How to set the equalizer

Abstract

The present invention discloses a method for setting an equalizer, comprising generating an unequalized impulse response, converting N transfer functions of a continuous-time linear equalizer from a frequency domain to a time domain to generate N continuous-time linear equalizer impulse responses, performing convolution integration operations on the N continuous-time linear equalized impulse responses and the unequalized impulse response respectively to generate N initial equalized impulse responses, generating a set of tap coefficients according to each initial equalized impulse response in the N initial equalized impulse responses and M target output values ​​of a feedforward equalizer, generating a signal quality of a complete equalized impulse response according to each initial equalized impulse response and the set of tap coefficients, and setting the continuous-time linear equalizer and the feedforward equalizer according to the best signal quality among the N signal qualities corresponding to the N initial equalized impulse responses and the N sets of tap coefficients.

Description

Technical Field

[0001] The present invention relates to a communication system, and in particular to a method for setting an equalizer. Background Art

[0002] Equalizers are commonly used in integrated circuit transmitters and receivers to improve inter-symbol interference (ISI) problems caused by signal attenuation, reflection, and crosstalk. However, related technologies perform equalizer optimization at the transmitter and receiver separately, so it is impossible to obtain the best combination of setting values ​​for the transmitter and receiver, and it is also impossible to obtain the best signal quality. Summary of the invention

[0003] An embodiment of the present invention provides a method for setting an equalizer, comprising generating an un-equalized impulse response of a feedforward equalizer of a transmitting device and a continuous-time linear equalizer of a receiving device, converting N transfer functions of the continuous-time linear equalizer from a frequency domain to a time domain to generate N continuous-time linear equalizer impulse responses, performing convolution integration operations on the N continuous-time linear equalized impulse responses and the un-equalized impulse response to generate N initial equalized impulse responses, generating a corresponding set of tap coefficients according to each initial equalized impulse response of the N initial equalized impulse responses and M target output values ​​of the feedforward equalizer, the set of tap coefficients including M tap coefficients, generating a signal quality of a complete equalized impulse response according to each initial equalized impulse response and the set of tap coefficients, selecting an optimal signal quality from N signal qualities corresponding to the N initial equalized impulse responses and the N sets of tap coefficients, and setting the continuous-time linear equalizer and the feedforward equalizer according to the optimal signal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 FIG. 4 is a block diagram of a communication system according to an embodiment of the present invention.

[0005] Figure 2 To set Figure 1 Flowchart of a method for a medium neutralizer.

[0006] Figure 3 A waveform plot showing the unequalized pulse response.

[0007] Figure 4 The frequency response of the transfer function is shown.

[0008] Figure 5 A waveform graph showing the continuous-time linear equalizer impulse response and the initial equalized impulse response.

[0009] Figure 6 for Figure 1 Schematic diagram of the feedforward equalizer.

[0010] Figure 7 show Figure 6 Signal waveform of the feedforward equalizer.

[0011] Figure 8 A waveform plot showing the complete equalized impulse response.

[0012] Explanation of symbols:

[0013] 1: Communication system

[0014] 10:Transmission device

[0015] 100: Feedforward equalizer

[0016] 12: Communication Channel

[0017] 14: Receiving device

[0018] 140:Continuous-time linear equalizer

[0019] 200: Method

[0020] S202 to S214: Steps

[0021] 30,401 to 415,50,52,70 to 76,80: Waveform

[0022] 601 to 603: Delay element

[0023] 621 to 624: Multiplier

[0024] 64: Adder

[0025] C(-1) to C(2): tap coefficients

[0026] N: Noise power

[0027] P: signal power

[0028] Stx: Transmit signal

[0029] Srx: Receive signal

[0030] t0 to t3: time

[0031] V(-1) to V(2): Voltage

[0032] X(k+1): input signal

[0033] X(k),X(k-1),X(k-2): Delayed equalized impulse response

[0034] Yk: output signal DETAILED DESCRIPTION

[0035] Figure 11 is a block diagram of a communication system 1 according to an embodiment of the present invention. The communication system 1 includes a transmission device 10, a communication channel 12, and a receiving device 14. The transmission device 10 is coupled to the receiving device 14 through the communication channel 12. The transmission device 10 can transmit a transmission signal Stx. When the transmission signal Stx passes through the communication channel 12, its signal quality may be attenuated to generate a receiving signal Srx. The receiving device 14 can receive the receiving signal Srx. The communication channel 12 can be a wired channel, a wireless channel, or a combination thereof, and can be implemented by a transmission medium such as an optical fiber, a cable, or air. The communication channel 12 can transmit voice data, image data, and other data.

