Electromagnetic emission detection, transceiver and system

A transceiver, TX/RX PHY, arranged for bi-directional data communication of a node with a counterpart node connected to a point-to-point network using differential mode signaling over a single twisted-pair cable is disclosed. The transceiver, TX/RX PHY, includes a common mode choke arranged between of the TX/RX PHY and the single twisted-pair cable and provided for common mode current suppression. Further included is a switching arrangement arranged between the TX/RX PHY, the common mode choke and the single twisted-pair cable and configured to switchably change a polarity of one of the windings of the common mode choke. A detection section is included and coupled via the switching arrangement to the common mode choke and configured to detect a common mode signal on the single twisted-pair cable in response to a transmission of a test signal by the counterpart node.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority under 35 U.S.C. § 119 of European Patent application no. 17209774.3, filed on Dec. 21, 2017, the contents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The present disclosure relates generally to an Ethernet transceiver and in particular to an electromagnetic emission detection on a communication link and methodologies to reduce the electromagnetic emission.

BACKGROUND

In general, Ethernet is a point-to-point communication technology. More complex networks are created by using layer 2 (according to the ISO/OSI stack) bridges (also called switches). Switches enable the definition of complex network topologies and offer many services including the basic relaying of frames (the basic Ethernet communication element) from one source node to multiple destinations, and more complex operations such as channel bandwidth allocation, network partitioning via virtual LANs (VLANs) and traffic prioritization.

The bandwidth requirements of modern and future automotive applications are posing a relevant challenge to current in-vehicle networking (IVN) technologies such as Controller Area Network (CAN) and FlexRay. Thanks to the latest development of the Ethernet technology, a 100 Mbps Ethernet link can now be implemented and a 1 Gbps link will be available in near future. Switched Ethernet networks are of particular interest in the automotive market for supporting bandwidth-intensive applications such as backbones interconnecting various domains, infotainment and surround-view applications. Usually, Ethernet implementation in the automotive field but not limited thereto the use of unshielded twisted pair of copper wires is preferred because of weight and cost reasons. However, unshielded twisted pair cabling poses problems in meeting EMC (electromagnetic compatibility) requirements, e.g. imposed by regulatory standards.

Since more and more complex electromagnetic environment in an electronic system, electromagnetic interference (EMI) phenomenon is much worse and becomes an obvious obstacle affecting regular operation of the system. Since rapid development of high speed digital circuits, researchers are driven to pay attention to suppress noise and crosstalk of digital system. Ideally, a differential signal may maintain well original signal aspect and maintain low electromagnetic radiation or electromagnetic interference. However, in an actual circuit, unbalanced delay and amplitude, or unbalanced design of input/output register or package layout may cause the differential signal to generate different rising/falling edge time such that unwanted common mode noise attaches the differential signal. With respect to high speed data transmission interface, for instance, Gigabit Ethernet, etc., a cable is always needed to transmit the differential signals between different electronic devices. At this time, a common mode noise may be coupled to an input/output cable and is formed to be an excitation source such that the input/output cable becomes an EMI antenna.

Hence, in order to solve electromagnetic interference (EMI) problem of the input/output cable, it is advantageous to suppress or at least significantly reduce common mode noise on a differential signal route to achieve low electromagnetic emission (EME).

SUMMARY

The present invention provides a transceiver, a system and a method of detecting a common mode signal on a single twisted-pair cable (300) used for bi-directional data communication between a node and a counterpart node of a point-to-point network using differential mode signaling as described in the accompanying claims. Specific embodiments of the invention are set forth in the dependent claims. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below in detail with reference to drawings. Note that the same reference numerals are used to represent identical or equivalent elements in figures, and the description thereof will not be repeated. The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the invention. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the invention and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims.

Referring now toFIG. 1, a block diagram is schematically illustrated, which depicts an Ethernet over twisted-pair cabling link between a first link partner node and a second link partner node in accordance with an embodiment of the present invention.

The exemplary system shown inFIG. 1comprises a first link partner node10and a second link partner node20. The first link partner node10and the second link partner node20communicate via a wire-based communication medium15. In general, the wire-based communication medium15may comprise one or more shielded or unshielded twisted-pairs (STP/UTP) of copper cabling or wires, for example. The first link partner node10and the second link partner node20may communicate using one or more twisted-pair wires comprised within the communication medium15. Certain performance and/or specifications criteria for STP/UTP copper cabling have been standardized. For example, through IEEE 802.3 Working Groups 100BASE-T1 (IEEE 802.3bw) and 1000BASE-T1 (IEEE 802.3 bp) are specified. In these two standards, a 15 m channel over one unshielded twisted pair of wires is defined for use in particular in vehicles. Both standards also include the parameter definitions for a 40 m transmission channel over one shielded twisted pair of wires for the aforementioned use and/or application such as in trucks, buses, aircraft, and trains, and further in industrial applications.

The first link partner node10comprises a computer system10a, a medium access control (MAC) controller10b, and a transceiver (TX/RX PHY)100, which coupled via a hybrid10cto the wire-based communication medium15. Similarly, the second link partner node20comprises a computer system20a, a MAC controller20b, and a transceiver (TX/RX PHY)200, which coupled via a hybrid20cto the wire-based communication medium15. Notwithstanding, the invention is not limited in this regard.

The transceiver (TX/RX PHY)100may comprise suitable logic, circuitry, and/or code that may enable communication, for example, transmission of data to and reception of data from a link partner node such as the second link partner node20. Similarly, the transceiver (TX/RX PHY)200may comprise suitable logic, circuitry, and/or code that may enable communication, for example, transmission of data to and reception of data from a link partner node such as the first link partner node10. The transceivers (TX/RX PHYs)100and200may support, for example, Ethernet communications operations. The transceivers (TX/RX PHYs)100and200may enable multi-rate communications, such as 10 Mbps, 100 Mbps, 1000 Mbps (or 1 Gbps) and/or 10 Gbps, for example. In this regard, the transceivers (TX/RX PHYs)100and200may support standard-based data rates and/or non-standard data rates. Moreover, the transceivers (TX/RX PHYs)100and200may support standard Ethernet link lengths or ranges of operation and/or extended ranges of operation.

In the context of the present application a link partner node relates to any point-to-point communication link based networking device including in particular any networking Ethernet device such as a networking node, hub, switch, router and the like, which is cable of receiving and transmitting data over the point-to-point communication link.

Reduction of electromagnetic emission (EME) is a major concern in the transmission of electronic signals and data. In particular, in EMI sensitive environments such as automotive environment, reliable operation of for instance high-speed communication requires the observation of electromagnetic compatibility requirements due to the risk of EME induced malfunctions of any kind. In particular, the use of UTP cabling requires further measures.

Common mode chokes are typically used for suppression of electromagnetic interference (EMI), which is an issue on communication links using differential signaling for data communication and in particular in IEEE 802.3 based Ethernet communication links. A common mode choke consists of two independent coils with the same amount of wire loops winding the same magnet, wherein its structure equals to a winding or feed through core coil, and it may generate high conductive impedance for common mode noise and generate impedance approaching to zero for differential signal via high magnetic conductivity by summation and subtraction of self-inductance and mutual inductance.

