Patent Publication Number: US-8120444-B2

Title: Circuit for separating or combining high frequency power

Description:
This application is the U.S. national phase of International Application No. PCT/EP2007/009464 filed 31 Oct. 2007, which designated the U.S. and claims priority to Germany Application No. 10 2006 056 618.1 filed 30 Nov. 2006, the entire contents of each of which are hereby incorporated by reference. 
     The invention relates to a circuit for separating or combining high frequency power in accordance with the preamble of claim  1 . 
     A generic circuit for separating and combining high frequency power is known, for example, from the brochure “Kathrein-Werke KG—Base Station Antennas for Mobile Communication, catalogue 03.99”. 
     The circuit is housed, for example in an elongate housing, at an end face of which what is known as a summation port is provided as an input and at the opposite end of which a first single port, for example, is provided as an output. Between one and three further connections are provided adjacent to said output at the end of the longitudinal sides of the housing, which connections act as outputs for the outcoupled power portions when HF power is supplied at the summation port (which acts as an input). In other words, the supplied signals are split between two, three or, for example, four outputs depending on the number of outputs provided. 
     The connection interfaces are normally 7/16 coaxial connections with threaded couplings, for example in accordance with IEC standard 169-4, or what are known as N connectors in accordance with IEC standard 169-16. 
     Dividers of this type for high frequency signals are normally used within the field of mobile radio or radio technology, that is to say in corresponding mobile radio or radio systems. Dividers of this type are also sometimes referred to as power splitters. In particular, if the power is separated differently at the outputs, reference is made to what are known as power tappers. 
     With reference to  FIGS. 1 and 2 , a known divider of this type in accordance with the prior art, i.e. a circuit for splitting or combining high frequency power, is shown in greater detail and will be described hereinafter. 
       FIG. 1  shows the outer conductor  1  of the divider, which may have a rectangular or square cross-section for example. In a variant, the cross-section of the housing  1 ′ forming the outer conductor  1  may also be configured so as to be of a different shape, for example annular. 
     This outer conductor  1  consists of a machined profiled part which is mostly made of aluminum. An extruded profiled part is preferably used in this case. 
     A first single port  4  for example is provided at the lower end  1   a  of the outer conductor  1 , which single port may also be referred to hereinafter as a summation port. 
     At the opposite end-face end  1   b , which is also referred to hereinafter as the upper end, a second single port  5   a  for example may be provided which acts as an output when HF power to be separated is supplied at the first single port  4 . 
     A third, a fourth or for example even a fifth single port  5   b ,  5   c  and  5   d  (or even more) may, for example, be provided adjacent to said end-face upper end  1   b  on the side faces  1   c  of the housing-shaped outer conductor  1 , via which ports the HF power supplied by the summation port  4  can be supplied to the circuits which can be connected to said single ports  5   b  to  5   d  (or, vice-versa, by supplying HF energy via the single ports  5   a  to  5   d  the combined energy may be supplied to the summation port  4 ). 
     As can be seen, in particular from the cross-sectional view shown in accordance with  FIG. 2  of a divider of this type known from the prior art, the outer conductor  1  is hollow on the inside and comprises a longitudinal hole  9  in which an inner conductor  11 , which is separate from the outer conductor  1 , is arranged, which inner conductor is supported and held in place relative to the outer conductor  1 , at least indirectly, via insulating holders  13  (insulator rings). 
     The single ports  5   a  to  5   d  normally consist of coaxial plug-in connectors  15  which, for example, are each fixed via four single screws  17  which can be screwed into corresponding threaded holes  19  in the housing of the outer conductor  1 . The coaxial plug-in connectors  15  thus comprise threaded couplings, via which the entire ready-made socket, for example matched to 50Ω, is fixed to the housing  1  using the aforementioned screws. 
     The coaxial plug-in connectors  15  are configured as a plurality of parts, as can be seen in particular from the cross-sectional view according to  FIG. 2 . They each comprise an inner conductor  21  and inner conductor sockets  22  arranged axially thereon, a disc-shaped insulating support  13  supported on each of the inner conductor sockets and an outer conductor socket  24 , which is supported outwardly between the insulating support  23  and the tubular outer conductor connection support  25  which, in turn, is provided with an outer thread in such a way that it is possible, in this case, to screw on a coaxial cable with a corresponding connection socket provided with an inner thread for example, thus ensuring contact with an inner and outer conductor. 
     As can be seen in particular from  FIG. 2 , inner conductor extension pins  26  are provided in the axial extension of the inner conductor  21 , which pins are supported on and screwed into the transformation inner conductor  11  extending through the outer conductor  1  in the axial longitudinal direction. 
     The aforementioned inner conductors  21  and the inner conductor extension pins  26  contactlessly penetrate a radial hole  28  in the housing  1 ′ acting as an outer conductor  1 . 
