Stepped Frequency Radar System, System Delay Determination Method, and Radar Ranging Method

Abstract

The present application provides a stepped-frequency radar system, a system delay determination method, and a radar ranging method. Among them, the stepped-frequency radar system is provided with at least two PLL circuits for generating local oscillator signals, and the local oscillator frequencies configured for each PLL circuit form an arithmetic sequence with a common difference equal to the local oscillator frequency step. During the process of transmitting radar signals, the control module can select one of multiple PLL circuits according to the current local oscillator frequency, and pre-configure the local oscillator frequencies of other PLL circuits so that other PLL circuits can adjust their local oscillator frequencies in advance. In the case where the current local oscillator frequency needs to hop, the control module can achieve frequency switching by selecting another PLL circuit. Thus, it can be seen that the present application can achieve fast switching of frequency points through the alternating output of multiple PLL circuits, and the system error can be accurately measured, taking into account the advantages of high frequency stability, good phase noise, few spurs, and low cost.

Description

Technical Field

[0001] The present application relates to the technical field of stepped frequency radar, and in particular to a stepped frequency radar system, a method for determining system delay, and a radar ranging method. Background Art

[0002] like Figure 1 As shown in the figure, SFCW (Stepped Frequency Continuous Waveform) is one of the commonly used signal forms of radar systems. Compared with pulse radar systems, stepped frequency radar systems have the advantages of high distance resolution, strong anti-interference ability, strong penetration ability, and strong controllability, so they are more suitable for various complex working environments.

[0003] In a stepped frequency radar system, the frequency hopping time of a single frequency point is an important indicator for measuring the system. The shorter the frequency hopping time of a single frequency point, the higher the frame rate and the better the scanning imaging effect. At present, stepped frequency radar systems mainly use two methods to generate radar signals: the first is to use DDS (Direct Digital Synthesizer) and DAC (Digital to Analog Converter) to generate stepped frequency radar signals, and the second is to use PLL (Phase Locked Loop) to generate directly.

[0004] Although the first method has the advantages of fast frequency switching speed and good phase continuity, the output frequency range of the DAC depends on the performance of the DAC and the sampling clock, so the output range of this method is limited. At the same time, the output of the DDS and DAC will produce high-order aliasing, resulting in more spurious phase noise in the radar signal, which is difficult to filter out. If high-performance DDS and DAC are used in the stepped frequency radar system, there is a problem of high cost.

[0005] Based on the above considerations, in order to realize a stepped frequency radar system with high frequency stability, good phase noise, less spurious and low cost, the PLL method is currently usually used to generate radar signals. In this implementation method, the baseband signal frequency is fixed, and the PLL is used to generate the local oscillator signal and increase the frequency of the local oscillator signal according to the frequency step. In this way, after mixing the baseband signal and the local oscillator signal, a stepped frequency radar signal can be obtained. However, the PLL needs to be calibrated after switching to a single frequency point. Only after calibration can it output a local oscillator signal with a stable frequency, and there is a problem of slow frequency switching speed. Summary of the invention

[0006] The purpose of the present application is to solve at least one of the above-mentioned technical defects, especially the technical defects of slow frequency switching speed and complex calibration of system fixed delay error in the prior art.

[0007] In a first aspect, an embodiment of the present application provides a stepped frequency radar system, including:

[0008] A baseband signal generating module, used for generating a baseband signal;

[0009] A local oscillator signal generating module, comprising a multiplexer and at least two PLL circuits, wherein the output end of each of the PLL circuits is connected to a plurality of input ends of the multiplexer in a one-to-one correspondence; the PLL circuit is used to generate a local oscillator signal according to a configured local oscillator frequency;

[0010] A control module, connected to the control end of the multiplexer and the control end of each of the PLL circuits, respectively, for respectively configuring the local oscillator frequency of each of the PLL circuits according to the local oscillator frequency sequence; further for determining the current local oscillator frequency, and outputting a selection signal to the multiplexer based on the current local oscillator frequency, so that the multiplexer selects the PLL circuit corresponding to the current local oscillator frequency; wherein the local oscillator frequency sequence is an arithmetic progression with a tolerance equal to the local oscillator frequency step length, and the local oscillator frequencies configured for each of the PLL circuits are different from each other;

[0011] The first frequency mixing module is connected to the baseband signal generating module and the output end of the multiplexer respectively, and is used to perform up-conversion processing on the baseband signal and the local oscillator signal output by the multiplexer to obtain a radar signal.

[0012] In some embodiments, the baseband signal generation module includes:

[0013] The DDS circuit is connected to the first mixing module and is used to perform frequency hopping according to the baseband frequency sequence and sequentially generate baseband signals corresponding to each sequence element; wherein the baseband frequency sequence is an arithmetic sequence with a tolerance equal to the baseband frequency step length.

[0014] In some embodiments, the baseband frequency step length is the frequency step length of the radar signal, and the number of sequence elements of the baseband frequency sequence is determined according to the baseband effective bandwidth of the stepped frequency radar system and the baseband frequency step length;

[0015] The local oscillator frequency step is the product of the number of elements in the sequence and the baseband frequency step.

[0016] In some embodiments, the control module is connected to the DDS circuit;

[0017] The control module is used to control the DDS circuit to generate a baseband signal corresponding to the first sequence element in the baseband frequency sequence when the current baseband signal frequency is the last sequence element in the baseband frequency sequence and the radar signal needs to frequency hop, and to update the current local oscillator frequency according to the local oscillator frequency step size.

[0018] In some embodiments, the control module is used to determine a first target local oscillator frequency from the local oscillator frequency series based on the configured local oscillator frequency when it is determined that the current local oscillator frequency has been updated, and configure the local oscillator frequency of the target PLL circuit to the first target local oscillator frequency; wherein the target PLL circuit is the PLL circuit corresponding to the current local oscillator frequency before the update.

