A multi-channel analog front-end circuit for laser radar

Abstract

The present invention discloses a laser radar multi-channel analog front-end circuit, comprising multiple gain amplification modules, each of which comprises two parallel amplification units, each of which comprises an input DC blocking capacitor, a bypass filter capacitor, a transimpedance amplifier, a fixed gain amplifier and a differential-to-single-ended amplifier, one end of the input DC blocking capacitor being connected to the output end of the detector, the other end of the input DC blocking capacitor being respectively connected to the bypass filter capacitor and the input end of the transimpedance amplifier, the transimpedance amplifier amplifies the signal and converts the single-ended input signal into a differential output signal, which is respectively output to the two input ends of the fixed gain amplifier, the two output ends of the fixed gain amplifier being respectively connected to the two input ends of the differential-to-single-ended amplifier, and the output end of the differential-to-single-ended amplifier serving as the output port of the amplification unit; the present invention has the advantage of improving the accuracy of the detection result of the laser radar.

Description

Technical Field

[0001] The present invention relates to the field of laser radar system design, and more specifically to a laser radar multi-channel analog front-end circuit. Background Art

[0002] LiDAR (Light Detection and Ranging) is an environmental perception system based on laser ranging technology, commonly known as LiDAR. Due to the advantages of lasers such as strong monochromaticity, good directionality, and strong coherence, LiDAR, developed based on laser measurement technology, is of great significance in non-contact distance measurement scenarios and is widely used in fields such as topographic mapping, weather monitoring, battlefield detection, and aerospace. In the military, LiDAR is a key component for intelligent weapons to achieve precision strikes, capable of performing tasks such as enemy target detection and imaging, helicopter obstacle avoidance, underwater detection, and space target surveillance. In recent years, with the rapid development of smart city construction, technologies such as unmanned delivery vehicles, self-driving cars, and robots have rapidly developed. The key to these technologies is the precise detection of targets and the real-time acquisition of target profile, distance, and orientation information, thereby perceiving the surrounding environment. LiDAR actively perceives and captures the surrounding environment, producing high-definition, real-time 3D images. It also offers unique advantages such as high-precision and high-resolution ranging and strong anti-interference capabilities. It has important applications in autonomous driving, drones, environmental monitoring, and wearable electronics. LiDAR has shown great potential in both industrial and civilian fields and has become a research hotspot. To meet the increasingly complex application demands of various fields, the current mainstream development trend of LiDAR is toward component integration, multi-line arrays of lasers and detectors, and multi-channel and chip-based signal processing circuits. In particular, research on signal processing circuits, as a key component of LiDAR, will not only improve LiDAR's overall performance but also help reduce its application costs.

[0003] In actual applications, when LiDAR detects close-range targets, the signal echo amplitude is large (above 500mV). At this time, the back-end analog signal processing circuit only needs a smaller amplification factor, otherwise the signal will easily saturate. However, when detecting long-range targets, the signal echo amplitude is small (below 10mV). At this time, the back-end analog signal processing circuit needs to maintain a large amplification state. Otherwise, due to insufficient link gain, the weak signal cannot be amplified to more than 2 times the noise floor level, and the signal will be overwhelmed by the inherent noise of the system. Therefore, when designing, it is necessary to consider whether to maintain accurate response to strong and weak echoes of targets at both long and short distances. Therefore, the corresponding back-end processing circuit needs to maintain a high dynamic range.

[0004] Chinese Patent Publication No. CN112711011A discloses a laser radar system, an optical signal receiving and processing device, and an optical signal receiving and processing method. The laser radar system includes an optical signal receiving and processing unit, which includes an optical receiver, a transimpedance amplifier, a first-level signal amplifier, a second-level adjustable gain amplifier, and an adjustable threshold comparator connected in sequence. The main control processing unit can adjust the power supply voltage of the optical receiver, the amplification gain of the second-level adjustable gain amplifier, and the threshold voltage of the adjustable threshold comparator according to the output result of the second-level adjustable gain amplifier. The gain adjustable range of the second-level adjustable gain amplifier is 10dB to 30dB, which has a high dynamic range. However, it does not process high-frequency noise, common-mode noise, DC noise, etc. in the circuit, so that the echo signal has certain interference, affecting the accuracy of the detection result. Although the gain is adjustable, it cannot be accurately adjusted in different gears, resulting in the laser radar being unable to accurately switch the gain gear when detecting close-range targets or detecting long-range targets, and thus unable to respond accurately. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to improve the accuracy of the detection results of the laser radar.

