Method and system for generating v-type frequency modulation signal

Abstract

The application discloses a V-type frequency modulation signal generation method and system, comprising: obtaining a discrete model of the V-type frequency modulation signal, obtaining a frequency increment and a frequency initial parameter through a first-order difference relationship between a frequency and a phase of the discrete signal; taking the frequency increment, the frequency initial parameter and a constant term as positive frequency modulation digital control parameters, constructing a linear increasing sequence based on the frequency increment, obtaining an instantaneous frequency value at different moments by sequentially superimposing the frequency initial parameter, superimposing the constant term on the instantaneous frequency value at different moments to obtain a phase sequence of a positive frequency modulation slope; performing a negation processing on the positive frequency modulation digital control parameters to obtain a phase sequence of a negative frequency modulation slope; and converting the phase sequence into amplitude data according to a sine waveform to generate the V-type frequency modulation signal. The application can greatly reduce the operation amount of control parameters and the data transmission amount in the signal generation process by optimizing parameter configuration logic and simplifying operation, significantly improves the calculation efficiency and reduces the consumption of calculation resources.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of signal processing, in particular to a V-type frequency modulation signal generation method and system. BACKGROUND

[0002] The V-type frequency modulation signal is proposed as an improved linear frequency modulation pulse signal variant. The V-type frequency modulation signal retains the good detection performance of the linear frequency modulation pulse signal and significantly improves the time-frequency resolution of the signal, which makes the V-type frequency modulation signal exhibit obvious advantages in multi-target resolution and complex environment adaptability.

[0003] At present, the generation method of the V-type frequency modulation signal needs to independently configure the control parameters of the two segments of the signal respectively, and the control parameters are issued twice to realize the switching control of the starting frequency and the frequency modulation rate of the V-type frequency modulation signal, which leads to a doubling of the data transmission amount and increases the consumption of computing resources. SUMMARY

[0004] In order to solve the problems of the prior art, the technical scheme adopted by the present application is as follows:

[0005] The present application provides a V-type frequency modulation signal generation method, which comprises the following steps:

[0006] Obtain the configuration parameters of the V-type frequency modulation signal, and construct a time-domain expression model of the V-type frequency modulation signal based on the configuration parameters;

[0007] Discretize the time-domain expression model to obtain a discrete model of the V-type frequency modulation signal, wherein the discrete model comprises a phase model of a discrete signal, and the phase model of the discrete signal is expressed as the sum of the following three terms: a constant term, a first-order term having a linear relationship with the discrete time, and a second-order term having a quadratic relationship with the discrete time;

[0008] Convert the phase model of the discrete signal to a frequency calculation model of the discrete signal by using the first-order difference relationship between the frequency and the phase of the discrete signal, obtain a frequency increment and a frequency initial parameter, wherein the frequency increment is twice the coefficient of the second-order term of the phase model, and the frequency initial parameter is the sum of the coefficient of the first-order term and the coefficient of the second-order term of the phase model;

[0009] Take the frequency increment, the frequency initial parameter and the constant term as positive frequency modulation digital control parameters of the V-type frequency modulation signal, and obtain a phase sequence of the positive frequency modulation slope according to the following phase calculation method: construct a linearly increasing sequence based on the frequency increment, obtain the instantaneous frequency values at different time points by sequentially superimposing the frequency initial parameter, superimpose the constant term on the instantaneous frequency values at different time points to obtain the phase sequence;

[0010] Invert the positive frequency modulation digital control parameters to obtain negative frequency modulation digital control parameters, and obtain a phase sequence of the negative frequency modulation slope according to the phase calculation method.

[0011] According to the sine waveform, the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are converted into amplitude data to generate the V-shaped frequency modulation signal.

[0012] In summary, the method for generating a V-shaped frequency modulation signal provided in the present application is based on a time-domain expression model of the V-shaped frequency modulation signal. The positive frequency modulation digital control parameter of the V-shaped frequency modulation signal is calculated. The phase sequence of the positive frequency modulation slope of the V-shaped frequency modulation signal is obtained by calculating the instantaneous frequency value at different times. The positive frequency modulation digital control parameter is inverted based on the signal characteristics of the V-shaped frequency modulation signal to obtain the negative frequency modulation digital control parameter of the V-shaped frequency modulation signal. The phase sequence of the negative frequency modulation slope of the V-shaped frequency modulation signal is further calculated and obtained. Thus, the V-shaped frequency modulation signal is generated without the need for secondary calculation and digital control parameter issuance. The amount of parameter configuration calculation and the amount of data transmission are greatly reduced. The calculation efficiency is significantly improved. Moreover, by optimizing the parameter configuration logic and simplifying the calculation method, the calculation resource consumption is effectively reduced while the generation efficiency of the V-shaped frequency modulation signal is improved.

[0013] Further, the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are calculated in a multi-path parallel processing manner.

[0014] Further, the discretization processing of the time-domain expression model includes:

[0015] The system sampling rate is set. The time-domain expression model is discretized according to the system sampling rate to obtain the phase model of the discrete signal of the system.

[0016] The working clock is used as a single-path sampling rate. The system sampling rate in the phase discrete model of the system is converted according to the single-path sampling rate to obtain the phase model of the discrete signal of the single path.

[0017] Further, the phase model of the discrete signal of the single path is represented by the following formula:

[0018] ;

[0019]

[0020] In the formula, T represents the pulse width of the V-shaped frequency modulation signal, m represents the discrete time, B / 2 represents the bandwidth of the V-shaped frequency modulation signal; u represents the positive and negative frequency modulation slope of the V-shaped frequency modulation signal, and u=B / T; M represents the number of processing paths, represents the system sampling rate, represents the single-path sampling rate.

