Method for avoiding third order intermodulation based on radar waveform generation

Abstract

The method for avoiding third-order intermodulation based on radar waveform generation of the application comprises the following steps: obtaining image test results under different radar parameters based on a standard radar test, adjusting the relationship of the different radar parameters by a frequency spectrum analyzer, determining the relationship between the pulse repetition frequency (PRF) and the frequency difference of different radar signals, and the radar parameters including the radar pulse repetition frequency and the frequency difference between different radar signals; suppressing the third-order intermodulation when the radar transmits and receives multiple signals; after suppressing the third-order intermodulation, sending the generated signal carrier frequency information to the radar radio frequency part, generating corresponding multiple signals and radiating. In a manner without reducing the signal-to-noise ratio, the influence of the third-order component is avoided, thereby improving the signal detection performance of the radar.

Description

Technical Field

[0001] This invention belongs to the technical field of radar systems, and in particular relates to a method for avoiding third-order intermodulation based on radar waveform generation. Background Technology

[0002] Due to the characteristics of nonlinear devices widely used in radar radio frequency systems, harmonics and intermodulation distortion will inevitably occur when radar signals of different frequencies are mixed, with third-order intermodulation being the most severe. Therefore, research on third-order intermodulation is unavoidable in modern radar technology research. Third-order and higher-order intermodulation components often fall outside the filter band in the spectrum, and in particular, they become a major factor in degrading radar signal quality in radars that transmit and receive multiple signals simultaneously.

[0003] In view of this, the present invention is hereby proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a method for avoiding third-order intermodulation based on radar waveform generation, aiming to improve the signal processing performance of radars that simultaneously transmit and receive multiple signals. The technical solution of this invention has many beneficial effects, as described below:

[0005] A method for avoiding third-order intermodulation based on radar waveform generation is provided, the method comprising:

[0006] Based on standardized radar tests, image test results under different radar parameters are obtained. The image test results are adjusted according to the relationship between the different radar parameters by the spectrum analyzer to determine the relationship between the pulse repetition frequency (PRF) and frequency difference between different radar signals. The radar parameters include the radar pulse repetition frequency and the frequency difference between different radar signals.

[0007] Third-order intermodulation suppression is applied to the radar during multi-channel signal transmission and reception.

[0008] After suppressing third-order intermodulation, the waveform is generated and the generated signal carrier frequency information is sent to the radar radio frequency section to generate corresponding multi-channel signals and radiate them.

[0009] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0010] This method effectively avoids third-order intermodulation (3D) interference. Compared to other filtering methods, it essentially masks the intermodulation components with the dominant frequency component, thus avoiding any loss in signal-to-noise ratio (SNR). It is simple to implement in engineering, requiring only algorithmic modifications in the radar software to mitigate the effects of 3D intermodulation. By avoiding the impact of 3D components without reducing the SNR, it improves the radar's signal detection performance and can be applied to radar systems with simultaneous multi-channel signal transmission and reception, reducing the impact of 3D intermodulation and enhancing radar signal detection capabilities. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 The third-order component slides across the frequency spectrum as the frequency difference changes;

[0013] Figure 2 The third-order intermodulation has deteriorated significantly;

[0014] Figure 3 Far-field plot of the distributed array after eliminating relative phase error;

[0015] Figure 4 The third-order components were not completely obscured in the three types of spectral lines;

[0016] Figure 5 The third-order component is annihilated in three types of spectral lines;

[0017] Figure 6 This is a flowchart illustrating the calculation method of the present invention. Detailed Implementation

[0018] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] like Figure 6 The method shown is for avoiding third-order intermodulation based on radar waveform generation. The method includes:

[0020] S101: Based on standardized radar tests, image test results under different radar parameters are obtained. The image test results are adjusted according to the relationship between different radar parameters using a spectrum analyzer to determine the relationship between the pulse repetition frequency (PRF) and frequency difference between different radar signals. Radar parameters include the radar pulse repetition frequency and the frequency difference between different radar signals. An example is given below.

[0021] The different signals include signal S1 and signal S2. The pulse repetition frequency of signal S1 is PRF1 and the carrier frequency is f1. The pulse repetition frequency of signal S2 is PRF2 and the carrier frequency is f2.

[0022] Adjust the parameters of the spectrum analyzer to determine the first mathematical relationship between the pulse repetition frequency PRF and the absolute value of the frequency difference between carrier frequencies f1 and f2 when the pulse repetition frequency PRF1 is equal to the pulse repetition frequency PRF2. Also, determine the second mathematical relationship between the pulse repetition frequency PRF1 and / or pulse repetition frequency PRF2 and the absolute value of the frequency difference between carrier frequencies f1 and f2 when the pulse repetition frequency PRF1 is not equal to the pulse repetition frequency PRF2.

