Patent Publication Number: US-8542082-B2

Title: High-impedance line and detecting system having the same

Description:
CROSS-REFERENCE 
     This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 200910110162.X, filed on Oct. 30, 2009 in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a high-impedance line and a detecting system having the same. 
     2. Description of Related Art 
     Generally, a high-impedance line configured for shielding high frequency signals includes two high-impedance transmission lines parallel to each other. The high-impedance transmission lines are formed by spraying several high impedance materials such as ferrite and silicon repeatedly. Thus, a cost of the high-impedance line is increased. 
     What is needed therefore, is a high-impedance line with low cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is a schematic structural view of one embodiment of a detecting system. 
         FIG. 2  is a schematic structural view of one embodiment of a high-impedance line. 
         FIG. 3  is a schematic structural view of the high-impedance line, in which resistance units of the high-impedance line are not shown for clarity. 
         FIG. 4  is an exposed view of the high-impedance line shown in  FIG. 2 . 
         FIG. 5  is an equivalent circuit diagram of a distributed inductance connected to the high-impedance line. 
         FIG. 6  is an equivalent circuit diagram of a distributed capacitance connected to the high-impedance line. 
         FIG. 7  is an equivalent circuit diagram of the high-impedance line. 
     
    
    
     DETAILED DESCRIPTION 
     The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one. 
     Referring to  FIG. 1 , a detecting system  100  includes a high-impedance line  10 , a circuit board  20 , a signal detecting device  30  and a signal processing device  40 . The high-impedance line  10 , the signal detecting device  30 , and the signal processing device  40  are disposed on the circuit board  20 . One end of the high-impedance line  10  is electrically connected to the signal detecting device  30 , and the other opposite end of the high-impedance line  10  is electrically connected to the signal processing device  40 . 
     Referring to  FIG. 2 , the high-impedance line  10  includes a first transmission line  11  and a second transmission line  12  insulated from the first transmission line  11 . Both the first and second transmission lines  11  and  12  can be disposed on the circuit board  20 . The first transmission line  11  can intersect with the second transmission line  12  many times to form a plurality of windings  13 . In one embodiment, the high-impedance line  10  includes ten windings  13 . 
     Referring to  FIG. 3  and  FIG. 4 , the first transmission line  11  can include a plurality of first upper portions  111   a , a plurality of first lower portions  111   b , a plurality of first connective portions  112 , and a plurality of first resistance units  113 . The first upper portions  111   a  and the first lower portions  111   b  can be parallel to each other. The first upper portions  111   a  align with each other, and the first lower portions  111   b  align with each other. Two adjacent first upper portions  111   a  and first lower portion  111   b  can be electrically connected to each other by one first connective portion  112  or by one first resistance unit  113 . A distance between two adjacent and disconnected first lower portions  111   b  can be larger than a length of each of the first upper and lower portions  111   a  and  111   b . A distance between two adjacent and two disconnected first upper portions  111   a  can be larger than the length of each of the first upper and lower portions  111   a  and  111   b . One first resistance unit  113  can replace each of the first connective portions  112 . Alternatively, one first resistance unit  113  can be disposed on each of the first connective portions  112 . In one embodiment, as shown in  FIG. 2 , about half of the first resistance units  113  are electrically connected to adjacent first upper portion  111   a  and first lower portion  111   b , and about half of the first connective portions  112  are electrically connected to the adjacent first upper portions  111   a  and first lower portions  111   b . The first connective portions  112  and the first resistance units  113  can be electrically connected to the first transmission line  11  alternatively. In one embodiment, the first upper portions  111   a  and the first lower portions  111   b  are substantially parallel to each other. A distance between every two adjacent first upper portions  111   a  and first lower portions  111   b  can be substantially the same. 
     The first upper and lower portions  111   a  and  111   b  and the first connective portions  112  can include a conductive material such as metal, conductive polymers, metallic carbon nanotubes, and indium tin oxide (ITO). In one embodiment, the conductive material is a metallic material such as gold, silver, copper. The first upper and lower portions  111   a  and  111   b  and the first connective portions  112  can have a strip shape, rod shape, bar shape, wire shape, or yarn shape. For example, the first upper and lower portions  111   a  and  111   b  and the first connective portions  112  can be metal wires, or metal strips. The first upper and lower portions  111   a  and  111   b  and the first connective portions  112  can also be metal strip shaped films or layers printed on the circuit board  20 . The first upper and lower portions  111   a  and  111   b  and the first connective portions  112  can be formed by means of screen printing or spraying. A length of each of the first upper and lower portions  111   a  and  111   b  can be less than or equal to 10 millimeters. A diameter or a thickness of each of the first upper and lower portions  111   a  and  111   b  can be less than or equal to 0.2 millimeters. A resistance of each of the first resistance units  113  can be greater than or equal to 500 ohms. In one embodiment, the resistance of each of the first resistance units  113  is greater than or equal to 1000 ohms. 
     The second transmission line  12  can have the same structure, shape, material and size as the first transmission line  11 . The second transmission  12  can include a plurality of second upper and lower portions  121   a  and  121   b , a plurality of second connective portions  122 , and a plurality of second resistance units  123 . A second connective portion  122  or a second resistance unit  123  can electrically connect two adjacent second upper and lower portion  121   a  and  121   b  to each other. Referring to  FIG. 2  and  FIG. 3 , the first upper portions  111   a  and the second lower portions  121   b  can be parallel to and correspond to each other. The first lower portions  111   b  and the second upper portions  121   a  can be parallel to and correspond to each other. The second upper and lower portions  121   a  and  121   b  can have the same structure, shape, material, length, and diameter as the first upper and lower portions  111   a ,  111   b . The second connective portions  122  and the first connective portions  112  can be parallel to and correspond to each other. The second connective portions  122  can have the same structure, shape, material and size as the first connective portions  112 . The second resistance units  123  and the first resistance units  113  can correspond to each other. The second resistance units  123  can have the same structure, shape, material, size and resistance as the first resistance units  113 . The second connective portions  122  or the second resistance units  123  can intersect with the first connective portions  112  or the first resistance units  113  to form the windings  13  of the high-impedance line  10 . 
     Each of the windings  13  can include one first upper portion  111   a  and one second lower portion  121   b  parallel to the first upper portion  111   a , or include one first lower portion  111   b  and one second upper portion  121   a . A distance between the first upper portion  111   a  and the second lower portion  121   b  corresponding to the same winding  13  can be less than or equal to 2 millimeters. A distance between the first lower portion  111   b  and the second upper portion  121   a  corresponding to the same winding  13  can be less than or equal to 2 millimeters. In one embodiment, the distance between the first upper portion  111   a  and the second lower portion  121   b  is less than or equal to 0.2 millimeters, and the distance between the first lower portion  111   b  and the second upper portion  121   a  is less than or equal to 0.2 millimeters. The first resistance units  113  and the second resistance units  123  can be disposed between the windings  13 . A number of the first resistance units  113  can be equal to a number of the second resistance units  123 ; thus, a resistance of the first transmission line  11  can be equal to a resistance of the second transmission line  12 . In one embodiment, the first resistance units  113  and the second resistance units  123  are alternately disposed between windings  13 . A resistance of each of the windings  13  can be substantially equal to each other to ensure each of the windings  13  can have a determined resistance. 
     When the high-impedance line  10  is in operation and receives a radio frequency signal (RF signal), the high-impedance line  10  defines a distributed inductance and a distributed capacitance therein. The distributed inductance can be formed among the first upper and lower portions  111   a  and  111   b  and the second upper and lower portions  121   a  and  121   b . The distributed capacitance can be formed between the first upper portions  111   a , and the second lower portions  121   b , or formed between the first lower portions  111   b  and the second upper portions  121   a.    
     An equivalent circuit diagram of the distributed inductance, and the first upper and lower portions  111   a  and  111   b  and the second upper and lower portions  121   a ,  121   b  can be shown in  FIG. 5 . An inductance of the distributed inductance can be defined as L, and a frequency of the RF signal can be defined as ω, a reactance formed by the distributed inductance can be shown by the formula Z=jωt. Thus, the greater the frequency ω of the RF signals, the greater the reactance Z formed by the distributed inductance, and the greater the impedance of the high-impedance line  10 . 
     An equivalent circuit diagram of the distributed capacitance, and the first upper portions  111   a  and the second lower portions  121   b  can be shown in  FIG. 6 . An capacitance of the distributed inductance can be defined as C; a reactance Z formed by the distributed capacitance can be shown by the formula 
             Z   =       1     jω   ⁢           ⁢   C       .           
Thus, the greater the frequency ω of the RF signals, the less the reactance Z formed by the distributed capacitance, and the greater the impedance of the high-impedance line  10 .
 