[0019] In some embodiments, the stepped frequency radar system further comprises:

[0020] a second frequency mixing module, connected to the output end of the multiplexer, for performing down-conversion processing on the received echo signal and the local oscillator signal output by the multiplexer, and obtaining a first intermediate frequency signal;

[0021] The echo processing module is connected to the second mixing module and is used to perform signal processing on the first intermediate frequency signal to obtain a second intermediate frequency signal.

[0022] In the stepped frequency radar system provided in some embodiments of the present application, at least two PLL circuits for generating local oscillator signals are provided, and the local oscillator frequencies configured for each PLL circuit constitute an arithmetic progression with a tolerance of the local oscillator frequency step length. In the process of transmitting radar signals, the control module can select one of the multiple PLL circuits according to the current local oscillator frequency, and configure the local oscillator frequencies of other PLL circuits in advance, so that the other PLL circuits can adjust their local oscillator frequencies in advance. In the case where the current local oscillator frequency needs to be hopped, the control module can achieve frequency switching by selecting another PLL circuit. It can be seen from this that the present application can achieve rapid switching of frequency points through the alternating output of multiple PLL circuits, and can take into account the advantages of high frequency stability, good phase noise, less spurious and low cost.

[0023] In a second aspect, an embodiment of the present application provides a method for determining system delay, the method comprising:

[0024] The stepped frequency radar system of any of the above embodiments transmits at least one group of radar signals; wherein the same group of radar signals includes multiple radar signals generated based on the same local oscillator frequency, and the signal frequencies of the same group of radar signals constitute a radar frequency sequence, and the radar frequency sequence is an arithmetic sequence with a tolerance equal to the baseband frequency step length;

[0025] Receiving at least one set of calibration echo signals; the calibration echo signals are obtained by reflecting a calibration object located at a preset distance, or the calibration echo signals are obtained by transmitting the radar signal using a cable of a preset length;

[0026] Using the second frequency mixing module and the echo processing module of the stepped frequency radar system to process the at least one set of calibration echo signals, and obtain at least one set of calibration intermediate frequency signals;

[0027] Taking the position of the signal frequency of the radar signal in the corresponding radar frequency series as the independent variable and the phase characteristic of the calibration intermediate frequency signal as the dependent variable, data fitting is performed on each group of the calibration intermediate frequency signals, and the system delay of the stepped frequency radar system is obtained based on the fitting results; wherein the system delay is used for data calibration.

[0028] In some embodiments, at least one set of radar signals is transmitted using a stepped frequency radar system, including:

[0029] The stepped frequency radar system is used to transmit A group of radar signals; among which, , is the total number of frequency hopping points of the stepped frequency radar system, is the number of baseband frequency hopping points of the stepped frequency radar system;

[0030] Taking the position of the signal frequency of the radar signal in the corresponding radar frequency series as the independent variable and the phase characteristic of the calibration intermediate frequency signal as the dependent variable, performing data fitting on each group of the calibration intermediate frequency signals, and obtaining the system delay of the stepped frequency radar system based on the fitting results, including:

[0031] The position of the signal frequency of the radar signal in the corresponding radar frequency series is used as the independent variable, and the phase characteristic of the calibration intermediate frequency signal is used as the dependent variable. The calibration intermediate frequency signal of the target group is fitted with data, and the system delay corresponding to the second target local oscillator frequency is obtained based on the fitting result of the target group; wherein the target group is For any group of intermediate frequency signals in the group calibration, the second target local oscillator frequency is the local oscillator frequency corresponding to the target group.

[0032] In some embodiments, performing data fitting on the calibration intermediate frequency signal of the target group, and obtaining the system delay corresponding to the second target local oscillator frequency based on the fitting result of the target group, includes:

[0033] Performing linear fitting on each calibration intermediate frequency signal of the target group and obtaining a fitting slope;

[0034] The system delay corresponding to the second target local oscillator frequency is calculated based on the following expression:

[0035]

[0036] In the formula, is the fitting slope; , is the frequency step of the radar signal; , R is the preset distance, C is the speed of light; is the system delay corresponding to the second target local oscillator frequency.

[0037] In the system delay determination method provided in some embodiments of the present application, a group of calibration echo signals generated by multiple radar signals corresponding to a single local oscillator frequency can be received, and each group of calibration echo signals can be processed respectively by multi-point data fitting to calculate the system delay of the stepped frequency radar system. In this way, the system delay of the stepped frequency radar system can be determined simply and quickly.

[0038] In a third aspect, an embodiment of the present application provides a radar ranging method, the method comprising:

[0039] The stepped frequency radar system provided by the above embodiment is used to transmit Group radar signal;

[0040] Receive the reflected light from the object to be measured Group ranging echo signal;

[0041] The second frequency mixing module and the echo processing module of the stepped frequency radar system are used to The ranging echo signal is processed and obtained Group ranging intermediate frequency signal;

[0042] According to the system delay corresponding to each group of the ranging intermediate frequency signals, The ranging intermediate frequency signal is corrected and obtained A group of corrected intermediate frequency signals; wherein the system delay is determined by the system delay determination method of any of the above embodiments;

[0043] Based on the The corrected intermediate frequency signal is formed to obtain the distance value of the object to be measured.

[0044] In the radar ranging method provided in some embodiments of the present application, each group of ranging intermediate frequency signals can be corrected in sections according to the system delay corresponding to each group of ranging intermediate frequency signals, so as to compensate the initial phase of the baseband signal in sections, and perform ranging calculation based on the corrected intermediate frequency signal. Compared with the existing correction method, this scheme has the advantages of simple and fast correction, and can achieve accurate ranging. It can be seen that the present application can simplify the correction process and improve the efficiency of ranging calculation on the basis of ensuring the accuracy of the ranging result. In addition, in the process of receiving the echo signal, the receiving time can be flexibly selected, which has the advantage of high flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0046] Figure 1 is the frequency-time diagram of the stepped frequency radar signal;

[0047] Figure 2 is one of the structural schematic diagrams of a stepped frequency radar system in one embodiment;

[0048] Figure 3 FIG2 is a second structural diagram of a stepped frequency radar system in one embodiment;

