Patent Publication Number: US-9905903-B2

Title: Resonator filter having a rotatable rod that presses a dielectric material into an elastic spring material

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0047096 filed in the Korean Intellectual Property Office on Apr. 2, 2015, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     (a) Field of the Invention 
     The present invention relates a microwave filter, and in detail, relates to a resonator filter using a dielectric material. 
     (b) Description of the Related Art 
     A microwave filter selecting a desired frequency band determines performance of a wireless telecommunications system. Especially, when the communications system uses many channels, the size and cost reduction of the filter is very important because the same number of filters as the number of channels are used. 
     As the filter used in the wireless communications system, there are filters using a lumped element, a micro-strip or a strip line filter using a transmission line, a resonator filter, a wave guide filter, and a SAW (surface acoustic wave) filter and so forth. 
     Among the various filters as described above, the cavity resonator filter loaded by dielectric material shows a high quality factor, and its mass and volume are relatively small compared with cavity filters without dielectric material. 
     The cavity resonator filter must have an appropriate number of resonators and a required connectivity to realize a preferable frequency response characteristic. In general, since the number of resonators constituting the filter must be high to realize a filter with a sharp roll-off rejection characteristic, the size of the filter gets large. Accordingly, to provide a small-size filter, methods of reducing the size of the resonator itself and the number of resonators have been undertaken by using a cavity resonator of a dual mode or a triple mode in which several resonance modes are realized in one cavity. 
     As high quality wireless system performance is required, a filter having stringent performance has been required. However, as the frequency response characteristic is very sensitive errors can occur when realizing the filter, such as distortion of the frequency characteristic due to a design error or a manufacturing error directly affects the performance of the filter. Therefore, there is a case that the performance requirements of the filter are not satisfied due to a small error. 
     The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
     SUMMARY OF THE INVENTION 
     An exemplary embodiment of the present invention provides a resonator filter reducing the size of the filter and simultaneously easily controlling the resonance frequency of the filter. 
     A resonator filter according to a first exemplary embodiment of the present invention includes: a cover formed with a first coupling hole; a housing connected to the cover to form an inner space and having a second coupling hole formed at a bottom of the inner space; a dielectric material mounted around the second coupling hole in the bottom of the inner space of the housing; a first rod inserted to the first coupling hole to be connected to the cover and pressing the dielectric material; and a second rod inserted to the second coupling hole to be connected to the housing to be close to the dielectric material and tuning a resonance frequency by controlling a separation distance from the first rod. 
     The first coupling hole and the first rod may be screw-coupled. 
     The first rod may have a coupling groove to allow a rotary tool to rotate the first rod. 
     The dielectric material may be formed with a hollow portion to be penetrated by the second rod. 
     The first rod may include an adhesive member to be fixed to the first coupling hole. 
     The second coupling hole and the second rod may be connected by screw-coupling. 
     The second rod may include a fixing nut close to the housing outside and fixing an insertion length of the second rod. 
     The dielectric material may include an elastic member within the housing. 
     The housing may include a mounting groove mounted with the dielectric material at the bottom thereof. 
     A resonator filter according to a second exemplary embodiment of the present invention includes: a cover formed with a first coupling hole; a housing connected under the cover and forming a space that is enclosed; a dielectric material positioned at a bottom of the housing inner space; a first rod inserted to the first coupling hole of the cover, pressing the dielectric material, and formed with a hollow portion; and a second rod inserted to the hollow portion of the first rod, close to the dielectric material, and controlling a separation distance from the housing bottom to tune a resonance frequency. 
     The first coupling hole and the first rod may be connected by screw-coupling. 
     The dielectric material may be formed with the hollow portion to be penetrated with the second rod. 
     The dielectric material may include an elastic member within the housing. 
     The housing may include a mounting groove mounted with the dielectric material at the bottom thereof. 
     A fixing nut fixing an insertion length of the second rod between the first rod and the second rod may be further included. 
     The first rod may include an adhesive member at the cover. 
     In the resonator filter according to the present exemplary embodiments, the first rod and the dielectric material are contacted with each other, and when thermal deformation due to a temperature change is generated, damage to the dielectric material due to the thermal deformation may be prevented by the elastic member capable of absorbing the thermal deformation. 
     Also, the size of the resonator filter may be reduced and simultaneously the resonance frequency of the filter may be easily controlled. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective exploded view of a resonator filter according to a first exemplary embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of a resonator filter according to a first exemplary embodiment of the present invention. 
         FIG. 3  is a top plan view of a resonator filter according to a first exemplary embodiment of the present invention. 
         FIG. 4  is a cross-sectional view of a resonator filter according to a second exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. 
     Parts unrelated to the description of the exemplary embodiments are not shown to make the description clear, and like reference numerals designate like element throughout the specification. 
     The size and thickness of the configurations are optionally shown in the drawings for convenience of description, and the present invention is not limited to the drawings. 
     In addition, unless explicitly described to the contrary, the word “comprise” and variations such as “comprises” or “comprising” will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. 
       FIG. 1  is a perspective exploded view of a resonator filter according to a first exemplary embodiment of the present invention, and  FIG. 2  is a cross-sectional view of a resonator filter according to a first exemplary embodiment of the present invention. 