[0021] Further, the configuration parameters of the V-shaped frequency modulation signal include:

[0022] The signal envelope, the center frequency of the V-shaped frequency modulation signal, the pulse width of the V-shaped frequency modulation signal, the bandwidth of the V-shaped frequency modulation signal, the initial phase of the V-shaped frequency modulation signal, and the positive and negative frequency modulation slopes of the V-shaped frequency modulation signal.

[0023] Further, the phase model of the discrete signal is converted into a frequency calculation model of the discrete signal by a first-order differential relationship between the frequency and the phase of the discrete signal, including:

[0024] Based on the phase model of the discrete signal, the phase difference between the two adjacent time points is calculated to obtain the frequency calculation model of the discrete signal.

[0025] Further, the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are converted into amplitude data by a function lookup table, wherein the function lookup table stores a mapping relationship between the phase and the amplitude of the sine wave in the interval of π / 2, and the corresponding amplitude of different phases in [0, 2π] is output according to the positive and negative mirror symmetry of the sine function when the table is looked up.

[0026] In a second aspect, the application also provides a V-shaped frequency modulation signal generation system, the generation system is based on an FPGA module, the FPGA module includes a PS end and a PL end, the PS end is configured to perform floating point operations on the frequency increment, the frequency initial parameter and the constant term based on the V-shaped frequency modulation signal generation method provided by the application, the PL end is configured to generate the positive frequency modulation digital control parameter and the negative frequency modulation digital control parameter based on the frequency increment, the frequency initial parameter and the constant term generated by the PS end, and generate the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope through an adder.

[0027] Further, the PS end sends the frequency increment, the frequency initial parameter and the constant term to the PL end through an AXI bus.

[0028] Further, the FPGA module further includes a storage module, the storage module is used to store a function lookup table, and the function lookup table stores a mapping relationship between the phase and the amplitude of the sine wave in the interval of π / 2. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 A step flowchart of the V-shaped frequency modulation signal generation method provided by an embodiment of the application is provided.

[0030] Figure 2 A step flowchart of the V-shaped frequency modulation signal generation method provided by an embodiment of the application is provided.

[0031] Figure 3 A schematic diagram of the adder used in the V-shaped frequency modulation signal generation system provided by an embodiment of the application is provided.

[0032] Figure 4A step flow chart for generating a V-type frequency modulation signal based on an FPGA module is provided in a V-type frequency modulation signal generation system according to an embodiment of the present application.

[0033] Figure 5 A time-frequency characteristic diagram of a V-type frequency modulation signal generated in a test experiment is provided according to an embodiment of the present application.

[0034] Figure 6 A frequency spectrum characteristic diagram of a V-type frequency modulation signal generated in a test experiment is provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0035] The present application will be described in detail below with reference to the specific embodiments shown in the drawings, but these embodiments do not limit the present application, and the structural, method, or functional changes made by those of ordinary skill in the art based on these embodiments are included in the protection scope of the present application.

[0036] In order to solve the problems of the prior art, an embodiment of the present application provides a V-type frequency modulation signal generation method, as shown in Figure 1 The generation method comprises the following steps:

[0037] In step S11, configuration parameters of the V-type frequency modulation signal are obtained, and a time-domain expression model of the V-type frequency modulation signal is constructed based on the configuration parameters.

[0038] In step S12, the time-domain expression model is discretized to obtain a discrete model of the V-type frequency modulation signal, and the discrete model comprises a phase model of a discrete signal, and the phase model of the discrete signal is expressed as the sum of the following three terms: a constant term, a first-order term in linear relationship with discrete time, and a second-order term in quadratic relationship with discrete time.

[0039] In step S13, the phase model of the discrete signal is converted into a frequency calculation model of the discrete signal through a first-order difference relationship between the frequency and the phase of the discrete signal, a frequency increment and a frequency initial parameter are obtained, the frequency increment is twice the coefficient of the second-order term of the phase model, and the frequency initial parameter is the sum of the coefficient of the first-order term and the coefficient of the second-order term of the phase model.

[0040] In step S14, the frequency increment, the frequency initial parameter, and the constant term are taken as positive frequency modulation digital control parameters of the V-type frequency modulation signal, and a phase sequence of a positive frequency modulation slope is obtained according to the following phase calculation method: a linearly increasing sequence is constructed based on the frequency increment, the instantaneous frequency values at different times are obtained by sequentially superimposing the frequency initial parameter, and the constant term is superimposed on the instantaneous frequency values at different times to obtain the phase sequence.

[0041] In step S15, the positive frequency modulation digital control parameters are inverted to obtain negative frequency modulation digital control parameters, and a phase sequence of a negative frequency modulation slope is obtained according to the phase calculation method.

[0042] Step S16, according to the sine waveform, the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are converted into amplitude data to generate a V-type frequency modulation signal.

[0043] Specifically, configuration parameters covering signal characteristics of the V-type frequency modulation signal are acquired, and the configuration parameters include: a signal envelope, a center frequency of the V-type frequency modulation signal, a pulse width of the V-type frequency modulation signal, a bandwidth of the V-type frequency modulation signal, an initial phase of the V-type frequency modulation signal, and positive and negative frequency modulation slopes of the V-type frequency modulation signal. A time-domain expression model of the V-type frequency modulation signal is constructed based on the configuration parameters, and the time-domain expression model is composed of two parts: one part is a signal envelope of the V-type frequency modulation signal, which is used to describe the amplitude change of the V-type frequency modulation signal; the other part is a phase oscillation part of the V-type frequency modulation signal, and the mathematical expression is a function containing a linear term and a quadratic term. In an embodiment, the signal envelope is a rectangular window function, and the signal envelope amplitude is constant when the V-type frequency modulation signal is within the pulse width, and the signal envelope is zero when the V-type frequency modulation signal is outside the pulse width.

