Abstract:
A phase-shifting system for electrically swiveling the direction of a beam of an antenna field includes several radiators with two planes of polarization. The phase-shifting system includes two jointly changeable phase shifters with microstrip lines associated therewith. The electrical length of each phase shifter can be changed by a dielectric which is slidable above the microstrip lines. Such a phase-shifting system offers a simplified design and added functional safety by arranging the microstrip lines of both phase shifters in parallel next to each other and by providing a common slidable dielectric in order to change the electrical length of the microstrip lines of both phase shifters.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the field of radiofrequency engineering. It relates to a phase shifter arrangement and an antenna array having such a phase shifter arrangement. 
   2. Description of Related Art 
   In mobile radio technology, antenna arrays or antennas, in which two or more individual radiators are arranged one behind the other in a mounting direction and are driven via a common supply network, have long been known for equipping the base stations. In order to be able to take better account of the different conditions at the location of the respective base station and of the interaction with other base stations, it has proved to be advantageous to provide the antennas with the possibility of a “down tilt”. This may take place, in principle, by purely mechanical means by the antenna being designed such that it can be adjusted at the point at which it is fixed to the mast. One disadvantage of this is the fact that considerable complexity is required to adjust and alter such a mechanical down tilt and it is usually necessary to climb the mast for this purpose. 
   Several suggestions have therefore been made to carry out an “electrical down tilt” by, in the case of a fixed antenna, the individual radiators of the antenna or the antenna array being driven on different phases such that the radiation lobe formed by superimposing the phase-shifted arrays of individual radiators is tilted in a desired manner (“phased array”). Examples of such an electrical “down tilt” are disclosed in U.S. Pat. No. 6,198,458 or in U.S. Pat. No. 5,801,600 or in U.S. Pat. No. 5,905,462. Used here are special differential phase shifters (see also DE-A1-199 11 905 or U.S. Pat. No. 5,949,303) or other phase shifters which are arranged in the supply network of the antenna between the individual radiators and can be adjusted at the same time, for example, via a linkage by means of a motor drive (see also U.S. Pat. No. 5,798,675). The simple, electrically controllable adjustability in this case also provides the possibility of remote adjustment from a control center or the like (“remote tilt control”). 
   Combinations of mechanical and electrical down tilts are likewise conceivable (U.S. Pat. No. 5,440,318). 
   In more recent mobile radio transmission methods having a high data transmission rate, as are known, for example, by the abbreviation UMTS, the transition is increasingly being made to using “dual polarized antennas” in order to be able to make use of the effect of “polarization diversity” in which multiple transmission of data is possible on radio waves having a different polarization for the purpose of increasing transmission reliability. The radiators in these antennas in this case each have two radiator elements for the two polarizations and are in the form of, for example, cruciform dipoles or correspondingly designed patch radiators. 
   The document U.S. Pat. No. 6,310,585 discloses an electrically controlled down tilt by means of phase shifters for the dual polarized antennas or antenna arrays. For this purpose, each of the two radiator elements of a radiator within the supply network has in each case one associated phase shifter (40 in FIG. 1; 440 in FIG. 3), in which, for example, a microstrip line is overlapped to a greater or lesser extent by a displaceable dielectric (column 3, lines 61-65; column 5, lines 1-18). Details on the phase shifters and the associated microstrip lines are not given in the document. 
   In U.S. Pat. No. 6,310,585, the phase shifters for all of the radiator elements of one polarization direction are rigidly coupled mechanically to one another by means of a first rod. The phase shifters for all of the radiator elements of the other polarization direction are likewise rigidly coupled to one another mechanically by means of a second rod. The two rods, for their part, are rigidly connected to one another by means of a central supporting device (415 in FIG. 3) and are driven by a pinion via a toothed rack. In addition, two or more flexible positioning elements (420 in FIG. 3) are provided which press the dielectric against the microstrip lines below. 
   Disadvantages of this known phase shifter arrangement are not only the complex displacement mechanism comprising a plurality of individual elements, but also the separate structure of the individual phase shifters which requires high accuracy on assembly and thus increased mounting complexity with, at the same time, increased susceptibility to faults. 
