Patent Publication Number: US-2023156987-A1

Title: Signal isolation device and method for improving the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to China Application Serial Number 202111336435.X, filed Nov. 12, 2021, which is herein incorporated by reference in its entirety. 
     BACKGROUND 
     Field of Invention 
     The present invention relates to a signal isolation device. 
     Description of Related Art 
     Over the years, it has become more and more critical to curb high-frequency noises and improve the performance of RF antennas and RF circuits. 
     If the noise cannot be effectively curbed, the communication performance of the RF antennas and the RF circuits will be greatly reduced. There is no technology that can realize the anti-noise structure with a simple manufacturing process. The current anti-noise structure is mostly suitable for narrow frequency bands, so it cannot be effectively used in the antenna. 
     Recently, the demand for the Internet to replace traditional telephones has been increasing, and consumers have a significant demand for high-quality Internet-enabled devices. In addition, multi-band communication has been widely used in daily life. 
     Therefore, how to provide a signal isolation device that is small in size, simple in process, and widely used in multiple frequency bands has become a research target for private enterprises and academic institutions to invest a lot of money, manpower, and time. 
     SUMMARY 
     The invention provides a method for improving a signal isolation device, including providing a signal isolation device which includes a plurality of electromagnetic band-gap (EBG) units adjoining each other, and each EBG unit has a substrate, a metal foil main body, and a plurality of metal features, the metal foil main body and the metal features are disposed on the substrate, and the metal feature extend from a periphery of the metal foil main body; generating a current concentration location related to the EBG units according to a corresponding frequency band of an insertion loss value of the signal isolation device; determining that the signal isolation device has a capacitive property or an inductive property according to the corresponding frequency band of the insertion loss value; and adjusting at least one of the metal features according to the current concentration location and according to the capacitive property or the inductive property of the signal isolation device. 
     In some embodiments of the present invention, the signal isolation device has the capacitive property, and adjusting the metal features includes adding a spiral path to one of the metal features. 
     In some embodiments of the present invention, the spiral path extends spirally from a center of the spiral path to an outward direction. 
     In some embodiments of the present invention, the signal isolation device has the inductive property, and adjusting the metal features includes adding an extension path, a portion of the extension path which is spaced apart from the metal foil main body extends along a periphery of the metal foil main body. 
     In some embodiments of the present invention, the portion of the extension path horizontally and straightly extends with respect to the periphery of the metal foil main body. 
     Another aspect of the present invention relates to a signal isolation device including at least one electromagnetic band-gap unit. The at least one electromagnetic band-gap unit includes a substrate, a metal foil main body, and a plurality of T-shaped metal foil features. The metal foil main body is disposed on the substrate, and the metal foil main body is square. The T-shaped metal foil features which are disposed on the substrate and extend from a periphery of the metal foil main body, wherein the T-shaped metal foil features are in a rotational symmetry around a center of the metal foil main body. 
     In some embodiments of the present invention, each T-shaped metal foil feature comprises a middle shaft portion, a first lateral portion, and a second lateral portion, wherein the middle shaft portion is disposed between the first lateral portion and the second lateral portion, the first lateral portion has a first length with respect to the middle shaft portion greater than a second length of the second lateral portion with respect to the middle shaft portion. 
     In some embodiments of the present invention, a ratio of the first length to a side length of the metal foil main body is between 0.45 and 0.58. 
     In some embodiments of the present invention, another ratio of the second length to the side length of the metal foil main body is between 0.1 and 0.3. 
     In some embodiments of the present invention, the substrate is square and has a side length ranging from about 7 mm to 25 mm. 
     In some embodiments of the present invention, the metal foil main body has a side length ranging from 5 mm to 20 mm. 
     In some embodiments of the present invention, the metal foil main body has a side length smaller than a side length of the substrate which is square. 
     In some embodiments of the present invention, the at least one electromagnetic band-gap unit includes a plurality of electromagnetic band-gap units which are arranged in a straight raw, one of the T-shaped metal foil features of one of the electromagnetic band-gap units joins one of the T-shaped metal foil features of another one of the electromagnetic band-gap units. 
     In some embodiments of the present invention, the at least one electromagnetic band-gap unit includes a plurality of electromagnetic band-gap units which are arranged in a straight raw, one of the T-shaped metal foil features of one of the electromagnetic band-gap units is in direct contact with one of the T-shaped metal foil features of another one of the electromagnetic band-gap units. 
