Patent Publication Number: US-2021193377-A1

Title: Biorthogonal windings on transformer and common mode choke for network port

Description:
STATEMENT OF RELATED APPLICATION 
     The present application is a divisional of U.S. patent application Ser. No. 15/818,950, filed Nov. 21, 2017, the contents of which are incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to magnetic components, and more particularly to a transformer and common mode choke for a network port. 
     BACKGROUND 
     Transformers and common mode chokes are used together at network interfaces between network cables and electronic devices to provide isolation and common mode noise suppression. The transformer electromagnetically couples signals from a primary side to a secondary side. Due to EMI (electromagnetic interference) concerns, the transformer is often coupled with a common mode choke (CMC). The common mode choke allows data signals to pass through unimpeded while presenting high impedance to common mode signals and noise, thereby removing high frequency noises. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is cross-sectional view of an integrated connector module with a transformer and common mode choke array, in accordance with one embodiment. 
         FIG. 2A  is a perspective of the transformer and common mode choke array of  FIG. 1  with toroidal cores. 
         FIG. 2B  is a perspective of a transformer and common mode choke array with square cores for use in the integrated connector module of  FIG. 1 . 
         FIG. 3  is a perspective showing internal components in a LAN (Local Area Network) magnetics module, in accordance with one embodiment. 
         FIG. 4A  is a perspective of a transformer and common mode choke array of  FIG. 3  with toroidal cores. 
         FIG. 4B  is a perspective of a transformer and common mode choke array with square cores for use in the LAN magnetics module of  FIG. 3 . 
         FIG. 5A  is a top view of a toroidal core with winding retaining grooves for maintaining a position of windings in the transformer and common mode choke array, in accordance with one embodiment. 
         FIG. 5B  is a perspective of the toroidal core with the winding retaining grooves shown in  FIG. 5A . 
         FIG. 6A  is an electrical schematic of the transformer and common mode choke array, in accordance with one embodiment. 
         FIG. 6B  is an electrical schematic for a portion of the transformer and common mode choke array with a center tap with common mode termination. 
         FIG. 7A  is a graph illustrating improved common mode noise rejection with biorthogonal windings. 
         FIG. 7B  is a graph illustrating reduced crosstalk with the biorthogonal windings. 
         FIG. 8  is a block diagram depicting an example of a network device on which a port comprising the embodiments described herein may be located. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Overview 
     In one embodiment, an apparatus generally comprises a plurality of transformers and a plurality of common mode chokes, each of the transformers and the common mode chokes comprising a magnetic core and windings wound around the magnetic core at generally opposite sides thereof. The transformers and common mode chokes are arranged in an array with the windings on each of the magnetic cores positioned generally orthogonal to the windings of adjacent magnetic cores in the array to reduce crosstalk and improve common mode noise rejection. 
     In another embodiment, an apparatus generally comprises an array of transformers and common mode chokes each comprising a magnetic core and windings wound around the magnetic core at opposing locations on the magnetic core, and a retaining groove on each of the magnetic cores to maintain the windings in their opposing locations on the magnetic core. The transformers and common mode chokes are positioned in the array with the windings on each of the magnetic cores located generally orthogonal to the windings of adjacent magnetic cores in the array to reduce crosstalk and improve common mode noise rejection. 
     In yet another embodiment, an apparatus generally comprises a connector for receiving a plurality of network communications cables, the connector comprising a plurality of transformers and a plurality of common mode chokes, each of the transformers and the common mode chokes comprising a magnetic core and windings wound around the magnetic core at generally opposite sides thereof. The apparatus further comprises a processor for processing data received from the connector. The transformers and common mode chokes are arranged in an array with the windings on each of the magnetic cores positioned generally orthogonal to the windings of adjacent magnetic cores to reduce electromagnetic interference in the array. 
     EXAMPLE EMBODIMENTS 
     The following description is presented to enable one of ordinary skill in the art to make and use the embodiments. Descriptions of specific embodiments and applications are provided only as examples, and various modifications will be readily apparent to those skilled in the art. The general principles described herein may be applied to other applications without departing from the scope of the embodiments. Thus, the embodiments are not to be limited to those shown, but are to be accorded the widest scope consistent with the principles and features described herein. For purpose of clarity, details relating to technical material that is known in the technical fields related to the embodiments have not been described in detail. 
     Transformers and common mode chokes are often used together in network ports and may be integrated into a network connector or packaged together as a discrete component. Both configurations require the transformers and common mode chokes to be positioned close together due to limited space availability. Conventional systems are configured with windings (coils) of the transformer and common mode choke mostly distributed around the entire circumference of a toroidal magnetic core. This winding configuration makes the coils close to each other in one stack or between stacks of transformers and common mode chokes, which increases the coupling between the coils and may cause Electromagnetic Interference (EMI) and Signal Interference (SI) problems, which can corrupt information, causing equipment to lose performance, malfunction, or fail. 