[0049] Figure 4 A schematic diagram of a stepped frequency radar system generating fast frequency points in one embodiment;

[0050] Figure 5 A schematic diagram of a flow chart of a method for determining system delay in one embodiment;

[0051] Figure 6 A schematic diagram of a flow chart of a radar ranging method in one embodiment;

[0052] Figure 7 is the uncorrected frequency-amplitude diagram;

[0053] Figure 8 Based on Figure 7 The obtained distance-amplitude time domain diagram;

[0054] Fig. 9 This is the frequency-amplitude diagram after correction using this application;

[0055] Fig.10 Based on Fig. 9 The resulting distance-amplitude time domain plot. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0057] In some embodiments, the present application provides a stepped frequency radar system. In the stepped frequency radar system, the radar signal is obtained by up-converting the baseband signal and the local oscillator signal, and the signal frequency of the radar signal may be the sum of the signal frequency of the baseband signal and the signal frequency of the local oscillator signal. After the radar signal is transmitted, objects in the space will reflect the radar signal to form an echo signal. The stepped frequency radar system can receive the echo signal and down-convert the echo signal and the local oscillator signal to obtain a down-converted signal. It can be understood that the frequency of the down-converted signal may be the difference between the signal frequency of the echo signal and the signal frequency of the local oscillator signal.

[0058] In some embodiments, Figure 2 As shown, the stepped frequency radar system provided by the present application includes: a baseband signal generating module 110, a local oscillator signal generating module 120, a control module 130 and a first mixing module 140. It should be noted that in addition to the module structure listed in the present application, the stepped frequency radar system may include more components, such as: a transceiver antenna, a signal preprocessing circuit, etc.

[0059] The baseband signal generating module 110 refers to a module device for generating and outputting a baseband signal, the local oscillator signal generating module 120 refers to a module device for generating and outputting a local oscillator signal, and the first frequency mixing module 140 refers to a module device for up-converting the baseband signal and the local oscillator signal. The control module 130 can be used to control the local oscillator signal generating module 120 so that the local oscillator signal generating module 120 outputs a local oscillator signal that meets the requirements, so that the radar signal transmitted by the stepped frequency radar system can be a stepped frequency radar signal.

[0060] It is understood that the specific implementation of the control module 130, the baseband signal generating module 110 and the first mixing module 140 can be determined according to actual conditions, and this document does not impose specific restrictions on this. In some examples, the control module 130 can be implemented based on FPGA (Field Programmable Gate Array).

[0061] The local oscillator signal generating module 120 includes a multiplexer 121 and at least two PLL circuits 122, each of which is used to generate a local oscillator signal LO according to the configured local oscillator frequency. It can be understood that the specific number of PLL circuits can be determined based on actual conditions such as frequency switching speed requirements, radar volume requirements, cost requirements, etc., and this document does not impose specific restrictions on this, as long as the number is greater than or equal to 2. Exemplarily, the number of PLL circuits can be 3, 5, 10, etc. For ease of description, some embodiments of the present application are described with two PLL circuits, and the two PLL circuits are respectively a first PLL circuit and a second PLL circuit.

[0062] The multiplexer 121 is a device that selects a specified signal from one or more input signals for output. When the multiplexer 121 is connected to multiple input signals, the multiplexer 121 will select one of them for output. In the present application, the output ends of the multiple PLL circuits 122 are connected to the multiple input ends of the multiplexer 121 in a one-to-one correspondence, so that the local oscillator signals generated by the multiple PLL circuits 122 constitute the multiple input signals of the multiplexer 121.

[0063] The control module 130 is connected to the control end of each PLL circuit 122, and is used to configure the local oscillator frequency of each PLL circuit 122 according to the local oscillator frequency sequence, and the local oscillator frequencies configured for each PLL circuit 122 are different from each other in a complete radar signal transmission cycle. The local oscillator frequency sequence is an arithmetic progression with a tolerance of the local oscillator frequency step length. When the local oscillator frequency step length is When , the local oscillator frequency series can be , , … .in, is the starting frequency of the radar signal, is the cutoff frequency of the radar signal. Further, the local oscillator frequency step size can be predetermined. In some examples, the local oscillator frequency step size can be the frequency step size of the radar signal. In other examples, the LO frequency step size can be Several times of.

[0064] For example, when the local oscillator frequency series is , , , , When the local oscillator signal generating module 120 includes four PLL circuits 122, the control module 130 may configure the local oscillator frequency of the first PLL circuit to , configure the local oscillator frequency of the second PLL circuit to , configure the local oscillator frequency of the third PLL circuit to , the local oscillator frequency of the fourth PLL circuit is configured as , the local oscillator frequency of the fifth PLL circuit 122 is configured as .

[0065] For another example, if the local oscillator signal generating module 120 includes two PLL circuits, the control module 130 may first configure the local oscillator frequency of the first PLL circuit to , configure the local oscillator frequency of the second PLL circuit to The local oscillator signal used in the up-conversion is Jump to In the case of The local oscillator signal used in the up-conversion is Jump to In this case, the local oscillator frequency of the second PLL circuit is configured as , and so on, until a complete radar signal transmission cycle is completed. In the next radar signal transmission cycle, the control module 130 can repeat the above process to configure the local oscillator frequency.

[0066] The control module 130 is also connected to the control end of the multiplexer 121. The control module 130 can be used to determine the current local oscillator frequency and output a selection signal to the multiplexer 121 based on the current local oscillator frequency, so that the multiplexer 121 selects the PLL circuit corresponding to the current local oscillator frequency. The current local oscillator frequency refers to the local oscillator frequency required to generate the current radar signal. For example, if the stepped frequency radar signal currently needs to transmit at a frequency of , then the current local oscillator frequency can be ; If the stepped frequency radar signal currently needs to transmit at a frequency of , then the current local oscillator frequency can be . is the signal frequency of the baseband signal.

