Method and measuring apparatus for measuring noise of device under test

1. Field of the Invention

The present invention is related to measurement of noise, and more particularly, to a method and a measuring apparatus for measuring noise of a device under test (DUT).

2. Description of the Prior Art

When an Ethernet transceiver transmits data to an external device through a digital-to-analog converter (DAC), a portion of noise on the data may be reflected from a cable. When measuring such noise, a related art method may stop data transmission at the other side of the cable (so that the Ethernet transceiver does not receive the signal from the other side of the cable) to ensure that the detected noise only includes the reflected noise mentioned above, rather than mixing additional signals (e.g., the signal or noise from the other side of the cable).

When the other side of the cable (e.g., a link partner device connected to the Ethernet transceiver under test via the cable) sends data to the Ethernet transceiver under test, the loading on an output terminal of the Ethernet transceiver may change, thereby impacting an amount of the reflected noise. Using the measuring method of the related art, in practice, the amount of reflected noise cannot be precisely estimated.

Thus, there is a need for a novel method and an associated measuring apparatus that can solve the problem of the related art without introducing any side effect or in a way that is less likely to introduce side effects.

An objective of the present invention is to provide a method and a measuring apparatus for measuring noise of a device under test (DUT), to solve the problem of the related art.

At least one embodiment of the present invention provides a method for measuring noise of a DUT, wherein the DUT is connected to a link partner (LP) device via a cable. The method may comprise: controlling a pseudo noise generator of the LP device to generate a far-end data sequence according to transmission data, and transmitting the far-end data sequence to the DUT via the cable; controlling a pseudo noise descrambler of the DUT to recover the transmission data according to the far-end data sequence received by the DUT, to allow a pseudo noise generator of the DUT to generate an aided-data sequence according to the transmission data, wherein the aided-data sequence is configured to perform cancellation with the far-end data sequence received by the DUT to generate a cancellation result; under a condition where the LP device transmits the far-end data sequence to the DUT and the DUT substantially transmits no data to the LP device, obtaining a first noise value according to the cancellation result; under a condition where the LP device transmits the far-end data sequence to the DUT and the DUT utilizes at least one circuit therein to transmit the aided-data sequence to the LP device at the same time, obtaining a second noise value according to the cancellation result; and calculating a difference between the first noise value and the second noise value, to estimate noise from the at least one circuit.

At least one embodiment of the present invention provides a measuring apparatus for measuring noise of a DUT, wherein the DUT is connected to a LP device via a cable, and the measuring apparatus is coupled to the DUT and the LP device. The measuring apparatus may comprise a storage circuit and a processing circuit. The storage circuit is configured to store a program code. The processing circuit is coupled to the storage circuit, and is configured to control the measuring apparatus according to the program code to transmit control signals to the DUT and the LP device. The measuring apparatus controls a pseudo noise generator of the LP device to generate a far-end data sequence according to transmission data, and transmits the far-end data sequence to the DUT via the cable; the measuring apparatus controls a pseudo noise descrambler of the DUT to recover the transmission data according to the far-end data sequence received by the DUT, to allow a pseudo noise generator of the DUT to generate an aided-data sequence according to the transmission data, wherein the aided-data sequence is configured to perform cancellation with the far-end data sequence received by the DUT to generate a cancellation result; under a condition where the LP device transmits the far-end data sequence to the DUT and the DUT substantially transmits no data to the LP device, the measuring apparatus obtains a first noise value according to the cancellation result; under a condition where the LP device transmits the far-end data sequence to the DUT and the DUT utilizes at least one circuit therein to transmit the aided-data sequence to the LP device at the same time, the measuring apparatus obtains a second noise value according to the cancellation result; and the measuring apparatus calculates a difference between the first noise value and the second noise value, to estimate noise from the at least one circuit.

The method and measuring apparatus provided by the embodiments of the present invention can obtain data and noise from the LP device first when operations of a transmitting (TX) terminal of the DUT have not started yet, and then obtain a measurement result after the operations of the TX terminal of the DUT start, in order to precisely know the amount of noise being reflected when the TX terminal of the DUT is transmitting data.

These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

FIG. 1 is a diagram illustrating a transceiver being connected to a link partner (LP) device via a cable according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a measuring apparatus for measuring noise of a device under test (DUT) such as the transceiver shown in FIG. 1 according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating some configurations of the transceiver shown in FIG. 1 in a measuring flow according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating some configurations of the transceiver shown in FIG. 1 in a measuring flow according to an embodiment of the present invention.

