Noise signal processing circuit and train noise monitoring system

Abstract

The utility model discloses a noise signal processing circuit and a train noise monitoring system, which relate to the field of train operation and maintenance safety guarantee, and comprise a blocking circuit, a gain adjusting circuit, a low-pass filter circuit, a differential processing circuit and an analog-to-digital conversion module, noise signals of a monitored object are subjected to direct-current component isolation through the blocking circuit, subjected to gain adjustment through the gain adjustment circuit, subjected to low-pass filtering through the low-pass filtering circuit and converted into differential signals through the differential processing circuit, and then the differential signals are converted into digital signals through the analog-to-digital conversion module to be output. The circuit carries out processing such as direct-current component isolation, low-pass anti-aliasing filtering and single-end to differential signal conversion on noise signals, improves the acquisition swing range of the noise signals and the anti-interference and anti-crosstalk capability, and has the advantages of high reliability, high precision and low cost.

Description

Technical Field

[0001] The utility model relates to the field of train operation and maintenance safety assurance, in particular to a noise signal processing circuit and a train noise monitoring system. Background Art

[0002] During the operation of rail trains, some sections of rail trains have the problem of high noise inside the car, and even the noise inside some sections has affected the normal communication of passengers and caused discomfort. In order to solve the above noise problem, it is necessary to collect and process the noise signals generated during the operation of rail trains. The existing noise signal acquisition link and signal processing circuit are relatively complex, the common mode signal noise or working point offset is relatively large, which affects the accuracy of high-precision measurement, and there are many circuit components and the cost is relatively high. Therefore, it is an urgent problem to develop a noise signal processing circuit with strong reliability, high precision and low cost. Utility Model Content

[0003] The utility model aims to provide a noise signal processing circuit and a train noise monitoring system, which improve the acquisition swing range of the noise signal and improve the anti-interference and crosstalk capabilities, and the noise signal processing circuit has strong reliability, high precision and low cost.

[0004] In order to solve the above technical problems, the utility model provides a noise signal processing circuit, including a noise signal analog processing circuit, wherein the noise signal analog processing circuit includes: a DC isolation circuit, a gain adjustment circuit, a low-pass filter circuit, a differential processing circuit and an analog-to-digital conversion module;

[0005] The signal input end of the DC isolation circuit is used to input the noise signal of the monitored object, the signal output end of the DC isolation circuit is connected to the input end of the gain adjustment circuit, the output end of the gain adjustment circuit is connected to the input end of the low-pass filter circuit, the output end of the low-pass filter circuit is connected to the input end of the differential processing circuit, the output end of the differential processing circuit is connected to the input end of the analog-to-digital conversion module, and the output end of the analog-to-digital conversion module serves as the output end of the noise signal analog processing circuit;

[0006] The DC isolation circuit is used to isolate the DC component of the noise signal, the gain adjustment circuit is used to adjust the gain of the signal output by the DC isolation circuit to a preset range, the low-pass filter circuit is used to low-pass filter the signal output by the gain adjustment circuit, the differential processing circuit is used to convert the signal output by the low-pass filter circuit into a differential signal, and the analog-to-digital conversion module is used to convert the differential signal into a digital signal and then output it.

[0007] Optionally, a constant current power supply for the microphone is also included;

[0008] The input end of the microphone constant current power supply is connected to an external input power supply, and the output end of the microphone constant current power supply is connected to a power supply end of a microphone used for collecting noise signals of the monitored object.

[0009] Optionally, it also includes a reset control and drive circuit and a reset switch circuit;

[0010] The input end of the reset control and drive circuit is connected to the output end of the analog-to-digital conversion module, the control end of the reset control and drive circuit is connected to the control end of the reset switch circuit, and the reset switch circuit is arranged between the output end of the microphone constant current power supply and the power supply end of the microphone;

[0011] The reset control and driving circuit is used to control the reset switch circuit to be disconnected when the channel transmitting the noise signal is abnormal, so as to power off the microphone.

[0012] Optionally, the microphone constant current power supply includes a power input filter circuit, a power isolation circuit, a capacitor filter circuit and a microphone sub-power supply branch, the microphone sub-power supply branch corresponds to the microphone one by one, and each of the microphone sub-power supply branches includes an inductor filter circuit and a voltage-current constant current conversion circuit;

[0013] The input end of the power input filter circuit is connected to the external input power supply, the output end of the power input filter circuit is connected to the input end of the power isolation circuit, the output end of the power isolation circuit is connected to the input end of the capacitor filter circuit, the output end of the capacitor filter circuit is connected to the input end of each of the microphone sub-power supply branches, and the output end of each of the microphone sub-power supply branches is respectively connected to the power supply end of the corresponding microphone;

[0014] The input end of the inductor filter circuit serves as the input end of the microphone sub-power supply branch, the output end of the inductor filter circuit is connected to the input end of the voltage-current constant current conversion circuit, and the output end of the voltage-current constant current conversion circuit serves as the output end of the microphone sub-power supply branch;

[0015] The power input filter circuit is used to filter the signal output by the external input power supply, the power isolation circuit is used to isolate the external input power supply from the subsequent circuit, the capacitor filter is used to reduce the ripple noise of the external input power supply, the inductor filter circuit is used for secondary isolation and filtering, and the voltage-to-current constant current conversion circuit is used to convert voltage into current output.

