CN115469295A - Laser radar receiving circuit, analog front end, laser radar and signal processing method - Google Patents
Laser radar receiving circuit, analog front end, laser radar and signal processing method Download PDFInfo
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- CN115469295A CN115469295A CN202211359371.XA CN202211359371A CN115469295A CN 115469295 A CN115469295 A CN 115469295A CN 202211359371 A CN202211359371 A CN 202211359371A CN 115469295 A CN115469295 A CN 115469295A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/4861—Circuits for detection, sampling, integration or read-out
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/487—Extracting wanted echo signals, e.g. pulse detection
- G01S7/4876—Extracting wanted echo signals, e.g. pulse detection by removing unwanted signals
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Abstract
The embodiment of the invention provides a laser radar receiving circuit, an analog front end, a laser radar and a signal processing method, and relates to the technical field of laser radars. The laser radar receiving circuit comprises a photoelectric conversion module, a transimpedance amplification module, a signal processing module and a reference voltage output module, wherein the transimpedance amplification module is electrically connected with the photoelectric conversion module and the signal processing module, and the reference voltage output module is electrically connected with the signal processing module and the transimpedance amplification module. The photoelectric conversion module converts a received optical signal into a current signal, the transimpedance amplification module converts the current signal into a voltage signal, the signal processing module adjusts the reference voltage provided by the reference voltage output module for the transimpedance amplification module according to the voltage signal, and then adjusts the voltage signal output by the transimpedance amplification module, so that the output dynamic range of the transimpedance amplification module is adjusted by adjusting the reference voltage of the transimpedance amplification module, and output saturation under a strong optical signal is effectively inhibited.
Description
Technical Field
The invention relates to the technical field of laser radars, in particular to a laser radar receiving circuit, an analog front end, a laser radar and a signal processing method.
Background
Long-distance and high-precision ranging is a core requirement of a laser radar system. To increase the detection distance, increasing the transmission power of the laser and the sensitivity of the receiving circuit is one of the most common approaches; correspondingly, the stronger the transmitting power of the laser radar is, the higher the receiving sensitivity is, and a "blind area" of detection can easily occur in a short-distance ranging scene or in the face of a high-reflectivity object, that is, the photocurrent generated by the strong light saturates the output signal of the laser radar receiving circuit, so that the problem of point cloud abnormity of the laser radar in a section or the whole measuring range is caused.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a lidar receiving circuit, an analog front end, a lidar and a signal processing method, so as to solve the problem that in the prior art, when the lidar receiving circuit receives a strong light signal, output signal saturation occurs, and thus point cloud abnormality is caused.
In order to achieve the above purpose, the embodiment of the present invention adopts the following technical solutions:
in a first aspect, the invention provides a laser radar receiving circuit, which includes a photoelectric conversion module, a transimpedance amplification module, a signal processing module, and a reference voltage output module, wherein the transimpedance amplification module is electrically connected to both the photoelectric conversion module and the signal processing module, the reference voltage output module is electrically connected to both the signal processing module and the transimpedance amplification module, and the reference voltage output module provides a reference voltage for the transimpedance amplification module under the control of the signal processing module;
the photoelectric conversion module is used for converting the received optical signal into a current signal;
the transimpedance amplification module is used for converting the current signal into a voltage signal;
the signal processing module is used for adjusting the size of the reference voltage output by the reference voltage output module according to the voltage signal, and further adjusting the size of the voltage signal output by the transimpedance amplification module.
In an optional embodiment, the transimpedance amplification module includes a first operational amplifier and a first resistor, a negative input terminal of the first operational amplifier is electrically connected to the photoelectric conversion module, a positive input terminal of the first operational amplifier is electrically connected to the reference voltage output module, an output terminal of the first operational amplifier is electrically connected to the signal processing module, and the first resistor is electrically connected between the negative input terminal and the output terminal of the first operational amplifier.
In an alternative embodiment, the reference voltage output module includes a plurality of switches and a plurality of voltage-dividing resistors connected in series between a power supply and ground, nodes corresponding to the number of the plurality of switches are formed among the plurality of voltage-dividing resistors, one end of each switch is electrically connected to a corresponding one of the nodes, the other end of each switch is electrically connected to the positive input end of the first operational amplifier, and the control end of each switch is electrically connected to the signal processing module;
the signal processing module is used for controlling one of the switches to be conducted according to the voltage signal, so that the magnitude of the reference voltage input to the positive input end of the first operational amplifier is adjusted.