Referring now toFIG. 2a, a further block diagram is schematically illustrated, which depicts an Ethernet over twisted-pair cabling link between a first link partner node and a second link partner node in accordance with an embodiment of the present invention. A common mode choke (CMC)120and coupling capacitors140and145are coupled between the signal input/output (I/O) of the transceiver (TX/RX PHY)100and the sockets150,155for e.g. detachably receiving a plug of the wire-based communication medium, herein a single twisted-pair cable300. Similarly, a common mode choke (CMC)220and coupling capacitors240and245are coupled between the signal input/output (I/O) of the transceiver (TX/RX PHY)200and the sockets250,255for e.g. detachable receiving a plug of the wire-based communication medium, herein a single twisted-pair cable300.

Whereas common mode chokes such as those illustrated inFIG. 2aallow for weakening common mode signals received by the transceivers (TX/RX PHYs)100,200, common mode signals on the wire-based communication medium, herein a single twisted-pair cable300may be nevertheless source of EMI for nearby arranged circuitries.

Referring now toFIG. 2b, a yet another block diagram is schematically illustrated, which depicts an Ethernet over twisted-pair cabling link between a first link partner node and a second link partner node in accordance with an embodiment of the present invention. In analogy to the above example ofFIG. 2a, the first and second link partner nodes100and200are provided with common mode chokes (CMC)120and220for suppression of common mode noise as well as coupling capacitors140,145and240,245for blocking DC signals. In addition, the single twisted-pair cable300used as wire-based communication medium between both link partner nodes is applicable and may be used for power transmission. For instance, standard IEEE 802.3bu specifies a power standard analogously to PoE (Power over Ethernet) with the name Power over Data Line (PoDL) over a single-pair Ethernet cable such as the single twisted-pair cable300.

A direct current is injected into the wires of the single twisted-pair cable300using a differential mode choke180. For instance, the direct current is injected at or near the end of the single twisted-pair cable300on side of the first communication partner node100.

The injected direct current can be drawn from the wires of the single twisted-pair cable300using again a differential mode choke280connected to the wires of the single twisted-pair cable300. For instance, the direct current is drawn at or near the end of the single twisted-pair cable300on side of the second communication partner node200. In an example, the direct current transmitted over the single twisted-pair cable300supplies the second communication partner node200with power.

A differential mode choke consists of two independent coils with the same amount of wire loops winding the same magnet. In contrast to the common mode choke, where currents are flowing in the same direction through each of the independent coils, the currents are flowing in opposite direction through each of the independent coils. The current flow direction is indicated by “dot symbols” shown at the winding symbols of the common/differential mode chokes illustrated inFIGS. 2aand 2b. Hence, a differential mode choke generates high conductive impedance for differential mode signals and common mode signals. A direct current is passed by a differential mode choke, which allows for injecting a direct current into the single twisted-pair cable300and drawn a direct current from the single twisted-pair cable300with a minimum interference of the data signaling on the single twisted-pair cable300.

The design and manufacturing of common mode chokes applicable for high frequencies are challenging. In particular, at frequencies above high frequency section of GHz because of frequency characteristic and parasitics of ferromagnetic material, and manufacturing process and complex structure of the common mode choke are difficult to match with the requirements of modern miniaturized circuits. Despite the aforementioned difficulties, well designed transceivers (TX/RX PHY), connectors and cables should meet the defined EMC requirements at design time. But, the EME requirements of the targeted application use may be unknown or only partially known to time of design, which may lead to misassumptions regarding the sufficient margin to emission requirements masks. Furthermore, EMC requirements may be nevertheless missed in different application scenarios and/or different application use because of mode conversion, which in turn may be caused by a lack of channel symmetry and/or cable impedance mismatch. Lack of channel symmetry and/or cable impedance mismatch may be attributed to cable bending, placement of cable connectors, composition of cable harness, a varying distance of the cable to ground and the like. Lack of channel symmetry and/or cable impedance may be also caused by aging effects and/or mechanical and/or thermal stresses (including inter alia vibrations), to which the cable is subjected. The aforementioned list is not exhaustive and should be understood as exemplary in order to improve the understanding of the teaching of the present application.

As the data rate enters the GHz range, crucial problems, such as mode-conversion and signal loss at the differential signal line increase significantly. There may be minimal signal distortion, delay, and skew on carefully designed differential lines. However, an unbalanced structure in the differential interconnection generates undesirable mode-conversion.

Therefore, it is imperative to how to provide further measures to deal with common mode noise, which is utilizable in individual applications during operation.

Referring now toFIGS. 3aand 3b, block diagrams are schematically illustrated, each of which depicts an Ethernet over twisted-pair cabling link between a first link partner node and a second link partner node with common mode detection in accordance with an embodiment of the present invention. In order to take measures against common mode noise on a twisted-pair cabling link for Ethernet-based communication, a detection of the common mode noise is required.

The depicted Ethernet over twisted-pair cabling link between a first link partner node and a second link partner node substantially corresponds to the example described above with reference toFIG. 2abut is further modified to allow for common mode signal detection. A repetition of the components common withFIG. 2awill be omitted in the following.

In the current example, a common mode signal detection is suggested, which makes use of the common mode chokes120and220already present. Each common mode choke120,220is provided with a respective switch arrangement130and230. Each of the switch arrangements130and230is arranged to selectively switch the common mode choke120and the common mode choke220, respectively, in either common mode signal suppression operation or differential mode signal suppression operation. The designation “common mode choke” should be understood to refer to the (conventional) functionality and operation during data communication. The switching of the common mode choke120,220into differential mode signal suppression operation is for instance obtained by switching the polarity of one coil of the common mode choke120,220. Switching the polarity means that in common mode signal suppression operation, currents flows in the same direction through each of the coils/choke windings and that in differential mode signal suppression operation, currents flows in opposite direction through each of the coils/choke windings.

In the example illustrated inFIG. 3a, the switching arrangement130is switched such that the common mode choke120is operated to suppress common mode signals with respect to the transceiver (TX/RX PHY)100and the switching arrangement230is switched such that the common mode choke220is operated to suppress differential mode signals with respect to the transceiver (TX/RX PHY)200. For instance, the switching arrangement230comprises two switches, which are simultaneously operated to swap the connections to the cable-side and transceiver-side terminals resulting in a reversal of the current flow through one of the coils of the common mode choke220. This means that the common mode choke220is hence switchably wired to pass a common mode signal present on the cable of the communication link300.

For testing the communication link300, the transceiver (TX/RX PHY)100is arranged and configured to generate and transmit a test signal on the cable of the communication link300. The test signal may be a differential mode signal. In an example, the test signal is representative of the differential mode signals transferred on the communication link300during data communication operation. The test signal may have a frequency range and/or bandwidth, which substantially corresponds to the frequency range of signals transferred on the communication link300during data communication operation. In an example, the test signal may comprise a sequence of individual test signals.

As aforementioned, the common mode choke220on side of the transceiver (TX/RX PHY)200is switchably configured to pass common mode signals only whereas differential mode signals are suppressed. Accordingly, common mode signals occurring on the cable of the communication link300due to mode conversion are detectable at the transceiver (TX/RX PHY)200, which comprises a detection section205for detecting common mode signal.