[0016] Optionally, the DC blocking circuit includes a first capacitor, the gain adjustment circuit includes a first resistor, a second resistor and a first operational amplifier, the low-pass filter circuit includes a second operational amplifier and N stages of resistor-capacitor filter circuits connected in parallel, and the differential processing circuit includes a third operational amplifier, a fourth operational amplifier, and third to tenth resistors, where N is a positive integer;

[0017] The first end of the first capacitor is connected to the power supply end of the microphone constant current power supply and the positive input end of the noise signal of the microphone, the second end of the first capacitor is connected to the first end of the first resistor, the second end of the first resistor is respectively connected to the first end of the second resistor and the positive input end of the first operational amplifier, the second end of the second resistor is connected to the negative input end of the noise signal of the microphone, the inverting input end of the first operational amplifier is connected to its own output end and the common end connected and the negative input end of the noise signal of the microphone are used together as two output ends of the gain adjustment circuit, and the two output ends of the gain adjustment circuit are respectively connected to the two input ends of the low-pass filter circuit;

[0018] Two terminals on a first side of the circuit after the N-stage resistor-capacitor filter circuits are connected in parallel serve as two input ends of the low-pass filter circuit, and two terminals on the other side of the circuit after the parallel connection are respectively connected to the non-inverting input end and the inverting input end of the second operational amplifier, and the inverting input end of the second operational amplifier is connected to its own output end, and the common end of the connections serves as the output end of the low-pass filter module;

[0019] The first end of the third resistor is connected to the output end of the second operational amplifier, the second end of the third resistor is respectively connected to the first end of the fourth resistor and the non-inverting input end of the third operational amplifier, the second end of the fourth resistor is connected to a power supply, the inverting input end of the third operational amplifier is respectively connected to the first end of the fifth resistor and the first end of the sixth resistor, the second end of the fifth resistor is grounded, and the second end of the sixth resistor is connected to the output end of the third operational amplifier, and the common end of the connections serves as the first differential output end of the differential processing circuit;

[0020] The first end of the seventh resistor is grounded, the second end of the seventh resistor is respectively connected to the first end of the eighth resistor and the non-inverting input end of the fourth operational amplifier, the second end of the eighth resistor is connected to a power supply, the inverting input end of the fourth operational amplifier is connected to the first end of the ninth resistor and the first end of the tenth resistor, the second end of the ninth resistor is connected to the output end of the second operational amplifier, the second end of the tenth resistor is connected to the output end of the fourth operational amplifier, and the common end of the connections serves as the second differential output end of the differential processing circuit.

[0021] Optionally, it also includes an op amp positive power supply and an op amp negative power supply;

[0022] The positive power supply terminal of the operational amplifier positive power supply is respectively connected to the positive power supply terminal of the first operational amplifier, the positive power supply terminal of the second operational amplifier, the positive power supply terminal of the third operational amplifier, and the positive power supply terminal of the fourth operational amplifier;

[0023] The negative power supply end of the operational amplifier negative power supply is respectively connected to the negative power supply end of the first operational amplifier, the negative power supply end of the second operational amplifier, the negative power supply end of the third operational amplifier and the negative power supply end of the fourth operational amplifier.

[0024] Optionally, the operational amplifier positive power supply includes a first input filter circuit, a first switching power supply, a first capacitor filter circuit and a first linear power supply connected in sequence, and the operational amplifier negative power supply includes a second input filter circuit, a second switching power supply, a second capacitor filter circuit and a second linear power supply connected in sequence;

[0025] The first input filter circuit is used to filter the primary power supply voltage, the first switching power supply is used to step down the filtered primary power supply voltage into a first positive voltage, the first capacitor filter circuit is used to filter the voltage output by the first switching power supply, the first linear power supply is used to reduce ripple noise and step down the first positive voltage into a second positive voltage, wherein the first positive voltage is a voltage within the voltage input range of the first linear power supply, and the second positive voltage is a voltage required by the positive power supply terminal of each of the operational amplifiers in the noise signal analog processing circuit;

[0026] The second input filter circuit is used to filter the primary power supply voltage, the second switching power supply is used to step down the filtered primary power supply voltage into a first negative voltage, the second capacitor filter circuit is used to filter the voltage output by the second switching power supply, and the second linear power supply is used to reduce ripple noise and step down the first negative voltage into a second negative voltage, wherein the first negative voltage is a voltage within the voltage input range of the second linear power supply, and the second negative voltage is the voltage required for the negative power supply terminal of each of the operational amplifiers in the noise signal analog processing circuit.

[0027] Optionally, it further includes an output filter circuit for filtering the differential signal output by the differential processing circuit, wherein the output filter circuit includes a second capacitor, a third capacitor and a fourth capacitor;

[0028] The first end of the second capacitor is grounded, the second end of the second capacitor is respectively connected to the output end of the third operational amplifier and the first end of the third capacitor, the second end of the third capacitor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is grounded;

[0029] The common end of the second capacitor connected to the third capacitor and the common end of the fourth capacitor connected to the third capacitor are respectively used as two output ends of the output filter circuit, and the two output ends of the output filter circuit are connected to the input end of the analog-to-digital conversion module.

[0030] Optionally, two clamping circuits are further included for clamping signals output from two output terminals of the output filter circuit, and the clamping circuits include a first diode and a second diode;

[0031] The cathode of the first diode is connected to a power supply, the anode of the first diode is connected to the cathode of the second diode and the common end of the connections is connected to the output end of the output filter circuit, and the anode of the second diode is grounded.

[0032] To solve the above technical problems, the present application also provides a train noise monitoring system, including a noise monitor and a microphone group, wherein the noise monitor includes any of the above noise signal processing circuits, the microphone group is used to collect noise signals of the monitored object, and the microphone group includes at least one microphone.