[0006] The present invention solves the above-mentioned technical problems through the following technical means: a laser radar multi-channel analog front-end circuit, including multiple gain amplification modules, each of the gain amplification modules includes two parallel amplification units, each amplification unit includes an input DC blocking capacitor, a bypass filter capacitor, a transimpedance amplifier, a fixed gain amplifier and a differential-to-single-ended amplifier, one end of the input DC blocking capacitor is connected to the output end of the detector, and the other end of the input DC blocking capacitor is respectively connected to the bypass filter capacitor and the input end of the transimpedance amplifier, the transimpedance amplifier amplifies the signal and converts the single-ended input signal into a differential output signal and outputs it to the two input ends of the fixed gain amplifier, the two output ends of the fixed gain amplifier are respectively connected to the two input ends of the differential-to-single-ended amplifier, the differential-to-single-ended amplifier subtracts the differential signal and outputs it, and the output end of the differential-to-single-ended amplifier serves as the output port of the amplification unit.

[0007] Beneficial effect: The two ends of the input DC blocking capacitor of the present invention are respectively connected to the detector and the transimpedance amplifier, isolating the DC operating level of the transimpedance amplifier from the detector, isolating the signal interference at the detector end, the bypass filter capacitor filters the high-frequency noise, and the differential-to-single-ended amplifier performs differential signal subtraction, further eliminating common-mode noise and DC noise and improving the dynamic range of the signal link. The entire circuit eliminates interference to the maximum extent and improves the accuracy of the detection results of the lidar.

[0008] Furthermore, each amplification unit further includes a coupling capacitor C5 and a coupling capacitor C6, and the two output terminals of the transimpedance amplifier are connected to the two input terminals of the fixed gain amplifier through the coupling capacitor C5 and the coupling capacitor C6 respectively.

[0009] Furthermore, each amplifying unit further includes a coupling capacitor C9 and a coupling capacitor C10, and the two output terminals of the fixed gain amplifier are connected to the two input terminals of the differential-to-single-ended amplifier via the coupling capacitor C9 and the coupling capacitor C10 respectively.

[0010] Furthermore, each amplifying unit further includes a DC blocking capacitor C13, the output end of the differential-to-single-ended amplifier is connected to one end of the DC blocking capacitor C13, and the other end of the DC blocking capacitor C13 serves as the output port of the amplifying unit.

[0011] Furthermore, the laser radar multi-channel analog front-end circuit also includes a multi-channel switch, and the output end of each amplification unit of each gain amplification module is respectively connected to an input channel of the multi-channel switch.

[0012] Furthermore, the working timing of the external timing control signal of each input channel is different from the working timing of other input channels, and the data transmitted from the multiple input channels are switched and output in turn.

[0013] Furthermore, the laser radar multi-channel analog front-end circuit also includes a variable gain amplifier, and the input end of the variable gain amplifier is connected to the output end of the multi-channel switch.

[0014] Furthermore, the variable gain amplifier includes a gain pin, and different gain levels are selected by configuring the high and low levels of the gain pin.

[0015] Furthermore, the laser radar multi-channel analog front-end circuit also includes a data acquisition card and a host computer, the signal acquisition end of the data acquisition card is connected to the output end of the variable gain amplifier, and the host computer is communicatively connected to the data acquisition card.

[0016] Furthermore, the detector includes a balanced unit detector, a balanced linear array detector or a balanced area array detector.

