Frequency modulated continuous wave lidar system

Abstract

This application provides a frequency-modulated continuous wave lidar system, comprising a programmable gain circuit and a laser. The programmable gain circuit includes a control module, a digital-to-analog converter module, and a programmable gain amplifier. The laser generates a detection beam. The control module generates a digital signal and controls the gain of the programmable gain amplifier according to the modulation bandwidth of the laser. The programmable gain amplifier, in response to the gain control of the control module, amplifies the analog signal to match the modulation bandwidth of the laser and uses the amplified analog signal as a modulation signal to modulate the detection beam. The modulated detection beam is emitted into the detection space. This application solves the problem of high resource requirements of the back-end receiving system in related technologies' frequency-modulated continuous wave lidar systems, thereby achieving optimal bandwidth modulation and ranging effects.

Description

Technical Field

[0001] This application relates to the field of lidar, and more specifically, to a frequency modulated continuous wave lidar system. Background Technology

[0002] In related technologies, frequency-modulated continuous wave lidar can be used for ranging. The ranging principle is as follows: a tunable laser emits a linearly modulated laser beam, which is reflected by the target and the reflected light beats with the local oscillator light on the photodetector of the receiving system. This converts the distance, speed and other information of the target into frequency, and the information of the target is obtained by solving the frequency information.

[0003] The measurement accuracy of frequency-modulated continuous wave (FM-CW) lidar depends on the modulation bandwidth of the laser, which is the difference between the maximum and minimum modulation frequencies. To improve measurement accuracy, the modulation bandwidth of the laser can be increased; however, a large modulation bandwidth leads to high resource requirements for the backend receiving system. Therefore, FM-CW lidar systems in related technologies suffer from the problem of high resource requirements for the backend receiving system. Summary of the Invention

[0004] This application provides a frequency-modulated continuous wave lidar system to at least solve the technical problem of high resource requirements for the back-end receiving system in frequency-modulated continuous wave lidar systems in related technologies.

[0005] According to one aspect of the embodiments of this application, a frequency-modulated continuous wave lidar system is provided, comprising: a programmable gain circuit and a laser, wherein the programmable gain circuit includes: a control module, a digital-to-analog converter module, and a programmable gain amplifier, wherein the laser is used to generate a detection beam; the control module is used to generate a digital signal and control the gain of the programmable gain amplifier according to the modulation bandwidth of the laser; the digital-to-analog converter module is connected to the control module and is used to convert the digital signal into an analog signal; the programmable gain amplifier is connected to the digital-to-analog converter module and is used to amplify the analog signal to match the modulation bandwidth of the laser in response to the gain control of the control module, and use the amplified analog signal as a modulation signal to modulate the detection beam, wherein the modulated detection beam is emitted into a detection space.

[0006] In one exemplary embodiment, the control module is further configured to increase the gain of the programmable gain amplifier when the modulation bandwidth of the laser is greater than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier; and to decrease the gain of the programmable gain amplifier when the modulation bandwidth of the laser is less than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier.

[0007] In one exemplary embodiment, the programmable gain amplifier is a programmable gain transimpedance amplifier, which is directly connected to the control module. The programmable gain transimpedance amplifier is configured with multiple resistance levels, and different resistance levels correspond to different gain resistors. The control module is further configured to configure the resistance levels of the programmable gain transimpedance amplifier according to the modulation bandwidth of the laser, so as to adjust the gain of the programmable gain transimpedance amplifier.

[0008] In one exemplary embodiment, the programmable gain amplifier includes: an operational amplifier, a set of gain resistors connected in parallel, and a multiplexer. The operational amplifier is configured in transimpedance amplification mode. One end of the set of gain resistors is connected to one input terminal of the operational amplifier. Each gain resistor in the set of gain resistors is connected to one input channel of the multiplexer. The output terminal of the multiplexer is connected to the output terminal of the operational amplifier. The control module, connected to the multiplexer, is used to select one input channel of the multiplexer according to the modulation bandwidth of the laser to achieve gain switching of the operational amplifier. The modulation bandwidth of the laser corresponds to the gain resistor on the selected input channel of the multiplexer.

[0009] In an exemplary embodiment, the resistance values ​​of the different gain resistors in the set of gain resistors are different from each other; the control module is further configured to determine the input channel connected to the gain resistor corresponding to the modulation bandwidth of the laser in the set of gain resistors as the selected input channel according to the preset modulation bandwidth corresponding to each gain resistor.

[0010] In one exemplary embodiment, the frequency-modulated continuous wave lidar system includes two switches connected in series, wherein one of the two switches is connected to the output of the operational amplifier, and the other switch is connected to the laser, so as to connect the multiplexer in Kelvin switching mode.