   SUMMARY OF THE INVENTION 
   The present invention is a phase shifter arrangement that avoids the disadvantages of the known phase shifter arrangements, such that the design is simplified and the desired functionality is reliably achieved, as well as an antenna array having such a phase shifter arrangement. 
   The invention includes arranging the microstrip lines of the two phase shifters parallel and next to one another, and providing a common, displaceable dielectric for the purpose of altering the electrical length of these microstrip lines of the two phase shifters. In this manner, only a single displaceable dielectric is required per radiator, and this may be used to automatically and synchronously adjust the electrical length for the two polarizations. There is thus also only a single row of dielectrics arranged one behind the other provided in the mounting direction of the antenna array, and this row of dielectrics may be displaced at the same time in a particularly simple manner by means of a single rod extending in the longitudinal direction. 
   In particular, the microstrip lines and the displaceable arrangement of the dielectric are designed such that the electrical length of the two parallel microstrip lines is altered to the same extent when the dielectric is displaced. This ensures that the radiation lobe always has the same orientation for the two polarizations. 
   In principle, it would also be conceivable to displace the dielectrics of the phase shifter arrangements transversely with respect to the mounting direction of the antenna array. However, particularly simple is the mechanical system whereby, according to a preferred refinement of the invention, the microstrip lines extend essentially along a longitudinal axis, and the dielectric can be displaced in the direction of the longitudinal axis. 
   The microstrip lines preferably each have at least one center piece which is completely overlapped by the displaceable dielectric in a first position and is left completely free in a second position. In this case, it is favorable for the setting characteristics if the microstrip lines in the center pieces run transversely with respect to the longitudinal direction and have a meandering structure, since the electrical length is thus altered to a greater extent per unit of the displacement path. 
   Already disclosed in U.S. Pat. No. 3,656,179 is a way of altering the associated characteristic impedance by displacing the dielectric in a bus strip arrangement. In order to reduce the degree of alteration to the characteristic impedance to a tolerable level, another refinement of the invention provides for two or more line sections running parallel in the longitudinal direction to be provided within the meandering structure, and for the microstrip lines to alter their strip width in the line sections running in the longitudinal direction. 
   The alteration to the strip width is preferably designed such that, when the dielectric is displaced from the second to the first position, the strip width of the overlapped line sections, starting from a minimum strip width, increases as the overlap increases up to a maximum strip width, in particular the strip width increasing linearly with the displacement path in the longitudinal direction. 
   Particularly advantageous variation of the characteristic impedance by an average value results when the minimum strip width is selected such that, when there is an overlap with the dielectric in the region of the minimum strip width, the same characteristic impedance of the microstrip lines is produced as in the region of the maximum strip width where there is no overlap with the dielectric. This type of alteration to the strip width is advantageous for each phase shifter which operates with the displacement of a dielectric above a microstrip line, and specifically independently of whether two or more phase shifters have a common dielectric or not. 
   In addition, adjusting pieces having a differing strip width can be arranged in the line sections running in the longitudinal direction for the purpose of adjusting the characteristic impedance. 
   The phase shifter arrangement according to the invention is simplified further if the microstrip lines of the two phase shifters are arranged and formed on a common printed circuit board. Together with the common, displaceable dielectric, there is thus a high degree of synchronization with, at the same time, a particularly simple design. 
   One possible refinement of the printed circuit board consists in the microstrip lines of the two phase shifters being designed to be mirror-symmetrical with respect to a center axis, running parallel to the longitudinal axis, of the printed circuit board. 
   In order for the displaceable dielectric to always be in a defined position relative to the microstrip lines below, it is advantageous if the microstrip lines of the two phase shifters and the common dielectric above are pressed flat against one another by means of a spring metal sheet. 
   A particularly uniform pressing action results when the spring metal sheet is arranged on the underside of the microstrip lines and is electrically insulated from the microstrip lines by means of an intermediate insulating plate, and if the spring metal sheet has a plurality of individual spring tongues distributed over its surface. 
