Continuous time linear equalizer based on low-pass and band-pass mixed structure

Abstract

The invention provides a continuous time linear equalizer based on a low-pass and band-pass mixed structure. The continuous time linear equalizer comprises a frequency selection coupler, a low-pass transconductance unit, a band-pass transconductance unit and a load unit. The frequency selection coupler is used for separating the differential analog signal into a first voltage component in a first band-pass frequency range and a second voltage component in a low-pass frequency range, the first band-pass frequency range comprises a target frequency expected to be compensated, and the frequency in the first band-pass frequency range is greater than the frequency in the low-pass frequency range; the band-pass transconductance unit is used for converting the first voltage component into current and synchronously realizing gain amplification to obtain a first current signal; the low-pass transconductance unit is used for converting the second voltage component into current and synchronously realizing gain amplification to obtain a second current signal; the load unit is used for summing the first current signal and the second current signal and converting the sum to a differential output voltage signal. According to the invention, the frequency corresponding to the gain peak point and the gain amplitude can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of integrated circuit design, and in particular to a continuous-time linear equalizer based on a low-pass and band-pass hybrid structure. BACKGROUND

[0002] With the vigorous development of information technology industries represented by artificial intelligence, Internet of Things and big data, higher requirements are put forward for data transmission between devices and chips. Under this background, high-speed serial interface (Serializer / Deserializer, SerDes) has attracted more and more attention due to its high transmission rate, low bit error rate and fewer pad usage, and has been gradually applied to many scenarios.

[0003] The receiver (Receiver, RX) of high-speed serial interface is mainly divided into Analog architecture and ADC-DSP (Analog-to-Digital Converter Digital Signal Processor) architecture. With the continuous evolution of process nodes, the RX of DSP architecture has more advantages than the traditional Analog architecture. However, regardless of which architecture is adopted, continuous-time linear equalization (Continuous Time Linear Equalizer, CTLE), feed-forward equalization (Feed-Forward Equalizer, FFE) and decision feedback equalization (Decision Feedback Equalizer, DFE) are needed. In the DSP architecture, FFE and DFE are completed in the digital domain, which is different from the implementation method in the Analog architecture, but regardless of whether it is in the Analog architecture or in the DSP architecture, the implementation method of CTLE and its role are consistent. In addition, as the first equalization of the signal after passing through the analog front-end (Analog Front-End, AFE), the equalization range, linearity and noise performance of CTLE will directly affect the quality of the signal in the subsequent link. Based on the above reasons, it is necessary to make a more in-depth and detailed analysis and research on CTLE.

[0004] The current mainstream CTLE structure mainly has a Gm-Tia (Transconductance amplifier Transimpedance Amplifier) structure and an RC source degeneration structure. However, with the continuous rise of the SerDes single-channel communication rate, the requirement for the CTLE equalization frequency range is also higher and higher. For example, for a receiver with a communication rate of 224 Gb / s and a PAM-4 modulation mode, the frequency of the peak point of the CTLE should be near 56 GHz, and due to the influence of the load capacitance, the transistor drain parasitic capacitance and the wiring parasitic capacitance, it is usually difficult to achieve the above goal by using the traditional CTLE structure. Therefore, how to effectively cope with the continuously rising frequency corresponding to the peak point of the CTLE is a problem to be solved. SUMMARY

[0005] The application provides a continuous-time linear equalizer based on a low-pass and band-pass hybrid structure, which can effectively solve the problems in the related art, and can weaken the influence of various parasitic capacitances and improve the frequency corresponding to the peak point of the gain in the amplitude-frequency characteristic curve of the CTLE and the amplitude of the gain.

[0006] A continuous-time linear equalizer based on a low-pass and band-pass hybrid structure, comprising a frequency selection coupler, a low-pass transconductance unit, a band-pass transconductance unit and a load unit, the output end of the frequency selection coupler is connected with the input end of the low-pass transconductance unit and the band-pass transconductance unit respectively, and the input end of the load unit is connected with the output end of the low-pass transconductance unit and the band-pass transconductance unit respectively. The frequency selection coupler is used for frequency separation of an input differential form analog signal to obtain a first voltage component signal and a second voltage component signal, the frequency of the first voltage component signal is located in a first band-pass frequency range, the first band-pass frequency range includes a target frequency to be compensated, and the frequency of the second voltage component signal is located in a low-pass frequency range, the frequency in the first band-pass frequency range is greater than the frequency in the low-pass frequency range. The band-pass transconductance unit is used for converting the first voltage component signal into a current and synchronously realizing gain amplification to obtain a first current signal. The low-pass transconductance unit is used for converting the second voltage component signal into a current and synchronously realizing gain amplification to obtain a second current signal. The load unit is used for summing the first current signal and the second current signal and performing current-to-voltage conversion processing to obtain a differential output voltage signal.

[0007] The continuous-time linear equalizer based on the low-pass and band-pass mixed structure comprises a frequency selective coupler, a band-pass transconductance unit, a low-pass transconductance unit and a first output terminal; The first frequency division module is configured to filter the first voltage component signal from the analog signal and transmit the first voltage component signal to the band-pass transconductance unit. The second frequency division module is configured to filter the second voltage component signal from the analog signal and transmit the second voltage component signal to the low-pass transconductance unit.

[0008] The first frequency division module comprises a tuning capacitor and a transformer. The tuning capacitor is configured to form an inductor-capacitor resonance network with a coil of the transformer, adjust the resonance frequency to the target frequency by changing the capacitance value of the tuning capacitor, and filter the first voltage component signal from the analog signal based on the adjusted inductor-capacitor resonance network. The transformer is configured to transmit the first voltage component signal to the band-pass transconductance unit.

[0009] The second frequency division module comprises a DC blocking capacitor, and the low-pass transconductance unit comprises an adjustable resistor and an adjustable capacitor. The DC blocking capacitor, the adjustable resistor and the adjustable capacitor form a composite filter network configured to filter the second voltage component signal from the analog signal.

[0010] The band-pass transconductance unit comprises a pair of first field effect transistors symmetrically connected in a differential pair. The pair of first field effect transistors are configured to convert the first voltage component signal into a current and realize gain amplification by the transconductance characteristic of the field effect transistor, thereby obtaining the first current signal.