[0036] The transmitting device 10 includes a feed-forward equalizer (FFE) 100, and the receiving device 14 includes a continuous time linear equalizer (CTLE) 140. The feed-forward equalizer 100 can be a finite impulse response (FIR) filter or a least mean square (LMS) filter. The continuous time linear equalizer 140 can be an active and / or passive continuous time linear equalizer. Both the feed-forward equalizer 100 and the continuous time linear equalizer 140 can reduce inter-symbol interference (ISI) and improve signal quality.

[0037] The present invention provides a method 200 for setting a feedforward equalizer 100 and a continuous-time linear equalizer 140, which simultaneously considers the optimization of the tap coefficients of the feedforward equalizer 100 and the optimization of the setting values ​​of the continuous-time linear equalizer 140, so as to improve the signal quality of the communication system 1. Compared with the related art, since the communication system in the related art performs the optimization of the tap coefficients of the feedforward equalizer and the optimization of the setting values ​​of the continuous-time linear equalizer separately, it may not be possible to obtain the combination of the optimal tap coefficients of the feedforward equalizer and the optimal setting values ​​of the continuous-time linear equalizer, and it is also impossible to obtain the optimal signal quality.

[0038] Figure 2The method 200 for setting the feedforward equalizer 100 and the continuous-time linear equalizer 140 is a flow chart. The method 200 includes steps S202 to S214. Steps S202 to S210 are used to simultaneously consider the signal quality of the feedforward equalizer 100 and the continuous-time linear equalizer 140 to generate a complete equalized impulse response, and steps S212 and S214 are used to set the method 200 of the feedforward equalizer 100 and the continuous-time linear equalizer 140 according to the best signal quality. Steps S202 to S214 are performed on a computer using software. Any reasonable technical changes or step adjustments fall within the scope of the present invention. Steps S202 to S214 are described below:

[0039] Step S202: Generate an unequalized impulse response of the feedforward equalizer 100 of the transmitting device 10 and the continuous-time linear equalizer 140 of the receiving device 14 without using the feedforward equalizer 100 of the transmitting device 10;

[0040] Step S204: converting the N transfer functions of the continuous-time linear equalizer 140 from the frequency domain to the time domain to generate N continuous-time linear equalizer impulse responses;

[0041] Step S206: performing convolution integral operations on the N continuous-time linear equalized impulse responses and the unequalized impulse responses respectively to generate N initial equalized impulse responses;

[0042] Step S208: generating a corresponding set of tap coefficients according to each of the N initial equalized impulse responses and the M target output values ​​of the feedforward equalizer 100;

[0043] Step S210: Generate the signal quality of a complete equalized impulse response according to each initial equalized impulse response and the set of tap coefficients;

[0044] Step S212: Selecting the best signal quality from N signal qualities corresponding to N initial equalized impulse responses and N sets of tap coefficients;

[0045] Step S214: Setting the continuous-time linear equalizer 140 and the feedforward equalizer 100 according to the best signal quality.

[0046] In step S202 , the simulation software uses an equivalent model of the transmitter 10 without the feedforward equalizer 100 , an equivalent model of the communication channel 12 , and an equivalent model of the receiver 14 without the continuous-time linear equalizer 140 to simulate an unequalized impulse response. Figure 3 The waveform diagram of the unequalized impulse response 30 is shown, wherein the horizontal axis represents time and the vertical axis represents signal amplitude.