FIG. 5 is a diagram illustrating some configurations of the transceiver shown in FIG. 1 in a measuring flow according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating a working flow of a method for measuring noise of a DUT according to an embodiment of the present invention.

FIG. 7 is an example of the working flow shown in FIG. 6 according to an embodiment of the present invention.

FIG. 1 is a diagram illustrating a transceiver 10 (e.g., an Ethernet transceiver) being connected to a link partner (LP) device 50 via a cable 20 according to an embodiment of the present invention, where the transceiver 10 is connected to the cable 20 via a connecting port 100 therein, and the LP device 50 is connected to the cable 20 via a connecting port 500 therein. As shown in FIG. 1 , the transceiver 10 may include, but is not limited to: a digital-to-analog converter (DAC) 110 , an analog front-end (AFE) circuit 120 , an analog-to-digital converter (ADC) 130 , an adder 140 , an equalizer 150 , a slicer 160 (e.g., a parser), a pseudo noise descrambler 170 , an echo canceller 180 , a pseudo noise generator 190 M (e.g., a master pseudo noise generator) and a pseudo noise generator 190 S (e.g., a slave pseudo noise generator). It is noted that the transceiver 10 may have an identical architecture to the LP device 50 (e.g., the LP device 50 may be an Ethernet transceiver having the same architecture), and the LP device 50 may also comprise the components mentioned above such as a DAC 510 , an ADC 520 and a pseudo noise generator 590 M (e.g., a master pseudo noise generator). Other components of the LP device 50 do not affect overall operations of the following embodiments, and are therefore omitted in figures for brevity.

Under a condition where both the transceiver 10 and the LP device 50 follow the Ethernet specification, one of the transceiver 10 and the LP device 50 may be set in a master mode, and the other may be set in a slave mode. For example, when the LP device 50 is set in the master mode and the transceiver 10 is set in the slave mode, where the transceiver 10 may utilize the pseudo noise generator 190 S (e.g., the slave pseudo noise generator therein) to output a data sequence carrying data to be transmitted to the LP device 50 to the DAC 110 , and the DAC 110 may convert this data sequence from a digital format into an analog format for being transmitted on the cable 20 . In another example, when the LP device 50 is set in the slave mode and the transceiver 10 is set in the master mode, where the transceiver 10 may utilize the pseudo noise generator 190 M (e.g., the master pseudo noise generator therein) to output a data sequence carrying data to be transmitted to the LP device 50 to the DAC 110 , and the DAC 110 may convert this data sequence from the digital format into the analog format for being transmitted on the cable 20 . For brevity, this embodiment and subsequent embodiments merely describe the condition where the LP device 50 is set in the master mode and the transceiver 10 is set in the slave mode, and related details of the condition where the LP device 50 is set in the slave mode and the transceiver 10 is set in the master mode may be deduced by analogy.

In this embodiment, the LP device 50 may utilize the pseudo noise generator 590 M (e.g., the master pseudo noise generator therein) may output a data sequence carrying the data to be transmitted to the transceiver 10 to the DAC 510 , and the DAC 510 may convert this data sequence from the digital format into the analog format in order to generate an analog signal that is able to be transmitted via the cable 20 . When the transceiver 10 receives the analog signal, the AFE circuit 120 may perform processing upon the analog signal (e.g., perform filtering through a filter therein and/or perform signal amplification through a programmable gain amplifier (PGA) therein) to generate a processed analog signal, and the ADC 130 may convert the processed analog signal from the analog format into the digital format, for obtaining a received data sequence.

In some embodiments, at the same time of the transceiver 10 receiving signals from the LP device 50 , the transceiver 10 transmits signals to the LP device 50 , and a portion of the signals that the transceiver 10 transmits to the LP device 50 may be reflected from the cable 20 and may be received by the AFE circuit 120 . Thus, the echo canceller 180 may generate a cancellation sequence according to a data sequence to be transmitted to the LP device 50 . The adder 140 may add the cancellation sequence to the received data sequence to remove data components from the received data sequence caused by the transmitted signal reflected by the cable 20 for generating a cancelled data sequence. Inter-symbol interference may occur during the process of data transmission, which may result in states or waveforms of the received data sequence being unstable; accurate values thereof are hard to be determined or interpreted. For example, assume that the cancelled data sequence is expected to express a logic value “1” representing+9 volts (V) and express a logic value “0” representing −9 V, but a voltage level of the cancelled data sequence at a certain time point keeps varying between +9 V and −9V. This makes it hard to determine whether the voltage level of the cancelled data sequence at this certain time point is +9 V or −9V. Thus, the equalizer 150 may perform equalization processing upon the cancelled data sequence, in order to eliminate or reduce signal jittering or drifting caused by these inter-symbol interferences to thereby correctly determine the values of the cancelled data sequence. Then, the slicer 160 may transmit the determined result to the pseudo noise descrambler 170 for recovering the data transmitted by the LP device 50 . Those skilled in this art should understand further detailed implementations of respective components of the transceiver 10 under the Ethernet specification according to FIG. 1 and the above descriptions; these further detailed implementations are omitted here for brevity.

