Stripline Arrangement and a Method for Production Thereof

FIELD OF THE INVENTION

The present invention relates to a stripline arrangement comprising a number of stripline layers each comprising a laminate layer and conducting layers provided thereon. At least some of the conducting layers comprise a respective conductive pattern and the arrangement further comprises RF/microwave signal input and output ports and an interconnecting arrangement for interconnecting said stripline layers.

The invention also relates to a method for producing a stripline arrangement comprising a number of stripline layers, each of which comprises a laminate layer and conducting layers.

STATE OF THE ART

Stripline arrangements are well known in the art. However, it has always been a problem with the connections of stripline assemblies, e.g. inputs/outputs for example to components and modules having various functionalities. So far a so called 1l-way connection has been used. A 1-way connection is a solution in which all connecting means or connectors are located in one and the same plane. This makes connection to, or integration with, other components complicated and un-necessarily space demanding and it is particularly difficult when it would be desirable to implement for example a so called tile technique which is a vertical building technique in which components or modules etc. are mounted vertically or on top of each other. Hence, so far there has been no satisfactory solution as far as the connections of stripline arrangements are concerned and so far it has e.g. been substantially impossible to design tile products or PCB boards (Printed Circuit Boards) requiring connections on both sides of the boards using the stripline technique.

SUMMARY OF THE INVENTION

What is needed is therefore a stripline arrangement as initially referred to which is easy to design and fabricate. Still further a stripline arrangement is needed which is capable of providing a 2-way connection possibility. Still further an arrangement is needed for which it is possible to provide connectors in different planes, particularly on both sides of a stripline arrangement comprising a stripline board, or PCB board. Still further a stripline arrangement is needed which has low losses, or a low reflection, and which is broad-banded. Particularly a stripline arrangement is needed which has a good controllability. Even more particularly a stripline arrangement is needed which is flexible and which can be used in for example so called tile products or similar compact connection assemblies. Further yet, a stripline arrangement is needed which allows for easy and flexible arranging of functional entities or components in layers on each other. Even more particularly a stripline arrangement is needed which is compact and can be used in or with various components and in which a conductive pattern, particularly a distribution network, easily can be provided not only in a cheap manner but also in a very compact and extremely flexible manner.

Therefore a stripline arrangement as initially referred to is provided wherein at least two of said stripline layers are arranged such that a given overlapping zone is provided between each other facing conducting layers of said stripline layers. The interconnecting arrangement comprises a bonding arrangement provided between adjacent and one another facing and overlapping conducting layers (arranged on different laminate layers). Further, connectors are provided substantially perpendicularly with respect to the extension plane of the respective stripline layer and they cross said laminate layer and its conducting layers for, in said overlapping zone, providing contact between adjacent conducting layers of adjacent stripline layers.

Particularly said laminate layers comprise dielectric layers with a given dielectric constant. The dielectric constant may vary between for example 2 and 200 depending on implementation or application and it is frequency dependent, i.e. it depends on the frequency of input RF signals or microwave signals and it has hence to be adapted, i.e. a material has to be selected which is adecuate for the specific implementation. Particularly it is selected with regard to the signal mid-frequency in order to reduce losses, or reflections, and in order to provide a broadband arrangement with a particularly good controllability. In a particular embodiment the laminate layers comprise ferroelectric layers. One example on a laminate is Rogers 3003™ with a dielectric constant of about 3.

The conducting layers particularly comprise a metal, such as for example Cu, Ag or Au in a conventional manner. The bonding layer may for example comprise a so called prepreg material such as for example ARLON 6250™. The bonding film is particularly matched to the dielectric, or the laminate layers in general, the thinner the board or stripline arrangement, the larger ε has to be selected (i.e. the laminate material) since the wavelength is inversely proportional to the square root of the dielectric constant, (λ_g=c/f×√{square root over (ε)}_r), λ_gbeing the wavelength in the conductor, f the mid-frequency of the frequency band and ε_rbeing the relative dielectric constant.

In an alternative embodiment the bonding arrangement may comprise screws or similar connecting means which substantially are mechanically operative.

Particularly the bonding film, if such is used, between two conducting layers comprises recesses or similar, for example cut-outs, adjacent to or in association with the connectors, such that said recesses or similar at least are provided where connectors protrude from a conducting layer of a stripline layer in order to prevent contact with the conducting layer of the adjacent stripline layer. Most advantageously the connectors are so called connector pins taken up in through holes in the respective stripline layers. Particularly the “head” of the connector pin is soldered onto the conducting layer of the respective stripline layer in which it is taken up.

