Signal transmission circuit

Abstract

The utility model provides a kind of signal transmission circuit.The signal transmission circuit includes: differential drive module, for converting single-ended input signal into differential signal;Differential drive module is electrically connected with signal conversion module by transmission cable, for transmitting differential signal to signal conversion module by transmission cable;Signal conversion module is used to recover differential signal, and the recovered differential signal is converted into single-ended output signal to drive microphone to work.Therefore, the utility model can realize reliable signal transmission based on the design of transmission cable, greatly improve far-field pickup performance and voice interaction effect.This simplified transmission architecture enables the robot to arrange multiple microphones on the whole machine at low cost and high density, so that reliable sound collection can be achieved regardless of the motion posture of the robot, improving the recognition rate of voice interaction.

Description

Technical Field

[0001] This utility model relates to the field of robot technology, and in particular to a signal transmission circuit. Background Technology

[0002] With the rapid development of artificial intelligence technology, robots are gradually being integrated into daily life. To achieve natural and smooth human-computer interaction, voice interaction is the key to achieving this goal, such as robots performing tasks through users' voice commands.

[0003] In existing technologies, robots commonly use electret condenser microphones (ECMs) as their sound pickup units. The ECM outputs analog audio signals, which need to be pre-conditioned by an onboard operational amplifier before being transmitted to the main processor for analog-to-digital conversion and processing.

[0004] However, due to the low strength and poor anti-interference capability of the analog signal output by the ECM, the effective transmission range of the analog signal is limited to the same main circuit board level. It cannot be reliably deployed to the far end of the robot, such as the head or hands, which greatly restricts the robot's design flexibility and far-field sound pickup performance, affecting the effective distance and recognition rate of voice interaction. Utility Model Content

[0005] This invention provides a signal transmission circuit to solve the problems of low analog signal strength and poor anti-interference ability of existing ECM outputs, as well as the fact that the effective transmission range of analog signals is limited to the same main circuit board level, which greatly restricts the flexibility of robot design and far-field sound pickup performance, and affects the effective distance and recognition rate of voice interaction.

[0006] This utility model provides a signal transmission circuit, which includes:

[0007] The differential drive module is used to convert single-ended input signals into differential signals;

[0008] The differential drive module is electrically connected to the signal conversion module via a transmission cable, and is used to transmit differential signals to the signal conversion module via the transmission cable.

[0009] The signal conversion module is used to recover the differential signal and convert the recovered differential signal into a single-ended output signal to drive the microphone.

[0010] Compared to existing single-ended signal transmissions, which are susceptible to interference, ringing, and inconsistent reference grounds, this invention uses a differential drive module to perform impedance transformation and power enhancement on the output single-ended input signal, converting it into a differential signal with strong driving capability. This fundamentally overcomes the shortcomings of single-ended signals in complex robot electromechanical environments, such as susceptibility to interference, ringing, and distortion due to unequal reference ground potentials. This design effectively avoids electromagnetic compatibility (EMC) interference caused by motor drives and battery fluctuations, as well as radiated noise from surrounding high-current wiring harnesses. It also effectively overcomes line losses in long-distance transmission, ensuring that the signal amplitude still meets processing requirements at the far end.

[0011] Secondly, when using transmission cables to transmit differential signals, external interference will couple to the positive and negative signal lines of the twisted pair in equal amounts in common-mode form during transmission. Since the signal conversion module only detects the voltage difference between the positive and negative signals, this common-mode interference will be effectively eliminated at the receiving end, thereby ensuring the integrity of the signal during long-distance transmission.

[0012] The significantly enhanced anti-interference capability removes the board-level limitation on effective signal transmission. This allows sensors to be flexibly deployed at remote locations on the robot. Avoiding the use of high-speed communication interfaces requiring complex protocol stacks, such as universal USB or Ethernet, not only saves on BOM costs but also reduces software development difficulty and time.

[0013] Therefore, a simple twisted-pair cable is sufficient for reliable signal transmission, greatly improving far-field sound pickup performance and voice interaction. This simplified transmission architecture allows multiple microphones to be deployed at low cost and high density throughout the robot, enabling reliable sound acquisition regardless of the robot's movement posture, thus laying a solid foundation for high-quality voice interaction.

[0014] Optionally, the differential drive module includes an H-bridge drive unit for generating complementary differential signals based on single-ended input signals to suppress electromagnetic interference.

[0015] Because H-bridge drivers can generate highly symmetrical, precisely out-of-phase ideal complementary signals, they can produce high-quality differential signals, thus effectively suppressing common-mode noise. Furthermore, the powerful driving capability of H-bridge drivers allows differential signals to overcome losses caused by the distributed capacitance and resistance of long-distance transmission cables, ensuring that the signal amplitude remains sufficiently large upon arrival at the receiving end, further enhancing the robustness and anti-attenuation capabilities of the signal transmission circuit.

[0016] Optionally, the H-bridge drive unit includes an inverter, a first switch, a second switch, a third switch, and a fourth switch; each switch is electrically connected to a Schottky diode; the differential signal includes a first signal and a second signal;

[0017] The first switch and the third switch are electrically connected. When the first switch is in the off state and the third switch is in the on state, the single-ended input signal is output as the first signal after passing through the third switch.

[0018] The input terminal of the second switch is electrically connected to the inverter, and the output terminal of the second switch is electrically connected to the fourth switch. When the second switch is in the on state and the fourth switch is in the off state, the single-ended input signal passes through the inverter and the second switch in sequence and outputs the second signal.

[0019] In this invention, an inverter is used to ensure a precise 180-degree phase difference between the second and first signals. Furthermore, by controlling the on / off switching modes of the switching transistor, a clear digital differential signal can be generated, reducing distortion and phase errors that might occur with analog amplifiers. Moreover, the switching transistor has extremely low impedance when on and extremely high impedance when off, resulting in very low power consumption in this operating mode. Therefore, the power switching bridge design based on the switching transistor can provide a powerful current output capability, effectively driving capacitive loads (such as long cables) and ensuring that the differential signal has sufficient strength for long-distance transmission without significant waveform attenuation.

[0020] Furthermore, the electrical connection of each switching transistor to a Schottky diode is crucial. Their primary function is to provide a freewheeling path and suppress voltage spikes. When the switching transistor is rapidly turned off, the parasitic inductance in the circuit generates a reverse induced electromotive force (voltage spike). The Schottky diode provides a discharge path for this induced current, thus protecting the switching transistor from breakdown and significantly improving the circuit's robustness and reliability.

[0021] Optionally, the signal transmission circuit also includes a voltage regulator module, which is electrically connected to the differential drive module and is used to perform two-stage voltage regulation on the single-ended input signal.

[0022] Because the power supply to the signal transmission circuit is not ideal, noise on the power line can modulate the output signal. Therefore, using a two-stage voltage regulator can significantly improve the power supply rejection ratio of the differential driver module, effectively resisting interference from the power supply and ensuring that the output differential signal reflects the true audio input without including power supply noise. By preventing power supply noise from being introduced into the signal transmission circuit as a new source of interference, the differential signal generated by the differential driver module can have higher purity and signal-to-noise ratio, laying a better foundation for subsequent long-distance transmission and high-quality signal recovery. Therefore, this two-stage voltage regulator architecture achieves "hierarchical processing" of noise. This division of labor achieves a wider bandwidth and more efficient filtering effect than single-stage voltage regulation, thus providing optimal power quality overall.

[0023] Furthermore, in robotic applications, the power supply voltage can drop momentarily due to the high current load of the motor. The primary voltage regulator can withstand such large fluctuations, preventing malfunctions in subsequent circuits; the secondary voltage regulator ensures that the supply voltage to the differential drive module remains constant during these fluctuations. This guarantees the stability and reliability of the audio transmission circuitry in the complex electromagnetic and load environments of robots.

[0024] Optionally, the voltage regulator module includes a first Zener diode, a second Zener diode, and a first resistor; the first Zener diode is electrically connected to the input terminal of the signal transmission circuit for primary voltage regulation of the single-ended input signal; the second Zener diode and the first resistor are electrically connected; the output terminal of the first resistor is electrically connected to the input terminal of the signal transmission circuit for secondary voltage regulation of the single-ended input signal.

