Abstract:
An impedance converter device comprises an electrically conductive external conductor with one or more connection locations for electrical lines, an electrically conductive internal conductor with one or more connection locations for electrical lines, and also a dielectric arranged between external conductor and internal conductor. The external conductor comprises a base area bounded by one or more side walls thereby forming an external conductor housing with an internal space and an opening opposite the base area. The internal conductor is arranged in the internal space. The internal conductor and the external conductor are insulated from one another by the dielectric. The internal conductor comprises at least one cutoff bar-type section with a cutoff bar bottom and at least one wall which extends from the bottom in the direction of the opening of the external conductor housing.

Description:
FIELD 
   The technology herein relates to an impedance converter device. 
   BACKGROUND AND SUMMARY 
   Impedance converters are used nowadays in particular in antenna arrangements for transformation of impedances. The impedance converters serve for matching the impedances resulting from individual radiator elements or antenna components, such as e.g. phase shifters, filters, bandpass filters, in broadband fashion to a common system impedance, which is 50 ohms in the field of mobile radio. 
   The prior art discloses impedance converters in which an impedance conversion is carried out by means of a λ/4 transformation by virtue of coaxial cables having a length corresponding to a quarter of the wavelength of the radio frequency with which the antenna arrangement is operated being interposed between connections in the antenna arrangement. In this case, it proves to be disadvantageous that, for the interposition of coaxial cables, a multiplicity of soldering points have to be provided at the ends of the coaxial cables, so that the production of such impedance converters is expensive and also greatly affected by tolerances owing to the diversity of parts. Equally, the prior art discloses tuning screws for altering the impedance in coaxial elements. This type of impedance conversion is also comparatively expensive. Moreover, impedance transformations are carried out by means of impedance converters in the form of strip conductors on circuit boards. What is disadvantageous in this case is that these impedance converters are permissible only for limited radio-frequency powers and a subsequent tuning of the impedance is not possible; in addition, intermodulation problems have to be reckoned with. 
   Therefore, it is an object of the exemplary illustrative non-limiting technology herein to provide an impedance converter device which can be produced cost-effectively, is suitable for high radio-frequency power and enables a tuning of the impedance in a simple manner. 
   The impedance converter device according to an exemplary illustrative non-limiting implementation herein is distinguished by a special shaping of an external conductor, of an internal conductor and also of a dielectric located in between. The external conductor of the device comprises a base area bounded by one or more side walls, thereby forming an external conductor housing with an internal space and an opening opposite the base area. The internal conductor is arranged in the internal space, the internal conductor and the external conductor being insulated from one another by the dielectric. The internal conductor comprises at least one cutoff bar-type section with a bottom and at least one wall which extends from the bottom in the direction of the opening of the external conductor housing. The configuration of the external conductor as an open housing enables access to the internal conductor, in particular to the walls of the cutoff bar-type sections. The angle of said walls can be adjusted by a corresponding tool, thereby enabling an operator to tune the impedance in a simple manner without intermodulation problems occurring or the intermodulation properties being impaired. It should be noted in this case that the opening can be closed by a suitable closure device. On the side opposite the base area of the exemplary illustrative non-limiting implementation, the housing is not formed in one piece with all the side walls of the housing, so that an (if appropriate also closed) opening can always be localized in the impedance converter. A further advantage of the exemplary illustrative non-limiting impedance converter is that the external conductor housing can be used universally and only the readily accessible internal conductor has to be exchanged in order to alter the transformation properties of the impedance converter. On account of the structural height attained by the external conductor housing, undesirable emissions of the converter do not occur. Moreover, the converter can be used for very high radio-frequency powers. 
   Preferably, the impedance converter essentially extends in a longitudinal direction between at least two opposite connection locations. Furthermore, at least web bottom of a cutoff bar-type internal conductor section is assigned at least two walls which extend in the direction of the opening of the external conductor housing in particular from edges of the bottom. In particular, the walls assigned to a bottom are parallel to one another. In one exemplary illustrative non-limiting implementation, the walls assigned to a bottom converge or diverge in the longitudinal direction of the impedance converter in a sectional view along a plane parallel to the base area of the external conductor. As an alternative, the walls assigned to a bottom are parallel to one another. Furthermore, the walls assigned to a bottom may be essentially perpendicular to the bottom. As an alternative, the walls assigned to a bottom diverge or converge in the direction of the opening of the external conductor housing in a sectional view along a plane perpendicular to the longitudinal direction of the impedance converter. 