[0047] In step S204, N transfer functions may be continuous-time linear equalizer transfer functions that comply with the specifications of various associations (such as PCI-SIG, IEEE, SNIA, OIF-CEI) pre-defined in simulation software, and the N transfer functions are converted into N continuous-time linear equalizer impulse responses using an inverse Fourier transform (IFT). Figure 4 The frequency responses of the transfer functions 401 to 415 are shown, with the horizontal axis representing frequency and the vertical axis representing gain.

[0048] Next, in step S206, N initial equalized impulse responses respectively represent the equalized impulse responses generated by considering the setting value of the continuous-time linear equalizer 140 but not considering the N setting value of the feedforward equalizer 100. Each continuous-time linear equalizer impulse response can be convolutionally integrated with the unequalized impulse response to generate an initial equalized impulse response. For example, 15 continuous-time linear equalizer impulse responses can generate 15 initial equalized impulse responses. Figure 5 The waveform diagram of the embodiment of the continuous-time linear equalizer impulse response 50 and the initial equalized impulse response 52 is shown, wherein the horizontal axis represents time and the vertical axis represents signal amplitude.

[0049] Figure 6A schematic diagram of a 4-tap feedforward equalizer 100 is shown. The feedforward equalizer 100 includes delay elements 601 to 603, multipliers 621 to 624, and an adder 64. The feedforward equalizer 100 can receive an input signal X(k+1) and generate an output signal Yk. The input signal X(k+1) can be an initial equalized impulse response 52. The delay elements 601 to 603 can delay the input signal X(k+1) three times to generate three delayed equalized impulse responses X(k), X(k-1), and X(k-2). The delay times of the delay elements 601 to 603 can be the same or different. The delayed equalized impulse response X(k) is the main-cursor, the input signal X(k+1) is the pre-cursor, and the delayed equalized impulse responses X(k-1) and X(k-2) are the post-cursors. Each of the multipliers 621 to 624 has settable tap coefficients C(-1), C(0), C(1), and C(2). The multiplier 621 can multiply the input signal X(k+1) and the tap coefficient C(-1) to generate a multiplication output X(k+1)*C(-1). Similarly, the multiplier 622 can multiply the delayed equalized impulse response X(k) and the tap coefficient C(0) to generate a multiplication output X(k)*C(0), the multiplier 623 can multiply the delayed equalized impulse response X(k-1) and the tap coefficient C(1) to generate a multiplication output X(k-1)*C(1), and the multiplier 624 can multiply the delayed equalized impulse response X(k-2) and the tap coefficient C(2) to generate a multiplication output X(k-2)*C(2). The adder 64 can add the multiplication outputs X(k+1)*C(-1), X(k)*C(0), X(k-1)*C(1) and X(k-2)*C(2) to generate an output signal Yk, as shown in formula (1):

[0050]

[0051] Since the input signal X(k-1) of the feedforward equalizer 100 is the initial equalized impulse response 52 , the output signal Yk is the complete equalized impulse response that takes both the feedforward equalizer 100 and the continuous-time linear equalizer 140 into consideration.

[0052] In step S208, each initial equalized impulse response X(k+1) may be delayed by (M-1) to generate an (M-1) delayed equalized impulse response, M formulas may be generated according to each initial equalized impulse response, the (M-1) delayed equalized impulse response and the M target output values, and M tap coefficients of the corresponding set of tap coefficients may be calculated according to the M formulas, where M is the number of taps and M is a positive integer greater than 1. For example, Figure 6In the 4-tap feedforward equalizer 100, M is equal to 4, and the delay elements 601 to 603 can delay each initial equalized impulse response X(k+1) by 3 to generate 3 delayed equalized impulse responses, generate 4 formulas according to each initial equalized impulse response X(k+1), the 3 delayed equalized impulse responses and the 4 target output values, and calculate the 4 tap coefficients of the corresponding set of tap coefficients according to the 4 formulas.

