Abstract:
A coupling device with electro-magnetic compensation is provided. The coupling device includes a first substrate having a first signal line on a top surface of the first substrate and a second substrate having a second signal line on a top surface of the second substrate connected together with a bottom surface of the first substrate wherein the second signal line couples with the first signal line by a plurality of electrical-conductive through holes. One side of the first signal line lies a capacitor device parallel connected to a ground and the capacitor device plays the role of adjusting the amount of return loss, isolation capacity, and coupling effect so as to have transmitting speeds in first and second signal lines remain substantially the same and superior high frequency characteristics.

Description:
BACKGROUND OF THE INVENTION 
   Background 
   1. Field of the Invention 
   The present invention relates to a coupling device, and more particularly, to a coupling device with electro-magnetic compensation with the use of a parallel-connected capacitor device to the ground for adjusting the amount of return loss and isolation and getting the amount of coupling effect and output to a level as expected in order to obtain a better high frequency characteristic. 
   2. Description of the Prior Art 
   Please refer to  FIG. 10  where a prior art broadside coupler  5  includes an upper layer signal line  51  and a lower layer signal line  52  attached to substrates  53  and  54 , respectively. The upper signal line  51  couples with the lower signal line  52  by a plurality of electrical conductive through holes  55 . A medium layer (substrate)  53  is between the upper layer signal line  51  and the lower layer signal line  52 . The prior art coupling device  5  further includes an input end  56 , a coupling end  57 , an output end  58 , and an isolation end  59 .  FIG. 8A  shows the result after having above mentioned ends measured and is indicative of inferior amount of return loss and isolation capacity with the amount of coupling effect and outputting not reaching to a level as anticipated. 
   The amount of coupling effect, return loss, and isolation capacity depend on the line width of the upper layer signal line  51  and the lower layer signal line  52  and the thickness of the medium layer between the upper layer signal line  51  and the lower layer signal line  52 . For the sake of obtaining better return loss and isolation capacity, the change to the line width of the upper layer signal line  51  and the lower layer signal line  52  or the thickness of the medium layer between the upper layer signal line  51  and the lower layer signal line  52  is inevitable, which is not preferred here. 
   Furthermore, the coupling device  5  couples the signal of the upper layer signal line  51  with that of its lower layer counterpart  52  through the medium layer between  51  and  52  and as the result odd/even mode problems would arise and the transmitting speeds of signals in the upper layer signal line  51  and the lower layer signal line  52  are different, leading to the inferior high frequency characteristic. 
   SUMMARY OF THE INVENTION 
   It is therefore a primary objective of the present invention to provide a coupling device with electro-magnetic compensation. With the use of a parallel-connected capacitor device, the present coupling device adjusts the amount of return loss and isolation capacity and makes the amount of coupling and output to reach to a level as anticipated. Furthermore, the present coupling device renders the consistency of signal transmitting speeds in two signal lines possible, achieving the goal of better high frequency characteristics. 
   In accordance with the claimed invention, a coupling device with electro-magnetic compensation includes a first substrate having a first signal line on a top surface of the first substrate, and a second substrate having a second signal line on a top surface of the second substrate connected together with a bottom surface of the first substrate wherein the second signal line is coupled with the first signal line by a plurality of electrical-conductive through holes, and one side of the first signal line lies a capacitor device parallel connected to a ground. The parallel-connected capacitor device could be either an open stub, a plurality of open stubs connected with others through wire bonding or ribbon bonding, or in the form of getting at least one capacitor connected to a grounded open stub. 
   It is an advantage of the present invention that with the setting of a parallel-connected capacitor device on one side or both sides of the signal line the present coupling device could have a superior isolation capacity and cut down the return loss while staying the coupling effect and amount of output at a level as expected and rendering the consistency of transmitting speeds in two signal lines possible in order to obtain a better high frequency characteristic. 
   These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic diagram of a coupling device according to the present invention. 
       FIG. 2  is a top view of a first preferred embodiment according to the present invention. 
       FIG. 3  is a top view of a second preferred embodiment according to the present invention. 
       FIG. 4  is a top view of a third preferred embodiment according to the present invention. 
       FIG. 5  is another schematic diagram of a coupling device according to the present invention. 
       FIG. 6  is a top view of a fourth preferred embodiment according to the present invention. 
       FIG. 7  is a top view of a fifth preferred embodiment according to the present invention. 
       FIG. 8  is a top view of a sixth preferred embodiment according to the present invention. 
       FIG. 9A  is a curve of the S-parameter of a coupling device according to the present invention. 
       FIG. 9B  is a curve of the S-parameter of a coupling device according to the prior art. 
