10base-t transmitter and 10base-t transmission method

Abstract

A 10BASE-T transmitter and a 10BASE-T transmission method are provided. The 10BASE-T transmitter includes a Manchester encoder circuit, a waveform shaper circuit, and a digital-to-analog converter circuit. The Manchester encoder circuit applies Manchester encoding to an input data to generate an encoded data. The waveform shaper circuit converts the encoded data into a plurality of digital codes. The digital-to-analog converter circuit generates a transmission waveform in accordance with the plurality of digital codes. The waveform shaper circuit controls a portion of the plurality of digital codes to apply pre-compensation of inter-symbol interference to the transmission waveform.

Description

Technical Field

[0001] This invention relates to long-distance 10BASE-T transmission, and more particularly to a 10BASE-T transmitter and related methods that use waveform shaping to apply pre-compensation for inter-symbol interference. Background Technology

[0002] The current 10BASE-T physical layer (PHY) is designed based on the 802.3 standard (hereinafter referred to as the IEEE 802.3 standard) developed by the Institute of Electrical and Electronics Engineers (IEEE). Specifically, 10BASE-T is an Ethernet standard for local area networks (LANs). "10" represents a maximum transmission rate of 10 megabits per second (Mbps), "BASE" represents baseband signal transmission, and "T" represents the twisted pair structure. The IEEE 802.3 standard has a voltage template to regulate 10BASE-T Medium Dependent Interface (MDI) signals with 100 meters of Category 3 cable loss (100M CAT3 loss) (worst-case Twisted Pair Model (TPM)). When an MDI signal output from a 10BASE-T physical layer transmitter, conforming to a voltage pattern with 100-meter Category 3 cable loss, is transmitted over longer network cables (e.g., 400 meters or more), it suffers from severe inter-symbol interference (ISI), causing 10BASE-T physical layer receivers to experience slicing errors. Most 10BASE-T physical layer receiver designs lack linear equalizers or digital front-end circuitry (such as feed-forward equalizers or decision-feedback equalizers) to equalize ISI in the channel. Therefore, an innovative 10BASE-T physical layer transmitter design is needed to eliminate or mitigate ISI after the MDI signal has traveled a long distance. Summary of the Invention

[0003] One of the objectives of this invention is to provide a 10BASE-T transmitter and related methods for applying pre-compensation for inter-symbol interference using waveform shaping.

[0004] In one embodiment of the present invention, a 10BASE-T transmitter is disclosed. The 10BASE-T transmitter includes a Manchester encoder circuit, a waveform shaper circuit, and a digital-to-analog converter circuit. The Manchester encoder circuit applies Manchester encoding to input data to generate encoded data. The waveform shaper circuit converts the encoded data into a plurality of digital codes. The digital-to-analog converter circuit generates a transmission waveform based on the plurality of digital codes. The waveform shaper circuit controls a portion of the plurality of digital codes to apply pre-compensation for inter-symbol interference to the transmission waveform.

[0005] In one embodiment of the present invention, a 10BASE-T transmission method is disclosed. The 10BASE-T transmission method includes: applying Manchester encoding to input data to generate encoded data; converting the encoded data to a plurality of digital codes; and performing a digital-to-analog conversion on the plurality of digital codes to generate a transmission waveform. The step of converting the encoded data to the plurality of digital codes includes: controlling a portion of the plurality of digital codes to apply pre-compensation for inter-symbol interference to the transmission waveform. Attached Figure Description

[0006] Figure 1 This is a schematic diagram of a 10BASE-T system according to an embodiment of the present invention.

[0007] Figure 2 for Figure 1 The diagram shows the 10BASE-T Manchester encoding used by the 10BASE-T transmitter.

[0008] Figure 3 This is a schematic diagram of a portion of the transmission waveform of the MDI signal generated for long-distance 10BASE-T media dependent interface transmission according to an embodiment of the present invention.

[0009] Figure 4 This is a schematic diagram of a transmission waveform with pre-compensation for inter-symbol interference according to an embodiment of the present invention.

[0010] Figure 5 This is a schematic diagram of a waveform shaper circuit according to an embodiment of the present invention.

[0011] Figure 6 Initialization and update of an embodiment of the present invention Figure 5 The diagram shows the count value tbt_cnt output by the counter.

[0012] Figure 7This is a schematic diagram illustrating various operational behaviors of a state machine according to an embodiment of the present invention.