[0033] Optionally, the microphone is insulated from the train body, the microphone is connected to the noise monitor via a coaxial cable and a coaxial connector, the housing of the microphone is connected to the shielding layer of the coaxial cable, the coaxial connector is insulated from the housing of the noise monitor, and the shielding layer of the coaxial cable is directly connected to the signal ground of the noise monitor as a ground wire.

[0034] The beneficial effect of the utility model is to provide a noise signal processing circuit and a train noise monitoring system, including a DC isolation circuit, a gain adjustment circuit, a low-pass filter circuit, a differential processing circuit and an analog-to-digital conversion module. The noise signal of the monitored object is isolated from the DC component by the DC isolation circuit, gain adjusted by the gain adjustment circuit, low-pass filtered by the low-pass filter circuit, converted into a differential signal by the differential processing circuit, and then converted into a digital signal by the analog-to-digital conversion module for output. The link for processing the noise signal in the present application includes a noise signal analog processing circuit, which includes isolating the DC component of the noise signal input by the microphone, low-pass anti-aliasing filtering, converting the single-ended signal to a differential signal, and output interface protection processing, thereby improving the acquisition swing range of the noise signal and improving the anti-interference and crosstalk capabilities; at the same time, a dual power supply mode of the noise signal analog processing circuit is designed, and the noise of the circuit itself is reduced by adopting low-ripple noise power supply, using differential processing of low circuit noise operational amplifiers, and other measures, thereby meeting the effective processing of weak noise signals and greatly reducing the circuit cost; in addition, the present application also provides a constant current power supply for the microphone and a shielding solution for the microphone and the instrument, providing a complete solution for noise signal processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 A schematic diagram of the structure of a noise signal processing circuit provided in this application;

[0037] Figure 2 A schematic diagram of the structure of a constant current power supply for a microphone in a noise signal processing circuit provided in the present application;

[0038] Figure 3 A schematic diagram of the structure of a reset control circuit in a noise signal processing circuit provided in the present application;

[0039] Figure 4 A circuit diagram of a noise signal simulation processing circuit in the noise signal processing circuit provided in the present application;

[0040] Figure 5 A schematic diagram of the structure of a power supply for a noise simulation signal processing circuit in a noise signal processing circuit provided in the present application;

[0041] Figure 6This is a schematic diagram of the structure of the noise signal acquisition and shielding link in the train noise monitoring system provided in this application. DETAILED DESCRIPTION

[0042] The core of the utility model is to provide a noise signal processing circuit and a train noise monitoring system, which improves the acquisition swing range of the noise signal and improves the anti-interference and crosstalk capabilities, and is a noise signal processing circuit with strong reliability, high precision and low cost.

[0043] In order to make the purpose, technical solution and advantages of the embodiment of the utility model clearer, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0044] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a noise signal processing circuit provided in the present application, wherein the noise signal processing circuit includes a noise signal analog processing circuit, and the noise signal analog processing circuit includes: a DC isolation circuit 01, a gain adjustment circuit 02, a low-pass filter circuit 03, a differential processing circuit 04, and an analog-to-digital conversion module 05;

[0045] The signal input end of the DC isolation circuit 01 is used to input the noise signal of the monitored object, the signal output end of the DC isolation circuit 01 is connected to the input end of the gain adjustment circuit 02, the output end of the gain adjustment circuit 02 is connected to the input end of the low-pass filter circuit 03, the output end of the low-pass filter circuit 03 is connected to the input end of the differential processing circuit 04, the output end of the differential processing circuit 04 is connected to the input end of the analog-to-digital conversion module 05, and the output end of the analog-to-digital conversion module 05 serves as the output end of the noise signal analog processing circuit;

[0046] The DC isolation circuit 01 is used to isolate the DC component of the noise signal, the gain adjustment circuit 02 is used to adjust the gain of the signal output by the DC isolation circuit 01 to a preset range, the low-pass filter circuit 03 is used to low-pass filter the signal output by the gain adjustment circuit 02, the differential processing circuit 04 is used to convert the signal output by the low-pass filter circuit 03 into a differential signal, and the analog-to-digital conversion module 05 is used to convert the differential signal into a digital signal and then output it.

[0047] In view of the problems of collecting, processing, diagnosing and improving noise signals in rail transit, the present application provides a noise signal processing circuit to provide basic data support for improving and enhancing the riding comfort of rail transit. In this embodiment, the noise signal processing circuit includes a noise signal simulation processing circuit, which processes the noise signal through isolating the DC component, gain adjustment, low-pass filtering and differential conversion, and then performs analog-to-digital conversion and outputs it, so that the noise signal processed by the noise signal processing circuit can be accurately analyzed, diagnosed and improved.

[0048] Specifically, in the present embodiment, the noise signal analog processing circuit includes a direct-current isolation circuit 01, a gain adjustment circuit 02, a low-pass filter circuit 03, a differential processing circuit 04 and an analog-to-digital conversion module 05 connected in sequence. According to the symmetrical characteristics of the noise signal, the direct-current component in the noise signal is first isolated by the direct-current isolation circuit 01, and the alternating current component in the noise signal is taken. In practical applications, the cut-off frequency of the direct-current isolation circuit 01 can be set to be less than 20HZ to meet the effective range characteristics of the noise signal. The noise signal processed by the direct-current isolation circuit 01 is gain-adjusted by the gain adjustment circuit 02, while taking into account the swing range and the sound pressure level measurement range. The noise signal output by the gain adjustment circuit 02 is low-pass anti-aliasing filtered by the low-pass filter circuit 03, and the filtering parameters need to meet the low attenuation and fidelity of the effective signal in the band, and meet the digital filtering and resampling requirements of the post-stage analog-to-digital conversion module 05. A signal follower circuit can also be set between the low-pass filter circuit 03 and the differential processing circuit 04, and the noise signal is followed and impedance matched by the signal follower circuit. The common mode noise signal is differentially converted by the differential processing circuit 04 (the signal after the noise signal differential conversion corresponds to Figure 1 Vp and Vn in the circuit) to improve the anti-interference ability of the noise signal, reduce the circuit noise, and adapt and expand the signal swing range. In addition, a circuit for differential filtering of the differential signal, a circuit for common mode filtering, and a circuit for output clamping protection can be set between the differential processing circuit 04 and the analog-to-digital conversion module 05.