       FIG. 10  is a schematic diagram of a coupling device according to the prior art. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Please refer to  FIG. 1  of a schematic diagram showing a coupling device  1  according to the present invention. The coupling device  1  includes a first substrate  11  having a first signal line  111  thereon, a second substrate  12  having a second signal  121  thereon, and a parallel-connected capacitor device  13 . The first signal line  111  is on the top surface of the first substrate  11  and the bottom surface of the first substrate  11  attaches to the top surface of the second substrate  12  where lies the second signal line  121 . The second signal line  121  couples with the first signal line  111  by a plurality of through holes  122  and the parallel-connected capacitor device  13  is placed beside the first signal line  111 . The bottom surface of the second substrate  12  further connects to a multi-layer substrate  14  where other layout could be placed. The parallel-connected capacitor device  13  could be either an open stub, in the form of a plurality of open stubs connected with others by wire bonding or ribbon bonding, or a grounded capacitor device. 
   The first signal line  111  has four ends including an input end  15 , a coupling end  16 , an output end  17 , and an isolation end  18 . The coupling device according to the present invention  1  could get the amount of coupling effect, return loss, and the isolation capacity by measuring aforementioned four ends of the first signal line  111 . The amount of the coupling effect, return loss, and isolation capacity depend on the length width of first and second signal lines  111  and  121 , the thickness of medium layer between those two signal lines  111  and  121  (i.e., the thickness of the first substrate  11 ), and the parallel-connected capacitor device  13  and the area thereof. 
   Please refer to  FIG. 2  of a structure schematic diagram of the first preferred embodiment according to the present invention. A coupling device  1   a  includes a first substrate  11   a  having a first signal line  111   a , a second substrate  12   a  (refer to  FIG. 1 ) connected to the first substrate  11   a  and having a second signal line  121   a  (refer to  FIG. 1  also), and a parallel-connected capacitor device  13   a  beside the first signal line  111   a . The current preferred embodiment employs an open stub  131   a  as the parallel-connected capacitor device  13   a  and the area of the open stub affects the amount of the coupling effect, return loss, and the isolation capacity of the coupling device  1   a . However, the use of an open stub as the parallel-connected capacitor device makes the change to the area of the open stub inconvenient where another new open stub must be replaced in order to make changes to the area of the open stub, leading to some inconvenience. 
   Please refer to  FIG. 3  of a top view of the second preferred embodiment according to the present invention. A coupling device  1   b  includes a first substrate  11   b  having a first signal line  111   b , a second substrate attached to the first substrate and having a second signal line (refer to  FIG. 1 ), and a parallel-connected capacitor device to the ground  13   b  beside the first signal line  111   b . In the current embodiment, the parallel-connected capacitor device to the ground  13   b  is in the form of a plurality of open stubs  131   b  interconnected with others through wire bonding or ribbon bonding, making the area of the parallel-connected capacitor device to the ground  13   b  adjustable without changing the entire open stub. 
   Please refer to  FIG. 4  of a top view of a third preferred embodiment according to the present invention. A coupling device  1   c  includes a first substrate  11   c  having a first signal line  111   c , a second substrate attached to the first substrate and having a second signal line (refer to  FIG. 1 ), and a parallel-connected capacitor device to the ground  13   c  beside the first signal line  111   c . The parallel-connected capacitor device to the ground  13   c  in the this preferred embodiment is in the form of having at least one capacitor  133   c  with one end attached to one side of the first signal line  111   c  and the other end connected to a grounded open stub  134   c . The grounded open stub  134   c  has at least one through hole  1341   c  for the purpose of grounding. The coupling device  1   c  adjusts the value of the capacitor  133   c  so as to control the amount of the coupling effect, return loss, and isolation capacity of the coupling device  1   c  itself. 
   Please refer to  FIG. 5  of another schematic diagram of a coupling device according to the present invention. A coupling device  2  includes a first substrate  21  having a first signal line  211 , a second substrate  22  having a second signal line  221 , a first parallel-connected capacitor device  23 , and a second parallel-connected capacitor device  24 . The bottom surface of the first substrate  21  connects to the top surface of the second substrate  22 . The second signal line  221  couples with the first signal line by a plurality of through holes  222 . The first parallel-connected capacitor device  23  and the second parallel-connected capacitor device  24  serving as the counterpart of the first parallel-connected capacitor device  23  in terms of the placement lie on each side of the first signal line  211 , respectively. The bottom surface of the second substrate  22  connects to a multi-layer substrate  25  where other circuitry layout is placed. The first and second parallel-connected capacitor devices  23  and  24  both could be open stubs, a plurality of open stubs interconnected with others by wire bonding or ribbon bonding, or in the form of having at least one capacitor connected to a grounded open stub. 