   Provided for the drive of the phase shifter is preferably a slide which is guided displaceably in the longitudinal direction, can be actuated manually from the outside or using a motor, and is in engagement with the dielectric. This configuration is particularly simple and functionally reliable and has the advantage of retaining its position when the motor drive fails. 
   It has proven successful in practice to use a plate having a relative dielectric constant of approximately 10, in particular in the form of a glass fiber-reinforced, organoceramic laminate, as the dielectric. 
   A preferred refinement of the antenna array according to the invention is characterized in that two or more phase shifter arrangements which can be displaced at the same time are arranged one behind the other within the supply network, and in that connections are provided between and downstream of the phase shifter arrangements for the purpose of connecting the radiators. 
   Another preferred refinement is distinguished by the fact that radiators are arranged in the antenna array 2n+1 (n=1, 2, 3, . . . ), that 2n phase shifter arrangements are arranged one behind the other in the associated supply network, that the supply inputs are connected to the supply network between the n-th and the (n+1)-th phase shifter arrangement, and that all of the phase shifter arrangements can be actuated at the same time, the first n phase shifter arrangements operating in opposition to the second n phase shifter arrangements. 

   
     DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in more detail below with reference to exemplary embodiments in connection with the drawing, in which: 
       FIG. 1  shows a cross section ( FIG. 1A ), a plan view from above ( FIG. 1B ) and a longitudinal section ( FIG. 1C ) through an individual phase shifter arrangement comprising two phase shifters according to a preferred exemplary embodiment of the invention; 
       FIG. 2  shows the base plate of the phase shifter arrangement shown in  FIG. 1 ; 
       FIG. 3  shows an insulating film of the phase shifter arrangement shown in  FIG. 1 ; 
       FIG. 4  shows a plan view ( FIG. 4A ) and a side view ( FIG. 4B ) of the spring metal sheet of the phase shifter arrangement shown in  FIG. 1 ; 
       FIG. 5  shows an insulating plate of the phase shifter arrangement shown in  FIG. 1 ; 
       FIG. 6  shows the printed circuit board having the two microstrip lines of the phase shifter arrangement shown in  FIG. 1 ; 
       FIG. 7  shows the dielectric of the phase shifter arrangement shown in  FIG. 1 ; 
       FIG. 8  shows a plan view from above ( FIG. 8A ) and a side view from the front ( FIG. 8B ) of the slide of the phase shifter arrangement shown in  FIG. 1 ; 
       FIG. 9  shows the plan view of two sides ( FIGS. 9A  and B) of a printed circuit board having 8 phase shifter arrangements according to the invention for an antenna array having in total 9 radiators; and 
       FIG. 10  shows the simplified circuit diagram for the antenna array shown in  FIG. 9 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 10  shows the simplified circuit diagram of an antenna array  105 , in which the present invention can advantageously be used. The antenna array comprises in total 9 radiators  106 , . . . ,  114 , which are arranged one behind the other (one on top of the other) in a (vertical) mounting direction. Each of the radiators  106 , . . . ,  114  comprises two individual radiator elements  106   a, b  (the reference numerals for the radiator elements in the radiators  107 , . . . ,  114  are omitted for clarity). Each of the radiator elements  106   a, b  is associated with one polarization direction. The two polarization directions are generally at right angles to one another and usually form an angle of 45° with the mounting direction of the antenna array  105 . The radiators  106 , . . . ,  114  are provided both for emitting and receiving radio waves. 
