A circuit for improving the quality of high-speed communication signals

Abstract

The present invention provides a circuit for improving the quality of high-speed communication signals, comprising a main circuit and a branch circuit, and further comprising a function selection synthesis circuit. The signal passes through the branch and the main circuit and is input into the function selection synthesis circuit for waveform synthesis, thereby realizing the switching between the de-emphasis function and the slew rate reduction function. The present invention multiplexes a main circuit and a branch driving circuit and controls the switching between the de-emphasis function and the slew rate reduction function through the function selection circuit. Compared with the prior art, the present invention effectively reduces the complexity of the circuit structure, saves the circuit area, and reduces the cost.

Description

Technical Field

[0001] The invention belongs to the technical field of optical communication, and in particular relates to a circuit for improving the quality of high-speed communication signals. Background Art

[0002] High-speed wired communication transmission circuits are usually reused in channels with different transmission distances. The longer the transmission distance, the more serious the loss and discontinuity of the channel. The high-frequency components of the signal are greatly damaged during the transmission process, causing distortion of the high-speed signal waveform, which is usually manifested as an increase in the rise and fall time of the signal and a decrease in the overall amplitude of the signal, which will reduce the opening of the eye diagram, affect the quality of the eye diagram, and cause communication errors. The shorter the transmission distance, the weaker the loss and discontinuity of the channel, and the high-frequency components of the signal are almost unaffected during the transmission process. Since the design usually reserves high-frequency compensation and the channel attenuation is insufficient, the signal will have amplitude overshoots on the rising and falling edges, and will also cause more serious crosstalk between channels, which will also increase the bit error rate of the communication signal.

[0003] For long channels, where the transmission distance is too long, resulting in excessive loss and discontinuity, a backward de-emphasis circuit is usually added to compensate for the high-frequency components of the signal that are more damaged. For short channels, where the transmission distance is short, resulting in insufficient channel attenuation, which causes overshoots at the rising and falling edges of the signal, a circuit that reduces the signal slew rate is usually added to weaken the high-frequency components with excessive amplitude. However, since the same circuit may be used in communication links with different channel lengths and qualities, in order to ensure signal and communication quality, the circuit needs to have both signal de-emphasis and slew rate reduction functions. The prior art usually has both a de-emphasis circuit and a slew rate reduction circuit. During use, the de-emphasis or slew rate reduction circuit is turned on based on the actual channel length and quality. The schematic diagram of the circuit with both de-emphasis and slew rate reduction functions is shown below. Figure 1 In this circuit, no matter which function is turned on, the other function circuit will be turned off, which will make part of the circuit unused and cause circuit redundancy and area waste, increasing the cost and complexity of the circuit. Summary of the invention

[0004] The purpose of the present invention is to provide a circuit for improving the quality of high-speed communication signals, so as to solve the technical problems of the prior art proposed in the above background technology, such as complex circuit structure, waste of area and high cost.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A circuit for improving the quality of high-speed communication signals comprises a main circuit and a branch circuit, and also comprises a function selection synthesis circuit. The signal passes through the branch circuit and the main circuit and is input into the function selection synthesis circuit for waveform synthesis, thereby realizing the switching between the de-emphasis function and the slew rate reduction function.

[0007] Furthermore, the main circuit is a main driving circuit, and the branch circuit includes a branch pre-stage driving circuit and a branch output driving circuit.

[0008] Furthermore, the function selection synthesis circuit includes three groups of transistor pairs, namely transistor pair A, transistor pair B and transistor pair C, which are connected to their respective tail current sources. The tail current sources of the transistor pair B and the transistor pair C have function selection circuits to control the opening and closing of the corresponding tail current sources, and connect the output ends of the transistors with the same poles, and connect the resistors in parallel to the power supply.

[0009] Preferably, the positive and negative poles of the transistor pair A and the transistor pair B are opposite, and the positive and negative poles of the transistor pair A and the transistor pair C are in the same direction. Meanwhile, the positive and negative poles of the input terminals of the transistor pair B and the transistor pair C are connected in opposite directions.

[0010] Preferably, the function selection circuit is composed of two groups of current mirrors and transistor control switches, the current mirrors convert the reference current into a tail current connecting transistor pair B and transistor pair C, and the transistor control switch realizes the turning on and off of the corresponding tail current source through the function switching control signal and the inverter.