[0049] The analog-to-digital conversion module 05 converts the noise signal in the form of the first differential signal and the second differential signal from an analog signal to a digital signal, so as to perform subsequent data processing, analysis and diagnosis of the noise signal. The analog-to-digital converter can use a 24-bit ADC (Analog-to-digital converter) chip to achieve high-precision synchronous acquisition and high-resolution conversion.

[0050] In summary, this embodiment provides a noise signal processing circuit, including a DC isolation circuit 01, a gain adjustment circuit 02, a low-pass filter circuit 03, a differential processing circuit 04 and an analog-to-digital conversion module 05. The noise signal of the object is isolated from the DC component by the DC isolation circuit 01, gain adjusted by the gain adjustment circuit 02, low-pass filtered by the low-pass filter circuit 03, converted into a differential signal by the differential processing circuit 04, and then converted into a digital signal by the analog-to-digital conversion module 05 for output. The circuit includes the isolation of the DC component of the noise signal, low-pass anti-aliasing filtering, and single-ended to differential signal processing, which improves the acquisition swing range of the noise signal, and improves the anti-interference and crosstalk capabilities, and is a noise signal processing circuit with high reliability, high precision and low cost.

[0051] Based on the above embodiments:

[0052] As an optional embodiment, it also includes a microphone constant current power supply 10;

[0053] The input end of the microphone constant current power supply 10 is connected to an external input power supply, and the output end of the microphone constant current power supply 10 is connected to a power supply end of a microphone for collecting noise signals of a monitoring object.

[0054] In this embodiment, the noise signal processing circuit also includes a microphone constant current power supply 10 for supplying constant current to the microphone, and the microphone is used to collect the noise signal of the monitored object. Figure 2 , Figure 2 A schematic diagram of the structure of a constant current power supply for a microphone in a noise signal processing circuit provided in the present application. Figure 2 Where Vin is the voltage output by the external input power supply. In order to reduce the noise in the noise signal transmission channel, the microphone constant current power supply 10 is filtered and the power supply is isolated to reduce the ripple noise of the power supply. In addition, in the case of multiple microphones, the power supplies of each microphone share a power isolation circuit, which is economical.

[0055] Specifically, the microphone constant current power supply 10 includes a power input filter circuit, a power isolation circuit, a capacitor filter circuit and a microphone sub-power supply branch, the microphone sub-power supply branch corresponds to the microphone one by one, and each microphone sub-power supply branch includes an inductor filter circuit and a voltage-current constant current conversion circuit;

[0056] The input end of the power input filter circuit is connected to the external input power supply, the output end of the power input filter circuit is connected to the input end of the power isolation circuit, the output end of the power isolation circuit is connected to the input end of the capacitor filter circuit, the output end of the capacitor filter circuit is connected to the input end of each microphone sub-power supply branch, and the output end of each microphone sub-power supply branch is respectively connected to the power supply end of the corresponding microphone;

[0057] The input end of the inductor filter circuit is used as the input end of the microphone sub-power supply branch, the output end of the inductor filter circuit is connected to the input end of the voltage-current constant current conversion circuit, and the output end of the voltage-current constant current conversion circuit is used as the output end of the microphone sub-power supply branch;

[0058] The power input filter circuit is used to filter the signal output by the external input power supply, the power isolation circuit is used to isolate the external input power supply from the subsequent circuit, the capacitor filter is used to reduce the ripple noise of the external input power supply, the inductor filter circuit is used for secondary isolation and filtering, and the voltage-current constant current conversion circuit is used to convert voltage into current output.

[0059] In this embodiment, in order to reduce the crosstalk between audio channels transmitting noise signals and improve the quality of noise signal acquisition and the accuracy of the swing range, an inductive filter circuit is used for secondary isolation and filtering of each microphone sub-power supply branch; a constant current diode is used for voltage / current conversion to improve the economy and reliability of noise signal acquisition.

[0060] As an optional embodiment, it also includes a reset control and drive circuit and a reset switch circuit;

[0061] The input end of the reset control and drive circuit is connected to the output end of the analog-to-digital conversion module 05, the control end of the reset control and drive circuit is connected to the control end of the reset switch circuit, and the reset switch circuit is arranged between the output end of the microphone constant current power supply 10 and the power supply end of the microphone;

[0062] The reset control and drive circuit is used to control the reset switch circuit to disconnect when the channel transmitting the noise signal is abnormal, so that the microphone is powered off.

[0063] In this embodiment, in order to perform self-test on the audio channel transmitting the noise signal to confirm whether the working status of the software and hardware is normal and whether the data is reliable, a reset control and drive circuit and a reset switch circuit are also set in the noise signal processing circuit. Figure 3 , Figure 3 The present invention provides a schematic diagram of the structure of a reset control circuit in a noise signal processing circuit. The reset control and drive circuit is used to control the reset switch circuit to disconnect when a channel transmitting a noise signal is abnormal, so that the microphone is powered off.