[0011] In one exemplary embodiment, the programmable gain amplifier includes: a differential proportional amplifier, two sets of gain resistors, and two multiplexers corresponding one-to-one with the two sets of gain resistors. The differential proportional amplifier is configured in differential proportional amplification mode. One end of the first set of gain resistors is connected in parallel to and connected to the first input terminal of the differential proportional amplifier. Each first gain resistor in the first set of gain resistors is connected to one input channel of the multiplexer corresponding to the first set of gain resistors. One end of the second set of gain resistors is connected in parallel to and connected to the second input terminal of the differential proportional amplifier. Each second gain resistor in the second set of gain resistors is connected to one input channel of the multiplexer corresponding to the second set of gain resistors. The output terminals of both multiplexers are connected to the output terminal of the differential proportional amplifier. The control module is connected to the two multiplexers and is used to select one input channel of the two multiplexers according to the modulation bandwidth of the laser to realize the gain switching of the differential proportional amplifier. The modulation bandwidth of the laser corresponds to the gain resistor on the selected input channel of the two multiplexers.

[0012] In an exemplary embodiment, the resistance values ​​of different gain resistors in the same group of the two sets of gain resistors are different from each other; the control module is further configured to determine the input channel connected to the gain resistor corresponding to the modulation bandwidth of the laser in the two sets of gain resistors as the selected input channel according to the preset modulation bandwidth corresponding to each first gain resistor and the modulation bandwidth corresponding to each second gain resistor.

[0013] In one exemplary embodiment, the digital-to-analog converter module is a current-mode DAC chip; the frequency-modulated continuous wave lidar system further includes: a load resistor, used as the output load of the current-mode DAC chip, to convert the analog signal from a current signal to a voltage signal, wherein the converted analog signal is output to the programmable gain amplifier.

[0014] In one exemplary embodiment, the control module is one of the following: a field-programmable gate array, a digital signal processor, or an application-specific integrated circuit (ASIC).

[0015] According to this application, a frequency-modulated continuous wave lidar system includes a programmable gain circuit and a laser. The programmable gain circuit includes a control module, a digital-to-analog converter module, and a programmable gain amplifier. The laser generates a probe beam. The control module generates a digital signal and controls the gain of the programmable gain amplifier according to the modulation bandwidth of the laser. The digital-to-analog converter module, connected to the control module, converts the digital signal into an analog signal. The programmable gain amplifier, connected to the digital-to-analog converter module, amplifies the analog signal to match the modulation bandwidth of the laser in response to the gain control of the control module, and uses the amplified analog signal as a modulation signal to modulate the probe beam. The modulated probe beam is emitted into the detection space. Because the gain of the programmable gain amplifier is controlled according to the modulation bandwidth of the laser, the dynamic range of the laser modulation bandwidth can be improved while ensuring the accuracy of the modulation signal, achieving optimal modulation bandwidth and ranging effect. This solves the problem of high resource requirements of the back-end receiving system in related technologies' frequency-modulated continuous wave lidar systems. Attached Figure Description

[0016] Figure 1 This is a structural block diagram of an optional frequency-modulated continuous wave lidar system according to an embodiment of this application;

[0017] Figure 2 This is a schematic diagram of an optional frequency-modulated continuous wave lidar system according to an embodiment of this application;

[0018] Figure 3 This is a schematic diagram of another optional frequency-modulated continuous wave lidar system according to an embodiment of this application;

[0019] Figure 4 This is a schematic diagram of another optional frequency-modulated continuous wave lidar system according to an embodiment of this application. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0021] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] According to one aspect of the embodiments of this application, a frequency-modulated continuous wave (FM-CW) lidar system is provided. The FM-CW lidar system in this embodiment can be applied to the field of lidar and to the process of FM-CW laser ranging. FM-CW laser ranging has advantages such as high measurement accuracy, long measurement distance, and high distance resolution, and is a commonly used technology in vehicle-mounted lidar. The ranging principle is as follows: a tunable laser emits a linearly modulated laser beam. After being reflected by the target, the reflected light and the local oscillator light beat at the photodetector of the receiving system, thereby converting the distance or velocity to be measured into a frequency. The distance or velocity of the target is obtained by calculating the frequency information. The difference between the maximum and minimum modulation frequencies of the laser is called the modulation bandwidth.

[0023] In frequency-modulated continuous wave (FM-CHW) lidar, the laser can be periodically and linearly modulated. Common modulation signals include triangular waves or sawtooth waves. The larger the modulation bandwidth, the larger the amplitude of the modulation signal. The ranging accuracy of FM-CHW lidar is an important performance indicator. The ranging accuracy depends on the modulation bandwidth of the laser, and a large modulation bandwidth places high demands on the resources of the back-end receiving system.

[0024] In this embodiment, to balance ranging accuracy and system resource requirements, and to optimize the use of receiving system resources while improving ranging accuracy, the laser modulation bandwidth can be adjusted according to the actual usage needs of the lidar. The laser modulation is achieved by changing the injection current. To this end, a programmable gain amplifier can be used to output the laser modulation signal. While ensuring the accuracy of the modulation signal, the dynamic range of the laser modulation bandwidth can be increased, thereby reducing system resource requirements while meeting the actual usage needs of the lidar, achieving optimal modulation bandwidth and ranging performance.