In the example illustrated inFIG. 3bsimilarly, the switching arrangement130is switched such that the common mode choke120is operated to suppress differential mode signals with respect to the transceiver (TX/RX PHY)100and the switching arrangement230is switched such that the common mode choke220is operated to suppress common mode signals with respect to the transceiver (TX/RX PHY)200. For instance, the switching arrangement130comprises two switches, which are simultaneously operated to swap the connections to the cable-side and transceiver-side terminals resulting in a reversal of the current flow through one of the coils of the common mode choke120. This means that the common mode choke220is hence switchably wired to pass a common mode signal present on the cable of the communication link300.

For testing the communication link300, the transceiver (TX/RX PHY)200is arranged and configured to generate and transmit a test signal on the cable of the communication link300.

As aforementioned, the common mode choke120on side of the transceiver (TX/RX PHY)200is switchably configured to pass common mode signals only, whereas differential mode signals are suppressed. Accordingly, common mode signals occurring on the cable of the communication link300due to mode conversion are detectable at the transceiver (TX/RX PHY)100, which comprises a detection section105for detecting common mode signal.

Those skilled in the art will appreciate from the above examples that the switching arrangements130and230are provided to enable detection of common mode signal(s) occurring on the cable of the communication link300by either one of the link partner nodes100and200in response to the test signal(s) generated and transmitted on the cable of the communication link300by the other one of the link partner nodes100and200. The switching arrangements130and230are controlled by the transceiver (TX/RX PHY) of the respective link partner node, for instance, in response to a request and/or on detection that the test signal(s) are transmitted on the cable of the communication link300.

Referring now toFIG. 3c, a block diagram is schematically illustrated, which depicts an Ethernet over twisted-pair cabling link between a first link partner node and a second link partner node with common mode detection in accordance with another embodiment of the present invention. The depicted Ethernet over twisted-pair cabling link between a first link partner node and a second link partner node substantially corresponds to the example described above with reference toFIG. 2bbut is further modified to allow for common mode signal detection. A repetition of the components common withFIG. 2bwill be omitted in the following.

The differential mode chokes180and280used for PoDL transmission may be also used for detecting a common mode signal on the cable of the communication link300. The detection of a common mode signal is performed as aforementioned but without switching the polarity of the common mode chokes120and220arranged between the respective transceiver (TX/RX PHY)100or200and the cable of the communication link300. Instead, the present differential mode chokes180and280of the PoDL circuits170and270are used, which are configured to pass direct current signals. Each one of the differential mode chokes180and280is coupled to a respective one of the detection sections105and205for detecting common mode signal, which are provided with, coupled to or implemented in the transceivers (TX/RX PHY)100and200.

For instance, the transceiver (TX/RX PHY)100transmits a test signal on the cable of the communication link300. The differential mode choke280of the PoDL circuit270is arranged and configured to pass the common mode signals present at the cable of the communication link300occurring due to mode conversion. The common mode signals present at the cable of the communication link300is detectable at the second link partner node200by the detection section205for detecting common mode signal coupled to the differential mode choke280.

Similarly, the transceiver (TX/RX PHY)200transmits a test signal on the cable of the communication link300. The differential mode choke180of the PoDL circuit170is arranged and configured to pass the common mode signals present at the cable of the communication link300occurring due to mode conversion. The common mode signals present at the cable of the communication link300is detectable at the first link partner node100by the detection section105for detecting common mode signal coupled to the differential mode choke180.

Those skilled in the art will understand from the above description that the common mode signals present on the cable of the communication link300between two link partner nodes is detected and measured using differential mode chokes, which are provided either by selectively switching the polarity of one of the coils/choke windings of a common mode choke or by a using differential mode choke of a PoDL circuit. The detection section105for detecting common mode signal may be arranged at the transceivers (TX/RX PHY)100,200of the link partner nodes such that mutual detection and measurement of common mode signals on the cable of the communication link300is possible, which occur in response to a test signal transmitted by the respective other one of the link partner nodes. The suggested methodology of detecting common mode signals on the cable of the communication link300may be performed on start-up/boot of the link partner nodes, e.g. as part of the link auto-negotiation procedure during set-up of the communication between the link partner nodes, and/or on demand e.g. in response to the detection of an increasing error rate or a worsening signal to noise ratio on an established communication connection between the link partner nodes. The suggested methodology allows for in situ detection and measurement of common mode signals on the cable of the communication link300. In particular, the use of differential mode chokes of PoDL circuits may further allow for continuous monitoring the presence of common mode signals on the cable of the communication link300.

Those skilled in the art will also understand that the differential mode chokes may be arranged at each end of the cable of the communication link300, which are not part of a PoDL system but for detection of common mode signals on the cable of the communication link300.

Referring now toFIG. 4a, a flow diagram is shown, which schematically illustrates an operation for detecting a violation of electromagnetic emission (EME) requirements on a cable of the communication link300and adjusting the communication signals generated by the two link partner nodes communicating over the communication link300according to an example of the present application. The two link partner nodes communicate data over the communication link using differential signals.

In an operation S100, an electromagnetic emission (EME) present on the cable of the communication link300between the connected link partner nodes at the end thereof is detected. In the following, the link partner nodes will be also referred to as nodes, in particular node A and node B corresponding to either one of the aforementioned first link partner node100and second link partner node200. In an example, node A corresponds to the aforementioned first link partner node100and node B corresponds to the aforementioned second link partner node200In an example, the EME includes common mode signal(s) occurring on the cable of the communication link for instance due to mode conversion.

In an operation S120, the detected EME is compared with an EME threshold. The EME threshold may be predefined. In an example, the EME threshold is an upper threshold to limit the EME.

In case the detected EME exceeds the EME threshold, the EME requirements of the communication link are violated. In this case the transmission (TX) signals are adjusted in order to minimize the detrimental effects of the detected EME to external circuities in an operation S130. In particular, the transmission (TX) signals are adjusted in order to minimize the common mode signal(s) present on the cable of the communication link thereby reducing EME. Various examples of adjusting the TX signals will be discussed with regard to embodiments of the present application. The success of the adjustment of the TX signals may be verified by returning to operation S110.

In case the detected EME does not exceed the EME threshold, the EME requirements of the communication link are met. A (further) adjustment of the TX signals is not necessary in this case. In an example, it is checked whether an adjustment of the TX signals is advisable to increase the data throughput over the communication link by making use of a margin between detected EME and the EME threshold.

Referring now toFIG. 4b, a flow diagram is shown, which schematically illustrates an operation for detecting the electromagnetic emission (EME) on the cable of the communication link300according to an embodiment of the present application. The present embodiment is based on a reporting of the detection results from one node to the other node connected to the cable of the communication link.

In an operation S101, node A transmits a request to node B, which requests the initiation of the EME test procedure. In response to the request, node B prepares for performing the EME test procedure.

In a following operation S102, node A transmits a test signal on the cable of the communication link300to node B.

In a following operation S103, node B performs a detecting of a common mode signal, which may occur in response to the transmitted test signal. Node B is prepared by the initial request for detecting the common mode signal. The detection is performed by node B as described above with reference toFIG. 3. For instance in response to the above request for preparation, node B is configured to switch the polarity of the common mode choke230as illustrated inFIG. 3aand described above with reference thereto. Alternatively, node B is configured to make use of a differential mode choke such as differential mode choke280shown inFIG. 3cand described above with reference thereto.