[0053] Figure 7 show Figure 6 4-tap feedforward equalizer 100, wherein the horizontal axis represents time and the vertical axis represents signal amplitude, and waveforms 70 to 76 represent multiplication outputs X(k+1)*C(-1), X(k)*C(0), X(k-1)*C(1) and X(k-2)*C(2) respectively. In step S208, the user can pre-set the four target output values ​​of the feedforward equalizer 100 at time t0 to t3 to 0, 1, 0, 0 respectively.

[0054] At time t0, the voltage of waveform 70 is V(0)C(-1), the voltage of waveform 72 is V(-1)C(0), and the voltages of waveforms 74 and 76 are approximately 0, so equation (2) can be obtained based on equation (1). At time t1, the voltage of waveform 70 is V(1)C(-1), the voltage of waveform 72 is V(0)C(0), the voltage of waveform 74 is V(-1)C(1), and the voltage of waveform 76 is approximately 0, so equation (3) can be obtained based on equation (1). At time t2, the voltage of waveform 70 is V(2)C(-1), the voltage of waveform 72 is V(1)C(0), the voltage of waveform 74 is V(0)C(1), and the voltage of waveform 76 is V(-1)C(2), so equation (4) can be obtained based on equation (1). At time t3, the voltage of waveform 70 is approximately 0, the voltage of waveform 72 is V(2)C(0), the voltage of waveform 74 is V(1)C(1), and the voltage of waveform 76 is V(0)C(2). Therefore, formula (5) can be obtained based on formula (1).

[0055] V(0)C(-1)+V(-1)C(0)=0 Formula (2)

[0056] V(1)C(-1)+V(0)C(0)+V(-1)C(1)=1 Formula (3)

[0057] V(2)C(-1)+V(1)C(0)+V(0)C(1)+V(-1)C(2)=0 Formula (4)

[0058] V(2)C(0)+V(1)C(1)+V(0)C(2)=0 Formula (5)

[0059] Therefore, each tap coefficient C(-1), C(0), C(1), and C(2) can be solved by formulas (2) to (5), and the obtained tap coefficients C(-1), C(0), C(1), and C(2) are a set of tap coefficients corresponding to each initial equalized impulse response X(k+1) after using the continuous-time linear equalizer 140. For example, 15 initial equalized impulse responses X(k+1) can generate 15 sets of tap coefficients.

[0060] although Figure 7 The waveforms 70 to 76 have the same shape, and in some embodiments the shapes of the waveforms 70 to 76 may be different. In addition, although a 4-tap feedforward equalizer 100 is used in the embodiment to illustrate step S208, a person skilled in the art may also use a feedforward equalizer 100 with other tap numbers to perform step S208 according to similar principles.

[0061] Then, in step S210, the initial equalized impulse response X(k+1) and the set of tap coefficients may be used to generate a complete equalized impulse response Yk according to formula (1), and the signal quality may be generated according to the complete equalized impulse response Yk. For example, 15 initial equalized impulse responses X(k+1) and 15 sets of tap coefficients may generate 15 complete equalized impulse responses Yk and 15 signal qualities. The signal quality may be represented by a signal-to-noise ratio, Figure 8 The waveform diagram of the complete equalized pulse response Yk is shown, wherein the horizontal axis represents time and the vertical axis represents signal amplitude. The waveform 80 is the complete equalized pulse response Yk. The simulation software can integrate the complete equalized pulse response Yk within a predetermined time interval to generate a signal power P, as shown in formula (6):

[0062]

[0063] exist Figure 8 In the example, the predetermined time interval is between the lower time limit t1 and the upper time limit t2. In addition, the simulation software can integrate the complete equalized impulse response Yk of the first time interval and the second time interval outside the predetermined time interval to generate the noise power N, as shown in formula (7):

[0064]

[0065] exist Figure 8 In the equation, the first time interval is between the minimum time t0 and the lower time limit t1, the second time interval is between the upper time limit t2 and the maximum time t3, the minimum time t0 is less than the lower time limit t1, and the maximum time t3 is greater than the upper time limit t2. Finally, the simulation software can generate the signal-to-noise ratio SNR according to the signal power P and the noise power N, as shown in formula (8-1) or (8-2):

[0066] SNR=PN formula (8-1)

[0067] SNR=P / N Formula (8-2)