[0025] Figure 1 This is a structural block diagram of an optional frequency-modulated continuous wave lidar system according to an embodiment of this application, such as... Figure 1As shown, the frequency-modulated continuous wave lidar system 100 may include a programmable gain circuit 101 and a laser 102. Here, the programmable gain circuit 101 is an electronic device that sets the amplification factor through digital or analog signal programming. The programmable gain circuit 101 includes a control module 1011, a digital-to-analog converter module 1012, and a programmable gain amplifier 1013. The gain of the programmable gain amplifier 1013 can be changed by programming to adapt to the needs of different signal levels, thereby ensuring the quality and accuracy of the output signal. The laser 102, as a light source, can be used to emit a frequency-modulated laser beam (detection signal) onto a target object for area detection.

[0026] The control module 1011 is a component used to control the lidar, or at least to control the target detection process. Depending on the application requirements, the control module 1011 can employ one or more control components, including but not limited to at least one of the following: FPGA (Field Programmable Gate Array), DSP (Digital Signal Processor), or ASIC (Application Specific Integrated Circuit) chip. The control module 1011 can generate digital signals based on the detection requirements of the laser 102 (the detection requirements can be dynamically determined based on the current detection scenario, specified by configuration information, or configured by the user through control commands). These signals include clock signals, control signals, etc., used to synchronize and control the operation of the entire system. The control module 1011 can also monitor the bandwidth changes of the laser 102 in real time and adjust the gain of the programmable gain amplifier 1013 in real time according to the modulation bandwidth requirements of the laser 102 to ensure that the amplitude of the modulation signal matches the frequency changes.

[0027] The digital-to-analog converter (DAC) module 1012 can be connected to the control module 1011 and converts the digital signal generated by the control module 1011 into a continuously changing analog signal, providing a modulation signal source for subsequent programmable gain amplification. The DAC is the core component of the DAC module 1012, and its working principle is based on the mapping relationship between binary numbers and analog quantities. In the DAC, the input binary number (digital signal) can generate a current proportional to the weights of each bit of the binary number at the input of the operational amplifier through a control switch or current source. These currents are summed by the operational amplifier and converted into an analog voltage output (analog signal) proportional to the binary number.

[0028] In digital-to-analog conversion (DAC), each bit of the digital signal represents a weight (usually a power of 2). For example, in an 8-bit DAC, the most significant bit represents a weight of 128, the second most significant bit is 64, and so on, with the least significant bit being 1. When a digital signal is input to the DAC, it is converted into an analog signal proportional to the input digital signal. This analog signal can be in the form of voltage or current, and its continuously varying nature allows it to be used in analog devices.

[0029] In a frequency-modulated continuous wave lidar system, modulation bandwidth is a crucial parameter, determining the highest signal rate (for digital signals) or the maximum bandwidth of the analog signal that the laser 102 can output. To effectively match the analog signal with the modulation bandwidth of the laser 102, a programmable gain amplifier 1013 can be used to appropriately amplify or attenuate the signal. Here, the programmable gain amplifier 1013 can be connected to the digital-to-analog converter module 1012, and in response to gain control by the control module 1011, it amplifies the analog signal output by the digital-to-analog converter module 1012 to match the modulation bandwidth of the laser 102 by adjusting the amplification factor through programming. The amplified analog signal can then be used as a modulation signal to modulate the probe beam. Specifically, the process of modulating the probe beam can be found in related technologies, and will not be elaborated upon in this embodiment. The modulated beam is then emitted into the detection space for echo signal acquisition. This modulation method based on programmable gain can dynamically adapt to different detection requirements, improving the flexibility and accuracy of the lidar.

[0030] For example, a programmable gain circuit for nonlinear frequency modulation of a laser in a frequency-modulated continuous-wave lidar can be provided. This programmable gain circuit includes a control module for direct digital synthesis (DDS) and gain control, a DAC (Digital-to-Analog Converter) chip for converting digital signals to analog signals, and an amplifier for amplifying the analog signals to meet the laser's modulation bandwidth. The amplifier is designed as a programmable gain circuit, with gain adjustment directly controlled by the main control chip to achieve large dynamic range modulation. In use, the DAC output range can be adjusted to optimize both the output range and resolution.