In a following operation S104, node B generates a report on the detection of the common mode signal and transmits the report to node A.

In a following operation S105, node A receive the report from node B. Based on the received report, node A is now capable of adjusting TX signals in order to minimize the detected EME if necessary.

Those skilled in the art immediately understand from the above description that the same or similar procedure is applicable to enable node B to be informed about the EME present on the cable of the communication link as schematically illustrated by the flow diagram and the operations S100′ to S105′. In brief, node B transmits the test signal (S101′), node A performs (S103′) a detecting of a common mode signal, which may occur in response to the transmitted test signal (for instance by switching the polarity of the common mode choke130as shown inFIG. 3bor using differential mode choke180shown inFIG. 3c), and node A generates (S104′) and transmits the report on the common mode signal detection to node B, which receives (S105′) the report and is enabled for adjusting TX signals.

Those skilled in the art will understand that the test signal referred to above is a differential mode signal and in particular an easily recognizable differential mode signal including for instance a narrow band test signal, a test signal with a predefined modulation scheme including a predefined frequency modulation (FM), pulse modulation (PM) or code sequence or a test signal with a predefined direct sequence spread spectrum (DSSS). The test signal may have other easy to recognize signal characteristic, which in particular differentiates the test signal from noise or interference signals caused by one or more external EMI sources.

Those skilled in the art will also understand that the test signal referred to above trigger the performing of detecting a common mode signal on the cable of the communication link300wherein the request transmitted from the test signal generating and transmitting node to the counterpart node (cf. operations S101and S111) may be omitted. To enable using the test signal to trigger the performing of the common mode signal detection, the test signal should be detectable distinct from data communication related signals on the cable of the communication link. A test signal detector may be part of a RX section of the transceivers of the link partner nodes, examples of which are discussed in the following.

Referring now toFIG. 5a, a block diagram of a transceiver (TX/RX PHY) of a link partner node according to an embodiment of the present application is schematically illustrated.

The transceiver (TX/RX PHY) comprises a receiving (RX) section400and a transmitting (TX) section450. The RX section comprises typically an RX analog frontend, herein schematically illustrated by an amplifier405and an analog-to-digital converter (ADC)410, and a digital processing stage, herein schematically illustrated by a digital signal processor415and a physical code sublayer component420. The digital processing stage is configured to process signals, which are received from the communication link300, for being passed to the Media Access Control (MAC) layer (not shown) via the media independent interface (MII)440. The TX section450comprises typically a digital processing stage, herein schematically illustrated by a physical code sublayer component455and a symbol modulation component460and an TX analog frontend, herein schematically illustrated by a digital-to-analog converter (DAC)465and a driver stage470. The implementation of the RX section400and TX section450is known in the art and a skilled person understands that further components may be comprised in the RX section400and TX section450.

For common mode detection, a detection section500is further comprised in the illustrated transceiver (TX/RX PHY), which includes an amplifier505, an analog-to-digital converter (ADC)510and a transform component515for transforming the digitized signal into frequency domain such as a Fast Fourier transform component515. Those skilled in the art will understand that the detection of a common mode signal on the cable of the communication link300may include further processing steps such as demodulation, decoding and de-spreading, which is typically performed on the digitized signal. Mode conversion is frequency dependent. Conventionally, there is more mode conversion at higher frequencies. The frequency transform component515allows to analyze strength of the detected common mode signal with respect to a frequency range, which is in particular predefined by the transform component.

In accordance with the operation according to the embodied flow diagram ofFIG. 4b, the results of the common mode signal detection, herein the frequency transformed version of the detected common mode signal, is reported to the counterpart node. For reporting, the detection section500comprises a TX reporting component520, which is configured to generate the report and to supply the report to the TX section450of the transceiver (TX/RX PHY) for being transmitted to the counterpart node. In the example shown inFIG. 5a, the TX reporting component520directly injects the report into the TX section450of the transceiver (TX/RX PHY).

The detection section500further comprises a test signal generator530, which is provided to supply a test signal to the TX section450of the transceiver (TX/RX PHY) and a RX reporting component525, which is configured to receive a common mode signal detection report generated by the counterpart node and to provide the detection results to a TX signal adjustment component550. In the example shown inFIG. 5a, the test signal generator530directly injects the test signal into the TX section450of the transceiver (TX/RX PHY). In the example shown inFIG. 5a, the RX reporting component525taps the received report at the RX section400of the transceiver (TX/RX PHY).

For the sake of illustration of the functionality and operation of the transceiver (TX/RX PHY) with EME detection capability, choke arrangements as described with reference toFIGS. 3ato 3care omitted in the block diagram. However, those skilled in the art understand that in particular the detection of the common mode signal requires one of the aforementioned choke arrangements and/or control thereof.

Referring now toFIG. 5b, a block diagram of a transceiver (TX/RX PHY) of a link partner node according to another embodiment of the present application is schematically illustrated.

The transceiver (TX/RX PHY) ofFIG. 5bsubstantially corresponds to the above described one but the TX reporting component520and the RX reporting component525make use of one or more higher layers such as the medium access control (MAC) layer accessible via the media independent interface440for transmitting and receiving the reports exchanged between node A and node B as described above with reference toFIG. 4b.

Whereas the detection of EME and common mode signals on the cable of the communication link has been discussed in detail in the forgoing description, the following description relates to the adaptation of the TX signal in response to the results of the detection operation.

With respect toFIGS. 6ato 6cdifferent TX signal adaptation procedures will be described in conjunction withFIGS. 7ato 7cshowing exemplary implementations in the transceiver (RX/TX PHY) enabling the different TX signal adjustment procedures.

Referring now toFIG. 6a, a flow diagram is shown, which schematically illustrates an TX signal adjustment based on signal cancellation according to an embodiment of the present application.

The signal cancellation procedure S200relates to a cancelling of the common mode signal with effect to the counterpart node, which receives data communication signals, using an inverse or cancelling signal generated at the transmitting node. The inverse or cancelling signal is generated on the basis of the detection result of a previous EME detection as described above.

In an operation S201, a frequency range of the detected common mode signal is estimated. In particular, the frequency range is estimated on the basis of the frequency transformed common mode signal. More particular, the frequency domain coefficients, which may be Fourier coefficients, obtained by frequency transform of the real space common mode signal are compared with one or more thresholds, which may be predefined. The frequency range is estimated from frequency domain coefficients exceeding the one or more thresholds.

Based on the estimated frequency range, matrix coefficients of an inverse mode conversion matrix are determined and the inverse mode conversion matrix is fed with the determined matrix coefficients in an operation S202.

In an operation S203, the inverse mode conversion matrix is operated to generate an inverse or cancelling signal and to add the generated inverse/cancelling signal to a TX signal generated at the TX section450of the transceiver (TX/RX PHY). The inverse mode conversion matrix is provided to generate the inverse/cancelling signal based on the TX signal generated by the transceiver (TX/RX PHY). The inverse/cancelling signal generated by the inverse mode conversion matrix is a common mode signal. The inverse mode conversion matrix effectively adds a deliberate (inverse) common mode signal to the output signal of the transceiver (TX/RX PHY), which is substantially in anti-phase to the detected common mode signal thereby cancelling or at least weakening the detected common mode signal.

