Patent Publication Number: US-2022216578-A1

Title: Filter device and equivalent filter circuit thereof

Description:
This non-provisional application claims priority claim under 35 U.S.C. § 119(a) on Taiwan Patent Application No. 110100676 filed Jan. 7, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention is related to a filter device and an equivalent filter circuit, particularly to a filter device and an equivalent filter circuit used for absorbing the electromagnetic noise. 
     BACKGROUND 
     In current electronic products, the requirements for data transmission rates are rising rapidly, such that the transmitting speed of signal of high-speed transmission interfaces (such as USB, HDMI, and Thunderbolt) are also faster and faster. However, when the signal passes through a discontinuous structure, for example, holes passed through multi-layered, blended signal trajectory, and the interface connector, it will easily generate noises, and therefore cause serious electromagnetic interference (EMI) or radio frequency interference (RFI). When the EMI or RFI occurs, the operation of the electrical elements within the electrical product will be affected. 
     The conventional filter is usually a reflective filter. The reflective filter can reflect the noise back to an original path (such as front circuit) to prevent the noise to interfere the circuit to be protected. However, the reflected common-mode signal may also be transmitted to other radiating elements, in which the problem of electromagnetic interference still exists in the communication system. 
     SUMMARY 
     It is one objective of the present invention to provide an equivalent filter circuit, in which comprises at least one first equivalent transmission line model, at least one second equivalent transmission line model, and/or at least one third equivalent transmission line model. One or more impedance units are disposed between the first equivalent transmission line model, the second equivalent transmission line model, and/or the third equivalent transmission line model, and connected with the first equivalent transmission line model, the second equivalent transmission line model, and/or the third equivalent transmission line model in series, parallel or series-parallel. Thereby, the equivalent filter circuit can absorb at least one noise at at least one specific frequency by the impedance units. 
     It is other objective of the present invention to provide a filter device, in which includes a substrate, at least one transmission conductor, and a first reference conductor. The transmission conductor is configured on a first surface of the substrate, and the first reference conductor is configured on a second surface of the substrate. The first reference conductor comprises a slotted structure. The slotted structure comprises a frame portion, a slotted portion, and a hollow portion. The slotted portion surrounds the frame portion, and the hollow portion is form in the frame portion. One or more impedance units are disposed on the frame portion and/or the slotted portion so that the filter device can absorb at least one noise at at least one specific frequency by the impedance units. 
     It is another objective of the present invention to provide a filter device, in which a second reference conductor, based on the position of the transmission conductor, is disposed in the hollow portion of the slotted structure of the filter device. A capacitive coupling effect generated between the transmission conductor and the slotted structure can be increased by the configuration of the second reference conductor, so that the signal passing through the filter device can obtain a better impedance matching to achieve better signal quality. 
     For achieving the above objectives, the present invention provides an equivalent filter circuit, comprising: at least one first equivalent transmission line model, comprising: a first master transmission conductor, connected at left end thereof to a signal input port, and connected at right end thereof to a signal output port; and a first slave transmission conductor; at least one second equivalent transmission line model, comprising: a second master transmission conductor connected at left and right ends thereof to a reference potential; and a second slave transmission conductor connected at right end thereof to right end of the first slave transmission conductor; and at least one first impedance unit connected between left end of the first slave transmission conductor and left end of the second slave transmission conductor in series. 
     In one embodiment of the present invention, wherein at least one second impedance unit is connected between right end of the first slave transmission conductor and right end of the second slave transmission conductor in series. 
     In one embodiment of the present invention, wherein the equivalent filter circuit comprises at least one third equivalent transmission line model, the least one third equivalent transmission line model comprises a third master transmission conductor and a third slave transmission conductor, left end of the second master transmission conductor is connected to the reference potential via the third master transmission conductor, the third slave transmission conductor and the at least one first impedance unit are connected between left end of the first slave transmission conductor and left end of the second slave transmission conductor in series. 
     In one embodiment of the present invention, wherein at least one third impedance unit is connected between left end of the first slave transmission conductor and left end of the third slave transmission conductor in series. 
     In one embodiment of the present invention, wherein at least one second impedance unit is connected between right end of the first slave transmission conductor and right end of the second slave transmission conductor in series. 
     In one embodiment of the present invention, wherein at least one fourth impedance unit is connected between right end of the first impedance unit and left end of the second master transmission conductor, or the at least one fourth impedance unit is connected between left end of the first impedance unit and left end of the second master transmission conductor. 
     In one embodiment of the present invention, wherein at least one second impedance unit is connected between right end of the first slave transmission conductor and right end of the second slave transmission conductor in series, at least one fifth impedance unit is connected between right end of the at least one second impedance unit and the reference potential, or the at least one fifth impedance unit is connected between left end of the at least one second impedance unit and the reference potential. 
     In one embodiment of the present invention, wherein the equivalent filter circuit comprises at least one third equivalent transmission line model; the least one third equivalent transmission line model comprises a third master transmission conductor and a third slave transmission conductor; left end of the second master transmission conductor is connected to the reference potential via the third master transmission conductor; at least one third impedance unit, the third slave transmission conductor, and the at least one first impedance unit are connected between left end of the first slave transmission conductor and left end of the second slave transmission conductor in series; at least one sixth impedance unit is connected between right end of the third impedance unit and the reference potential, or the at least one sixth impedance unit is connected between left end of the third impedance unit and the reference potential. 
     In one embodiment of the present invention, further comprising one or more fourth impedance units and comprising a plurality of the first impedance units; wherein each of the fourth impedance units is connected at one end thereof between the two adjacent first impedance units, and connected at other end thereof to the second master transmission conductor. 