[0023] The relationship between the pulse repetition frequency (PRF) and frequency difference for different radar signals is determined as follows:

[0024] When two signals have the same pulse repetition frequency (PRF), the frequency of the third-order component is expressed as:

[0025] 2f1-f2=f1+f1-f2|=f1+Δf, frequency difference Δf=|f1-f2|.

[0026] Determine the relationship between the pulse repetition frequency (PRF) and frequency difference for different radar signals, including:

[0027] When the pulse repetition frequencies of two signals are different, the spectral lines are arranged on the spectrum with two different pulse repetition frequencies (PRFs) as intervals.

[0028] The distance of the third-order component from the main spectral line within a single frequency gate is obtained from the frequency expression of the third-order component. This is the frequency difference between the two signals that generate third-order intermodulation. Specifically, the impulse repetition frequency (PRF) of each signal needs to be mathematically matched with the frequency difference.

[0029] The first mathematical relation is: Δf mn = N*PRF, where Δf mn The carrier frequency difference between each pair of signals is N, which represents any positive integer. PRF is the pulse repetition frequency, which is equal to the pulse repetition frequency PRF1 or PRF2.

[0030] The second mathematical relation is: Δf mn =N*PRF x, where Δf mn The carrier frequency difference between each pair of signals is N, where N represents any positive integer, and PRF is the frequency difference between each pair of signals. x A PRF representing any given signal.

[0031] S102: Performs third-order intermodulation suppression on the radar during multi-channel signal transmission and reception, specifically:

[0032] Definition: The effective signal received by the radar is the main signal. During the transmission and reception of multiple signals, third-order intermodulation will inevitably be generated. Third-order intermodulation is a type of secondary wave.

[0033] When the third-order intermodulation component coincides with the spectral line of the main signal, the third-order intermodulation component is submerged in the spectrum of the main signal, or the main signal is enhanced. In this scenario, the third-order intermodulation is considered to be avoided (the third-order intermodulation is superimposed on the main signal within the spectral line of the main signal, with the positions coinciding and the energy being superimposed). That is, the signal does not need to undergo unnecessary filtering processing of the third-order intermodulation at the receiving end.

[0034] When multiple input signals have the same PRF, in order to avoid third-order intermodulation, the frequency difference between each pair of them needs to satisfy the first mathematical relationship.

[0035] When multiple input signals have different frequency response factors (PRFs), to avoid third-order intermodulation, the frequency difference between each pair of input signals and the PRF must satisfy the second mathematical relationship, where PRF... x A PRF representing any signal, such as PRF1 or PRF2 or any other signal's PRF;

[0036] S103: After suppressing third-order intermodulation, the waveform is generated and the generated signal carrier frequency information is sent to the radar radio frequency section to generate corresponding multi-channel signals and radiate them, and then sent to the radar hardware front end.

[0037] The core objective of this invention is to determine the relationship between the pulse repetition frequency (PRF) and frequency difference between multiple radar signals, and to employ different strategies in each case to perform mathematical matching between PRE and frequency difference. Ultimately, this achieves the goal of avoiding third-order intermodulation through waveform generation without sacrificing signal quality, without requiring additional filtering of third-order intermodulation at the receiver, and with minimal hardware modifications required.

[0038] like Figure 1 As shown, when the carrier frequency of the signal is adjusted, the third-order component also moves regularly left and right in the spectrum. The interval between the spectral lines is PRF. It is not difficult to find that the quality of the third-order intermodulation is related to the relationship between PRF and the frequency difference of the input signal.

[0039] Figure 2This is a schematic diagram of severe third-order intermodulation degradation. Similar to the PRF, it shows the output spectra of three signals with frequencies of 5100KHz, 5000KHz and 5035KHz respectively. The frequency differences between each pair do not all meet the waveform generation rules under the same PRF, and the third-order intermodulation has a serious impact.

[0040] Figure 3 Third-order intermodulation is avoided, similar to PRF, in Figure 3 In this system, the frequencies of the three input signals are 5400KHz, 5900KHz and 6000KHz, respectively, and the PRF is set to 100KHz. The waveform generation rules under the same PRF are satisfied between each pair of the three signals, and the third-order intermodulation is effectively avoided.

[0041] Figure 4 The third-order components were not completely buried in the three types of spectral lines. The signal frequencies shown were 5000KHz, 5025KHz and 5120KHz, respectively, and the PRF was set to 10KHz, 25KHz and 40KHz, respectively. The waveform generation rules under different PRFs were not met in pairs of the three signals, and the third-order intermodulation had a serious impact.