[0011] The low-pass transconductance unit comprises a pair of second field effect transistors symmetrically connected in a differential pair, and the adjustable resistor and the adjustable capacitor are connected in parallel across the sources of the pair of second field effect transistors. The pair of second field effect tubes are used to convert the second voltage component signal into current and realize gain amplification by the transconductance characteristic of the field effect tube, and obtain the second current signal.

[0012] According to the continuous time linear equalizer based on the low-pass and band-pass hybrid structure provided in the application, the first frequency division module comprises a first filter network composed of a blocking capacitor and an inductor, the second frequency division module comprises a second filter network composed of a blocking capacitor and an inductor, and the parameters of the first filter network and the second filter network are different. The first filter network is used to screen the first voltage component signal from the analog signal and transmit the first voltage component signal to the band-pass transconductance unit. The second filter network is used to screen the second voltage component signal from the analog signal and transmit the first voltage component signal to the low-pass transconductance unit.

[0013] According to the continuous time linear equalizer based on the low-pass and band-pass hybrid structure provided in the application, the band-pass transconductance unit comprises a first band-pass transconductance unit, a signal adjustment circuit and a second band-pass transconductance unit. The first band-pass transconductance unit is used to convert the first voltage component signal into current and realize first-stage gain amplification by the transconductance characteristic of the field effect tube, and obtain a first-stage current signal. The signal adjustment circuit is used to at least convert the first-stage current signal from current to voltage, and obtain a converted voltage signal. The second band-pass transconductance unit is used to convert the converted voltage signal into current and realize second-stage gain amplification by the transconductance characteristic of the field effect tube, and obtain a second-stage current signal, wherein the second-stage current signal is the first-stage current signal.

[0014] According to the continuous time linear equalizer based on the low-pass and band-pass hybrid structure provided in the application, the signal adjustment circuit comprises a series resonance network composed of an inductor and a capacitor. The series resonance network is used to provide gain compensation for the first-stage current signal.

[0015] According to the continuous time linear equalizer based on the low-pass and band-pass hybrid structure provided in the application, the continuous time linear equalizer further comprises a middle-pass transconductance unit, the frequency selection coupler further comprises a third frequency division module, the output end of the third frequency division module is further connected with the input end of the middle-pass transconductance unit, and the input end of the load unit is further connected with the output end of the middle-pass transconductance unit. The third frequency division module is configured to filter a third voltage component signal from the analog signal and transmit the third voltage component signal to the middle-pass transconductance unit, where the third voltage component signal has a frequency within a second band-pass frequency range, and the frequency within the second band-pass frequency range is greater than the frequency within the low-pass frequency range and less than the frequency within the first band-pass frequency range. The middle-pass transconductance unit is further configured to convert the third voltage component signal into a current and synchronously implement gain amplification to obtain a third current signal. The load unit is configured to sum the first current signal, the second current signal and the third current signal and convert the sum into a voltage to obtain the differential output voltage signal.

[0016] In the continuous-time linear equalizer based on the low-pass and band-pass hybrid structure in the present application, the frequency selection coupler divides the input differential analog signal into a first voltage component signal with high frequency and a second voltage component signal with low frequency, so that the high frequency signal and the low frequency signal are processed separately, and the signals after separation only flow through the circuit path corresponding to the bandwidth. The parasitic capacitance of each path only needs to process the signal of the corresponding frequency band, which is equivalent to splitting the total parasitic capacitance into different channels according to the frequency band, and the effective capacitance load of each channel is equivalent to reduce. For example, the parasitic capacitance of the band-pass path only affects the high frequency signal, and the high frequency signal is no longer affected by the parasitic capacitance of the low-pass path, so the influence of various parasitic capacitances can be weakened. In addition, the parasitic capacitance of the band-pass path is reduced due to path segmentation, that is, the load capacitance (including parasitic capacitance) of the band-pass transconductance unit is reduced due to path segmentation, which can improve the cutoff frequency of the high frequency response of the band-pass transconductance unit, so as to make the peak value of the gain of the equalizer shift to a higher frequency, and finally achieve the effect of improving the frequency corresponding to the peak value of the gain. Further, the band-pass transconductance unit converts the first voltage component signal with high frequency into a current and synchronously implements gain amplification, that is, the conversion itself is also a process of improving the gain, so the present application can also significantly improve the amplitude of the gain (i.e. the maximum gain) corresponding to the peak value of the gain. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0018] Figure 1 is a schematic diagram of the research results of the CTLE in the conventional scheme according to an embodiment of the present application; Figure 2is a system structure block diagram of a continuous-time linear equalizer based on a low-pass and band-pass hybrid structure according to an embodiment of the present application; Figure 3 is a circuit structure schematic diagram of a first CTLE according to an embodiment of the present application; Figure 4 is a circuit structure schematic diagram of a second CTLE according to an embodiment of the present application; Figure 5 is a circuit structure schematic diagram of a third CTLE according to an embodiment of the present application; Figure 6 is a frequency-amplitude characteristic curve schematic diagram of a CTLE based on a low-pass and band-pass hybrid structure according to an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below with reference to the drawings in the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0020] In wired communication, data signals are usually baseband signals, so the frequency-amplitude characteristic response curves of CTLEs all present low-pass characteristics. When high-speed signals pass through physical channels (such as PCB traces, cables) and receiver front-end circuits (AFE), serious high-frequency attenuation occurs. The skin effect, dielectric loss of the physical medium and the parasitic capacitance of the circuit will act like a low-pass filter, causing greater weakening of high-frequency components than low-frequency components of the signal. In order to solve the problem of high-frequency attenuation, CTLE is designed as a reverse filter, which provides a small gain at low frequencies but a significant gain peak near the critical high-frequency region (i.e. the Nyquist frequency). The Nyquist frequency is the highest effective frequency contained in the digital signal. By making accurate compensation at this frequency point, the CTLE can pull the attenuated high-frequency components back to the normal level, thereby restoring the integrity of the signal. The compensation principle can be shown as in part a of Figure 1 Figure 1 is a research result schematic diagram about CTLE in a conventional scheme according to an embodiment of the present application.