     In one embodiment of the present invention, wherein a plurality of second impedance units are connected between right end of the first slave transmission conductor and right end of the second slave transmission conductor in series; the equivalent filter circuit further comprises one or more fifth impedance unit, each of the fifth impedance units is connected at one end thereof between the two adjacent second impedance units, and connected at other end thereof to the reference potential. 
     In one embodiment of the present invention, wherein the equivalent filter circuit comprises at least one third equivalent transmission line model; the least one third equivalent transmission line model comprises a third master transmission conductor and a third slave transmission conductor; left end of the second master transmission conductor is connected to the reference potential via the third master transmission conductor; a plurality of third impedance units, the third slave transmission conductor, and the at least one first impedance unit are connected between left end of the first slave transmission conductor and left end of the second slave transmission conductor in series; the equivalent filter circuit further comprises one or more sixth impedance units, each of the sixth impedance units is connected at one end thereof between the two adjacent third impedance units, and connected at other end thereof to the reference potential. 
     In one embodiment of the present invention, wherein a plurality of second impedance units are connected between right end of the first slave transmission conductor and right end of the second slave transmission conductor in series; the equivalent filter circuit further comprises one or more fifth impedance unit, each of the fifth impedance units is connected at one end thereof between the two adjacent second impedance units, and connected at other end thereof to the reference potential. 
     In one embodiment of the present invention, wherein the first master transmission conductor and the first slave transmission conductor are coupled to generate a first characteristic impedance and a first electrical length; the second master transmission conductor and the second slave transmission conductor are coupled to generate a second characteristic impedance and a second electrical length; the third master transmission conductor and the third slave transmission conductor are coupled to generate a third characteristic impedance and a third electrical length; the first characteristic impedance, the second characteristic impedance, and the third characteristic impedance are of the same impedance value or the different impedance values; the first electrical length, the second electrical length, and the third electrical length are of the same electrical length or the different electrical lengths. 
     In one embodiment of the present invention, wherein the equivalent filter circuit comprises the two first equivalent transmission line models and the two second equivalent transmission line models; left ends of the second slave transmission conductors of the two first equivalent transmission line models are connected together via the at least one corresponding first impedance unit, and right ends of the second slave transmission conductors of the two first equivalent transmission line models are directly connected together. 
     In one embodiment of the present invention, wherein the first equivalent transmission line model or the second equivalent transmission line model is a microstrip line, a slotted line, an artificial transmission line, a modified-T circuit line, or other transmission line structure capable of transmitting signals. 
     In one embodiment of the present invention, wherein the at least one first impedance unit is at least one resistor, at least one inductor, at least one capacitor, or a series-parallel combination of the at least one resistor, the at least one inductor, and the at least one capacitor. 
     The present invention further comprises an equivalent filter circuit, comprising: at least one first equivalent transmission line model, comprising: a first master transmission conductor, connected at left end thereof to a signal input port, and connected at right end thereof to a signal output port; and a first slave transmission conductor; and at least one second equivalent transmission line model, comprising: a second master transmission conductor connected at left and right ends thereof to a reference potential; and a second slave transmission conductor, connected at left end thereof to left end of the first slave transmission conductor, and connected at right end thereof to right end of the first slave transmission conductor; wherein the at least one second equivalent transmission line model is connected to a first impedance unit in parallel via left end of the second master transmission conductor and left end of the second slave transmission conductor. 
     In one embodiment of the present invention, wherein the at least one second equivalent transmission line model is connected to a second impedance unit in parallel via right end of the second master transmission conductor and right end of the second slave transmission conductor. 
     In one embodiment of the present invention, wherein the equivalent filter circuit comprises at least one third equivalent transmission line model, the least one third equivalent transmission line model comprises a third master transmission conductor and a third slave transmission conductor; left end of the second master transmission conductor is connected to the reference potential via the third master transmission conductor; the third slave transmission conductor are connected between left end of the first slave transmission conductor and left end of the second slave transmission conductor in series. 
     In one embodiment of the present invention, wherein the at least one third equivalent transmission line model is connected to the first impedance unit in parallel via right end of the third master transmission conductor and right end of the third slave transmission conductor, and the at least one third equivalent transmission line model is connected to a third impedance unit in parallel via left end of the third master transmission conductor and left end of the third slave transmission conductor. 
     In one embodiment of the present invention, wherein the at least one second equivalent transmission line model is connected to a second impedance unit in parallel via right end of the second master transmission conductor and right end of the second slave transmission conductor. 
     The present invention further comprises a filter device, comprising: a substrate; at least one transmission conductor configured on a first surface of the substrate; and a first reference conductor, configured on a second surface of the substrate, and comprising a slotted structure, the slotted structure comprising: a frame portion; a slotted portion surrounding the frame portion; and a hollow portion formed in the frame portion; wherein at least one first impedance unit is connected to the frame portion. 
     In one embodiment of the present invention, wherein the frame portion is a quadrilateral frame and comprises a first side, a second side, a third side, and a fourth side; the first side is corresponding to the third side, and the second side is corresponding to the fourth side, the at least one transmission conductor is projectively across the first side and the third side of the frame portion. 
     In one embodiment of the present invention, further comprising at least one second impedance unit, wherein the at least one first impedance unit is disposed on the first side of the frame portion based on the position of the at least one transmission conductor, and the at least one second impedance unit is disposed on the third side of the frame portion based on the position of the at least one transmission conductor. 
     In one embodiment of the present invention, further comprising at least one third impedance unit, wherein the at least one third impedance unit is configured on the second side or the fourth side of the frame portion. 