[0025] Thus, by employing a simple combination of two Zener diodes and resistors, graded noise suppression can be achieved, effectively suppressing power supply interference over a wider frequency range compared to single-stage regulation. Since the stability and accuracy of the circuit's output voltage primarily depend on the characteristics of the second Zener diode, which, due to the primary voltage regulation of the first Zener diode, is unaffected by a wide range of input fluctuations, this enhances voltage regulation accuracy and stability. The first Zener diode not only regulates voltage but also provides overvoltage protection. If an abnormally high voltage occurs at the input, the first Zener diode will break down first, limiting the voltage to a safe range and preventing the high voltage from directly impacting the more precise differential drive module in the subsequent stages, thus improving the overall robustness of the circuit.

[0026] Furthermore, since it uses only two Zener diodes and one resistor, eliminating the need for complex integrated circuits, the circuit structure is very simple, reliable, and extremely low in cost, making it ideal for widespread use in industrial applications that require high cost-effectiveness and reliability, such as robotics.

[0027] Optionally, the circuit also includes an electrostatic discharge (ESD) protection module, which is electrically connected to the transmission cable to suppress ESD interference.

[0028] Because static electricity can affect the internal components of differential drive modules or signal conversion modules, an electrostatic discharge (ESD) protection module is incorporated into the signal transmission circuit to ensure stable and reliable operation. Even if ESD interference doesn't damage the hardware, it can still generate a large voltage spike on the signal lines. This voltage spike can be mistaken for a valid signal, leading to data errors, communication interruptions, and other problems. Therefore, the ESD protection module quickly clamps and eliminates the voltage spike, ensuring the continuity and integrity of the normal differential signal.

[0029] Optionally, the electrostatic discharge (ESD) protection module includes a first ESD protection unit and a second ESD protection unit. One end of the first ESD protection unit is electrically connected to the output terminal of the differential drive module, and the other end of the first ESD protection unit is electrically connected to the transmission cable. One end of the second ESD protection unit is electrically connected to the transmission cable, and the other end of the second ESD protection unit is electrically connected to the input terminal of the signal conversion module.

[0030] Understandably, transmission cables can be very long, and their entire exposed portion can become a path for electrostatic coupling. Single-point protection, such as installing an electrostatic discharge (ESD) protection unit only at the receiving end, cannot effectively protect against ESD from the other end. This invention, by simultaneously installing ESD protection units at both the transmitting and receiving ends, ensures that regardless of where the ESD surge occurs in the transmission cable, the protective path can be directly discharged, achieving comprehensive protection. Moreover, if only an ESD protection unit is installed at the far end, the inductance of the long transmission cable will delay the response and generate higher voltage overshoot, reducing the protection effect. Therefore, simultaneously installing ESD protection units at both the transmitting and receiving ends also reduces parasitic inductance in the path, allowing the protection device to respond and clamp the voltage more quickly, thus providing more effective protection.

[0031] Optionally, the differential drive module also includes a signal conditioning unit, which is used to protect the integrity of the single-ended input signal.

[0032] In this invention, the design of the signal conditioning unit ensures the stability of the operation of sensors such as microphones, prevents input signal jumps and deviations, and also keeps the input signal of the subsequent differential drive module stable, thereby improving the consistency and reliability of the signal transmission circuit performance.

[0033] Optionally, the signal conditioning unit includes a second resistor, a third resistor, and a third Zener diode. The second resistor and the third Zener diode are electrically connected in parallel to prevent the single-ended input signal from changing abruptly. The third resistor is electrically connected to the differential drive module to limit the current flowing through the circuit to a safe range.

[0034] Therefore, by using the second resistor and the third Zener diode for voltage clamping and the third resistor for current limiting, circuit problems caused by voltage transients are prevented, the robustness of the signal transmission circuit is enhanced, and reliable overcurrent protection is further achieved.

[0035] Optionally, the signal conversion module includes a differential amplifier and a level conversion unit connected in sequence; the differential amplifier is used to recover the differential signal; and the level conversion unit is used to convert the recovered differential signal into a single-ended output signal.

[0036] Therefore, using a differential amplifier can effectively suppress common-mode noise introduced in long-distance transmission, greatly improving communication reliability. Furthermore, the level conversion unit can shape signals that may have slight jitter or slow rising edges into digital signals with defined logic levels. This eliminates uncertainties near the logic threshold, prevents false triggering due to noise, and ensures the accuracy of data sampling. Thus, through the design of the differential amplifier and level conversion unit, the differential signal from the transmission cable can be converted into standard digital logic levels, such as transistor-to-transistor logic (TTL) or CMOS levels. This allows any standard digital circuitry at the backend, such as a microphone, to directly and reliably receive and process this single-ended output signal without the need for complex interface circuitry, simplifying the overall design.

[0037] Optionally, the level conversion unit includes a fourth resistor and an inverting Schmitt trigger connected in sequence. The input terminal of the fourth resistor is electrically connected to the output terminal of the differential amplifier, and the inverting Schmitt trigger is used to output a single-ended output signal.

[0038] Therefore, the design of an inverting Schmitt trigger and a fourth resistor can convert analog single-ended signals with varying amplitudes into standard, stable digital logic levels (such as 0V / 3.3V). This ensures electrical compatibility with subsequent digital circuits and avoids logic errors caused by ambiguous voltage levels. Thus, through the simple design of an inverting Schmitt trigger and a fourth resistor, multiple functions such as analog-to-digital conversion, waveform shaping, noise suppression, and inversion are simultaneously achieved. This high level of integration reduces the need for additional filtering or shaping circuits, simplifies circuit design, and significantly improves the reliability and robustness of the entire signal transmission.

[0039] Optionally, the signal transmission circuit also includes a matching unit; the matching unit is electrically connected to the differential amplifier and is used to prevent changes in the input differential signal.

[0040] The harmful effects of signal reflection become more pronounced at higher frequencies and with longer cables. Therefore, adding a matching unit to the signal transmission circuit allows it to operate stably at higher data rates or with longer cables without compromising signal integrity due to reflections. This ensures signal integrity even after long-distance or high-speed transmission. Furthermore, by eliminating reflections, the matching unit ensures that the waveform received by the differential amplifier is essentially identical to the waveform transmitted by the differential drive module, preventing distortions such as overshoot and ringing. This allows the differential amplifier to accurately determine and amplify the signal, providing high-quality input for subsequent circuits.

[0041] Optionally, the matching units include a fifth, sixth, seventh, and eighth resistor with the same resistance value.

[0042] The fifth resistor is electrically connected to the first input terminal of the differential amplifier, the sixth resistor is electrically connected to the second input terminal of the differential amplifier, the input terminal of the eighth resistor is electrically connected to the output terminal of the differential amplifier, the output terminal of the eighth resistor is electrically connected to the second input terminal of the differential amplifier, and the connection terminal of the fifth resistor and the first input terminal is electrically connected to the seventh resistor.

[0043] Therefore, compared to simple parallel resistor matching, the design of this invention can achieve true reflection-free matching. By precisely setting the input impedance to equal the characteristic impedance of the cable, it ensures that the signal energy is completely absorbed, fundamentally eliminating waveform distortion (overshoot, ringing) caused by reflection and guaranteeing the quality of the received signal. Furthermore, while a simple parallel matching resistor can also match impedance, it halves the signal voltage amplitude, reducing the signal-to-noise ratio. However, the subtractor circuit formed by the fifth, sixth, seventh, and eighth resistors and the differential amplifier in this design can utilize the high input impedance and feedback of the differential amplifier to achieve impedance matching without attenuating the signal voltage, maintaining the original signal amplitude.

[0044] Furthermore, this subtractor circuit integrates differential reception, impedance matching, and unity-gain buffering into a single, streamlined circuit. It eliminates the need for external matching resistors and additional buffer stages, simplifying board design, reducing component count, and improving circuit integration and reliability. Moreover, by selecting high-precision resistors, the matching impedance value can be set very accurately. Additionally, the resistor value can be adjusted to accommodate transmission cables with different characteristic impedances, providing greater flexibility and matching accuracy.