[0021] In Figure 1 ​In part a, H(s) is the transfer function describing the frequency characteristics of the system (e.g., a channel or CTLE), and its magnitude |H(s)| specifically represents the system's amplification capability for signals of different frequencies, i.e., gain. The AFE output state curve represents the state of the signal after passing through the analog front-end (AFE) before reaching the CTLE. As the frequency increases, its gain decreases rapidly, indicating that the high-frequency components of the signal are severely attenuated. The CTLE curve represents the frequency response of the CTLE itself, and its characteristics are exactly the opposite of the AFE output state curve. It has low gain at low frequencies but a significant peak in the high-frequency region. The position and height of this peak can be carefully designed to precisely match and compensate for the high-frequency attenuation portion of the AFE output state curve. The post-compensation effect curve represents the final overall effect of the signal after being attenuated by the channel (corresponding to the AFE output state curve) and then compensated by the CTLE. Since the peak of the CTLE fills the channel attenuation, the final post-compensation effect curve becomes flatter, and its effective bandwidth is much higher than the original AFE output state curve. This means that after equalization, the entire system can support higher frequency signal transmission.

[0022] Next Figure 1 Taking the traditional RC source degenerate structure shown in part b as an example, the working principle of CTLE is explained.

[0023] exist Figure 1 In part b, This represents the positive terminal of the differential input signal. This represents the negative terminal of the differential input signal. This represents the positive terminal of the differential output signal. This represents the negative terminal of the differential output signal. Indicates the load resistance. Indicates the source degenerate resistance. This represents the sum of the load capacitance, transistor drain parasitic capacitance, and some trace parasitic capacitances. This represents the source-degenerate capacitance. The transfer function used by CTLE for the RC source-degenerate structure on the left is: This is a single zero point ( ), double poles ( , The system's zeros and poles are defined as follows: Zeros increase system gain; beyond the zero frequency, the system gain begins to rise. Poles decrease system gain; beyond the pole frequency, the system gain begins to fall. The frequencies corresponding to the zeros and poles of this system are... , , In order: By reasonably controlling the values of the various electronic devices in the circuit, the amplitude-frequency characteristic response curve can be made as shown in FIG. 1, i.e. the peak point of the gain corresponds to a frequency between 56GHz and 60GHz. Figure 1

[0024] In combination with part c of FIG. 1, when the frequency is less than 56GHz, the gain is low and flat; after the frequency exceeds 56GHz, the gain starts to rise; when the frequency exceeds 60GHz, the rising trend of the gain ends. Between 56GHz and 60GHz, the circuit reaches its maximum gain, forming a peak. After the frequency exceeds 60GHz, the gain rapidly decreases. Figure 1

[0025] However, as the single-channel communication rate of SerDes continues to rise, the requirements for the CTLE equalization frequency range are also increasing. For example, for a receiver using PAM-4 modulation at a communication rate of 224Gb / s, the peak point of the gain of the CTLE should correspond to a frequency near 56GHz. Due to the influence of load capacitance, transistor drain parasitic capacitance, and some parasitic capacitance of the wiring, it is difficult to achieve this target. For example, in FIG. 1, An increase will cause to decrease, causing the peak frequency to shift to low frequency.

[0026] To overcome the above problems, the structure based on inductance for bandwidth expansion shown in part d of FIG. 1 is used in the related art. However, due to the influence of parasitic capacitance in the structure based on inductance for bandwidth expansion, it is still difficult to achieve this target. Specifically, as shown in part e of FIG. 1, these parasitic capacitances include Figure 1 Figure 1 is the sum of the load capacitance, the transistor drain parasitic capacitance, and some parasitic capacitance of the wiring, is the sum of the transistor source capacitance, the resistance parasitic capacitance, and some parasitic capacitance of the wiring. If increases, then will decrease, and if increases, it is equivalent to increasing , causing and to decrease, ultimately causing the overall amplitude-frequency response to move to low frequency, causing the frequency corresponding to the gain peak point to decrease, which cannot meet the use requirements.

[0027] ​​​​​​​​​​​​​​​The application proposes a new circuit structure of the CTLE, which adopts a low-pass and band-pass mixed structure and can solve the problems mentioned in the related art. Next, the continuous-time linear equalizer based on the low-pass and band-pass mixed structure of the application will be described in detail.

[0028] Figure 2 is a system structure block diagram of a continuous-time linear equalizer based on a low-pass and band-pass mixed structure according to an embodiment of the application. Referring to Figure 2 , the continuous-time linear equalizer based on the low-pass and band-pass mixed structure of the application includes a frequency selection coupler, a low-pass transconductance unit, a band-pass transconductance unit and a load unit, the output end of the frequency selection coupler is connected with the input end of the low-pass transconductance unit and the band-pass transconductance unit respectively, and the input end of the load unit is connected with the output end of the low-pass transconductance unit and the band-pass transconductance unit respectively.

[0029] The frequency selection coupler is used to perform frequency separation on the input differential form analog signal to obtain a first voltage component signal and a second voltage component signal, the frequency of the first voltage component signal is located in a preset first band-pass frequency range, the target frequency expected to be compensated is included in the first band-pass frequency range, and the frequency of the second voltage component signal is located in a preset low-pass frequency range, the frequency in the first band-pass frequency range is greater than the frequency in the low-pass frequency range.

[0030] In the application, the analog front end inputs a differential analog signal to the frequency selection coupler, and the frequency selection coupler separates the differential analog signal into a high-frequency voltage component signal (i.e. the first voltage component signal) and a low-frequency voltage component signal (i.e. the second voltage component signal). Figure 2 In the application, the high-frequency component is the first voltage component signal, and the low-frequency component is the second voltage component signal.

[0031] Among them, the first band-pass frequency range and the low-pass frequency range can be set according to actual needs (i.e. not a fixed frequency range), only the type of each electronic device used in the frequency selection coupler needs to be selected, so that it can realize the screening of signals in the first band-pass frequency range and the low-pass frequency range.

[0032] Among them, the target frequency expected to be compensated in the first band-pass frequency range can be 56GHz, or other values, which can be set according to actual needs.

[0033] The band-pass transconductance unit is used to convert the first voltage component signal into a current and synchronously realize gain amplification to obtain a first current signal.