     In one embodiment of the present invention, further comprising at least one third impedance unit, wherein the at least one third impedance unit is disposed on the second side or the fourth side of the frame portion. 
     In one embodiment of the present invention, further comprising at least one fourth impedance unit, wherein the at least one fourth impedance unit is disposed in the slotted portion, the at least one first impedance unit is connected at left end or right end thereof to the first reference conductor via the at least one fourth impedance unit. 
     In one embodiment of the present invention, further comprising at least one fourth impedance unit and at least one fifth impedance unit, wherein the at least one fourth impedance unit and the at least one fifth impedance unit are disposed in the slotted portion, the first impedance unit is connected at left end or right end thereof to the first reference conductor via the at least one fourth impedance unit, and the second impedance unit is connected at left end or right end thereof to the first reference conductor via the at least one fifth impedance unit. 
     In one embodiment of the present invention, further comprising at least one fourth impedance unit and at least one sixth impedance unit, wherein the at least one fourth impedance unit and the at least one sixth impedance unit are disposed in the slotted portion, the first impedance unit is connected at left end or right end thereof to the first reference conductor via the at least one fourth impedance unit, and the third impedance unit is connected at left end or right end thereof to the first reference conductor via the at least one sixth impedance unit. 
     In one embodiment of the present invention, further comprising at least one fourth impedance unit, at least one fifth impedance unit, and at least one sixth impedance unit; wherein the at least one fourth impedance unit, the at least one fifth impedance unit, and the at least one sixth impedance unit are disposed in the slotted portion; the first impedance unit is connected at left end or right end thereof to the first reference conductor via the at least one fourth impedance unit, the second impedance unit is connected at left end or right end thereof to the first reference conductor via the at least one fifth impedance unit, and the third impedance unit is connected at left end or right end thereof to the first reference conductor via the at least one sixth impedance unit. 
     In one embodiment of the present invention, further comprising one or more fourth impedance units disposed in the slotted portion, wherein each of the fourth impedance units is connected at one end thereof between the two adjacent first impedance units, and connected at other end thereof to the first reference conductor. 
     In one embodiment of the present invention, further comprising one or more fourth impedance units and one or more fifth impedance units; wherein the one or more fourth impedance units and the one or more fifth impedance units are disposed in the slotted portion; each of the fourth impedance units is connected at one end thereof between the two adjacent first impedance units, and connected at other end thereof to the first reference conductor, and each of the fifth impedance units is connected at one end thereof between the two adjacent second impedance units, and connected at other end thereof to the first reference conductor. 
     In one embodiment of the present invention, further comprising one or more fourth impedance units and one or more sixth impedance units; wherein the one or more fourth impedance units and the one or more sixth impedance units are disposed in the slotted portion; each of the fourth impedance units is connected at one end thereof between the two adjacent first impedance units, and connected at other end thereof to the first reference conductor, and each of the sixth impedance units is connected at one end thereof between the two adjacent third impedance units, and connected at other end thereof to the first reference conductor. 
     In one embodiment of the present invention, further comprising one or more fourth impedance units, one or more fifth impedance units, and one or more sixth impedance units; wherein the one or more fourth impedance units, the one or more fifth impedance units, and the one or more sixth impedance units are disposed in the slotted portion; each of the fourth impedance units is connected at one end thereof between the two adjacent first impedance units, and connected at other end thereof to the first reference conductor, each of the fifth impedance units is connected at one end thereof between the two adjacent second impedance units, and connected at other end thereof to the first reference conductor, and each of the sixth impedance units is connected at one end thereof between the two adjacent third impedance units, and connected at other end thereof to the first reference conductor. 
     In one embodiment of the present invention, wherein the slotted structure further comprises a second reference conductor, wherein the second reference conductor is configured in the hollow portion based on the position of the at least one transmission conductor. 
     In one embodiment of the present invention, wherein the number of the transmission conductors is two to form a pair of differential transmission conductors. 
     In one embodiment of the present invention, wherein the frame portion and the first reference conductor are formed as an asymmetric coplanar strip line. 
     The present invention further comprises a filter device, comprising: a substrate; at least one transmission conductor configured on a first surface of the substrate; and a first reference conductor, configured on a second surface of the substrate, and comprising a slotted structure, the slotted structure comprising: a frame portion; a slotted portion surrounding the frame portion; and a hollow portion formed in the frame portion; wherein at least one first impedance unit is disposed in the slotted portion, and connected to the frame portion and the first reference conductor. 
     In one embodiment of the present invention, further at least one second impedance unit, wherein the at least one first impedance unit is disposed in the slotted portion based on the position of the at least one transmission conductor, and connected to the first side of the frame portion and the first reference conductor; the at least one second impedance unit is disposed in the slotted portion based on the position of the at least one transmission conductor, and connected to the third side of the frame portion and the first reference conductor. 
     In one embodiment of the present invention, further at least one third impedance unit, wherein the at least one third impedance unit is disposed in the slotted portion, and connected to the second side of the frame portion and the first reference conductor or connected to the fourth side of the frame portion and the first reference conductor. 
     In one embodiment of the present invention, further at least one third impedance unit, wherein the at least one first impedance unit is disposed in the slotted portion based on the position of the at least one transmission conductor, and connected to the first side of the frame portion and the first reference conductor; the at least one third impedance unit is disposed in the slotted portion, and connected to the second side of the frame portion and the first reference conductor or connected to the fourth side of the frame portion and the first reference conductor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit diagram of an equivalent filter circuit according to one embodiment of the present invention. 
         FIG. 2  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 3  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 4  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 5  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 6  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 7  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 8  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 9  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 10  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 11  is a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. 