     An equivalent circuit diagram of the high-impedance line  10  can be shown in  FIG. 7 . The impedance of the high-impedance line  10  formed by the distributed inductances, the distributed capacitances, the first resistance units  113 , and the second resistance units  123 , can be increased with the frequency ω of the RF signal. Thus, the high-impedance line  100  can be capable of shielding high frequency signals in RF signals. In one embodiment, the high-impedance line  100  is capable of shielding signals with a frequency substantially greater than 850 MHZ. 
     The circuit board  20  can be configured for fixing the high-impedance line  10 . The first upper and lower portions  111   a  and  111   b , the second upper and lower portions  121   a  and  121   b  and the first and second connective portions  121  and  122  can be fixed on the circuit board  20  by means of printing or welding. The first and second resistance units  113  and  123  can be fixed on the circuit board  20  by means of welding or adhering. The circuit board  20  can be a panel or a printed circuit board (PCB). In one embodiment, the circuit board  20  is the PCB. The PCB can provide electrical connection among the high-impedance line  100  and other electrical elements such as the signal detecting device  30 , and the signal processing device  40 . 
     The signal detecting device  30  can be configured for detecting RF signals and inputting the RF signals to the high-impedance line  10 . The high-impedance line  10  can converted the RF signals to signal envelops. The signal detecting device  30  can be a Hearing Aid Compatibility (HAC) probe or a detecting device detecting RF signals. 
     The signal processing device  40  can be configured for receiving signal envelopes converted by the high-impedance line  10 . The signal processing device  40  can be an Analog-digital converter (ADC), a central processing unit (CPU) or other data-processing equipment. 
     Finally, it is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. Elements associated with any of the above embodiments are envisioned to be associated with any other embodiments. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.