[0064] As an optional embodiment, the DC isolation circuit 01 includes a first capacitor, the gain adjustment circuit 02 includes a first resistor, a second resistor and a first operational amplifier, the low-pass filter circuit 03 includes a second operational amplifier and N stages of resistor and capacitor filter circuits connected in parallel, and the differential processing circuit 04 includes a third operational amplifier, a fourth operational amplifier, and third to tenth resistors, where N is a positive integer;

[0065] The first end of the first capacitor is connected to the power supply end of the microphone constant current power supply 10 and the positive input end of the microphone noise signal, the second end of the first capacitor is connected to the first end of the first resistor, the second end of the first resistor is respectively connected to the first end of the second resistor and the positive input end of the first operational amplifier, the second end of the second resistor is connected to the negative input end of the microphone noise signal, the inverting input end of the first operational amplifier is connected to its own output end and the common end connected to the negative input end of the microphone noise signal together as two output ends of the gain adjustment circuit are respectively connected to the two input ends of the low-pass filter circuit 03;

[0066] The two terminals on the first side of the circuit after the N-stage resistor-capacitor filter circuit is connected in parallel are used as the two input terminals of the low-pass filter circuit 03, and the two terminals on the other side of the circuit after the parallel connection are respectively connected to the non-inverting input terminal and the inverting input terminal of the second operational amplifier, and the inverting input terminal of the second operational amplifier is connected to its own output terminal and the common terminal of the connection is used as the output terminal of the low-pass filter module;

[0067] The first end of the third resistor is connected to the output end of the second operational amplifier, the second end of the third resistor is respectively connected to the first end of the fourth resistor and the non-inverting input end of the third operational amplifier, the second end of the fourth resistor is connected to the power supply, the inverting input end of the third operational amplifier is respectively connected to the first end of the fifth resistor and the first end of the sixth resistor, the second end of the fifth resistor is grounded, the second end of the sixth resistor is connected to the output end of the third operational amplifier, and the common end of the connections serves as the first differential output end of the differential processing circuit 04;

[0068] The first end of the seventh resistor is grounded, the second end of the seventh resistor is respectively connected to the first end of the eighth resistor and the non-inverting input terminal of the fourth operational amplifier, the second end of the eighth resistor is connected to the power supply, the inverting input terminal of the fourth operational amplifier is connected to the first end of the ninth resistor and the first end of the tenth resistor, the second end of the ninth resistor is connected to the output terminal of the second operational amplifier, the second end of the tenth resistor is connected to the output terminal of the fourth operational amplifier, and the common end of the connections serves as the second differential output terminal of the differential processing circuit 04.

[0069] As an optional embodiment, it further includes an output filter circuit for filtering the differential signal output by the differential processing circuit 04, and the output filter circuit includes a second capacitor, a third capacitor and a fourth capacitor;

[0070] The first end of the second capacitor is grounded, the second end of the second capacitor is respectively connected to the output end of the third operational amplifier and the first end of the third capacitor, the second end of the third capacitor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is grounded;

[0071] The common end where the second capacitor is connected to the third capacitor and the common end where the fourth capacitor is connected to the third capacitor serve as two output ends of the output filter circuit respectively. The two output ends of the output filter circuit are connected to the input end of the analog-to-digital conversion module 05 .

[0072] As an optional embodiment, it further includes two clamping circuits for clamping signals output from two output terminals of the output filter circuit, the clamping circuits including a first diode and a second diode;

[0073] The cathode of the first diode is connected to the power supply, the anode of the first diode is connected to the cathode of the second diode, and the common end of the connections is connected to the output end of the output filter circuit, and the anode of the second diode is grounded.

[0074] In the above embodiments, specific implementation circuits of the noise signal simulation processing circuit are provided. Please refer to Figure 4 , Figure 4 This is a circuit diagram of the noise signal analog processing circuit in the noise signal processing circuit provided in this application. The noise signal analog processing circuit isolates the DC component of the noise signal (20Hz~20kHz), performs low-pass anti-mixing filtering, single-ended to differential signal processing, and output interface protection. By adopting low-ripple noise power supply, using low circuit noise op amps and differential signal processing, the circuit noise of the circuit itself is reduced to 50uV, which can meet the effective processing of weak noise analog signals. Figure 4 Where Vin- and Vin+ are noise signals, 24v&4mA are the signals output from the power supply end of the microphone constant current power supply 10, C1 is the first capacitor, R1 to R10 are the first resistor to the tenth resistor respectively, N2A, N2B, N2C and N2D are the first operational amplifier, the second operational amplifier, the third operational amplifier and the fourth operational amplifier respectively, C1 to C4 are the first capacitor to the fourth capacitor respectively, D1 and D2 are the first diode and the second diode respectively, and VoutP and VoutN are a pair of differential signals output by the noise signal analog processing circuit.

[0075] In the DC isolation circuit 01, the first capacitor removes the DC component of the noise signal input by the microphone and retains the AC component (frequency>20Hz). The maximum range after DC isolation and gain adjustment is -7V~+7V. The low-pass filter circuit 03 performs two-stage RC passive low-pass anti-mixing filtering and signal following on the noise signal. The differential processing circuit 04 realizes the conversion of the single-ended noise signal into a differential signal, adapts to the differential input interface of the ADC chip, can effectively expand the swing of the noise signal, and reduce the common mode interference, which is very beneficial for measuring the microvolt noise signal of low sound pressure. The second capacitor, the third capacitor and the fourth capacitor constitute the output filter circuit to further filter the noise signal. The first diode and the second diode clamp the output signal in the range of 0~5V to protect the input interface of the ADC chip. In addition, the vibration / noise signal preprocessing and differential conversion of each channel are realized by the same low circuit noise, low zero drift four-gate operational amplifier, which has low cost, high integration and low circuit noise.