[0044] The time-domain expression model can reflect the signal envelope and phase oscillation characteristics of the V-type frequency modulation signal, and in an embodiment, the time-domain expression model of the V-type frequency modulation signal can be expressed as follows:

[0045] ;

[0046] In the formula, f(t) represents the signal envelope, and ; ; f(t) represents the center frequency of the V-type frequency modulation signal, f(t) represents the pulse width of the V-type frequency modulation signal, f(t) represents the bandwidth of the V-type frequency modulation signal, f(t) represents the initial phase of the V-type frequency modulation signal; f(t) represents the positive and negative frequency modulation slopes of the V-type frequency modulation signal, and .

[0047] The time-domain expression model of the V-type frequency modulation signal is discretized to convert the continuous time-domain expression model into a discrete model that can be processed by a digital system, and the discrete model of the V-type frequency modulation signal includes a discrete signal phase model, which is expressed as the sum of the following three terms:

[0048] The first term is a constant, representing the initial phase shift of the V-mode frequency modulated signal. This constant remains unchanged throughout the signal generation process and does not change with discrete time. The second term is a linear term that has a linear relationship with discrete time, reflecting the linear phase change trend of the V-mode frequency modulated signal over time. The third term is a quadratic term that has a quadratic relationship with discrete time, proportional to the square of the discrete time. This quadratic term reflects the phase change caused by linear frequency modulation. Based on these three terms, the phase model can completely describe the phase state of the discrete signal at each discrete time point, transforming the continuous phase change law into a discrete phase expression that can be computed by the digital system.

[0049] In one embodiment, the discrete model of the V-mode frequency modulated signal can be expressed by the following formula:

[0050] ;

[0051] In the formula, Indicates the signal envelope, and ; This indicates the sampling rate.

[0052] Furthermore, the phase model of a discrete signal can be expressed by the following formula:

[0053] ;

[0054] In the formula, , where m represents discrete time and M represents the number of processing paths.

[0055] Removing 2π from the phase model of a discrete signal, based on the lookup table principle, the phase model of a discrete signal can be expressed by the following formula: ;

[0056] In the formula, T represents the pulse width of the V-mode frequency modulation signal, and B / 2 represents the bandwidth of the V-mode frequency modulation signal. The initial phase of the V-mode frequency modulation signal is represented by ; u represents the positive and negative frequency modulation slope of the V-mode frequency modulation signal, and u = B / T; m represents the discrete time, and M represents the number of processing paths; This indicates the system sampling rate.

[0057] According to the phase model of discrete signals, there is a first-order difference relationship between frequency and phase. In the discrete case, frequency is represented by the difference in phase between adjacent time points. The instantaneous frequency at a certain discrete time point can be obtained by calculating the phase difference between that time point and the previous time point. Based on the first-order difference relationship between frequency and phase, the phase model of discrete signals is converted into a frequency calculation model. In one embodiment, the frequency calculation model can be expressed by the following formula:

[0058] ;

[0059] In the formula, f represents the frequency.

[0060] The frequency increment is twice the coefficient of the quadratic term in the phase model, and the frequency increment can reflect the step amount of the linear change of the frequency with time; the frequency initial parameter is the sum of the coefficient of the linear term and the coefficient of the quadratic term in the phase model, and the frequency initial parameter represents the frequency value of the V-shaped frequency modulation signal at the starting moment. Through the frequency increment and the frequency initial parameter, the instantaneous frequency sequence of the V-shaped frequency modulation signal can be obtained through iterative addition, thereby reducing the occupation of logical operation resources and reducing the calculation delay.

[0061] Further, based on the obtained constant term, frequency increment and frequency initial parameter, the three parameters are determined as positive frequency modulation digital control parameters of the V-shaped frequency modulation signal, and the positive frequency modulation digital control parameters determine the frequency and phase change characteristics of the V-shaped frequency modulation signal in the positive frequency modulation stage. Based on the positive frequency modulation digital control parameters, the phase sequence of the positive frequency modulation slope is obtained according to the following three-step phase calculation method:

[0062] The first step is to construct a linearly increasing sequence based on the frequency increment, and the frequency increment reflects the rate of change of the frequency with time. By continuously accumulating the frequency increment, a series of frequency change values that increase linearly with discrete time can be obtained, and the linearly increasing sequence can reflect the trend of gradually increasing frequency in the positive frequency modulation process.

[0063] The second step is to sequentially superimpose the frequency initial parameter and the above linearly increasing sequence, and the frequency initial parameter is used as the frequency reference at the initial moment. The instantaneous frequency value at each discrete time point is obtained by adding the frequency reference value to the frequency increment accumulation value at the corresponding moment, so that the instantaneous frequency values at different moments in the positive frequency modulation stage can be obtained.

[0064] The third step is to superimpose the instantaneous frequency values at different moments with the constant term, and the constant term plays a role of phase compensation or phase offset. Through the cumulative superimposed results, the phase sequence of the positive frequency modulation slope is finally obtained.

[0065] After obtaining the phase sequence of the positive frequency modulation slope, the positive frequency modulation digital control parameters are inverted by using the characteristics that the V-shaped frequency modulation signal is composed of two segments of positive frequency modulation and negative frequency modulation, and the signs of the frequency modulation slopes of the two segments are opposite. The sign of the positive frequency modulation digital control parameter is changed to make the trend of frequency change from increasing to decreasing, and the negative frequency modulation digital control parameter is obtained.