     These problems may be addressed by adding extra ferrite core on a network cable or a ferrite bead in a PCB (Printed Circuit Board) to increase common mode noise suppression, or digital signal processing technology may be introduced to increase Signal-to-Noise Ratio (SNR) to mitigate problems caused by crosstalk. However, these fixes result in a need for additional resources and the changes needed to reduce EMI to acceptable levels will increase labor and material costs and may cause degradation to other electrical performance parameters, which can compromise signal integrity. 
     The embodiments described herein include biorthogonal windings for transformers and common mode chokes for a network port to minimize coupling between coils and thereby enhance common mode noise rejection and reduce crosstalk. As described in detail below, the biorthogonal winding is orthogonal to adjacent windings between adjacent transformers and common mode chokes. 
     Referring now to the drawings, and first to  FIG. 1 , an example of a cable assembly comprising a plug (male connector)  10  and cable  11  coupled to an Integrated Connector Module (ICM) (port, jack, receptacle, receiver, female connector, Ethernet receptacle)  12  is shown. The ICM  12  includes a housing with the receptacles on one face and connections to a PCB (printed circuit board)  16  on another side. The ICM  12  may be used for connecting communications equipment through cables  11  in a data communications network, for example. The ICM  12  may include any number of ports each comprising a receptacle (cavity, opening)  13  formed in a body of the ICM for receiving a free end of the plug  10 . As shown in the example of  FIG. 1 , the plug  10  may include a resilient tab  14  configured to rest against an inner surface of the ICM port to lock the plug in place. 
     The ICM  12  comprises a transformer and common mode choke array  15  coupled to the PCB  16 . The connector  12  may be mounted onto the PCB  16  using any suitable connection means, generally indicated at  20 . The PCB  16  may include, for example, a plurality of conductive pads with coil wires from the transformer and common mode choke array  15  soldered thereto. The connector  12  may further include a Bob Smith Termination (BST), generally indicated at  17 , or any other circuit providing common mode termination of wires. 
     The ICM  12  is operable to remove common mode noise using the common mode choke and magnetically isolate signal wires using the transformer. The term “noise” as used herein may refer to any undesired signal component that is present in the circuit, including, for example, any discrepancy between an average of two differential signals and a reference voltage. 
     In one example, the transformer and common mode choke array  15  comprises two rows of transformers and common mode chokes stacked vertically, as shown in  FIG. 1 . In this example, each network port has four signal pairs and each signal pair has one transformer and one common mode choke. Thus, four, two row stacks of transformers and common mode chokes are placed inside of the connector for one port and need to be placed close to one another due to space limitations. 
     Each transformer and common mode choke within the array  15  comprises a magnetic core  18  and windings (coils)  19  wound on generally opposite sides of the magnetic core. As described in detail below, the transformers and common mode chokes are arranged in the array  15  with the windings  19  on each of the magnetic cores  18  positioned generally orthogonal to the windings of adjacent cores in the array to minimize coupling between the coils thereby enhancing common mode noise rejection and reducing crosstalk (reducing EMI). 
       FIG. 2A  is an enlarged perspective of the transformer and common mode choke array  15  of  FIG. 1 . As previously noted, the transformer and common mode choke array  15  comprises a plurality or transformer and common mode choke assemblies each comprising a magnetic core  18  and windings  19  (insulated wire wound on core). The windings  19  may include, for example, primary and secondary windings disposed at diametrically opposed locations across the core (i.e., generally opposite sides of the core) or two winding groups each comprising both primary and secondary windings, with the two groups located on opposite sides of the core. Thus, there are two angular sections  24  of the core  18  that contain no windings, and the two windings  19  are spaced from one another moving circumferentially around the core. In the example shown in  FIG. 2A , the coils are wound over two sections, each section having an angular width of less than ninety degrees. 
     As shown in  FIG. 2A , each core and coil assembly is positioned such that the respective windings  19  are located generally orthogonal to each adjacent winding. The windings  19  within the array are referred to herein as biorthogonal windings, since each of the two windings on the core  18  is positioned generally orthogonal to the windings on an adjacent core in the same plane or an adjacent core stacked vertically above or below the core and coil assembly. In one example, each stack (i.e., one of the four stacks shown in  FIG. 2A ) comprises a common mode choke positioned over a transformer. 