[0013] Figure 8 for Figure 5 The oversampling digital-to-analog converter circuit shown is in Figure 5 The diagram shows the transmission waveform generated under the control of the state machine.

[0014] [Symbol Explanation]

[0015] 100:10BASE-T system

[0016] 102:10BASE-T Transmitter

[0017] 104:10BASE-T receiver

[0018] 106: Twisted Pair Cable

[0019] 112: Serializer circuit

[0020] 114: Manchester encoder circuit

[0021] 116, 502: Waveform Shaper Circuit

[0022] 118: Transmission of digital-to-analog converter and driver circuit

[0023] 122: Receiver Variable Gain Amplifier and Clipper Circuit

[0024] 124: Manchester Decoder Circuit

[0025] 126: Deserializer Circuit

[0026] 504: Counter

[0027] 506: State Machine

[0028] 508_1, 508_N: Lookup table

[0029] 510: Oversampling Digital-to-Analog Converter Circuit

[0030] D1: Input Data

[0031] D2: Encoded Data

[0032] D3: Numeric code

[0033] BT: Bit Time

[0034] tbt_cnt: Count value

[0035] ST_SIN, ST_IDLE, ST_HOLD, ST_FIN, ST_FLAT: status Detailed Implementation

[0036] Certain terms are used in the specification and claims to refer to specific elements. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same element. This specification and claims do not distinguish elements based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." Furthermore, the terms "coupled" or "coupled" herein include any direct and indirect electrical connection means. Therefore, if a first device is described as coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices and connection means.

[0037] Figure 1 This is a schematic diagram of a 10BASE-T system according to an embodiment of the present invention. The 10BASE-T system 100 is an Ethernet system and includes a 10BASE-T transmitter 102 and a 10BASE-T receiver 104. The MDI signal is transmitted from the 10BASE-T transmitter 102 to the 10BASE-T receiver 104 via a twisted-pair cable 106. The 10BASE-T transmitter 102 includes a serializer circuit (labeled as serializer in the diagram) 112, a Manchester encoder circuit (labeled as Manchester encoder in the diagram) 114, a wave shaper circuit (labeled as wave shaper in the diagram) 116, and a transmit (TX) digital-to-analog converter (DAC) and driver circuit (labeled as transmit DAC & driver in the diagram) 118. The 10BASE-T receiver 104 includes a receive (RX) variable gain amplifier (VGA) and slicer circuit (labeled as receive variable gain amplifier & slicer in the diagram) 122, and a Manchester decoder... The circuit includes a decoder (labeled as Manchester decoder) 124 and a deserializer (labeled as deserializer) 126. Since the focus of this invention is on the design of the 10BASE-T transmitter 102, further description of the 10BASE-T receiver 104 is omitted here for brevity. Note that only elements relevant to this invention are shown. Figure 1In fact, the 10BASE-T transmitter 102 may include additional components to achieve other functions.

[0038] Serializer circuit 112 receives medium independent interface (MII) data from the media access control (MAC) layer and converts this MII data into serial data as input data D1 for the subsequent Manchester encoder circuit 114. Manchester encoder circuit 114 applies Manchester encoding to the input data D1 to generate encoded data D2. Manchester code always undergoes a transition in the middle of each bittime, and depending on the data to be transmitted, the transition can occur at the beginning of the bittime. The direction of the mid-bit transition indicates the bit value. Transitions at the leading and trailing boundaries of the bittime do not carry any information; their existence is solely to set the signal in the correct state to allow for mid-bit transitions. Figure 2 for Figure 1 The diagram shows the 10BASE-T Manchester encoding used by the 10BASE-T transmitter 102. One bit time BT is defined as one clock cycle of the clock signal used by the Manchester encoder circuit 114, such as... Figure 2 As shown, input data D1 contains multiple consecutive bits (1, 0, 1, 0, 0, 1, 1, 1, 0, 0, 1). Manchester encoding of input data D1 can be performed using a mutually exclusive OR operation (XOR) between input data D1 and the clock signal. Therefore, the encoded data D2 output by the Manchester encoder circuit 114 will transition in the middle of each bit time, where a transition from low logic level "0" to high logic level "1" represents a bit value "1", and a transition from high logic level "1" to low logic level "0" represents a bit value "0". In 10BASE-T Manchester encoding, only two symbol frequencies exist, such as... Figure 2 As shown, the Manchester encoding result of consecutive bits with the same bit value (e.g., all "1" or all "0") will have a symbol frequency of 10 MHz, while the Manchester encoding result of consecutive bits with interleaved bit values ​​(e.g., 01010101...) will have another symbol frequency of 5 MHz.