[0067] The PLL circuit corresponding to the current local oscillation frequency refers to a PLL circuit whose configured local oscillation frequency is the current local oscillation frequency. For example, the local oscillation signal generating module 120 includes a first PLL circuit and a second PLL circuit, and the local oscillation frequency configured for the first PLL circuit is , so that the first PLL circuit can output a frequency of The local oscillator frequency of the second PLL circuit is configured as , so that the second PLL circuit can output a frequency of The local oscillator signal. If the current local oscillator frequency is , then the PLL circuit corresponding to the current local oscillator frequency is the first PLL circuit. , then the PLL circuit corresponding to the current local oscillator frequency refers to the second PLL circuit.

[0068] The first frequency mixing module 140 is connected to the output ends of the baseband signal generating module 110 and the multiplexer 121 respectively, and can perform up-conversion processing on the baseband signal output by the baseband signal generating module 110 and the local oscillator signal output by the multiplexer 121, so as to obtain a radar signal. By configuring the local oscillator frequency of each PLL circuit 122 and adjusting the gating state of the multiplexer 121, the output end of the multiplexer 121 can output local oscillator signals with different local oscillator frequencies, so that the radar signal obtained by the up-conversion processing can be a stepped frequency radar signal.

[0069] In the present application, at least two PLL circuits 122 are provided for generating local oscillator signals, and the local oscillator frequencies configured for each PLL circuit 122 constitute an arithmetic progression with a tolerance of the local oscillator frequency step length. In the process of transmitting radar signals, the control module 130 can select one of the multiple PLL circuits 122 according to the current local oscillator frequency, and configure the local oscillator frequencies of other PLL circuits 122 in advance, so that other PLL circuits 122 can adjust their local oscillator frequencies in advance. In the case where the current local oscillator frequency needs to be hopped, the control module 130 can achieve frequency switching by selecting another PLL circuit 122. It can be seen that the present application can achieve fast switching of frequency points through the alternating output of multiple PLL circuits 122, and can take into account the advantages of high frequency stability, good phase noise, less spurious and low cost.

[0070] In some embodiments, the number of PLL circuits is limited due to factors such as cost and radar system volume. Since the PLL circuit 122 needs a certain amount of time to output a local oscillator signal with a stable frequency, if the stepped frequency radar signal is realized by simply changing the local oscillator frequency, the frequency switching requirements of specific application scenarios cannot be met. In order to further improve the frequency switching speed, the present embodiment can quickly adjust the frequency of the baseband signal through DDS, and further improve the switching speed by combining baseband signal frequency hopping with local oscillator signal frequency hopping.

[0071] In this embodiment, Figure 3 As shown, the baseband signal generation module 110 may include a DDS circuit. The DDS circuit refers to a circuit that uses direct digital synthesis technology to generate and output a baseband signal. Its specific circuit structure can be determined according to actual conditions, and this application does not impose specific restrictions on this.

[0072] The DDS circuit can be connected to the first mixing module 140, and is used to perform frequency hopping according to the baseband frequency sequence, and sequentially generate baseband signals corresponding to each sequence element of the baseband frequency sequence. It can be understood that the baseband frequency sequence includes n baseband frequencies (n≥2), and each sequence element of the baseband frequency sequence refers to n baseband frequencies.

[0073] The baseband frequency sequence is an arithmetic sequence with a tolerance equal to the baseband frequency step length. When , the baseband frequency series can be , , 3 ……n Furthermore, the baseband frequency step size may be predetermined. In one example, the baseband frequency step size may be the frequency step size of the radar signal. .

[0074] The DDS circuit can perform frequency hopping according to the baseband frequency series and output signal frequencies in sequence. , 2 , 3 ……n When the frequency of the local oscillator signal output by the multiplexer 121 remains unchanged, since the DDS circuit outputs baseband signals with different frequencies, the frequency of the radar signal also changes after the up-conversion process. In this way, a stepped frequency radar signal can be realized by frequency hopping of the baseband signal and the local oscillator signal.

[0075] In this embodiment, the DDS can be used to quickly switch to generate an equidistant baseband signal, and the transmission frequency point of the frequency-stepping radar can be quickly generated by up-conversion.

[0076] In some embodiments, the baseband frequency step size is the frequency step size of the radar signal, that is, The number of array elements of the baseband frequency array can be determined according to the baseband effective bandwidth and the baseband frequency step length of the stepped frequency radar system. The local oscillator frequency step length is the product of the number of array elements and the baseband frequency step length.

[0077] In this embodiment, if the starting frequency of the stepped frequency radar system is , the cut-off frequency is , the total number of radar signal points is N, and the baseband effective bandwidth is , then the frequency step of the radar signal , the number of elements in the baseband frequency sequence , LO frequency step , the number of elements in the local oscillator frequency sequence It can be determined according to the following expression:

[0078]

[0079]

[0080]

[0081]

[0082] In the formula, is a constant less than 1, for example , that is, one third of the baseband effective bandwidth.

[0083] The elements of the baseband frequency series are , 2 , 3 … The elements of the local oscillator frequency series are , , … .

[0084] In some embodiments, the control module 130 may be connected to a DDS circuit to control the DDS circuit to perform frequency hopping and determine the current frequency of the baseband signal. The control module 130 is used to control the DDS circuit to generate a baseband signal corresponding to the first sequence element in the baseband frequency sequence when the current baseband signal frequency is the last sequence element of the baseband frequency sequence and the radar signal needs frequency hopping, and update the current local oscillator frequency according to the local oscillator frequency step length. In this way, the reliability of the stepped frequency radar signal can be improved.

[0085] Please combine Figure 4 Taking the local oscillator signal generating module 120 including two PLL circuits as an example, the control module 130 may configure the local oscillator frequency of the first PLL circuit to be , configure the local oscillator frequency of the second PLL circuit to The multiplexer 121 first selects the first PLL circuit so that the output terminal of the multiplexer 121 outputs The control module 130 can control the DDS circuit to generate a local oscillator signal with a frequency of , 2 , 3 ……n The baseband signal is up-converted by the first mixing module 140, and the frequencies of the radar signals are: , … .