Most particularly each laminate layer is sandwiched between a first and a second conducting layer.

In an advantageous implementation said input and/or output ports are formed by one or more of said connectors providing vertical input/output ports arranged in different layers (i.e. vertical on condition that the extension plane of the stripline is defined as horizontal, in more general terms perpendicular to said plane of extension). However, the inventive concept according to which an overlap is provided in order to connect stripline layers is not exclusively limited to vertically input/output ports in different layers but may also be implemented with input/output ports in one and the same plane or for example one might be parallel with the planar extension of the stripline arrangement whereas the other is vertically disposed etc. Any variation is in principle possible, but a particularly advantageous embodiment is provided through arranging the connectors on both sides of a stripline arrangement or a PCB (Printed Circuit Board).

Particularly the conducting films comprise recesses, cut-outs or similar, allowing the connectors to protrude substantially perpendicularly with respect to the extension plane of the stripline layers, in order to form said input and/or output ports, from the laminate layer without contacting the conducting layer, i.e. the respective external conducting layer located opposite to the respective conducting layers facing each other at the interconnection. Particularly the respective protruding portions of the connectors forming input/output ports are taken up in a respective connector housing.

In specific embodiments a plurality of stripline layers are interconnected substantially perpendicularly to their planar extension via said connectors with modules or elements, e.g. forming a tile or brick like connection assembly. Thus, particularly the arrangement comprises a so called 2-way stripline assembly with perpendicularly to the plane of extension, e.g. vertically, disposed contacts or connectors, such that the connectors are disposed in different planes, or on both or opposite sides of e.g. stripline or PCB boards.

Most particularly the dimension of the overlapping zone in the plane of the interconnected stripline layers comprises approximately λ/4, wherein λ is the wavelength corresponding to the mid-frequency of handled RF waves or microwaves.

In one particular embodiment the connectors comprise so called GPO (Gilbert Push On) connectors, each comprising a connector pin and a connector housing. The connector pin is mounted in the laminate layer, or a PCB, whereas the connector housing is soldered or similarly onto a ground plane disposed on the external corresponding conducting layer disposed on the laminate layer of the respective stripline layer.

Particularly the overlapping conducting layers (or one of the conducting layers) comprises a distribution network, e.g. for power distribution to a plurality of radiating elements in an antenna system. Of course the distribution network can be used for any other application as well and the conductive pattern may particularly be provided in both or in one of the overlapping conducting layers. The other conducting layer (of the same stripline layer, i.e. disposed on the opposite side of the respective laminate layer) may also simply be used to establish a connection with a conducting layer of the interconnected stripline layer. Such a conducting layer may be formed by removal of up to 98-99% of all the conducting material of the conducting layer thus leaving only the required connections. Of course also other implementations are possible.

The stripline arrangement particularly comprises a stripline board with two laminate layers. It may also comprise a plurality of stripline layers with conducting layers disposed on either sides of respective laminate layers, wherein at least two adjacent stripline layers (other than those interconnected according to the inventive concept) are interconnected by means of vias, i.e. forming a multilayer structure.

The invention also discloses a method for producing a stripline arrangement comprising a number of stripline layers, each of which comprising a laminate layer disposed between conducting layers. The method comprises the steps of; etching conductive patterns in respective conducting layers disposed on either sides of a dielectric or ferroelectric laminate layer for at least two such stripline layers; arranging, e.g. soldering, connector means onto a respective first respective conducting layer disposed on each of the laminate layers, such that said connector means extend through said laminate layers substantially perpendicularly to the planar extension thereof such as to protrude through a respective second conducting layer disposed on the opposite side of said respective laminate layer; mounting said at least two stripline layers substantially parallelly onto each other such that an overlap is formed between the adjacent, each other facing, conducting layers of said stripline layers, whereby said overlap includes a number of connectors, and selecting the dimension of said overlap in a direction substantially parallel to the planar extension of said stripline layers in dependence of the wavelength of RF waves or microwaves to be handled by the stripline arrangement.