[0017] The advantages of the present invention are:

[0018] (1) The two ends of the input blocking capacitor of the present invention are respectively connected to the detector and the transimpedance amplifier, isolating the DC operating level of the transimpedance amplifier from the detector, isolating the signal interference at the detector end, bypassing the filter capacitor to filter the high-frequency noise, and performing differential signal subtraction on the differential-to-single-ended amplifier, thereby further eliminating common-mode noise and DC noise and improving the dynamic range of the signal link. The entire circuit eliminates interference to the greatest extent, thereby improving the accuracy of the detection results of the lidar.

[0019] (2) The differential-to-single-ended amplifier of the present invention is output to a multi-channel switch after passing through a DC blocking capacitor, and the amplified and filtered data transmitted from the previous multiple channels are switched and output in turn through external timing control.

[0020] (3) The variable gain amplifier of the present invention further improves the dynamic range of the signal transmitted previously, and selects different gain gears by configuring the high and low levels of the gain pin, and can be precisely adjusted in different gears, so that the laser radar can accurately switch the gain gear when detecting close-range target objects or long-range targets, thereby accurately responding.

[0021] (4) The present invention adopts a multi-stage structure amplifier circuit to improve the dynamic range of the analog signal amplification link, thereby ensuring accurate response to strong and weak echoes of targets at long and short distances.

[0022] (5) The overall link architecture of the present invention is simple, and each amplifier level has a wide range of commercial integrated circuit chips to choose from, which enhances its configurability. In actual use, it also has the advantages of low cost, good stability, and high gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a multi-channel analog front-end circuit for a laser radar disclosed in an embodiment of the present invention;

[0024] Figure 2 This is a channel switching timing diagram of a multi-channel switch in a multi-channel analog front-end circuit of a lidar disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] like Figure 1As shown, a multi-channel analog front-end circuit for a laser radar can be applied to current mainstream detector architectures such as balanced unit detectors, balanced linear detectors, and balanced area array detectors, and includes multiple gain amplifier modules 1, a multi-channel switch MUX, and a variable gain amplifier VGA.

[0027] Each of the gain amplification modules 1 includes two parallel amplification units, each of which includes an input blocking capacitor C1, a bypass filter capacitor C2, a transimpedance amplifier TIA, a fixed gain amplifier AMP, and a differential-to-single-ended amplifier DRA. One end of the input blocking capacitor C1 is connected to the output end of the detector 2, and the other end of the input blocking capacitor C1 is connected to the bypass filter capacitor C2 and the input end of the transimpedance amplifier TIA, respectively. The input blocking capacitor C1 can effectively filter out the high-frequency noise signal in the photocurrent converted by the detector 2 to avoid its subsequent impact on the echo signal. The bypass filter capacitor C2 serves to effectively isolate the impact of the common-mode level of the transimpedance amplifier TIA on the performance of the detector 2.

[0028] The transimpedance amplifier TIA is the first stage of signal amplification with a gain of 60dB. A transimpedance amplifier TIA model LMH32401 can be used. Because the linear detector 2 converts the received optical signal into an AC current signal, in order to facilitate the amplification of the AC signal, a transimpedance amplifier TIA is required to convert the AC current signal into an AC voltage signal. On the other hand, the function of the transimpedance amplifier TIA is also to convert the single-ended input signal into a differential output signal, with the aim of better eliminating the common-mode noise in the signal and reducing its impact. Specifically, the two output terminals of the transimpedance amplifier TIA are connected to the two input terminals of the fixed-gain amplifier AMP through coupling capacitors C5 and C6, respectively. That is, the transimpedance amplifier TIA amplifies the signal and converts the single-ended input signal into a differential output signal and outputs it to the two input terminals of the fixed-gain amplifier AMP. The coupling capacitors C5 and C6 are respectively AC-coupled with the fixed-gain amplifier AMP to avoid the mutual influence of the common-mode levels between the transimpedance amplifier TIA and the fixed-gain amplifier AMP.