[0045] The signal transmission circuit provided by this utility model includes a differential driver module, a transmission cable, and a signal conversion module. Specifically, the differential driver module converts the single-ended signal output by the EMC into a pair of differential signals with opposite phases and equal amplitudes. This differential signal is transmitted to the remote signal conversion module via the transmission cable. Because differential signals have a natural suppression effect on common-mode noise, interference intruding during transmission is largely canceled out at the differential receiver of the signal conversion module, thus accurately restoring the original differential signal. Furthermore, the signal conversion module converts the restored differential signal back into a high-quality single-ended signal output to drive the microphone. In this way, this utility model effectively overcomes the limitations of long-distance transmission of ECM analog signals by combining a differential signal transmission mechanism with a transmission cable. Attached Figure Description

[0046] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the present invention and, together with the description, serve to explain the principles of the present invention.

[0047] Figure 1 An application scenario diagram of a signal transmission circuit provided by this utility model;

[0048] Figure 2 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 1 ;

[0049] Figure 3 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 2 ;

[0050] Figure 4 A schematic diagram of the circuit structure of a signal transmission circuit provided by this utility model;

[0051] Figure 5 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 3 ;

[0052] Figure 6 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 4 ;

[0053] Figure 7 A schematic diagram of the circuit structure of another signal transmission circuit provided by this utility model;

[0054] Figure 8 A schematic diagram of the circuit structure of another signal transmission circuit provided by this utility model;

[0055] Figure 9 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 5 ;

[0056] Figure 10 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 6 ;

[0057] Figure 11 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 7 ;

[0058] Figure 12 A schematic diagram of the circuit structure of another signal transmission circuit provided by this utility model.

[0059] Explanation of reference numerals in the attached figures:

[0060] 100 - Signal transmission circuit; 200 - Robot dog; 101 - Differential drive module; 102 - Transmission cable; 103 - Signal conversion module; 104 - Voltage regulator module; 105 - Electrostatic protection module; 11 - H-bridge drive unit; 12 - First electrostatic protection unit; 13 - Second electrostatic protection unit; 14 - Signal conditioning unit; 15 - Differential amplifier; 16 - Level conversion unit; 17 - Matching unit.

[0061] The accompanying drawings have illustrated specific embodiments of the present invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the present invention in any way, but rather to illustrate the concept of the present invention to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0062] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this invention as detailed in the appended claims.

[0063] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly defined.

[0064] The technical solution of this utility model and how it solves the above-mentioned technical problems will be described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of this utility model will now be described with reference to the accompanying drawings.

[0065] Human-robot interaction is one of the important functions of robots, and this interaction mainly relies on voice to exchange information and perform tasks. In related technologies, robots use an ECM (Electronic Control Unit) as their voice pickup unit. The ECM outputs analog audio signals, which need to be initially conditioned by an onboard operational amplifier before being transmitted to the main processor for analog-to-digital conversion and processing.

[0066] However, analog audio signals have low strength and poor anti-interference ability, and are easily interfered with, especially during long-distance transmission, which leads to a decrease in sound pickup performance and affects the performance of the minimum sound pickup distance in the product specifications.

[0067] Moreover, robots typically contain a large number of motors, such as nearly 30 joint motors in the whole machine. The electromagnetic interference generated by their operation further limits the effective transmission distance of analog audio signals, making the effective transmission range of analog signals limited to the same main circuit board level. It is difficult to deploy microphones to remote positions such as hands and heads, which greatly restricts the design flexibility and far-field sound pickup performance of robots, and affects the effective distance and recognition rate of voice interaction.

[0068] Furthermore, for robots using silicon-based digital microphones or silicon micro-electro-mechanical systems (Si-MEMS), although they employ CMOS (Complementary Metal-Oxide-Semiconductor Logic Level) output and are not sensitive to noise introduced during transmission, their output signals are still not suitable for long-distance transmission and are mainly applicable to board-level applications.

[0069] To address the aforementioned problems, this invention provides a signal transmission circuit comprising a differential driver module, a transmission cable, and a signal conversion module. Specifically, the differential driver module converts the single-ended signal output by the EMC into a pair of differential signals with opposite phases and equal amplitudes. This differential signal is transmitted to the remote signal conversion module via the transmission cable. Because differential signals naturally suppress common-mode noise, interference intruding during transmission is significantly canceled out at the differential receiver of the signal conversion module, thus accurately reproducing the original differential signal. Furthermore, the signal conversion module converts the reproduced differential signal back into a high-quality single-ended signal output to drive the microphone. In this way, this invention effectively overcomes the limitations of long-distance transmission of ECM analog signals by combining a differential signal transmission mechanism with a transmission cable.

[0070] For example, Figure 1 An application scenario diagram of a signal transmission circuit provided by this utility model is shown, such as... Figure 1 As shown, taking the application in a robot dog as an example, the robot dog 200 includes a signal transmission circuit 100, which can be deployed at the head and tail of the robot dog 200.

[0071] The robot dog 200 is equipped with EMC microphones at its head and tail. The EMC microphones can capture the user's voice, such as voice commands, and convert them into analog electrical signals, i.e., single-ended input signals.

[0072] Furthermore, the differential drive module in the signal transmission circuit 100 converts the received single-ended input signal into a pair of differential signals, namely a positive-phase signal D+ and an inverted signal D-. Inside the robot dog 200, a flexible cable or ribbon cable passes from the head of the robot dog 200, through the neck (or joint), to the main body or other locations where circuit boards are deployed.

[0073] Since a pair of differential signals are transmitted through a transmission cable, the cable itself may pick up electromagnetic interference generated by motors, power supplies, etc. In this case, after receiving the differential signal from the transmission cable, the signal conversion module further converts the recovered differential signal back to the single-ended output signal required by the back-end processor, such as an audio codec, to drive the EMC microphone.

[0074] It should be noted that this utility model does not specifically limit the application scenarios and application robots of the signal transmission circuit 100. Optionally, the robot can also be a humanoid robot or other robot with multiple joint motors that can perform voice interaction.

[0075] For example, Figure 2 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 1 ,like Figure 2 As shown, the signal transmission circuit 100 includes:

[0076] Differential drive module 101 is used to convert single-ended input signals into differential signals;

[0077] The differential drive module 101 is electrically connected to the signal conversion module 103 via the transmission cable 102, and is used to transmit differential signals to the signal conversion module 103 via the transmission cable 102.

[0078] The signal conversion module 103 is used to recover the differential signal and convert the recovered differential signal into a single-ended output signal to drive the microphone.

[0079] In this invention, the signal transmission circuit 100 receives single-ended input signals from sensors such as ECMs via the differential drive module 101, and converts the single-ended input signals into a pair of differential signals with equal amplitude and opposite phase. This step transforms the single-ended input signal from a ground-referenced single-ended mode to a self-referenced differential mode.

[0080] The transmission cable 102 is used for signal transmission. During this process, external interference will be synchronously coupled to the two signal lines of the differential signal in the form of common-mode noise.

[0081] In this way, after receiving the pair of differential signals, the signal conversion module 103 extracts the difference through subtraction. Since the coupled common-mode noise is approximately equal on both signal lines, it is largely canceled out during the subtraction process, thereby recovering the original differential signal. Subsequently, the signal conversion module 103 converts the differential signal back into a standard single-ended output signal for use by the back-end circuitry or microphone.

[0082] Optionally, a single-ended input signal can refer to a voltage signal with a common ground as the reference point. This single-ended input signal can be a clock signal or a data signal generated by a codec, and it is a standard digital logic level differential signal.

[0083] The transmission cable 102 can refer to a pair of wires with a specific structure used to transmit differential signals. For example, it can be a pair of signal lines of the same length that are tightly coupled. This utility model does not specifically limit the type of transmission cable 102.

[0084] It should be noted that in long-distance transmission, the transmission cable 102, like an antenna, inevitably introduces external noise, such as power supply interference, motor noise, and radio frequency interference. This external noise typically couples simultaneously and in phase to both signal lines of the differential signal. However, the signal conversion module only cares about the voltage difference between the two signal lines. That is, when (D+) subtracts (D-), since the external noise is added to both lines simultaneously, they cancel each other out in the subtraction operation. Therefore, although the signal lines themselves may carry high noise voltages, the voltage difference representing useful information remains clean. This greatly suppresses the impact of environmental noise on signal quality.

[0085] For example, taking a robot dog as an example, after the robot dog is powered on, it first initializes the codec. After initialization, the codec starts working and continuously outputs a clock signal with a frequency of 3.125MHz through its Pulse Density Modulation (PDM) interface. This clock signal is converted into a PN (pseudo-differential) signal by the differential driver module 101 and then transmitted to the remote microphone circuit board through the transmission cable 102. On the microphone circuit board, a signal conversion module 103 (differential to single-ended circuit) restores the PN signal to the original single-ended clock signal for use by the microphone.