     The single port  5   a  arranged on the upper end-face end  1   b  comprises a corresponding inner conductor  21  which is also screwed into a portion of the transformation inner conductor  11  from its position above and is electrically contacted therewith. 
     A conventional divider of this type, whether used as a divider, splitter or tapper, presents drawbacks regarding intermodulation caused by a relatively high number of contact points, some of which have a large surface area. In addition, contact corrosion may also take place at the connection points between the separate line portions which are in contact, even if the sockets are assembled so as to be tight relative to the outer face of the housing  1  by way of annular seals  27 . It is extremely important for the parts to fit together accurately. In addition, assembly is also extremely complex owing to the relatively high number of contact points. 
     A conventional circuit for separating or combining frequencies is also known from U.S. Pat. No. 3,428,920. In this case a divider with a head piece is known. The head piece is spherical and comprises cylindrical connection pieces arranged so as to be offset in the peripheral direction, which connection pieces are inserted into corresponding holes in the housing-shaped head piece. The housing-shaped head piece is not only mechanically connected to the outer conductors, but these together form the outer conductor. The inner conductor is held in these cylindrical outer conductors in an insulated manner. In this case, similarly to the prior art according to  FIGS. 1 to 2  and mentioned at the outset, the single ports are coaxial plug-in connectors. 
     Lastly, a power combiner or power divider is also known from U.S. Pat. No. 5,880,648. The divider comprises a head piece with a plurality of individual components which are connected to a common assembled head piece which can be easily handled. 
     The object of the present invention is therefore to develop a circuit for separating or combining power frequencies, which reduces or minimizes the aforementioned drawbacks. 
     The object is achieved according to the invention in accordance with the features disclosed in claim  1 . Advantageous embodiments of the invention are given in the sub-claims. 
     Within the scope of the solution according to the invention, a circuit for separating or combining HF power is provided which offers considerable advantages over the prior art. 
     The invention is characterized by a compact construction which can be adjusted over an extremely wide range, for example from 350 to 3800 MHz. 
     Since a one-piece head piece with corresponding connections is used within the scope of the invention, problems regarding intermodulation are avoided. Owing to the fact that a separate mechanical connection point between the connection sockets and the divider head is avoided, contact corrosion at these points is also prevented. Since the connection head is not only preferably integrally configured but is also made of a consistent material, any possible problems regarding intermodulation and contact erosion are avoided. 
     In accordance with the invention, the one-piece connection head consists of a forged part, a cast part or a milled part. Any suitable materials may be considered, for example brass. The outer conductor may also consist of a corresponding metal tube, for example in the form of a machined profiled part, a turned part or an extruded part. In this case also, any suitable materials may be considered. 
     It has proven to be particularly advantageous within the scope of the invention if identical component parts can always be used for the connections (irrespective of whether the device is used as a two-way, three-way, four-way or general multi-way divider), since the inner conductors are of the same length or may be of the same length for all connection outputs. In a preferred embodiment of the invention, this is achieved by “sinking” the relevant inner conductor connection piece in the transformation inner conductor, the electrical properties being unaffected. 
     In a particularly preferred embodiment, what is known as a “blind hole” is formed in the connection head (opposite a lateral output). The blind hole enables symmetrical loading at the outputs, as a result of which it is possible to achieve a high level of phase balance and optimum power distribution between the outputs. 
     The invention also makes it possible to use a combination of different connection sockets, i.e. connection interfaces, for example what are known as 7-16 coaxial connectors or, for example, the aforementioned N connectors or threaded couplings in accordance with IEC standard 169-4, at the single ports acting as outputs for example. 
     A further advantage is that despite using the one-piece housing piece, the entire device can be produced in a cost-effective manner. 
     The housing-shaped, generally longitudinally extending outer conductor is preferably connected mechanically and electrically at an interface to the connection head or divider head by means of a screw connection, compression joint, soldered joint or another connection allowing intermodulation. However, said housing-shaped outer conductor  1  may also be configured integrally with the head piece. 
    
    
     
       The construction according to the invention of the device or circuit for separating or combining HF power will be explained hereinafter with reference to further drawings, in which: 
         FIG. 1  is a schematic, three-dimensional, partly exploded view of a corresponding divider according to the prior art; 
         FIG. 2  is an axial longitudinal sectional view through the divider in accordance with  FIG. 1  according to the prior art; 
         FIG. 3  is an exploded view of an embodiment according to the invention of a circuit for separating or combining HF power; 
         FIG. 4  is a corresponding sectional view through the embodiment according to the invention in accordance with  FIG. 3 ; 
         FIG. 5  is an axial sectional view through the circuit or divider head; 
         FIG. 6  is a three-dimensional view of the upper insulator consisting of two insulator halves in the region of or adjacent to the head piece of the circuit or divider head; and 
         FIG. 7  is a three-dimensional view of the head piece viewed from the lower side, to which the inner and outer conductors are connected. 