   In an exemplary illustrative non-limiting implementation, the external conductor comprises a stamped, one-piece metal sheet with bent-over side walls. This enables the external conductor to be produced extremely inexpensively since the production by stamping is simple and cost-effective. Analogously, the internal conductor is preferably likewise a stamped, one-piece metal sheet with bent-over walls. This results, on the one hand, in cost-effective production of the internal conductor and, on the other hand, ensures good bendability of the walls, so that the impedance can easily be tuned or altered by bending the walls. 
   In an exemplary illustrative non-limiting implementation, the dielectric is a component with a receptacle, the component being inserted in the internal space of the external conductor housing and the internal conductor being arranged in the receptacle of the component. This results, in a simple manner, in an electrical insulation between internal conductor and external conductor by means of a separate component. In this case, the component is preferably formed in one piece. Furthermore, in a preferred variant, the component is held by force locking, in particular by a clamping, and/or by positive locking and/or by material locking in the external conductor housing. Analogously, the internal conductor may be held by force locking, in particular by a clamping, and/or by positive locking and/or by material locking in the receptacle of the dielectric. This enables simple assembly of the components of the impedance converter according to the exemplary implementation without the need to provide additional fixing means. 
   In a further preferred variant of the converter, the internal conductor has, at its ends, end sections with at least one or more end areas which extend in the direction of the opening of the external conductor housing. These end sections can be used to fix the position of the internal conductor in the external conductor housing. When this variant is combined with the exemplary implementation in which the dielectric is a component with a receptacle, one or more corners of the receptacle are preferably rounded and receive edges of the end sections of the internal conductor. 
   In an exemplary illustrative non-limiting implementation, the internal conductor has at least one first cutoff bar-type section for impedance transformation. In this case, the first cutoff bar-type section preferably has a length which is ¼ of the wavelength of a radio frequency which is used for mobile radio transmission, in particular a radio frequency in a GSM network and/or UMTS network. In this case, the length is preferably coordinated with the center frequency to be transmitted. This enables the impedance converter according to the exemplary implementation to be used as a λ/4 transformer in customary mobile radio networks. The impedance converter also makes it possible, if appropriate, to carry out multistage λ/4 transformations when using long external conductors. 
   In a further illustrative exemplary non-limiting implementation, the internal conductor has at least one second cutoff bar-type section for length adaptation of the internal conductor. The second cutoff bar-type section has the effect that the length of the internal conductor is always identical, independently of the radio-frequencies used, so that the internal conductor can always be inserted into an identically constructed external conductor housing. Consequently, the impedance converter can be adapted to different antenna systems in a simple manner by exchanging the internal conductor. 
   In order to connect the impedance converter to electrical lines, connection locations are provided in external conductor and in the internal conductor, said connection locations preferably comprising openings at ends of the external conductor and of the internal conductor, respectively. Each opening of the external conductor is preferably aligned with an opening of the internal conductor, the aligned openings in each case being connected to one another through an opening in the dielectric. The openings of the external conductor and of the internal conductor are preferably designed for receiving and subsequently soldering coaxial cables, the openings of the external conductor serving to receive a coaxial external conductor and the openings of the internal conductor serving to receive a coaxial internal conductor. The openings of the dielectric are preferably in each case accommodated in cutouts which serve in particular to receive an insulation arranged between a coaxial external conductor and a coaxial internal conductor. Furthermore, the openings of the external conductor may comprise at least one shoulder which serves in particular as a stop for an end of a coaxial external conductor. 
   In an exemplary illustrative impedance converter implementation, coaxial cables are soldered by means of soldering paste and/or integrated soldering moldings at the openings of the external conductor and of the internal conductor. This enables the coaxial cables to be soldered to the impedance converter in an automated and cost-effective manner. 
   In a refinement, the exemplary illustrative dielectric used in the impedance converter may comprise air, which means that the internal and external conductors of the impedance converter are spaced apart from one another by additional spacing means. 
