Simple step frequency sub-pulse phase difference calculation method based on DSP (Digital Signal Processor)

Abstract

The invention relates to a DSP-based step frequency sub-pulse phase difference simple calculation method, and belongs to the field of frequency spectrum synthesis. The method comprises the following steps: acquiring two adjacent step frequency sub-pulses received by a step frequency system radar; extracting a frequency overlapping part of the two sub-pulses; performing difference calculation and amplitude multiplication on phases of discrete points of the frequency overlapping part of the two sub-pulses to obtain an expression of a result sub-pulse of each discrete point; obtaining a mean value of a real part and an imaginary part of discrete points of the frequency overlapping part; and calculating the average value of discrete point phases of the frequency overlapping part, wherein the phase is the phase difference of the two sub-pulses. The step is simple and easy to execute, two steps of operation of firstly filling zero at a sub-pulse frequency coincidence position and converting from a frequency domain to a time domain are omitted, and calculation is directly carried out in the frequency domain; the occupied DSP memory is small, zero padding is not needed, and the program running time is short.

Description

Technical Field

[0001] The invention belongs to the field of spectrum synthesis, and in particular relates to a simple calculation method for stepped frequency sub-pulse phase difference based on DSP. Background Art

[0002] The stepped frequency signal is a sub-pulse form that exchanges time for bandwidth. The radar transmits a group of narrow pulses with linear frequency jumps, and achieves high range resolution by synthesizing a large bandwidth. The traditional method of synthesizing high-resolution distance using stepped frequency sub-pulses is to treat the stepped frequency sub-pulses as a group of discretely transmitted point frequencies, which can be obtained through IFFT. However, its main problem is that the step size cannot be too large, otherwise it is easy to generate false targets. This requirement seriously limits its scope of application in engineering, because a large step size can reduce the number of stepping steps and increase the data rate. The spectrum synthesis method can splice the spectra of discretely transmitted stepped frequency sub-pulses in the frequency domain to synthesize a large bandwidth. Unlike traditional processing methods, the spectrum synthesis method will not have the problem of generating false targets when the step size is large, and the synthesis effect is better.

[0003] However, during spectrum synthesis, the phases of the two sub-pulses at the same frequency are not completely consistent, that is, there is a fixed phase difference. Therefore, the phase of one of the sub-pulses is often used as a reference to calculate the fixed phase difference between the other sub-pulse and the reference sub-pulse, and then perform phase compensation to compensate it to the phase difference consistent with the reference sub-pulse at the same frequency before spectrum synthesis can be performed. The current common method is to cut out the overlapping spectrum of the two sub-pulses to perform IFFT, and obtain the time domain signal. Each discrete point of the time domain signal contains information such as amplitude and phase. The difference between the phases of the two time domain signals is calculated, and then the mean is calculated. Finally, the phase of the mean is calculated to achieve the operation of calculating the phase difference between the two stepped frequency sub-pulses.

[0004] However, since the DSP library function requires that the sub-pulse length must meet the power of 2 requirement when using the FFT and IFFT built-in functions, it is necessary to fill the overlapping part of the two sub-pulses with zeros when calculating the phase difference; secondly, the two time domain signals obtained after the transformation also need to allocate memory; finally, through formula analysis, the fixed phase difference in the time domain signal is also fixed in the frequency domain.

[0005] Based on the above situation, the frequency overlapping part of two stepped frequency sub-pulses is used to directly calculate the phase difference during DSP programming, thereby realizing a simple calculation method for the stepped frequency sub-pulse phase difference based on DSP. Summary of the invention

[0006] 1. Technical issues to be resolved

[0007] The technical problem to be solved by the present invention is how to provide a simple calculation method for the phase difference of stepped frequency sub-pulses based on DSP to solve the problems of zero padding and memory allocation during spectrum synthesis of stepped frequency sub-pulses.