[0076] As an optional embodiment, it also includes an operational amplifier positive power supply and an operational amplifier negative power supply;

[0077] The positive power supply terminal of the operational amplifier positive power supply is respectively connected to the positive power supply terminal of the first operational amplifier, the positive power supply terminal of the second operational amplifier, the positive power supply terminal of the third operational amplifier and the positive power supply terminal of the fourth operational amplifier;

[0078] The negative power supply terminal of the operational amplifier negative power supply is respectively connected to the negative power supply terminal of the first operational amplifier, the negative power supply terminal of the second operational amplifier, the negative power supply terminal of the third operational amplifier and the negative power supply terminal of the fourth operational amplifier.

[0079] Please refer to Figure 5 , Figure 5 The present invention provides a schematic diagram of a power supply for a noise analog signal processing circuit in a noise signal processing circuit. Considering that the noise signal is a bipolar signal, in order to increase the swing range of the noise signal and adapt to the post-stage differential processing and analog-to-digital conversion, this embodiment adopts a dual power supply mode to power the noise analog signal processing circuit.

[0080] Specifically, the operational amplifier positive power supply includes a first input filter circuit, a first switching power supply, a first capacitor filter circuit and a first linear power supply connected in sequence, and the operational amplifier negative power supply includes a second input filter circuit, a second switching power supply, a second capacitor filter circuit and a second linear power supply connected in sequence;

[0081] The first input filter circuit is used to filter the primary power supply voltage, the first switching power supply is used to step down the filtered primary power supply voltage into a first positive voltage, the first capacitor filter circuit is used to filter the voltage output by the first switching power supply, and the first linear power supply is used to reduce ripple noise and step down the first positive voltage into a second positive voltage, wherein the first positive voltage is a voltage within the voltage input range of the first linear power supply, and the second positive voltage is a voltage required by the positive power supply terminal of each operational amplifier in the noise signal analog processing circuit;

[0082] The second input filter circuit is used to filter the primary power supply voltage, the second switching power supply is used to step down the filtered primary power supply voltage to a first negative voltage, the second capacitor filter circuit is used to filter the voltage output by the second switching power supply, and the second linear power supply is used to reduce ripple noise and step down the first negative voltage to a second negative voltage, wherein the first negative voltage is a voltage within the voltage input range of the second linear power supply, and the second negative voltage is the voltage required by the negative power supply terminal of each operational amplifier in the noise signal analog processing circuit.

[0083] Since the noise sound pressure level is represented as a logarithm, the swing range is very large. For example, a microphone with a sensitivity of 45mV / Pa and a measurement range of 17dB to 134dB has a corresponding output sinusoidal voltage signal range of 10uV to 7V. It is assumed that the noise signal above 54dB needs to be measured, and the effective signal needs to be measured to 0.7mV. Therefore, the static noise of the noise analog signal processing circuit is required to be less than 0.7mV. It can be seen that the power supply for the noise analog signal processing circuit is very important. In this scheme, the positive power supply and the negative power supply of the op amp both use two-stage power conversion. The first stage is a switching power supply to realize the conversion of voltage level and positive and negative power supply. The second stage uses LDO (linear power supply) for secondary conversion to reduce the power output ripple noise and improve power efficiency.

[0084] The first stage of the positive power supply of the operational amplifier realizes the conversion from the primary power supply voltage to the first positive voltage (+24V / +V1) based on the first switching power supply to adapt to the input voltage range of the first linear power supply of the subsequent stage; the first linear power supply realizes the conversion from the first positive voltage to the second positive voltage (+V1 / +V2), which is used to reduce the ripple noise of the power supply of the analog signal processing circuit, and provides a high-quality power supply foundation for the processing of weak noise signals. The first stage of the negative power supply of the operational amplifier realizes the conversion from the primary power supply voltage to the first negative voltage (+24V / -V1) based on the second switching power supply to adapt to the input voltage range of the second linear power supply of the subsequent stage; the second linear power supply chip realizes the conversion from the first negative voltage to the second negative voltage (-V1 / -V2), which is mainly used to reduce the ripple noise of the negative power supply of the analog signal processing circuit, and provides a high-quality power supply foundation for the processing of weak noise signals.

[0085] In summary, the present application provides a noise signal processing circuit, including a DC isolation circuit 01, a gain adjustment circuit 02, a low-pass filter circuit 03, a differential processing circuit 04 and an analog-to-digital conversion module 05. The noise signal of the monitored object is isolated from the DC component by the DC isolation circuit 01, gain adjusted by the gain adjustment circuit 02, low-pass filtered by the low-pass filter circuit 03, converted into a differential signal by the differential processing circuit 04, and then converted into a digital signal by the analog-to-digital conversion module 05 for output. The link for processing the noise signal in the present application includes a noise signal analog processing circuit, which includes isolating the DC component of the noise signal input by the microphone, low-pass anti-aliasing filtering, converting the single-ended signal to a differential signal, and output interface protection processing, thereby improving the acquisition swing range of the noise signal and improving the anti-interference and crosstalk capabilities; at the same time, a dual power supply mode of the noise signal analog processing circuit is designed, and the noise of the circuit itself is reduced by adopting low-ripple noise power supply, using differential processing of low circuit noise operational amplifiers, and other measures, thereby meeting the effective processing of weak noise signals and greatly reducing the circuit cost; in addition, the present application also provides a constant current power supply for the microphone and a shielding solution for the microphone and the instrument, providing a complete solution for noise signal processing.

[0086] The present application also provides a train noise monitoring system, including a noise monitor and a microphone group, wherein the noise monitor includes any of the above-mentioned noise signal processing circuits, and the microphone group is used to collect noise signals of the monitored object, and the microphone group includes at least one microphone.