[0086] The DDS circuit current output In the case of a baseband signal and frequency hopping is required, the control module 130 may update the current local oscillator frequency to , and accordingly select the second PLL circuit. And, control the DDS circuit to generate a frequency of The baseband signal of DDS circuit generates the frequency of , 2 , 3 ……n Thus, the frequency of the radar signal is up-converted by the first frequency mixing module 140, and the frequencies of the radar signal are: , … .

[0087] In addition, after the second PLL circuit is enabled, the control module 130 may configure the local oscillation frequency of the first PLL circuit to , to adjust the frequency of the local oscillation signal generated by the first PLL circuit.

[0088] The current output in the DDS circuit In the case of a baseband signal and frequency hopping is required, the control module 130 may update the current local oscillator frequency to , and accordingly select the first PLL circuit. Control the DDS circuit to generate a frequency of The baseband signal of DDS circuit generates the frequency of , 2 , 3 ……n Thus, the frequency of the radar signal is up-converted by the first frequency mixing module 140, and the frequencies of the radar signal are: , … .

[0089] In addition, after the first PLL circuit is enabled, the control module 130 may configure the local oscillation frequency of the second PLL circuit to , to adjust the frequency of the local oscillator signal generated by the second PLL circuit. And so on, until the current local oscillator frequency reaches And complete a complete radar signal transmission cycle.

[0090] In this way, the PLL circuit 122 can switch the frequency in advance through a ping-pong operation, and output the local oscillation signal alternately through the first PLL circuit and the second PLL circuit, thereby realizing the ping-pong output of the local oscillation signal. This process reduces the register configuration time and the phase-locked loop frequency calibration time required when a single phase-locked loop switches the frequency, thereby increasing the frequency switching speed. At the same time, the frequency of the baseband signal can also be changed through the DDS circuit to realize fast switching of the frequency.

[0091] At the same time, when the first PLL stably outputs the LO signal, the frequency of the baseband signal is changed by DDS to achieve fast switching of the frequency point. The same method is implemented when the second PLL stably outputs the LO signal, alternating in sequence. This process can achieve fast switching of the frequency point.

[0092] In some embodiments, the control module 130 is used to determine a first target local oscillator frequency from the local oscillator frequency series according to the configured local oscillator frequency when determining that the current local oscillator frequency is updated, and configure the local oscillator frequency of the target PLL circuit to be the first target local oscillator frequency. The target PLL circuit is the PLL circuit corresponding to the current local oscillator frequency before the update. In this way, the local oscillator frequency of the PLL circuit can be adjusted as quickly as possible to further improve the frequency switching speed of the radar signal.

[0093] In this embodiment, if the current local oscillator frequency is updated, it indicates that at least one PLL circuit is switched from a gated state to a non-gated state. In this case, the local oscillator frequency of the PLL circuit can be reconfigured so that the PLL circuit performs frequency adjustment in advance to further improve the frequency switching speed.

[0094] For example, in the above example, if the current LO frequency changes from Updated to , it indicates that the first PLL circuit switches from the selected state to the unselected state, and the local oscillator frequency is The local oscillator signal has been used in this radar signal transmission cycle, so the local oscillator frequency of the first PLL circuit can be reconfigured to If the current local oscillator frequency changes from Updated to , it indicates that the second PLL circuit switches from the selected state to the unselected state, and the local oscillator frequency is The local oscillator signal has been used in this radar signal transmission cycle, so the local oscillator frequency of the second PLL circuit can be reconfigured to .

[0095] In some embodiments, Figure 3 As shown, the stepped frequency radar system may further include a second frequency mixing module and an echo processing module. The second frequency mixing module refers to a module device for performing down-conversion processing on the echo signal, and the echo processing module refers to a module device for performing signal processing on the received echo signal.

[0096] It can be understood that the specific circuit structures of the second frequency mixing module and the echo processing module can be determined according to actual conditions, and this document does not impose specific restrictions on this. For ease of description, some embodiments of the present application take the echo processing module including an ADC (Analog-to-Digital Converter) as an example for explanation. Furthermore, the first frequency mixing module 140, the second frequency mixing module, the local oscillator signal generating module 120 and the ADC can all be implemented by a radio frequency chip.

[0097] The second frequency mixing module can be connected to the output end of the multiplexer 121, and is used to perform down-conversion processing on the received echo signal and the local oscillator signal output by the multiplexer 121, and obtain a first intermediate frequency signal. The echo processing module can be connected to the second frequency mixing module, and perform signal processing on the first intermediate frequency signal output by the second frequency mixing module to obtain a second intermediate frequency signal. The second intermediate frequency signal can be used for subsequent signal processing and analysis to realize functions such as radar speed measurement and distance measurement.

[0098] In some embodiments, Figure 5 As shown, the embodiment of the present application provides a method for determining system delay, comprising the following steps:

[0099] S502: Using the stepped frequency radar system of the above embodiment to transmit at least one group of radar signals.

[0100] The same group of radar signals includes multiple radar signals generated based on the same local oscillator frequency, and the signal frequencies of the same group of radar signals constitute a radar frequency sequence, which is an arithmetic sequence with a tolerance equal to the baseband frequency step length. That is, multiple stepped frequency radar signals generated based on the same local oscillator frequency belong to the same group of radar signals.

[0101] For example, in Figure 3-4 In the example shown, when the multiplexer selects the first PLL circuit so that the output terminal of the multiplexer outputs The control module can control the DDS circuit to generate the local oscillator signal with a frequency of , 2 , 3 ……n The baseband signal of the radar signal is: , … .

[0102] The DDS circuit current output If the baseband signal is needed and frequency hopping is required, the control module can update the current local oscillator frequency to , and the second PLL circuit is enabled. And, the DDS circuit is controlled to generate a frequency of The baseband signal of DDS circuit generates the frequency of , 2 , 3 ……n Baseband signal. In this way, through up-conversion, the frequency of the radar signal is: , … .