     Another aspect of the present invention relates to a signal isolation device which includes a plurality of electromagnetic band-gap units arranged in a row, and each electromagnetic band-gap unit includes a square substrate, a square metal foil main body, and a plurality of T-shaped metal foil features. The square metal foil main body is disposed on the substrate. The plurality of T-shaped metal foil features are disposed on the substrate and extending from a periphery of the metal foil main body, and the T-shaped metal foil features are in a rotational symmetry around a center of the metal foil main body. 
     In some embodiments of the present invention, each T-shaped metal foil feature includes a middle shaft portion, a first lateral portion, and a second lateral portion, wherein the middle shaft portion is disposed between the first lateral portion and the second lateral portion, the first lateral portion has a first length with respect to the middle shaft portion greater than a second length of the second lateral portion with respect to the middle shaft portion. 
     In some embodiments of the present invention, a ratio of the first length to a side length of the metal foil main body is between 0.45 and 0.58. 
     In some embodiments of the present invention, another ratio of the second length to the side length of the metal foil main body is between 0.1 and 0.3. 
     In some embodiments of the present invention, the substrate has a side length ranging from about 7 mm to 25 mm. 
     In some embodiments of the present invention, the metal foil main body has a side length smaller than a side length of the substrate. 
     In embodiments of the present invention, a signal isolation device with electromagnetic band-gap units and a method for improving the same are provided, and the method can further improve the isolation abilities in the desired frequency bands. Therefore, the signal isolation device has outstanding isolation abilities in WiFi dual-bands and WiFi 6E bands. 
     It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by Office upon request and payment of the necessary fee. The disclosure can be more fully understood by reading the following detailed description of the embodiment, with reference made to the accompanying drawings as follows. 
         FIG.  1    illustrates a method for improving a signal isolation device in accordance with some embodiments of the present invention. 
         FIG.  2    illustrates a schematic view of a signal isolation device in accordance with some embodiments of the present invention. 
         FIG.  3    illustrates a comparison diagram of return loss of a signal isolation device in accordance with some embodiments of the present invention. 
         FIG.  4    illustrates a current distribution diagram of a signal isolation device in accordance with some embodiments of the present invention. 
         FIG.  5    illustrates a smith chart of a signal isolation device in accordance with some embodiments of the present invention. 
         FIG.  6    illustrates a top view of a signal isolation device in accordance with some embodiments of the present invention. 
         FIG.  7    illustrates a top view of a signal isolation device in accordance with some embodiments of the present invention. 
         FIG.  8    illustrates a schematic view of an electromagnetic band-gap unit in accordance with some embodiments of the present invention. 
         FIG.  9    illustrates a top view of an electromagnetic band-gap unit in accordance with some embodiments of the present invention. 
         FIG.  10    illustrates a comparison diagram of return loss of a signal isolation device in accordance with some embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
     Reference is made to  FIG.  1   , which illustrates a method  100  for improving a signal isolation device. The method  100  starts from a step  110 , which includes providing a signal isolation device, and the signal isolation device includes a plurality of electromagnetic band-gap (EBG) units adjoining each other. Each EBG unit includes a substrate, a metal foil main body, and a plurality of metal features, and the metal foil main body and the metal features are disposed on the substrate. The method  100  includes a step  130  which includes generating a current concentration location related to the EBG units according to a corresponding frequency band of an insertion loss value of the signal isolation device. The method  100  further includes a step  150  which includes determining that the signal isolation device has a capacitive property or an inductive property according to the corresponding frequency band of the insertion loss value. The method  100  further includes a step  170  which includes adjusting the metal features according to the current concentration location and according to the capacitive property or the inductive property of the signal isolation device. Therefore, the method  100  can efficiently decrease the insertion loss values related to the corresponding frequency band of the signal isolation device, so as to dramatically improve the isolation abilities of the corresponding frequency band of the signal isolation device. 