   Please refer to  FIG. 6  of a top view of a fourth preferred embodiment according to the present invention. A coupling device  2   a  includes a first substrate  21   a  having a first signal line  211   a , a second substrate having a second signal line (refer to  FIG. 5 ), a first parallel-connected capacitor device  23   a , and a second parallel-connected capacitor device  24   a  on each side of the first signal line  211   a . In the current embodiment, the first and second parallel-connected capacitor devices  23   a  and  24   a  are open stubs  231   a  and  241   a , respectively, in order to save more space than the embodiment shown in  FIG. 2 . In  FIG. 2 , in the case that the open stub  131   a  takes more space the space of the whole coupling device  1   a  increases as the result. The present embodiment divides the open stub  131   a  in  FIG. 2  into two pieces of open stubs  231   a  and  241   a  placed on each side of the first signal line  211   a , for the purpose of limiting the size of the entire coupling device  2   a.    
   Please refer to  FIG. 7  of a top view of a fifth preferred embodiment according to the present invention. A coupling device  2   b  includes a first substrate  21   b  having a first signal line  211   b , a second substrate connected to the first substrate  21   b  and having a second signal line (refer to  FIG. 5 ), and a first parallel-connected capacitor device  23   b  and a second parallel-connected capacitor device  24   b  placed on each side of the first signal line  211   b , respectively. The first and second parallel-connected capacitor devices  23   b  and  24   b  are a plurality of open stubs  231   b  and  241   b , respectively. Those open stubs  231   b  and  241   b  are interconnected with others through wire bonding or ribbon bonding. In doing so, at the time of adjusting the area of the first and second parallel-connected capacitor devices  23   b  and  24   b  only cutting down the number of those open stubs  231   b  and  241   b  is required, providing a viable alternative to the fourth preferred embodiment according to the present invention shown in  FIG. 5 . 
   Please refer to  FIG. 8  of a top view of a sixth preferred embodiment according to the present invention. A coupling device  2   c  includes a first substrate  21   c  having a first signal line  211   c , a second substrate connected to the first substrate  21   c  and having a second signal line (refer to  FIG. 5 ), and a first parallel-connected capacitor device  23   c  and a second parallel-connected capacitor device  24   c  placed on each side of the first signal line  211   b , respectively. The first and second parallel-connected capacitor devices  23   c  and  24   c  are single capacitors  233   c  and  243   c  connected to grounded open stubs  234   c  and  244   c . One end of each of capacitors  233   c  and  243   c  connects to the first signal line  211   c  while the other end of those capacitors  233   c  and  243   c  connects to grounded open stubs  234   c  and  244   c . Those grounded open stubs  233   c  and  244   c  each has at lest one through hole  2341   c  and  2441   c  connected to the ground. The present preferred embodiment controls the value of capacitors  233   c  and  243   c  for controlling the coupling effect, the return loss, and the isolation capacity thereof. 
   Please refer to  FIGS. 9A and 9B  of schematic diagrams showing S-parameter curves of coupling devices according to the present invention and prior art, respectively. Both coupling devices have in put end, a coupling end, an output end, and an isolation end. The coupling device according to the present invention has a first, second, third, and fourth curves  31 ,  32 ,  33 , and  34  while its counterpart based on the prior art is with fifth, sixth, seventh, and eighth curves  41 ,  42 ,  43 , and  44 . 
   The second and third curves are from the coupling and output ends of the coupling device according to the present invention. From those two curves, the amount of coupling effect and output is substantially equal at the frequency of 2 GHz while their counterparts (the sixth and seventh curves  42  and  43  from coupling and output ends of the coupling device of the prior art) are not close to each other at the same 2 GHz frequency, failing to meet the goal of having the amount of the coupling effect and output substantially equal. 
   The first and fifth curves show inputs of coupling devices according to the present invention and prior art. At the frequency of 2 GHz, the return loss for the coupling device according to the present invention is minus 32 db but is minus 15 db in the case of the coupling device based on the prior art. As the result, the present coupling device does improve the return loss. 
   The fourth and eighth curves  34  and  44  come from isolation ends of coupling devices according to the present invention and prior art, respectively. At the frequency of 2 GHz, the amount of isolation capacity is minus 31 db in the coupling device according to the present invention while the coupling device according to the prior art has the isolation capacity stay at minus 17.5 db. Above two curves show the difference in the isolation capacity between the coupling device according to the prior art and present invention, which effectively improve the performance of the isolation capacity. 
   In contrast to prior art coupling device, the coupling device according to the present invention incorporates a parallel-connected capacitor device to the ground for improving the return loss and isolation capacity and making the coupling effect and the amount of output reach to a level as expected. With the aforementioned characteristic, the present invention makes transmitting speeds in the first and second signal lines remain substantially the same so as to achieve better high frequency characteristics. 
   Those skilled in the art will readily observe that numerous modifications and alterations of the device may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.