FIG. 2 is a diagram illustrating a measuring apparatus 30 for measuring noise of a device under test (DUT) such as the transceiver 10 according to an embodiment of the present invention, where the measuring apparatus 30 may be coupled to the transceiver 10 and the LP device 50 . The measuring apparatus 30 may comprise a storage circuit 30 S, and a processing circuit 30 P coupled to the storage circuit 30 S, where the storage circuit 30 S may be configured to store a program code 30 C, and the processing circuit 30 P may be configured to control the measuring apparatus to transmit control signals to the transceiver 10 and the LP device 50 according to the program code 30 C.

In FIGS. 3-5 , components and signal paths depicted in solid lines are enabled, and components and signal paths depicted in dashed lines are disabled.

In the embodiment of FIG. 3 , the measuring apparatus 30 may control the transceiver 10 and the LP device 50 to operate in a first training phase TP 1 , wherein when operating in the first training phase TP 1 , the measuring apparatus 30 may control a device operating in the master mode to transmit data to a device operating in the slave mode, and prevent the device operating in the slave mode from transmitting any data to the device operating in the master mode. Initially, the measuring apparatus 30 may control the pseudo noise generator 590 M of the LP device 50 to generate a far-end data sequence according to transmission data TXdata, and transmit the far-end data sequence to the transceiver 10 via the cable 20 . As shown in FIG. 3 , the far-end data sequence may be transmitted through a path formed by the DAC 510 , the connecting port 500 , the cable 20 , the connecting port 100 , the AFE circuit 120 and the ADC 130 , to make the adder 140 obtain the far-end data sequence received by the transceiver 10 (referred to as “the received far-end data sequence” for brevity), where the echo canceller 180 is disabled at this moment, and the adder 140 therefore directly transmits the received far-end data sequence to the equalizer 150 . Then, the measuring apparatus 30 may control the pseudo noise descrambler 170 of the transceiver 10 to recover the transmission data TXdata according to the received far-end data sequence. In particular, the measuring apparatus 30 may control the equalizer 150 of the transceiver 10 to perform equalization processing upon the received far-end data sequence to generate an equalized far-end data sequence, and control the slicer 160 of the transceiver 10 to obtain a recovered far-end data sequence according to the equalized far-end data sequence, to allow the pseudo noise descrambler 170 to recover the transmission data TXdata according to the recovered far-end data sequence. As the pseudo noise descrambler 170 is able to recover the transmission data TXdata, the pseudo noise generator 190 M of the transceiver 10 may generate an aided-data sequence (labeled “Aided-data” in figures for brevity) according to the transmission data TXdata.

In the embodiment of FIG. 4 , the measuring apparatus 30 may control the transceiver 10 and the LP device 10 to keep operating in the first training phase TP 1 . It is noted that, after the transmission data TX data is recovered, the pseudo noise descrambler 170 may be disabled, and the echo canceller 180 may be enabled. In addition, the pseudo noise generator 190 M of the transceiver 10 may have the same architecture as the pseudo noise generator 590 M of the LP device, so the pseudo noise generator 190 M may generate the same data sequence according to the same transmission data TXdata (e.g., the aided-data sequence generated by the pseudo noise generator 190 M may be substantially equal to the far-end data sequence generated by the pseudo noise generator 590 M). Based on the above features, the aided-data sequence may be configured to perform cancellation with the received far-end data sequence to generate a cancellation result. It should be noted that the echo canceller 180 is enabled under a condition where a signal-to-noise ratio (SNR) of the equalized far-end data sequence exceeds a first predetermined threshold SNR_eye_open, to make the cancellation result be generated. As the transceiver 10 and the LP device 50 operate in the first training phase TP 1 (e.g., the LP device 50 is set in the master mode and the transceiver 10 is set in the slave mode), the measuring apparatus 30 may obtain a first noise value P 1 according to the cancellation result under a condition where the LP device 50 transmits the far-end data sequence to the transceiver 10 and the transceiver 10 does not transmit any data to the LP device 50 . The transceiver 10 prevents the cancellation result from performing the equalization processing by bypassing the equalizer 150 (labeled “EQ=1” in FIG. 4 for better comprehension), to make the cancellation result be directly transmitted to the slicer 160 for calculating the first noise value P 1 . Thus, the first noise value P 1 may represent a sum of noise provided by the LP device 50 (which may be referred to as a power value P(noise_far) of far-end noise noise_far) and noise provided by a transmission path of the far-end data sequence (which may be referred to as a power value P(noise_rx) of transmission noise noise_rx). It is noted that calculation of the first noise value P 1 is performed under a condition where a SNR of the cancellation result exceeds a second predetermined threshold SNR_EC_done.