[0039] Waveform shaper circuit 116 is used to convert encoded data D2 into multiple digital codes D3. Transmit digital-to-analog converter and driver circuit 118 includes a digital-to-analog converter to generate a transmit waveform (TX waveform) based on the multiple digital codes D3, and also includes a transmitter circuit to output the transmit waveform to 10BASE-T receiver 104 via twisted pair 106. If the transmission waveform of the MDI signal output by the 10BASE-T transmitter 102 conforms to the voltage template with 100-meter Category 3 cable loss specified in the IEEE 802.3 standard, then this transmission waveform will have a serious inter-symbol interference problem when transmitted over a longer (e.g., 400 meters or longer) twisted pair 106. In order to solve this problem encountered in long-distance 10BASE-T MDI transmission, the present invention proposes to use a waveform shaper circuit 116 to control a portion of the plurality of digital codes D3 to apply pre-compensation for inter-symbol interference to the transmission waveform of the MDI signal transmitted over a longer (e.g., 400 meters or longer) twisted pair 106.

[0040] Figure 3 This is a schematic diagram of a portion of the transmission waveform of the MDI signal generated for long-distance 10BASE-T media-dependent interface transmission according to an embodiment of the present invention. The partial transmission waveform 302 without the inter-symbol interference pre-compensation disclosed in this invention conforms to the IEEE 802.3 standard. In contrast, the partial transmission waveform 304 with the inter-symbol interference pre-compensation disclosed in this invention does not conform to the IEEE 802.3 standard. For example, the partial transmission waveform 302 without the inter-symbol interference pre-compensation disclosed in this invention conforms to the voltage template with 100 meters of Category 3 cable loss as specified in the IEEE 802.3 standard; however, the partial transmission waveform 304 with the inter-symbol interference pre-compensation disclosed in this invention does not conform to the voltage template with 100 meters of Category 3 cable loss as specified in the IEEE 802.3 standard. Figure 3Each of the partial transmission waveforms 302 and 304 shown is generated for a portion of the plurality of digital codes D3 output by the Manchester encoder circuit 114, and that portion of the plurality of digital codes D3 is generated for two consecutive bits (1, 0) in the encoded data D2. Partial transmission waveform 302 includes a first sinusoidal part S1, a non-sinusoidal part S2, and a second sinusoidal part S3, wherein the non-sinusoidal part S2 immediately follows the first sinusoidal part S1, and the second sinusoidal part S3 immediately follows the non-sinusoidal part S2. Partial transmission waveform 304 includes a first sinusoidal part P1, a non-sinusoidal part P2, and a second sinusoidal part P3, wherein the non-sinusoidal part P2 immediately follows the first sinusoidal part P1, and the second sinusoidal part P3 immediately follows the non-sinusoidal part P2. When the 10BASE-T transmitter 102 enables waveform shaping to apply pre-compensation for inter-symbol interference to the transmitted waveform of the MDI signal, the waveform shaper circuit 116 controls a portion of the plurality of digital codes D3 to delay the end time of the first sine wave portion, and / or controls a portion of the plurality of digital codes D3 to ensure that the non-sine wave portion has a constant level. Compared to the first sine wave portion S1 of the partial transmitted waveform 302, the first sine wave portion P1 of the partial transmitted waveform 304 is extended to de-emphasize the subsequent non-sine wave portion. Furthermore, compared to the slope shape of the non-sine wave portion S2 of the partial transmitted waveform 302, the non-sine wave portion P2 of the partial transmitted waveform 304 is pure flat, which maximizes the de-emphasis of the non-sine wave portion. Due to the deemphasis of the non-sinusoidal portion, part of the transmitted waveform 304 cannot comply with the voltage template for 100-meter Category 3 cable loss specified in the IEEE 802.3 standard. However, the deemphasis of the non-sinusoidal portion of the transmitted waveform 304 allows the transmitted waveform that does not comply with the IEEE 802.3 standard to be emphasized (emphasized) with a high-frequency waveform (10 MHz), which can pre-compensate for inter-symbol interference in the case of ultra-long network lines (e.g., 400 meters or longer).