[0103] In this example, , … is the first set of radar signals, , … is the second set of radar signals, and so on.

[0104] S504: Receive at least one set of calibration echo signals; the calibration echo signals are obtained by reflection from a calibration object located at a preset distance, or the calibration echo signals are obtained by transmitting radar signals using a cable of a preset length.

[0105] It should be noted that the calibration echo signal is an echo of the radar signal emitted in step S502. In the present application, a calibration object can be placed in the space in advance, and the interval distance between the calibration object and the stepped frequency radar system is a preset distance. When the stepped frequency radar system transmits at least one set of radar signals to the calibration object according to step S502, the calibration object will reflect the radar signal and form a calibration echo signal. The stepped frequency radar signal can receive the calibration echo signal reflected by the calibration object.

[0106] Alternatively, the present application may use a cable to respectively connect the radar signal transmitting end and the echo signal receiving end of the step frequency radar system, and the length of the cable is a known preset length. After the step frequency radar system transmits at least one set of radar signals to the calibration object according to step S502, the radar signal may be transmitted to the echo signal receiving end of the step frequency radar system through the cable, and a calibration echo signal is formed and received by the step frequency radar system.

[0107] The group classification of the calibration echo signal is consistent with the group classification of the radar signal. In other words, the calibration echo signals corresponding to the same group of radar signals also belong to the same group, and the calibration echo signals corresponding to different groups of radar signals also belong to different groups.

[0108] In the above example, the transmission frequency is , … , , … After the radar signal , … The corresponding calibration echo signals belong to the same group. , … The corresponding calibration echo signals belong to the same group.

[0109] S506: Use the second frequency mixing module and the echo processing module of the stepped frequency radar system to process at least one set of calibration echo signals, and obtain at least one set of calibration intermediate frequency signals.

[0110] In this step, when each calibration echo signal is obtained, the second frequency mixing module and the echo processing module can process each calibration echo signal respectively to obtain each calibration intermediate frequency signal. The group classification of each calibration intermediate frequency signal is consistent with the group classification of the calibration echo signal. For relevant descriptions, please refer to the above descriptions of the group classification of the calibration echo signal and the radar signal, which will not be repeated in this article.

[0111] S508: Taking the position of the signal frequency of the radar signal in the corresponding radar frequency series as the independent variable and the phase characteristic of the calibration intermediate frequency signal as the dependent variable, data fitting is performed on each group of calibration intermediate frequency signals, and the system delay of the stepped frequency radar system is obtained based on the fitting results; wherein the system delay is used for data calibration.

[0112] In some examples, the stepped frequency radar system may include a signal processing module, and step S508 may be performed by the signal processing module.

[0113] Specifically, the baseband signal at the transmitter is , taking the first frequency point as an example, , t is time, j is an imaginary unit. The local oscillator signal at the transmitter is ,in , is a random initial phase. In this case, the radar signal obtained by up-converting the baseband signal and the local oscillator signal is The echo signal is , taking the echo processing module including ADC as an example, is the delay from transmitting radar signal to receiving by ADC.

[0114] After down-conversion by the second mixing module, the resulting down-converted signal is: In the ADC After data acquisition and secondary down-conversion, the intermediate frequency signal is , is the internal delay of the ADC system.

[0115] In collecting any group , 2 , 3 ……n The echo signal of the baseband signal is processed to obtain:

[0116]

[0117] After changes, we can get:

[0118]

[0119] From the above derivation, we know that: middle So is a linear equation of one variable, is the position of the signal frequency of the radar signal in the corresponding radar frequency series.

[0120] By measuring Transform n groups of data to obtain … The n groups of results are:

[0121]

[0122] It can be seen that the present application can use the position of the signal frequency of the radar signal in the corresponding radar frequency series as the independent variable, and use the phase characteristics of the calibration intermediate frequency signal as the dependent variable for data fitting, that is, use m as the independent variable and (include to ) is used as the dependent variable to fit the data, so that the system delay can be obtained based on the fitting results. .

[0123] In the system delay determination method provided in some embodiments of the present application, a group of calibration echo signals generated by multiple radar signals corresponding to a single local oscillator frequency can be received, and each group of calibration echo signals can be processed respectively by multi-point data fitting to calculate the system delay of the stepped frequency radar system. In this way, the system delay of the stepped frequency radar system can be determined simply and quickly.

[0124] In some embodiments, at least one set of radar signals is transmitted using a stepped frequency radar system, including:

[0125] Transmitted using a stepped frequency radar system A group of radar signals; among which, , is the total number of frequency hopping points of the stepped frequency radar system, is the number of baseband frequency hopping points of the stepped frequency radar system.

[0126] Taking the position of the signal frequency of the radar signal in the corresponding radar frequency series as the independent variable and the phase characteristics of the calibration intermediate frequency signal as the dependent variable, data fitting is performed on each group of calibration intermediate frequency signals, and the system delay of the stepped frequency radar system is obtained based on the fitting results, including:

[0127] The position of the radar signal frequency in the corresponding radar frequency series is used as the independent variable, and the phase characteristic of the calibration intermediate frequency signal is used as the dependent variable. The calibration intermediate frequency signal of the target group is fitted, and the system delay corresponding to the second target local oscillator frequency is obtained based on the fitting result of the target group; wherein the target group is For any group of intermediate frequency signals in the group calibration, the second target local oscillator frequency is the local oscillator frequency corresponding to the target group.

[0128] In this embodiment, a stepped frequency radar system may be used to transmit A group of radar signals, each group of radar signals may include n stepped frequency radar signals with different frequencies. , is the total number of frequency hopping points of the stepped frequency radar system. is the number of baseband frequency hopping points of the stepped frequency radar system, that is, the number of elements in the baseband frequency sequence. is the number of elements in the local oscillator frequency sequence, that is, the number of local oscillator frequencies that need to be experienced in a complete radar signal transmission cycle.

[0129] For each local oscillator frequency, n calibration intermediate frequency signals corresponding to the local oscillator frequency can be obtained, and the system delay corresponding to the local oscillator frequency can be obtained through data fitting, so as to perform segmented compensation according to the local oscillator frequency in the future and improve the accuracy of radar measurement.