[0031] According to the embodiments provided in this application, a frequency-modulated continuous wave lidar system includes a programmable gain circuit and a laser. The programmable gain circuit includes a control module, a digital-to-analog converter module, and a programmable gain amplifier. The laser is used to generate a probe beam. The control module is used to generate a digital signal and control the gain of the programmable gain amplifier according to the modulation bandwidth of the laser. The digital-to-analog converter module is connected to the control module and is used to convert the digital signal into an analog signal. The programmable gain amplifier is connected to the digital-to-analog converter module and, in response to the gain control of the control module, amplifies the analog signal to match the modulation bandwidth of the laser, and uses the amplified analog signal as a modulation signal to modulate the probe beam. The modulated probe beam is emitted into the detection space. By using the above-described frequency-modulated continuous wave lidar system, the problem of high resource requirements for the back-end receiving system in related technologies is solved, the dynamic range of the laser modulation bandwidth is improved, and the resource requirements for the back-end receiving system are reduced.

[0032] In one exemplary embodiment, the control module is further configured to increase the gain of the programmable gain amplifier when the modulation bandwidth of the laser is greater than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier; and to decrease the gain of the programmable gain amplifier when the modulation bandwidth of the laser is less than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier.

[0033] To enable the frequency-modulated continuous wave lidar system to adapt to different detection requirements and achieve optimal detection results while maintaining signal quality and system efficiency, the gain of the programmable gain amplifier can be dynamically adjusted via a control module. Taking a digital signal processor (DSP) as the control module as an example, the DSP's programmability allows users to write specific algorithms to implement gain control functions. In this embodiment, the control module can not only be used for signal generation and system control, but also monitor the modulation bandwidth of the laser in real time through internal algorithms and adjust the gain of the programmable gain amplifier as needed.

[0034] Optionally, the control module can acquire the modulation bandwidth of the laser. This operation can be achieved through a built-in sensor or by analyzing the frequency changes of the echo signal. When a change in the laser's modulation bandwidth is detected, the control module can directly implement a corresponding gain adjustment strategy, or wait for a specific opportunity to implement the corresponding gain adjustment strategy. The gain adjustment strategy could be: if the laser's modulation bandwidth is greater than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier, it indicates that the amplitude of the modulation signal needs to be increased, and the control module can send a control signal to the programmable gain amplifier to increase its gain; conversely, if the laser's modulation bandwidth is less than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier, it indicates that the amplitude of the modulation signal needs to be decreased, and the control module can send a control signal to the programmable gain amplifier to decrease its gain.

[0035] Here, the programmable gain amplifier is configured with multiple gain levels, each corresponding to a different gain coefficient. When a signal is received from the control module, the programmable gain amplifier switches to the corresponding gain level to ensure that, upon receiving the signal from the control module, the amplitude of the output signal is kept consistent with the modulation bandwidth of the laser through level switching.

[0036] For example, when a LiDAR on an autonomous vehicle enters a densely populated urban area, the target distance is relatively short, and the LiDAR needs to increase the modulation frequency to improve detection resolution. At this time, if the control module detects that the modulation bandwidth of the laser has increased to a level greater than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier, it can increase the gain of the programmable gain amplifier to ensure that the amplitude of the modulated signal can support higher frequency changes, thereby optimizing the effect of close-range detection. Conversely, when the vehicle enters an open area and the target distance is far, the LiDAR needs to decrease the modulation frequency to increase the detection range. At this time, if the control module detects that the modulation bandwidth of the laser has decreased to a level less than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier, it can correspondingly decrease the gain of the programmable gain amplifier to avoid unnecessary increases in signal amplitude and maintain system efficiency and signal quality.

[0037] In this embodiment, the gain of the programmable gain amplifier can be dynamically adjusted by the control module to match the modulation bandwidth of the laser, thereby improving the radar signal quality and detection range.

[0038] In one exemplary embodiment, the programmable gain amplifier can be implemented in various ways. It may include an amplifier or other components. The gain adjustment may be implemented by the amplifier itself or by other components besides the amplifier, as long as the gain can be adjusted accordingly according to the control of the control module.

[0039] As an optional implementation, the programmable gain amplifier can be a programmable gain transimpedance amplifier (PGA), an electronic device capable of automatically adjusting the gain of the output signal based on the strength of the input signal. The PGA has multiple resistance levels, each corresponding to a different gain resistor. The PGA is directly connected to a control module; that is, the control module can directly control the resistance level used by the PGA, thereby configuring the amplifier gain according to the laser modulation bandwidth. The PGA may include a resistor switch array; by changing the on / off state of the resistor switch array, different gain resistors can be selected, achieving programmability of the gain. The amplifier's gain value can be adjusted according to actual application requirements, thus enabling flexible, accurate, and wide dynamic range measurements.

[0040] Correspondingly, in this embodiment, the control module is also configured to set the resistance level of the programmable gain transimpedance amplifier according to the modulation bandwidth of the laser, so as to adjust the gain of the programmable gain transimpedance amplifier. When the modulation bandwidth of the laser changes, the control module can calculate the matching gain requirement of the programmable gain transimpedance amplifier and adjust the gain resistor in the programmable gain transimpedance amplifier, thereby changing its transimpedance gain and ensuring that the amplitude of the input signal matches the modulation bandwidth of the laser.