[0087] For a detailed introduction to the train noise monitoring system provided in the present application, please refer to the above-mentioned embodiment of the noise signal processing circuit, and the present application will not elaborate on it here.

[0088] Based on the above embodiments:

[0089] As an optional embodiment, the microphone is insulated from the train body, the microphone is connected to the noise monitor through a coaxial cable and a coaxial connector, the microphone housing is connected to the shielding layer of the coaxial cable, the coaxial connector is insulated from the housing of the noise monitor, and the shielding layer of the coaxial cable is directly connected to the signal ground of the noise monitor as a ground wire.

[0090] Please refer to Figure 6 , Figure 6A schematic diagram of the structure of the noise signal acquisition and shielding link in the train noise monitoring system provided in the present application. In this embodiment, the microphone is insulated from the train body to reduce electromagnetic interference. The microphone and the noise monitor are connected using a coaxial cable and a coaxial connector, and the coaxial connector is used to transmit noise signals; the housing of the microphone is connected to the shielding layer of the coaxial cable, and the coaxial connector is insulated from the housing of the noise monitor. The shielding layer of the coaxial cable is directly connected to the signal ground of the noise monitor as a ground wire, thereby reducing electromagnetic interference. The coaxial cable and the noise monitor are connected via an SMA (SubMiniature Version A) coaxial connector, which can improve the connection reliability and the ability to adapt to train vibration and shock.

[0091] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. It should also be noted that in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, article or device. In the absence of further restrictions, the elements defined by the sentence "including one..." do not exclude the presence of other identical elements in the process, article or device including the elements.

[0092] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A noise signal processing circuit, characterized in that: It includes a noise signal analog processing circuit, which includes: a DC isolation circuit, a gain adjustment circuit, a low-pass filter circuit, a differential processing circuit and an analog-to-digital conversion module; The signal input end of the DC isolation circuit is used to input the noise signal of the monitored object, the signal output end of the DC isolation circuit is connected to the input end of the gain adjustment circuit, the output end of the gain adjustment circuit is connected to the input end of the low-pass filter circuit, the output end of the low-pass filter circuit is connected to the input end of the differential processing circuit, the output end of the differential processing circuit is connected to the input end of the analog-to-digital conversion module, and the output end of the analog-to-digital conversion module serves as the output end of the noise signal analog processing circuit; The DC isolation circuit is used to isolate the DC component of the noise signal, the gain adjustment circuit is used to adjust the gain of the signal output by the DC isolation circuit to a preset range, the low-pass filter circuit is used to low-pass filter the signal output by the gain adjustment circuit, the differential processing circuit is used to convert the signal output by the low-pass filter circuit into a differential signal, and the analog-to-digital conversion module is used to convert the differential signal into a digital signal and then output it.

2. The noise signal processing circuit according to claim 1, characterized in that: Also included is a constant current power supply for the microphone; The input end of the microphone constant current power supply is connected to an external input power supply, and the output end of the microphone constant current power supply is connected to a power supply end of a microphone used for collecting noise signals of the monitored object.

3. The noise signal processing circuit according to claim 2, characterized in that: It also includes a reset control and drive circuit and a reset switch circuit; The input end of the reset control and drive circuit is connected to the output end of the analog-to-digital conversion module, the control end of the reset control and drive circuit is connected to the control end of the reset switch circuit, and the reset switch circuit is arranged between the output end of the microphone constant current power supply and the power supply end of the microphone; The reset control and driving circuit is used to control the reset switch circuit to be disconnected when the channel transmitting the noise signal is abnormal, so as to power off the microphone.

4. The noise signal processing circuit according to claim 2, characterized in that: The microphone constant current power supply comprises a power input filter circuit, a power isolation circuit, a capacitor filter circuit and a microphone sub-power supply branch, the microphone sub-power supply branch corresponds to the microphone one by one, and each of the microphone sub-power supply branches comprises an inductor filter circuit and a voltage-current constant current conversion circuit; The input end of the power input filter circuit is connected to the external input power supply, the output end of the power input filter circuit is connected to the input end of the power isolation circuit, the output end of the power isolation circuit is connected to the input end of the capacitor filter circuit, the output end of the capacitor filter circuit is connected to the input end of each of the microphone sub-power supply branches, and the output end of each of the microphone sub-power supply branches is respectively connected to the power supply end of the corresponding microphone; The input end of the inductor filter circuit serves as the input end of the microphone sub-power supply branch, the output end of the inductor filter circuit is connected to the input end of the voltage-current constant current conversion circuit, and the output end of the voltage-current constant current conversion circuit serves as the output end of the microphone sub-power supply branch; The power input filter circuit is used to filter the signal output by the external input power supply, the power isolation circuit is used to isolate the external input power supply from the subsequent circuit, the capacitor filter is used to reduce the ripple noise of the external input power supply, the inductor filter circuit is used for secondary isolation and filtering, and the voltage-to-current constant current conversion circuit is used to convert voltage into current output.