   In a further refinement of the exemplary impedance converterimplementation, the internal conductor is configured in compartment-like fashion with a plurality of cutoff bar-type sections arranged parallel. This enables the device to be interconnected with a plurality of different systems. In order to fix the cutoff bar-type sections, the latter are in each case arranged in a cutout in the dielectric. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages will be better and more completely understood by referring to the following detailed description of exemplary non-limiting illustrative implementations in conjunction with the drawings of which: 
       FIG. 1  shows a perspective view of an exemplary illustrative non-limiting impedance converter; 
       FIG. 1   a  shows a perspective view of an exemplary illustrative non-limiting external conductor used in the impedance converter; 
       FIG. 2  shows a perspective view of the exemplary impedance converter of  FIG. 1  rotated through 180° with respect to  FIG. 1 ; 
       FIG. 3  shows a plan view of the exemplary impedance converter of  FIG. 1 ; 
       FIG. 4  shows a sectional view of the exemplary impedance converter of  FIG. 3  along the line I—I; 
       FIG. 5  shows a perspective view of a further exemplary illustrative non-limiting impedance converter; 
       FIG. 6  shows a perspective view of the exemplary impedance converter of  FIG. 5  rotated through 180° with respect to  FIG. 5 ; 
       FIG. 7  shows a plan view of the exemplary impedance converter of  FIG. 6 ; and 
       FIG. 8  shows a sectional view of the exemplary impedance converter of  FIG. 7  along the line II—II. 
   

   DETAILED DESCRIPTION 
     FIG. 1  and  FIG. 2  show perspective views of an exemplary illustrative non-limiting implementation of an impedance converter. The exemplary converter comprises an external conductor in the form of an external elongate metal housing  1 , the housing being open at the top side and comprising a stamped metal sheet. The housing is of essentially rectangular configuration and has a base area  1   a  (not visible in  FIG. 1  and  FIG. 2 ) and also side walls  1   b ,  1   c ,  1   d  and  1   e . As is shown in  FIG. 1   a , the external conductor  1  is preferably a metal sheet part whose side walls are upwardly bent sections of the metal sheet part. In this case, the edges of the individual side walls are spaced apart from one another by narrow interspaces Z. In the interior of the external conductor shown in  FIG. 1   a , the dielectric  3  may be fixedly clamped by force locking by means of the bent side walls. 
   The dielectric is likewise open at the top side and an internal conductor  2  is inserted in its interior. Said internal conductor has end sections  2   c  and  2   d  respectively comprising side walls  24 ,  25 ,  26  and  27 ,  28 ,  29 . The end sections are pushed into the dielectric  3  by means of rounded corners  3   a ,  3   b ,  3   c  and  3   d . The internal conductor  2  has a length such that it is fixedly clamped in the internal space of the dielectric  3  by means of the end sections  2   c  and  2   d . The internal conductor comprises two cutoff bar (“web”)-type sections  2   a  and  2   b  connected to one another between the end sections  2   c  and  2   d . The first cutoff bar-type section  2   a  comprises a bottom  21  and two walls  22  and  23  extending perpendicularly upward. Analogously, the second cutoff bar-type section  2   b  comprises a bottom  21 ′ (not visible in  FIGS. 1 and 2 ) and walls  22 ′ and  23 ′. The internal conductor is preferably formed as a one-piece metal sheet, in which case, in the metal sheet, first of all the shaping of the side walls of the end section and of the cutoff bar-type sections is stamped out and then the side walls and walls are bent upward. The use of stamped sheets for the external conductor and the internal conductor ensures inexpensive and simple production of the impedance converter. 
   The transformation impedance can be set by means of the width of the cutoff bar-type sections  2   a ,  2   b  and the corresponding bent-up walls or by means of the height of the cutoff bar-type sections above the external conductor bottom (spacing through dielectric). 
   The first cutoff bar-type section  2   a  serves for impedance transformation if the impedance converter is soldered in an antenna arrangement between coaxial cables. The length of the first cutoff bar-type section  2   a  is ¼ of a wave length λ, as a result of which a λ/4 transformation is carried out, where λ corresponds to the wavelength of the radio frequency with which the corresponding antenna arrangement is operated. The customary mobile radio frequencies, such as e.g. 900 or 1800 MHz in GSM networks, are preferably involved in this case. In contrast to the first cutoff bar-type section  2   a , the second cutoff bar-type section  2   b  of the impedance converter primarily serves for length correction. In other words, the length of the second cutoff bar-type section is always chosen in a manner dependent on the length of the first cutoff bar-type section and the total length of the impedance converter such that the internal conductor is always fixed in the same position in the dielectric. 
   The internal conductor  2  has the major advantage that its impedance can be adapted or altered by bending the walls of the first cutoff bar-type section  2   a . This is advantageous in particular during the manufacture of the impedance converter, since, at the end of the manufacturing process, possible tolerances in the impedance can again be compensated for by bending the walls  22  and  23 , respectively. If appropriate, the second cutoff bar-type section may also be configured in such a way that it likewise influences the impedance, so that the impedance of the converter can also be altered by bending the walls  22 ′ and  23 ′, respectively. 
