining microstrip transmission line 17 . The first transitioned di f ferential pair transmission line segment 12 is galvanically connected to the incoming transmission line segment 11 and the continuing outgoing remaining microstrip transmission line 17 and branches of f from the direction of the incoming microstrip transmission line segment 11 . The second transitioned di f ferential pair transmission line segment 13 begins with the overlapping section 16 that runs into the length matching transition line segment 15 . After the length matching transition line segment 15 the second transitioned di f ferential pair transmission line segment 13 traverses the incoming transmission line segment 11 and the outgoing remaining microstrip transmission line 17 and runs parallel to the first transitioned differential pair transmission line segment 12 that branches off from the incoming microstrip transmission line segment 11. Thus, the embodiment shown in figure 4 comprises one incoming transmission line 8, namely the incoming microstrip transmission line, and two outgoing transmission lines, namely the outgoing remaining microstrip transmission line 17 and the transitioned differential pair transmission line 10.

Figure 5 illustrates yet another embodiment of the radio frequency device 1. The incoming transmission line 8 is formed by an incoming differential pair transmission line 18 comprising a first incoming differential pair transmission line segment 19 and a second incoming differential pair transmission line segment 20. Both, the first and second incoming differential pair transmission line segments 19, 20 are arranged on the first surface 5 of the first substrate layer 3. Both, the first and second incoming differential pair transmission line segments 19, 20 pass through the transition structure 9 and continue as first and second remaining differential pair transition line segments 21, 22 that form an outgoing remaining differential pair transition line 23.

Both, the first and second incoming differential pair transmission line segments 19, 20 are arranged on the first surface 5 of the first substrate layer 3. The second transitioned differential pair transmission line segment 13 is arranged on the second surface 6 on the second substrate layer 4. Within the transition structure 9, the first transitioned differential pair transmission line segment 12 is galvanically connected to the first incoming differential pair transmission line segment 19 and branches off from the first incoming differential pair transmission line segment 19.

Within the transition structure 9, the second transitioned differential pair transmission line segment 13 begins with the overlapping section 16 that overlaps with the second incoming differential pair transmission line segment 20. The second transitioned differential pair transmission line segment 13 then traverses the first incoming differential pair transmission line segment 19 and runs parallel to the first transitioned differential pair transmission line segment 12. After branching off from the incoming differential pair transmission line segment 19, the radio frequency signal that is transmitted away from the first incoming differential pair transmission line segment 19 is then transmitted through the length matching transition line segment 15 that is designed to provide for a 180° phase shift between both signals that are further transmitted along the first and second transitioned differential pair transmission line segments 12, 13.

Figures 9 and 13 illustrate in more detail different embodiments of the radio frequency device similar to the embodiment that is schematically shown in figure 1. Figures 10 to 12 and 14 to 16 illustrate sectional views in order to show the arrangement of the different transmission lines within the respective substrate layer arrangement 2. The substrate layer arrangement 2 comprises a different stacking of first and second substrate layer 3, 4. As before, many aspects and features of the two embodiments shown in Figures 9 and 13 are similar and will be referenced with same reference numerals . Di f ferences between the two embodiments will be described in the following .

In the embodiment that is shown in figures 9 to 12 , the length matching transition line segment 15 is part of and arranged within the second transitioned di f ferential pair transmission line segment 13 . Thus , the length matching transition line segment 15 is arranged on the second surface 6 of the second substrate layer 4 and positioned after the overlapping section 16 of the second transitioned di f ferential pair transmission line segment 13 . The direction of the overlapping section 16 and thus of the begin of the second transitioned di f ferential pair transmission line segment 13 is opposite to the direction of the overlapping section 16 within the embodiment of figure 12 and parallel , but opposite to the direction of signal transmission along the incoming microstrip transmission line segment 11 . However, as long as there is an overlapping section 16 that runs parallel to the course of the incoming microstrip transmission line segment 11 , there will be a capacitive coupling and the formation and transmission of a radio frequency signal along the second transitioned di f ferential pair transmission line segment 13 on the second surface 6 .

The incoming microstrip transmission line segment 11 runs into the first transitioned di f ferential pair transmission line segment 12 that is also arranged at the first surface 5 , thereby forming an electroconductive course along the first surface 5 . The first and second transitioned di f ferential pair transmission line segments 12 , 13 form the transitioned di f ferential pair transmission line 10 . In the embodiment that is shown in figures 13 to 16 , the length matching transition line segment 15 is galvanically connected to the incoming microstrip transmission line segment 11 . The incoming microstrip transmission line segment 11 runs into the length matching transition line segment 15 that is also arranged at the first surface 5 , and the length matching transition line segment 15 then runs into the first transitioned di f ferential pair transmission line segment 12 that is also arranged at the first surface 5 , thereby forming an electroconductive course along the first surface 5 . The second transitioned di f ferential pair transmission line segment 13 is arranged at the second surface 6 and galvanically isolated from the incoming microstrip transmission line segment 11 . The second transitioned di f ferential pair transmission line segment 13 begins with an overlapping section 16 that runs parallel and fully overlapping with the corresponding section of the incoming microstrip transmission line segment 11 at the first surface 5 . The overlap provides for a capacitive coupling and generates a signal within the overlapping section 16 of the second transitioned di f ferential pair transmission line segment 13 that is fed into the transitioned di f ferential pair transmission line 10 , resulting in a di f ferential pair signal transmission along the transitioned di f ferential pair transmission line 10 .