     Referring to  FIG. 1  and  FIG. 2 , in a resonator filter  100  according to the present first exemplary embodiment, a housing  20  formed with a second coupling hole  25  is connected to a cover  10  formed with a first coupling hole  15 , and a dielectric material  50  is positioned inside the housing  20 . A first rod  30  for pressing the dielectric material  50  is connected to the cover  10 , and a second rod  40  is connected to the housing  20 . 
     The first coupling hole  15  is formed in the cover  10  and the first rod  30  is coupled to the first coupling hole  15 . The position of the first coupling hole  15  may be in one line with the dielectric material  50 . A thread may be formed in an interior circumference of the first coupling hole  15 . Accordingly, the first rod  30  may be connected to the first coupling hole  15  by screw-coupling. The first rod  30  may further include a rotary tool coupling groove  35  so that the rotation is easily performed by a rotary tool such as a driver. 
     The housing  20  formed with the second coupling hole  25  connected under the cover  10 . The position of the second coupling hole  25  may be in one line with the first coupling hole  15 . The thread may be formed in an interior circumference of the second coupling hole  25 . Accordingly, the second rod  40  may be connected to the second coupling hole  25  by the screw-coupling. The second rod  40  may have a bolt shape. 
     The dielectric material  50  is positioned inside the housing  20 . The dielectric material  50  has a larger diameter than the second coupling hole and may be mounted in the second coupling hole  25 . A hollow portion  52  ( FIG. 1 ) may be formed in the dielectric material  50  to be circular. The dielectric material  50  may be positioned with a segmented shape around the second rod  40 . Accordingly, the second rod  40  may be connected to be close to the dielectric material  50 . The second rod  40  may communicate with the hollow portion  52  of the dielectric material  50 . In this case, the second rod  40  penetrates the dielectric material  50  and may control a separation distance G ( FIG. 2 ) from the first rod  30  in the dielectric material  50 . Capacitance is determined depending on a length between the second rod  40  and the separation distance G of the first rod  30 . A user may tune the required resonance frequency by increasing or decreasing the separation distance G with the first rod  30  while rotating the second rod  40 . A fixing nut  45  fixing the insertion length of the second rod  40  when the tuning of the resonance frequency is completed may be further included. The fixing nut  45  is installed outside the housing  20 . 
     The first rod  30  presses the dielectric material  50  to fix the dielectric material  50 . The first rod  30  may be cylindrical of which a center is empty to reduce the weight thereof. 
     An elastic member  55  may be positioned between the dielectric material  50  and the housing  20 . The elastic member  55  may have the same shape as the dielectric material  50 . The elastic member  55  has a function of alleviating thermal stress generated by a thermal expansion difference between the dielectric material and other parts when the dielectric material  50  is pressed by the first rod  30  or when thermal deformation is generated. The elastic member  55  may be a spring. 
     The housing  20  may further include a mounting groove  27  that is mounted and coupled to be inserted with the dielectric material  50  at a bottom thereof. By forming the mounting groove  27  at the bottom of the housing  20 , the dielectric material  50  may be prevented from being moved inside the housing  20  and the entire height of the filter may be reduced, and the dielectric material  50  is inserted to the mounting groove  27  along with the elastic member  55 , thereby assembly may be easy. 
       FIG. 3  is a top plan view of a resonator filter according to a first exemplary embodiment of the present invention. 
     Referring to  FIG. 3 , an adhesive member  60  is further included between the first coupling hole  15  ( FIGS. 1 and 2 ) formed in the cover  10  and the first rod  30  ( FIGS. 1 and 2 ). If the first rod  30  contacts the dielectric material  50  to determine the insertion length, the first rod  30  is adhered to the first coupling hole  15  by the adhesive member  60 . Accordingly, the first rod  30  cannot be moved such that the insertion length of the first rod  30  inserted to the housing  20  may be prevented from being changed. The adhesive member  60  may be made of welding. 
       FIG. 4  is a cross-sectional view of a resonator filter according to a second exemplary embodiment of the present invention. 
     Referring to  FIG. 4 , the housing  20  is connected to the cover  10  formed with the first coupling hole  15 , and the dielectric material  50  is disposed inside the housing  20 . The first rod  30  is formed with the hollow portion and may be connected to the first coupling hole  15 . The second rod  40  is inserted to the hollow portion of the first rod  30  and penetrates the dielectric material  50 , thereby controlling the separation distance G ( FIG. 2 ) from the housing bottom. 
     The first rod  30  formed with the hollow portion in the center is connected to the first coupling hole  15 . The adhesive member  60  fixing between the first rod  30  may be further included in the first coupling hole  15 . 
     The second rod  40  is inserted in the hollow portion of the first rod  30  to be connected. The second rod  40  and the first rod  30  may be screw-coupled. When the insertion length of the second rod  40  is determined between the second rod  40  and the first rod  30 , the fixing nut  45  fixing the length may be installed. 
     While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 
     
       
         
           
               
             
               
                   
               
               
                 &lt;Description of symbols&gt; 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 100: resonator filter 
                 10: cover 
               
               
                   
                  15: first coupling hole 
                 20: housing 
               
               
                   
                  25: second coupling hole 
                 27: mounting groove 
               
               
                   
                  30: first rod 
                 35: coupling groove 
               
               
                   
                  40: second rod 
                 45: fixing nut 
               
               
                   
                  50: dielectric material 
                 52: hollow portion 
               
               
                   
                  55: elastic member 
                 60: adhesive member 
               
               
                   
                 G: separation distance