   The external conductor  1  of the impedance converter has a cylindrical opening  101  in the side area  1   e  and also two cylindrical openings  102  and  103  connected to one another in the side area  1   c . These openings are connected to smaller cylindrical openings  201 ,  202  and  203  in the end sections  2   c  and  2   d , respectively, via corresponding cylindrical openings  301 ,  302  and  303  in the dielectric  3 . The openings in the external conductor and in the internal conductor serve for connection to a coaxial cable, the openings of the external conductor serving to receive a coaxial external conductor and the corresponding openings in the internal conductor serving to receive the corresponding coaxial internal conductor. In order to fix the coaxial conductors of the cable, the conductors are soldered to the openings. In particular, solderings for the coaxial external conductors are provided at the outer sides of the side walls  1   c  and  1   e  of the housing  1  and solderings for the coaxial internal conductor are provided in the end sections  2   c  and  2   d  of the internal conductor  2 . By means of integrated soldering moldings or soldering pastes, the internal and external conductor soldering between the impedance converter and the coaxial cables can be effected in an automated manner (e.g. induction soldering). In comparison with conventional impedance converters in which coaxial cables for impedance conversion are soldered in as an intermediate connection, a smaller number of soldering locations are required in the exemplary illustrative non-limiting impedance converter. Furthermore, the structural height of the impedance converter prevents emissions which occur, for example in the case of impedance converters in the form of strip conductors on circuit boards. 
     FIG. 3  shows a plan view of the impedance converter from  FIG. 1  and  FIG. 2 .  FIG. 3  reveals in particular that the bottom  21  of the first cutoff bar-type section  2   a  is wider than the bottom  21 ′ of the second cutoff bar-type section  2   b . Furthermore, the length of the second cutoff bar-type section is less than the length of the first cutoff bar-type section. What is achieved by virtue of the size-reduced design of the second cutoff bar-type section is that this section has only a small influence or no influence at all on the impedance of the converter.  FIG. 3  furthermore reveals that the walls  22  and  23  and also  22 ′ and  23 ′ of the cutoff bar-type sections are readily accessible from above, so that an operator can readjust or tune the impedance, if appropriate, by bending the walls. 
     FIG. 4  shows a sectional view along the line I—I of  FIG. 3 , broken lines indicating the position of coaxial cables which are connected to the impedance converter. Furthermore, the cross section of the external conductor housing  1  is indicated by a single hatching, whereas the cross section of the dielectric  3  is represented by a double hatching.  FIG. 4  reveals, in particular, the diameters of the openings  101  and  103  in the external conductor housing, of the openings  301  and  303  in the dielectric and also of the openings  201  and  203  in the internal conductor housing. Of the openings  103 ,  203  and  303 , the opening  103  has the largest diameter, and serves to receive a coaxial external conductor  51  of a coaxial cable  5 . In this case, the inserted coaxial external conductor stops at a peripheral shoulder S in the opening  103 . The opening  303  has a smaller diameter than the opening  103  and serves to receive an insulation  53  of the coaxial cable  5 . The opening  203  has the smallest diameter and serves to receive the coaxial internal conductor  52  of the coaxial cable  5 . The coaxial external conductor  51  is fixed by means of a soldering to the outer side of the side wall  1   c . Analogously, the coaxial internal conductor  52  is soldered to the inner side of the side wall  25 . 
   The openings  101 ,  201  and  301  in the region of the side wall  1   e  are designed for a larger or lower-attenuation coaxial cable  5 ′. Analogously to the opening  103 , the opening  101  has a corresponding shoulder S′ against which one end of a coaxial external conductor  51 ′ stops. The opening  301  is smaller than the opening  101  and it is arranged in a cylindrical cutout A in the dielectric  3 , the cutout being chosen in such a way that the insulation  53 ′ of the coaxial cable  5 ′ can be accommodated therein. The size of the opening  201  in the internal conductor  2  essentially corresponds to the size of the opening  301  in the dielectric  3 , the diameter of the openings being chosen in such a way that the coaxial internal conductor  52 ′ of the coaxial cable  5 ′ fits through the openings. Analogously to the opposite side of the impedance converter, the coaxial internal conductor  52 ′ is soldered to the inner side of the side wall  28  and the coaxial external conductor  51 ′ is soldered to the outer side of the side wall  1   e . If, by way of example, two coaxial cables each having an impedance of 50 ohms are inserted via the openings  102  and  103 , an input impedance of 25 ohms is produced at this location. The impedance of the impedance converter is to be set to 35 ohms in such a case, in order that an impedance of 50 ohms is produced again at the opposite opening  101 . Instead of two connection locations for coaxial cables at the side wall  1   e , it would also be possible, if appropriate, to provide only a single connection location for an individual coaxial cable. 