[0066] After obtaining the negative frequency modulation digital control parameter, the same phase calculation method as that for calculating the phase sequence of the positive frequency modulation slope is used to obtain the phase sequence of the negative frequency modulation slope. A linear decreasing sequence is constructed based on the frequency increment of the negative frequency modulation (due to the parameter taking the opposite, the original increasing sequence becomes a decreasing sequence), and then the frequency initial parameter of the negative frequency modulation is sequentially superimposed with the linear decreasing sequence to obtain the instantaneous frequency values of the V-shaped frequency modulation signal at different times. Finally, the instantaneous frequency values at different times are superimposed with a constant term and accumulated to obtain the phase sequence of the negative frequency modulation slope. Through the above parameter reuse calculation method, the calculation process of the positive frequency modulation slope and the negative frequency modulation slope is simplified, repeated parameter configuration and operation are avoided, and the continuity of the positive and negative frequency modulation signals in phase is ensured, thereby providing a consistent and continuous phase basis for subsequent waveform synthesis.

[0067] Further, after obtaining the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope, the amplitude of the sinusoidal signal periodically changes with the phase based on the waveform function table. Different phase values correspond to amplitude points on the sinusoidal waveform. According to the mapping relationship between the phase value and the sinusoidal amplitude, the phase sequence is converted into an amplitude sequence. The phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are matched in the waveform function table, and the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are converted into amplitude data. The amplitude data of the positive frequency modulation slope and the amplitude data of the negative frequency modulation slope are spliced in time sequence, and the amplitude data of the V-shaped frequency modulation signal is obtained in combination with the signal envelope, thereby generating the V-shaped frequency modulation signal.

[0068] According to the above description, the method for generating a V-shaped frequency modulation signal provided by the embodiments of the present application calculates the positive frequency modulation digital control parameter of the V-shaped frequency modulation signal based on the time domain expression model of the V-shaped frequency modulation signal, obtains the phase sequence of the positive frequency modulation slope of the V-shaped frequency modulation signal by calculating the instantaneous frequency values at different times, performs a negation process on the positive frequency modulation digital control parameter based on the signal characteristics of the V-shaped frequency modulation signal to obtain the negative frequency modulation digital control parameter of the V-shaped frequency modulation signal, further calculates the phase sequence of the negative frequency modulation slope of the V-shaped frequency modulation signal, and thereby generates the V-shaped frequency modulation signal without the need for secondary calculation and digital control parameter issuing, greatly reduces the operation amount and data transmission amount of parameter configuration, significantly improves the calculation efficiency, and effectively improves the signal quality while improving the generation efficiency of the V-shaped frequency modulation signal and reducing the consumption of hardware resources, thereby stably generating the V-shaped frequency modulation signal meeting the requirements of high-precision application scenarios such as radars.

[0069] As an optional implementation manner, in step S11, the configuration parameters of the V-shaped frequency modulation signal include: a signal envelope, a center frequency of the V-shaped frequency modulation signal, a pulse width of the V-shaped frequency modulation signal, a bandwidth of the V-shaped frequency modulation signal, an initial phase of the V-shaped frequency modulation signal, and positive and negative frequency modulation slopes of the V-shaped frequency modulation signal.

[0070] The signal envelope determines the time distribution range of the V-type frequency modulation signal. In the embodiment of the present application, the signal envelope adopts a rectangular window to ensure the stability of the signal within the pulse width. The center frequency determines the position of the V-type frequency modulation signal in the frequency spectrum. The pulse width defines the time length of the V-type frequency modulation signal. The bandwidth of the V-type frequency modulation signal reflects the range of the frequency variation of the signal, which is used to determine the frequency resolution of the signal. The initial phase of the V-type frequency modulation signal is used to determine the phase state of the starting moment of the signal. The positive and negative frequency modulation slopes of the V-type frequency modulation signal determine the variation trend that the frequency of the signal first increases linearly and then decreases linearly, thereby completely describing the variation law of the V-type frequency modulation signal in the time domain.

[0071] As an optional implementation manner, as shown in FIG. 12, the step of discretizing the time-domain expression model in step S12 further includes the following steps. Figure 2

[0072] In step S121, a system sampling rate is set, and the time-domain expression model is discretized according to the system sampling rate to obtain a phase model of a discrete signal of the system.

[0073] In step S122, a working clock is taken as a single-path sampling rate, and the system sampling rate in the phase discrete model of the system is converted according to the single-path sampling rate to obtain a phase model of a discrete signal of a single path.

[0074] Specifically, the system sampling rate is set based on the bandwidth of the V-type frequency modulation signal, the frequency variation range and the number of processing paths, and the time-domain expression model is discretized according to the system sampling rate. The discrete time points are extracted at the time intervals set by the system sampling rate on the continuous time axis, and the continuous time variable is converted into a sequence of discrete sampling time points. For the phase part in the time-domain expression model, the corresponding phase value is calculated according to the discrete time points, so as to convert the continuous phase function into a series of discrete phase data points. The above phase data points collectively constitute the phase model of the discrete signal of the system.

[0075] The single-path processing path takes the working clock as the reference clock signal, and takes the working clock as the single-path sampling rate, so as to avoid data loss or processing errors caused by clock mismatch. In an embodiment, the single-path sampling rate can be expressed as:

[0076] ;

[0077] In the formula, fclk represents the single-path sampling rate, fs represents the system sampling rate, and M represents the number of processing paths.