     
    
    
     The invention will be described hereinafter with reference to  FIG. 3  onwards. 
       FIG. 3  is an exploded three-dimensional view of a divider according to the invention and  FIG. 4  is a longitudinal sectional view of a divider according to the invention, in which parts identical to those of the divider known from the prior art in accordance with  FIGS. 1 to 2  are denoted with like reference numerals. 
     It can be seen from the illustration that the divider also comprises an outer conductor  1  and an inner conductor  11  configured as a coaxial conductor with a housing  1 ′, in which the summation port  4  is arranged at the lower end-face end  1   a  of the housing. In the embodiment shown, said outer conductor  1  has a cylindrical cross-section. However, in a variant the outer conductor  1  may have a square cross-section or generally an n-polygonal or other cross-section, similarly to the embodiment in accordance with the prior art in accordance with  FIGS. 1 and 2 . In this respect there are no limitations. 
     At the opposite end  1   b  of the outer conductor and in contrast with the embodiment according to the prior art in accordance with  FIGS. 1 and 2 , a plurality of single ports is not directly provided but instead a one-piece head piece  31  is used and arranged at the upper end  1   b  of the outer conductor  1  at this point, on which head piece the single port  5   a  is provided in the axial extension of the outer conductor  1  and the other connection ports  5   b  and  5   d  are provided in the peripheral direction relative to the outer conductor  1  and are arranged in a plane so as to be offset relative to one another. In this embodiment two connection ports  5   b  and  5   d  are arranged in the axial direction and point away from one another, a central port  5   c  additionally being provided between said two ports  5   b  and  5   d , which are arranged so as to extend at an angle of 180° relative to one another, and offset by 90° relative thereto, which central port is also arranged so as to be aligned at an angle of 90° relative to the upper port  5   a . However, this 90° orientation is not mandatory. Any other geometrical shapes and orientations are also possible. Generally, an n-polygonal configuration is provided since the aforementioned angle may then also be smaller than 90° between two adjacent connection ports if the n-polygonal shape is, for example, 5-, 6- or 8-sided or more. Annular cross-sections may also be considered in principle. 
     In other words, an interface  33  is provided at the upper end  1   b  of the housing  1 ′ acting as an outer conductor  1 , at which interface a head piece  31  having more than one port (four ports in the embodiment shown) is provided, rather than a single connection port  5   a  as in the prior art (in accordance with  FIGS. 1 and 2 ). 
     The head piece  31  with the single ports  5   a ,  5   b ,  5   c ,  5   d  which form the integral outer conductor connections  105  consists of a forged part, a cast part or a milled part. In other words, the head piece  31  serves as an outer conductor housing in which the single ports  5   a  to  5   d  serving as outer conductor connections  105  form an integral component part of the head piece  31 , i.e. are rigidly connected to the actual portion of the head piece  31  and do not form a positive or non-positive connection but are materially connected (material connection). Material connections are connections in which the connection partners are joined together by atomic or molecular forces. At the same time they are non-detachable connections which can only be separated by destroying the connection means. Solders, welds, etc. are possible material connections. However, the head piece with the outer conductor connections belonging to the head piece is preferably produced from a single part which is positively connected and in the form of a forged part, a cast part or a milled part. If the head piece with the ports (i.e. the outer conductor connection  105 ) is produced by way of a forging process, it should preferably be produced in a warm forging process, including the ports serving as outer conductors (i.e. the outer conductor connections  105 ), in such a way that the head piece, together with the outer conductor connections, forms a single warm forged part which is easily handled. 
     According to the sectional view in accordance with  FIG. 4 , it can further be seen that the inner conductor  11 , which is also sometimes referred to as a transformation inner conductor  11 , is held relative to the outer conductor  1  by means of two annular insulators  113   a  arranged above and with a further annular insulator  113 ′ arranged closer to the stagnation port  4 , the upper narrow insulator rings  113   a  being supported on and inwardly abutting the head piece  31 . These two insulator rings orientate the inner conductor axially, radially and in rotation. As can be seen in  FIG. 6 , the annular insulator  113  which consists of two connectable annular portion insulator portions  113   a  and  113   b  is provided in the embodiment shown with two slightly protruding outer projections offset at 180° from one another which extend in the axial direction. Rotation is prevented in that when the transformation inner conductor  11  is inserted into the outer conductor  1 , these projections  113   c  engage in corresponding longitudinal grooves  105   a  (in the three-dimensional view according to  FIG. 7  one of the two inner grooves  105   a  can be seen at the connection port  5   a ,  FIG. 7  showing the view from below the head piece  31  with the outer conductor  1  removed). 