[0034] The band-pass transconductance unit is used to convert the first voltage component signal into a current and synchronously realize gain amplification to obtain a first current signal. Figure 2Gm unit (bandpass) in the bandpass transconductance unit is mainly used for converting the first voltage component signal into current (while converting, gain amplification is realized), to obtain the converted current signal, that is, the first current signal. In various embodiments of the present application, the gain, that is, the gain represented by the ordinate in the amplitude-frequency characteristic curve.

[0035] The low-pass transconductance unit is used for converting the second voltage component signal into current and realizing gain amplification at the same time, to obtain the second current signal.

[0036] The low-pass transconductance unit is used for converting the second voltage component signal into current and realizing gain amplification at the same time, to obtain the second current signal. Figure 2 Gm unit (low-pass) in the low-pass transconductance unit is mainly used for converting the second voltage component signal into current (while converting, gain amplification is realized), to obtain the converted current signal, that is, the second current signal.

[0037] In the present application, the bandpass transconductance unit and the low-pass transconductance unit can use the same structure or different structures. When the same structure is used, the model or parameters of the selected electronic device can be the same or different, which is specifically set according to actual needs, and the present application does not make specific limitations.

[0038] The load unit is used for summing the first current signal and the second current signal and current-to-voltage conversion processing, to obtain a differential output voltage signal.

[0039] In the present application, the load unit is the load in Figure 2 The load unit is mainly used for summing the first current signal and the second current signal, and converting the summed signal into a differential output voltage signal. The differential output voltage signal can be provided for use by subsequent other modules.

[0040] The continuous-time linear equalizer based on the low-pass and bandpass hybrid structure of the present application can weaken the influence of various parasitic capacitances, and the reasons include at least: First, the frequency-selective coupler divides the input signal into a first voltage component signal of high frequency and a second voltage component signal of low frequency, so that the high-frequency signal and the low-frequency signal are processed separately, and the separated signals only flow through the circuit path of the corresponding bandwidth, which can avoid the excitation of the total parasitic capacitance by the full-bandwidth signal, and effectively reduce the effective capacitance load of each channel. The parasitic capacitance of each path only needs to process the signal of the corresponding frequency band, which is equivalent to splitting the total parasitic capacitance into different channels according to the frequency band, and the effective capacitance load of each channel is equivalent to being reduced. For example, the parasitic capacitance of the bandpass path only affects the high-frequency signal, and the high-frequency signal is no longer affected by the shunt of the low-pass path parasitic capacitance (because the low-frequency path has high impedance to the high-frequency signal), and the parasitic capacitance of the low-pass path only affects the low-frequency signal.

[0041] Second, the current domain processing mechanism is adopted, and the bandpass / lowpass transconductance unit converts the voltage into current, and the load unit sums the current signals. The sensitivity of the current signal to the parasitic capacitance during transmission is lower than that of the voltage signal (because the output impedance of the current source is high), which can indirectly weaken the influence of the parasitic capacitance.

[0042] The continuous-time linear equalizer based on the low-pass and band-pass hybrid structure in the present application can effectively improve the frequency corresponding to the gain peak point, and the reasons include at least: First, the parasitic capacitance of the bandpass path is reduced due to path segmentation, that is, the load capacitance (including parasitic capacitance) of the bandpass transconductance unit is reduced due to path segmentation, which can improve the cutoff frequency of its high-frequency response, thereby making the gain peak of the equalizer shift to a higher frequency.

[0043] Second, on the basis of weakening the influence of various parasitic capacitances, the bandpass transconductance unit is only responsible for processing the first voltage component signal of high frequency, which can compensate for the target frequency (for example, 56GHz) and avoid the interference of low-frequency signals, thereby improving the purity of the frequency corresponding to the gain peak point.

[0044] In addition, the bandpass transconductance unit converts the first voltage component signal of high frequency into current and simultaneously realizes the amplification of gain, that is, the conversion itself is also a gain improvement process, so it can significantly improve the amplitude of the gain corresponding to the gain peak point.

[0045] In combination with the above embodiments, in an implementation manner, the frequency-selective coupler includes a first frequency division module and a second frequency division module, an output end of the first frequency division module is connected with an input end of the bandpass transconductance unit, and an output end of the second frequency division module is connected with an input end of the low-pass transconductance unit.

[0046] The first frequency division module is used for screening the first voltage component signal from the analog signal and transmitting the first voltage component signal to the bandpass transconductance unit.

[0047] The second frequency division module is used for screening the second voltage component signal from the analog signal and transmitting the second voltage component signal to the low-pass transconductance unit.

[0048] In the present application, two independent frequency division modules, i.e., the first frequency division module and the second frequency division module, are arranged in the frequency-selective coupler. The task of screening the first voltage component signal can be realized by means of the first frequency division module, and the task of screening the second voltage signal can be realized by means of the second frequency division module.

[0049] The internal circuits of the first frequency division module and the second frequency division module can be set according to actual needs, and the present application does not limit this.

[0050] In the present application, the first frequency division module is responsible for screening the first voltage component signal of the high frequency band and transmitting it to the band-pass transconductance unit, and the second frequency division module is responsible for screening the second voltage component signal of the low frequency band and transmitting it to the low-pass transconductance unit, which makes the high frequency and low frequency signals be divided into independent paths in the input stage, avoids the frequency band coupling interference (such as the interference of low frequency signal on high frequency compensation) generated when the mixed signal is transmitted in the same circuit, and improves the accuracy of the subsequent band-pass transconductance unit for target frequency compensation.

[0051] In the present application, based on the framework shown in Figure 2 , three related CTLE circuit structures are designed, as shown in Figures 3-5 . Figure 3 is a first CTLE circuit structure diagram shown in an embodiment of the present application. Figure 4 is a second CTLE circuit structure diagram shown in an embodiment of the present application. Figure 5 is a third CTLE circuit structure diagram shown in an embodiment of the present application.

[0052] In the following Figure 3 , the first CTLE circuit structure will be introduced.

[0053] Referring to Figure 3 , the first frequency division module includes a tuning capacitor and a transformer (connected to two coils after ); the tuning capacitor is used to form an inductor-capacitor resonant network with the coil of the transformer, adjust the resonant frequency to the target frequency by changing its own capacitance value, and screen the first voltage component signal from the analog signal based on the adjusted inductor-capacitor resonant network.