In an optional implementation manner, the reference voltage output module includes a digital-to-analog conversion unit, and the digital-to-analog conversion unit is electrically connected to both the signal processing module and the positive input end of the first operational amplifier;
the signal processing module is used for outputting a digital control signal to the digital-to-analog conversion unit according to the voltage signal;
the digital-to-analog conversion unit is used for converting the digital control signal into a corresponding reference voltage.
In an optional embodiment, the lidar receiving circuit further includes a filtering module, an input end of the filtering module is electrically connected to the transimpedance amplification module, and an output end of the filtering module is electrically connected to the signal processing module;
the filtering module is used for filtering the voltage signal output by the transimpedance amplification module and outputting the voltage signal after filtering to the signal processing module.
In an optional embodiment, the filtering module includes a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, and a second operational amplifier;
the second resistor and the third resistor are connected in series between the transimpedance amplification module and the negative input end of the second operational amplifier; the fourth resistor is electrically connected between the positive input end and the output end of the second operational amplifier, one end of the fifth resistor is electrically connected with the positive input end of the second operational amplifier, and the other end of the fifth resistor is grounded;
one end of the first capacitor is electrically connected between the second resistor and the third resistor, and the other end of the first capacitor is electrically connected with the output end of the second operational amplifier; one end of the second capacitor is electrically connected between the third resistor and the negative input end of the second operational amplifier, and the other end of the second capacitor is grounded.
In an optional embodiment, the signal processing module includes a variable gain amplifying unit, an analog-to-digital conversion unit, and a logic control unit, the variable gain amplifying unit, the analog-to-digital conversion unit, and the logic control unit are electrically connected in sequence, the variable gain amplifying unit is further electrically connected to the transimpedance amplifying module, and the logic control unit is further electrically connected to the reference voltage output module;
the variable gain amplifying unit is used for amplifying the voltage signal output by the transimpedance amplifying module;
the analog-to-digital conversion unit is used for converting the amplified voltage signal into a digital signal;
the logic control unit is used for adjusting the reference voltage output by the reference voltage output module according to the digital signal.
In a second aspect, the present invention provides a signal processing method applied to the lidar receiving circuit according to any of the foregoing embodiments, the method including:
the photoelectric conversion module converts the received optical signal into a current signal;
the transimpedance amplification module converts the current signal into a voltage signal;
the signal processing module adjusts the magnitude of the reference voltage output by the reference voltage output module according to the voltage signal, and then adjusts the magnitude of the voltage signal output by the transimpedance amplification module.
In a third aspect, the present invention provides a lidar analog front end comprising a lidar receiving circuit according to any of the preceding embodiments.
In a fourth aspect, the present invention provides a lidar comprising the lidar analog front end of the preceding embodiments.
The laser radar receiving circuit comprises a photoelectric conversion module, a transimpedance amplification module, a signal processing module and a reference voltage output module, wherein the transimpedance amplification module is electrically connected with the photoelectric conversion module and the signal processing module, the reference voltage output module is electrically connected with the signal processing module and the transimpedance amplification module, and the reference voltage output module provides reference voltage for the transimpedance amplification module under the control of the signal processing module. The photoelectric conversion module converts a received optical signal into a current signal, the transimpedance amplification module converts the current signal into a voltage signal, and the signal processing module adjusts the reference voltage output by the reference voltage output module according to the voltage signal, so that the voltage signal output by the transimpedance amplification module is adjusted. This laser radar receiving circuit can be according to the voltage signal of transimpedance amplifier module output, adjust the reference voltage of transimpedance amplifier module in real time, along with reference voltage's change, the size of the voltage signal of transimpedance amplifier output also can change, realize the reference voltage through adjusting transimpedance amplifier module, adjust transimpedance amplifier module's output dynamic range, thereby effectively restrain the output saturation of laser radar receiving circuit under the highlight signal, the unusual problem of laser radar point cloud has been avoided, the range finding blind area has been reduced.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and those skilled in the art can also obtain other related drawings based on the drawings without inventive efforts.