[0086] Optionally, the microphone can also be a Si-MEMS silicon microphone, in which case the signal transmission circuit 100 can operate using a 3.3V working voltage.

[0087] Compared to existing single-ended signal transmissions, which are susceptible to interference, ringing, and inconsistent reference grounds, this invention uses a differential drive module 101 to perform impedance transformation and power enhancement on the output single-ended input signal, converting it into a differential signal with strong driving capability. This fundamentally overcomes the shortcomings of single-ended signals in complex robot electromechanical environments, such as susceptibility to interference, ringing, and distortion due to unequal reference ground potentials. This design effectively avoids electromagnetic compatibility (EMC) interference caused by motor drive and battery fluctuations, as well as radiated noise from surrounding high-current wiring harnesses. It also effectively overcomes line losses in long-distance transmission, ensuring that the signal amplitude can still meet processing requirements at the far end.

[0088] Secondly, differential signals are transmitted using transmission cable 102. During transmission, external interference will couple to the positive and negative signal lines of the twisted pair in equal amounts in common-mode form. Since the signal conversion module 103 only detects the voltage difference between the positive and negative signals, this common-mode interference will be effectively eliminated at the receiving end, thereby ensuring the integrity of the signal during long-distance transmission.

[0089] The significantly enhanced anti-interference capability eliminates the board-level limitation on effective signal transmission. This allows sensors to be flexibly deployed at remote locations on the robot. Avoiding the use of high-speed communication interfaces requiring complex protocol stacks, such as Universal Serial Bus (USB) or Ethernet, not only saves on hardware bill of materials (BOM) costs but also reduces software development difficulty and time.

[0090] Therefore, the transmission cable 102 only requires a simple twisted pair to achieve reliable signal transmission, greatly improving far-field sound pickup performance and voice interaction effects. This simplified transmission architecture allows multiple microphones to be deployed on the robot at low cost and high density, enabling reliable sound acquisition regardless of the robot's movement posture, laying a solid foundation for high-quality voice interaction.

[0091] It should be noted that if high-speed signals such as USB or network are used for long-distance transmission, the required circuit needs to have a dedicated differential transceiver decoding circuit, which is suitable for using chips with higher integration, and the circuit complexity is higher than that of this utility model.

[0092] Optional, Figure 3 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 2 ,like Figure 3 As shown, the signal transmission circuit 100, in addition to having Figure 2 In addition to the structure shown, the differential drive module 101 includes an H-bridge drive unit 11 for generating complementary differential signals based on single-ended input signals to suppress electromagnetic interference.

[0093] The H-bridge drive unit 11 is composed of controlled switching elements. This utility model does not specifically limit the number and type of switching elements.

[0094] In this invention, when a single-ended input signal is applied to the H-bridge driver unit 11, the internal circuit structure of the H-bridge driver unit 11 operates in a complementary state. The H-bridge driver unit 11 can then generate two output signals based on the polarity of the single-ended input signal: one signal is in phase with the original signal (positive phase signal, such as D+), and the other signal is completely out of phase with the original signal (inverted phase signal, such as D-).

[0095] It should be noted that the voltage difference (D+ - D-) between these two signals at any given time is proportional to the original input signal, but their voltages relative to ground are symmetrical about a common-mode level. Therefore, unlike a simple amplifier, the H-bridge driver unit 11 can provide a powerful current output capability, not only generating complementary signals but also driving the load of the subsequent transmission cable 102 in a low-impedance manner, reducing signal attenuation at the source end.

[0096] Because the H-bridge driver unit 11 can generate highly symmetrical, precisely out-of-phase ideal complementary signals, it can produce high-quality differential signals, thereby effectively suppressing common-mode noise. Furthermore, the powerful driving capability provided by the H-bridge driver unit 11 allows the differential signal to overcome losses caused by the distributed capacitance and resistance of the long-distance transmission cable 102, ensuring that the signal amplitude remains sufficiently large upon reaching the receiving end, further enhancing the robustness and anti-attenuation capability of the signal transmission circuit 100.

[0097] Optional, Figure 4 A circuit structure diagram of a signal transmission circuit provided by this utility model is shown below. Figure 4 As shown, the H-bridge drive unit 11 includes an inverter U1A, a first switch Q1, a second switch Q2, a third switch Q3, and a fourth switch Q4; each switch is electrically connected to a Schottky diode; the differential signal includes a first signal and a second signal;

[0098] The first switch Q1 and the third switch Q3 are electrically connected. When the first switch Q1 is in the off state and the third switch Q3 is in the on state, the single-ended input signal is output as the first signal after passing through the third switch Q3.

[0099] The input terminal of the second switch Q2 is electrically connected to the inverter U1A, and the output terminal of the second switch Q2 is electrically connected to the fourth switch Q4. When the second switch Q2 is in the on state and the fourth switch Q4 is in the off state, the single-ended input signal passes through the inverter U1A and the second switch Q2 in sequence and outputs the second signal.

[0100] In this invention, each switching transistor is electrically connected to a Schottky diode, such as... Figure 4 As shown, the first switch Q1 is electrically connected to the Schottky diode D2, the second switch Q2 is electrically connected to the Schottky diode D3, the third switch Q3 is electrically connected to the Schottky diode D6, and the fourth switch Q4 is electrically connected to the Schottky diode D7.

[0101] It should be noted that, considering the PDM clock signal may reach 5Mbps, a metal-oxide-semiconductor field-effect transistor (MOSFET) pair can be used as the switching transistor, with an upper limit of 8V for its gate-to-source voltage (VGS). The Schottky diode can be selected based on a maximum continuously and safely passing average forward current of 0.2 amps (IF = 0.2A) and a voltage drop across it of approximately 0.6 volts (VF = 0.6V) when the rated current flows through it.

[0102] Optionally, during the design of the signal transmission circuit 100, the transistors with different bandwidths can be modified to adapt to signals with different transmission rates and improve cost-effectiveness.

[0103] This invention does not impose specific limitations on the type and model of the switching transistor and Schottky diode; the above is merely an example.

[0104] For example, for the output path of the first signal, the single-ended input signal directly controls the gate (or base) of the first switch Q1 and the third switch Q3. When the input is high, the first switch Q1 is turned on and the third switch Q3 is turned off; when the input is low, the first switch Q1 is turned off and the third switch Q3 is turned on.

[0105] Thus, with the first switch Q1 off and the third switch Q3 on, the input signal is low. The current path (or signal path) through the on-state third switch generates a voltage signal at the output node D+ corresponding to the low input level. When the input is reversed to a high level, the first switch Q1 is on and the third switch Q3 is off, pulling D+ up to a high level. Therefore, the D+ signal always follows the changes in the single-ended input signal, forming the first signal of the in-phase output.

[0106] For the output path of the second signal, the single-ended input signal passes through inverter U1A to generate a signal with completely opposite phase. This inverted signal is used to control the second switch Q2 and the fourth switch Q4.

[0107] With the second switch Q2 on and the fourth switch Q4 off, the single-ended input signal is high. Therefore, the inverter U1A outputs a low level, turning on the second switch Q2 and turning off the fourth switch Q4. The current path (or signal path) through the on-state second switch Q2 generates a low-level signal at the output node D-. At this time, since the original input was high, D+ was high, and D- was low, they are opposite. When the input changes, D- always remains inverted compared to D+. Therefore, the second signal is the inverted output of the input signal.

[0108] Thus, through the above mechanism, when the single-ended input signal switches between high and low levels, the first switch Q1 and the third switch Q3, the second switch Q2 and the fourth switch Q4 operate in a complementary manner (when one group is on, the other group is off) to generate a first signal (in-phase) and a second signal (out-of-phase) with equal amplitude and completely opposite phase at the D+ and D- output terminals, which are the required differential signals.

[0109] like Figure 4 As shown, the two output terminals D+ and D- correspond to DMIC_CLK_P and DMIC_CLK_N respectively, and the input terminal for a single-ended input signal is DMIC_CLK. The corresponding electrical characteristics of the input and output terminals are shown in Table 1.