[0054] The transformer is used to transmit the first voltage signal to the band-pass transconductance unit.

[0055] In Figure 3 , since the input analog signal is a differential signal, the upper tuning capacitor is used to receive the positive-phase analog signal, and the lower tuning capacitor is used to receive the negative-phase analog signal.

[0056] In actual use, by selecting a tuning capacitor and a transformer of a suitable model, by changing the capacitance value of the tuning capacitor , the resonant frequency is adjusted to the target frequency of the expected compensation, so that the adjusted inductor-capacitor resonant network (i.e. LC resonant network) can screen the first voltage component signal of high frequency from the analog signal.

[0057] In Figure 3 , the tuning capacitor ​ For the DC bias voltage, and and The DC bias resistance is connected, and the two work together to ensure that the corresponding electronic device works stably.

[0058] In Figure 3 , the analog front end (AFE) includes inductance, diode and resistance . The inductance is used to realize impedance matching (a low-pass filter is formed with the rear-stage capacitor to match the input impedance and reduce signal reflection) and noise suppression (high-frequency noise is filtered out to improve the signal-to-noise ratio of the input signal). The diode is used to provide electrostatic discharge protection, that is, when high-voltage static electricity appears at the input port, the diode is turned on to discharge the static electricity current to the ground to protect the rear-stage circuit. The resistance is used to realize differential impedance matching and common-mode noise suppression. The differential impedance matching refers to providing a differential terminal load to match the transmission line impedance and reduce reflection. The common-mode noise suppression refers to presenting high impedance to the common-mode noise (because there is no potential difference between the two ends of the differential resistance for the common-mode signal) and only providing matching for the differential-mode signal. In actual implementation, the circuit structure of the analog front end (AFE) can also be set to other types according to actual needs, and the present application does not limit this.

[0059] In Figure 3 , the second frequency division module includes a DC blocking capacitor , and the low-pass transconductance unit includes an adjustable resistance and an adjustable capacitor. The DC blocking capacitor , the adjustable resistance and the adjustable capacitor constitute a composite filter network, and the composite filter network is used to screen the second voltage component signal from the analog signal.

[0060] In the present application, by selecting a DC blocking capacitor , an adjustable resistance and an adjustable capacitor of a suitable model, or adjusting the parameter values of the DC blocking capacitor , the adjustable resistance and the adjustable capacitor to reasonable parameters, the DC blocking capacitor , the adjustable resistance and the adjustable capacitor can effectively screen the low-frequency second voltage component signal from the analog signal when they work cooperatively.

[0061] In the present application, the second voltage component signal screened by the second frequency division module is a signal containing a low-frequency signal, that is, a signal used to obtain a low-frequency signal, which can not be the final low-frequency signal that needs to be processed in a strict sense, and the second frequency division module can cooperate with the electronic devices in the low-pass transconductance unit to realize the screening of the final low-frequency signal. The second frequency division module described in the foregoing is used to screen the second voltage component signal from the analog signal, which means that the first frequency division module can be used in the process of screening the second voltage component signal.

[0062] Refer to Figure 3, the band-pass transconductance unit includes a pair of first field effect tubes, and the pair of first field effect tubes are symmetrically connected in the form of a differential pair. The pair of first field effect tubes are used to synchronously convert the first voltage component signal into a current and realize gain amplification through the transconductance characteristic of the field effect tube, so as to obtain a first current signal.

[0063] In the present application, the pair of first field effect tubes synchronously convert the first voltage component signal into a current and realize gain amplification through the transconductance value of the field effect tube. .

[0064] Among them, reflects the control ability of the gate voltage to the drain current, and the formula is: , is the drain current change amount, is the gate-source voltage change amount.

[0065] In the band-pass transconductance unit, the value of the first field effect tube can be selected to realize the value of the first field effect tube.

[0066] Referring to Figure 3 , the low-pass transconductance unit includes a pair of second field effect tubes, and the pair of second field effect tubes are symmetrically connected in the form of a differential pair. The adjustable resistance and the adjustable capacitance are connected in parallel between the sources of the pair of second field effect tubes; the pair of second field effect tubes are used to synchronously convert the second voltage component signal into a current and realize gain amplification through the transconductance characteristic of the field effect tube, so as to obtain a second current signal.

[0067] In the present application, in the low-pass transconductance unit, the value of the second field effect tube can also be selected to realize the value of the second field effect tube.

[0068] In actual implementation, the high-pass transconductance unit and the low-pass transconductance unit can adopt the same circuit structure, or can adopt different circuit structures. In other words, the high-pass transconductance unit and the low-pass transconductance unit can both adopt the circuit structure of the high-pass transconductance unit shown in Figure 3 , or can both adopt the circuit structure of the low-pass transconductance unit shown in Figure 3 . As for the specific type of the device selected in the high-pass transconductance unit and the low-pass transconductance unit, it can be determined according to actual needs.

[0069] In Figure 3 , the circles with downward arrows in the band-pass transconductance unit and the low-pass transconductance unit represent tail current sources, which are used to provide constant direct current bias current for the two transistors.

[0070] In the present application, the CTLE adopts the circuit structure as shown in Figure 4The circuit structure shown can significantly improve the frequency corresponding to the peak point and the maximum amplitude size corresponding to the peak point. For improving the frequency corresponding to the peak point, the reason is as follows: by adjusting the physical structure of the transformer to control its LC resonance characteristics, the gain peak can be accurately positioned at the target frequency (such as the Nyquist frequency) that needs to be compensated. For improving the maximum amplitude size corresponding to the peak point, the reason is as follows: by the two-stage gain of the transformer and the band-pass transconductance unit. The transformer provides a first-stage voltage gain when resonating, and the band-pass transconductance unit further performs a second-stage transconductance gain, finally realizing a high-amplitude peak. Specifically, while screening high-frequency signals, the transformer uses its LC resonance characteristics to generate a voltage gain at the resonance frequency point. That is, at that specific frequency point, the voltage amplitude of the secondary coil (output end) of the transformer is greater than that of the primary coil (input end). Therefore, the voltage signal with a peak received by the band-pass transconductance unit has been pre-amplified. After receiving the voltage signal that has been amplified, the band-pass transconductance unit performs voltage-to-current conversion, which is also a gain process, and the gain size is determined by the transconductance value of the band-pass transconductance unit . Therefore, the greater the gm value, the greater the output current for the same input voltage.

