Laser radar receiving circuit and receiving device

Abstract

The utility model discloses a laser radar receiving circuit and a receiving device, relates to the technical field of radars, and aims to solve the anti-interference problem of a laser radar under the condition of strong background light, comprising a photoelectric detector, the photoelectric detector is connected with an operational amplifier, a first end of the photoelectric detector is connected with a power supply, and a second end of the photoelectric detector is connected with a second end of the operational amplifier. The first end of the photoelectric detector is connected with the first input end of the operational amplifier, the second end of the photoelectric detector is connected with the first input end of the operational amplifier, the second input end of the operational amplifier inputs bias voltage, and a feedback module is connected between the first input end and the output end of the operational amplifier. The direct-current component of the background light can be eliminated, weakening of the dynamic range output by the TIA by the strong background light is reduced, and the performance difference of the laser radar in different background light environments is reduced.

Description

Technical Field

[0001] This utility model belongs to the field of radar technology, specifically relating to a laser radar receiving circuit and receiving device. Background Technology

[0002] With the further popularization of automation technology, mobile platforms are no longer limited to indoor applications such as robotic vacuum cleaners and AGVs. When mobile platforms are extended outdoors, they inevitably face the problem of strong background light and how to ensure consistent performance of LiDAR under different background light environments. Existing technologies address these issues by focusing on the optical system. On the one hand, they minimize the field of view of the receiving lens to reduce the amount of background light received from outside the target. On the other hand, adding a bandpass filter of the corresponding wavelength to the front end of the APD can significantly reduce the energy of external background light reaching the optoelectronic device. However, the bandwidth of the filter cannot be too narrow; the temperature drift of the LD must be considered. For example, the wavelength drift coefficient of a commonly used side-emitting EELLD is 0.3 nm / ℃. Considering that the operating temperature of LiDAR ranges from -40 to 85℃, the center wavelength variation of the LD is approximately 37.5 nm. Taking a 905nm LD as an example, at a room temperature of 25℃, the bandpass filter specification must be 905 + / - 20nm to meet the wavelength drift requirements across the entire temperature range. Alternatively, a vertical-cavity emission (VCSEL) lidar can be used, which has an exceptionally low temperature drift coefficient, reaching 0.07 nm / ℃. At room temperature (25℃), its bandpass filter specification is 905 + / - 5 nm, which also meets the temperature drift range requirements, further reducing the energy of background light reaching the photodetector. However, under strong outdoor light, when the intensity of the background light is much greater than the intensity of the signal light, the accuracy or ranging capability of the lidar will still be reduced.

[0003] For example, Chinese patent CN116430362A discloses a lidar receiving circuit and a lidar, including an auxiliary light source circuit, an echo signal processing circuit, and a control circuit. When the auxiliary light source circuit is turned on, the echo signal processing circuit processes the initial light signal and the auxiliary light signal to obtain the target echo signal, which is then sent to the control circuit. This allows the control circuit to acquire the target echo signal within a preset time range after the auxiliary light source circuit is turned off. By providing an auxiliary light source, and considering the low reflectivity of the target object, the auxiliary light signal output when the auxiliary light source circuit is turned on increases the intensity of the light signal received by the lidar, thereby amplifying the obtained echo signal, i.e., increasing the peak voltage of the echo signal, to acquire the target echo signal with a corresponding amplification factor. However, the lidar in Chinese patent CN116430362A is susceptible to interference from background light, exhibits inconsistent performance under different background light conditions, is unsuitable for outdoor environments with strong light, and has a complex circuit. Utility Model Content

[0004] To address the interference problem of lidar under strong background light conditions, this invention proposes a lidar receiving circuit and receiving device that can eliminate the DC component of background light and reduce the weakening of the dynamic range of the operational amplifier output by strong background light, thereby reducing the performance difference of lidar under different background light environments.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a laser radar receiving circuit, including a photodetector, the photodetector being connected to an operational amplifier, the first end of the photodetector being connected to a power supply, the second end of the photodetector being connected to the first input end of the operational amplifier, the second input end of the operational amplifier receiving a bias voltage, and a feedback module being connected between the first input end and the output end of the operational amplifier.