[0110] Table 1

[0111]

[0112] As shown in Table 1, after the high level at the DMIC_CLK terminal turns on the third switch Q3 and the second switch Q2, high and low levels can be generated sequentially on DMIC_CLK_P and DMIC_CLK_N.

[0113] In this invention, the use of inverter U1A ensures a precise 180-degree phase difference between the second and first signals. Furthermore, by controlling the on / off switching modes of the switching transistor, a clear digital differential signal can be generated, reducing distortion and phase errors that might arise from using analog amplifiers. Moreover, the switching transistor has extremely low impedance when on and extremely high impedance when off, resulting in very low power consumption in this operating mode. Therefore, the power switching bridge design based on the switching transistor provides a powerful current output capability, effectively driving capacitive loads (such as long cables) and ensuring sufficient strength for long-distance transmission of the differential signal without significant waveform attenuation.

[0114] Furthermore, the electrical connection of each switching transistor to a Schottky diode is crucial. Their primary function is to provide a freewheeling path and suppress voltage spikes. When the switching transistor is rapidly turned off, the parasitic inductance in the circuit generates a reverse induced electromotive force (voltage spike). The Schottky diode provides a discharge path for this induced current, thus protecting the switching transistor from breakdown and significantly improving the circuit's robustness and reliability.

[0115] Optional, Figure 5 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 3 ,like Figure 5 As shown, the signal transmission circuit 100, in addition to having Figure 2 In addition to the structure shown, the signal transmission circuit 100 also includes a voltage regulator module 104, which is electrically connected to the differential drive module 101 and is used to perform two-stage voltage regulation on the single-ended input signal.

[0116] In this invention, the two-stage voltage regulator typically includes a primary voltage regulator and a secondary voltage regulator. The primary voltage regulator is used to handle large power supply fluctuations, such as suppressing wide-range voltage variations or low-frequency noise introduced from the robot's main power supply system. It stabilizes an unstable input voltage (such as variations caused by motor start-stop) to a relatively stable, but not necessarily very precise, intermediate voltage.

[0117] The secondary regulator receives the output from the first-stage regulator and further regulates it to filter out high-frequency noise (such as ripple generated by the switching power supply) and stabilize the voltage within the range required by the differential drive module 101.

[0118] Because the power supply to the signal transmission circuit 100 is not ideal, noise on the power line can modulate the output signal. Therefore, using a two-stage voltage regulator can significantly improve the power supply rejection ratio of the differential driver module 101, effectively resisting interference from the power supply and ensuring that the output differential signal reflects the true audio input without including power supply noise. By preventing power supply noise from being introduced into the signal transmission circuit 100 as a new source of interference, the differential signal generated by the differential driver module 101 can have higher purity and signal-to-noise ratio, laying a better foundation for subsequent long-distance transmission and high-quality signal recovery. Therefore, this two-stage voltage regulator architecture achieves "hierarchical processing" of noise. This division of labor achieves a wider bandwidth and more efficient filtering effect than single-stage voltage regulation, thus providing optimal power quality overall.

[0119] Furthermore, in robotic applications, the power supply voltage can drop momentarily due to the high current load of the motor. The primary voltage regulator can withstand such large fluctuations, preventing malfunctions in subsequent circuits; the secondary voltage regulator ensures that the supply voltage of the differential drive module 101 remains constant during fluctuations. This guarantees the stability and reliability of the audio transmission circuit in the complex electromagnetic and load environments of the robot.

[0120] Optionally, as shown in Figure 4, the voltage regulator module 104 includes a first Zener diode D4, a second Zener diode D5, and a first resistor R1; the first Zener diode D4 is electrically connected to the input terminal of the signal transmission circuit 100 and is used for primary voltage regulation of the single-ended input signal; the second Zener diode D5 is electrically connected to the first resistor R1, and the output terminal of the first resistor R1 is electrically connected to the input terminal of the signal transmission circuit 100 and is used for secondary voltage regulation of the single-ended input signal.

[0121] The primary voltage regulation is achieved by the first Zener diode D4, which is directly connected between the input terminal of the signal transmission circuit 100 and ground (GND). Its working principle utilizes the reverse breakdown characteristic of the Zener diode. When the input voltage exceeds the Zener voltage of the first Zener diode D4, the first Zener diode D4 breaks down and conducts, thereby shunting away the excess current.

[0122] The secondary voltage regulation is achieved by a first resistor R1 and a second Zener diode D5. The first resistor R1 acts as a current-limiting resistor, connected in series with the second Zener diode D5, and then connected between the node after primary voltage regulation (i.e., the cathode of D4) and ground. This allows the first resistor R1 to share the voltage drop and limit the current flowing through the second Zener diode D5. In this way, the voltage at the connection point of the first resistor R1 and the second Zener diode D5 (i.e., the secondary voltage regulation output point) can be precisely stabilized at the regulated voltage value corresponding to the second Zener diode D5.

[0123] For example, such as Figure 4 As shown, after the single-ended input signal enters the signal transmission circuit 100 from the DMIC_CLK terminal, it is regulated by the primary voltage of the first Zener diode D4 and the secondary voltage of the first resistor R1 and the second Zener diode D5, which ensures that the voltage level entering the signal transmission circuit 100 is within a safe range.

[0124] It should be noted that the regulated voltage of the signal transmission circuit 100 depends on the VGS voltage of the switching transistor. The rated regulated voltage of the Zener diode can be 6.2V. This invention does not limit the specific value of the regulated voltage, which can be determined based on the requirements of the scenario.

[0125] Optionally, the first Zener diode D4 on the board can be left unmounted to reduce costs. "Unmounted" means that the component is not soldered onto the circuit board during the assembly stage.

[0126] Thus, by employing a simple combination of two Zener diodes and a resistor, graded noise suppression can be achieved, effectively suppressing power supply interference over a wider frequency range compared to single-stage voltage regulation. Since the stability and accuracy of the circuit's output voltage primarily depend on the characteristics of the second Zener diode D5, which is protected from a wide range of input fluctuations due to the primary voltage regulation of the first Zener diode D4, the voltage regulation accuracy and stability are enhanced. The first Zener diode D4 not only regulates the voltage but also provides overvoltage protection. If an abnormally high voltage occurs at the input, the first Zener diode D4 will break down first, limiting the voltage to a safe range and preventing the high voltage from directly impacting the more precise differential drive module 101 in the subsequent stage, thus improving the overall robustness of the circuit.

[0127] Furthermore, since it uses only two Zener diodes and one resistor, eliminating the need for complex integrated circuits, the circuit structure is very simple, reliable, and extremely low in cost, making it ideal for widespread use in industrial applications that require high cost-effectiveness and reliability, such as robotics.

[0128] Optional, Figure 6 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 4 ,like Figure 6 As shown, the signal transmission circuit 100, in addition to having Figure 2 In addition to the structure shown, the signal transmission circuit 100 also includes an electrostatic discharge protection module 105, which is electrically connected to the transmission cable 102 to suppress electrostatic discharge interference.

[0129] It should be noted that under normal operating conditions, the electrostatic discharge (ESD) protection module 105 exhibits extremely high impedance, having virtually no impact on the normal differential signal on the transmission cable 102, i.e., it does not affect signal integrity. However, when an ESD pulse couples to the transmission cable 102 through the air or through direct contact, it generates a transient voltage of thousands or even tens of thousands of volts within a very short time. Once this voltage exceeds the trigger voltage (or clamping voltage) of the ESD protection module 105, the ESD protection module 105 will immediately break down, changing from a high-impedance state to an extremely low-impedance state.

[0130] In this way, after switching to a low-impedance state, the electrostatic discharge (ESD) protection module 105 instantly establishes a temporary channel between the signal line and ground, rapidly guiding the enormous electrostatic energy to ground (GND), thereby clamping the voltage on the transmission cable 102 to a safe level that will not damage the downstream circuitry. After the pulse, the ESD protection module 105 automatically returns to a high-impedance state.

[0131] Because static electricity can affect the internal components of the differential drive module 101 or signal conversion module 103, an electrostatic discharge (ESD) protection module 105 is incorporated into the signal transmission circuit 100 to ensure stable and reliable operation of the differential drive module 101 or signal conversion module 103. Even if ESD interference does not damage the hardware, it can still generate a large voltage spike on the signal line. This voltage spike can be mistaken for a valid signal, leading to data errors, communication interruptions, and other problems. Therefore, the ESD protection module 105 eliminates the voltage spike through rapid clamping, ensuring the continuity and integrity of the normal differential signal.