This can be done in one or more steps but generally no more than three steps comprising heating up in an oven as is known in the art. The hole stripline arrangement may also be formed in one single step. The respective conductive patterns are generally different and only in one conductive layer a so called distribution network is provided, or more particularly in both adjacent conducting layers in the overlap zone, the other layers solely having the function of providing interconnection and connection with externally mounted components. Particularly the method further comprises the step of; using said connectors as input/output ports, said input/output ports hence being located in different planes, on opposite sides of the stripline arrangement. The method further comprises the step of removing conducting material around the protruding portions or around the portions where connector parts protrude, which connector parts are to act as input/output ports; arranging housings to externally surround said as inputs/outputs intended connector parts.

The method further particularly comprises the step of; soldering said housings onto ground planes provided externally of said respective conducting layers with respect to the laminate layers to which they are connected.

The method preferably comprises the step of; bonding, by means of a bonding layer, two conducting layers of said at least two stripline layers to each other such that, in the conducting layer overlapping area, recesses or cut-outs are provided substantially around said, perpendicularly to the extension plane of the transmission line arrangement extending, connectors protruding from the stripline arrangement. The connectors particularly comprises connector pins. As referred to above, the dimension of the overlap particularly comprises a quarter wavelength of the wavelength of the relevant RF/microwave (millimeter wave) signal to be handled.

The method advantageously further comprises the step of; connecting a number of modules by means of said connectors, i.e. the protruding parts thereof, such that a perpendicular, particularly vertical contact connection assembly is formed. Such may for example be used to connect a plurality of antenna elements in antenna system implementations. Of course also other implementations are possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will in the following be further described, in a non-limiting manner, and with reference to the accompanying drawings, in which:

FIG. 1 is a very schematical cross-sectional view of a stripline arrangement according to the invention,

FIG. 2 is a more detailed view of one embodiment of a stripline arrangement according to the invention,

FIG. 3 shows an example of an application of a stripline arrangement according to the invention with vertical (perpendicular) contacts in different planes and to which a number of modules are connected,

FIG. 4 is a diagram illustrating simulated results for connectors in an optimization tool to a specific frequency band, and

FIG. 5 is a flow diagram describing one method for manufacturing a stripline arrangement according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 very schematically illustrates, in cross-section, a stripline arrangement 10 according to the present invention. The arrangement 10 comprises a first stripline layer 1₁comprising a laminate layer 1A with a conducting layer 2A and a second stripline layer 2₁comprising a laminate layer 1B with a conducting layer 2B. It is supposed that the stripline layers comprise laminate layers 1A, 1B which comprise a dielectrical or ferroelectrical material such as for example Rogers 3003. Of course the invention is not limited to use of this specific material but any appropriate material can be selected, and the material has to be selected such that the dielectric constant is appropriate for the desired implementation. The wavelength of an input RF signal or a microwave signal in the stripline arrangement λ_gdepends on the dielectric constant as λ_g=c/f×√{square root over (ε)}_r, and if a particularly thin board is desired, a material with a higher dielectric constant has to be selected and vice versa. The stripline layers 1₁, 2₁are so disposed that an overlapping zone or an overlap with length L is formed between the each other facing conducting layers 2A, 2B, and a bonding arrangement 5, for example a bonding film, is disposed for connecting the conducting layers 2A, 2B to one another. In particular the bonding film 5 is selected such as to match the dielectricum, i.e. the dielectric constant of the laminate layers 1A, 1B. The dimension L of the overlapping zone in a direction in the planar extension of the stripline arrangement 10, is selected depending on the wavelength of the RF/microwave signal relevant for the concerned application. The overlapping dimension L is particularly dependent on the frequency of the RF/microwave signal and, most advantageously, it should be substantially λ/4 of the RF/microwave signal in order to provide for a good electrical performance. It is particularly ¼ of the wavelength of the mid-frequency of the relevant RF/microwave signal in order to reduce losses or reflections and in order to assure that a particularly broad-banded arrangement is provided which additionally shows a very good controllability.

Particularly the thickness of the stripline arrangement 10 is of the magnitude 3 mm. However, the figure 3 mm is merely given as an example to illustrate that it is a comparatively thin arrangement; it may also be even thinner than that, e.g. 1.5 mm (or thicker) The given figures are merely to be seen as examples.

Depending on implementation or intended application the laminate material is selected to have a dielectric constant between for example 2 and 200 or lower or higher as well.