[0006] In this technical solution, a lidar receiving circuit includes a photodetector and an operational amplifier. The photodetector and operational amplifier are disposed on one side of a filter. The positive input terminal of the operational amplifier is connected to a bias voltage. A feedback module is connected between the inverting input terminal and the output terminal of the operational amplifier. The feedback module adopts a T-type feedback network, which can retain the advantages of DC coupling and reduce the weakening of the dynamic range of the operational amplifier output by strong background light, thereby reducing the performance difference of lidar under different background light environments.

[0007] Preferably, the negative terminal of the photodetector is connected to a power supply, the positive terminal of the photodetector is connected to the inverting input terminal of the operational amplifier, the positive input terminal of the operational amplifier receives a bias voltage, and the feedback module is connected between the inverting input terminal and the output terminal of the operational amplifier.

[0008] Preferably, the feedback module is a T-type feedback network, which includes several resistors and capacitors.

[0009] Preferably, the feedback module includes a first branch, the first branch including a capacitor C. F The capacitor C F One end is connected to the inverting input terminal of the operational amplifier, and the other end is connected to the output terminal of the operational amplifier.

[0010] Preferably, the feedback module includes a second branch, which is connected in parallel with the first branch. The second branch includes resistors R1 and R2, which are connected in series.

[0011] Preferably, the feedback module includes a third branch, which includes a resistor R3. One end of the resistor R3 is connected between the resistor R1 and the resistor R2, and the other end is connected to one end of the capacitor C1. The other end of the capacitor C1 is grounded, and the resistor R3 and the capacitor C1 are connected in series.

[0012] Preferably, the output current of the photodetector includes the background photocurrent I. DC and signal photocurrent I S The background photocurrent is DC, and the signal photocurrent is AC.

[0013] Preferably, the feedback module controls the signal photocurrent I. S The gain of the transimpedance is positively correlated with the frequency of the input signal; the higher the frequency of the input signal, the greater the feedback module's response to the signal photocurrent I. S The greater the transresistor gain, the better.

[0014] Preferably, the resistance values ​​of some resistors in the feedback module are less than 5kΩ; by using a T-type network, smaller resistors can be used to achieve the purpose of equivalent large impedance, which can reduce the resistive thermal noise caused by directly using large resistors and improve the signal-to-noise ratio.

[0015] The beneficial effects of this utility model are:

[0016] 1. The photodetector and operational amplifier adopt DC coupling, which retains the advantages of DC coupling to the greatest extent.

[0017] 2. By adopting a T-type network, different amplification factors for DC and AC are achieved, maintaining a large dynamic range under different background light conditions;

[0018] 3. By using a T-type network, a smaller resistor can be used to achieve the purpose of equivalent large impedance. This can reduce the resistive thermal noise caused by directly using a large resistor and improve the signal-to-noise ratio.

[0019] 4. Capable of receiving pulses with higher repetition frequencies. Attached Figure Description

[0020] Figure 1 This is a circuit diagram of a lidar receiver circuit that uses DC coupling.

[0021] Figure 2 This is a circuit diagram of a lidar receiver circuit that uses AC coupling.

[0022] Figure 3 This is a circuit diagram of a laser radar receiving circuit according to this utility model. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this utility model and are only used to explain this utility model. They do not limit the scope of protection of this utility model. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0024] In existing technologies, the commonly used photoelectric conversion device in lidar is the avalanche photodiode (APD). The most common method of coupling between the APD and the transimpedance amplifier (TIA) is DC coupling. Figure 1 .

[0025] The current generated by both background light and signal light is input to the output voltage of the transimpedance amplifier after conversion. Under strong outdoor background light conditions, this will directly reduce the dynamic range of the TIA output.

[0026] DC coupling is the simplest method, capable of converting all useful echo signal current into a voltage signal, with an output voltage signal of V. out =V ref -(I dc +I S )*R F , where V ref I is the voltage at the positive input terminal of the TIA op-amp. dc I represents the DC current component generated by the background light. S R is the current component generated by the signal light. f This is the gain of the transresistor.

[0027] It is easy to conclude that when the background light is enhanced, the dynamic range of the Vout output will increase with the DC component I. dc As the background light increases, the dynamic range of the TIA output decreases, thus background light enhancement weakens the dynamic range of the TIA output.