[0132] Optional, Figure 7 A schematic diagram of another signal transmission circuit provided by this utility model. Figure 8 A schematic diagram of the circuit structure of another signal transmission circuit provided by this utility model is shown below. Figure 7 and Figure 8 As shown, the electrostatic discharge (ESD) protection module 105 includes a first ESD protection unit 12 and a second ESD protection unit 13. One end of the first ESD protection unit 12 is electrically connected to the output terminal of the differential drive module 101, and the other end of the first ESD protection unit 12 is electrically connected to the transmission cable 102. One end of the second ESD protection unit 13 is electrically connected to the transmission cable 102, and the other end of the second ESD protection unit 13 is electrically connected to the input terminal of the signal conversion module 103.

[0133] The first electrostatic discharge (ESD) protection unit 12 is located between the output end of the differential drive module 101 and the starting end of the transmission cable 102. Its function is to protect the differential drive module 101. When static electricity enters from the side of the transmission cable 102 near the drive end (for example, an ESD event occurring at the robot's neck connector), the first ESD protection unit 12 will respond immediately to discharge the static energy to the ground nearby, preventing high-voltage pulses from propagating in the reverse direction along the signal line.

[0134] The second electrostatic discharge (ESD) protection unit 13 is located between the end of the transmission cable 102 and the input end of the signal conversion module 103. Its function is to protect the signal conversion module 103. When static electricity enters from the side of the transmission cable 102 near the receiving end (for example, an ESD event occurring at the microphone opening on the robot's head), the second ESD protection unit 13 will immediately activate to discharge the static energy and prevent high-voltage pulses from impacting the receiving chip.

[0135] Optionally, considering long-distance traces and connector insertion and removal, as well as the possible static electricity generated inside the device, this invention uses a low-capacitance transient voltage suppressor (TVS) diode of 0.25pF in the circuit design.

[0136] Optionally, the first electrostatic discharge protection unit 12 includes at least two TVS diodes, such as... Figure 7 As shown, the first electrostatic discharge (ESD) protection unit 12 includes TVS diodes D8 and D9. The second ESD protection unit 13 includes at least two TVS diodes, such as... Figure 8 As shown, the second electrostatic protection unit 13 includes TVS diode D10 and TVS diode D11.

[0137] It is understandable that, given the potentially long length of the transmission cable 102, its entire exposed portion could become a path for electrostatic coupling. Single-point protection, such as installing an electrostatic discharge protection unit only at the receiving end, cannot effectively protect against electrostatic discharge from the other end. This invention, by simultaneously installing electrostatic discharge protection units at both the transmitting and receiving ends, ensures that regardless of where the electrostatic shock occurs in the transmission cable 102, the discharge path can be directly protected, achieving comprehensive protection. Furthermore, if only one electrostatic discharge protection unit is installed at the far end, the inductance of the long transmission cable 102 will delay the response and generate higher voltage overshoot, reducing the protection effect. Therefore, simultaneously installing electrostatic discharge protection units at both the transmitting and receiving ends also reduces parasitic inductance along the path, allowing the protection device to respond and clamp the voltage more quickly, thereby providing more effective protection.

[0138] Optional, Figure 9 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 5 ,like Figure 9 As shown, the signal transmission circuit 100, in addition to having Figure 2 In addition to the structure shown, the differential drive module also includes a signal conditioning unit 14, which is used to protect the integrity of the single-ended input signal.

[0139] The signal conditioning unit 14 is located at the front end of the signal transmission circuit 100, and is usually connected after the signal source (such as an ECM microphone) and before the H-bridge drive unit 11.

[0140] In this invention, the design of the signal conditioning unit 14 can ensure the stability of the operation of sensors such as microphones, prevent the input signal from jumping or shifting, and also keep the input signal of the subsequent differential drive module 101 stable, thereby improving the consistency and reliability of the signal transmission circuit 100.

[0141] Optional, such as Figure 4 or Figure 7 As shown, the signal conditioning unit 14 includes a second resistor R2, a third resistor R3, and a third Zener diode D1. The second resistor R2 and the third Zener diode D1 are electrically connected to prevent the single-ended input signal from jumping. The third resistor R3 is electrically connected to the differential drive module 101 to limit the current flowing through the circuit to a safe range.

[0142] In this circuit, the second resistor R2 and the third Zener diode D1 are connected in parallel, with one end connected to the single-ended input signal and the other end connected to the power supply VCC. When the single-ended input signal voltage exceeds the Zener voltage of the third Zener diode D1, the third Zener diode D1 will quickly conduct, clamping the input voltage to the regulated value. Simultaneously, the second resistor R2 acts as a current-limiting resistor, working in conjunction with the third Zener diode D1 to prevent damage to the third Zener diode D1 due to excessive current during clamping.

[0143] Understandably, the parallel network formed by the second resistor R2 and the third Zener diode D1 can effectively suppress instantaneous high voltage spikes (i.e., "jumps" or "glitches") that appear on the single-ended input signal, preventing these overshoot voltages from damaging the differential drive module 101.

[0144] The third resistor R3 is connected in series in the circuit and is located between the output terminal of the above parallel network and the input terminal of the differential drive module 101.

[0145] Understandably, according to Ohm's law ( The current flowing through the circuit will generate a voltage drop across the third resistor R3. If, due to some anomaly, the current attempts to increase rapidly, the voltage drop across the third resistor R3 will also increase significantly, thereby limiting the actual voltage and current reaching the circuit. In this way, the third resistor R3 limits the current that may flow through the differential drive module 101 to a safe, preset range. This invention does not limit the specific value of the safe range.

[0146] Therefore, voltage clamping is achieved through the second resistor R2 and the third Zener diode D1, and current is limited through the third resistor R3. This prevents circuit problems caused by voltage transients, enhances the robustness of the signal transmission circuit 100, and further realizes reliable overcurrent protection.

[0147] Optional, Figure 10 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 6 ,like Figure 10 As shown, the signal transmission circuit 100, in addition to having Figure 2 In addition to the structure shown, the signal conversion module 103 includes a differential amplifier 15 and a level conversion unit 16 connected in sequence; the differential amplifier 15 is used to recover the differential signal; the level conversion unit 16 is used to convert the recovered differential signal into a single-ended output signal.

[0148] Optionally, differential amplifier 15 can be a low-cost video differential amplifier U2A, which simplifies the design of signal transmission circuit 100 while ensuring bandwidth. Alternatively, differential amplifier 15 can also be a voltage follower.

[0149] The level conversion unit 16 can be selected as a comparator or an inverting Schmitt trigger, and this utility model does not specifically limit it.

[0150] For example, differential amplifier 15 receives a pair of differential signals (a first signal and a second signal) from transmission cable 102. These differential signals are superimposed with common-mode noise of equal amplitude and phase during transmission. Furthermore, differential amplifier 15 operates by measuring the voltage difference between its two input terminals, D+ and D-, and suppresses the voltage component common to both input terminals (i.e., the common-mode signal).

[0151] Furthermore, the differential amplifier 15 outputs an analog single-ended signal whose voltage is proportional to (D+) minus (D-). Since common-mode noise is added to both D+ and D- simultaneously, they cancel each other out during the subtraction, thus the effective signal is extracted and amplified, while the common-mode noise is greatly suppressed. This step achieves the conversion from a differential signal to an analog single-ended signal.

[0152] The level conversion unit 16 can receive the analog single-ended signal output from the differential amplifier 15. The voltage range and waveform of this analog single-ended signal may not yet meet the interface requirements of the back-end digital circuitry (such as a microphone).

[0153] At this point, the level conversion unit 16 compares the voltage value of the analog single-ended signal with a reference threshold. When the voltage value is higher than the reference threshold, a standard logic high level (e.g., 3.3V) is output; when the voltage value is lower than the reference threshold, a standard logic low level (0V) is output. This process shapes and restores a continuous analog single-ended signal into a digital square wave signal, i.e., a single-ended output signal.