[0078] ​​​After the single-path sampling rate is determined, the system sampling rate in the phase discrete model of the system is converted based on the single-path sampling rate, to obtain a phase model of the discrete signal of the single path, so that the single-path processing path can efficiently and accurately calculate and process the phase sequence under the control of the working clock, providing a discretization basis for generation of the positive and negative frequency modulation slope phase sequences, and providing a unified timing reference for coordinated work of the processing paths in the multi-path parallel processing. In an embodiment, the phase model of the discrete signal of the single path can be expressed as follows:

[0079] ;

[0080] In the formula, T represents the pulse width of the V-type frequency modulation signal, B / 2 represents the bandwidth of the V-type frequency modulation signal, represents the initial phase of the V-type frequency modulation signal; u represents the positive and negative frequency modulation slope of the V-type frequency modulation signal, and u = B / T; m represents the discrete time, and M represents the number of processing paths. represents the system sampling rate.

[0081] Further, the phase model of the discrete signal is merged and simplified, and three new coefficients a, b and c are used to replace the quadratic term coefficient, the linear term coefficient and the constant term, respectively, in which the coefficient a is used to replace the quadratic term coefficient, the coefficient b is used to replace the linear term coefficient, and the coefficient c is used to replace the constant term.

[0082] As an optional line-of-sight mode, when the initial phase is zero, the phase model of the discrete signal of the single path can be simplified as:

[0083] ;

[0084] In the formula, a is the quadratic term coefficient, b is the linear term coefficient, c is the constant term, and m represents the discrete time.

[0085] Further, when the discrete time , the coefficients a, b and c can be expressed by the formula as follows:

[0086] ;

[0087] In the formula, B / 2 represents the bandwidth of the V-type frequency modulation signal; u represents the positive and negative frequency modulation slope of the V-type frequency modulation signal, and u = B / T; and M represents the number of processing paths.

[0088] When the discrete time , the coefficients a, b and c can be expressed by the formula as follows:

[0089] ;

[0090] In the formula, B / 2 represents the bandwidth of the V-type frequency modulation signal; u represents the positive and negative frequency modulation slopes of the V-type frequency modulation signal, and u = B / T; M represents the number of processing paths.

[0091] According to the expression formula of the coefficients a, b, and c, it can be obtained that, in the case that the initial phase is zero, the value of the quadratic term coefficient a is determined by the bandwidth and the pulse width, the sign of the quadratic term coefficient a determines the direction of the frequency modulation slope, and the values of the coefficients a, b, and c are opposite to each other between two discrete time periods, and the alternation of the frequency phase of the V-type frequency modulation signal is configured by the coefficients a, b, and c.

[0092] As an optional implementation, in step S13, the phase model of the discrete signal is converted into the frequency calculation model of the discrete signal by the first-order differential relationship between the frequency and the phase of the discrete signal, including: based on the phase model of the discrete signal, calculating the phase difference between two adjacent time points to obtain the frequency calculation model of the discrete signal.

[0093] Specifically, by using the relationship between the frequency and the phase in the discrete domain, the frequency is the rate of change of the phase with respect to time, which is represented as the phase difference value between adjacent time points in the discrete case. The phase model of the discrete signal describes the phase state of the discrete signal at each discrete time point. When calculating the phase difference between two adjacent time points, two consecutive discrete time points, for example, the nth time point and the (n-1)th time point, are selected and substituted into the phase model of the discrete signal to obtain the phase values corresponding to the two time points. The phase difference between the two adjacent time points is obtained by differentiating the phase values of the adjacent time points. Through the phase difference calculation, the phase model originally composed of three terms is converted into an expression containing only the frequency increment and the frequency initial parameter. The expression is the frequency calculation model of the discrete signal.

[0094] In an embodiment, the frequency calculation model of the discrete signal can be represented by the following formula:

[0095] ;

[0096] In the formula, m represents the discrete time.

[0097] The frequency increment and the frequency initial parameter are obtained by the frequency calculation model of the discrete signal. Based on the frequency increment, the frequency initial parameter, and the constant term, the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are calculated. As an optional implementation, in steps S14 and S15, the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are calculated in a multi-path parallel processing manner.

[0098] ​Specifically, in the calculation process, independent processing paths are respectively set for the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope, the processing paths are started at the same time and run in parallel, one processing path is used for processing the calculation of the phase sequence of the positive frequency modulation slope, and the other processing path is used for processing the calculation of the phase sequence of the negative frequency modulation slope. The two processing paths simultaneously receive corresponding control parameters, and then synchronously perform operations such as construction of a linearly increasing (or decreasing) sequence, superposition of instantaneous frequencies, and accumulation of phases.

[0099] Through the multi-path parallel processing mode, the overall calculation time is greatly shortened, the efficiency and real-time performance of signal generation are improved, and the hardware utilization rate is also improved. Moreover, since the calculation of the phase sequences of the positive and negative frequency modulation slopes is completed synchronously, strict alignment in time can be ensured, which lays a foundation for subsequent conversion into waveform data through a function lookup table and synthesis of a complete V-shaped frequency modulation signal, and avoids the influence of time difference caused by serial processing on the continuity and accuracy of the signal.

[0100] As an optional implementation, in step S16, the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are converted into amplitude data through a function lookup table. The function lookup table stores the mapping relationship between the phase and amplitude of a sine waveform in the interval of π / 2, and the corresponding amplitude of different phases in [0, 2π] is output according to the positive and negative mirror symmetry of the sine function when the table is looked up.