     Reference is made to  FIGS.  1 - 2   , the step  110  includes providing the signal isolation device  200  which includes adjacent EBG units, and each EBG unit  210  includes a substrate  211 , a metal foil main body  213 , and a plurality of metal features  215 . The metal foil main body  213  and the metal features  215  are located on the substrate  211 , and the metal features  215  extend from a periphery of the metal foil main body  213 . In addition, one of the metal features  215  of each EBG unit  210  joins another one of the metal features  215  of each EBG unit  210 , so as to provide outstanding signal isolation ability. The one of the metal features  215  of each EBG unit  210  can be indirect contact with the another one of the metal features  215  of each EBG unit  210 . 
     In some embodiments of the present invention, the metal foil main body  213  is square, and the metal features  215  is L-shaped. The metal features  215  respectively adjoin corners of the metal foil main body  213 , and the metal features  215  are in a rotational symmetry around a center C 1  of the metal foil main body  213 . The center C 1  can be a feeding point. In addition, the metal features  215  has a first extension portion  215   a  and a second extension portion  215   b,  and the first extension portion  215   a  directly joins the metal foil main body  213  and vertically extends with respect to a side of the square metal foil main body  213 . The second extension portion  215   b  which horizontally extends with respect to the side of the square metal foil main body  213  is spaced apart from the side of the metal foil main body  213 , and the first extension portion  215   a  is connected between the metal foil main body  213  and the second extension portion  215   b.  In addition, each EBG unit  210  further includes a flat metal foil which is disposed on a bottom surface of the substrate  211 , but the present invention is not limited in this respect. 
     Specifically, the substrate  211  includes a single layer printed circuit board (PCB). For instance, the substrate  211  is a printed circuit board in FR4 printed circuit board specification, and the substrate  211  can be manufactured by laminating epoxy resin and woven glass. In addition, the metal foil main body  213  and the metal features  215  can be a continuous piece of material or not a continuous piece of material, and the metal foil main body  213  and the metal features  215  can include gold, silver, copper, stannum, plumbum, or alloy thereof. The metal foil main body  213  and the metal features  215  can be manufactured by a laser cutting process, an etching process, or a machining process. The present invention is not limited in this respect. 
     Reference is made to  FIGS.  1 - 4   . The step  130  includes generating a current concentration location related to the EBG units  210  according to a corresponding frequency band of the insertion loss value of the signal isolation device  200 , and  FIGS.  3 - 4    can represent the step  130 .  FIG.  3    illustrates a comparison diagram of return loss, and the curved line S 1  in  FIG.  3    at least shows insertion loss values of the signal isolation device  200  between 2 Mhz and 14 Mhz.  FIG.  4    illustrates a current distribution diagram. The step  130  includes choosing an insertion loss value between 2 Mhz and 10 Mhz. For instance, the highest insertion loss value among insertion loss values in  FIG.  3    can be chosen. In some embodiments of the present invention, the step  130  includes choosing a point P 1  which represents the frequency band of 7.25 Mhz which is between 7 Mhz and 7.5 Mhz. The insertion loss value of the point P 1  has an insertion loss value about −20 dB. In addition, an electromagnetic wave of about 7.25 Mhz is generated to pass through the signal isolation device  200 . By measuring or simulating the current distribution diagram of the signal isolation device  200 , a current concentration location R 1  in  FIG.  4    can be obtained. Specifically, electromagnetic simulation software such as High Frequency Structure Simulator (HFSS) and/or a magnetometer can be used to simulate  FIG.  4   . The present invention is not limited in this respect. 
     Reference is made to  FIGS.  1  and  5   . The step  150  includes determining that the signal isolation device  200  has a capacitive property or an inductive property according to the corresponding frequency band of the insertion loss value. For instance, the line M 1  in  FIG.  5   , which is a smith chart, can represent the condition of the signal isolation device  200  measured or simulated in the corresponding frequency band. As known from the line M 1 , the signal isolation device  200  has the inductive property. In some other embodiments of the present invention, the line M 2  in  FIG.  5    can represent the signal isolation device  200  in different frequency bands and/or in different size from the line M 1 . As known from the line M 2 , the signal isolation device  200  has the capacitive property. For people who have general knowledge in the art, they well know the methods for measuring the signal isolation device  200  and illustrating the smith chart, and thus the detail information about measuring the signal isolation device  200  and illustrating the smith chart are neglected. 