[0154] Therefore, the use of differential amplifier 15 can effectively suppress common-mode noise introduced in long-distance transmission, greatly improving communication reliability. Furthermore, level conversion unit 16 can shape signals that may have slight jitter or slow rising edges into digital signals with defined logic levels. This eliminates uncertainty near the logic threshold, prevents false triggering caused by noise, and ensures the accuracy of data sampling. Thus, through the design of differential amplifier 15 and level conversion unit 16, the differential signal from transmission cable 102 can be converted into standard digital logic levels, such as Transistor-Transistor Logic (TTL) levels or Complementary Metal-Oxide-Semiconductor (CMOS) levels. This allows any standard digital circuitry at the backend, such as a microphone, to directly and reliably receive and process the single-ended output signal without complex interface circuitry, simplifying the overall design.

[0155] Optional, such as Figure 8 As shown, the level conversion unit 16 includes a fourth resistor R4 and an inverting Schmitt trigger U3A connected in sequence. The input terminal of the fourth resistor R4 is electrically connected to the output terminal of the differential amplifier 15, and the inverting Schmitt trigger U3A is used to output a single-ended output signal.

[0156] It should be noted that the output of differential amplifier 15 is an analog single-ended signal, and its level may not perfectly conform to the standard logic level of subsequent digital circuits, such as 3.3V. Therefore, a fourth resistor R4 is placed between the output of differential amplifier 15 and the input of inverting Schmitt trigger U3A for current limiting and matching. This connection ensures that the output signal level can be safely and appropriately applied to the inverting Schmitt trigger U3A.

[0157] In this invention, the inverting Schmitt trigger U3A is a special gate circuit with hysteresis characteristics. It has two critical threshold voltages: a positive threshold (VT+) and a negative threshold (VT-), and VT+ > VT-. Therefore, when the input voltage exceeds VT+, the output quickly flips to a low level (e.g., 0V). When the input voltage is lower than VT-, the output quickly flips to a high level (e.g., 3.3V).

[0158] When the input voltage is between VT- and VT+, the output remains unchanged. This characteristic allows the U3A inverting Schmitt trigger to convert a slowly changing or glitch-prone analog single-ended signal into a digital square wave signal while simultaneously performing the inversion function.

[0159] It should be noted that the Schmitt trigger U3A, due to its hysteresis window (VT+ - VT-), makes the signal transmission circuit 100 insensitive to noise and jitter in the input signal smaller than this hysteresis window. The output only changes when the signal changes and exceeds a threshold. This greatly suppresses the influence of ringing and glitches on the output signal, preventing false triggering. Furthermore, the regenerative characteristics of the Schmitt trigger U3A ensure that the rise and fall times of its output signal are extremely short when switching between high and low levels, and the waveform is close to an ideal square wave. This guarantees the timing accuracy of the clock signal and data acquisition, reducing bit errors.

[0160] Therefore, the design of the inverting Schmitt trigger U3A and the fourth resistor R4 can convert analog single-ended signals with varying amplitudes into standard, stable digital logic levels (such as 0V / 3.3V). This ensures electrical compatibility with subsequent digital circuits and avoids logic errors caused by ambiguous levels. Thus, through the simple design of the inverting Schmitt trigger U3A and the fourth resistor R4, multiple functions such as analog-to-digital conversion, waveform shaping, noise suppression, and inversion are simultaneously achieved. This high level of integration reduces the need for additional filtering or shaping circuits, simplifies circuit design, and significantly improves the reliability and robustness of the entire signal transmission.

[0161] Optional, Figure 11 A partial structural diagram of a signal transmission circuit provided by this utility model Figure 7 ,like Figure 11 As shown, the signal transmission circuit 100, in addition to having Figure 10 In addition to the structure shown, the signal transmission circuit 100 also includes a matching unit 17; the matching unit 17 is electrically connected to the differential amplifier 15, and the matching unit 17 is used to prevent changes in the input differential signal.

[0162] In this invention, the matching unit 17 can match the characteristic impedance of the transmission cable 102 with the input impedance of the receiving end, ensuring that the signal energy is completely absorbed, thereby preventing changes in the input differential signal (waveform). The matching unit 17 is typically a matching resistor network, which can be a resistor with a resistance value equal to or close to the characteristic impedance of the transmission cable 102. This invention does not limit the specific form of the matching unit 17.

[0163] For example, when the differential signal reaches the receiving end through the transmission cable 102, there may be a characteristic impedance. If the input impedance of the differential amplifier 15 is not equal to the characteristic impedance of the transmission cable 102, some of the signal energy will not be absorbed by the receiving end, but will be reflected back to the transmitting end along the transmission cable 102.

[0164] It should be noted that this partial signal can superimpose with the original signal, causing distortions such as overshoot, undershoot, and ringing in the received waveform, thus leading to incorrect logic level judgment. Therefore, the matching unit 17 is connected in parallel between the positive and negative input terminals of the differential amplifier 15, i.e., across the differential signal line. This provides a load to the transmission cable 102 with an impedance equal to its own characteristic impedance. When the signal reaches the end of the transmission cable 102, its energy is absorbed by this matching unit 17, thereby eliminating signal reflection.

[0165] For example, differential amplifier 15 is used as a voltage follower. Figure 8As shown, after the first and second signals corresponding to the DMIC_CLK_P and DMIC_CLK_N terminals enter the matching unit 17, they can output analog single-ended signals on the voltage follower after passing through it.

[0166] The harmful effects of signal reflection become more pronounced at higher frequencies and with longer cables. Therefore, by adding a matching unit 17 to the signal transmission circuit 100, the circuit can operate stably at higher data rates or with longer transmission cables without concern about signal integrity being compromised by reflections. This ensures that the signal maintains its integrity even after long-distance or high-speed transmission. Furthermore, by eliminating reflections, the matching unit 17 ensures that the signal waveform received by the differential amplifier 15 is essentially consistent with the waveform transmitted by the differential drive module 101, avoiding distortions such as overshoot and ringing. This allows the differential amplifier 15 to accurately determine and amplify the signal, providing high-quality input for subsequent circuits.

[0167] Optional, such as Figure 8 As shown, the matching unit 17 includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8 with the same resistance value;

[0168] The fifth resistor R5 is electrically connected to the first input terminal of the differential amplifier 15, the sixth resistor R6 is electrically connected to the second input terminal of the differential amplifier 15, the input terminal of the eighth resistor R8 is electrically connected to the output terminal of the differential amplifier 15, the output terminal of the eighth resistor R8 is electrically connected to the second input terminal of the differential amplifier 15, and the connection terminal of the fifth resistor R5 and the first input terminal of the differential amplifier 15 is electrically connected to the seventh resistor R7.

[0169] The seventh resistor, R7, is the gain setting resistor. It is connected between the non-inverting input (first input) of the differential amplifier 15 and ground (or a reference voltage). The fifth resistor, R5, and the seventh resistor, R7, form a voltage divider network.

[0170] The eighth resistor, R8, is the feedback resistor. It is connected between the output terminal and the inverting input terminal (second input terminal) of differential amplifier 15. The fifth resistor, R5, and the sixth resistor, R6, are input series resistors.

[0171] It should be noted that resistors R5 (fifth), R6 (sixth), R7 (seventh), and R8 (eighth), together with differential amplifier 15, constitute a standard subtractor circuit. Its output voltage satisfies the formula Vout = (Vp - Vn), where Vp is the voltage at the first input terminal and Vn is the voltage at the second input terminal.

[0172] Thus, when the four resistors have equal values ​​(R5=R6=R7=R8=1.5kR), the gain of differential amplifier 15 is 1. That is, Vout=Vp-Vn. This means that the subtractor circuit is not used for voltage amplification, but rather to convert the differential signal (Vp-Vn) into a ground-referenced single-ended signal (Vout) with high precision, while perfectly suppressing common-mode noise.

[0173] For example, taking a subtractor circuit (R5=R6=R7=R8=1.5KR, Vout=Vp-Vn) as an example, if signal amplification is required subsequently, simply increasing the value of the feedback resistor R8 will increase the gain. For instance, it can be determined whether the output voltage of differential amplifier 15 needs to be amplified based on theoretical calculations and actual waveform measurements. If output voltage amplification is required, the maximum value of the output Vout must be less than the supply voltage of differential amplifier 15; otherwise, it will cause distortion of the output signal. Therefore, in this circuit, voltage amplification is sufficient to meet the circuit's operational requirements.