[0041] Figure 3The partial transmission waveform 304 shown is generated for a portion of the plurality of digital codes D3 output by the Manchester encoder circuit 114, wherein this portion of the plurality of digital codes D3 is generated for two consecutive bits (1, 0) in the encoded data D2. The same waveform shaping concept can be applied to the partial transmission waveform generated for a portion of the plurality of digital codes D3 output by the Manchester encoder circuit 114, wherein this portion of the plurality of digital codes D3 is generated for two consecutive bits (0, 1) in the encoded data D2. Figure 4 This is a schematic diagram of a transmission waveform with pre-compensation for inter-symbol interference according to an embodiment of the present invention. Compared to a waveform with a ramp-shaped non-sinusoidal portion that conforms to the IEEE 802.3 standard (as shown by the dashed line), a waveform with a delayed and de-emphasized non-sinusoidal portion (e.g., a purely flat portion immediately following an extended sinusoidal portion) that does not conform to the IEEE 802.3 standard (as shown by the solid line) can eliminate or mitigate the problem of inter-symbol interference when transmitted over a longer (e.g., 400 meters or more) twisted pair 106.

[0042] In some embodiments of the present invention, the digital-to-analog converter circuit used by the transmitting digital-to-analog converter and driver circuit 118 may be an oversampling digital-to-analog converter with a sampling rate higher than the data rate of the input data D1 to be transmitted, and / or the plurality of digital codes D3 fed into the oversampling digital-to-analog converter may be appropriately controlled for pre-compensation of inter-symbol interference by using a state machine and a plurality of lookup tables. Figure 5 This is a schematic diagram of a waveform shaper circuit according to an embodiment of the present invention. Figure 1 The waveform shaper circuit 116 shown can be implemented by the waveform shaper circuit 502, and Figure 1 The digital-to-analog converter circuit used in the illustrated transmission digital-to-analog converter and driver circuit 118 can be implemented by an oversampling digital-to-analog converter 510. For example, the oversampling digital-to-analog converter 510 operates based on a sampling clock with a clock frequency of 250 MHz. The waveform shaper circuit 502 includes a counter 504, a state machine 506, and multiple lookup tables 508_1 to 508_N (N≥2). Since the clock frequency (250 MHz) of the oversampling clock CLK250M is higher than the data rate (10 MHz) of the input data D1, the counter 504 is used to generate and update a count value tbt_cnt to indicate each sampling time point in one bit time. Figure 6This diagram illustrates the initialization and updating of the count value tbt_cnt output by counter 504 according to an embodiment of the present invention. When the 10BASE-T physical layer transmitter is reset, the count value tbt_cnt is initialized to a preset value (e.g., 0). The count value tbt_cnt is continuously updated in response to each pulse of the oversampling clock CLK250M, and is reset to the preset value (e.g., 0) each time it reaches a value of 25.

[0043] State machine 506 operates based on a finite number of states. Based on the current state and the given input, state machine 506 performs a state transition and produces an output. Figure 7 This is a schematic diagram illustrating various operational behaviors of a state machine 506 according to an embodiment of the present invention. Figure 8 This is a schematic diagram of the transmission waveform generated by the oversampling digital-to-analog converter circuit 510 under the control of state machine 506. In this embodiment, state machine 506 has 5 states: ST_IDLE, ST_SIN, ST_FLAT, ST_HOLD, and ST_FIN; and lookup tables 508_1 to 508_N may contain LUT_SIN_0t, LUT_SIN_0.5t, LUT_FLAT_0t, LUT_FLAT_0.5t, LUT_HOLD_0t, LUT_HOLD_0.5t, LUT_FIN_0t, and LUT_FIN_0.5t. Regarding the partial transmission waveform 304 employing the pre-compensation for inter-symbol interference disclosed in this invention, when state machine 506 enters the ST_SIN state, multiple digital codes for each of the first sine wave portion P1 and the second sine wave portion P3 are set, and when state machine 506 enters the ST_FLAT state, multiple digital codes for the non-sine wave portion P2 are set. The end time of the first sine wave portion P1 is delayed by extending the ST_SIN state time; in other words, the end time of the first sine wave portion P1 can be delayed by controlling the transition from the ST_SIN state to the ST_FLAT state. Furthermore, the non-sine wave portion P2 in the partial transmission waveform 304 can be set to be purely flat by appropriately setting the lookup table referenced in the ST_FLAT state.