Due to the large common mode suppression of the common mode choke at the output of the transceiver (TX/RX PHY), the inverse/cancelling signal generated by the inverse mode conversion matrix has to be strong to overcome the suppression. For example, it may be assumed that the cable of the communication link is 10% unbalanced due to some impairment. The differential mode signal has for instance 1 mVrms (=+60 dBuV) for one or more EMC relevant frequency ranges/bands (e.g. 100 MHz). The unbalance of 10% results to a common mode signal on the cable with +40 dBuV, which is out of a predefined specification (e.g. >20 dB for IEEE 802.3). A cancelling or at least weakening of the common mode signal can be expected in case of an inverse/cancelling signal with +40 dBuV in anti-phase after passing the common mode choke arranged at the output of the transceiver (TX/RX PHY). It may be assumed that the common mode choke has a +40 dB common mode signal suppression. Hence, the inverse/cancelling signal requires 10 mVrms (=+80 dBuV) at the transceiver (TX/RX PHY). This means that the inverse/cancelling signal has to be a factor of 10 stronger than the differential mode signal generated at the transceiver (TX/RX PHY) for communicating data over the cable of the communication link. A typical target for cancelling the common mode signal is a remaining common mode signal, which is smaller than −40 dB and an emission target smaller than +15 dBuV.

Referring now toFIG. 7a, a block diagram is shown, which schematically illustrates an TX signal adjustment based on the adding of an inverse/cancelling signal in the transmit path of the transmit section of a transceiver (TX/RX PHY) according to an embodiment of the present application. Those skilled in the art will immediately appreciate that the block diagram ofFIG. 7ahas been simplified to the components involved in generating and adding of the inverse/cancelling signal. The description of the aforementioned embodiments of the transceiver (TX/RX PHY) should be read into the present embodiment.

The frequency transform coefficients may be provided by the frequency transform component (e.g. the FFT component515) or the RX reporting component525to a coefficient control component605, which is arranged to estimate the frequency range, to determine the matrix coefficients for an inverse mode conversion matrix component610arranged in form of a filter in the transmit path of the transceiver (TX/RX PHY), and to configure the inverse mode conversion matrix component610with the determined matrix coefficients. An input of the inverse mode conversion matrix component610is coupled to the transmit path of the TX section450to receive the TX signal generated by the transceiver (TX/RX PHY) and an output of the inverse mode conversion matrix component610is coupled to the signal coupler, which is provided to add the inverse/cancelling signal generated by the inverse mode conversion matrix component610to the TX signal on the transmit path of the TX section450.

The inverse/cancelling signal is added to the TX signal generated by the transceiver (TX/RX PHY) upstream to the digital-to-analog converter (DAC)465and in particular directly upstream to the digital-to-analog converter (DAC)465.

Referring now toFIG. 6b, a flow diagram is shown, which schematically illustrates an TX signal adjustment based on filter according to an embodiment of the present application.

The signal cancellation procedure S210relates to a FIR filter, which is applied for frequency selective filtering the TX signal generated by the transceiver (TX/RX PHY) at the node. The filter coefficients, with which the FIR filter is configured, are generated on the basis of the detection result of a previous EME detection as described above.

In an operation S211, a frequency range of the detected common mode signal is estimated. In particular, the frequency range is estimated on the basis of the frequency transformed common mode signal. More particular, the frequency domain coefficients (Fourier coefficients) obtained by frequency transform of the real space common mode signal are compared with one or more thresholds, which may be predefined. The frequency range is estimated from frequency domain coefficients exceeding the one or more thresholds.

Based on the estimated frequency range, filter coefficients of an FIR filter are determined and the FIR filter is fed with the determined filter coefficients in an operation S202. The FIR filter is in particular a band stop FIR filter and the filter coefficients are determined to weaken the TX signal at the estimated frequency range, where the frequency domain coefficients of the detected common mode signal exceeds the one or more thresholds.

Typically, the TX signals transmitted on the cable of the communication link300have to comply with a predefined TX PSD (power spectral density) mask. The TX PSD mask may include a lower PSD mask and an upper PSD mask, which define a corridor for the strength of the TX signals. The predefined TX PSD mask is typically defined in a standard to enable interoperability of transceivers (TX/RX PHY). The fact that the signal strength should comply with predefined TX PSD (power spectral density) mask allows for using a band stop FIR filter configured on the basis of the detected common mode signal for weakening the detected common mode signal.

In an operation213, the FIR filter is operated to frequency dependent weaken the TX signal generated at the TX section450of the transceiver (TX/RX PHY).

Referring now toFIG. 7b, a block diagram is shown, which schematically illustrates an TX signal adjustment based on filtering the TX signal on the transmit path of the transmit section of a transceiver (TX/RX PHY) according to an embodiment of the present application. Those skilled in the art will immediately appreciate that the block diagram ofFIG. 7bhas been simplified to the components involved in filtering the TX signal. The description of the aforementioned embodiments of the transceiver (TX/RX PHY) should be read into the present embodiment.

The frequency transform coefficient may be provided by the frequency transform component (e.g. the FFT component515) or the RX reporting component525to a coefficient control component605, which is arranged to estimate the frequency range, to determine the filter coefficients for a FIR filter component620in the transmit path of the transceiver (TX/RX PHY), and to configure the FIR filter component620with the determined filter coefficients. An input of the FIR filter component620is coupled to the transmit path of the TX section450to receive the TX signal generated by the transceiver (TX/RX PHY) and an output of the FIR filter component620is coupled to the signal coupler, which is provided to add the filter signal generated by the FIR filter component620to the TX signal on the transmit path of the TX section450. Effectively, the FIR filter component620is configured to operate as a band stop filter and to weaken the TX signal at the estimated frequency range.

The TX signal generated by the transceiver (TX/RX PHY) is filtered by the FIR filter component620upstream to the digital-to-analog converter (DAC)465and in particular directly upstream to the digital-to-analog converter (DAC)465.

The upper and lower TX PSD masks605and610for a 1000BASE-T1 communication link and upper and lower TX PSD masks615and620for a 10GBASE-T is illustrated inFIGS. 8aand 8b, respectively. As understood from the illustrated upper and lower TX PSD mask, there is for instance a 6 dB headroom available for shaping the TX-PSD through filtering the TX signal as described above.

Referring now toFIG. 6c, a flow diagram is shown, which schematically illustrates an TX signal adjustment based on amplitude scaling according to an embodiment of the present application.

The amplitude scaling procedure S220involves a configurable pulse amplitude modulation (PAM), which is used for modulating the TX signal at the TX section450of the transceiver (TX/RX PHY). In PAM signal modulation, information is encoded in the amplitude of a series of signal pulses. For example, a two-bit modulator takes two bits and maps the signal amplitude to one of four possible voltage (amplitude) levels (perhaps 0.5 V, 1 V, 1.5 V, 2 V) over a specified symbol period. Demodulation of the signal is accomplished by detecting the amplitude level of the carrier at each symbol period. The number of discrete pulse amplitude levels are typically some power of two for digital signal communication and are referred to as PAM level or modulation complexity. Lower modulation complexity means lower PAM level and higher complexity means higher PAM level.