Fig. 1 shows a block diagram of a lidar receiving circuit according to an embodiment of the present invention;
fig. 2 is a block diagram illustrating another structure of a lidar receiving circuit according to an embodiment of the present invention;
fig. 3 is a schematic circuit diagram illustrating a transimpedance amplification module in a laser radar receiving circuit according to an embodiment of the present invention;
fig. 4 is a schematic diagram illustrating a circuit structure of a reference voltage output module in a lidar receiving circuit according to an embodiment of the present invention;
FIG. 5 is a diagram showing an exemplary circuit configuration of the reference voltage output module of FIG. 4;
FIG. 6 shows a schematic diagram of adjusting the output dynamic range of a first operational amplifier by switching the reference voltage;
fig. 7 is a schematic diagram illustrating another circuit structure of a reference voltage output module in a laser radar receiving circuit according to an embodiment of the present invention;
FIG. 8 is a diagram showing an exemplary circuit configuration of the reference voltage output module of FIG. 7;
FIG. 9 shows a schematic diagram of adjusting the output dynamic range of the first operational amplifier by DAC adjusting the adjustment reference voltage;
fig. 10 shows a block diagram of another structure of a lidar receiving circuit provided in an embodiment of the present invention;
fig. 11 shows a schematic circuit diagram of a filter module;
FIG. 12 shows a circuit bode diagram of a filter module;
FIG. 13 shows a ranging diagram for a lidar in a high reflectivity obstacle condition;
FIG. 14 is a diagram showing an echo signal when a conventional lidar receiving circuit faces a high reflectivity object;
FIG. 15 is a diagram showing an echo signal when a laser radar receiving circuit provided by an embodiment of the present invention faces a high-reflectivity object;
fig. 16 is a schematic flow chart of a signal processing method according to an embodiment of the present invention.
Icon: 100-laser radar receiving circuit; 110-a photoelectric conversion module; 120-transimpedance amplification module; 130-a signal processing module; 140-a reference voltage output module; 150-a filtering module; 121-a first operational amplifier; 122 — a first resistance; 131-a variable gain amplification unit; 132-an analog-to-digital conversion unit; 133-a logic control unit; 141-switch; 142-voltage dividing resistors; 143-node; 144-a power supply; 145-a digital-to-analog conversion unit; 151-second resistance; 152-a third resistance; 153-fourth resistance; 154-fifth resistance; 155-a first capacitance; 156-a second capacitance; 157-second operational amplifier.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.
Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
In a conventional laser radar receiving circuit, a transimpedance amplifier is used for converting an echo pulse photocurrent into a voltage signal and has a linear transimpedance gain value, so that an output voltage of the receiving circuit is linearly proportional to an input optical power. To detect weak optical signals, the gain of the receiving circuit is typically set very high so that the magnitude of the signal amplification is sufficiently large. If the strong light signal is directly received at this time, because the photocurrent is too strong, the output signal of the transimpedance amplifier is saturated, the output pulse width of the transimpedance amplifier in a saturated state is widened, and if the arrival time interval of the next light pulse detected by the photosensor is not long enough, the generated current pulse is annihilated by the saturated signal, resulting in data loss.
Based on the above, the embodiment of the invention provides a laser radar receiving circuit, a simulation front end, a laser radar and a signal processing method, wherein the reference voltage of a transimpedance amplification module is adjusted in real time according to a voltage signal output by the transimpedance amplification module, so that the output dynamic range of the transimpedance amplification module is adjusted, and when the laser radar is in a short-distance ranging scene or faces a high-reflectivity object, the output signal saturation of the laser radar receiving circuit can be effectively inhibited, the problem of point cloud abnormity of the laser radar is avoided, and a ranging blind area is reduced.
Fig. 1 is a block diagram of a lidar receiving circuit 100 according to an embodiment of the present invention. The laser radar receiving circuit 100 includes a photoelectric conversion module 110, a transimpedance amplification module 120, a signal processing module 130, and a reference voltage output module 140, the transimpedance amplification module 120 is electrically connected to both the photoelectric conversion module 110 and the signal processing module 130, the reference voltage output module 140 is electrically connected to both the signal processing module 130 and the transimpedance amplification module 120, and the reference voltage output module 140 provides a reference voltage for the transimpedance amplification module 120 under the control of the signal processing module 130.
The photoelectric conversion module 110 is configured to convert a received optical signal into a current signal; the transimpedance amplification module 120 is configured to convert the current signal into a voltage signal; the signal processing module 130 is configured to adjust the magnitude of the reference voltage output by the reference voltage output module 140 according to the voltage signal, and further adjust the magnitude of the voltage signal output by the transimpedance amplification module 120.