     In order to prevent any rotation and to fix in place the insulator  113  consisting of the two parts, said insulator is provided on the inside and in the embodiment shown with two (in this case) annular or cylindrical radially inwardly protruding fixing projections  113   d  in the embodiment shown. These fix the respective insulator portion  113   a  or  113   b  to the inner conductor  11 , The inner conductor  11  is thus also provided with a hole or recess  11   a  (shown in  FIG. 4 ), in which one of the annular rings can be clipped until the projection  113   d  engages in said hole  11   a . This hole or blind hole  11   a  is preferably provided with an undercut, it being possible for the projection  113   d  to be made of a suitable material (for example plastics material or Teflon) and to be configured in such a way that when it is inserted there is a slight snapping effect. The second annular portion insulator portion  113   c  may be inserted from the opposite side into a corresponding further hole in the inner conductor in such a way that once these two insulator halves  113   a  and  113   b  have been fixed in place, the annular insulator construction according to  FIG. 6  is obtained and the insulator ring is thus held in place on the inner conductor  11  and thus also prevents the inner conductor from rotating. 
     As can be seen from the drawing according to  FIG. 6 , the insulator halves  113   a  and  113   b  are configured in such a way that, when viewed from above, they extend over slightly more than a 180° annular portion and therefore at their two open end regions are only half as tall so a correspondingly shaped second insulator part rotated through 180° can be connected to the first in such a way that a continuous support ring having the same continuous axial thickness is obtained. 
     According to the invention, the head piece  31  comprises integral connections  105  which form the single ports  5   a  to  5   d . Into these connections  105 , i.e. into the cylindrical or pot-shaped outer conductor of the connections  105 , the inner conductors  115  are inserted, the inner conductors  115  being provided on the connection side (i.e. pointing outwardly) with a barrel spring  115   a  (in which a coaxial connection connector can be inserted via its inner conductor) and in the axial extension of said inner conductors an inner conductor pin  115   b  and an annular insulating support  115   c  being provided. This inner conductor part  115  prefabricated in this manner is inserted into the aforementioned connection  105  and into a corresponding threaded hole  111  via its threaded connection  115   d  on the assembly side, which threaded hole is formed to a corresponding depth in the inner conductor  11 . 
     The head piece  31  itself also comprises on its connection side to the housing  1  a socket-shaped connection  133 , in which the upper end  1   b  of the housing  1  can be screwed via its outer thread into a corresponding inner thread in the connection  133  of the head piece  31 . The transformation inner conductor  11  is thus distanced and centered relative to the head piece  13  in an insulated manner via the aforementioned insulator rings  113 . 
     Instead of the screw connection at the socket-shaped connection  113 , in this case the outer conductor may also be connected to the connection or divider head (what is known as the head piece  31 ) by another suitable connection which allows intermodulation, for example a compression joint, soldered joint or the like. 
     At the summation port  4  a prepared socket with a fixing screw  4   a  can also be unscrewed at an outer thread at the lower end  1   a  of the housing  1 , in fact with a prepared inner conductor  401  comprising outwardly pointing barrel supports  401   a  and an inner conductor pin  401   b  connected axially in the direction of the inner conductor  11 , this unit in turn being held via an annular insulating support  401   c . In this case, the inner conductor  401  is also connected via a threaded connection to the transformation inner conductor  11 . The inner conductor  11  is also held in a centered manner via the insulating support  401   c . Not only the aforementioned upper insulator ring  113  consisting of the two insulator halves  113   a  and  113   b , but also the lower annular insulator support  113 ′ is used to insert the inner conductor  11  into the outer conductor  1 . The insulator  113  and the insulator support  113 ′ thus center the inner conductor  11  since the inner conductor is interrupted between the insulator support  113  and the insulator support  401   c  by the inner conductor pin contact  401   b . The contact  401   b  thus compensates differences in tolerance and length. 
     In a variant of the embodiment shown, a construction identical to that for the other connection ports  5   b  to  5   d  may be selected for the uppermost port  5   a , i.e. a construction with an inner conductor  115  of the same length. In the embodiment shown according to  FIGS. 3 and 4 , this inner conductor, i.e. the inner conductor pin  115   b , is slightly shorter than the inner conductor  115  for the other connection ports  5   b  to  5   d.    
     It can also be seen from the cross-sectional view according to  FIG. 5  that no further single port is provided opposite the single port  5   c  but, in this case, an inwardly blind hole  37  is formed in the material of the head piece  31 . This blind hole  37  is arranged in the direct axial extension of the hole  39  which forms the axial extension hole for the single port  5   c  having a greater internal diameter. The hole  39  thus opens out into a hole  40  arranged in the axial extension of the inner conductor  11  (similarly to the blind hole  37 ), which hole  40  leads to the upper connection  105  of the single port  5   a . This blind hole  37  opposite the front output  5   c  enables symmetrical loading at the outputs, a high level of phase balance and power distribution between the outputs being obtained with extremely simple means.