         FIG. 12  is a three-dimensional structural perspective view of a filter device according to one embodiment of the present invention. 
         FIG. 13  is a structural top view of a filter device according to one embodiment of the present invention. 
         FIG. 14  is a structural bottom view of a filter device according to one embodiment of the present invention. 
         FIG. 14A  is a structural section view of a filter device according to one embodiment of the present invention. 
         FIG. 14B  is a structural section view of a filter device according to another embodiment of the present invention. 
         FIG. 15  is an enlarged view of area A in  FIG. 14 . 
         FIG. 16  is a structural bottom view of a filter device according to another embodiment of the present invention. 
         FIG. 17  is a structural bottom view of a filter device according to another embodiment of the present invention. 
         FIG. 18  is a structural bottom view of a filter device according to another embodiment of the present invention. 
         FIG. 19  is a structural bottom view of a filter device according to another embodiment of the present invention. 
         FIG. 20  is a structural bottom view of a filter device according to another embodiment of the present invention. 
         FIG. 21  is a three-dimensional structural perspective view of a filter device according to another embodiment of the present invention. 
         FIG. 22  is a structural top view of a filter device according to another embodiment of the present invention. 
         FIG. 23  is a structural bottom view of a filter device according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , there is shown a circuit diagram of an equivalent filter circuit according to one embodiment of the present invention. As shown in  FIG. 1 , the equivalent filter circuit  200  is used to suppress at least one electromagnetic noise at at least one specific frequency, and it is a single-ended equivalent filter circuit. The equivalent filter circuit  200  comprises at least one first equivalent transmission line model  21  and at least one equivalent transmission line model  22 . The first equivalent transmission line model  21  comprises a first master transmission conductor  211  and a first slave transmission conductor  212 . The second equivalent transmission line model  22  comprises a second master transmission conductor  221  and a second slave transmission conductor  222 . 
     The first master transmission conductor  211  is connected at left end thereof to a signal input port  2111 , and connected at right end thereof to a signal output port  2112 . The second master transmission conductor  221  is connected at left and right ends thereof to a reference potential (V). The first slave transmission conductor  212  is connected at left end thereof to left end of the second slave transmission conductor  222 , and connected at right end thereof to right end of the second slave transmission conductor  222 . 
     The equivalent filter circuit  200  of the present invention is an absorption equivalent filter circuit, which is provided with at least one impedance unit therein to absorb the at least one noise at the at least one specific frequency by the impedance unit. In the present embodiment, at least one first impedance unit  31  is connected between left end of the first slave transmission conductor  212  and left end of the second slave transmission conductor  222  in series, or at least one second impedance unit  32  is connected between right end of the first slave transmission conductor  212  and right end of the second slave transmission conductor  222  in series. 
     Further, the two single-ended equivalent filter circuits  200  can be combined into a differential equivalent filter circuit. As shown in  FIG. 2 , the differential equivalent filter circuit comprises the two first equivalent transmission line models  21  and the two second equivalent transmission line models  22 . The left ends of the second slave transmission conductors  222  of the two equivalent transmission line models  22  are connected together via the first impedance units  31 , and the right ends of the second slave transmission conductors  222  of the two equivalent transmission line models  22  are directly connected together or connected together via the second impedance units  32 . 
     Referring to  FIG. 3 , there is shown a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. As shown in  FIG. 3 , the equivalent filter circuit  201  of the present embodiment further comprises at least one third equivalent transmission line model  23 . The third equivalent transmission line model  23  comprises a third master transmission conductor  231  and a third slave transmission conductor  232 . The second master transmission conductor  221  is connected at left end thereof to the reference potential via the third master transmission conductor  231 , and the third slave transmission conductor  232  and the first impedance unit  31  are connected between the left end of the first slave transmission conductor  212  and the left end of the second slave transmission conductor  222  in series. 
     Referring to  FIG. 4 , there is shown a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. Comparing to the equivalent filter circuit  201  in the embodiment of  FIG. 3 , the equivalent filter circuit  202  in the embodiment of  FIG. 4  further comprises at least one second impedance unit  32  and at least one third impedance unit  33 . The second impedance unit  32  is connected between right end of the first slave transmission conductor  212  and right end of the second slave transmission conductor  222  in series, and the third impedance unit  33  is connected between left end of the first slave transmission conductor  212  and left end of the third slave transmission conductor  232  in series. 
     Further, the two single-ended equivalent filter circuits  201 / 202  can be combined into a differential equivalent filter circuit. As shown in  FIG. 5 , the differential equivalent filter circuit comprises the two first equivalent transmission line models  21 , the two second equivalent transmission line models  22 , and the two third equivalent transmission line models  23 . In one embodiment of the present invention, the left ends of the third slave transmission conductors  232  of the two third equivalent transmission line models  23  are directly connected together or connected together via the third impedance units  33 , and the right ends of the second slave transmission conductors  222  of the two equivalent transmission line models  22  are directly connected together or connected together via the second impedance units  32 . 
     Referring to  FIG. 6 , there is shown a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. Comparing to the equivalent filter circuit  201  in the embodiment of  FIG. 3 , the equivalent filter circuit  203  in the embodiment of  FIG. 6  further comprises at least one fourth impedance unit  34 . The fourth impedance unit  34  is connected between right end of the first impedance unit  31  and left end of the second master transmission conductor  221 ; or the fourth impedance unit  34  is connected between left end of the first impedance unit  31  and left end of the second master transmission conductor  221 . 