In the present embodiment, the photoelectric conversion module 110 may employ a photoelectric sensor, such as a Photodiode (PD) or an Avalanche Photodiode (APD). After receiving the laser signal reflected by the object to be measured, the photoelectric conversion module 110 may generate a light-induced current signal proportional to the illumination intensity according to the photoelectric effect. The transimpedance amplifier 120 converts the current signal output by the photoelectric conversion module 110 into a voltage signal and outputs the voltage signal to the signal processing module 130 for processing.
In this embodiment, the signal processing module 130 may perform time of flight (TOF) calculation and signal pulse width and optical signal intensity analysis according to the received voltage signal, and adjust the magnitude of the reference voltage output by the reference voltage output module 140 according to the analysis result of the signal pulse width or the optical signal intensity.
In this embodiment, the reference voltage of the transimpedance amplification module 120 is the quiescent point V REF Since it is one of the key parameters that affect the output dynamic range of the transimpedance amplification module 120, the signal processing module 130 adjusts the reference voltage provided to the transimpedance amplification module 120 by the reference voltage output module 140, and can adjust the magnitude of the voltage signal output by the transimpedance amplification module 120, thereby achieving the purposes of optimizing the output dynamic range of the transimpedance amplification module 120 and suppressing the saturation of the output signal.
It should be noted that, in practical application, the key parameters that affect the output dynamic range of the transimpedance amplification module 120 may further include a working power supply VDD, a receiving gain, and the like, so that in an actual use process, the key parameters of the working power supply VDD, the receiving gain, and the like may also be adjusted according to scene needs, so as to greatly improve the output dynamic range of the transimpedance amplification module 120.
Therefore, the laser radar receiving circuit provided by the embodiment of the invention can adjust the reference voltage of the transimpedance amplification module in real time according to the voltage signal output by the transimpedance amplification module, the size of the voltage signal output by the transimpedance amplifier can also change along with the change of the reference voltage, and the adjustment of the output dynamic range of the transimpedance amplification module is realized by adjusting the reference voltage of the transimpedance amplification module, so that the output saturation of the laser radar receiving circuit under a strong light signal is effectively inhibited, the problem of point cloud abnormity of a laser radar is avoided, and the ranging blind area is reduced.
Optionally, after receiving the voltage signal output by the transimpedance amplification module 120, the signal processing module 130 needs to amplify the voltage signal and convert the analog signal into a digital signal, and finally performs algorithm processing and judgment based on the digital signal, so as to implement functions of calculating the flight time, analyzing the intensity of the optical signal, adjusting the output dynamic range of the transimpedance amplification module 120, and the like.
Based on this, referring to fig. 2, the signal processing module 130 includes a variable gain amplifying unit 131, an analog-to-digital conversion unit 132 and a logic control unit 133, the variable gain amplifying unit 131, the analog-to-digital conversion unit 132 and the logic control unit 133 are sequentially electrically connected, the variable gain amplifying unit 131 is further electrically connected to the transimpedance amplifying module 120, and the logic control unit 133 is further electrically connected to the reference voltage output module 140.
The variable gain amplifying unit 131 is configured to amplify the voltage signal output by the transimpedance amplifying module 120; the analog-to-digital conversion unit 132 is configured to convert the amplified voltage signal into a digital signal; the logic control unit 133 is configured to adjust the magnitude of the reference voltage output by the reference voltage output module 140 according to the digital signal.
In this embodiment, the variable Gain amplifying Unit 131 may be implemented by a variable Gain Amplifier (PGA), the Analog-to-Digital converting Unit 132 may be implemented by a TDC (Time-to-Digital Converter) or an ADC (Analog-to-Digital Converter), and the logic control Unit 133 may be implemented by a MCU (micro controller Unit), a SoC (System on Chip), an FPGA (Field Programmable Gate Array).
That is to say, the optical-to-electrical conversion module 110 and the transimpedance amplification module 120 convert the optical signal into a voltage signal and output the voltage signal to the variable gain amplification unit 131, the voltage signal is amplified by the variable gain amplification unit 131 and then sent to the analog-to-digital conversion unit 132 to be converted from an analog signal to a digital signal, the converted digital signal is sent to the logic control unit 133 to be calculated and analyzed for the flight time, the optical signal intensity and the signal pulse width, and finally the magnitude of the reference voltage output by the reference voltage output module 140 is adjusted according to the signal pulse width or the optical signal intensity information, so that the purposes of adjusting the output dynamic range of the transimpedance amplification module 120 and suppressing the saturation of the output signal are achieved.