[0101] Specifically, in step S16, the phase sequences of the positive and negative frequency modulation slopes are converted into amplitude data through a function lookup table. For the storage design of the function lookup table, based on the positive and negative mirror symmetry of the sine function, the mapping relationship between the phase and amplitude in the interval of π / 2 (i.e., 1 / 4 period of the sine wave) is selected. The sine function has a strict symmetry rule in [0, 2π]: for example, the waveform in the interval of 0~π / 2 is mirror symmetric to the waveform in the interval of π / 2~π, the waveform in the interval of 0~π / 2 is positive and negative symmetric to the waveform in the interval of π~3π / 2, and the waveform in the interval of π / 2~π is positive and negative symmetric to the waveform in the interval of 3π / 2~2π. Based on the positive and negative mirror symmetry of the sine function, it is not necessary to store the mapping data of the complete period, but the amplitude of any phase in [0, 2π] can be derived through the stored information in the interval of π / 2 through symmetry logic, so that the storage resource consumption is reduced to 1 / 4 of the complete period storage, and the resource occupation is significantly reduced.

[0102] In the specific table lookup conversion process, the accurate conversion of the amplitude is realized through “phase quadrant judgment + symmetry logic processing”. Each phase value in the input phase sequence is subjected to quadrant attribution judgment: according to the numerical range of the phase value, it is divided into a certain quadrant in [0, π / 2] (first quadrant), [π / 2, π] (second quadrant), [π, 3π / 2] (third quadrant), and [3π / 2, 2π] (fourth quadrant).

[0103] For the first quadrant, directly address the function lookup table with the phase value in the interval of 0~π / 2, and output the corresponding amplitude; for the second quadrant, use the mirror symmetry to inversely address the lookup table with the relative address corresponding to "π - phase value", and output the amplitude symmetric to the first quadrant; for the third quadrant, use the positive and negative symmetry to first forwardly address the lookup table with the relative address of the phase value in the interval of π~3π / 2, and then take the negative of the output amplitude; for the fourth quadrant, combine the mirror and positive and negative symmetries to inversely address the lookup table with the relative address corresponding to "2π - phase value", and then take the negative of the output amplitude. Through the above address processing and sign control, the amplitude corresponding to any phase in [0, 2π] is accurately output from the lookup table storing the data in the interval of 0~π / 2, the resource consumption is reduced, and the processing speed is improved.

[0104] According to the above description, the method for generating a V-type frequency modulation signal provided by the embodiments of the present application is based on a time domain expression model of the V-type frequency modulation signal, calculates positive frequency modulation digital control parameters of the V-type frequency modulation signal, obtains a phase sequence of a positive frequency modulation slope of the V-type frequency modulation signal by calculating instantaneous frequency values at different times, and performs an inversion process on the positive frequency modulation digital control parameters based on signal characteristics of the V-type frequency modulation signal to obtain negative frequency modulation digital control parameters of the V-type frequency modulation signal, and further calculates and obtains a phase sequence of a negative frequency modulation slope of the V-type frequency modulation signal, thereby generating the V-type frequency modulation signal, without the need for secondary calculation and issuance of digital control parameters, greatly reducing the operation amount and data transmission amount of parameter configuration, significantly improving the calculation efficiency, and through optimization of parameter configuration logic and simplification of the operation mode, improving the generation efficiency of the V-type frequency modulation signal and reducing the consumption of hardware resources while effectively improving the signal quality, and the V-type frequency modulation signal meeting the needs of high-precision application scenarios such as radars can be stably generated.

[0105] In a second aspect, based on the same inventive concept, the embodiments of the present application also provide a generation system of a V-type frequency modulation signal, which is based on an FPGA module, the FPGA module includes a PS end and a PL end, the PS end is configured to perform floating point operations of frequency increments, frequency initial parameters and constant terms based on the method for generating a V-type frequency modulation signal described above, the PL end is configured to generate positive frequency modulation digital control parameters and negative frequency modulation digital control parameters based on the frequency increments, the frequency initial parameters and the constant terms generated by the PS end, and generate a phase sequence of a positive frequency modulation slope and a phase sequence of a negative frequency modulation slope through an adder.

[0106] Specifically, the PS end (Processing System) and the PL end (Programmable Logic) realize efficient interaction of data and instructions through a high-speed interconnection channel inside the FPGA module. The PS end is configured to complete the floating-point operation of the frequency increment, the frequency initial parameter and the constant term of the V-type frequency modulation signal as described above. The PS end receives the V-type frequency modulation signal configuration parameters (such as signal bandwidth, pulse width, center frequency, etc.) issued by the upper computer, and calculates the frequency increment, the frequency initial parameter and the constant term based on the preset V-type signal generation logic through floating-point operation. The PS end transmits the calculated frequency increment, the frequency initial parameter and the constant term to the PL end. The PL end is configured to generate positive frequency modulation digital control parameters based on the above parameters, and to obtain negative frequency modulation digital control parameters by performing negation processing on the positive frequency modulation digital control parameters based on the characteristic that the two frequency modulation frequencies of the V-type frequency modulation signal are opposite numbers.

[0107] Based on the positive frequency modulation digital control parameters and the negative frequency modulation digital control parameters, the PL end generates a phase sequence of the positive frequency modulation slope through an adder according to the positive frequency modulation digital control parameters: a linearly increasing instantaneous frequency sequence is constructed with the frequency increment as the step, and then a continuous positive frequency modulation phase sequence is obtained by accumulating the instantaneous frequency and superimposing the constant term; similarly, a phase sequence of the negative frequency modulation slope is generated through the same calculation logic according to the negative frequency modulation digital control parameters. Further, based on the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope, the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are converted into amplitude data according to the sine waveform to generate the V-type frequency modulation signal.

[0108] According to the above description, the V-type frequency modulation signal generation system provided by the embodiments of the present application generates the V-type frequency modulation signal by respectively configuring the PS end and the PL end on the FPGA module, without the need for secondary calculation and issuance of digital control parameters, greatly reducing the operation amount and data transmission amount of parameter configuration, and reducing the consumption of hardware resources.