[0041] For example, such as Figure 2 As shown, the programmable gain circuit may include a controller, a DAC chip, and a programmable gain transimpedance amplifier. The controller can directly control the programmable gain transimpedance amplifier, thereby controlling the modulation signal output by the programmable gain transimpedance amplifier. Specifically, the controller (i.e., the control module) is used for direct digital frequency synthesis and gain control, the DAC chip is used to convert digital signals into analog signals, and the amplifier can be an integrated programmable gain transimpedance amplifier, which can be adjusted by the controller.

[0042] for Figure 2 The programmable gain circuit shown allows the amplifier gain to be configured according to the modulation bandwidth of the laser. A larger modulation bandwidth increases the amplifier gain, while a smaller modulation bandwidth decreases the amplifier gain to ensure the accuracy of the output modulation signal. The integrated programmable gain transimpedance amplifier circuit is simple. However, because the programmable gain transimpedance amplifier is integrated and the internal resistor values ​​are preset, the built-in gain cannot be flexibly configured.

[0043] By introducing a programmable gain transimpedance amplifier and dynamically adjusting its gain resistor using a control module, the gain of the programmable gain transimpedance amplifier can be adjusted to match the modulation bandwidth of the laser, thereby improving the stability and efficiency of the radar signal.

[0044] As an alternative implementation, the programmable gain amplifier can employ an operational amplifier combined with a multiplexer. The operational amplifier (Op-Amp or OP) is the core component of the programmable gain amplifier, providing high gain, high input impedance, and low output impedance. The operational amplifier may include a differential input stage, an intermediate amplification stage, and an output stage, capable of amplifying the input signal. A multiplexer (Mux) is an electronic device capable of selecting one or more signals from multiple input signals and transmitting them to a common output line.

[0045] To achieve gain adjustment, the programmable gain amplifier may also include a set of gain resistors in parallel. One end of the set of gain resistors is connected to one input of the operational amplifier, and each gain resistor in the set is connected to one input channel of the multiplexer. The output of the multiplexer is connected to the output of the operational amplifier. By selecting one or more gain resistors to use, dynamic gain adjustment can be achieved. The resistors in the parallel set of gain resistors can be programmable (e.g., their resistance values ​​can be changed via digital control), allowing for finer gain adjustment. The multiplexer can select different gain settings. By changing the input or control signals of the multiplexer, different resistors, resistor combinations, or feedback network configurations can be selected. The multiplexer can also be used in conjunction with other circuits (e.g., digital-to-analog converters) to achieve finer programmable gain control.

[0046] Correspondingly, the control module, connected to the multiplexer, is used to select one input channel of the multiplexer according to the modulation bandwidth of the laser to achieve gain switching of the operational amplifier. The modulation bandwidth of the laser corresponds to the gain resistor on the selected input channel of the multiplexer. This correspondence can be as close as possible, but does not need to be exactly the same. This is because the number of gain resistors is limited. Therefore, the modulation bandwidth corresponding to the gain resistor on the selected input channel of the multiplexer is closest to the modulation bandwidth of the laser. It can be larger than the modulation bandwidth of the laser and closest to it, or smaller than the modulation bandwidth of the laser and closest to it, or the absolute value of the bandwidth difference with the laser's modulation bandwidth can be the smallest. In this embodiment, the method of selecting the input channel is not limited.

[0047] To achieve high-precision current-to-voltage conversion, the operational amplifier can be configured in transimpedance amplification mode. This means that by selecting different gain resistors and combinations thereof, the amplifier's gain can be dynamically adjusted to meet the modulation bandwidth requirements of the laser. Each gain resistor has a different value, corresponding to a different gain coefficient. By selecting different gain resistors using a multiplexer, the transimpedance gain of the operational amplifier can be changed to ensure accurate signal amplification and avoid signal distortion or overload problems.

[0048] For example, such as Figure 3 As shown, the programmable gain circuit may include: a controller, a DAC chip, an operational amplifier, and a multiplexer. The control module is used for direct digital frequency synthesis (DDS) and gain control. The DAC chip converts digital signals to analog signals. The operational amplifier is configured for transimpedance amplification mode and selects the gain resistor according to the required gain for different modulation bandwidths. The multiplexer is connected to the gain resistor and the operational amplifier, and is selected by the controller to achieve gain switching. This programmable gain circuit can flexibly select the gain resistor according to the laser characteristics and modulation bandwidth.

[0049] The programmable gain amplifier described above allows for the selection of gain resistors based on the required gain for different modulation bandwidths. The multiplexer, through the controller, enables gain switching. This circuit allows for flexible selection of gain resistors based on laser characteristics and modulation bandwidth. By employing a programmable gain amplifier design with multiplexing gating control, the performance of automatically adjusting the gain of the laser modulation bandwidth can be improved.