     Referring to  FIG. 7 , there is shown a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. Comparing to the equivalent filter circuit  203  in the embodiment of  FIG. 6 , the equivalent filter circuit  204  in the embodiment of  FIG. 7  further comprises at least one second impedance unit  32 , at least one third impedance unit  33 , at least one fifth impedance unit  35 , and at least one sixth impedance unit  36 . 
     The second impedance unit  32  is connected between right end of the first slave transmission conductor  212  and right end of the second slave transmission conductor  222  in series. The third impedance unit  33  is connected between left end of the first slave transmission conductor  212  and left end of the third slave transmission conductor  232  in series. The fifth impedance unit  35  is connected between right end of the second impedance unit  32  and the reference potential, or the fifth impedance unit  35  is connected between left end of the second impedance unit  32  and the reference potential. The sixth impedance unit  36  is connected between right end of the third impedance unit  33  and the reference potential, or the sixth impedance unit  36  is connected between left end of the third impedance unit  33  and the reference potential. In the present embodiment, these fourth impedance units  34  located at the left and right ends of the first impedance units  31  may have the same impedance value or the different impedance values; these fifth impedance units  35  located at the left and right ends of the second impedance units  32  may have the same impedance value or the different impedance values; these sixth impedance units  36  located at the left and right ends of the third impedance units  33  may have the same impedance value or the different impedance values. 
     Referring to  FIG. 8 , there is shown a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. In the equivalent filter circuit  205  in the embodiment of  FIG. 8 , two or more than two first impedance units  31  are connected between the second slave transmission conductor  222  and the third slave transmission conductor  232  in series. Besides, the equivalent filter circuit  205  comprises one or more fourth impedance units  34 . Each of the fourth impedance units  34  is connected at one end thereof between the two adjacent first impedance units  31 , and connected at other end thereof to the second master transmission conductor  221 . 
     Referring to  FIG. 9 , there is shown a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. Comparing to the equivalent filter circuit  205  in the embodiment of  FIG. 8 , the equivalent filter circuit  206  in the embodiment of  FIG. 9  further comprises two or more than two second impedance units  32 , two or more than two third impedance units  33 , at least one fifth impedance units  35 , and at least one sixth impedance units  36 . 
     The second impedance units  32  are connected between right end of the first slave transmission conductor  212  and right end of the second slave transmission conductor  222  in series, and the third impedance units  33  are connected between left end of the first slave transmission conductor  212  and left end of the third slave transmission conductor  232  in series. Each of the fifth impedance units  35  is connected at one end thereof between the two adjacent second impedance units  32 , and connected at other end thereof to the reference potential. Each of the sixth impedance units  36  is connected at one end thereof between the two adjacent third impedance units  33 , and connected at other end thereof to the reference potential. In the present embodiment, these first impedance units  31  located at the left and right ends of the fourth impedance unit  34  may have the same impedance value or the different impedance values; these second impedance units  32  located at the left and right ends of the fifth impedance unit  35  may have the same impedance value or the different impedance values; these third impedance units  33  located at the left and right ends of the sixth impedance unit  36  may have the same impedance value or the different impedance values. 
     Referring to  FIG. 10 , there is shown a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. Comparing to the equivalent filter circuit  200  in the embodiment of  FIG. 1  where the impedance units are provided in series, the equivalent filter circuit  207  of this embodiment is provided with at least one impedance unit in parallel. For example, the second equivalent transmission line model  22  is connected to at least one first impedance unit  31  in parallel via left end of the second master transmission conductor  221  and left end of the second slave transmission conductor  222 ; or, the second equivalent transmission line model  22  is connected to at least one second impedance unit  32  in parallel via right end of the second master transmission conductor  221  and right end of the second slave transmission conductor  222 . 
     Referring to  FIG. 11 , there is shown a circuit diagram of an equivalent filter circuit according to another embodiment of the present invention. Comparing to the equivalent filter circuit  207  in the embodiment of  FIG. 10 , the equivalent filter circuit  208  in the embodiment of  FIG. 11  further comprises at least one third equivalent transmission line model  23 . The third equivalent transmission line model  23  is connected to at least one first impedance unit  31  in parallel via right end of the third master transmission conductor  231  and right end of the third slave transmission conductor  232 , and connected to at least one third impedance unit  33  in parallel via left end of the third master transmission conductor  231  and left end of the third slave transmission conductor  232 . 
     In each of the above embodiments, the first master transmission conductor  211  and the first slave transmission conductor  212  of the first equivalent transmission line model  21  are coupled to generate a first characteristic impedance (Z 1 ) and a first electrical length (θ 1 ), the second master transmission conductor  221  and the second slave transmission conductor  222  of the second equivalent transmission line model  22  are coupled to generate a second characteristic impedance (Z 2 ) and a second electrical length (θ 2 ), and the third master transmission conductor  231  and the third slave transmission conductor  232  of the second equivalent transmission line model  23  are coupled to generate a third characteristic impedance (Z 3 ) and a third electrical length (θ 3 ). The first characteristic impedance (Z 1 ), the second characteristic impedance (Z 2 ), and the third characteristic impedance (Z 3 ) are of the same impedance value or the different impedance values. The first electrical length (θ 1 ), the second electrical length (θ 2 ), and the third electrical length (θ 3 ) are of the same electrical length or the different electrical lengths. In one embodiment of the present invention, the second electrical length (θ 2 ) or the third electrical length (θ 3 ) is designed close to zero. 
     The first equivalent transmission line model  21 , the second equivalent transmission line model  22 , or the second equivalent transmission line model  23  are a microstrip line, a slotted line, an artificial transmission line, a modified-T circuit line, or other transmission line structure capable of transmitting signals. 