     Reference is made to  FIGS.  1 ,  4 , and  6   . In one or more embodiments of the present invention, the step  170  includes adjusting the metal features  215  according to the inductive property or the capacitive property of the signal isolation device  200  and the current concentration location R 1 . In  FIG.  4   , the current concentration location R 1  immediately adjoins a junction between the first extension portion  215   a  and the second extension portion  215   b,  and the step  170  can includes adjusting the junction between the first extension portion  215   a  and the second extension portion  215   b.  In some embodiments of the present invention, when the signal isolation device  200  has the capacitive property, the step  170  includes adding a spiral path X 1  to at least one of the metal features  215  around the current concentration location R 1 . Furthermore, additional spiral path X 1  can be added to the other metal features  215  at corresponding positions such that all of the spiral paths and the meatal features are in a rotational symmetry around a center C 1 . The spiral path X 1  extends from a center to an outward direction, and the spiral path X 1  are made of metal, such as gold, silver, copper, stannum, plumbum, or alloy thereof. The present invention is not limited in this respect. Specifically, the spiral path X 1  can be a rectangular spiral structure, and the spiral path X 1  has portions which are vertical to or horizontal to an extension direction of the second extension portion  215   b.  The present invention is not limited in this respect. In some other embodiments of the present invention, the spiral path X 1  can be a circular spiral structure or an ellipse spiral structure. 
     In some embodiments of the present invention, the step  170  includes that the signal isolation device  200  has the capacitive property. When the signal isolation device  200  has the capacitive property, the step  170  further includes adding an extension path X 2  to at least one of the metal features  215  around the current concentration location R 1 . Furthermore, additional extension paths X 2  can respectively be added to the other metal features  215  at corresponding positions, such that all the metal features and the extension paths are in a rotational symmetry around a center C 1 . The extension path X 2  are made of metal, such as gold, silver, copper, stannum, plumbum, or alloy thereof, but the present invention is not limited in this respect. The extension path X 2  has at least one portion which is spaced apart from the metal foil main body  213  and extends with respect to a periphery of the metal foil main body  213 . In some embodiments of the present invention, the at least one portion of the extension path X 2  extends straightly and extends horizontally with respect to the periphery of the metal foil main body  213 , and the present invention is not limited in this respect. 
     Reference is made to  FIGS.  7 - 9   .  FIG.  7    illustrates a schematic view of a signal isolation device  300  which is manufactured by the method  100 .  FIG.  8    illustrates a schematic view of an EBG unit  310 .  FIG.  9    illustrates a top view of the EBG unit  310 . In some embodiments of the present invention, the signal isolation device  300  includes at least one EBG unit  310  which has a substrate  311 , a metal foil main body  313 , and a plurality of T-shaped metal foil features  315 . The metal foil main body  313  is located on the substrate  311 , and the metal foil main body  313  is rectangular or square. The T-shaped metal foil features  315  which are located on the substrate  311  extend from sides of the metal foil main body  313  respectively, and the T-shaped metal foil features  315  is in a rotational symmetry around a center C 2  of the metal foil main body  313 , in which the center C 2  can be a feeding point. In some embodiments of the present invention, the signal isolation device  300  includes a plurality of the EBG units  310  which are arranged along a straight row, and one of the T-shaped metal foil features  315  of one of the EBG units  310  joins or is in direct contact with one of the T-shaped metal foil features  315  of another one of the EBG units  310 . The EBG units  310  are connected to each other for improving the signal isolation ability of the signal isolation device  300 . In some embodiments of the present invention, the signal isolation device  300  further includes a flat metal foil  317  which is disposed on a bottom surface of the substrate  311 , but the present invention is not limited in this respect. 
     Specifically, the substrate  311  can includes a single-layer printed circuit board. For instance, the substrate  311  is a printed circuit board in FR4 printed circuit board specification, and the substrate  311  can be manufactured by laminating epoxy resin and woven glass. In addition, the metal foil main body  313  and the T-shaped metal foil features  315  are a continuous piece of material or not a continuous piece of material, and the metal foil main body  313  and the T-shaped metal foil features  315  are made of gold, silver, copper, stannum, plumbum, or alloy thereof. The metal foil main body  313  and the T-shaped metal foil features  315  can be manufactured by a laser cutting process, an etching process, or a machining process. The present invention is not limited in this respect. 