Optionally, referring to fig. 3, the transimpedance amplification module 120 includes a first operational amplifier 121 and a first resistor 122, a negative input terminal of the first operational amplifier 121 is electrically connected to the photoelectric conversion module 110, a positive input terminal of the first operational amplifier 121 is electrically connected to the reference voltage output module 140, an output terminal of the first operational amplifier 121 is electrically connected to the signal processing module 130, and the first resistor 122 is electrically connected between the negative input terminal and the output terminal of the first operational amplifier 121.
It can be seen that in the laser radar receiving circuit provided in the embodiment of the present invention, because the first operational amplifier has negative feedback, that is, the output voltage of the first operational amplifier is fed back to the negative input terminal through the feedback network (that is, the first resistor), the voltage of the positive input terminal and the voltage of the negative input terminal are substantially equal, and the reference voltage output module provides the reference voltage for the positive input terminal of the first operational amplifier, so that the signal processing module adjusts the magnitude of the reference voltage output by the reference voltage output module according to the voltage signal of the transimpedance amplification module, that is, adjusts the magnitude of the input voltage at the positive input terminal of the first operational amplifier, that is, adjusts the magnitude of the input voltage at the negative input terminal of the first operational amplifier, so as to adjust the magnitude of the voltage signal output by the transimpedance amplification module, thereby achieving the purposes of improving the output dynamic range of the transimpedance amplification module and suppressing saturation of the output signal.
In this embodiment, the signal processing module 130 may adjust the magnitude of the reference voltage output by the reference voltage output module 140 in the following two ways.
In a first embodiment, referring to fig. 4, the reference voltage output module 140 includes a plurality of switches 141 and a plurality of voltage dividing resistors 142 connected in series between a power source 144 and ground, nodes 143 corresponding to the number of the plurality of switches 141 are formed among the plurality of voltage dividing resistors 142, one end of each switch 141 is electrically connected to a corresponding one of the nodes 143, the other end of each switch 141 is electrically connected to a positive input terminal of the first operational amplifier 121, and a control terminal of each switch 141 is electrically connected to the signal processing module 130.
The signal processing module 130 is configured to control one of the switches 141 to be turned on according to the voltage signal, so as to adjust the magnitude of the reference voltage input to the positive input terminal of the first operational amplifier 121.
In this embodiment, each node 143 formed between the voltage-dividing resistors 142 can provide voltages with different magnitudes, and the logic control unit 133 of the signal processing module 130 can enable the nodes 143 corresponding to different switches 141 to input reference voltages with different magnitudes to the positive input end of the first operational amplifier 121 by turning on different switches 141, thereby achieving the purpose of adjusting the output dynamic range of the first operational amplifier 121.
In practical applications, the switch 141 may be a transistor, a MOS transistor, or the like, which is not limited in this embodiment.
Next, taking three voltage dividing resistors 142 as an example, as shown in fig. 5, the three voltage dividing resistors 142 are R1, R2, and R3, two nodes are formed between the resistors R1, R2, and R3, the nodes are P1 and P2, the switch corresponding to the node P1 is S1, and the reference voltage V is provided REF_HIGH (ii) a The switch corresponding to the node P2 is S2, and the provided reference voltage is V REF_LOW (ii) a Signal processingThe logic control unit 133 in the module 130 may select to turn on the switch S1 or the switch S2 according to the signal pulse width or the optical signal strength information, and when the switch S1 is turned on, the reference voltage V at the positive input terminal of the first operational amplifier 121 may be set REF Is adjusted to V REF_HIGH (ii) a When the switch S2 is turned on, the reference voltage V at the positive input terminal of the first operational amplifier 121 is set to be REF Is adjusted to V REF_LOW (ii) a Regulating the reference voltage V by controlling the switches S1, S2 REF The dynamic range of the output of the first operational amplifier 121 is also adjusted, as can be seen in fig. 6.
Referring to fig. 7, the reference voltage output module 140 includes a digital-to-analog conversion unit 145, and the digital-to-analog conversion unit 145 is electrically connected to both the signal processing module 130 and the positive input terminal of the first operational amplifier 121.
The signal processing module 130 is configured to output a digital control signal to the digital-to-analog conversion unit 145 according to the voltage signal; the digital-to-analog conversion unit 145 is used for converting the digital control signal into a corresponding reference voltage.