[0011] Preferably, the main circuit signal is input into the transistor pair A, and the branch circuit signal is input into the transistor pair B and the transistor pair C.

[0012] The present invention has the following beneficial effects:

[0013] 1. The de-emphasis function circuit and the slew rate reduction circuit of the present invention share a main and branch driving circuit, while the existing method only uses the corresponding driving circuit regardless of whether the de-emphasis function or the slew rate reduction function is turned on. Since the driving circuit of the other function is not used, the circuit is redundant and the area is wasted. Compared with the prior art, the present invention simplifies the traditional circuit structure, saves circuit area, and reduces costs.

[0014] 2. Use the function selection circuit to select whether to enable the de-emphasis function or the slew rate reduction function. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0016] Figure 1 It is a schematic diagram of a circuit with both de-emphasis and slew rate reduction functions in the prior art;

[0017] Figure 2 A schematic diagram of the circuit structure of the present invention;

[0018] Figure 3 Select the schematic diagram of the synthesis circuit structure for the function;

[0019] Figure 4 It is the schematic diagram of the tail current source and function selection circuit;

[0020] Figure 5 It is the circuit working flow chart of the present invention.

[0021] In the accompanying drawings, the components represented by the various symbols are as follows:

[0022] Transistor pair A-1, transistor pair B-2, transistor pair C-3, current mirror-4. DETAILED DESCRIPTION

[0023] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 2-5 As shown, a circuit for improving the quality of high-speed communication signals has a structure as shown in FIG. Figure 2 As shown, it is composed of a main circuit, a branch circuit and a function selection synthesis circuit. The main circuit is a main driving circuit, and the branch circuit includes a branch pre-stage driving circuit and a branch output driving circuit.

[0025] The function selection synthesis circuit realizes the switching between the de-emphasis function and the slew rate reduction function through the function selection circuit, and its structure is as follows: Figure 3As shown, it includes three groups of transistor pairs, namely transistor pair A1, transistor pair B2 and transistor pair C3, connected to their respective tail current sources, and the tail current sources of the transistor pair B2 and the transistor pair C3 have a function selection circuit to control the opening and closing of the corresponding tail current source, and connect the output ends of the transistors with the same poles, and connect the resistors in parallel to the power supply. The positive and negative poles of the transistor pair A1 and the transistor pair B2 are opposite, and the positive and negative poles of the transistor pair A1 and the transistor pair C3 are in the same direction. At the same time, the positive and negative poles of the input ends of the transistor pair B2 and the transistor pair C3 are connected in reverse. By controlling the opening and closing of the tail current sources of the transistor pair B2 and the transistor pair C3, the addition and subtraction of the current between the transistor pairs can be realized at the output end, and the synthesis of the input waveforms of the main circuit and the branch circuit can be realized.

[0026] The tail current source of the transistor pair B2 and the transistor pair C3 in the function selection synthesis circuit and the function selection circuit are as follows: Figure 4 As shown, it is composed of two groups of current mirrors 4 and transistor control switches, and the current mirror 4 converts the reference current iref into a tail current connected to the transistor pair B2 and the transistor pair C3. When the function switching control signal is high, the parallel transistor control terminal of the transistor pair C3 is connected to a high voltage, the transistor switch is turned on, the three terminals of the mirror transistor are grounded, the tail current source is biased in a cut-off state, the tail current is turned off, and no current is output; at the same time, the function switching control signal is converted into a low voltage through the inverter, and is connected to the parallel transistor control terminal of the transistor pair B2, the transistor switch is turned off, and the current mirror 4 works normally, providing a normal mirror current to the transistor pair B2. Conversely, when the function switching control signal is low, the tail current of the transistor pair B2 is turned off, and no current flows; while the current mirror 4 of the transistor pair C3 works normally, providing it with a normal tail current.