[0028] To eliminate the DC component of the background light, AC coupling can be used, refer to... Figure 2 .

[0029] A coupling capacitor Cin is provided between the positive terminal of the avalanche photodiode and the inverting input terminal of the transimpedance amplifier. Since the capacitor has the characteristic of blocking DC and passing AC, the DC component generated by the background light cannot be input to the TIA, thus ensuring the output dynamic range of the TIA.

[0030] However, at the same time, a load resistor R must be connected to ground at the anode of the APD. SOnly in this way can a stable DC bias circuit be established for the APD. Otherwise, it is an open circuit, the APD bias voltage has no reference point, and it is impossible to establish an accelerating electric field across the APD. Therefore, the APD cannot achieve the purpose of avalanche amplification.

[0031] The presence of this load resistor Rs establishes a path to ground for the signal photocurrent, while also shunting the signal photocurrent input to the TIA.

[0032] AC coupling can eliminate the influence of the DC component generated by the background light, but a resistor Rs must be added below the APD anode.

[0033] The purpose of this resistor is to provide a stable DC bias voltage for the APD. Without this resistor, the voltage applied to the APD has no reference point, which is equivalent to an open circuit. There is no voltage drop across the APD, and it cannot provide a sufficiently large electric field for the APD's avalanche operation, so the APD cannot work properly.

[0034] However, increasing this resistance will divert the useful signal photocurrent Is, leading to a decrease in the transresistance gain of the subsequent TIA, thereby reducing the system's receiving sensitivity.

[0035] It is understandable that DC coupling and AC coupling each have their own advantages and disadvantages.

[0036] DC-coupled circuits have higher gain, faster saturation recovery time, and faster multi-channel switching, but their dynamic range is smaller under strong background light.

[0037] AC coupling has good resistance to strong light and a large dynamic range. However, the effective signal is shunted, the equivalent impedance gain is reduced, the charging and discharging of the coupling capacitor takes time, the saturation recovery time is slow, and the establishment time between multiple channels is relatively long.

[0038] Example 1

[0039] This embodiment provides a lidar receiving circuit, including a photodetector, an operational amplifier, and a feedback module. (Refer to...) Figure 3 This can eliminate the DC component of the background light and reduce the weakening of the dynamic range of the operational amplifier output by strong background light.

[0040] like Figure 3 As shown, the photodetector is disposed on one side of the filter, and the filter is disposed on the first side of the photodetector.

[0041] In this embodiment, the photodetector can be an avalanche photodiode (APD). The photodetector can be, but is not limited to, an avalanche photodiode (APD), a SPAD (single-photon avalanche photodiode), a SiPM (silicon photomultiplier tube), or a PD (photodiode).

[0042] The negative terminal of the photodetector is connected to the power supply, and the positive terminal of the photodetector is connected to the inverting input of the operational amplifier.

[0043] In this embodiment, the operational amplifier is a transimpedance amplifier (TIA), and a transimpedance amplifier of model MS8258D can be used.

[0044] The operational amplifier is biased at its positive input terminal, and a feedback module is connected between its inverting input terminal and its output terminal.

[0045] The feedback module is a T-type feedback network, which includes several resistors and capacitors.

[0046] The feedback module includes a first branch, which includes a capacitor C. F The capacitor C F One end is connected to the inverting input terminal of the operational amplifier, and the other end is connected to the output terminal of the operational amplifier.

[0047] The feedback module includes a second branch, which is connected in parallel with the first branch. The second branch includes resistors R1 and R2, which are connected in series.

[0048] The feedback module includes a third branch, which includes a resistor R3. One end of the resistor R3 is connected between the resistor R1 and the resistor R2, and the other end is connected to one end of the capacitor C1. The other end of the capacitor C1 is grounded, and the resistor R3 and the capacitor C1 are connected in series.

[0049] In this embodiment, the feedback network consists of a first branch, a second branch, and a third branch. Using a T-type network allows for a larger equivalent impedance with a smaller circuit value, thereby further reducing resistive thermal noise.