In the embodiment of FIG. 5 , the measuring apparatus 30 may control the transceiver 10 and the LP device 50 to operate in a second training phase TP 2 , wherein when operating in the second training phase TP 2 , the measuring apparatus 30 may control a device operating in the master mode to transmit data to a device operating in the slave mode and control the device operating in the slave mode to transmit data to the device operating in the master mode at a same time. As shown in FIG. 5 , the DAC 110 may be enabled. Although the transceiver 10 is set in the slave mode, the DAC 110 obtains the aided-data sequence from the pseudo noise generator 190 M, which is different from a typical operation defined in the Ethernet specification. Accordingly, the data sequence transmitted to the LP device 50 by the transceiver 10 is the same as the data sequence transmitted by the LP device 50 , which enables better measurement of the noise. As the transceiver 10 and the LP device 50 operate in the second training phase TP 2 (e.g., the LP device 50 is set in the master mode and the transceiver 10 is set in the slave mode), the measuring apparatus 30 may obtain a second noise value P 2 according to the cancellation result under a condition where the LP device 50 transmit the far-end data sequence to the transceiver 10 and the transceiver 10 utilizes at least one circuit therein (e.g., the DAC 110 ) to transmit the aided-data sequence to the LP device 50 at a same time. The transceiver 10 prevents the cancellation result from performing the equalization processing by bypassing the equalizer 150 (labeled “EQ=1” in FIG. 5 for better comprehension), to make the cancellation result be directly transmitted to the slicer 160 for calculating the second noise value P 2 . Thus, the second noise value P 2 may represent a sum of the noise provided by the LP device (which may be referred to as the power value P(noise_far) of the far-end noise noise_far), the noise provided by the transmission path of the far-end data sequence (which may be referred to as the power value P(noise_rx) of the transmission noise noise_rx), and noise being reflected when transmitting the aided-data sequence to the cable 20 via the DAC 110 (which may be referred to as a power value P(noise_near) of near-end noise noise_near).

After the first noise value P 1 and the second noise value P 2 are obtained, the measuring apparatus 30 may calculate a difference between the first noise value P 1 and the second noise value P 2 , in order to estimate the noise from noise of the at least one circuit (e.g., the noise which is reflected when the aided-data sequence is transmitted to the cable via the DAC 110 mentioned above, such as the near-end noise noise_near). The near-end noise P(noise_near) obtained based on the method mentioned above is measured under a condition where the other side of the cable is transmitting signals, which is therefore more similar to the real case. Thus, the problem of the related art can be solved.

FIG. 6 is a diagram illustrating a working flow of a method for measuring noise of a DUT according to an embodiment of the present invention, where the DUT may be connected to a LP device (e.g., the LP device 50 ) via a cable (e.g., the cable 20 ). The working flow of this embodiment is applicable to the measuring apparatus 30 shown in FIG. 2 , and the transceiver 10 shown in FIG. 3 to FIG. 5 may be examples of the DUT. It is noted that one or more steps may be added, modified or deleted in the working flow shown in FIG. 6 if an overall result is not hindered, and these steps do not have to be executed in the exact order shown in FIG. 6 .

In Step S 610 , the measuring apparatus 30 may control a pseudo noise generator of the LP device to generate a far-end data sequence according to transmission data, and transmit the far-end data sequence to the DUT via the cable.

In Step S 620 , the measuring apparatus 30 may control a pseudo noise descrambler of the DUT to recover the transmission data according to the far-end data sequence received by the DUT, to allow a pseudo noise generator of the DUT to generate an aided-data sequence according to the transmission data, wherein the aided-data sequence is configured to perform cancellation with the far-end data sequence received by the DUT to generate a cancellation result.

In Step S 630 , under a condition where the LP device transmits the far-end data sequence to the DUT and the DUT substantially transmits no data to the LP device, the measuring apparatus 30 may obtain a first noise value according to the cancellation result.

In Step S 640 , under a condition where the LP device transmits the far-end data sequence to the DUT and the DUT utilizes at least one circuit therein to transmit the aided-data sequence to the LP device at the same time, the measuring apparatus 30 may obtain a second noise value according to the cancellation result.