[0050] As another optional implementation, the programmable gain amplifier can adopt a structure combining a differential proportional amplifier and two multiplexers. Furthermore, the programmable gain amplifier can also include two sets of gain resistors, with each multiplexer and set of gain resistors corresponding to one another. The differential proportional amplifier is configured in differential proportional amplification mode. One end of the first set of gain resistors is connected in parallel to the first input terminal of the differential proportional amplifier. Each first gain resistor in the first set is connected to one input channel of the multiplexer corresponding to the first set of gain resistors. One end of the second set of gain resistors is connected in parallel to the second input terminal of the differential proportional amplifier. Each second gain resistor in the second set is connected to one input channel of the multiplexer corresponding to the second set of gain resistors. The output terminals of both multiplexers are connected to the output terminal of the differential proportional amplifier. This structure expands the adjustable range of the gain, thereby increasing the adjustable range of the modulation bandwidth.

[0051] Correspondingly, the control module, connected to two multiplexers, selects one input channel from the two multiplexers according to the laser's modulation bandwidth to achieve gain switching of the differential amplifier. Both sets of gain resistors consist of multiple resistors with different gain values, each corresponding to a different gain value, with the resistance value inversely proportional to the gain. When the control module needs to increase the gain of the programmable gain amplifier, it selects a resistor with a smaller resistance value; when it needs to decrease the gain, it selects a resistor with a larger resistance value. The laser's modulation bandwidth corresponds to the gain resistor on one input channel selected by the two multiplexers.

[0052] For example, such as Figure 4 As shown, the programmable gain amplifier may include: a controller, a DAC chip, a differential amplifier, and multiplexers. The controller is used for direct digital frequency synthesis and gain control. The DAC chip is used to convert digital signals into analog signals. The operational amplifier is configured in differential amplifier mode and sets the gain resistor according to the gain required for different modulation bandwidths. There are two multiplexers, each connected to a set of gain resistors, which are synchronously selected by the controller to achieve gain switching.

[0053] The control module can monitor the modulation bandwidth of the laser in real time. When the modulation bandwidth changes, the control module can select one input channel of the two multiplexers according to the preset modulation bandwidth-gain resistor mapping relationship, thereby adjusting the gain of the differential amplifier to adapt to the change in the laser modulation bandwidth. The modulation bandwidth of the laser corresponds to the gain resistor on one input channel selected by the two multiplexers.

[0054] The dynamic range of laser modulation bandwidth can be improved by introducing a programmable gain amplifier with dual-channel gain adjustment, as described above.

[0055] In one exemplary embodiment, for the aforementioned programmable gain amplifier comprising a set of gain resistors, the resistance values ​​of the different gain resistors in the set of gain resistors are different, and the different gain resistors correspond to different gains, that is, to different modulation bandwidths. The resistance value is inversely proportional to the gain; the smaller the resistance value, the greater the gain of the amplifier; the larger the resistance value, the smaller the gain. Correspondingly, the control module is further configured to determine the input channel connected to the gain resistor corresponding to the modulation bandwidth of the laser in the set of gain resistors as the selected input channel according to the preset modulation bandwidth corresponding to each gain resistor.

[0056] Considering that the circuit structure is fixed and the modulation bandwidth corresponding to each gain resistor is stable, that is, it will not change significantly with time, in order to improve the convenience of gain adjustment, in this embodiment, the modulation bandwidth corresponding to each gain resistor can be preset. When it is necessary to select the input channel, the input channel connected to the gain resistor corresponding to the modulation bandwidth of the laser can be determined as the selected input channel according to the preset modulation bandwidth corresponding to each gain resistor.

[0057] Optionally, each gain resistor can correspond to a modulation bandwidth range, facilitating modulation bandwidth matching. Alternatively, the modulation bandwidth corresponding to each gain resistor can be set as a reference modulation bandwidth. When performing modulation bandwidth matching, any modulation bandwidth matching method as described in the preceding embodiments can be used; this embodiment does not impose any limitations on this method.

[0058] In this embodiment, by pre-setting the correspondence between the gain resistor and the modulation bandwidth, when gain adjustment is required, the corresponding gain resistor is determined based on the set correspondence, and then the selected input channel is determined, which improves the convenience and efficiency of gain adjustment.

[0059] In an exemplary embodiment, when the multiplexer is selected, the on-resistance changes with external conditions such as ambient temperature, causing the feedback loop impedance to be unstable. In order to improve the accuracy of the output signal, in this embodiment, the multiplexer can be connected in a "Kelvin switch" mode. That is, the frequency modulated continuous wave lidar system also includes two switches connected in series. One switch is connected to the output of the operational amplifier, and the other switch is connected to the laser, so that the multiplexer is connected in a Kelvin switch mode. This connection can be used to eliminate the influence of the switch introduced into the feedback loop.