For instance, 4-level PAM (PAM-4) uses 4 discrete pulse amplitude levels, each of which is referred to as one of 4 symbols enabling symbol mapping of a 2 Bit sequence; 8-level PAM (PAM-8) uses 8 discrete pulse amplitude levels, each of which is referred to as one of 8 symbols enabling symbol mapping of a 3 Bit sequence; 16-level PAM (PAM-16) uses 16 discrete pulse amplitude levels, each of which is referred to as one of 16 symbols enabling symbol mapping of a 4 Bit sequence and so on. Generally, an amplitude level range comprises the discrete pulse amplitude levels. The upper limit of the amplitude level range corresponds to a predefined maximum modulation amplitude. When maintaining the maximum modulation amplitude, the step size between adjacent pulse level amplitudes is hence a function of the PAM level (or number of symbols). For instance, a PAM level is selected to ensure that the smallest pulse amplitude level is above the noise floor. In case of an increasing noise floor, while maintaining the maximum modulation amplitude a selecting of a lower PAM level, which increases the step size between consecutive pulse level amplitudes, allows for ensuring that the smallest pulse amplitude level is above the increased noise floor.FIG. 6dshows a method for selecting a modulation based on the data rate. Accordingly, at step S230, the data rate of transmission is adapted. At step S231, a modulation is selected based on adapted data rate. At step S232, a change in the modulation is reporated.

Referring now toFIG. 9, a schematic diagram illustrates discrete amplitude levels of exemplary pulse amplitude modulation schemes, namely PAM-16, PAM8and PAM4with amplitude scaling. The discrete amplitude levels of the different PAM schemes are illustrated in form of overlying bars710,715and720. PAM-16 has 16 distinct discrete amplitude levels, PAM-8 has 8 distinct discrete amplitude levels and PAM-4 has 4 distinct discrete amplitude levels. The diagram further schematically illustrates the noise floor700due to analog-to-digital conversion (including quantization noise and thermal noise) and the noise floor705due to cross-talk effects. In order to reduce the EME, an amplitude scaling is suggested, which downscales the maximum modulation amplitude dependent on the complexity of the amplitude modulation. A maximum modulation amplitude is predefined with respect to a default amplitude modulation scheme. The amplitude scaling hence applies accordingly to the discrete pulse amplitude levels comprised by the aforementioned amplitude level range.

The amplitude scaling is enabled by selecting a new amplitude modulation scheme with a smaller number of symbols, e.g. a lower PAM level. The downscaling of the maximum modulation amplitude is a function of the default amplitude modulation scheme and the new amplitude modulation scheme. In particular, the downscaling of the maximum modulation amplitude is a function of the numbers of symbols of the default amplitude modulation scheme and the new amplitude modulation scheme. For instance, the maximum modulation amplitude is downscaled by a factor corresponding to the ratio of the numbers of symbols of the default amplitude modulation scheme and the new amplitude modulation scheme. For instance, the maximum modulation amplitude may be downscaled by changing the modulation scheme from PAM-16 to PAM-8 as schematically illustrated inFIG. 9. The ratio of the PAM levels (or ratio of numbers of symbols) is equal to 2. The new maximum amplitude is half (½) of the predefined maximum modulation amplitude of the default amplitude modulation scheme. The downscaling factor is equal to the ratio of the PAM levels. The downscaling factor provides for the same step size between consecutive pulse level amplitudes in case of the PAM-16 scheme to PAM-8 scheme. In another example, the maximum modulation amplitude may be downscaled by changing the modulation scheme from PAM-16 to PAM-4. In this example, the ratio of the PAM levels (or ratio of numbers of symbols) is equal to 4, in accordance with which the maximum modulation amplitude is accordingly downscaled. The new maximum amplitude is half (¼) of the predefined maximum modulation amplitude of the default amplitude modulation scheme.

Although, PAM scheme with power of two levels are schematically illustrated inFIG. 9and described above with reference toFIG. 9, a skilled person will understand from the above description, that modulation schemes may be likewise applied, which comprise any numbers of discrete pulse amplitude levels and in particular non power of two numbers. For instance, the modulation scheme may be changed from PAM-16 (enabling to code 16 different symbols) to PAM-15 (enabling to code 15 different symbols). In this example, the downscaling factor for downscaling the maximum modulation amplitude is 16/15. The new maximum modulation amplitude is 15/16 of the predefined maximum modulation amplitude of the default amplitude modulation scheme (PAM-16). For instance, the modulation scheme may be changed from PAM-16 (enabling to code 16 different symbols) to PAM-10 (enabling to code 10 different symbols). In this example, the downscaling factor for downscaling the maximum modulation amplitude is 8/5. The new maximum modulation amplitude is 5/8 of the predefined maximum modulation amplitude of the default amplitude modulation scheme (PAM-16).

In an operation S221, a new modulation scheme is selected. A set of predefined modulation schemes may be provided. The selecting a new modulation scheme includes selecting a new modulation scheme from the set of predefined modulation schemes. In an example, the set of predefined modulation schemes comprises a set of PAM modulation schemes, each of which having a different PAM level. In order to reduce the maximum modulation amplitude, a PAM scheme with lower complexity is selected.

In an operation S222, the peak-to-peak voltage Vpp of the TX signal is adjusted in accordance with a new maximum modulation amplitude, which dependent on the selected new modulation scheme. In an example, the peak-to-peak voltage Vpp of the TX signal is adjusted to have a maximum according to the new maximum modulation amplitude. The new maximum modulation amplitude is based on the relationship of the modulation levels (the number of discrete levels for distinct modulation symbols) of selected new scheme. In an example, the new maximum modulation amplitude is based on a current maximum modulation amplitude and a downscale factor, which corresponds to the ratio of the levels of the current modulation scheme and levels of the new modulation scheme.

In an operation S223, the selected new modulation scheme is for instance reported to the higher layers, including in particular the MAC layer via the MII440, and the counterpart node.

Referring now toFIG. 7c, a block diagram is shown, which schematically illustrates an TX signal adjustment based on scaling the amplitude of the TX signal on the transmit path of the transmit section of a transceiver (TX/RX PHY) according to an embodiment of the present application. Those skilled in the art will immediately appreciate that the block diagram ofFIG. 7chas been simplified to the components involved in scaling of the amplitude of the TX signal. The description of the aforementioned embodiments of the transceiver (TX/RX PHY) should be read into the present embodiment.

The frequency transform coefficient may be provided by the frequency transform component (e.g. the FFT component515) or the RX reporting component525to a modulation control component630, which in response to a detected violation of the EME requirements, configures the symbol modulation component460to apply a less complex modulation scheme, which allows to downscale the maximum modulation amplitude for the analog TX signal output by the transmitter section450of the transceiver (TX/RX PHY). As described above, the modulation control component630may control the symbol modulation component460to apply a PAM modulation with lower PAM level (preferably being some power of two level). The downscaling of the maximum modulation amplitude is for instance enabled by a Vpp scaling component635, which receive an indication of the maximum modulation amplitude and which control the digital-to-analog converter (DAC)465accordingly, which converts the digital stream of symbols output by the symbol modulation component460into an analog signal. In an example, the digital-to-analog converter (DAC)465has a configurable output range, which is configured by the Vpp scaling component635coupled thereto.