[0174] Furthermore, the analog single-ended signal output from the differential amplifier 15 enters the inverting Schmitt trigger U3A, thereby converting the voltage range of the input analog single-ended signal into a standard, stable CMOS logic level, for example, 0.4V represents logic '0' and 3.3V represents logic '1'.

[0175] The numerical transformations corresponding to the above conversion process are shown in Table 2:

[0176] Table 2

[0177]

[0178] This design, by using the same values ​​for resistors R5, R6, R7, and R8, simplifies the calculation logic. Simultaneously, the reserved gain adjustment capability allows for convenient functional expansion by changing the value of resistor R8, providing a convenient means of debugging and optimization to address different application scenarios or component differences, demonstrating good design flexibility. Furthermore, it allows for precise impedance matching. By carefully designing the values ​​of resistors R5, R6, R7, and R8 (especially making them equal), the equivalent impedance of the two input terminals of the differential amplifier 15 can be made equal to the characteristic impedance of the transmission cable 102. Therefore, when the differential signal reaches the receiving end, the load impedance matches the characteristic impedance of the transmission cable 102, eliminating signal reflection.

[0179] Therefore, compared to simple parallel resistor matching, the design of this invention can achieve true reflection-free matching. By precisely setting the input impedance to equal the characteristic impedance of the cable, it ensures that the signal energy is completely absorbed, fundamentally eliminating waveform distortion (overshoot, ringing) caused by reflection and guaranteeing the quality of the received signal. Furthermore, while a simple parallel matching resistor can also match impedance, it halves the signal voltage amplitude, reducing the signal-to-noise ratio. However, the subtractor circuit formed by the fifth resistor R5, sixth resistor R6, seventh resistor R7, and eighth resistor R8, together with the differential amplifier 15, can utilize the high input impedance and feedback of the differential amplifier 15 to achieve impedance matching without attenuating the signal voltage, maintaining the original amplitude of the signal.

[0180] Furthermore, this subtractor circuit integrates differential reception, impedance matching, and unity-gain buffering into a single, streamlined circuit. It eliminates the need for external matching resistors and additional buffer stages, simplifying board design, reducing component count, and improving circuit integration and reliability. Moreover, by selecting high-precision resistors, the matching impedance value can be set very accurately. Additionally, the resistor value can be adjusted to accommodate transmission cables 102 with different characteristic impedances, providing greater flexibility and matching accuracy.

[0181] Optional, Figure 12 A schematic diagram of the circuit structure of another signal transmission circuit provided by this utility model is shown below. Figure 12 As shown, the signal transmission circuit 100 may also include a ninth resistor R9, a tenth resistor R10, and an eleventh resistor R11, wherein the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11 are not surface-mounted to reserve sufficient space.

[0182] The tenth resistor R10 and the eleventh resistor R11 are electrically connected in parallel, and the tenth resistor R10 is electrically connected to the input terminal of the seventh resistor R7. The input terminal of the ninth resistor R9 is electrically connected to the eleventh resistor R11, and the output terminal of the ninth resistor R9 is grounded.

[0183] It should be noted that during the circuit design phase, fine adjustments to certain circuit parameters, such as bias current, gain, filter cutoff frequency, or termination impedance, may not be theoretically possible to determine with complete precision, or their optimal values ​​may depend on factors such as the actual application environment and performance differences between different batches of chips. Therefore, in the circuit board layout, pad positions are reserved for the ninth resistor R9, the tenth resistor R10, and the eleventh resistor R11, but these resistors are not soldered during initial production. This improves design flexibility and debuggability.

[0184] Furthermore, these reserved resistor locations can also serve as "interfaces" or "test points" for circuit debugging. During the design process of the signal transmission circuit 100, changes in circuit performance can be observed and measured by soldering resistors of different resistance values ​​or measuring open-circuit and short-circuit conditions.

[0185] Other embodiments of the present invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the following claims.

[0186] It should be understood that this invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this invention is limited only by the appended claims.

Claims

1. A signal transmission circuit, characterized in that, The signal transmission circuit includes: The differential drive module is used to convert single-ended input signals into differential signals; The differential drive module is electrically connected to the signal conversion module via a transmission cable, and is used to transmit the differential signal to the signal conversion module via the transmission cable; The signal conversion module is used to recover the differential signal and convert the recovered differential signal into a single-ended output signal to drive the microphone.

2. The signal transmission circuit according to claim 1, characterized in that, The differential drive module includes an H-bridge drive unit, which is used to generate complementary differential signals based on the single-ended input signal to suppress electromagnetic interference.

3. The signal transmission circuit according to claim 2, characterized in that, The H-bridge drive unit includes an inverter, a first switch, a second switch, a third switch, and a fourth switch; each switch is electrically connected to a Schottky diode; the differential signal includes a first signal and a second signal. The first switch and the third switch are electrically connected. When the first switch is in the off state and the third switch is in the on state, the single-ended input signal is output as the first signal after passing through the third switch. The input terminal of the second switch is electrically connected to the inverter, and the output terminal of the second switch is electrically connected to the fourth switch. When the second switch is in the on state and the fourth switch is in the off state, the single-ended input signal passes through the inverter and the second switch in sequence and outputs the second signal.

4. The signal transmission circuit according to claim 1, characterized in that, The signal transmission circuit also includes a voltage regulator module, which is electrically connected to the differential drive module and is used to perform two-stage voltage regulation on the single-ended input signal.

5. The signal transmission circuit according to claim 4, characterized in that, The voltage regulator module includes a first Zener diode, a second Zener diode, and a first resistor; the first Zener diode is electrically connected to the input terminal of the signal transmission circuit for primary voltage regulation of the single-ended input signal; the second Zener diode is electrically connected to the first resistor; and the output terminal of the first resistor is electrically connected to the input terminal of the signal transmission circuit for secondary voltage regulation of the single-ended input signal.

6. The signal transmission circuit according to claim 1, characterized in that, The signal transmission circuit also includes an electrostatic discharge (ESD) protection module, which is electrically connected to the transmission cable and is used to suppress ESD interference.

7. The signal transmission circuit according to claim 6, characterized in that, The electrostatic protection module includes a first electrostatic protection unit and a second electrostatic protection unit. One end of the first electrostatic protection unit is electrically connected to the output end of the differential drive module, and the other end of the first electrostatic protection unit is electrically connected to the transmission cable. One end of the second electrostatic discharge protection unit is electrically connected to the transmission cable, and the other end of the second electrostatic discharge protection unit is electrically connected to the input terminal of the signal conversion module.

8. The signal transmission circuit according to claim 1, characterized in that, The differential drive module also includes a signal conditioning unit, which is used to protect the integrity of the single-ended input signal.

9. The signal transmission circuit according to claim 8, characterized in that, The signal conditioning unit includes a second resistor, a third resistor, and a third Zener diode. The second resistor and the third Zener diode are electrically connected in parallel to prevent the single-ended input signal from changing abruptly. The third resistor is electrically connected to the differential drive module to limit the current flowing through the circuit to a safe range.

10. The signal transmission circuit according to claim 1, characterized in that, The signal conversion module includes a differential amplifier and a level conversion unit connected in sequence; the differential amplifier is used to recover the differential signal; the level conversion unit is used to convert the recovered differential signal into a single-ended output signal.

11. The signal transmission circuit according to claim 10, characterized in that, The level conversion unit includes a fourth resistor and an inverting Schmitt trigger connected in sequence. The input terminal of the fourth resistor is electrically connected to the output terminal of the differential amplifier, and the inverting Schmitt trigger is used to output the single-ended output signal.

12. The signal transmission circuit according to claim 10, characterized in that, The signal transmission circuit further includes a matching unit; the matching unit is electrically connected to the differential amplifier, and the matching unit is used to prevent changes in the input differential signal.

13. The signal transmission circuit according to claim 12, characterized in that, The matching unit includes a fifth resistor, a sixth resistor, a seventh resistor, and an eighth resistor with the same resistance value; The fifth resistor is electrically connected to the first input terminal of the differential amplifier, the sixth resistor is electrically connected to the second input terminal of the differential amplifier, the input terminal of the eighth resistor is electrically connected to the output terminal of the differential amplifier, the output terminal of the eighth resistor is electrically connected to the second input terminal of the differential amplifier, and the connection terminal of the fifth resistor and the first input terminal is electrically connected to the seventh resistor.

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