[0060] When the programmable gain amplifier (PLA) is in operation, the control module opens the first switch connected to the operational amplifier's output, allowing the signal to be output smoothly from the PLA. Simultaneously, the control module opens the second switch connected to the laser, ensuring the signal is transmitted directly and cleanly to the laser for beam modulation. During non-signal transmission periods, the control module closes both switches to disconnect the PLA from the laser, preventing parasitic effects on the signal path from accumulating in the absence of a signal and affecting the quality of subsequent signal transmissions.

[0061] Optionally, the two switches connected in series in the frequency modulated continuous wave lidar system can be electronic switches, optical switches, or other types of fast switching switches to ensure rapid response during signal transmission and disconnection; at the same time, the algorithm in the control module can also be responsible for switching the Kelvin switch to ensure that the signal can pass through the optimal path during transmission, reducing signal loss and noise interference.

[0062] This embodiment optimizes the signal transmission path between the programmable gain amplifier and the laser in the frequency modulated continuous wave lidar system by introducing a Kelvin switching mode, eliminating the influence of the switch introduced in the feedback loop and improving the accuracy of the output signal.

[0063] In one exemplary embodiment, for the aforementioned programmable gain amplifier comprising two sets of gain resistors, the resistance values ​​of different gain resistors within the same set are different, and different gain resistors can correspond to different modulation bandwidths. Considering the connection methods of the different sets of gain resistors, for two gain resistors with the same resistance value in different sets of gain resistors, their corresponding modulation bandwidths are also different. Therefore, the resistance values ​​of two gain resistors in different sets of gain resistors can be the same or different.

[0064] Correspondingly, the control module is also used to determine the input channel connected to the gain resistor corresponding to the modulation bandwidth of the laser in the two sets of gain resistors, based on the preset modulation bandwidth corresponding to each first gain resistor and the modulation bandwidth corresponding to each second gain resistor.

[0065] The two sets of gain resistors may include a first set of gain resistors and a second set of gain resistors, wherein the gain resistors in the first set of gain resistors are first gain resistors, and the gain resistors in the second set of gain resistors are second gain resistors. In this embodiment, the modulation bandwidth corresponding to each first gain resistor and the modulation bandwidth corresponding to each second gain resistor can be preset in the same or similar manner as in the previous embodiments. Accordingly, when gain adjustment is required, a matching gain resistor can be selected from the two sets of gain resistors based on the set correspondence.

[0066] For example, when the modulation bandwidth of the laser increases, the control module determines the input channel connected to the gain resistor corresponding to the modulation bandwidth of the laser as the selected input channel according to the preset modulation bandwidth corresponding to each first gain resistor and the modulation bandwidth corresponding to each second gain resistor, so as to increase the gain of the differential amplifier, and vice versa.

[0067] In this embodiment, by pre-setting the correspondence between the gain resistor and the modulation bandwidth, when gain adjustment is required, the corresponding gain resistor is determined based on the set correspondence, and then the selected input channel is determined, which improves the convenience and efficiency of gain adjustment.

[0068] In an exemplary embodiment, the digital-to-analog converter module is a current-mode DAC chip. Correspondingly, the aforementioned programmable gain amplifier and digital-to-analog converter module can both be implemented using a current-mode DAC chip. For example, the implementation scheme of the programmable gain amplifier can be one of the following: current-mode DAC + programmable gain transimpedance amplifier, current-mode DAC + operational amplifier + multiplexer, current-mode DAC + differential proportional amplifier + multiplexer.

[0069] Optionally, in this embodiment, the frequency modulated continuous wave lidar system further includes: a load resistor, used as the output load of a current-type DAC chip to convert the analog signal from a current signal to a voltage signal.

[0070] The control module can generate a digital modulation signal according to system requirements. The digital modulation signal may contain the frequency information of the laser pulse. The digital-to-analog converter module receives the digital modulation signal and converts it into an analog current signal as the input for subsequent signal processing. Here, the digital-to-analog converter module can be a current-type DAC chip.

[0071] In this embodiment, the frequency-modulated continuous wave lidar system may further include a load resistor. The load resistor can be used as the output load of a current-mode DAC chip, converting the current signal output by the current-mode DAC chip into a proportional voltage signal, providing a suitable signal format for the programmable gain amplifier to process. At the same time, the voltage signal converted by the load resistor can provide precise signal amplitude control, avoiding distortion during the signal conversion process.

[0072] In this embodiment, the current signal is first converted into a voltage signal and then amplified. The gain resistor can be flexibly selected according to the characteristics of the laser and the modulation bandwidth, thereby optimizing the signal processing flow in the frequency modulated continuous wave lidar system.