The exemplary transceiver (TX/RX PHY) may further comprise a rate requesting component645, which is configured to inform higher layers (such as the MAC layer) about the change of data rate due to the selected symbol modulation scheme, and/or a header component640, which is arranged to generate a message for transmittal to the counterpart node informing the counterpart node about the selected modulation scheme for enabling the counterpart node to decode following data communication being modulated according to the selected new modulation scheme. The header component640is arranged to supply the generated message to the transmit path TX of the TX section450. In an example, the header component640is coupled to and arranged to inject the generated message into the transmit path TX of the TX section450.

The exemplary transceiver (TX/RX PHY) may further comprise a modulation report component650, which is configured to receive a request informing about a modulation scheme used by the counterpart node for data communication. On receiving such a request, the modulation report component650is arranged to configure the RX section400in accordance with the reported modulation scheme. Accordingly, the RX section400is enabled to receive following data communication modulated in accordance with the reported modulation scheme.

The modulation report component650may be further configured to receive a request requesting the node to use a new modulation scheme (and new data rate) for data transmission. The modulation report component650is coupled to the modulation control component630and reports the requested modulation scheme (and data rate) to the modulation control component630, which accordingly controls the symbol modulation of the TX section450.

Referring now toFIGS. 10aand 10b, schematic flow diagrams are illustrated, which relate to exemplary handshaking procedures for changing the modulation scheme used for data communication over a communication link between link partner nodes according to embodiments of the present application. The schematic flow diagrams illustrated inFIGS. 10aand 10brelate to example scenarios, which differ in the EME violation detection sequence in advance of the handshaking procedure for changing the modulation scheme.

Referring first toFIG. 10a, a EME violation is detected by for instance node A in an operation S400. In an example, the EME violation relates to a common mode signal(s) occurring on the cable of the communication link for instance due to mode conversion. In response to the detected EME violation, node A sends a request to node B requesting for checking the EME. Node B receiving the request performs an EME detection for verifying whether nor not an EME violation is also present at node B in an operation S410. In a request response node B informs node A about the results of the EME detection. The result may comprise an indication whether or not node B has detected an EME violation. An example of detecting an EME violation on the communication link has been described above with reference toFIG. 4. On confirmation that node B has detected an EME violation, a handshake procedure to change the modulation is initiated by node A.

The EME violation detection may be performed at the transceivers (TX/RX PHY) of the nodes A and B. Higher layer functionalities such as MAC layer functionalities may not be involved in EME violation detection as exemplified above with reference toFIG. 5in conjunction withFIG. 4.

In response to the confirmation of EME violation detected at both nodes A and B communication with each other over the communication link, a request is generated at the transceiver (TX/RX PHY) of node A and transmitted to the MAC (Media Access Control) of node A via the MII for requesting an adjusting of the data rate, which corresponds to a new modulation scheme. The request is for instance generated by rate requesting component645described above with reference toFIG. 7cin conjunction withFIG. 6c.

On receiving an acknowledgment from the MAC of node A indicating that the requested data rate is adopted by the high layers of node A in an operation S430, a message for transmittal to node B is generated in an operation S440. The message informs node B about the new modulation scheme and the new data rate, for enabling node B to decode following data communication. The message further requests the node B to also change to the new modulation scheme and the new data rate. The message is for instance generated by the header component640described above with reference toFIG. 7cin conjunction withFIG. 6c.

The message is transmitted by the transceiver (TX/RX PHY) of node A to node B, where the message is received and the RX section of node B is configured according to the new modulation scheme used by the transceiver (TX/RX PHY) of node A. Further the TX section of the node B is further configured to likewise use the new modulation scheme, where the symbol modulation is accordingly configured.

On receiving an acknowledgment from the MAC of node B indicating that the requested data rate is adopted by the high layers of node B in an operation S450in response to a request generated at the transceiver (TX/RX PHY) of node B and transmitted to the MAC (Media Access Control) of node B via the MII for requesting an adjusting of the data rate, which corresponds to the new modulation scheme, the new modulation scheme is configured at the transceiver (TX/RX PHY) of node B. The changing of the modulation scheme at node B is for instance controlled by the modulation report component650, the modulation control component630and the rate requesting component645described above with reference toFIG. 7cin conjunction withFIG. 6c.

An acknowledgement may be further transmitted by the node B and in particular the transceiver (TX/RX PHY) of node B to the node A. In response to the acknowledgement received at the transceiver (TX/RX PHY) of node A, the RX section of the RX section of node B is configured according to the new modulation scheme used by the transceiver (TX/RX PHY) of node B. The acknowledgement may be further passed to higher layers of the node A including in particular the MAC layer of node A for informing about the new data rate of the data communication transmitted by node B.

Referring next toFIG. 10b, a EME violation is detected by for instance node B in an operation S450. In response to the detected EME violation, node B sends a report request to node A reporting the detected EME violation and requesting for checking the EME. Node A receiving the request performs an EME detection for verifying whether nor not an EME violation is also present at node A in an operation S460. An example of detecting an EME violation on the communication link has been described above with reference toFIG. 4.

On confirmation that node A has also detected an EME violation, a handshake procedure to change the modulation is initiated by node A. The handshake procedure for changing the modulation corresponds to the handshake procedure described above with reference toFIG. 10a. A repetition is omitted.

For the above description, it is immediately apparent to those skilled in the art that the change of modulation procedure may be applied to maintain the data communication over the communication link in case of a disturbed data communication over the communication link by reducing the data rate in conjunction with relaxed EME requirements to be met.

Above, the detection of EME including the technical implementations enabling the EME detection as well as measures to at least reduce the detected EME violating EME requirements have been discussed. Although the measures to at least reduce the detected EME violating EME requirements have been discussed separately, those skilled in the art appreciate from the above description that one or more of them may be combined in more complex control loops. An example of such a complex control loop is shown inFIG. 11, which schematically illustrates a flow diagram of a method to reduce the EME on a cable of a communication link between nodes A and B.

In an operation S302, the electromagnetic emission (EME) present on the cable of the communication link between the two connected nodes is detected. In an example, the EME includes common mode signal(s) occurring on the cable of the communication link for instance due to mode conversion. The EME detection is described above in more detail with reference toFIGS. 4ato4c.

In an operation S304, the detected EME is compared with an EME threshold. The EME threshold may be predefined.

In case of a violation of the EME threshold, the operational sequence branches to an operation S306. Otherwise, the operational sequence branches to an operation S314.

In an operation S306, i.e. in response to a detected violation of the EME requirements, a filtering of the TX signal is performed. The filtering of the TX signal is described above in more details with reference toFIGS. 6band7b.

In next operations S308and S310, the electromagnetic emission (EME) present on the cable of the communication link between the two connected nodes is detected and the detected EME is compared with the EME threshold. The repeated EME detection allows to check the effect/efficiency of the TX signal filtering configured in the above operation S306.

In case of a violation of the EME threshold, the operational sequence branches to an operation S312. Otherwise, the operational sequence branches to an operation S314.