   The radiators  106 , . . . ,  114  or radiator elements  106   a, b  are connected, via a supply network  115 , to two supply inputs  99   a, b , which are arranged within the supply network  115  at the level of the central radiator  110 . Each of the two supply inputs  99   a, b  is assigned one of the polarization directions and is connected to the corresponding radiator elements. In order for the radiators  106 , . . . ,  114  to be able to form a “phase array” and to emit and receive an electrically pivotable beam, phase shifters  91   a, b , . . . ,  98   a, b , are arranged in pairs distributed in the supply network  115 . Each pair of phase shifters  91   a, b , . . . ,  98   a, b  forms a phase shifter arrangement. The two phase shifters of a pair of phase shifters or of a phase shifter arrangement are adjusted in synchrony, as is illustrated in  FIG. 10  by the dashed connecting lines within each pair. All of the phase shifter pairs  91   a, b , . . . ,  98   a, b  are actuated at the same time by a connecting tongue  116  running in the longitudinal direction (mounting direction), which is driven manually or using a motor and is likewise illustrated using dashed lines in  FIG. 10 . The change in the phase shift in the phase shifters  95   a, b , . . . ,  98   a, b  arranged below the supply inputs  99   a, b  takes place in this case in opposition to the change in the phase shift in the phase shifters  91   a, b , . . . ,  94   a, b  arranged above the supply inputs  99   a, b  (i.e. an increase in the phase shift at the bottom corresponds to a decrease in the phase shift at the top, and vice versa), which is indicated in  FIG. 10  by the arrows in the phase shifters having a different orientation. 
   The central one of the 9 radiators  106 , . . . ,  114 , namely the radiator  110 , is connected directly to the supply inputs  99   a, b  and thus operates on a constant phase. The remaining 8 radiators  106 , . . . ,  109  and  111 , . . . ,  114  each have an associated phase shifter pair. Since the phase shifter pairs  91   a, b , . . . ,  98   a, b  are connected in series within the supply network  115 , the individual phase shifts, starting from the center, are summed. If all of the phase shifters are the same, the phase shift toward the outside increases in equal increments: the signal supplied to the supply inputs  99   a, b  reaches the radiator  109  with a single phase shift, the radiator  108  with a dual phase shift, the radiator  107  with a triple phase shift, and the radiator  106  with a quadruple phase shift. The same applies for the radiators  111  to  114 . 
   A single phase shifter pair or a single phase shifter arrangement now preferably has a construction as is shown in the exemplary embodiment in  FIGS. 1 to 8 , in which, in  FIG. 1 , different views are depicted of a completely assembled arrangement, whereas  FIGS. 2 to 8  show the individual elements of the arrangement shown in  FIG. 1  in sequence within the arrangement. The printed circuit board  60  shown in  FIG. 6  and having the microstrip lines  66 ,  67  in this case only represents the subsection of a longer printed circuit board  90 , as is reproduced in  FIG. 9  for the entire antenna array  105  shown in  FIG. 10 . 
   The printed circuit board  60  ( FIG. 6 ), which is made of, for example, a base material of 0.5 mm in thickness having a double-sided 35 μm Cu coating, has, on the underside, a continuous Cu coating and, on the top side, the conductor tracks shown which are mirror-symmetrical with respect to a center axis  11  and form the microstrip lines  66 ,  67 . The printed circuit board  60  is arranged in the phase shifter arrangement  10  in  FIG. 1  between a (lower) base plate  20  ( FIG. 2 ) and an (upper) slide  80  ( FIG. 8 ) such that the conductor tracks of the microstrip lines  66 ,  67  are on the side of the slide  80 . The base plate  20 , which may be in the form of, for example, an aluminum plate, has, on the sides, two fastening tabs  21 ,  22  having corresponding fastening holes  23 ,  24 , by means of which it can be screwed tightly to an antenna housing. 
   The printed circuit board  60  is fixed in relation to the base plate  20 . This is achieved by two lugs  25 ,  26  which engage in corresponding openings  64 ,  65  in the printed circuit board  60  ( FIG. 6 ) being bent back upward at right angles on the base plate  20 . Also provided in the printed circuit board  60  are three guide openings  61 , . . . ,  63  in the form of slots which are spaced apart from one another, run parallel to the center axis  11 , and in which the slide  80  engages with correspondingly formed and arranged engaging cams  81 , . . . ,  83  ( FIG. 1 ;  FIG. 8 ). The guide openings  61 , . . . ,  63  determine the displacement region of the slide  80  relative to the printed circuit board  60 . 