[0068] In step S212, the maximum signal-to-noise ratio SNR may be selected from the N signal-to-noise ratios SNR as the best signal quality. In step S214, a set of best continuous-time linear equalizer settings of the continuous-time linear equalizer 140 and a set of best tap coefficients of the feedforward equalizer 100 are determined according to the best signal quality, the continuous-time linear equalizer 140 is set according to the set of best continuous-time linear equalizer settings, and the feedforward equalizer 100 is set according to the set of best tap coefficient settings. For example, a set of best continuous-time linear equalizer settings may include a DC gain setting value, a low-frequency gain setting value, a zero frequency setting value, a pole frequency setting value and / or other settings, and a set of best tap coefficient settings may include tap coefficients C(-1) to C(2).

[0069] The method 200 simultaneously optimizes the tap coefficients of the feedforward equalizer 100 and the settings of the continuous-time linear equalizer 140 to improve the signal quality of the communication system 1 .

[0070] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the claims of the present invention should fall within the scope of the present invention.

Claims

1. A method for setting an equalizer, characterized in that: Include: generating an unequalized impulse response without using a feedforward equalizer of a transmitting device and a continuous-time linear equalizer of a receiving device; converting the N transfer functions of the continuous-time linear equalizer from the frequency domain to the time domain to generate N continuous-time linear equalized impulse responses; Perform convolution integration operations on the N continuous-time linear equalized impulse responses and the unequalized impulse responses respectively to generate N initial equalized impulse responses; Generate a corresponding set of tap coefficients according to each of the N initial equalized impulse responses and the M target output values ​​of the feedforward equalizer, wherein the set of tap coefficients includes M tap coefficients, and M is a positive integer greater than 1; Generating a signal quality of a complete equalized impulse response according to each of the initial equalized impulse responses and the set of tap coefficients; Selecting an optimal signal quality from N signal qualities corresponding to the N initial equalized impulse responses and N sets of tap coefficients; and The continuous-time linear equalizer and the feedforward equalizer are set according to the best signal quality.

2. The method for setting an equalizer according to claim 1, wherein: Wherein, generating the corresponding set of tap coefficients according to each of the N initial equalized impulse responses and the M target output values ​​of the feedforward equalizer comprises: Delaying each of the initial equalized impulse responses by (M-1) to generate (M-1) delayed equalized impulse responses; Generate M formulas according to each of the initial equalized impulse responses, the (M-1) delayed equalized impulse responses and the M target output values; and The M tap coefficients are calculated according to the M formulas.

3. The method for setting an equalizer according to claim 1, wherein: The signal quality is a signal-to-noise ratio.

4. The method for setting an equalizer according to claim 3, wherein: Wherein, generating the signal quality of the complete equalized impulse response according to each of the initial equalized impulse responses and the set of tap coefficients comprises: Integrating the complete equalized impulse response within a predetermined time interval to generate a signal power; integrating the complete equalized impulse response outside the predetermined time interval to generate a noise power; and The signal-to-noise ratio is generated according to the signal power and the noise power.

5. The method for setting an equalizer according to claim 4, wherein: The integrating the complete equalized impulse response outside the predetermined time interval to generate the noise power comprises: Integrating the complete equalized impulse response in a first time interval and a second time interval outside the predetermined time interval to generate the noise power; The predetermined time interval is between a lower time limit and an upper time limit; The first time interval is between a minimum time and the time lower limit; The second time interval is between the upper time limit and a maximum time; The minimum time is less than the lower time limit; and The maximum time is greater than the upper time limit.

6. The method for setting an equalizer according to claim 1, wherein: Wherein setting the continuous-time linear equalizer and the feedforward equalizer according to the optimal signal quality comprises: determining a set of optimal continuous-time linear equalizer settings for the continuous-time linear equalizer and a set of optimal tap coefficients for the feedforward equalizer according to the optimal signal quality; Setting the continuous-time linear equalizer according to the optimal continuous-time linear equalizer setting value; and The feedforward equalizer is set according to the set of optimal tap coefficient settings.

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