[0130] Specifically, in the launch In the case of a group of radar signals, we can get A set of calibration echo signals can be used to obtain A group of calibrated intermediate frequency signals. For each group of calibration intermediate frequency signals, the present application uses m as the independent variable and the phase characteristics of the calibration intermediate frequency signal as the dependent variable, performs data fitting on the n calibration intermediate frequency signals of the group, and obtains the corresponding system delay based on the fitting results.

[0131] For example, when the first radar signal is , … , the second radar signal is , … When the above steps are used to process the first set of calibration intermediate frequency signals, Similarly, the above steps can be used to process the second set of calibration intermediate frequency signals and obtain The corresponding system delay.

[0132] In some embodiments, performing data fitting on the calibration intermediate frequency signal of the target group, and obtaining the system delay corresponding to the second target local oscillator frequency based on the fitting result of the target group, includes:

[0133] Performing linear fitting on each calibration intermediate frequency signal of the target group and obtaining the fitting slope;

[0134] Calculate the system delay corresponding to the second target LO frequency based on the following expression:

[0135]

[0136] In the formula, is the fitting slope; , is the frequency step of the radar signal; , R is the preset distance, C is the speed of light; is the system delay corresponding to the second target local oscillator frequency.

[0137] Specifically, it can be seen from the above derivation process that after linear fitting of a set of calibration intermediate frequency signals, the intercept of the first-order equation is , the slope is Since the calibration object is set at a preset distance, the preset distance is known, so Calculate the time difference from transmitting the radar signal to receiving the echo signal. , , When all the parameters are known, the system delay can be obtained by substituting the data into the above formula.

[0138] In this way, the calculation is simple and fast, which can further improve the efficiency of determining the system delay.

[0139] In some embodiments, Figure 6 As shown, the embodiment of the present application provides a radar ranging method, including:

[0140] S602: Using the stepped frequency radar system provided in the above embodiment to transmit Group radar signal;

[0141] S604: Receive the reflected signal from the object to be measured. Group ranging echo signal;

[0142] S606: Using the second frequency mixing module and the echo processing module of the stepped frequency radar system The ranging echo signal is processed and obtained Group ranging intermediate frequency signal;

[0143] S608: According to the system delay corresponding to each set of ranging intermediate frequency signals, The intermediate frequency signal of the group ranging is corrected and obtained A group of corrected intermediate frequency signals; wherein the system delay is determined based on the system delay determination method provided in the above embodiment;

[0144] S610: Based on The intermediate frequency signal is corrected to obtain the distance value of the object to be measured.

[0145] In this embodiment, when using the stepped frequency radar system for ranging, the stepped frequency radar system can be used to transmit A set of stepped frequency radar signals. The relevant description of the group radar signal can be found above, and this application will not repeat it here.

[0146] In a complete radar signal transmission cycle, the stepped frequency radar system can transmit N stepped frequency radar signals. When the radar signal reaches the location of the object to be measured, it will be reflected by the object to be measured to form a ranging echo signal. The stepped frequency radar system can receive The group of ranging echo signals is obtained based on this For the description of the ranging echo signal and the ranging intermediate frequency signal, please refer to the description of the calibration echo signal and the calibration intermediate frequency signal, which will not be repeated in this application.

[0147] For all ranging intermediate frequency signals, this application can be used according to , 2 , 3 ……n For each group of ranging intermediate frequency signals, the present application may determine the target system delay according to the local oscillator frequency corresponding to the group of ranging intermediate frequency signals, and calibrate the group of ranging intermediate frequency signals based on the target system delay to reduce or even eliminate the impact of system delay on the measurement results. For example, before correction, the phase characteristics of the ranging intermediate frequency signal may be:

[0148]

[0149] After correction, the phase characteristics of the corrected intermediate frequency signal can be:

[0150]

[0151] After the calibration is completed, this application can be In one example, an IFFT (inverse Fourier transform) calculation can be performed on each corrected intermediate frequency signal to obtain the time domain waveform of the distance information of the stepped frequency radar system, and finally transmitted to the personal computer through the network port.

[0152] In one example, the uncorrected frequency-amplitude plot can be Figure 7 As shown, based on Figure 7 The calculated distance-amplitude time domain diagram can be shown as Figure 8 After correction using this application, the frequency-amplitude diagram can be shown as Fig. 9 Based on Fig. 9The calculated distance-amplitude time domain diagram can be shown as Fig.10 shown.

[0153] In the radar ranging method provided in some embodiments of the present application, each group of ranging intermediate frequency signals can be corrected in sections according to the system delay corresponding to each group of ranging intermediate frequency signals, so as to compensate the initial phase of the baseband signal in sections, and perform ranging calculation based on the corrected intermediate frequency signal. Compared with the existing correction method, this scheme has the advantages of simple and fast correction, and can achieve accurate ranging. It can be seen that the present application can simplify the correction process and improve the efficiency of ranging calculation on the basis of ensuring the accuracy of the ranging result. In addition, in the process of receiving the echo signal, the receiving time can be flexibly selected, which has the advantage of high flexibility.

[0154] Finally, it should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not clearly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. Herein, "one", "one", "said", "the" and "it" may also include plural forms, unless the context clearly indicates another way. A plurality refers to at least two cases, such as 2, 3, 5 or 8, etc. "And / or" includes any and all combinations of the relevant listed items.

[0155] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can refer to each other.