[0109] As an optional implementation manner, the PS end sends the frequency increment, the frequency initial parameter and the constant term to the PL end through the AXI bus, and utilizes the high-performance communication advantage of the AXI bus in the FPGA heterogeneous architecture to provide an efficient and reliable hardware basis for the parameter interaction between the PS end and the PL end in the V-type frequency modulation signal generation system, so as to adapt to the strict requirements of radar and other high-precision scenarios on the real-time performance and accuracy of data transmission.

[0110] As an optional implementation, the FPGA module further comprises a storage module, and the storage module is configured to store a function lookup table, and the function lookup table stores a mapping relationship between phases and amplitudes of a sine wave in a π / 2 interval. The function lookup table is designed based on positive-negative mirror symmetry of a sine function, and without storing mapping data of a complete period, the amplitude of an arbitrary phase in [0, 2π] can be derived through symmetric logic based on the stored information in the π / 2 interval, so that the storage resource consumption is reduced to 1 / 4 of the complete period storage, and resource occupation is significantly reduced.

[0111] As an optional implementation, as shown in Figure 3 the phase output calculated by the adder is input to a DDS (Direct Digital Frequency Synthesis) module, the DDS module outputs real part data and imaginary part data, and based on the data output by the DDS module, a complete V-type frequency modulation signal is composed through a modulator. Time division multiplexing technology is used between the adder and the DDS module, and parallel output is realized through staggered clock access, thereby reducing repeated occupation of storage resources.

[0112] The FPGA module determines the frequency modulation rate switching time through a pulse width timer, and switches the linear frequency modulation phase at the time when the timer counts to half of the pulse width, thereby completing the switching of the frequency modulation rate of the V-type frequency modulation signal. The pulse width timer is used in the frequency modulation rate switching control module, and is configured to monitor the signal generation time in real time, and the timing formula is as follows:

[0113] ;

[0114] In the formula, T is a global clock period of the FPGA module.

[0115] In the positive frequency modulation phase, the phase sequence of the positive frequency modulation slope is generated through calculation; when t=T / 2 (half of the pulse width) in the pulse width timer, the frequency modulation rate switching signal is triggered, and the discrete frequency value is changed, and the phase sequence of the negative frequency modulation slope is generated through calculation.

[0116] Further, in an embodiment, the FPGA module is internally provided with 8-channel DACs (Digital Analog Converters), and the synchronization accuracy between the multiple DACs is high, so as to facilitate multi-channel and phase-coherent high-performance signal generation, and to facilitate maintaining phase continuity and avoiding phase jump caused by transmission delay.

[0117] In actual application, the steps of generating the V-type frequency modulation signal based on the FPGA module are as follows Figure 4 ​As shown, the number of parallel paths of the FPGA and the frequency of the DAC are determined according to the required V-type frequency modulation signal; the host computer configures the required pulse width, frequency increment, center frequency and other parameters and sends them to the PS end; the PS end performs floating point calculation to generate corresponding parameters, a pulse width counter monitors timing, triggers a frequency switching signal, the PS sends parameters, the PL side performs parallel calculation and gradually adds frequencies and phases through an adder; the FPGA module generates addresses in the corresponding function lookup table after adding parameters in parallel in each path; after matching in the waveform function table, the signal is output, and the V-type frequency modulation signal is output through the multi-path signal parallel-serial conversion of the DAC.

[0118] To further illustrate the V-type frequency modulation signal generation method provided by the embodiments of the present application, experimental tests are performed below to verify the effectiveness of the generation method. In the experiment, the clock frequency The time-frequency characteristics of the generated V-type frequency modulation signal are as shown in Figure 5 The spectral characteristics are as shown in Figure 6 The parameters of the V-type frequency modulation signal are: pulse width T = 5 μs, bandwidth B = 500 MHz. The test results show that the generated V-type frequency modulation signal has excellent time-frequency focusing characteristics.

[0119] It should be noted that the FPGA implementation scheme of the conventional V-type frequency modulation signal usually depends on the configuration of all parameters (including the initial frequency, the frequency modulation slope and the initial phase) of the positive and negative frequency modulation two sections of signals respectively, and requires real-time execution of a large number of multiplication and square operations in the FPGA to accurately generate frequency and phase control words. This direct calculation implementation path not only consumes a large number of valuable special DSP multiplier resources, but also significantly increases the use amount of general lookup table (LUT) and register (Register) due to the complex operation logic and multi-stage pipeline structure, which greatly limits the expansion capability of the system in a multi-channel scenario.

[0120] The present application innovatively constructs a continuous adder chain. Through the ingenious reconstruction of the algorithm level, the complex square operation is converted into continuous addition operation, thereby completely avoiding the dependence on the multiplier at the hardware level. The test data powerfully verify the excellent performance of the scheme: on the same process and scale of the FPGA chip, the V-type frequency modulation signal generation unit as the core of the present application only consumes 1,627 LUTs. In sharp contrast, a general linear frequency modulation signal generation module with a function equivalent to the traditional multiplier structure has a LUT consumption of 3,751.

[0121] This comparison shows that the scheme reduces the logic resource consumption by more than 56% on the premise of achieving the same frequency modulation function. This order of magnitude optimization of resource utilization not only greatly reduces the hardware cost and power consumption, but also is crucial for the subsequent system integration and multi-channel parallel expansion in the fields of radar and communication.