[0044] Please note, Figure 5 The embodiments shown above are for illustrative purposes only and are not intended to limit the invention. In fact, any method that utilizes the pre-compensation for inter-symbol interference disclosed in this invention to generate the transmission waveform of the MDI signal (e.g.) Figure 4 The transmission waveform shown or Figure 3The means of transmitting the partial waveform 304 shown, which has an extended sine wave portion to de-emphasize the subsequent non-sine wave portion and / or the non-sine wave portion is set to be purely flat to maximize the de-emphasis of the non-sine wave portion, all fall within the scope of the present invention.

[0045] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made in accordance with the claims of the present invention shall be within the scope of the present invention.

Claims

1. A 10BASE-T transmitter, comprising: Manchester encoder circuit, used to apply Manchester encoding to input data to generate encoded data; A waveform shaper circuit is used to convert the encoded data into multiple digital codes; as well as A digital-to-analog converter circuit is used to generate a transmission waveform based on the plurality of digital codes; The waveform shaper circuit controls a portion of the plurality of digital codes to apply pre-compensation for inter-symbol interference to the transmitted waveform, which includes a sine wave portion and a non-sine wave portion immediately following the sine wave portion, and the pre-compensation includes de-emphasis of the non-sine wave portion.

2. The 10BASE-T transmitter as claimed in claim 1, wherein the transmission waveform does not conform to the voltage template specified in the IEEE 802.3 standard.

3. The 10BASE-T transmitter of claim 1, wherein the portion of the plurality of digital codes is generated for a plurality of consecutive bits in the encoded data, the plurality of consecutive bits including a first bit and a second bit immediately following the first bit, and the first bit and the second bit having different bit values.

4. The 10BASE-T transmitter of claim 3, wherein a portion of the transmission waveform is generated for that portion of the plurality of digital codes.

5. The 10BASE-T transmitter of claim 4, wherein the waveform shaper circuit controls a portion of the plurality of digital codes to delay the end time of the sine wave portion.

6. The 10BASE-T transmitter of claim 4, wherein the waveform shaper circuit controls a portion of the plurality of digital codes such that the non-sinusoidal portion has a fixed level.

7. The 10BASE-T transmitter as claimed in claim 3, wherein the first bit and the second bit are 0 and 1, respectively.

8. The 10BASE-T transmitter as claimed in claim 3, wherein the first bit and the second bit are 1 and 0, respectively.

9. The 10BASE-T transmitter of claim 1, wherein the waveform shaper circuit comprises: State machines; and Multiple lookup tables.

10. The 10BASE-T transmitter as claimed in claim 1, wherein the digital-to-analog converter circuit is an oversampling digital-to-analog converter circuit.

11. A 10BASE-T transmission method, comprising: Apply Manchester encoding to the input data to produce encoded data; Convert the encoded data to multiple numeric codes; and The multiple digital codes are converted from digital to analog to generate a transmission waveform; The steps involved in converting the encoded data into multiple numeric codes include: A portion of the plurality of digital codes is controlled to apply pre-compensation for inter-symbol interference to the transmitted waveform, wherein the transmitted waveform includes a sine wave portion and a non-sine wave portion immediately following the sine wave portion, and the pre-compensation includes de-emphasis of the non-sine wave portion.

12. The 10BASE-T transmission method as described in claim 11, wherein the transmission waveform does not conform to the voltage template specified in the IEEE 802.3 standard.

13. The 10BASE-T transmission method of claim 11, wherein the portion of the plurality of digital codes is generated for a plurality of consecutive bits in the encoded data, the plurality of consecutive bits including a first bit and a second bit immediately following the first bit, and the first bit and the second bit having different bit values.

14. The 10BASE-T transmission method of claim 13, wherein a portion of the transmission waveform is generated for that portion of the plurality of digital codes.

15. The 10BASE-T transmission method of claim 14, wherein a portion of the plurality of digital codes is controlled to delay the end time of the sine wave portion.

16. The 10BASE-T transmission method of claim 14, wherein a portion of the plurality of digital codes is controlled such that the non-sinusoidal portion has a fixed level.

17. The 10BASE-T transmission method as described in claim 13, wherein the first bit and the second bit are 0 and 1, respectively.

18. The 10BASE-T transmission method as described in claim 13, wherein the first bit and the second bit are 1 and 0, respectively.

19. The 10BASE-T transmission method as claimed in claim 11, wherein the step of converting the encoded data into a plurality of digital codes comprises: It uses a state machine and multiple lookup tables.

20. The 10BASE-T transmission method of claim 11, wherein the digital-to-analog conversion is an oversampled digital-to-analog conversion.

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