[0071] The second circuit structure will be introduced below. Figure 4 The second circuit structure will be introduced below.

[0072] Referring to Figure 4 , the first frequency division module includes a first filter network composed of a blocking capacitor and an inductor, the second frequency division module includes a second filter network composed of a blocking capacitor and an inductor, and the parameters of the first filter network and the second filter network are different; the first filter network is used to screen a first voltage component signal from the analog signal and transmit the first voltage component signal to the band-pass transconductance unit; and the second filter network is used to screen a second voltage component signal from the analog signal and transmit the first voltage component signal to the low-pass transconductance unit.

[0073] Specifically, the first filter network includes a blocking capacitor and an inductor , through which the first voltage component signal with high frequency in the analog signal can be transmitted to the unit. The second filter network includes a blocking capacitor and an inductor , through which the second voltage component signal with low frequency in the analog signal can be transmitted to the unit. The connection form of each electronic element is as shown in Figure 4 .

[0074] In Figure 3 , the band-pass transconductance unit includes a first band-pass transconductance unit , signal adjusting circuit and second band-pass transconductance unit ; the first band-pass transconductance unit is configured to convert the first voltage component signal into current synchronously and realize first-stage gain amplification by the transconductance characteristic of a field effect tube, so as to obtain a first-stage current signal; the signal adjusting circuit is configured to at least convert the first-stage current signal from current to voltage, so as to obtain a converted voltage signal; and the second transconductance unit is configured to convert the converted voltage signal into current synchronously and realize second-stage gain amplification by the transconductance characteristic of a field effect tube, so as to obtain a second-stage current signal, which is the first current signal.

[0075] In XL , the signal adjusting circuit comprises a series resonance network composed of an inductor and a capacitor. The part in the black box between the first transconductance unit and the second transconductance unit constitutes the signal adjusting circuit.

[0076] The signal adjusting circuit comprises a series resonance network composed of an inductor and a capacitor.

[0077] Specifically, in the signal adjusting circuit, is a peak inductance, is a corresponding capacitor, which constitute a high-frequency selection and tuning network, and the impedance characteristics of the inductor and the capacitor at high frequencies are used to realize resonance peak compensation of high-frequency signals, improve the gain of high-frequency signals, and make the circuit have a better balance effect in the high-frequency band (near the target frequency). XC increases with the increase of frequency, Figure 4 decreases with the increase of frequency. and constitute the series resonance network.

[0078] is a peak capacitance, and etc. are used to accurately adjust the resonance frequency point and the peak gain of the high-frequency band, so that the circuit amplitude-frequency characteristic forms a suitable peak at the high frequency that needs to be compensated, and the compensation ability for channel high-frequency attenuation is enhanced.

[0079] is a common-mode voltage, which provides a stable common-mode working point for the high-frequency transconductance unit, ensures the symmetry of the upper and lower branches in the differential circuit, improves the common-mode rejection ratio of the circuit, reduces common-mode noise interference, and ensures the accuracy of high-frequency signal processing.

[0080] is configured to provide a direct current bias path, stabilize the direct current working point, and cooperate with other devices to adjust the amplitude, frequency response, etc. of the high-frequency signal.

[0081] In Gm , the low-pass transconductance unit also comprises a first low-pass transconductance unit​ , signal adjusting circuit and second low-pass transconductance unit ; the first low-pass transconductance unit is used for synchronously converting the second voltage component signal into current and realizing first-stage gain amplification through the transconductance characteristic of a field effect tube, so as to obtain a first-stage current signal; the signal adjusting circuit is used for at least adjusting the first-stage current signal to realize current-to-voltage conversion, so as to obtain a converted voltage signal; and the second low-pass transconductance unit is used for synchronously converting the converted voltage signal into current and realizing second-stage gain amplification through the transconductance characteristic of a field effect tube, so as to obtain a second-stage current signal, which is the second current signal.

[0082] is a load inductance, is a load-end parasitic or configured capacitance, both of which constitute a load-end resonant or frequency-selective network, which can adjust the impedance characteristic of the load and match the output impedance of the unit, so as to optimize the transmission and amplification effect of low-frequency signals at the load end.

[0083] is a load resistance, which provides a direct-current bias path for the circuit, ensures the direct-current working point of the unit, and cooperates with the inductance and the capacitance to affect the amplitude and frequency response of the signal, adjust the gain and bandwidth of the circuit and the like.

[0084] is a direct-current power supply, which provides a direct-current voltage required by the entire low-pass Figure 4 unit link, and ensures that the transistors and the like are in a normal conduction and amplification working state.

[0085] Secondly, in the analog front end of the circuit shown in Figure 4 , the diode plays a role of signal receiving and preliminary rectification, can preliminarily process the input radio frequency signal and the like, extract effective signal components, and also has a certain limiting amplitude and protection function for the subsequent circuit. The inductance is mainly used for filtering and impedance matching, the filtering can filter out part of the stray interference in the signal, and the impedance matching can make the signal enter the subsequent circuit more efficiently from the transmission path, and reduce signal reflection loss. The resistance is used as a terminal matching resistance, for adjusting the impedance of the signal, so that the entire front-end input impedance is adapted to the characteristic impedance of the transmission line, ensures stable signal transmission, and avoids problems such as signal reflection and attenuation caused by impedance mismatching.

[0086] In the output stage circuit of the circuit shown in Gm , constitutes an output load network, is a resonant or filtering capacitance, is a load resistance, ​​is the load inductance, the three work together to process the current signal from the cascade Figure 4 The unit converts the current signal into a voltage signal output, and further filters and shapes the signal to meet the needs of the subsequent circuit. It can also adjust the bandwidth and impedance matching of the output signal.

[0087] is the parasitic capacitance of the solder pad, which affects the signal. is the electrostatic protection capacitor, mainly used for electrostatic protection. When there is an electrostatic shock, the electrostatic charge can be discharged to protect the internal circuit from static damage. is the parasitic capacitance (Parasitic Capacitance).