[0042] Figure 5 The third-order components are annihilated in three types of spectral lines. Figure 5 In this system, the frequencies of the three input signals are 5000KHz, 5025KHz and 5150KHz, respectively, and the PRFs are set to 10KHz, 25KHz and 40KHz, respectively. The waveform generation rules of the three signals under different PRFs are satisfied between each pair of the three signals, and the third-order intermodulation is effectively avoided.

[0043] In conclusion,

[0044] 1. Appendix Figure 1 This explains that the essence of this method is to "hide" the signal of the third-order component within the main signal spectrum. Essentially, it avoids the influence of the third-order component rather than eliminating it, and therefore does not result in a loss of signal-to-noise ratio.

[0045] 2. In the radar main control system software, add relevant algorithms for assigning carrier frequency values.

[0046] 3. When there are different PRFs, the PRF of any signal can be selected as PRFx. In actual design, it can be agreed to be the minimum value, and any positive integer N can be set as a random number within a certain range, which can simultaneously increase the radar anti-jamming performance.

[0047] 4. After the frequency difference is determined, the main control system sends control commands to the radio frequency system to generate signals and perform down-conversion processing during signal reception.

[0048] As can be seen from the above steps, the method of the present invention can improve the signal detection performance of radar by adjusting the generation of waveforms without reducing the signal-to-noise ratio and avoiding the influence of third-order components.

[0049] The product provided by this invention has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the invention claims.

Claims

1. A method for avoiding third-order intermodulation based on radar waveform generation, characterized in that, The method includes: Image test results under different radar parameters were obtained based on standardized radar tests. These results were adjusted using a spectrum analyzer to determine the relationship between the different radar parameters and the frequency difference between different radar signals. The radar parameters include the radar pulse repetition frequency and the frequency difference between different radar signals. Different signals include signal S1 and signal S2, where signal S1 has a pulse repetition frequency of PRF1 and a carrier frequency of f1, and signal S2 has a pulse repetition frequency of PRF2 and a carrier frequency of f2. The parameters of the spectrum analyzer are adjusted so that when the pulse repetition frequency PRF1 equals the pulse repetition frequency PRF2, a first mathematical relationship is determined between the pulse repetition frequency PRF1 and the absolute value of the frequency difference between carrier frequencies f1 and f2; and a second mathematical relationship is determined when the pulse repetition frequency PRF1 is not arbitrarily equal to the pulse repetition frequency PRF2, between the pulse repetition frequency PRF1 and / or the pulse repetition frequency PRF2 and the absolute value of the frequency difference between carrier frequencies f1 and f2. Third-order intermodulation suppression is applied to the radar during multi-channel signal transmission and reception. After suppressing third-order intermodulation, the waveform is generated and the generated signal carrier frequency information is sent to the radar radio frequency section to generate corresponding multi-channel signals and radiate them. The first mathematical relationship is: In the formula, The carrier frequency difference between each pair of signals is N, which represents any positive integer. PRF is the pulse repetition frequency, which is equal to the pulse repetition frequency PRF1 or the pulse repetition frequency PRF2. The second mathematical relation is: In the formula, The carrier frequency difference between each pair of signals is N, where N represents any positive integer. A PRF representing any given signal.

2. The method according to claim 1, characterized in that, Determine the relationship between the pulse repetition frequency (PRF) and frequency difference for different radar signals, including: When two signals have the same pulse repetition frequency (PRF), the frequency of the third-order component is expressed as: Frequency difference .

3. The method according to claim 2, characterized in that, Determine the relationship between the pulse repetition frequency (PRF) and frequency difference for different radar signals, including: When the pulse repetition frequencies of two signals are different, the spectral lines are arranged on the spectrum with two different pulse repetition frequencies (PRF) as intervals. The distance of the third-order component from the main spectrum within a single frequency gate is obtained from the frequency expression of the third-order component. This is the frequency difference between the two signals that generate third-order intermodulation. The pulse repetition frequency (PRF) of each signal needs to be mathematically matched with the frequency difference.

4. The method according to claim 3, characterized in that, The third-order intermodulation suppression for radar during multi-channel signal transmission and reception includes: The effective signal received by the radar is used as the main signal; When the third-order intermodulation component coincides with the spectral line position of the main signal in the spectrum, the third-order intermodulation component is submerged in the spectrum of the main signal, or the main signal is enhanced, and the third-order intermodulation is avoided, that is, the signal does not need to perform unnecessary filtering processing on the third-order intermodulation at the receiving end. When multiple input signals have the same PRF, in order to avoid third-order intermodulation, the frequency difference between each pair of signals needs to satisfy the first mathematical relationship. When multiple input signals have different PRFs, in order to avoid third-order intermodulation, the frequency difference between each pair and the PRF need to satisfy the second mathematical relationship.

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