     The equivalent filter circuit  200 / 201 / 202 / 203 / 204 / 205 / 206 / 207 / 208  of the present invention is provided with one or more impedance units  31 ,  32 ,  33 ,  34 ,  35 , or  36  in series, parallel, or series-parallel. The impedance unit  31 ,  32 ,  33 ,  34 ,  35 , or  36  is at least one resistor, at least one inductor, at least one inductor, or a series-parallel combination of the resistor, the inductor, and the capacitor. In one embodiment of the present invention, the impedance units  31 ,  32 ,  33 ,  34 ,  35 , and  36  can be designed to have the same impedance value or the different impedance values. In other embodiment of the present invention, the impedance values of the one or more impedance units  31 ,  32 ,  33 ,  34 ,  35 , and  36  can be designed to be zero. 
     Referring to  FIG. 12 ,  FIG. 13 , and  FIG. 14 , there are shown a three-dimensional structural perspective view, a structural top view, and a structural bottom view of a filter device according to one embodiment of the present invention, and also referring to  FIG. 1 . As shown in  FIG. 12 ,  FIG. 13 , and  FIG. 14 , the filter device  500  comprises a substrate  51 , at least one transmission conductor  53 , and a first reference conductor  55 . The transmission conductor  53  is configured on a first surface (such as top surface) of the substrate  51 , and the first reference conductor  55  is configured on a second surface (such as bottom surface) of the substrate  51 . The first reference conductor  55  comprises a slotted structure  57 . The slotted structure  57  comprises a frame portion  571 , a slotted portion  573 , and a hollow portion  575 . In the present invention, the transmission conductor  53 , the frame portion  571 , the slotted portion  573 , and the hollow portion  575  can be a microstrip line, a slotted line, an artificial transmission line, a modified-T circuit line, or other transmission line structure capable of transmitting signals. The slotted portion  573  surrounds the frame portion  571 , and the hollow portion  575  is formed in the frame portion  571 . Besides, at least one first impedance unit  31  and/or at least one first impedance unit  32  are disposed on the frame portion  571 , and connected with the frame portion  571 . The frame portion  571  is a quadrilateral frame, and comprises a first side  5711 , a second side  5712 , a third side  5713 , and a fourth side  5714 . The first side  5711  is connected at one end thereof to one end of the third side  5713  via the second side  5712 , and connected at one end thereof to other end of the third side  5713  via the fourth side  5714 . The first side  5711  is corresponding to the third side  5713 , and the second side  5712  is corresponding to the fourth side  5714 . The transmission conductor  53  is projectively across the first side  5711  and the third side  5713  of the frame portion  571 . In the present embodiment, the first impedance unit  31  is disposed on the first side  5711  of the frame portion  571  based on the position of the transmission conductor  53 , for example, the first impedance unit  31  is disposed on the first side  5711  of the frame portion  571  that is located at the lower left side of the transmission conductor  53 ; the second impedance unit  32  is disposed on the third side  5713  of the frame portion  571  based on the position of the transmission conductor  53 , for example, the second impedance unit  32  is disposed on the third side  5713  of the frame portion  571  that is located at the lower right side of the transmission conductor  53 . 
     In one embodiment of the present invention, the first impedance unit  31  or the second impedance unit  32  is disposed on the frame portion  571 , and directly connected to the frame portion  571 . As shown in  FIG. 14A , the frame portion  571  comprises at least one notch  5710 . The first impedance unit  31  or the second impedance unit  32  is disposed on the notch  5710  of the frame portion  571 , and the left and right ends of the first impedance unit  31  or the second impedance unit  32  are directly connected to the frame portion  571  located on both sides of the notch  5710 , respectively. 
     In another embodiment of the present invention, the first impedance unit  31  or the second impedance unit  32  is disposed on the frame portion  571 , and connected to the frame portion  571  via at least one conductive via hole. As shown in  FIG. 14B , the first reference conductor  55  is provided at the top surface thereof with the substrate  51 , and provided at the bottom surface thereof with other substrate  59 . The frame portion  571  comprises at least one notch  5710 . Two conductive via holes  591  are configured in the substrate  59 . The left and right ends of the first impedance unit  31  or the second impedance unit  32  are connected to the frame portion  571  on both sides of the notch  5710  via the corresponding conductive via holes  591 . 
     The equivalent filter circuit  200  of  FIG. 1  may be equivalently formed by the filter device  500 . The transmission conductor  53  is coupled to the frame portion  571  to generate the first equivalent transmission line model  21 . The frame portion  571  is coupled to the first reference conductor  55  to generate the second equivalent transmission line model  22 . The first master transmission conductor  211  of the first equivalent transmission line model  21  is represented as the equivalent element of the transmission conductor  53 , and the first slave transmission conductor  212  of the first equivalent transmission line model  21  is represented as the equivalent element of the frame portion  571 . The second master transmission conductor  221  of the second equivalent transmission line model  22  is represented as the equivalent element of the first reference conductor  55 , and the second slave transmission conductor  222  of the second equivalent transmission line model  22  is represented as the equivalent element of the frame portion  571 . Furthermore, the first impedance unit  31  and the second impedance unit  32  of the filter device  500  are equivalent to the first impedance unit  31  and the second impedance unit  32  in the equivalent filter circuit  200  of  FIG. 1 . 
     In one embodiment of the present invention, the electrical lengths (θ 1 , θ 2 ) and the characteristic impedances (Z 1 , Z 2 ) of the first equivalent transmission line model  21  and the second equivalent transmission line model  22  may be adjusted by modifying the length and width of the transmission conductor  53 , the frame portion  571 , and/or the slotted portion  573 . Thus, the frequency where the electromagnetic noise is to be absorbed may be further adjusted by the modification of the electrical lengths (θ 1 , θ 2 ) and the characteristic impedances (Z 1 , Z 2 ). 