5. The noise signal processing circuit according to claim 2, characterized in that: The DC blocking circuit includes a first capacitor, the gain adjustment circuit includes a first resistor, a second resistor and a first operational amplifier, the low-pass filter circuit includes a second operational amplifier and N stages of resistor-capacitor filter circuits connected in parallel, and the differential processing circuit includes a third operational amplifier, a fourth operational amplifier, and third to tenth resistors, where N is a positive integer; The first end of the first capacitor is connected to the power supply end of the microphone constant current power supply and the positive input end of the noise signal of the microphone, the second end of the first capacitor is connected to the first end of the first resistor, the second end of the first resistor is respectively connected to the first end of the second resistor and the positive input end of the first operational amplifier, the second end of the second resistor is connected to the negative input end of the noise signal of the microphone, the inverting input end of the first operational amplifier is connected to its own output end and the common end connected and the negative input end of the noise signal of the microphone are used together as two output ends of the gain adjustment circuit, and the two output ends of the gain adjustment circuit are respectively connected to the two input ends of the low-pass filter circuit; Two terminals on a first side of the circuit after the N-stage resistor-capacitor filter circuits are connected in parallel serve as two input ends of the low-pass filter circuit, and two terminals on the other side of the circuit after the parallel connection are respectively connected to the non-inverting input end and the inverting input end of the second operational amplifier, and the inverting input end of the second operational amplifier is connected to its own output end, and the common end of the connections serves as the output end of the low-pass filter module; The first end of the third resistor is connected to the output end of the second operational amplifier, the second end of the third resistor is respectively connected to the first end of the fourth resistor and the non-inverting input end of the third operational amplifier, the second end of the fourth resistor is connected to a power supply, the inverting input end of the third operational amplifier is respectively connected to the first end of the fifth resistor and the first end of the sixth resistor, the second end of the fifth resistor is grounded, the second end of the sixth resistor is connected to the output end of the third operational amplifier, and the common end of the connections serves as the first differential output end of the differential processing circuit; The first end of the seventh resistor is grounded, the second end of the seventh resistor is respectively connected to the first end of the eighth resistor and the non-inverting input end of the fourth operational amplifier, the second end of the eighth resistor is connected to a power supply, the inverting input end of the fourth operational amplifier is connected to the first end of the ninth resistor and the first end of the tenth resistor, the second end of the ninth resistor is connected to the output end of the second operational amplifier, the second end of the tenth resistor is connected to the output end of the fourth operational amplifier, and the common end of the connections serves as the second differential output end of the differential processing circuit.

6. The noise signal processing circuit according to claim 5, characterized in that: It also includes an op amp positive power supply and an op amp negative power supply; The positive power supply terminal of the operational amplifier positive power supply is respectively connected to the positive power supply terminal of the first operational amplifier, the positive power supply terminal of the second operational amplifier, the positive power supply terminal of the third operational amplifier, and the positive power supply terminal of the fourth operational amplifier; The negative power supply end of the operational amplifier negative power supply is respectively connected to the negative power supply end of the first operational amplifier, the negative power supply end of the second operational amplifier, the negative power supply end of the third operational amplifier and the negative power supply end of the fourth operational amplifier.

7. The noise signal processing circuit according to claim 6, characterized in that: The operational amplifier positive power supply includes a first input filter circuit, a first switching power supply, a first capacitor filter circuit and a first linear power supply connected in sequence, and the operational amplifier negative power supply includes a second input filter circuit, a second switching power supply, a second capacitor filter circuit and a second linear power supply connected in sequence; The first input filter circuit is used to filter the primary power supply voltage, the first switching power supply is used to step down the filtered primary power supply voltage into a first positive voltage, the first capacitor filter circuit is used to filter the voltage output by the first switching power supply, the first linear power supply is used to reduce ripple noise and step down the first positive voltage into a second positive voltage, wherein the first positive voltage is a voltage within the voltage input range of the first linear power supply, and the second positive voltage is a voltage required by the positive power supply terminal of each of the operational amplifiers in the noise signal analog processing circuit; The second input filter circuit is used to filter the primary power supply voltage, the second switching power supply is used to step down the filtered primary power supply voltage into a first negative voltage, the second capacitor filter circuit is used to filter the voltage output by the second switching power supply, and the second linear power supply is used to reduce ripple noise and step down the first negative voltage into a second negative voltage, wherein the first negative voltage is a voltage within the voltage input range of the second linear power supply, and the second negative voltage is the voltage required for the negative power supply terminal of each of the operational amplifiers in the noise signal analog processing circuit.

8. The noise signal processing circuit according to claim 5, characterized in that: Also includes an output filter circuit for filtering the differential signal output by the differential processing circuit, the output filter circuit includes a second capacitor, a third capacitor and a fourth capacitor; The first end of the second capacitor is grounded, the second end of the second capacitor is respectively connected to the output end of the third operational amplifier and the first end of the third capacitor, the second end of the third capacitor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is grounded; The common end of the second capacitor connected to the third capacitor and the common end of the fourth capacitor connected to the third capacitor are respectively used as two output ends of the output filter circuit, and the two output ends of the output filter circuit are connected to the input end of the analog-to-digital conversion module.

9. The noise signal processing circuit according to claim 8, characterized in that: Also included are two clamping circuits for clamping signals output from two output terminals of the output filter circuit, the clamping circuits comprising a first diode and a second diode; The cathode of the first diode is connected to a power supply, the anode of the first diode is connected to the cathode of the second diode and the common end of the connections is connected to the output end of the output filter circuit, and the anode of the second diode is grounded.

10. A train noise monitoring system, characterized in that: The invention comprises a noise monitor and a microphone group, wherein the noise monitor comprises the noise signal processing circuit according to any one of claims 1 to 9, and the microphone group is used to collect noise signals of a monitored object, and the microphone group comprises at least one microphone.

11. The train noise monitoring system according to claim 10, characterized in that: The microphone is insulated from the train body, connected to the noise monitor via a coaxial cable and a coaxial connector, the housing of the microphone is connected to the shielding layer of the coaxial cable, the coaxial connector is insulated from the housing of the noise monitor, and the shielding layer of the coaxial cable is directly connected to the signal ground of the noise monitor as a ground wire.

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