[0088] is the transmission line inductance (or coil inductance), which plays a role in impedance matching and signal transmission. It can adjust the impedance of the output stage to match the internal circuit output impedance with the external load, reduce signal reflection, and improve signal transmission efficiency. It also has certain signal delay and phase adjustment functions.

[0089] is the terminal matching resistance, used to adjust the impedance matching of the output stage, so that the entire output signal can be transmitted to the external AC coupling circuit and subsequent load stably and efficiently, avoiding signal reflection, oscillation, and other problems.

[0090] The external AC coupling (Outside AC-coupled) capacitor is located in the external AC coupling and is connected to , used to further isolate DC and couple AC signals, allowing only the AC signal processed by the previous stages (including the balanced low-frequency and high-frequency combined signal) to be transmitted to the subsequent circuit, while filtering out the remaining DC components and low-frequency noise to some extent, ensuring the purity of the output signal.

[0091] In Figure 4 , the signal adjustment circuit finely controls low / high-frequency signals, and the output stage focuses on signal synthesis, external adaptation, and protection filtering, which can jointly ensure the equalization compensation and high-quality output of CTLE for high-speed signals.

[0092] In Figure 3 , the structure inside each Gm unit can refer to the structure provided in the bandpass transconductance unit or low-pass transconductance unit. Figure 5

[0093] The third circuit structure will be introduced below in combination with Figure 5 .

[0094] Figure 5 ​The frequency selection coupler further comprises a third frequency division module, and an input end of the third frequency division module is connected with the input end of the mid-pass transconductance unit, and an input end of the load unit is connected with an output end of the mid-pass transconductance unit.

[0095] The third frequency division module is configured to filter a third voltage component signal from the analog signal, and transmit the third voltage component signal to the mid-pass transconductance unit, the third voltage component signal having a frequency within a preset second band-pass frequency range, the frequency within the second band-pass frequency range being greater than a frequency within the low-pass frequency range and less than a frequency within the first band-pass frequency range.

[0096] The mid-pass transconductance unit is further configured to convert the third voltage component signal into a current and synchronously implement gain amplification to obtain a third current signal.

[0097] The load unit is configured to sum the first current signal, the second current signal and the third current signal, and convert the sum into a voltage to obtain a differential output voltage signal.

[0098] In the frequency selection coupler, Figure 5 Vb1 and Vb2 are DC bias voltage sources, which provide DC bias for related nodes in the frequency selection coupler to stabilize the working point.

[0099] As a terminal matching resistor, the resistor adjusts the output impedance of the frequency selection coupler to adapt to the input impedance of the subsequent Gm unit, reduces signal reflection, and improves signal transmission efficiency.

[0100] In the frequency selection coupler, the transformer comprises a primary coil and a secondary coil . The differential analog signal from the analog front end passes through the primary coil and the DC blocking capacitor to enter the low-pass transconductance unit Gm1 (SD), which is responsible for converting the input voltage component signal into a current and synchronously implementing gain amplification to obtain a second current signal. The differential analog signal from the analog front end passes through the primary coil , the inductor and the capacitor to enter the mid-pass transconductance unit Gm2, which is responsible for converting the input voltage component signal into a current and synchronously implementing gain amplification to obtain a third current signal. The differential analog signal from the analog front end passes through the secondary coil to enter the high-pass transconductance unit Gm3, which is responsible for converting the input voltage component signal into a current and synchronously implementing gain amplification to obtain a first current signal.

[0101] In the frequency selection coupler, VbIn the analog front end, the diode realizes signal receiving and preliminary rectification, extracts effective signal components, has the functions of limiting and protecting the subsequent circuit, and can resist excessive instantaneous signal impact. The inductor plays the roles of filtering and impedance matching. The filtering can remove part of the stray interference in the signal; the impedance matching ensures that the signal is efficiently transmitted from the transmission path to the subsequent circuit, reduces signal reflection loss, and ensures stable signal transmission. Figure 5 3. A direct current bias voltage is provided, and a series resistor is used to adjust the bias current. The two work together to set a suitable direct current working point for the analog front end device, ensuring that the diode, inductor and other devices work in a stable state.

[0102] The output part includes and , which work together to realize signal synthesis and conversion, synthesize the current signals of different frequencies output by each transconductance unit, and convert the synthesized current signals into differential output voltage signals.

[0103] In Figure 3 , the structure inside each Gm unit can be set according to the structure inside the bandpass transconductance unit or low-pass transconductance unit provided in Figure 5 .

[0104] Using the circuit shown in Figure 6 , the first aspect can compensate for the loss of different frequency bands: the attenuation of the channel to the signal changes with frequency (high-frequency attenuation is usually more severe), after being divided into three paths, Gm1 (LF), Gm2 (MF), and Gm3 (HF) can independently adjust the gain of each frequency band, accurately compensate for the loss difference of low-frequency, medium-frequency, and high-frequency signals, and make the full-band signal more accurate. The second aspect can suppress the interference between frequency bands. Different frequency signals can produce crosstalk in the same path. The split processing reduces the mutual interference of low-frequency, medium-frequency, and high-frequency signals, and improves the signal purity. The third aspect can adapt to the characteristics of multiple channels. The frequency response of the actual channel (such as the PCB trace) is complex. The three-path structure can adjust the parameters (transconductance, load) of each Gm unit to flexibly adapt to the attenuation curve of different channels, and can widen the compatibility of the circuit for various application scenarios.

[0105] In summary, the CTLE based on the low-pass-bandpass hybrid structure proposed in this application has at least two advantages compared to the traditional scheme: (1) The frequency corresponding to the gain peaking point of the CTLE is increased, so that it can be applied to a wired receiver with higher transmission rate.

[0106] (2) The maximum gain amplitude corresponding to the gain peaking point of the CTLE is increased, so that it can be applied to a wired communication application with larger transmission loss.

[0107] The CTLE of the hybrid structure of the present application has an overall amplitude-frequency characteristic curve as shown in Figure 6 Compared with the structure with only low frequency components, the hybrid structure has significant improvement in both the frequency of the gain peaking point and the maximum gain amplitude. ​ is a schematic diagram of the amplitude-frequency characteristic curve of a CTLE based on a low-pass and band-pass hybrid structure according to an embodiment of the present application.