   The slide  80 , which may be made of, for example, plastic and may be an injection-molded part, also has two lateral guides  86 ,  87  which engage over the lateral edge of the printed circuit board  60 . On its top side of the slide  80 , integrally formed in a depression and one behind the other in the longitudinal direction, are two driver cams  88 ,  89  with which an actuating element (not shown) for the slide can engage. Furthermore, two recesses  84 ,  85  are provided on the slide  80  in order to provide space for the lugs  25 ,  26  protruding through the printed circuit board  60  from below. 
   The actual phase shifters  10   a ,  10   b  of the phase shifter arrangement  10  are formed by the interaction of the microstrip lines  66 ,  67  with a dielectric  70  arranged displaceably on the top side of the printed circuit board  60 . The dielectric  70  shown in detail in  FIG. 7  comprises, for example, an organoceramic laminate of the CER-10 type, as can be procured from the US company Taconic, Petersburgh, N.Y. (USA). The glass fiber-reinforced laminate filled with ceramic has a dielectric constant of 10 and very good mechanical properties. A plate of this material is used having a thickness of approximately 0.64 mm. Other dielectrics are also conceivable, however. According to  FIG. 7 , the dielectric  70  has three circular engaging openings  71 , . . . ,  73  which are spaced apart from one another and in which the slide  80  engages with its engaging cams  81 , . . . ,  83 . The dielectric  70  is thus fixed in relation to the slide  80  and is displaced along with the slide  80 . Furthermore, two recesses  74 ,  75  are provided in the dielectric  70  which are comparable in shape and function to the recesses  81 ,  82  of the slide  80 . 
   The interaction of the microstrip lines  66 ,  67  and the dielectric  70  takes place essentially in the region of the meandering center pieces  66   b ,  67   b  of the microstrip lines  66 ,  67  which are each arranged between connection pieces  66   a, c  and  67   a, c  and run transversely with respect to the center axis  11  ( FIG. 6 ). Each of the center pieces  66   b ,  67   b  comprises two or more (in the example in  FIG. 6 ,  5 ) line sections  66   d , . . . , h , which run parallel to the center axis  11  and are connected to one another for the purpose of forming the meandering pattern on alternating sides by means of U- or V-shaped bent pieces. Within the line sections  66   d, . . . , h , the line width varies linearly with respect to the length and in the process decreases from left to right. Since the dielectric  70  with its left-hand edge moves when being displaced precisely in the region of the line sections  66   d, . . . , h , when the dielectric is displaced, regions of the line sections  66   d, . . . , h  having different line widths are covered or not covered. 
   There is a particular reason for the variation in the line width of the line sections  66   d, . . . , h : In order to maintain the (conventional) characteristic impedance of the microstrip lines  66 ,  67  of 50 ohms, the line width in the case of the materials and dimensions used is approximately 1.5 mm (without a dielectric on top). In the region of the dielectric on top, however, only a line width of approximately 0.98 mm is required for a characteristic impedance of 50 ohms owing to the dielectric. Therefore, if the line width outside the region of coverage of the dielectric is set at 1.5 mm and at 0.98 mm in the region of continuous coverage and a linear transition between these two extreme values is assumed in the intermediate line sections  66   d, . . . , h , the deviation of the actual characteristic impedance when the dielectric  70  is displaced varies by the average value of 50 ohms, the characteristic impedance being more than 50 ohms if the dielectric  70  is shifted to the left far beyond the line sections  66   d , . . . , h, and being less than 50 ohms if the dielectric  70  is shifted only slightly beyond the line sections  66   d, . . . , h . Since only the absolute value of the difference is relevant for the (undesired) erroneous adjustment, and not the mathematical sign, a larger displacement region of the dielectric and thus a larger phase shift over a larger frequency range can thus be obtained utilizing the maximum permissible erroneous adjustment. In addition, it is possible for the electrical properties to be optimized by adjusting pieces  68 ,  69  being provided which are wider in the center pieces  66   b ,  67   b  ( FIG. 6 ). 