[0156] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A stepped frequency radar system, characterized in that: include: A baseband signal generating module, used for generating a baseband signal; A local oscillator signal generating module, comprising a multiplexer and at least two PLL circuits, wherein the output end of each of the PLL circuits is connected to a plurality of input ends of the multiplexer in a one-to-one correspondence; the PLL circuit is used to generate a local oscillator signal according to a configured local oscillator frequency; A control module, connected to the control end of the multiplexer and the control end of each of the PLL circuits, respectively, for respectively configuring the local oscillator frequency of each of the PLL circuits according to the local oscillator frequency sequence; further for determining the current local oscillator frequency, and outputting a selection signal to the multiplexer based on the current local oscillator frequency, so that the multiplexer selects the PLL circuit corresponding to the current local oscillator frequency; wherein the local oscillator frequency sequence is an arithmetic progression with a tolerance equal to the local oscillator frequency step length, and the local oscillator frequencies configured for each of the PLL circuits are different from each other; The first frequency mixing module is connected to the baseband signal generating module and the output end of the multiplexer respectively, and is used to perform up-conversion processing on the baseband signal and the local oscillator signal output by the multiplexer to obtain a radar signal.

2. The system according to claim 1, characterized in that The baseband signal generation module comprises: The DDS circuit is connected to the first mixing module and is used to perform frequency hopping according to the baseband frequency sequence and sequentially generate baseband signals corresponding to each sequence element; wherein the baseband frequency sequence is an arithmetic sequence with a tolerance equal to the baseband frequency step length.

3. The system according to claim 2, characterized in that The baseband frequency step length is the frequency step length of the radar signal, and the number of sequence elements of the baseband frequency sequence is determined according to the baseband effective bandwidth of the stepped frequency radar system and the baseband frequency step length; The local oscillator frequency step is the product of the number of elements in the sequence and the baseband frequency step.

4. The system according to claim 2, characterized in that The control module is connected to the DDS circuit; The control module is used to control the DDS circuit to generate a baseband signal corresponding to the first sequence element in the baseband frequency sequence when the current baseband signal frequency is the last sequence element in the baseband frequency sequence and the radar signal needs to frequency hop, and to update the current local oscillator frequency according to the local oscillator frequency step size.

5. The system according to claim 4, characterized in that The control module is used to determine a first target local oscillator frequency from the local oscillator frequency series according to the configured local oscillator frequency when it is determined that the current local oscillator frequency is updated, and configure the local oscillator frequency of the target PLL circuit to the first target local oscillator frequency; wherein the target PLL circuit is the PLL circuit corresponding to the current local oscillator frequency before the update.

6. The system according to any one of claims 2 to 5, characterized in that: The stepped frequency radar system further comprises: a second frequency mixing module, connected to the output end of the multiplexer, for performing down-conversion processing on the received echo signal and the local oscillator signal output by the multiplexer, and obtaining a first intermediate frequency signal; The echo processing module is connected to the second mixing module and is used to perform signal processing on the first intermediate frequency signal to obtain a second intermediate frequency signal.

7. A method for determining system delay, characterized in that: The method comprises: At least one group of radar signals is transmitted using the stepped frequency radar system as claimed in claim 6; wherein the same group of radar signals includes a plurality of radar signals generated based on the same local oscillator frequency, and the signal frequencies of the same group of radar signals constitute a radar frequency sequence, and the radar frequency sequence is an arithmetic sequence with a tolerance equal to the baseband frequency step length; Receiving at least one set of calibration echo signals; the calibration echo signals are obtained by reflecting a calibration object located at a preset distance, or the calibration echo signals are obtained by transmitting the radar signal using a cable of a preset length; Using the second frequency mixing module and the echo processing module of the stepped frequency radar system to process the at least one set of calibration echo signals, and obtain at least one set of calibration intermediate frequency signals; Taking the position of the signal frequency of the radar signal in the corresponding radar frequency series as the independent variable and the phase characteristic of the calibration intermediate frequency signal as the dependent variable, data fitting is performed on each group of the calibration intermediate frequency signals, and the system delay of the stepped frequency radar system is obtained based on the fitting results; wherein the system delay is used for data calibration and the system delay is an absolute delay.

8. The method according to claim 7, characterized in that A stepped frequency radar system is used to transmit at least one set of radar signals, including: The stepped frequency radar system is used to transmit A group of radar signals; among which, , is the total number of frequency hopping points of the stepped frequency radar system, is the number of baseband frequency hopping points of the stepped frequency radar system; Taking the position of the signal frequency of the radar signal in the corresponding radar frequency series as the independent variable and the phase characteristic of the calibration intermediate frequency signal as the dependent variable, performing data fitting on each group of the calibration intermediate frequency signals, and obtaining the system delay of the stepped frequency radar system based on the fitting results, including: The position of the signal frequency of the radar signal in the corresponding radar frequency series is used as the independent variable, and the phase characteristic of the calibration intermediate frequency signal is used as the dependent variable. The calibration intermediate frequency signal of the target group is fitted with data, and the system delay corresponding to the second target local oscillator frequency is obtained based on the fitting result of the target group; wherein the target group is For any group of intermediate frequency signals in the group calibration, the second target local oscillator frequency is the local oscillator frequency corresponding to the target group.

9. The method according to claim 8, characterized in that The performing data fitting on the calibration intermediate frequency signal of the target group, and obtaining the system delay corresponding to the second target local oscillator frequency based on the fitting result of the target group, includes: Performing linear fitting on each calibration intermediate frequency signal of the target group and obtaining a fitting slope; The system delay corresponding to the second target local oscillator frequency is calculated based on the following expression: ； In the formula, is the fitting slope; , is the frequency step of the radar signal; , R is the preset distance, C is the speed of light; is the system delay corresponding to the second target local oscillator frequency.

10. A radar ranging method, characterized in that: The method comprises: The stepped frequency radar system according to claim 6 is used to transmit Group radar signal; Receive the reflected light from the object to be measured Group ranging echo signal; The second frequency mixing module and the echo processing module of the stepped frequency radar system are used to The ranging echo signal is processed and obtained Group ranging intermediate frequency signal; According to the system delay corresponding to each group of the ranging intermediate frequency signals, The ranging intermediate frequency signal is corrected and obtained A group of corrected intermediate frequency signals; wherein the system delay is determined based on the system delay determination method according to claim 8 or 9; Based on the The corrected intermediate frequency signal is formed to obtain the distance value of the object to be measured.

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