[0050] In this embodiment, the photodetector output current includes the background photocurrent I. DC and signal photocurrent I S The background photocurrent is DC, and the signal photocurrent is AC. Specifically, since the emitted light is an artificially designed pulsed laser, it has a certain pulse width condition; that is, the reflected signal light also has a certain pulse width condition. Therefore, the signal photocurrent I...S The background light is considered an AC signal, while the background light is unmodulated light; therefore, the background photocurrent I is considered an AC signal. DC It is considered a DC signal.

[0051] In this embodiment, the feedback module controls the signal photocurrent I. S The transimpedance gain is positively correlated with the input signal frequency. Here, the input signal frequency refers to the equivalent frequency corresponding to the pulse width of the reflected signal light, not the repetition frequency of the emitted signal. It's important to note that although the emitted light is a signal of a specific width, meaning its frequency is essentially fixed, the reflected signal light will be broadened to varying degrees due to differences in reflectivity. For example, the pulse width broadening is minimal for black objects, while for highly reflective objects, the strong reflected energy, APD saturation, and output signal tailing will broaden the signal light, resulting in a lower corresponding frequency.

[0052] In this embodiment, the resistance values ​​of some resistors are less than 5kΩ. Since the feedback module of the lidar receiving circuit in this embodiment adopts a T-type network, smaller resistors can be used to achieve the purpose of equivalent large impedance. This can reduce the resistive thermal noise caused by directly using large resistors and improve the signal-to-noise ratio.

[0053] The working principle of a lidar receiving circuit according to this embodiment will be described in detail below.

[0054] After the emitted laser reaches the target, it is reflected by the target and, together with the reflected background light, reaches the front-end filter. Light with wavelengths within the filter band can pass through the filter and reach the photodetector. At this time, the background light DC I DC and signal optical pulse current I S They are input together to the inverting input of the operational amplifier.

[0055] The operational amplifier's positive input terminal is input with V. ref Bias voltage.

[0056] For the DC portion, the background light is unmodulated, therefore the background photocurrent I... DC Treating it as a DC signal, the R3C1 branch, i.e. the third branch, is equivalent to an open circuit. Therefore, its equivalent transducer gain is R1+R2.

[0057] For useful signal optical pulse current signal I s Since the emitted light is an artificially designed pulsed laser, it has a certain pulse width. This means the reflected signal light also has a certain pulse width. The signal light pulse current signal I... s If it can be considered as an AC signal, then its equivalent gain is the transducer gain constructed by the T-type network: R1+R2+R1*R2 / (R3+1 / wc1).

[0058] The transducer gain is positively correlated with the input signal frequency; the lower the frequency, the smaller the equivalent transducer gain, and vice versa. Here, the input signal frequency refers to the equivalent frequency of the reflected light pulse. It's important to note that although the emitted light is a signal of a specific width, meaning its frequency is essentially fixed, the reflected light will be broadened to varying degrees due to differences in reflectivity. For example, the pulse width broadening is minimal for black objects, while for highly reflective objects, the strong reflected energy, APD saturation, and output signal tailing will broaden the light, resulting in a lower corresponding frequency.

[0059] C F As the loop compensation capacitor, the loop bandwidth of this circuit is determined by the equivalent transimpedance gain R and C. F It was decided jointly.

[0060] In this embodiment, R1 can be set to 1000Ω, R2 to 100Ω, R3 to 10Ω, and C1 to 1uF.

[0061] For a DC signal, the equivalent DC impedance is calculated based on the resistance and capacitance values ​​as R1 + R2 = 1100Ω.

[0062] For alternating signals, Z C =1 / wC1, Zc is connected in series with R3, and the equivalent AC impedance is R1+R2+R1*R2 / (R3+1 / wC1).

[0063] Where w = 2πf, and when f = 100MHz, the equivalent AC impedance = 1000 + 100 + 1000 * 100 / (10 + 1 / 2 * 3.14 * 100000000 * 0.000001) ≈ 11000Ω.

[0064] It is easy to see from the values ​​of the equivalent DC impedance and the equivalent AC impedance that the DC impedance and the AC impedance differ by about 10 times.

[0065] Therefore, under strong background light, the operational amplifier output signal V out =V ref -I DC *(R1+R2)-I S* (R1+R2+R1*R2 / (R3+1 / wc).