   The two microstrip lines  66 ,  67  are (as can easily be seen in  FIG. 6 ) formed and arranged such that they are mirror-symmetrical with respect to the center axis  11 . The dielectric  70  is selected to be so wide that, in the event of a displacement in the direction of the center axis  11 , the meandering center pieces  66   b ,  67   b  of the microstrip lines  66 ,  67  are overlapped or left free in the same manner. This makes it possible, without high complexity and with functional reliability to achieve synchronization between the two phase shifters  10   a  and  10   b  and to make the phase shifts in the two phase shifters  10   a, b  largely uniform. 
   However, an essential element ensuring functional reliability is the fact that the dielectric  70  bears tightly against the surface of the printed circuit board  60  carrying the microstrip lines  66 ,  67 , if possible without an air gap. This is achieved by means of a flat spring metal sheet  40  ( FIGS. 4A , B) which is arranged between the base plate  20  and the printed circuit board  60  and presses the printed circuit board  60  from below against the dielectric  70  held in the slide  80 . The spring metal sheet  40  has (as does the base plate  20 ) lateral fastening tabs  41 ,  42  having corresponding fastening holes  43 ,  44  which are aligned with the fastening holes  23 ,  24  in the base plate  20 . Arranged distributed over the surface of the spring metal sheet  40  is, next to one another, a large number of individual spring tongues  45  which have been produced, for example, from the spring metal sheet  40  by a stamping or bending process. The spring metal sheet  40  is electrically insulated from the base plate  20  by means of an intermediate, thin insulating film  30  ( FIG. 3 ) which matches the base plate  20  and the spring metal sheet  40  in terms of the lateral fastening tabs  31 ,  32  and fastening holes  33 ,  34 . The spring metal sheet  40  is furthermore electrically insulated with respect to the lower Cu layer of the printed circuit board  60  by means of an intermediate, for example 0.5 mm thick, insulating plate  50  ( FIG. 5 ), against which the spring tongues  45  press. The insulating plate has openings  54 ,  55 , through which the lugs  25 ,  26  of the base plate  20  pass through for fixing purposes. The slot-like guide openings  51 ,  53  are analogous to the guide openings  61 , . . . ,  63  in the printed circuit board  60  in terms of function and shape. 
   The exemplary embodiment shown in  FIGS. 1 to 8  relates only to a phase shifter arrangement comprising two phase shifters  10   a ,  10   b  which is correspondingly only suitable for adjusting a dual polarized radiator. If, as is shown in  FIG. 10 , an antenna array  105  comprises more than two, for example 9, radiators  106 ,  107 ,  108 ,  109 ,  110 ,  111 ,  112 ,  113  and  114 , and two or more, in the example, eight phase shifter arrangements are required for electrically pivoting the antenna beam, these phase shifter arrangements, together with the supply network  115 , are preferably integrated on a single printed circuit board. Such a printed circuit board  90  for in total 9 radiators and 8 phase shifter arrangements is reproduced in  FIG. 9 . Formed on this printed circuit board  90  are, mirror-symmetrically with respect to the center axis  11 , two microstrip lines  90   a ,  90   b  having branches which at the same time form a supply network with the power distributed over two or more antenna connections  102   a ,  102   b ,  103   a ,  103   b ,  104   a ,  104   b  (for simplicity only the antenna connections for 4 radiators are provided with reference numerals in  FIG. 9B ; in total there are antenna connections for 9 radiators or 18 radiator elements). 