[0073] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0074] Obviously, those skilled in the art should understand that the modules or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those presented here, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0075] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A frequency-modulated continuous wave lidar system, characterized in that, include: A programmable gain circuit and a laser, wherein the programmable gain circuit includes: a control module, a digital-to-analog converter module, and a programmable gain amplifier, wherein... The laser is used to generate a probe beam; The control module is used to generate digital signals and control the gain of the programmable gain amplifier according to the modulation bandwidth of the laser. The digital-to-analog converter module is connected to the control module and is used to convert the digital signal into an analog signal; The programmable gain amplifier, connected to the digital-to-analog converter module, is used to amplify the analog signal to match the modulation bandwidth of the laser in response to the gain control of the control module, and to use the amplified analog signal as a modulation signal to modulate the probe beam, wherein the modulated probe beam is emitted into the detection space.

2. The frequency-modulated continuous wave lidar system according to claim 1, characterized in that, The control module is further configured to increase the gain of the programmable gain amplifier when the modulation bandwidth of the laser is greater than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier; and to decrease the gain of the programmable gain amplifier when the modulation bandwidth of the laser is less than the modulation bandwidth corresponding to the current gain of the programmable gain amplifier.

3. The frequency-modulated continuous wave lidar system according to claim 1, characterized in that, The programmable gain amplifier is a programmable gain transimpedance amplifier, which is directly connected to the control module. The programmable gain transimpedance amplifier is configured with multiple resistance levels, each corresponding to a different gain resistor. The control module is also configured to configure the resistance level of the programmable gain transimpedance amplifier according to the modulation bandwidth of the laser, so as to adjust the gain of the programmable gain transimpedance amplifier.

4. The frequency-modulated continuous wave lidar system according to claim 1, characterized in that, The programmable gain amplifier includes: an operational amplifier, a set of gain resistors connected in parallel, and a multiplexer. The operational amplifier is configured in transimpedance amplification mode. One end of the set of gain resistors is connected to one input terminal of the operational amplifier. Each gain resistor in the set of gain resistors is connected to one input channel of the multiplexer. The output terminal of the multiplexer is connected to the output terminal of the operational amplifier. The control module is connected to the multiplexer and is used to select one input channel of the multiplexer according to the modulation bandwidth of the laser to realize the gain switching of the operational amplifier. The modulation bandwidth of the laser corresponds to the gain resistor on the selected input channel of the multiplexer.

5. The frequency-modulated continuous wave lidar system according to claim 4, characterized in that, The resistance values ​​of the different gain resistors in the set of gain resistors are all different; The control module is further configured to determine the input channel connected to the gain resistor corresponding to the modulation bandwidth of the laser in the set of gain resistors as the selected input channel according to the preset modulation bandwidth corresponding to each gain resistor.

6. The frequency-modulated continuous wave lidar system according to claim 4, characterized in that, The frequency-modulated continuous wave lidar system includes two switches connected in series. One of the switches is connected to the output of the operational amplifier, and the other switch is connected to the laser, so as to connect the multiplexer in Kelvin switch mode.

7. The frequency-modulated continuous wave lidar system according to claim 1, characterized in that, The programmable gain amplifier includes: a differential proportional amplifier, two sets of gain resistors, and two multiplexers corresponding one-to-one with the two sets of gain resistors. The differential proportional amplifier is configured in differential proportional amplification mode. One end of the first set of gain resistors is connected in parallel and to the first input terminal of the differential proportional amplifier. Each first gain resistor in the first set of gain resistors is connected to one input channel of the multiplexer corresponding to the first set of gain resistors. One end of the second set of gain resistors is connected in parallel and to the second input terminal of the differential proportional amplifier. Each second gain resistor in the second set of gain resistors is connected to one input channel of the multiplexer corresponding to the second set of gain resistors. The output terminals of the two multiplexers are both connected to the output terminal of the differential proportional amplifier. The control module is connected to the two multiplexers and is used to select one input channel of the two multiplexers according to the modulation bandwidth of the laser to realize the gain switching of the differential amplifier. The modulation bandwidth of the laser corresponds to the gain resistor on the selected input channel of the two multiplexers.

8. The frequency-modulated continuous wave lidar system according to claim 7, characterized in that, The resistance values ​​of different gain resistors in the same group of the two groups of gain resistors are different. The control module is further configured to determine the input channel connected to the gain resistor corresponding to the modulation bandwidth of the laser among the two sets of gain resistors, based on the preset modulation bandwidth corresponding to each first gain resistor and the modulation bandwidth corresponding to each second gain resistor, as the selected input channel.

9. The frequency-modulated continuous wave lidar system according to claim 1, characterized in that, The digital-to-analog converter module is a current-mode DAC chip; the frequency-modulated continuous wave lidar system also includes: The load resistor serves as the output load of the current-mode DAC chip, converting the analog signal from a current signal to a voltage signal, wherein the converted analog signal is output to the programmable gain amplifier.

10. The frequency-modulated continuous wave lidar system according to any one of claims 1 to 9, characterized in that, The control module is one of the following: a field-programmable gate array, a digital signal processor, or an application-specific integrated circuit (ASIC).

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