[0066] Substituting the values, we get V out =V ref -I DC *1100-I S *11000.

[0067] According to the above formula, it can be understood that the reduction in the dynamic range of the signal caused by the background light is only about 1 / 10 of the signal amplitude, which largely ensures the signal-to-noise ratio under strong background light.

[0068] In addition, since the thermal noise of a resistor is proportional to its resistance value, the larger the resistance, the greater the thermal noise it generates.

[0069] The formula for the one-sided noise power spectral density of a resistor is Vn² = 4kTR, where k = 1.38e⁻²³ is the Boltzmann constant and T is the absolute temperature.

[0070] As can be seen from the above formula, by using a T-type network, a larger equivalent impedance can be obtained with a smaller resistance value, thereby further reducing the resistive thermal noise by about 10 times.

[0071] In this embodiment, the photodetector and operational amplifier of a lidar receiving circuit adopt a DC coupling method, which retains the advantages of DC coupling to the greatest extent, namely, high gain, fast saturation recovery time, and fast multi-channel switching time.

[0072] The lidar receiving circuit of this embodiment adopts a T-type network, which realizes different amplification factors for DC and AC, and can basically maintain a large dynamic range of the signal under strong background light conditions.

[0073] When encountering highly reflective objects or other radar beams, the strong light input causes the APD to be in an oversaturated state, and the output signal pulse will be broadened. When the signal light is broadened, the frequency of the corresponding signal light decreases, thereby reducing the amplification factor of the transimpedance amplifier (TIA), speeding up the recovery time of the TIA output, and preparing for the next measurement more quickly. Therefore, the lidar receiving circuit of this embodiment can handle receiving pulses with higher repetition frequencies.

[0074] Meanwhile, the lidar receiving circuit of this embodiment adopts a T-type network, which can use a smaller resistor to achieve the purpose of equivalent large impedance. This can reduce the resistive thermal noise caused by directly using a large resistor and improve the signal-to-noise ratio.

[0075] Example 2

[0076] This embodiment provides a lidar receiving circuit, including a photodetector, an operational amplifier, and a feedback module, which can eliminate the DC component of the background light and reduce the weakening of the dynamic range of the operational amplifier output by strong background light.

[0077] In this embodiment, the photodetector can be an avalanche photodiode (APD). The photodetector can be, but is not limited to, an avalanche photodiode (APD), a SPAD (single-photon avalanche photodiode), a SiPM (silicon photomultiplier tube), or a PD (photodiode).

[0078] The negative terminal of the photodetector is connected to the power supply, and the positive terminal of the photodetector is connected to the inverting input of the operational amplifier.

[0079] In this embodiment, the operational amplifier is a transimpedance amplifier (TIA), and a transimpedance amplifier of model MS8258D can be used.

[0080] The operational amplifier is biased at its positive input terminal, and a feedback module is connected between its inverting input terminal and its output terminal.

[0081] The feedback module is a T-type feedback network, which includes several resistors and capacitors.

[0082] The feedback module includes a first branch, which includes a capacitor C. F The capacitor C F One end is connected to the inverting input terminal of the operational amplifier, and the other end is connected to the output terminal of the operational amplifier.

[0083] The feedback module includes a second branch, which is connected in parallel with the first branch. The second branch includes resistors R1 and R2, which are connected in series.

[0084] The feedback module includes a third branch, which includes a resistor R3. One end of the resistor R3 is connected between the resistor R1 and the resistor R2, and the other end is connected to one end of the capacitor C1. The other end of the capacitor C1 is grounded, and the resistor R3 and the capacitor C1 are connected in series.

[0085] In this embodiment, the feedback network consists of a first branch, a second branch, and a third branch. Using a T-type network allows for a larger equivalent impedance with a smaller circuit value, thereby further reducing resistive thermal noise.

[0086] In this embodiment, the photodetector output current includes the background photocurrent I. DC and signal photocurrent I S The background photocurrent is DC, and the signal photocurrent is AC. Specifically, since the emitted light is an artificially designed pulsed laser, it has a certain pulse width condition; that is, the reflected signal light also has a certain pulse width condition. Therefore, the signal photocurrent I...S The background light is considered an AC signal, while the background light is unmodulated light; therefore, the background photocurrent I is considered an AC signal. DC It is considered a DC signal.