In Step S 650 , the measuring apparatus 30 may calculate a difference between the first noise value and the second noise value, to estimate noise from the at least one circuit.

FIG. 7 is a diagram illustrating an example of the working flow shown in FIG. 6 according to an embodiment of the present invention. It is noted that one or more steps may be added, modified or deleted in the working flow shown in FIG. 7 if an overall result is not hindered, and these steps do not have to be executed in the exact order shown in FIG. 7 .

In Step S 700 , the measuring apparatus 30 may perform initialization setting upon the DUT and the LP device. For example, the DUT is set in the slave mode and the LP device is set in the master mode. In addition, the DUT may be connected to the LP device via a cable such as a 100-meter (100 m) cable, and the measuring apparatus 30 may perform clock synchronization of the DUT and the LP device.

In Step S 710 , the measuring apparatus 30 may link up the DUT and the LP device in the first training phase TP 1 (e.g., controlling these devices to operate in the first training phase TP 1 ), and set a gain of a PGA such as the PGA within the AFE circuit 120 in response to the length of the cable (e.g., 100 m). The DUT may follow a normal procedure of the training phase TP 1 , and the measuring apparatus 30 may monitor a SNR (signal-to-noise ratio) SNR_SL measured by a slicer (e.g., the slicer 160 ) of the DUT.

In Step S 720 , the measuring apparatus 30 may determine whether the SNR SNR_SL exceeds the first predetermined threshold SNR_eye_open (labeled “SNR_SL >SNR_eye_open?”). If the determination result shows “Yes”, it means the equalization processing of the received far-end data sequence is completed (e.g., the signal thereof is stable), and the flow proceeds with Step S 730 ; and if the determination result shows “No”, the flow returns to Step S 710 .

In Step S 730 , the measuring apparatus 30 may keep the LP device in the first training phase TP 1 and reset the equalizer within the DUT (e.g., setting the equalizer in a bypass mode, labeled “EQ=1”), then enable an echo cancellation (EC) operation matching the data (e.g., TXdata) transmitted from the LP device in the DUT, and monitor the SNR SNR_SL measured by the slicer (e.g., the slicer 160 ) of the DUT.

In Step S 740 , the measuring apparatus 30 may determine whether the SNR SNR_SL exceeds the second predetermined threshold SNR_EC_done (labeled “SNR_SL>SNR_EC_done?”). If the determination result shows “Yes”, it means the EC operation mentioned above is completed (e.g., the signal thereof is stable), the flow proceeds with Step S 750 ; and if the determination result shows “No”, the flow returns to Step S 730 .

In Step S 750 , the measuring apparatus 30 may calculate a noise power P 1 received by the slicer, where P 1 =P(noise_far+noise_rx), and P(noise_far+noise Tx) may represent a total power of the far-end noise noise_far and the transmission noise noise_rx.

In Step S 760 , the measuring apparatus 30 may set the LP device and the DUT in the second training phase TP 2 , then utilize a DAC (e.g., the DAC 110 ) of the DUT to output the transmission data TXdata, and monitor the SNR SNR_SL measured by the slicer (e.g., the slicer 160 ) of the DUT.

In Step S 770 , the measuring apparatus 30 may determine whether the SNR SNR_SL exceeds the second predetermined threshold SNR_EC_done (labeled “SNR_SL>SNR_EC_done?”). If the determination result shows “Yes”, it means the EC operation mentioned above is completed (e.g., the signal thereof is stable), and the flow proceeds with Step S 780 ; and if the determination result shows “No”, the flow returns to Step S 760 .

In Step S 780 , the measuring apparatus 30 may calculate a noise power P 2 received by the slicer, where P 2 =P(noise_far+noise_rx+noise_near), and P(noise_far+noise_rx+noise_near) may represent a total power of the far-end noise noise_far, the transmission noise noise_rx and the near-end noise noise_near.

In Step S 790 , the measuring apparatus 30 may calculate a noise power of the DAC of the DUT. For example, the measuring apparatus 30 may calculate a power value P(noise_near) of the near-end noise from the DAC by P 2 −P 1 (e.g., P(noise_near)=P 2 −P 1 ).

To summarize, the embodiments of the present invention can remove impacts of far-end noise, channel noise and non-ideal effects of an equalizer by controlling a measuring procedure to calculate near-end noise under a condition where a device at another side of a cable is transmitting signals. Thus, the embodiments of the present invention can be more close to a real-world case, thereby solving the problem of the related art.

Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.