[0029] The function of the fixed-gain amplifier AMP is to amplify the signal by another 60dB, further improving the dynamic range of the signal processing chain. Its model can be AD8350. Considering a single-channel, one-to-one balanced signal chain, each gain amplifier module 1 will generate four signals after passing through the fixed-gain amplifier AMP. In the case of multiple channels, the number will be even greater, which is not conducive to further digital processing at the back end. Therefore, a differential-to-single-ended amplifier DRA is set with a gain of 0dB. The purpose is to subtract the differential signals output from the fixed-gain amplifier AMP, eliminating common-mode noise while reducing the number of output channels. Its model can be AD8130. Specifically, the two output ends of the fixed-gain amplifier AMP are connected to the two input ends of the differential-to-single-ended amplifier DRA via coupling capacitors C9 and C10, respectively. The differential-to-single-ended amplifier DRA performs differential signal subtraction and outputs it. The output end of the differential-to-single-ended amplifier DRA is connected to one end of a DC blocking capacitor C13, and the other end of the DC blocking capacitor C13 serves as the output port of the amplification unit. Figure 1 Channel 1 to Channel 8 represent eight gain amplifying modules 1 . This embodiment only uses eight gain amplifying modules 1 as an example. In actual applications, the number of gain amplifying modules 1 may be less than or greater than eight, and there is no limit on the number. Figure 1 The capacitors C3, C4, C7, C8, C11, C12, and C14 are all on another amplifier unit. This amplifier unit and the amplifier unit described above constitute a gain amplifier module 1 as a whole. The specific circuit structure of this amplifier unit is the same as the amplifier unit structure described above, and will not be repeated here.

[0030] After the signal comes out of the differential to single-ended amplifier DRA, since the multi-channel output cannot simultaneously perform signal digital acquisition, a multi-channel switch MUX is set up considering the adaptability of the back-end circuit. The output end of each amplification unit of each gain amplifier module 1 is respectively connected to an input channel of the multi-channel switch MUX. The input end of the variable gain amplifier VGA is connected to the output end of the multi-channel switch MUX. The working timing of the external timing control signal of each input channel is different from the working timing of other input channels, and the data transmitted from multiple input channels are switched and output in turn. As shown in the attached figure Figure 2 As shown in the figure, a simple diagram of the multi-channel switch MUX controlling the output of the multi-channel analog amplified signal is given. In the first clock cycle, the switch corresponding to the first channel is turned on, that is, the first channel will be output to the adjustable gain amplifier for further amplification. In the second clock cycle, the second channel will be switched on, and the signal of the second channel will be output to the adjustable gain amplifier, and so on, until all 8 channels are output.

[0031] The variable gain amplifier (VGA) is designed to further fine-tune the dynamic range of the LiDAR signal output. In this embodiment, it features eight levels of adjustable gain, with a gain amplification range of 5dB-40dB. This is achieved by configuring three gain pins to different levels. Different gain levels are selected by configuring the high and low levels of the gain pins. Table 1 below shows the pin configurations for the adjustable gain amplifier's gain pins G3, G2, and G1 under different gain conditions. This allows for different gains to be configured by adjusting the high and low levels of each pin. Specifically, G3, G2, and G1 are configured to 000 for a 5dB gain level, 001 for a 10dB gain level, 010 for a 15dB gain level, 011 for a 20dB gain level, 100 for a 25dB gain level, 101 for a 30dB gain level, 110 for a 35dB gain level, and 111 for a 40dB gain level.

[0032] Table 1 Pin configuration of gain pins G3, G2, and G1 under different gain conditions

[0033] G1 G2 G3 5dB 0 0 0 10dB 0 0 1 15dB 0 1 0 20dB 0 1 1 25dB 1 0 0 30dB 1 0 1 35dB 1 1 0 40dB 1 1 1

[0034] Continue reading Figure 1 As a further improvement, the multi-channel analog front-end circuit of the laser radar described herein further includes a data acquisition card (DAQ) and a host computer. The signal acquisition terminal of the data acquisition card (DAQ) is connected to the output terminal of the variable gain amplifier (VGA) via capacitor C15, and the host computer is in communication with the data acquisition card (DAQ). The output data of the variable gain amplifier (VGA) can be read and collected by the data acquisition card (DAQ), and the signal is then processed on the host computer to perform complex signal processing algorithms and other functions. The specific processing process is not an improvement of the present invention and is not described in detail here.