[0087] In this embodiment, the feedback module controls the signal photocurrent I. S The transimpedance gain is positively correlated with the input signal frequency. Here, the input signal frequency refers to the equivalent frequency of the reflected light pulse. It's important to note that although the emitted light is a signal of a specific width, meaning its frequency is essentially fixed, the reflected light will be broadened to varying degrees due to differences in reflectivity. For example, the pulse width broadening is minimal for black objects, while for highly reflective objects, the strong reflected energy, APD saturation, and output signal tailing will broaden the light, resulting in a lower corresponding frequency.

[0088] In this embodiment, the resistance values ​​of some resistors are less than 5kΩ. Since the feedback module of the lidar receiving circuit in this embodiment adopts a T-type network, smaller resistors can be used to achieve the purpose of equivalent large impedance. This can reduce the resistive thermal noise caused by directly using large resistors and improve the signal-to-noise ratio.

[0089] The working principle of a lidar receiving circuit according to this embodiment will be described in detail below.

[0090] After the emitted laser reaches the target, it is reflected by the target and, together with the reflected background light, reaches the front-end filter. Light with wavelengths within the filter band can pass through the filter and reach the photodetector. At this time, the background light DC I DC and signal optical pulse current I S They are input together to the inverting input of the operational amplifier.

[0091] The operational amplifier's positive input terminal is input with V. ref Bias voltage.

[0092] For the DC portion, the background light is unmodulated, therefore the background photocurrent I... DC Treating it as a DC signal, the R3C1 branch, i.e. the third branch, is equivalent to an open circuit. Therefore, its equivalent transducer gain is R1+R2.

[0093] For useful signal optical pulse current signal I s Since the emitted light is an artificially designed pulsed laser, it has a certain pulse width. This means the reflected signal light also has a certain pulse width. The signal light pulse current signal I... s If it can be considered as an AC signal, then its equivalent gain is the transducer gain constructed by the T-type network: R1+R2+R1*R2 / (R3+1 / wc1).

[0094] The transducer gain is positively correlated with the input signal frequency; the lower the frequency, the smaller the equivalent transducer gain, and vice versa. Here, the input signal frequency refers to the equivalent frequency of the reflected light pulse. It's important to note that although the emitted light is a signal of a specific width, meaning its frequency is essentially fixed, the reflected light will be broadened to varying degrees due to differences in reflectivity. For example, the pulse width broadening is minimal for black objects, while for highly reflective objects, the strong reflected energy, APD saturation, and output signal tailing will broaden the light, resulting in a lower corresponding frequency.

[0095] C F As the loop compensation capacitor, the loop bandwidth of this circuit is determined by the equivalent transimpedance gain R and C. F It was decided jointly.

[0096] In this embodiment, R1 can be set to 2000Ω, R2 to 200Ω, R3 to 10Ω, and C1 to 1uF.

[0097] For DC signals, the equivalent DC impedance is calculated based on the resistance and capacitance values ​​as R1 + R2 = 2200Ω.

[0098] For alternating signals, Z C =1 / wC1, Zc is connected in series with R3, and the equivalent AC impedance is R1+R2+R1*R2 / (R3+1 / wC1).

[0099] Where w = 2Πf, and when f = 100MHz, the equivalent AC impedance = 2000 + 200 + 2000 * 200 / (10 + 1 / 2 * 3.14 * 100000000 * 0.000001) ≈ 41800Ω.

[0100] It is easy to see from the values ​​of the equivalent DC impedance and the equivalent AC impedance that the DC impedance and the AC impedance differ by about 20 times.

[0101] Therefore, under strong background light, the operational amplifier output signal V out =V ref -I DC *(R1+R2)-I S* (R1+R2+R1*R2 / (R3+1 / wc).

[0102] Substituting the values, we get V out =V ref -I dc *2200-I S *41800.

[0103] According to the above formula, it can be understood that the reduction in signal dynamic range caused by background light is only about 1 / 20 of the signal amplitude, which largely ensures the signal-to-noise ratio under strong background light.