     In the example shown in  FIGS. 1 and 2A  the array  15  comprises toroidal cores  18 . The cores may also be rectangular (e.g., square) as shown in the transformer and common mode choke array  25  of  FIG. 2B . Each core  28  comprises four sides with only two opposing sides having coils  29  wound thereon. The two remaining sides are bare (i.e., have no windings). The windings  29  are located on opposite sides of the cores  28 , with the cores positioned such that the windings are generally orthogonal to one another on adjacent cores in the same plane or an adjacent core stacked vertically above or below the core. 
     Referring again to  FIG. 1 , the ICM  12  may comprise, for example, an RJ45 network connector that has a LAN (Local Area Network) magnetic interface circuit and common mode termination components for each port integrated into the connector housing to form a functional unit. In another embodiment, the transformer and common mode choke array may be packaged together as a discrete component, as shown in  FIG. 3 , and placed on a PCB for the network port. 
       FIG. 3  shows a transformer and common mode choke array  35  packaged together as a discrete component referred to as a LAN (Local Area Network) magnetic device (module, circuit, component)  30 . Each signal pair has one transformer and one common mode choke, which cascade together as one group. The array  35  comprises a plurality of transformers and common mode chokes, each comprising a magnetic core  38  and a pair of windings  39  wound around the core at generally opposite sides thereof. 
       FIG. 4A  is a perspective of the transformer and common mode choke array  35  of  FIG. 3 , which comprises a plurality or transformers and common mode choke assemblies each comprising a magnetic core  38  and windings (coil, insulated wire wound on core)  39 . Each core and winding assembly is positioned such that the respective windings  39  are located generally orthogonal to windings on adjacent cores, as previously described with respect to  FIG. 2A . 
       FIG. 4B  shows an array  45  comprising rectangular (square) cores  48 . As previously described, windings  49  are located on opposite sides of each core  48 , with the cores positioned such that the windings are generally orthogonal to one another on adjacent cores. Thus, a side of the core  48  containing one of the pair of windings  49  is positioned adjacent to a side of a core that contains no windings. 
     In one example, the magnetic core  18 ,  28 ,  38 ,  48  has a diameter (toroidal core) or width and height (square core) of approximately 4 mm and a height of approximately 2.45 mm. It is to be understood that this is only an example and that the core may be any suitable size or shape to fit within the ICM or LAN magnetics module. Also the array  15 ,  25 ,  35 ,  45  may contain any number, arrangement, or type of core and winding assemblies. 
     The square cores  28 ,  48  shown in  FIGS. 2B and 4B  help to maintain the windings  29 ,  49  in their original orthogonal position within the array  25 ,  45  since the windings are unlikely to migrate over corners of the rectangular core. However, for the toroidal core  18 ,  38  of  FIGS. 2A and 4A , the coils  19 ,  39  may not stay in their original targeted area of the core with each of the windings generally opposite one another on the core. In order to provide consistency in the position of the windings within the array  15 ,  35 , a notched magnetic core may be used, as shown in  FIGS. 5A and 5B . 
       FIGS. 5A and 5B  show a top view and a perspective view, respectively, of a core  58  and pair of windings  59  of a transformer or common mode choke, in accordance with one embodiment. In this example, the core  58  comprises retaining grooves (notches, slots)  54 , which help to maintain the windings  59  in a position generally diametrically opposed from one another on the core. The windings  59  are located within the retaining groove  54  to provide a consistent winding location so that the windings will remain biorthogonal to windings on adjacent toroidal cores. These discrete alignment grooves  54  ensure core-to-core winding repeatability. In the example shown in  FIGS. 5A and 5B , the retaining groove  54  comprises a necked down portion extending circumferentially over two angular portions of the core. 
     It is to be understood that the retaining groove shown in  FIGS. 5A and 5B  and described above is only an example and that other retaining means may be used without departing from the scope of the embodiments. For example, the retaining groove may be located only on an inner surface or outer surface of the core or may comprise a pair of raised tabs or recessed slots or notches, which help to maintain the windings  59  within their specified angular target area on the core  58 . The grooves  54  may be, for example, angled to facilitate winding operations in addition to other alignment benefits. 
     It is to be understood that the connector assembly, LAN magnetics, and transformer and common mode choke arrays shown in  FIGS. 1, 2A, 2B, 3, 4A, and 4B  and described herein are only examples and that other port, plug, cable, or connector configurations, including those covered by different standards or codes, may be used or different configuration arrays (number of components, arrangement of rows, stacks) may be used without departing from the scope of the embodiments. For example, the connector may comprise any number of ports and may be configured for operation with PoE (Power over Ethernet). The embodiments may be used with various types of connectors used within the telecommunications industry, such as registered jacks RJ45 type connectors, or any other type of connectors, plugs, interfaces, or adapters used in the telecommunications industry, computer industry, automotive industry, or other industries. 