[0122] It can be understood that the word "exemplary" used herein means "serving as an example, instance, or illustration." Any implementation described as "exemplary" is not necessarily preferred or advantageous over other implementations and / or does not exclude other features of the application. It should be understood that certain features of the application described in the context of separate embodiments can also be provided in combination, and vice versa. Conversely, various features of the application described in the context of a single embodiment can also be provided separately or in any appropriate combination, or as part of any other described embodiment of the application.

[0123] In the description of the application, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" herein is only a description of the relationship between the associated objects, which means that there can be three relationships, for example, A and / or B, which can mean: A exists alone, A and B exist together, and B exists alone. In addition, "at least one" means one or more, and "multiple" means two or more. "First", "second", and the like do not limit the quantity and execution order, and "first", "second", and the like do not necessarily mean different.

[0124] The above disclosure is only the preferred embodiment of the application, and is not intended to limit the scope of the application. Those skilled in the art can understand that changes, modifications, substitutions, combinations, simplifications, etc. without departing from the spirit and scope of the application and the appended claims, are equivalent replacement methods still within the scope of the application.

Claims

1. A method of generating a VFM signal, characterized by, The generating method comprises the following steps: obtaining configuration parameters of the V-type frequency modulation signal, and constructing a time-domain expression model of the V-type frequency modulation signal based on the configuration parameters; discretizing the time-domain expression model to obtain a discrete model of the V-type frequency modulation signal, wherein the discrete model comprises a phase model of a discrete signal, and the phase model of the discrete signal is expressed as a sum of three terms: a constant term, a linear term having a linear relationship with a discrete time, and a quadratic term having a quadratic relationship with the discrete time; converting the phase model of the discrete signal into a frequency calculation model of the discrete signal by using a first-order differential relationship between a frequency and a phase of the discrete signal, to obtain a frequency increment and a frequency initial parameter, wherein the frequency increment is twice a coefficient of the quadratic term of the phase model, and the frequency initial parameter is a sum of a coefficient of the linear term and the coefficient of the quadratic term of the phase model; taking the frequency increment, the frequency initial parameter, and the constant term as positive frequency modulation digital control parameters of the V-type frequency modulation signal, and obtaining a phase sequence of a positive frequency modulation slope according to a phase calculation method as follows: constructing a linearly increasing sequence based on the frequency increment, sequentially superimposing the frequency initial parameter to obtain an instantaneous frequency value at different time points, superimposing the constant term on the instantaneous frequency value at the different time points to obtain a phase sequence; inverting the positive frequency modulation digital control parameters to obtain negative frequency modulation digital control parameters, and obtaining a phase sequence of a negative frequency modulation slope according to the phase calculation method; converting the phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope into amplitude data according to a sinusoidal waveform, and generating the V-type frequency modulation signal.

2. The method of claim 1, wherein, The phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are calculated in a multi-channel parallel processing mode.

3. The method of claim 2, wherein, The discretizing the time-domain expression model comprises: setting a system sampling rate, and discretizing the time-domain expression model according to the system sampling rate to obtain a phase model of a discrete signal of the system; taking a working clock as a single-channel sampling rate, and converting the system sampling rate in the phase discrete model of the system according to the single-channel sampling rate to obtain a phase model of a discrete signal of a single channel.

4. The V-type frequency modulation signal generating method according to claim 3, wherein the phase model of the discrete signal of the single channel is expressed by the following formula: ； In the formula, T represents the pulse width of the V-type frequency modulation signal, m represents the discrete time, B / 2 represents the bandwidth of the V-type frequency modulation signal; u represents the positive and negative frequency modulation slope of the V-type frequency modulation signal, and u=B / T; M represents the number of processing paths, represents the system sampling rate, represents the single-path sampling rate.

5. The method of claim 1, wherein, the configuration parameters of the V-type frequency modulation signal comprise: a signal envelope, a center frequency of the V-type frequency modulation signal, a pulse width of the V-type frequency modulation signal, a bandwidth of the V-type frequency modulation signal, an initial phase of the V-type frequency modulation signal, and positive and negative frequency modulation slopes of the V-type frequency modulation signal.

6. The method of claim 1, wherein, The converting the phase model of the discrete signal into the frequency calculation model of the discrete signal comprises: calculating a phase difference between two adjacent time points based on the phase model of the discrete signal to obtain the frequency calculation model of the discrete signal.

7. The method of claim 1, wherein, The phase sequence of the positive frequency modulation slope and the phase sequence of the negative frequency modulation slope are converted into amplitude data through a function lookup table, wherein the function lookup table stores a mapping relationship between phases and amplitudes of a sine waveform in a π / 2 interval, and corresponding amplitudes of different phases in [0, 2π] are output according to positive-negative mirror symmetry of a sine function during the lookup table.

8. A system for generating a VFM signal, characterized by The generation system is based on an FPGA module, the FPGA module includes a PS end and a PL end, the PS end is configured to perform floating point operation on the frequency increment, the frequency initial parameter and the constant term based on the method for generating the V-type frequency modulation signal according to any one of claims 1 to 4, the PL end is configured to generate positive frequency modulation digital control parameters and negative frequency modulation digital control parameters based on the frequency increment, the frequency initial parameter and the constant term generated by the PS end, and generate a phase sequence of a positive frequency modulation slope and a phase sequence of a negative frequency modulation slope through an adder.

9. The system for generating V-type frequency modulation signal according to claim 8, wherein, The PS end sends the frequency increment, the frequency initial parameter and the constant term to the PL end through an AXI bus.

10. The system for generating V-type frequency modulation signal according to claim 8, wherein, The FPGA module further includes a storage module, and the storage module is used to store a function lookup table, and the function lookup table stores a mapping relationship between phases and amplitudes of a sine waveform in a π / 2 interval.

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