[0108] From the above description of the embodiments, those skilled in the art can clearly understand that the embodiments can be implemented by means of software plus necessary universal hardware platforms, and of course, can also be implemented by hardware. Based on such understanding, the above technical solutions, essentially or in other words, the part of the prior art that makes a contribution, can be embodied in the form of a software product, which can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods of the embodiments or some parts of the embodiments.

[0109] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for some technical features therein; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A continuous-time linear equalizer based on a low-pass and band-pass hybrid structure, characterized by, The frequency selection coupler, the low-pass transconductance unit and the band-pass transconductance unit, and the load unit are connected in series. The frequency selection coupler is configured to separate the input analog signal in differential form into a first voltage component signal and a second voltage component signal, the first voltage component signal has a frequency within a first band-pass frequency range, the first band-pass frequency range includes a target frequency to be compensated, and the second voltage component signal has a frequency within a low-pass frequency range, the frequency within the first band-pass frequency range is greater than the frequency within the low-pass frequency range. The band-pass transconductance unit is configured to convert the first voltage component signal into a current and simultaneously implement gain amplification to obtain a first current signal. The low-pass transconductance unit is configured to convert the second voltage component signal into a current and simultaneously implement gain amplification to obtain a second current signal. The load unit is configured to sum the first current signal and the second current signal and convert the sum into a differential output voltage signal.

2. The continuous-time linear equalizer based on a hybrid lowpass and bandpass structure according to claim 1, characterized by The frequency selection coupler includes a first frequency division module and a second frequency division module, the output end of the first frequency division module is connected to the input end of the band-pass transconductance unit, and the output end of the second frequency division module is connected to the input end of the low-pass transconductance unit. The first frequency division module is configured to filter the first voltage component signal from the analog signal and transmit the first voltage component signal to the band-pass transconductance unit. The second frequency division module is configured to filter the second voltage component signal from the analog signal and transmit the second voltage component signal to the low-pass transconductance unit.

3. The continuous-time linear equalizer based on a hybrid low-pass and band-pass structure according to claim 2, characterized by The first frequency division module includes a tuning capacitor and a transformer. The tuning capacitor is configured to form an inductor-capacitor resonance network with the coil of the transformer, adjust the resonance frequency to the target frequency by changing the capacitance value of the tuning capacitor, and filter the first voltage component signal from the analog signal based on the adjusted inductor-capacitor resonance network. The transformer is configured to transmit the first voltage component signal to the band-pass transconductance unit.

4. The continuous-time linear equalizer based on a hybrid lowpass and bandpass structure according to claim 2, characterized by The second frequency division module includes a DC blocking capacitor, and the low-pass transconductance unit includes an adjustable resistor and an adjustable capacitor. The DC blocking capacitor, the adjustable resistor and the adjustable capacitor form a composite filter network, and the composite filter network is configured to filter the second voltage component signal from the analog signal.

5. The continuous-time linear equalizer based on a hybrid lowpass and bandpass structure according to claim 1, characterized by The band-pass transconductance unit includes a pair of first field effect transistors, and the pair of first field effect transistors are symmetrically connected in the form of a differential pair. The pair of first field effect transistors are configured to convert the first voltage component signal into a current and implement gain amplification simultaneously by the transconductance characteristic of the field effect transistor to obtain the first current signal.

6. The continuous-time linear equalizer based on a hybrid low-pass and band-pass structure according to claim 4, characterized by The low-pass transconductance unit comprises a pair of second field effect tubes, the pair of second field effect tubes are symmetrically connected in the form of a differential pair, and the adjustable resistor and the adjustable capacitor are both connected in parallel across the sources of the pair of second field effect tubes. The pair of second field effect tubes are used for synchronously converting the second voltage component signal into a current and realizing gain amplification through the transconductance characteristic of a field effect tube to obtain the second current signal.

7. The continuous-time linear equalizer based on a hybrid low-pass and band-pass structure according to claim 2, characterized by The first frequency division module comprises a first filter network composed of a blocking capacitor and an inductor, the second frequency division module comprises a second filter network composed of a blocking capacitor and an inductor, and the parameters of the first filter network and the second filter network are different. The first filter network is used for screening the first voltage component signal from the analog signal and transmitting the first voltage component signal to the band-pass transconductance unit. The second filter network is used for screening the second voltage component signal from the analog signal and transmitting the first voltage component signal to the low-pass transconductance unit.

8. The continuous-time linear equalizer based on a hybrid low-pass and band-pass structure according to claim 7, characterized by The band-pass transconductance unit comprises a first band-pass transconductance unit, a signal adjustment circuit and a second band-pass transconductance unit. The first band-pass transconductance unit is used for synchronously converting the first voltage component signal into a current and realizing first-stage gain amplification through the transconductance characteristic of a field effect tube to obtain a first-stage current signal. The signal adjustment circuit is used for at least converting the first-stage current signal into a voltage signal. The second band-pass transconductance unit is used for synchronously converting the converted voltage signal into a current and realizing second-stage gain amplification through the transconductance characteristic of a field effect tube to obtain a second-stage current signal, and the second-stage current signal is the first current signal.

9. The continuous-time linear equalizer based on a hybrid low-pass and band-pass structure according to claim 8, characterized by The signal adjustment circuit comprises a series resonance network composed of an inductor and a capacitor. The series resonance network is used for providing gain compensation for the first-stage current signal.

10. The continuous-time linear equalizer based on a hybrid low-pass and band-pass structure according to claim 2, characterized by The frequency selection coupler further comprises a middle-pass transconductance unit, and the third frequency division module is further connected with the input end of the middle-pass transconductance unit, and the input end of the load unit is further connected with the output end of the middle-pass transconductance unit. The third frequency division module is used for screening a third voltage component signal from the analog signal and transmitting the third voltage component signal to the middle-pass transconductance unit, the frequency of the third voltage component signal is located in a second band-pass frequency range, and the frequency in the second band-pass frequency range is greater than the frequency in the low-pass frequency range and less than the frequency in the first band-pass frequency range. The middle-pass transconductance unit is further used for converting the third voltage component signal into a current and synchronously realizing gain amplification to obtain a third current signal. The load unit is used for summing and converting the first current signal, the second current signal and the third current signal into a voltage signal.

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