     Further, referring to  FIG. 14  and  FIG. 15  at the same time, for achieving the purpose of the transmission conductor with high impedance, the filter device  500  of the present invention is provided with the frame portion  571  that is having a narrower width, and configured in the slotted structure  57 . The frame portion  571  having the narrower width and the first reference conductor  55  having a wider width may be formed an asymmetric coplanar strip. The frame portion  571  is configured on a position close to the first reference conductor  55 , which can shorten the width (W) of the slot portion  573 , so that the overall area of the filter  500  can be effectively reduced, and thereby the purpose of miniaturizing the circuit structure of the filter device  500  can be achieved. Besides, even if the frame portion  571  is very close to the first reference conductor  55 , a large amount of electric field coupling is still generated between the frame portion  571  and the first reference conductor  55 . However, since the wire body of the frame portion  571  of the filter device  500  is designed to have a thinner width, the inductive amount of the frame portion  571  will increase, and the impedance (Z 0 ) of the transmission conductor will increase accordingly, thereby the purpose that the transmission conductor is having high impedance can be achieved. 
     Referring to  FIG. 16 , there is shown a structural bottom view of a filter device according to another embodiment of the present invention, and also referring to  FIG. 4 ,  FIG. 12 , and  FIG. 13  at the same time. Comparing to the filter device  500  in  FIG. 14 , the filter device  501  in  FIG. 16  further comprises at least one third impedance  33 . The third impedance  33  is disposed on the second side  5712  or the fourth side  5714  of the frame portion  571 , and connected with the frame portion  571 . The third impedance  33  may be directly connected with the frame portion  571 , as shown in  FIG. 14A ; otherwise, the third impedance  33  may be connected with the frame portion  571  via the conductive via hole, as shown in  FIG. 14B . The equivalent filter circuit  202  in  FIG. 4  may be equivalently formed by the filter device  501  in  FIG. 16 . The transmission conductor  53  is coupled to the frame portion  571  to generate the first equivalent transmission line model  21 . The frame portion  571  distributed at the right side of the third impedance unit  33  is coupled to the first reference conductor  55  to generate the second equivalent transmission line model  22 . The frame portion  571  distributed at the left side of the third impedance unit  33  is coupled to the first reference conductor  55  to generate the third equivalent transmission line model  23 . The first master transmission conductor  211  of the first equivalent transmission line model  21  is represented as the equivalent element of the transmission conductor  53 , and the first slave transmission conductor  212  of the first equivalent transmission line model  21  is represented as the equivalent element of the frame portion  571 . The second master transmission conductor  221  of the second equivalent transmission line model  22  is represented as the equivalent element of the first reference conductor  55 , and the second slave transmission conductor  222  of the second equivalent transmission line model  22  is represented as the equivalent element of the frame portion  571 . The third master transmission conductor  231  of the third equivalent transmission line model  23  is represented as the equivalent element of the first reference conductor  55 , and the third slave transmission conductor  232  of the third equivalent transmission line model  23  is represented as the equivalent element of the frame portion  571 . Furthermore, the first impedance unit  31 , the second impedance unit  32 , and the third impedance unit  33  of the filter device  501  are equivalent to the first impedance unit  31 , the second impedance unit  32 , and the third impedance unit  33  in the equivalent filter circuit  202  of  FIG. 4 . 
     In one embodiment of the present invention, the electrical lengths (θ 1 , θ 2 , θ 3 ) and the characteristic impedances (Z 1 , Z 2 , Z 3 ) of the first equivalent transmission line model  21 , the second equivalent transmission line model  22 , and the third equivalent transmission line model  23  may be adjusted by modifying the length and width of the transmission conductor  53 , the frame portion  571 , and/or the slotted portion  573 . Thus, the frequency where the electromagnetic noise is to be absorbed may be further adjusted by the modification of the electrical lengths (θ 1 , θ 2 , θ 3 ) and the characteristic impedances (Z 1 , Z 2 , Z 3 ). 
     Referring to  FIG. 17 , there is shown a structural bottom view of a filter device according to another embodiment of the present invention, and also referring to  FIG. 7 ,  FIG. 12 , and  FIG. 13  at the same time. Comparing to the filter device  501  in  FIG. 16 , the filter device  502  in  FIG. 17  further comprises at least one fourth impedance  34 , at least one fifth impedance  35 , and at least one sixth impedance  36 . The fourth impedance  34 , the fifth impedance  35 , and the sixth impedance  36  are disposed in the slotted portion  573 . The left end or the right end of the first impedance unit  31  is connected to the first reference conductor  55  via the fourth impedance unit  34 . The left end or the right end of the second impedance unit  32  is connected to the first reference conductor  55  via the fifth impedance unit  35 . The left end or the right end of the third impedance unit  33  is connected to the first reference conductor  55  via the sixth impedance unit  36 . The equivalent filter circuit  204  of  FIG. 7  may be equivalently formed by the filter device  502  in  FIG. 17 . The fourth impedance units  34 , the fifth impedance units  35 , and the sixth impedance units  36  of the filter device  502  are equivalent to the fourth impedance units  34 , the fifth impedance units  35 , and the sixth impedance units  36  in the equivalent filter circuit  204  of  FIG. 7 . In the equivalent filter circuit  204  of  FIG. 7  and the filter device  502  of  FIG. 17 , the first impedance unit  31  and the fourth impedance units  34  located at two sides of the first impedance unit  31 , the second impedance unit  32  and the fifth impedance unit  35  located at two sides of the second impedance unit  32 , and the third impedance unit  33  and the sixth impedance unit  36  located at two sides of the third impedance unit  33  will form a π-shaped impedance assembly unit, respectively. 