In an operation S312, the amplitude of the TX signal is adapted to a lower maximum peak-to-peak voltage Vpp in accordance with a downscaled maximum modulation amplitude in order to further reduce the detected EME still violating the EME requirements. The adapting of the TX signal amplitude is described above in more details with reference toFIGS. 6cand 7c. The operational sequence continues with the operation S308, in which the EME detection is again repeated.

In an operation S314, the BER margin is estimated. The BER margin results from an estimated bit error rate (BER) of the data communication over the communication link and a BER target, which may be a predefined BER target. The BER margin may be the difference between the BER of the data communication over the communication link and the BER target.

In an operation S316, the estimated BER margin is compared with the BER margin threshold, which may be predefined. In case the estimated BER margin exceeds the BER margin threshold, the sequence ends. Otherwise, in case there is a sufficient BER margin (the estimated BER margin is below the BER margin threshold), the operational sequence continues with an operation S318.

In the operation S318, a signal-to-noise ratio (SNR) margin is estimated. The SNR margin results from an estimated signal-to-noise ratio (SNR) of the data communication over the data communication over the communication link and a SNR target, which may be a predefined SNR target. The SNR margin may be the difference between the SNR of the data communication over the communication link and the SNR target.

In an operation S320, the estimated SNR margin is compared with the SNR margin threshold, which may be predefined. In case the estimated SNR margin is below the SNR margin threshold, the sequence ends. Otherwise, in case there is a sufficient SNR margin (the estimated SNR margin exceeds the SNR margin threshold), the operational sequence continues with an operation S322.

In the operation S322, it is further checked whether an EME margin, which is based on the detected EME and a EME target, exceeds a EME threshold. The EME target and/or the EME threshold may be predefined. If the EME margin exceeds the EME threshold, it is assumed that the signal quality (determined on the basis of the checks of the estimated BER margin, the estimated SNR margin and EME margin) on the cable of the communication link is good enough for increasing the data communication rate.

In an operation S324, the amplitude of the TX signal is adapted/scaled up to a higher maximum peak-to-peak voltage Vpp in order to increase the data communication rate by selecting a new modulation with higher complexity. The operational sequence return to operation S302.

Although not explicitly described above with respect to theFIGS. 6cand 7c, those skilled in the art understand that the suggested procedure and components for adapting the amplitude of the TX signal is likewise applicable to downscale the maximum modulation amplitude (and the maximum peak-to-peak voltage Vpp) of the TX signal as well as to upscale the maximum modulation amplitude (and the maximum peak-to-peak voltage Vpp) of the TX signal by selecting modulation scheme with either lower or higher complexity. In an example, lower complexity means lower PAM level and lower data rate and higher complexity means higher PAM level and higher data rate.

According to an embodiment, a transceiver is provided, which is arranged for bi-directional data communication of a node with a counterpart node connected to a point-to-point network using differential mode signaling over a single twisted-pair cable. The transceiver, TX/RX PHY, comprises a common mode choke, a switching arrangement and a detection section. The common mode choke is arranged between of the TX/RX PHY and the single twisted-pair cable and provided for common mode current suppression. The switching arrangement is further arranged between the TX/RX PHY, the common mode choke and the single twisted-pair cable and configured to switchably change a polarity of one of the windings of the common mode choke. The detection section is coupled via the switching arrangement to the common mode choke and configured to detect a common mode signal on the single twisted-pair cable in response to a transmission of a test signal by the counterpart node. For detecting the common mode signal, the switching arrangement is operated to change the polarity of the one winding of the choke such that the common mode choke operates functionally as differential mode choke. For bi-directional data communication, the switching arrangement is operated to maintain the original polarity of the one winding such that the common mode choke operates functionally as common mode choke.

According to an example, the detection section further comprises an amplifier coupled to the common mode choke and configured to amplify a common mode signal present on the single twisted-pair cable; an analog-to-digital converter coupled to the amplifier and configured to sample the common mode signal; and a frequency transform component coupled to the analog-to-digital converter and configured to frequency transform the sampled common mode signal output by the analog-to-digital converter.

According to an example, the detection section further comprises a TX reporting component configured to generate a report relating to the detected common mode signal. The generated report is for transmittal to the counterpart node.

According to an example, the TX reporting component is further configured to inject the generated report into a TX path of the TX/RX PHY; and/or to supply the generated report via a media independent interface, MII, to a media access layer, MAC, of the node for transmittal to the counterpart node.

According to an example, the detection section further comprises a test signal generator configured to generate a test signal for asserting on the single twisted-pair cable, to which the counterpart node is connected. The test signal generator is coupled to a TX path of the TX/RX and configured to inject the test signal into the TX path.

According to an example, the test signal is a differential mode test signal.

According to an embodiment, a system is provided, which comprises a transceiver, TX/RX PHY, and a differential mode choke. The TX/RX PHY is arranged for bi-directional data communication of a node with a counterpart node connected to a point-to-point network using differential mode signaling over a single twisted-pair cable. The TX/RX PHY has a common mode choke and a detection section. The common mode choke is arranged between of the TX/RX PHY and the single twisted-pair cable and is provided for common mode current suppression. The differential mode choke is arranged between the TX/RX PHY and the single twisted-pair cable and in parallel to the common mode choke and provided for differential mode current suppression. The detection section is coupled to the differential mode choke and configured to detect a common mode signal on the single twisted-pair cable in response to a transmission of a test signal by the counterpart node.

According to an example, the detection section further comprises an amplifier coupled to the common mode choke and configured to amplify a common mode signal present on the single twisted-pair cable; an analog-to-digital converter coupled to the amplifier and configured to sample the common mode signal; and a frequency transform component coupled to the analog-to-digital converter and configured to frequency transform the sampled common mode signal output by the analog-to-digital converter.

According to an example, the detection section further comprises a TX reporting component configured to generate a report relating to the detected common mode signal. The generated report is for transmittal to the counterpart node.

According to an example, the TX reporting component is further configured to inject the generated report into a TX path of the TX/RX PHY; and/or to supply the generated report via a media independent interface, MII, to a media access layer, MAC, of the node for transmittal to the counterpart node.

According to an example, the detection section further comprises a test signal generator configured to generate a test signal for asserting on the single twisted-pair cable, to which the counterpart node is connected. The test signal generator is coupled to a TX path of the TX/RX and configured to inject the test signal into the TX path.

According to an example, the test signal is a differential mode test signal.

According to an embodiment, a method of detecting a common mode signal on a single twisted-pair cable used for bi-directional data communication between a node and a counterpart node of a point-to-point network using differential mode signaling is provided. A choke is operated in differential mode current suppression. The choke is connected to the single twisted-pair cable. A test signal is asserted on the single twisted-pair cable. A common mode signal is detected on the single twisted-pair cable occurring in response to the assertion of a test signal by the counterpart node using a detection section of a transmitter, TX/RX PHY, of the node.

According to an example, the choke is a common mode choke. A polarity of one of the windings of the common mode choke is swichably changed to operate the choke in differential mode current suppression.

According to an example, the choke is a differential mode choke, which is arranged in parallel to a common mode choke. The common mode choke and the differential mode choke are coupled to the single twisted-pair cable. The differential mode choke and the detection section are used for detecting the common mode signal on the single twisted-pair cable.