     FIGS. 5 and 6  show two perspective views of a second exemplary illustrative non-limiting implementation of an impedance converter, the view of  FIG. 6  being rotated through 180° with respect to the view of  FIG. 5 . In contrast to the first exemplary implementation, the internal conductor  2  of the impedance converter is configured in compartment-type fashion, three cutoff-bar-type sections  2   a ,  2   a ′ and  2   a ″ arranged parallel to one another being provided instead of an individual first cutoff bar-type section. However, it is also possible to provide only two or else more of such cutoff bar-type sections arranged parallel. The cutoff bar-type sections are connected to the second cutoff bar-type section  2   b  via a transversely running web  2   e . In order to contact-connect the three first cutoff bar-type sections to corresponding coaxial cables, respectively interconnected openings  102 ,  103  and  102 ′,  103 ′ and  102 ″,  103 ″ are provided in the external conductor  1 . Furthermore, each cutoff bar-type section  2   a ,  2   a ′ and  2   a ″ opens into separate end sections  2   c ,  2   c ′ and  2   c ″, respectively, as emerges in particular from  FIG. 6 . An end section  2   d  likewise adjoins one side of the cutoff bar-type section  2   b . Analogously to the preceding illustrative implementation, all the openings in the external conductor  1  are aligned with corresponding openings in the dielectric and in the internal conductor. In order to fix the internal conductor in the dielectric, corresponding receptacles for the end sections  2   c ,  2   c ′,  2   c ″ and  2   d  are provided in the internal space of the dielectric. Said receptacles are formed by parallelepipedal projections  31 ,  32 ,  33  and  34  at the inner sides of the dielectric. The internal conductor is thereby fixed on the dielectric. 
     FIG. 7  shows a plan view of the impedance converter of  FIG. 5  and  FIG. 6 .  FIG. 7  reveals, in particular, the structure of the internal conductor. It can be seen that the three parallel cutoff bar-type sections  2   a ,  2   a ′,  2   a ″ are configured identically and have a larger width than the cutoff bar-type section  2   b . However, the cutoff bar-type sections may also have different widths in order to achieve a desired power division. By bending the walls of the cutoff bar-type sections  2   a ,  2   a ′ and  2   a ″, it is again possible to tune or alter the impedance since the cutoff bar-type sections  2   a ,  2   a ′ and  2   a ″ essentially perform the function of impedance transformation. The narrower cutoff bar-type section  2   b  serves for length adaptation or, if appropriate, also for impedance transformation of the three individual branches of the internal conductor  2 , the length of the section always being chosen such that the internal conductor is fixedly clamped in the internal space of the dielectric  3  between opposite side walls of the dielectric. On account of its fanned-out form, the impedance converter serves for connecting a plurality of parallel coaxial cables, thereby enabling an interconnection and impedance transformation of a plurality of antenna systems. 
     FIG. 8  shows a sectional view along the line II—II of  FIG. 7 . This reveals, in particular, the dimensions of the cylindrical openings in the impedance converter, corresponding coaxial cables  5  and  5 ′ being inserted in the openings for illustration purposes. The construction of the converter in accordance with  FIG. 8  is essentially identical to the construction of the converter of  FIG. 4 , identical structural parts being designated by the same reference symbols. Therefore, a detailed description of the construction of  FIG. 8  is dispensed with and reference is made in this respect to  FIG. 4 . The arrangement of the openings  103 ,  203  and  303  in the region of the end section  2   c  is illustrated on the left-hand side of the impedance converter of  FIG. 8 , the arrangement of the openings in the corresponding end sections  2   c ′ and  2   c ″ being identical. Analogously to  FIG. 4 , the opening  103  has a shoulder S for receiving the coaxial external conductor  51 . Likewise, a shoulder S′ is provided on the opposite, right-hand side of the converter in the opening  101  and the opening  301  is arranged in a cutout A which serves to receive the insulation  53 ′. As is described with reference to  FIG. 4 , the external and internal conductors of the coaxial cables are soldered to the external and internal conductors of the impedance converter. 
   While the technology herein has been described in connection with exemplary illustrative non-limiting implementations, the invention is not to be limited by the disclosure. The invention is intended to be defined by the claims and to cover all corresponding and equivalent arrangements whether or not specifically disclosed herein.