     Referring to  FIG. 18 , there is shown a structural bottom view of a filter device according to another embodiment of the present invention, and also referring to  FIG. 9 ,  FIG. 12 , and  FIG. 13  at the same time. In the filter device  503  of  FIG. 18 , two or more than two first impedance units  31  are disposed on the first side  5711  of the frame portion  571 , two or more than two second impedance units  32  are disposed on the third side  5713  of the frame portion  571 , and two or more than two third impedance units  33  are disposed on the second side  5712  or the fourth sides  5714  of the frame portion  571 . Each of the fourth impedance units  34  is connected at one end thereof between the two adjacent first impedance units  31 , and connected at other end thereof to the first reference conductor  55 . Each of the fifth impedance units  35  is connected at one end thereof between the two adjacent second impedance units  32 , and connected at other end thereof to the first reference conductor  55 . Each of the sixth impedance units  36  is connected at one end thereof between the two adjacent third impedance units  33 , and connected at other end thereof to the first reference conductor  55 . The equivalent filter circuit  206  in  FIG. 9  may be equivalently formed by the filter device  503  in  FIG. 18 . In the equivalent filter circuit  206  of  FIG. 9  and the filter device  503  of  FIG. 18 , the two first impedance units  31  and the fourth impedance unit  34  connected between the two first impedance units  31 , the two second impedance units  32  and the fifth impedance unit  35  connected between the two second impedance units  32 , and the two third impedance units  33  and the sixth impedance unit  36  connected between the two third impedance units  33  will form a T-shaped impedance assembly unit, respectively. 
     Referring to  FIG. 19 , there is shown a structural bottom view of a filter device according to another embodiment of the present invention, and also referring to  FIG. 10 ,  FIG. 12 , and  FIG. 13  at the same time. The equivalent filter circuit  207  in  FIG. 10  may be equivalently formed by the filter device  504  in  FIG. 19 . Comparing to the filter device  500  in  FIG. 14  where the first impedance unit  31  and the second impedance unit  32  are disposed on the frame portion  571 , the first impedance unit  31  and the second impedance unit  32  of the filter device  504  in  FIG. 19  are disposed in the slotted portion  573 . Besides, the first side  5711  of the frame portion  571  is connected to the first reference conductor  55  via the first impedance unit  31 , and the third side  5713  of the frame portion  571  is connected to the first reference conductor  55  via the second impedance unit  32 . 
     Referring to  FIG. 20 , there is shown a structural bottom view of a filter device according to another embodiment of the present invention, and also referring to  FIG. 11 ,  FIG. 12 , and  FIG. 13  at the same time. The equivalent filter circuit  208  in  FIG. 11  may be equivalently formed by the filter device  505  in  FIG. 20 . Comparing to the filter device  504  in  FIG. 19 , the filter device  505  in  FIG. 20  further comprises at least one third impedance unit  33 . The third impedance unit  33  is disposed in the slotted portion  573 . The second side  5712  of the frame portion  571  is connected to the first reference conductor  55  via the third impedance unit  33 , or the fourth side  5714  of the frame portion  571  is connected to the first reference conductor  55  via the third impedance unit  33 . 
     Referring to  FIG. 21  and  FIG. 22 , there are shown a three-dimensional structural perspective view and a structural top view of a filter device according to another embodiment of the present invention. In the present embodiment, the number of transmission conductors  53  of the filter device  500 / 501 / 502 / 503 / 504 / 505  can be two. The two transmission conductors  53  are formed as a pair of differential transmission conductors. A differential mode signal or a common mode signal can be transmitted on the differential transmission conductors. The differential mode signal is a data signal, and the common signal is a common mode noise. The filter device  500 / 501 / 502 / 503 / 504 / 505  can be used to absorb the common mode noise by one or more impedance units  31 ,  32 ,  33 ,  34 ,  35 , and/or  36  to prevent that the common mode noise affects the transmission quality of the differential mode signal. 
     Referring to  FIG. 23 , there is shown a structural bottom view of a filter device according to another embodiment of the present invention. In the filter device  500  of the present embodiment, the slotted structure  57  further comprises a second reference conductor  577 . The second reference conductor  577  is configured in the hollow portion  575  based on the position of the transmission conductors  53 . For example, the second reference conductor  577  is located directly below the transmission conductors  53 . A capacitive coupling effect between the transmission conductors  53  and the slotted structure  57  can be increased by the configuration of the second reference conductor  577  so that the signal passing through the filter device  500  can obtain a better impedance matching so as to achieve better signal quality. In the present embodiment, the first impedance units  31  and the second impedance units  32  are disposed on the frame portion  571  located at the both sides of the second reference conductor  577 , and directly connected with the frame portion  571 , as shown in  FIG. 14A ; otherwise, the first impedance units  31  and the second impedance units  32  are disposed on the frame portion  571  located at the both sides of the second reference conductor  577 , and connected with the frame portion  571  via the conductive via holes  591 , as shown in  FIG. 14B . 
     Of course, in addition to the filter device  500 , other filter device  501 ,  502 ,  503 ,  504  or  505  can also configure the second reference conductor  577  in the hollow portion  575  of the slotted structure  57  in order to increase the capacitive coupling effect between the transmission conductors  53  and the slotted structure  57 . 
     The above disclosure is only the preferred embodiment of the present invention, and not used for limiting the scope of the present invention. All equivalent variations and modifications on the basis of shapes, structures, features and spirits described in the claims of the present invention should be included in the claims of the present invention.