In this embodiment, the Digital-to-Analog Converter 145 may be implemented by a DAC (Digital-to-Analog Converter), as shown in fig. 8, the logic control unit 133 of the signal processing module 130 may input Digital control signals with different sizes to the DAC according to the signal pulse width or the optical signal intensity information, and obtain Analog signals with different sizes through conversion by the DAC, so as to input reference voltages with different sizes to the positive input terminal of the first operational amplifier 121, and further adjust the output dynamic range of the first operational amplifier 121, which may be specifically referred to fig. 9.
Optionally, in order to further improve the blind area suppression effect of the lidar receiving circuit 100, referring to fig. 10, the lidar receiving circuit 100 according to the embodiment of the present invention further includes a filtering module 150, an input end of the filtering module 150 is electrically connected to the transimpedance amplification module 120, and an output end of the filtering module 150 is electrically connected to the signal processing module 130.
The filtering module 150 is configured to perform filtering processing on the voltage signal output by the transimpedance amplification module 120, and output the filtered voltage signal to the signal processing module 130.
In this embodiment, the voltage signal output by the transimpedance amplification module 120 is filtered by the filtering module 150, so that the interference of a weak signal by other noise can be effectively avoided, and the signal-to-noise ratio and the resolution of the whole hardware system can be enhanced.
Therefore, the laser radar receiving circuit provided by the embodiment of the invention effectively inhibits the output saturation of the circuit under the strong light signal by greatly improving the output dynamic range on one hand, and effectively avoids the interference of the weak signal by other noises on the other hand by the filtering module, thereby realizing a better blind area inhibition function.
Optionally, referring to fig. 11, the filtering module 150 includes a second resistor 151, a third resistor 152, a fourth resistor 153, a fifth resistor 154, a first capacitor 155, a second capacitor 156, and a second operational amplifier 157; the second resistor 151 and the third resistor 152 are connected in series between the transimpedance amplification module 120 and the negative input terminal of the second operational amplifier 157; the fourth resistor 153 is electrically connected between the positive input end and the output end of the second operational amplifier 157, one end of the fifth resistor 154 is electrically connected to the positive input end of the second operational amplifier 157, and the other end of the fifth resistor 154 is grounded; one end of the first capacitor 155 is electrically connected between the second resistor 151 and the third resistor 152, and the other end of the first capacitor 155 is electrically connected to the output end of the second operational amplifier 157; one end of the second capacitor 156 is electrically connected between the third resistor 152 and the negative input terminal of the second operational amplifier 157, and the other end of the second capacitor 156 is grounded.
In the present embodiment, the filter module 150 shown in fig. 11 is a wideband filter circuit, and the bode diagram (fig. 12) of the circuit shows a typical low-pass filter characteristic. At the central frequency f of the laser pulse signal 0 (ω 0 And/2 pi) is close to (generally 150MHz to 250MHz), the gain of the circuit reaches the maximum value, so that the weak photoelectric signal can be effectively prevented from being interfered by other noises, and the signal-to-noise ratio and the resolution of the whole hardware system are enhanced.
The resistance value of the second resistor 151 is represented as R 1 The resistance of the third resistor 152 is represented as R 2 The resistance value of the fourth resistor 153 is expressed asR f The resistance of the fifth resistor 154 is denoted as R g The capacitance value of the first capacitor 155 is denoted as C 1 The capacitance value of the second capacitor 156 is denoted as C 2 Then R is 1 、R 2 、Rf、Rg、C 1 、C 2 The value of (b) is determined by:
a typical transfer function of the filtering module 150 can be expressed as:
wherein s is Laplace transform parameter, K, Q p And ω p Is a key characteristic parameter, K represents the DC (direct current) gain, Q p Representing a quality factor, ω p Represents the cut-off frequency;
assuming that the noise gain K is set to 0dB and the signal gain | H(s) & gtis zero according to the system requirements MAX Is 6dB, then Q p Can be calculated by equation (3); center frequency f of laser pulse signal 0 200MHz, then ω p Can be calculated by equation (4); the transmission characteristics of the filtering module 150 are now fully determined;then R can be converted according to the formulas (2), (5) and (6) 1 、R 2 、R f 、R g 、C 1 、C 2 And (4) calculating.