       FIG. 6A  shows an example schematic for an eight port connector with common mode chokes  60  and transformers  62 . A pair of traces (positive signal wire  64  and negative signal wire  66 ) at Port  1  goes through common mode choke  60  and passes through transformer  62 . The common mode choke  60  is connected between a line side of the port and one of the windings of the transformer  62 . One winding of the transformer  62  is connectable on the network via the connector with the other winding connected to the common mode choke  60 . Referring to Port  2 , for example, one end  65  of the coil of the transformer  62  is electrically connected to a first terminal of Port  2  and another end  67  is electrically connected to a second terminal of Port  2 . In conventional systems in which all of the windings are close to each other (i.e., winding extending over a majority of the core and positioned adjacent to one another in array), capacitance between the coils (e.g., between wires  64  and  65  and between adjacent wires between Port  1  and Port  3 , Port  2  and Port  4 , etc.) is larger than with the biorthogonal windings described herein, which leads to worse common mode noise rejection and crosstalk. 
     In one embodiment, a center tap  69  may be provided at the transformer  62  with common mode termination as shown in  FIG. 6B . In the example shown in  FIG. 6B , the termination network is connected to the transformer through capacitor  61 . The center tap  69  may provide extra common mode noise rejection at higher frequencies (e.g., 3-5 dB improvement above 100 MHz, 20 dB improvement below 100 MHz). 
     As shown in the example simulations of  FIGS. 7A and 7B , the biorthogonal windings provide improved common mode noise rejection and crosstalk performance over conventional systems without biorthogonal windings. In this example, the biorthogonal winding embodiments provide almost 5-10 dB improvement over conventional system in all frequencies in common mode noise rejection ( FIG. 7A ). With regard to crosstalk shown in  FIG. 7B , the biorthogonal winding embodiments provide an improvement of around 10-30 dB above frequencies of 100 MHz, as compared with conventional systems. 
     The embodiments described herein may operate in the context of a data communications network including multiple network devices. The network may include any number of network devices in communication via any number of nodes (e.g., routers, switches, gateways, controllers, edge devices, access devices, aggregation devices, core nodes, intermediate nodes, or other network devices), which facilitate passage of data within the network. The network devices may communicate over one or more networks (e.g., local area network (LAN), metropolitan area network (MAN), wide area network (WAN), virtual private network (VPN) (e.g., Ethernet virtual private network (EVPN), layer 2 virtual private network (L2VPN)), virtual local area network (VLAN), wireless network, enterprise network, corporate network, data center, Internet, intranet, radio access network, public switched network, or any other network). 
       FIG. 8  illustrates an example of a network device  80  that may implement the embodiments described herein. In one embodiment, the network device  80  is a programmable machine that may be implemented in hardware, software, or any combination thereof. The network device  80  includes one or more processor  82 , memory  84 , and network interface (port)  86  comprising the transformer and common mode choke array described herein. 
     Memory  84  may be a volatile memory or non-volatile storage, which stores various applications, operating systems, modules, and data for execution and use by the processor  82 . The network device  80  may include any number of memory components. 
     Logic may be encoded in one or more tangible media for execution by the processor  82 . For example, the processor  82  may execute codes stored in a computer-readable medium such as memory  84 . The computer-readable medium may be, for example, electronic (e.g., RAM (random access memory), ROM (read-only memory), EPROM (erasable programmable read-only memory)), magnetic, optical (e.g., CD, DVD), electromagnetic, semiconductor technology, or any other suitable medium. In one example, the computer-readable medium comprises a non-transitory computer-readable medium. The processor  82  may process data received from the connector (port)  86 . The network device  80  may include any number of processors  82 . 
     The network interface  86  may comprise any number of interfaces (linecards, ports) for receiving data or transmitting data to other devices. The network interface  86  may include, for example, an Ethernet interface for connection to a computer or network. As described above, the interface  86  may comprise one or more connectors configured to receive one or more plugs. The term “connector” as used herein may refer to an ICM as shown in  FIG. 1  or a device comprising a separate LAN magnetics module as shown in  FIG. 3 . 
     It is to be understood that the network device  80  shown in  FIG. 8  and described above is only an example and that different configurations of network devices may be used. For example, the network device  80  may further include any suitable combination of hardware, software, algorithms, processors, devices, components, or elements operable to facilitate the capabilities described herein. 
     Although an apparatus has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations made without departing from the scope of the embodiments. Accordingly, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.