In both embodiments , the length of the overlapping section 14 of the overlapping section 16 that at least partially overlaps with the incoming microstrip transmission line segment 11 is approx . X/ 4 of the wavelength X of the radio frequency signal that is transmitted along the transition structure 9 of the radio frequency device 1 . In both embodiments , the first and second transitioned di f ferential pair transmission line segments 12 , 13 are arranged at di f ferent surfaces 5 , 6 , namely on the first surface 5 of the first substrate layer 3 and on the second surface 6 of the second substrate layer 4 . In between the first and second substrate layer 3 , 4 there is a layer of a tunable dielectric material 24 . Preferably, the tunable dielectric material 24 is a liquid crystal material that can be tuned by an electric field that af fects the orientation of liquid crystal molecules within the liquid crystal material 24 . By generating an electric field within the tunable dielectric material 24 , the dielectric characteristics of the tunable dielectric material 24 can be controlled and modi fied . I f the layer of tunable dielectric material 24 is controlled within the region of the transitioned di f ferential pair transmission line 10 , this may allow for a phase shi fting unit that can be operated by application of the electric field that af fects the layer of tunable dielectric material 24 that is sandwiched between the first and second transitioned di f ferential pair transmission line segment 12 , 13 and thus af fects the phase of the signal transmission along the transitioned di f ferential pair transmission line 10 .

The electric field can be preset by application of a bias voltage via a first bias voltage line 25 and a second bias voltage line 26 that are connected to the first respective second transitioned di f ferential pair transmission line segment 12 , 13 . Figures 17 to 20 illustrate another embodiment of the radio frequency device 1, whereby the incoming transmission line 8 is not a microstrip transmission line, but the incoming differential pair transmission line 18 with the first incoming differential pair transmission line segment 19 and the second incoming differential pair transmission line segment 20. Both, the first and second incoming differential pair transmission line segments 19, 20 run parallel towards each other and are arranged on the first surface 5 of the first substrate layer 3.

Along the course of the incoming differential pair transmission line 18 and before entering into the coupling region 14 there is a matching region 27, whereby the width of the first and second incoming differential pair transmission line segments 19, 20 of the incoming transmission line 8 is different from and preferably smaller than the width of the corresponding sections of the incoming differential pair transmission line segments 19, 20 of the incoming transmission line 8 that runs into the coupling region 14. The width and shape of the first and second incoming differential pair transmission line segments 19, 20 within the matching region 27 is designed to reduce unwanted signal reflections and signal loss of the radio frequency signals that enter into the transition structure 9.

The first transitioned differential pair transmission line segment 12 is galvanically connected to and branches off from the first incoming differential pair transmission line segment 19. The second transitioned differential pair transmission line segment 13 is arranged on the second surface 6 and begins with the overlapping section 16. After the overlapping section 16, the second transitioned differential pair transmission line segment 13 traverses the first incoming differential pair transmission line 19 within a crossing region 28. Within the crossing region 28, the width of the second transitioned differential pair transmission line segment 13 and of the first incoming differential pair transmission line 19 are each significantly smaller than the respective width outside of the crossing region 28. Preferably the width within the crossing region 28 is smaller than 1/4 or smaller than 1/5 than the respective width outside the crossing region 28.

The length matching transition line segment 15 is galvanically connected to the first incoming differential pair transmission line segment 19 and to the first transitioned differential pair transmission line segment 12 that branches off from the first incoming differential pair transmission line segment 19. The design of the length matching transition line segment 15 is preset to provide for a 180° phase shift between both signals that are further transmitted along the first and second transitioned differential pair transmission line segments 12, 13.

Both, the first and second incoming differential pair transmission line segments 19, 20 run parallel towards each other and are arranged on the first surface 5 of the first substrate layer 3, continue after the transition structure 9 as the remaining outgoing differential pair transmission line 23 that is formed by a first and second remaining outgoing differential pair transmission line segment 21, 22. The remaining outgoing differential pair transmission line 23 forms a fully galvanically connected remaining outgoing transmission line in addition to the capacitively connected transitioned differential pair transmission line 10.

Figure 21 schematically illustrates a radio frequency device 1 with an incoming differential pair transmission line 18 that runs along a course within the substrate layer arrangement 2. Along the course of the incoming differential pair transmission line 18, there are several transition structures 9 with corresponding transitioned differential pair transmission lines 10 that branch off from the incoming differential pair transmission line 18. The design of the transition structures 9 can be similar to the design that is illustrated in figures 17 to 20. The successive transitioned differential pair transmission lines 10 are branched from the incoming differential pair transmission line 18 in opposite directions, which allows for a compact design and arrangement of the branching transitioned differential pair transmission lines 10.