[0027] The overall working process of the circuit of the present invention is as follows: Figure 5As shown, the input signal passes through the branch circuit and the main circuit, so that the output signal of the branch output drive circuit and the output signal of the main drive circuit form a certain phase delay, and the two signals are input into the function selection synthesis circuit for waveform synthesis, wherein the main signal is input into the transistor pair A1 of the function selection synthesis circuit, and the branch signal is input into the transistor pair B2 and the transistor pair C3 of the function selection synthesis circuit. When the de-emphasis function is turned on, the tail current of the transistor pair B2 is turned on, so that the transistor pair B2 works normally, and the tail current of the transistor pair C3 is turned off, so that the transistor pair C3 is in the cut-off state. At this time, the main output signal is input into the transistor pair A1, and the branch output signal is input into the transistor pair B2. Since the input positive and negative poles of the transistor pair A1 and the transistor pair B2 are opposite, the waveform polarity of the branch output signal is reversed after entering the function selection synthesis circuit, thereby realizing the reverse synthesis of the branch output signal with phase delay and the main output signal waveform in the function selection synthesis circuit, and realizing the de-emphasis function. Similarly, when the slew rate reduction function is turned on, the tail current of transistor pair C3 is turned on, so that transistor pair C3 works normally, and the tail current of transistor pair B2 is turned off, so that transistor pair B2 is in a cut-off state. At this time, the main output signal is input to transistor pair A1, and the branch output signal is input to transistor pair C3. Since the positive and negative inputs of transistor pair A1 and transistor pair C3 are the same, the polarity of the waveform of the branch output signal remains unchanged after entering the function selection synthesis circuit, thereby realizing the same-direction synthesis of the branch output signal with phase delay and the main output signal waveform in the function selection synthesis circuit, and realizing the slew rate reduction function.

[0028] The present invention modifies and simplifies the circuit structure based on the basic structure of the circuit having both de-emphasis and slew rate reduction functions. Compared with the traditional structure, the present invention merges the branches that realize the de-emphasis and slew rate reduction functions into one branch, reduces two driving circuits, and simplifies the three inputs of the traditional structure into two inputs in the function selection synthesis circuit, and adds a function selection circuit to realize the switching of the de-emphasis function and the slew rate reduction function. The input signal passes through the branch circuit and the main circuit, so that the output signal forms a certain phase delay. When the channel is long or the quality is poor, the polarity of the output signal of the branch output driving circuit is reversed, and the waveforms of the two signals are reversely synthesized to complete the de-emphasis function. When the channel is short or the quality is good, the polarity of the output signal of the branch output driving circuit is kept unchanged, and the waveforms of the two signals are synthesized in the same direction to complete the slew rate reduction function.

[0029] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A circuit for improving the quality of high-speed communication signals, comprising a main circuit and a branch circuit, characterized in that: It also includes a function selection synthesis circuit, which is composed of multiple groups of transistor pairs and function selection circuits. The function selection circuit is composed of multiple groups of current mirrors (4) and transistor control switches. The signal passes through the branch circuit and the main circuit and is input into the function selection synthesis circuit for waveform synthesis, thereby realizing the switching between the de-emphasis function and the slew rate reduction function.

2. A circuit for improving the quality of high-speed communication signals according to claim 1, characterized in that: The main circuit is a main driving circuit, and the branch circuit includes a branch pre-stage driving circuit and a branch output driving circuit.

3. A circuit for improving high-speed communication signal quality according to claim 1, characterized in that: The function selection synthesis circuit comprises three groups of transistor pairs, namely transistor pair A (1), transistor pair B (2) and transistor pair C (3), connected to respective tail current sources. The tail current sources of the transistor pair B (2) and the transistor pair C (3) have the function selection circuit to control the on and off of the corresponding tail current sources.

4. A circuit for improving high-speed communication signal quality according to claim 3, characterized in that: The positive and negative poles of the transistor pair A (1) and the transistor pair B (2) are in opposite directions, and the positive and negative poles of the transistor pair A (1) and the transistor pair C (3) are in the same direction. At the same time, the positive and negative poles of the input terminals of the transistor pair B (2) and the transistor pair C (3) are connected in opposite directions.

5. A circuit for improving the quality of high-speed communication signals according to claim 3 or 4, characterized in that: The current mirror (4) converts the reference current into a tail current connected to the transistor pair B (2) and the transistor pair C (3), and the transistor control switch realizes the opening and closing of the corresponding tail current source through the function switching control signal and the inverter.

6. A circuit for improving the quality of high-speed communication signals according to claim 3 or 4, characterized in that: The main circuit signal is input into the transistor pair A (1), and the branch circuit signal is input into the transistor pair B (2) and the transistor pair C (3).

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