In the following, a laser radar receiving circuit provided by an embodiment of the present invention and a conventional laser radar receiving circuit are described in a specific scenario.
Fig. 13 is a schematic diagram of ranging when the lidar is in a high reflectivity obstacle condition. When an obstacle A with high reflectivity exists in front of a laser radar (Lidar), part of energy of emitted light B is converted into reflected light C, and the reflected light C is directly received and detected by the laser radar; and the other part of the light is converted into transmitted light D, the transmitted light D hits an object E to be detected and is reflected, and the reflected light F forms a light signal G after passing through the obstacle A and is received and detected by the laser radar. The intensity of the reflected light signal C of the high-reflectivity object in this case may be much higher than the intensity of the reflected light signal G of the object to be measured.
Fig. 14 and fig. 15 are schematic diagrams of echo signals of a conventional laser radar receiving circuit without a blind spot suppression function and a laser radar receiving circuit with a blind spot suppression function according to an embodiment of the present invention when facing a high-reflectivity object. As shown in fig. 14 and 15, the pulses H1 and H2 are laser emission signal waveforms, the pulses M1 and M2 are strong light signals returned from the object a with a high reflectivity at a short distance, and the pulses N1 and N2 are weak light signals returned from the object E to be measured.
In order to detect the weak optical signal G, the gain of the conventional laser radar receiving circuit is usually set very high. If the strong optical signal C is directly received, the receiving circuit may be saturated due to too strong photocurrent, so that the pulse signal may be widened. And the stronger the optical signal is, the wider the received pulse signal is, and in some cases, the pulse width will rise to the microsecond level, so that the circuit cannot obtain the pulse waveform N1 of the weak optical signal G, and thus cannot obtain the time-of-flight parameter t stop And calculates the distance. The lidar receiving circuit 100 in the embodiment of the invention has a blind area suppression function, so that the output saturation of the circuit under a strong light signal is effectively suppressed by greatly improving the output dynamic range on one hand, and on the other hand, the output saturation of the circuit under the strong light signal is effectively suppressed byThe filtering module 150 effectively prevents the weak signal from being interfered by other noises, thereby enhancing the signal-to-noise ratio and resolution of the whole hardware system; therefore, the occurrence of signal saturation broadening can be effectively inhibited, the reflection echo M2 of the strong light signal presents an unsaturated form, and meanwhile, the interference of the signal is further weakened by the filtering module 150, so that the circuit can more clearly distinguish the weak light signal N2 returned by the object E to be detected from the time-of-flight parameter t stop,s 。
Fig. 16 is a schematic flow chart of a signal processing method according to an embodiment of the present invention. The signal processing method can be applied to the laser radar receiving circuit 100 in the foregoing embodiment. It should be noted that the basic principle and the generated technical effect of the signal processing method provided by the embodiment are the same as those of the embodiment, and for the sake of brief description, no part of the embodiment is mentioned, and corresponding contents in the embodiment can be referred to. The signal processing amplification may comprise the steps of:
in step S10, the photoelectric conversion module converts the received optical signal into a current signal.
In step S20, the transimpedance amplification module converts the current signal into a voltage signal.
And step S30, the signal processing module adjusts the reference voltage output by the reference voltage output module according to the voltage signal, and then adjusts the voltage signal output by the transimpedance amplification module.
Therefore, according to the signal processing method provided by the embodiment of the invention, the received optical signal is converted into the current signal through the photoelectric conversion module, the current signal is converted into the voltage signal through the transimpedance amplification module, the reference voltage of the transimpedance amplification module is adjusted in real time by the signal processing module according to the voltage signal, the magnitude of the voltage signal output by the transimpedance amplifier can be changed along with the change of the reference voltage, the adjustment of the output dynamic range of the transimpedance amplification module is realized through the adjustment of the reference voltage of the transimpedance amplification module, the output saturation of the laser radar receiving circuit under the strong optical signal is effectively inhibited, the problem of point cloud abnormity of the laser radar is avoided, and the ranging blind area is reduced.
The embodiment of the invention also provides a laser radar simulation front end, which comprises the laser radar receiving circuit in the embodiment.
The embodiment of the invention also provides a laser radar which comprises the laser radar simulation front end in the embodiment.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A laser radar receiving circuit is characterized by comprising a photoelectric conversion module, a transimpedance amplification module, a signal processing module and a reference voltage output module, wherein the transimpedance amplification module is electrically connected with the photoelectric conversion module and the signal processing module;
the photoelectric conversion module is used for converting the received optical signal into a current signal;
the transimpedance amplification module is used for converting the current signal into a voltage signal;
the signal processing module is used for adjusting the reference voltage output by the reference voltage output module according to the voltage signal, and further adjusting the voltage signal output by the transimpedance amplification module.