[0035] Through the above technical solution, the present invention can be applied to the current mainstream balanced unit detector 2, balanced linear array detector 2, balanced area array detector 2 and other detector 2 structure, and at the same time, the circuit input end is subjected to capacitive coupling and bypass capacitor filtering processing, which can effectively isolate the influence of the common mode level of the amplifier on the detector 2 on the one hand, and on the other hand, the bypass capacitor to ground can filter out the high-frequency noise signal after the conversion of the detector 2, avoiding its subsequent influence on the echo signal. At the same time, in order to improve the dynamic range of the signal processing link of the entire system, a multi-stage structure amplifier circuit is adopted to improve the dynamic range of the analog signal amplification link, thereby ensuring that the strong and weak echoes of targets at long and short distances can be accurately responded. At the same time, the overall link architecture is simple, and there are many optional models of commercial integrated circuit chips for amplifiers at each level, which enhances its configurability. In actual use, it also has the characteristics of low cost, simple architecture, good stability, and high gain.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A laser radar multi-channel analog front-end circuit, characterized in that: It includes multiple gain amplification modules, each of which includes two parallel amplification units. Each amplification unit includes an input DC blocking capacitor, a bypass filter capacitor, a transimpedance amplifier, a fixed gain amplifier and a differential-to-single-ended amplifier. One end of the input DC blocking capacitor is connected to the output end of the detector, and the other end of the input DC blocking capacitor is respectively connected to the bypass filter capacitor and the input end of the transimpedance amplifier. The transimpedance amplifier amplifies the signal and converts the single-ended input signal into a differential output signal, which is output to the two input ends of the fixed gain amplifier respectively. The two output ends of the fixed gain amplifier are respectively connected to the two input ends of the differential-to-single-ended amplifier. The differential-to-single-ended amplifier subtracts the differential signal and outputs it. The output end of the differential-to-single-ended amplifier serves as the output port of the amplification unit. Each amplification unit also includes a coupling capacitor C5 and a coupling capacitor C6. The two output ends of the transimpedance amplifier are respectively connected to the two input ends of the fixed gain amplifier through the coupling capacitor C5 and the coupling capacitor C6.

2. The laser radar multi-channel analog front-end circuit according to claim 1, characterized in that: Each amplification unit further includes a coupling capacitor C9 and a coupling capacitor C10. The two output terminals of the fixed gain amplifier are connected to the two input terminals of the differential-to-single-ended amplifier through the coupling capacitor C9 and the coupling capacitor C10 respectively.

3. The laser radar multi-channel analog front-end circuit according to claim 1, characterized in that: Each amplifying unit further includes a DC blocking capacitor C13 , the output end of the differential-to-single-ended amplifier is connected to one end of the DC blocking capacitor C13 , and the other end of the DC blocking capacitor C13 serves as the output port of the amplifying unit.

4. The laser radar multi-channel analog front-end circuit according to claim 1, characterized in that: It also includes a multi-channel switch, and the output end of each amplifying unit of each gain amplifying module is respectively connected to an input channel of the multi-channel switch.

5. The laser radar multi-channel analog front-end circuit according to claim 4, characterized in that: The working timing of the external timing control signal of each input channel is different from the working timing of other input channels, and the data transmitted from multiple input channels are switched and output in turn.

6. The laser radar multi-channel analog front-end circuit according to claim 4, characterized in that: The system also includes a variable gain amplifier, wherein the input end of the variable gain amplifier is connected to the output end of the multi-channel switch.

7. The laser radar multi-channel analog front-end circuit according to claim 6, characterized in that: The variable gain amplifier includes a gain pin, and different gain levels are selected by configuring the high and low levels of the gain pin.

8. The laser radar multi-channel analog front-end circuit according to claim 6, characterized in that: It also includes a data acquisition card and a host computer. The signal acquisition end of the data acquisition card is connected to the output end of the variable gain amplifier, and the host computer is in communication connection with the data acquisition card.

9. The laser radar multi-channel analog front-end circuit according to claim 1, characterized in that: The detector includes a balanced unit detector, a balanced linear array detector or a balanced area array detector.

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