[0104] In addition, since the thermal noise of a resistor is proportional to its resistance value, the larger the resistance, the greater the thermal noise it generates.

[0105] The formula for the one-sided noise power spectral density of a resistor is Vn² = 4kTR, where k = 1.38e⁻²³ is the Boltzmann constant and T is the absolute temperature.

[0106] As can be seen from the above formula, by using a T-type network, a larger equivalent impedance can be obtained with a smaller resistance value, thereby further reducing the resistive thermal noise by about 20 times.

[0107] In this embodiment, the photodetector and operational amplifier of a lidar receiving circuit adopt a DC coupling method, which retains the advantages of DC coupling to the greatest extent, namely, high gain, fast saturation recovery time, and fast multi-channel switching time.

[0108] The lidar receiving circuit of this embodiment adopts a T-type network, which realizes different amplification factors for DC and AC, and can basically maintain a large dynamic range of the signal under strong background light conditions.

[0109] When encountering highly reflective objects or other radar beams, the strong light input causes the photodetector to be in an oversaturated state, and the output pulse will be broadened. When the signal light is broadened, the frequency of the corresponding signal light decreases, thereby reducing the amplification factor of the operational amplifier, speeding up the recovery time of the operational amplifier output, and preparing for the next measurement more quickly. Therefore, the lidar receiving circuit of this embodiment can handle receiving pulses with higher repetition frequencies.

[0110] Meanwhile, the lidar receiving circuit of this embodiment adopts a T-type network, which can use a smaller resistor to achieve the purpose of equivalent large impedance. This can reduce the resistive thermal noise caused by directly using a large resistor and improve the signal-to-noise ratio.

[0111] The present invention provides a detailed description of a lidar receiving circuit. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely illustrative and are intended to aid in understanding the method and core concepts of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A lidar receiving circuit, characterized in that, The device includes a photodetector connected to an operational amplifier. The first end of the photodetector is connected to a power supply, and the second end of the photodetector is connected to the first input end of the operational amplifier. A bias voltage is input to the second input end of the operational amplifier, and a feedback module is connected between the first input end and the output end of the operational amplifier.

2. The lidar receiving circuit according to claim 1, characterized in that, The negative terminal of the photodetector is connected to a power supply, the positive terminal of the photodetector is connected to the inverting input terminal of the operational amplifier, the positive input terminal of the operational amplifier receives a bias voltage, and the feedback module is connected between the inverting input terminal and the output terminal of the operational amplifier.

3. The lidar receiving circuit according to claim 1, characterized in that, The feedback module is a T-type feedback network, which includes several resistors and capacitors.

4. A lidar receiving circuit according to claim 1, characterized in that, The feedback module includes a first branch, which includes a capacitor C. F The capacitor C F One end is connected to the inverting input terminal of the operational amplifier, and the other end is connected to the output terminal of the operational amplifier.

5. A lidar receiving circuit according to claim 4, characterized in that, The feedback module includes a second branch, which is connected in parallel with the first branch. The second branch includes resistors R1 and R2, which are connected in series.

6. A lidar receiving circuit according to claim 5, characterized in that, The feedback module includes a third branch, which includes a resistor R3. One end of the resistor R3 is connected between the resistor R1 and the resistor R2, and the other end is connected to one end of the capacitor C1. The other end of the capacitor C1 is grounded, and the resistor R3 and the capacitor C1 are connected in series.

7. A lidar receiving circuit according to any one of claims 1-6, characterized in that, The output current of the photodetector includes the background photocurrent I. DC and signal photocurrent I S The background photocurrent is DC, and the signal photocurrent is AC.

8. A lidar receiving circuit according to claim 7, characterized in that, The feedback module controls the signal photocurrent I. S The gain of the transducer is positively correlated with the frequency of the input signal.

9. A lidar receiving circuit according to claim 3, characterized in that, The resistance values ​​of the aforementioned resistors are less than 5kΩ.

10. A lidar receiver, characterized in that, The invention includes a lidar receiving circuit and a filter as described in any one of claims 1-9, wherein the lidar receiving circuit includes a photodetector and the filter is disposed on a first side of the photodetector.

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