In the embodiment of FIG. 1 no input/output ports are illustrated and hence it should be clear that the input ports may be disposed perpendicularly as well as horisontally with respect to the planar extension of the stripline arrangement. A particularly advantageous embodiment relates to the case when the contacts or input/output ports are disposed substantially orthogonally with respect to the planar extension of the stripline arrangement and on opposite sides thereof as will be more thoroughly discussed with reference to for example FIG. 2. In addition to the connecting arrangement, connectors, particularly connector pins are provided in the overlapping zone (cf. FIG. 2) and the overlap is particularly indispensible in order to enable the use of, particularly in different planes, disposed input/output ports. It should also be clear that the bonding arrangement does not necessarily have to be a bonding film or a glue film, but also mechanically bonding or connection means could be used (not shown).

FIG. 2 shows an advantageous implementation of the invention comprising a stripline arrangement 10′ or a PCB with vertical connections in two planes, i.e. a 2-way stripline arrangement, (particularly applicable for all frequencies depending on selected dielectric constant) where the connections or input/output ports are disposed on both sides of the stripline arrangement 10′. Similar reference numerals are used for similar components as compared to FIG. 1. Thus, a first stripline layer comprises a laminate layer 1A with a first conducting layer 2A disposed on one side and a second conducting layer 3A disposed on the other side of said laminate layer 1A which is connected to a second stripline layer comprising a second laminate layer 1B with a first conducting layer 2B disposed on one side thereof and a second conducting layer 3B disposed on the other side of said laminate layer 1B. A bonding arrangement 5 comprising a bonding film is provided in the overlapping zone having an extension L′. A first perpendicular (vertical) connector 4A is further taken up in a through hole in the first laminate layer 1A and the respective conducting layers 2A, 3A connected to said first laminate layer 1A. Said connector 4A particularly comprises a connector pin with a “head”, and said “head” of said connector pin 4A is particularly soldered onto the first conducting layer 2A disposed on said first laminate layer 1A, hence protruding through the second conducting layer 3A.

Particularly recesses may be provided in portions of the bonding film surrounding the soldered connector heads to prevent their contacting the conducting layer 2B of the second laminate layer 1B and vice versa. In a similar manner a second connector 4B, particularly a connector pin, is soldered onto the first conducting layer 2B disposed on the second laminate layer 1B. Around the solder 6B a recess or similar may be provided as discussed with reference to the first connector 4A.

A portion of the second conducting layer 3A is removed, or there is no conducting material, in an area surrounding the external protrusion of the first connector 4A to prevent conducting connection between the connector 4A and the second conducting layer 3A to provide an output port (of course it may also be an input port, but in this implementation it is supposed that it acts as an input port) and a housing or connector house 7A is soldered, indicated through solder 8A, onto a ground plane 11A provided on the conducting layer 3A. Similarly a recess or similar is provided in the second conducting layer 3B disposed on the second laminate layer 2B where the connector 4B protrudes externally and a housing 7B is soldered (solder 8B) onto a ground plane 11B provided on the second conducting layer 3B disposed on the second laminate layer 1B. The connector, or particularly the connector pin, 4B in this case acts as an input port, although, it of course also may be operative as an output port depending on implementation.

In FIG. 3 below it is schematically illustrated an implementation of a stripline arrangement as in FIG. 2 comprising two output/input ports and 12 input/output ports provided through connector pins 4A, i. e. on top of FIG. 2. Onto the ports 4_in1, . . . , 4_in12modules 21₁, . . . , 21₁₂can easily be mounted, e.g. snapped on directly or indirectly via intermediate means. In FIG. 2 it is also illustrated a chip-resistor 9 connected to the first conducting layer 2A in a conventional manner, which however is not specific for the present invention and therefor will not be more thoroughly described herein. Particularly the conducting layer 2A disposed on the first laminate layer 1A comprises a distribution network, together with layer 2B in the overlapping zone, etched in the conducting material in such as to leave only the conductive pattern. The conductive patterns in the other conducting layers are particularly provided in order to provide connection between the layers and input/output sides.