   Formed within the supply network of the microstrip lines  90   a, b  are, in analogy to  FIG. 6 , meandering center pieces  91   a, b , . . . ,  98   a, b  which are each part of a phase shifter arrangement  91 , . . . ,  98  comprising two phase shifters. The supply inputs  99   a, b  are arranged in the center of the printed circuit board  90 . Each of the phase shifter arrangements  91 , . . . ,  98  is assigned (in analogy to  FIGS. 1 to 8 ) a dielectric which can be displaced by means of a slide, a base plate, and a spring metal sheet which is mounted such that it is insulated. Correspondingly, in each of the phase shifter arrangements  91 , . . . ,  98 , guide openings  100  and openings  101  are provided for engagement of the base plate. The (nine) slides of all of the phase shifter arrangements  91 , . . . ,  98  are in engagement with a common actuating element (not shown) which extends along the center axis  11  over the entire printed circuit board  90  and can be displaced in the longitudinal direction manually from the outside or by means of a controlled motor drive. 
   In Summary the Following can be Said: 
   Phase shifters are required to achieve a variable down tilt in the case of an antenna array. It must be possible for the main lobe of the antenna to be lowered beyond the horizontal at least to a first zero position. In mobile radio engineering (GSM, UMTS), it is necessary to fulfill the following requirements: 
   In the case of large antennas, it must be possible to alter the down tilt between 0° and approximately 8°; for this purpose, it must be possible for the phase to be altered continuously between 0° and approximately 45° by means of the phase shifter. 
   In the case of small antennas, it must be possible to alter down tilt between 0° and approximately 16°; for this purpose, it must be possible for the phase to be altered continuously between 0° and approximately 85° by means of the phase shifter. 
   There are several possible ways of altering the phase. The following relationship applies between the electrical and the mechanical length of a line:
 
 I   elec   =I   mech √{square root over (∈ r )}
 
   The electrical length is proportional to the phase: 
   
     
       
         
           φ 
           = 
           
             
               
                 I 
                 elec 
               
               λ 
             
             ⁢ 
             360 
             ⁢ 
             ° 
           
         
       
     
   
   In order to alter the phase, the mechanical length or the ∈ r  can be altered. 
   A patent has already been applied for by the applicant for a phase shifter with means for altering the mechanical length of the line. 
   A phase alteration by altering the ∈ r  can be achieved in the case of a microstrip line by a dielectric being laid on the line (see DE-A1-199 11 905). 
   According to the present solution, two or more line sections lying parallel and next to one another are connected to one another by a 180° corner to form a meandering structure. A dielectric having a high ∈ r  is pushed over this line structure, a common dielectric being used for two adjacent phase shifters. The maximum possible phase shift is given by the number of line sections and their length which at the same time corresponds to the displacement path of the dielectric. 
   Using 5 parallel line sections, a phase shift of 46° is achieved; with 7 parallel line sections, a phase shift of 65° is achieved. In order to achieve an even greater phase shift, two or more phase shifters can be connected one behind the other. 
   By using an uneven number of line sections lying parallel and next to one another, the phase shifter can be integrated very effectively in a supply network. However, the phase shifter may also be realized using an even number of lines, which may be more advantageous for other applications. 
   Each individual line section in the phase shifter has a line width which can be altered linearly (is linearly tapered). In the 0° position of the phase shifter (the dielectric is not over the line sections), the line width is narrower and is of such a width that, together with the dielectric pushed on top of it, the system impedance (50Ω) is given. At the other end of the line sections, the line width corresponds to the normal microstrip. Despite the tapered line sections, depending on the position of the displaceable dielectric, there is an erroneous adjustment. Erroneous adjustment may be compensated for by small adjusting pieces (“stubs”) in the line structure. 
   The phase shifter operates as follows: a base plate made of aluminum is screwed onto the antenna housing and positions, by means of two bent-back lugs, the printed circuit board having the line structure. The displaceable dielectric is located on the printed circuit board. Between the aluminum plate and the printed circuit board is a spring metal sheet which presses the printed circuit board against the dielectric. The printed circuit board (ground), the spring metal sheet and the aluminum plate are insulated from one another by additional insulators. 
   It is possible to use a substrate having a high ∈ r  as the dielectric. This thin platelet is held by an additional plastic part (slide), which also has driver cams for the slide apparatus. It is also possible, by selecting a suitable plastic or a ceramic, for the dielectric platelet and the plastic part to be integral. 
   The phase may be set by means of a manually or electrically operated drive.