2. The lidar receiving circuit of claim 1, wherein the transimpedance amplification module comprises a first operational amplifier and a first resistor, a negative input terminal of the first operational amplifier is electrically connected to the photoelectric conversion module, a positive input terminal of the first operational amplifier is electrically connected to the reference voltage output module, an output terminal of the first operational amplifier is electrically connected to the signal processing module, and the first resistor is electrically connected between the negative input terminal and the output terminal of the first operational amplifier.
3. The lidar receiving circuit according to claim 2, wherein the reference voltage output module comprises a plurality of switches and a plurality of voltage dividing resistors connected in series between a power supply and ground, wherein nodes corresponding to the number of the plurality of switches are formed among the plurality of voltage dividing resistors, one end of each of the switches is electrically connected to a corresponding one of the nodes, the other end of each of the switches is electrically connected to the positive input terminal of the first operational amplifier, and the control terminal of each of the switches is electrically connected to the signal processing module;
the signal processing module is used for controlling one of the switches to be conducted according to the voltage signal, so that the magnitude of the reference voltage input to the positive input end of the first operational amplifier is adjusted.
4. The lidar receiving circuit of claim 2, wherein the reference voltage output module comprises a digital-to-analog conversion unit, and the digital-to-analog conversion unit is electrically connected to the signal processing module and a positive input terminal of the first operational amplifier;
the signal processing module is used for outputting a digital control signal to the digital-to-analog conversion unit according to the voltage signal;
the digital-to-analog conversion unit is used for converting the digital control signal into a corresponding reference voltage.
5. The lidar receiving circuit according to any of claims 1 to 4, further comprising a filtering module, wherein an input terminal of the filtering module is electrically connected to the transimpedance amplification module, and an output terminal of the filtering module is electrically connected to the signal processing module;
the filtering module is used for filtering the voltage signal output by the transimpedance amplification module and outputting the voltage signal after filtering to the signal processing module.
6. The lidar receiving circuit of claim 5, wherein the filtering module comprises a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, and a second operational amplifier;
the second resistor and the third resistor are connected in series between the transimpedance amplification module and the negative input end of the second operational amplifier; the fourth resistor is electrically connected between the positive input end and the output end of the second operational amplifier, one end of the fifth resistor is electrically connected with the positive input end of the second operational amplifier, and the other end of the fifth resistor is grounded;
one end of the first capacitor is electrically connected between the second resistor and the third resistor, and the other end of the first capacitor is electrically connected with the output end of the second operational amplifier; one end of the second capacitor is electrically connected between the third resistor and the negative input end of the second operational amplifier, and the other end of the second capacitor is grounded.
7. The lidar receiving circuit according to any of claims 1 to 4, wherein the signal processing module comprises a variable gain amplifying unit, an analog-to-digital conversion unit and a logic control unit, the variable gain amplifying unit, the analog-to-digital conversion unit and the logic control unit are electrically connected in sequence, the variable gain amplifying unit is further electrically connected with the transimpedance amplifying module, and the logic control unit is further electrically connected with the reference voltage output module;
the variable gain amplification unit is used for amplifying the voltage signal output by the transimpedance amplification module;
the analog-to-digital conversion unit is used for converting the amplified voltage signal into a digital signal;
the logic control unit is used for adjusting the size of the reference voltage output by the reference voltage output module according to the digital signal.
8. A signal processing method applied to the lidar receiving circuit according to any of claims 1 to 7, the method comprising:
the photoelectric conversion module converts the received optical signal into a current signal;
the transimpedance amplification module converts the current signal into a voltage signal;
the signal processing module adjusts the magnitude of the reference voltage output by the reference voltage output module according to the voltage signal, and then adjusts the magnitude of the voltage signal output by the transimpedance amplification module.
9. A lidar analog front end comprising a lidar receiving circuit of any of claims 1-7.
10. A lidar comprising the lidar analog front end of claim 9.
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| CN117406200A (en) * | 2023-12-07 | 2024-01-16 | 苏州旭创科技有限公司 | Laser radar receiving end circuit and laser radar equipment |
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