As referred to with reference to FIG. 2, the overlap L′ particularly comprises λ/4. The connectors 4A, 4B, particularly connector pins, may for example comprise so called GPO (Gilbert Push On) connectors which are perpendicularly (vertically) disposed with respect to the stripline arrangement, or the PCB. Such a connector solution particularly consists, as can be seen from FIG. 2, of a connector house 7A, 7B and a connector pin 4A, 4B. The connector pins 4A, 4B are amounted onto the PCB or stripline arrangement, whereas the connector houses 7A, 7B are soldered onto the respective ground planes as discussed above. Due to the connector pins 4A, 4B, reflections are produced; therefore the connectors have to be optimized for respective application specific frequency bands. This may for example be done in simulation tools, one example thereof being HP HFSS (Ansoft ver. 8.5™) and in FIG. 4 some simulation results for connectors are illustrated as the suppression in dB versus frequency (in GHz).

It should be clear that this merely constitutes one particular example; optimization may of course also be provided for in a number of other ways.

The inventive concept may be used in many different applications, one thereof being in antenna systems in which the modules (see FIG. 4) 21₁, 21₂, . . . , 21₁₂are mounted at contacts of the (here) 12 input/output ports. Said modules may then be connected to respective antenna elements or radiating elements which is very advantageous.

Since the output ports or the input ports are oppositely directed in relation to for example antenna ports (not shown) the stripline transmission needs to change from one stripline layer to another and in a particular embodiment all hybrides and transmission lines are provided on one of the stripline layers, i.e. the conducting layer disposed thereon, but at a given distance before for example an input port, the transmission line needs to change to the other e.g. lower stripline layer and this is taken care of through the overlapping zone as discussed above.

FIG. 5 schematically illustrates one example of a manufacturing method for producing a stripline arrangement according to the present invention. According to the embodiment described with reference to flow diagram of FIG. 5, a stripline arrangement with a number of modules connected thereto may be produced as follows: In a first step, conducting layers are provided on each side of at least two respective laminate layers with a selected dielectric constant to form at least two, here called, stripline layers, 101. Subsequently respective conductive patterns are etched in the respective conducting layers, of which at least one (on one of the stripline layers or adjacent conducting layers in the overlap zone) for example is a distribution network, 102. It should be clear that the conductive patterns may take many forms depending on implementation. Subsequently connectors are mounted in through holes provided in each of said stripline layers, 103. The invention is not limited to any specific way of providing such through holes, or using any specific mounting technique or similar. Subsequently enlarged or broadened protruding portions of said connectors, e.g. connector heads or similar, are soldered onto one of the respective conducting layers of the respective stripline layers, 104, such that the connector or connector pins are soldered onto one of the conducting layers disposed on a laminate layer and protrudes through the other conducting layer on the opposite side of said same stripline layer, 104. At this stage, or at an earlier stage, recesses or similar are provided in the conducting layers located on those sides of the laminate layers which are opposite to the solders around the connectors, which recesses or similar substantially surround through holes to prevent contact between the respective connectors and the conducting layers on those sides which are opposite to the solders, 105. Then a bonding layer is provided on the conducting layers on the sides of the stripline layers where the connectors are soldered, 106. The at least two stripline layers are then interconnected through interconnection of the conducting layers onto which a connector is soldered, respectively, by means of a bonding layer or similar, such that an overlap is formed between the adjacent respective conducting layers of the respective stripline layers, 107. The size of the overlap etc. has been discussed earlier in the application and will therefore not be further described here. Finally, connector houses are soldered onto ground planes disposed on the layers forming external conducting layers surrounding protruding connector pins, hence providing forming input/output ports through said protruding connectors with housings mounted thereon, 108. Finally, modules may simply be mounted onto said connectors or connector housings, which modules in turn may be mounted onto for example antenna elements or similar.

It should be clear that these steps can be performed in different orders, the boards may be joined in different steps etc. However, generally the stripline layers etc. do no withstand being heated up more than three times, hence the assembling procedure should preferably be performed in one, two or three steps.

It should also be clear that the invention of course not is limited to the specifically illustrated embodiments but that it can be varied in a number of ways within the scope of the appended claims and that it can be used for several different applications, not only for antenna systems but also in other applications, particularly if a distribution network is needed for distributing signals to microwave products (millimeter wave products), or such products, and where it is appropriate to have vertical, or more generally perpendicular, in relation to the stripline arrangement, provided contacts, which offers a very cheap and easy way to manufacture assemblies which for example may be built up in the form of tile or brick-like structures and where compact solutions are needed.

Stripline Arrangement and a Method for Production Thereof

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