     In some embodiments of the present invention, the substrate  311  is square, and the substrate  311  has a side length L 1  ranging from about 7 mm to 25 mm. Preferably, the side length L 1  of the substrate  311  ranges from about 8 mm to about 20 mm. For instance, the side length L 1  of the substrate  311  is about 8.4 mm. In addition, the metal foil main body  313  is also square, and the metal foil main body  313  has a side length L 2  smaller than the side length L 1  of the substrate  311 . The side length L 2  of the metal foil main body  313  ranges from about 5 mm to 20 mm. Preferably, the side length L 2  of the metal foil main body  313  ranges from about 6 mm to about 12 mm. For instance, the side length L 1  of the substrate  311  is about 7.4 mm. 
     In some embodiments of the present invention, the T-shaped metal foil feature  315  extends from one side of the square metal foil main body  313 , and the T-shaped metal foil features  315  includes a middle shaft portion  315   a,  a first lateral portion  315   b,  and a second lateral portion  315   c.  The first lateral portion  315   b  and the second lateral portion  315   c  are substantially rectangular, and the middle shaft portion  315   a  is located between the first lateral portion  315   b  and the second lateral portion  315   c.  The first lateral portion  315   b  and the second lateral portion  315   c  respectively extend along two opposite directions and horizontally extend with respect to the side of the metal foil main body  313 . In addition, the first lateral portion  315   b  has a first length Q 1  with respect to the middle shaft portion  315   a  greater than a second length Q 2  of the second lateral portion  315   c  with respect to the middle shaft portion  315   a,  and the first length Q 1  and the second length Q 2  is measured along a direction parallel to the aforementioned side of the metal foil main body  313 . 
     In some embodiments of the present invention, a ratio of the first length Q 1  to the side length L 2  of the metal foil main body  313  is between 0.45 and 0.58. When the ratio of the first length Q 1  to side length L 2  of the metal foil main body  313  is between 0.45 and 0.58, the signal isolation device  300  has outstanding signal isolation abilities. In some embodiments of the present invention, a ratio of the second length Q 2  to the side length L 2  of the metal foil main body is between 0.1 and 0.3. When the ratio of the second length Q 2  to the side length L 2  of the metal foil main body is between 0.1 and 0.3, the signal isolation device  300  has outstanding signal isolation abilities. The present invention is not limited in this respect. 
     In some embodiments of the present invention, the first lateral portion  315   b  has a first width T 1  with respect to the corresponding side of the metal foil main body  313 , and the first width T 1  is smaller than a second width T 2  of the second lateral portion  315   c  with respect to the corresponding side of the metal foil main body  313 . The first width T 1  and the second width T 2  are measured along a direction vertical to the corresponding side of the metal foil main body  313 . Specifically, a ratio of the first width T 1  to the second length L 2  of the metal foil main body  313  is between 0.0125 and 0.05, and a ratio of the second width T 2  to second length L 2  of the metal foil main body  313  is between 0.02 and 0.05 such that the signal isolation device  300  has outstanding signal isolation abilities. 
     In one or more embodiments of the present invention, the middle shaft portion  315   a  which is rectangular extends away from the metal foil main body  313 , and the middle shaft portion  315   a  has a height H 1  with respect to the metal foil main body  313 , in which the height H 1  is between 0.4 mm and 0.6 mm. For instance, the height H 1  of the metal foil main body  313  is 0.5 mm. In addition, the middle shaft portion  315   a  has a width W 1  between 0.15 mm and 0.25 mm. For instance, the width W 1  of the middle shaft portion  315   a  is 0.2 mm. The present invention is not limited in this respect. 
     Please refer to  FIG.  10   , which illustrates a comparison diagram of return loss, and the curved line S 2  in  FIG.  10    represents return loss values of the signal isolation device  300 . As known from  FIG.  10   , the return loss values of the signal isolation device  300  are smaller than −40 dB regarding the frequency bands from 2 Mhz to 10 Mhz, and thus the signal isolation device  300  can efficiently cover WiFi dual-bands and WiFi 6E bands which are from 2.4 GHz to 7.125 GHz, so as to provide excellent signal isolation abilities in these band ranges. 
     In embodiments of the present invention, a signal isolation device with electromagnetic band-gap units and a method for improving the same are provided, and the method can further improve the isolation abilities in the desired frequency bands. Therefore, the signal isolation device has outstanding isolation abilities in WiFi dual-bands and WiFi 6E bands. 
     Although the present invention has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims.