Patent Publication Number: US-2011050504-A1

Title: Multiple-connected microstrip lines and the design methods thereof

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the fields of transmission lines, waveguides, inductors, antennas and more specifically to a new transmission line structure, which comprises a plurality of microstrip lines connected together for improving electromagnetic characteristics such as impedance matching, inductor Quality (Q) factor, antenna radiation patterns, signal interference etc. 
     Microstrip line, shown as in  FIG. 1 , has been adopted as a basic structure for transmitting, feeding, storing, and radiating electromagnetic signals for years. One of main advantages is its simple structure, which is easy to manufacture and to integrate with other structures. However, this structure is susceptible to signal interference than other structures, such as striplines. Two widely referred papers related to microstrip lines are listed as follows:
     H. A. Wheeler, “Transmission-Line Properties of Parallel Strips Separated by a Dielectric Sheet,” IEEE Trans. on Microwave Theory &amp;. Techniques, Vol. 3, No. 3, March 1965, pp. 172-185.   H. A. Wheeler, “Transmission-Line of a Strip on a Dielectric Sheet on a Plane,” IEEE Trans. on Microwave Theory &amp; techniques, Vol. 25, No. 8, August 1977, pp. 631-647.   

     Recently, the electronic hardware becomes miniature. This trend is observed in all aspects of hardware technologies and materials, such as PCB, integrated circuits (IC), antennas, etc. The use of microstrip lines in conjunction with these technologies and materials suffers from two drawbacks. Firstly, due to miniaturization, the signals in microstrip lines become susceptible to the closer electromagnetic structures in the neighborhood; secondly, due to miniaturization, skin effect becomes more prominent, and subsequently the impedance of microstrip line varies sensitively with signal frequencies. In order to improve the frequency response and Q factor, particularly for broadband applications, there are inventions modifying the structures related to microstrip line. 
     For example, a prior art U.S. Pat. No. 6,750,750 teaches a multiple-parallel-line structure on the top of a conductive line of a spiral inductor as shown in  FIG. 2 . Another prior art U.S. Pat. No. 6,853,097 teaches a multiple-fins structure extend away from a based region of a conductive line of an inductor as shown in  FIG. 3 . And another prior art U.S. Pat. No. 6,885,275 teaches a multiple-tracks-conductive-line structure joined at ends on a single layer or joined through via holes for the structure on multiple layers as shown in  FIG. 4 . 
     However, these prior arts apply only to the on-chip inductors of integrated circuits and the teaching structures are not exactly the microstrip lines due to the involved architectures of integrated circuits. Therefore, these prior arts are applicable limited to the indicated area. 
     SUMMARY OF THE INVENTION 
     The primary object of the present invention is to provide a multiple-connected microstrip line, which comprises a plurality of microstrip lines connected by a plurality of conductive segments for forming a single electrically connected structure, thereby keeps the simple construction for easily integrating with other structures, meanwhile mitigates susceptibility of signal interference caused by miniaturization, improves the desirable electromagnetic characteristics, and increases the areas of applications. 
     A further object of the present invention is to provide design methods for designing multiple-connected-microstrip-line components, which transmit, feed-in/feed-out, store/release, and radiate/receive electromagnetic signals with improved Q factor, broadband impedance matching, interference immunity, and radiation patterns in the areas of transmission lines, impedance transformers, inductors, antennas etc. 
     Another further object of the present invention is to provide design methods for designing multiple-connected-microstrip-line components, which transmit, feed-in/feed-out, store/release, and radiate/receive electromagnetic signals with improved Q factor, broadband impedance matching, interference immunity and radiation patterns in the structures with single layer or a plurality of layers of metallic, semiconductor, and dielectric materials, such as those used for building integrated circuits (IC), thin film transistors (TFT), low temperature co-fired ceramics (LTCC), high temperature co-fired ceramics (HTCC), printed circuit board (PCB), carbon nanotube (CNT) etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a prior art—Microstrip line; 
         FIG. 2  is a prior art—Multiple-parallel-line on the top of a conductive line; 
         FIG. 3  is a prior art—Multiple-fin conductive line; 
         FIG. 4  is a prior art—Multiple-track conductive line; 
         FIG. 5  illustrates Multiple-connected microstrip line structure in this invention; 
         FIG. 6  is an embodiment of multiple-connected microstrip line as a transmission line; 
         FIG. 7  is another embodiment of multiple-connected microstrip line comprises feed-in, feed-out and via hole to ground conductor; 
         FIG. 8  is another embodiment of multiple-connected microstrip line comprises feed-in and feed-out; 
         FIG. 9  is an embodiment of transmission line designed by the prior art—Microstrip line; 
         FIG. 10  is an embodiment of transmission line designed by the structure of this invention, multiple-connected microstrip line; 
         FIG. 11  is the S parameters (S 11 , S 22 , and S 21 ) of transmission line designed by the prior art—Microstrip line ( FIG. 9 ); 
         FIG. 12  is the S parameters (S 11 , S 22 , and S 21 ) of transmission line designed by the structure of this invention, multiple-connected microstrip line ( FIG. 10 ); 
         FIG. 13  is an embodiment of antenna designed by the prior art—Microstrip line; 
         FIG. 14  is an embodiment of antenna designed by the structure of this invention, multiple-connected microstrip line; 
         FIG. 15  is the Total Field gain vs. Frequency plot of antenna designed by the prior art—Microstrip line ( FIG. 13 ); 
         FIG. 16  is the Total Field gain vs. Frequency plot of antenna designed by the structure of this invention, multiple-connected microstrip line ( FIG. 14 ); 
         FIG. 17  is the Elevation Radiation pattern plot of antenna designed by the prior art—Microstrip line ( FIG. 13 ); 
         FIG. 18  is the Elevation Radiation pattern plot of antenna designed by the structure of this invention, multiple-connected microstrip line ( FIG. 14 ). 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a known microstrip line comprises signal conductor  101 , dielectric material  102 , and ground conductor  103 . 
       FIG. 5  shows the structure of this invention, multiple-connected microstrip line comprising signal conductors  201 , dielectric material  202 , ground conductor  203 , conductive segments  204  for connecting signal conductors  201 ;  210  represents the width of signal conductor  101 ;  211  represents the height of signal conductor  101 ;  212  represents the height of dielectric material;  213  represents the length of dielectric material and ground conductor; and  214  represents the width of dielectric material and ground conductor. A multiple-connected microstrip line comprises two or more than two signal conductors.  215  represents the distance between two adjacent signal conductors. This distance  215  is also the width of conductive segments  204 . The length, height, and width of the individual signal conductors  201  are not necessarily the same. The length, height, and width of the individual conductive segments  204  are not necessarily the same either. A plurality of connecting positions among signal conductors and conductive segments forms a connecting pattern of a multiple-connected microstrip line. 
     Based on different connecting patterns and different dimensions of the signal conductors and conductive segments, the electromagnetic characteristics of multiple-connected microstrip line, such as resistance, capacitance, and inductance, will vary with the signal frequencies, consequently the S parameters, Q factor, radiation gain, and radiation pattern will reflect these variations. 
       FIG. 6  is an embodiment of transmission line designed by multiple-connected microstrip line. This embodiment comprises three signal conductors with a wide signal conductor  305  at center and two narrow signal conductors  301  on both sides. These signal conductors are connected by conductive segments  304 . The narrower signal conductors with higher impedance shield the undesirable signal interference from external environment when the major part of electromagnetic energy transmits through the central signal conductor. 
     For an unbalanced feed-in, we can connect the signal conductor of a coaxial cable to the signal conductor  101  of a traditional microstrip line and ground shield of the coaxial cable to the ground conductor  103  ( FIG. 1 ).  FIG. 7  shows an embodiment of two signal feed-in points  410  to two signal conductors  401 , which extending to the other side of multiple-connected microstrip line, and therein connected to a third signal conductor  401  by conductive segments  404 . A signal feed-out  411  connected to the third signal conductor passes the signal to a coaxial cable by the same manner as feed-in. The construction of feed-in and feed-out is not limited to the current form. Signal conductor  401  can be also connected to a conductive or semi-conductive via hole  412  to the ground conductor  403  by the conductive segment  404  through dielectric material  402 .  FIG. 8  is an another embodiment showing different designs of feed-in  510 , signal conductors  501 , conductive segments  504 , and feed-out  511 . In this  FIG. 502  represents the dielectric material and  503  represents ground conductor.  FIG. 7  and  FIG. 8  show that a multiple-connected microstrip line can be constructed on a signal layer or a plurality of layers by different connecting configurations of feed-in, feed-out, and via hole. 
       FIG. 9  is a microstrip line designed as a transmission line with signal conductor  101 , dielectric material  102 , ground conductor  103 , feed-in  110 , and feed-out  111 .  FIG. 10  shows a multiple-connected microstrip line designed as a transmission line with three signal conductors  701 , conductive segments  704 , feed-in  710 , feed-out  711 , dielectric material  702 , and ground conductor  703 . The total width including three signal conductors and two conductive segments of the multiple-connected microstrip line is same as the width of microstrip line in  FIG. 9 .  FIG. 11  shows the S parameters (S 11 , S 22 , and S 21 ) from 0.2 GHz to 2 GHz of transmission line designed by the traditional microstrip line ( FIG. 9 ); and  FIG. 12  shows S 11 , S 22 , and S 21  of transmission line in the same frequency range designed by multiple-connected microstrip lines ( FIG. 10 ). From these plots, we observe that the additional topological parameters of multiple-connected microstrip line, such as the widths and the separating distances of signal conductors, allow the designers to improve the frequency response and Q factor of transmission line over a broad bandwidth. 
       FIG. 13  is a microstrip line designed as an antenna with signal conductor  101 , dielectric material  102 , ground conductor  103 , and feed-in  410 . The ground conductor only partially covers the dielectric material  102 .  FIG. 14  shows a multiple-connected microstrip line designed as an antenna with two signal conductors  1101 , dielectric material  1102 , ground conductor  1103 , and feed-in  1110 . All dimensions of this design are same as those in  FIG. 13  except the signal conductors  1101 . The total width including two signal conductors and the gap between two signal conductors of the multiple-connected microstrip line is same as the width of microstrip line  101  in  FIG. 13 .  FIG. 15  shows the Total Field gain vs. Frequency plot of antenna designed by traditional microstrip line ( FIG. 13 ). And  FIG. 16  shows the Total Field gain vs. Frequency plot of antenna designed by multiple-connected microstrip lines ( FIG. 14 ).  FIG. 17  shows the Elevation Radiation pattern plot of antenna designed by microstrip line ( FIG. 13 ); and  FIG. 18  shows the Elevation Radiation pattern plot of antenna designed by the multiple-connected microstrip lines ( FIG. 14 ). Again, from these plots, we observe that the additional topological parameters of multiple-connected microstrip line allow the designers to improve gain and radiation pattern of broadband antennas. 
     From the embodiments disclosed above,  FIG. 10  shows that the multiple-connected microstrip line comprises three signal conductors as part of a transmission line, and  FIG. 14  shows that the multiple-connected microstrip line comprises two signal conductors as part of an antenna. These embodiments represent two connecting patterns of the multiple-connected microstrip line. 
     Although the present invention has been described in the detailed embodiments, a myriad of changes, variations, alterations, transformations and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alternations, transformations and modifications that fall within the spirit and scope of the appended claims.