[0008] (II) Technical solution

[0009] In order to solve the above technical problems, the present invention proposes

[0010] (III) Beneficial effects

[0011] The present invention proposes a simple calculation method for the phase difference of stepped frequency sub-pulses based on DSP. The present invention has the following beneficial effects: the steps are simple and easy to execute, and the two operations of first filling zeros at the overlapping parts of the sub-pulse frequencies and converting from the frequency domain to the time domain are omitted, and the calculation is directly performed in the frequency domain; less DSP memory is occupied, and no zero filling is required, so this part of the memory is not required. On the other hand, no time domain sub-pulses need to be generated, which can further save DSP memory; the program running time is short, which is also due to the saving of two steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of the spectrum of two adjacent stepped frequency sub-pulses of the present invention;

[0013] Figure 2 It is a schematic diagram of spectrum synthesis of stepped frequency sub-pulses of the present invention;

[0014] Figure 3 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0015] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0016] The present invention proposes a simple calculation method for the phase difference of stepped frequency sub-pulses based on DSP. The method can be used in DSP programming to realize the operation of simply and quickly calculating the phase difference between stepped frequency sub-pulses when performing spectrum synthesis of large bandwidth without occupying redundant memory.

[0017] Based on the above analysis, the present invention proposes a simple calculation method for the phase difference of stepped frequency sub-pulses based on DSP. This method calculates the difference between the phases of each discrete point of the frequency overlapping part of two stepped frequency sub-pulses, then calculates the mean, and finally calculates the phase of the mean to obtain the phase difference between the two sub-pulses.

[0018] The present invention discloses a simple calculation method for the phase difference of stepped frequency sub-pulses based on DSP, which can be used for DSP programming to realize the operation of simply and quickly calculating the phase difference between stepped frequency sub-pulses when performing spectrum synthesis of large bandwidth without occupying redundant memory. The present invention solves the problems of cumbersome calculation steps and occupying redundant memory when using DSP programming to realize time domain phase difference calculation. The present invention first obtains two adjacent stepped frequency sub-pulses received by a stepped frequency system radar, then extracts the frequency overlapping part of the two sub-pulses, and then calculates the difference between the phases of discrete points where the two sub-pulses have the same frequency, then calculates the mean, and finally calculates the phase of the mean to obtain the phase difference of the stepped frequency sub-pulses.

[0019] The technical solution to solve the problem of the present invention is:

[0020] First, two adjacent stepped-frequency sub-pulses received by the stepped-frequency radar are obtained, and then the frequency overlapping part of the two sub-pulses is extracted. Secondly, the phase difference of the discrete points where the two sub-pulses have the same frequency is calculated, and then the mean is calculated. Finally, the phase of the calculated mean is the phase difference between the two adjacent stepped-frequency sub-pulses.

[0021] The present invention implements the steps as follows:

[0022] S1, obtaining two adjacent stepped frequency sub-pulses received by a stepped frequency radar;

[0023] S2, extracting the frequency overlap of two sub-pulses;

[0024] S3, calculating the difference between the phases of the discrete points of the overlapping part of the two sub-pulse frequencies, multiplying the amplitudes, and obtaining the expression of the result sub-pulse at each discrete point;

[0025] S4, obtaining the mean of the real part and the imaginary part of the discrete points of the frequency overlap part;

[0026] S5. Calculate the average phase of the discrete points of the frequency overlapping part, which is the phase difference between the two sub-pulses.

[0027] Embodiment 1:

[0028] Figure 1 Schematic diagram of the spectrum of two adjacent stepped frequency sub-pulses Sig1 and Sig2. The specific implementation steps of the method proposed in the present invention are as follows:

[0029] (1) Obtain two adjacent stepped-frequency sub-pulses received by the stepped-frequency radar.

[0030] like Figure 1 As shown, f c1 and f c2 are the center frequencies of sub-pulses Sig1 and Sig2, B spaceis the step bandwidth between two adjacent sub-pulses, that is, the step amount, and B is the distribution bandwidth of each sub-pulse.

[0031] (2) extracting the frequency overlap of the two sub-pulses;

[0032] like Figure 1 As shown, the shaded area of ​​the spectrum distribution is the frequency overlap of the two sub-pulses, which needs to be extracted, so the left and right boundaries of the shaded areas of the two sub-pulses need to be clearly defined.

[0033] The left boundary frequency value of Sig1 is

[0034] f Left1 =f c1 +B space -B / 2

[0035] The right boundary frequency value of Sig1 is

[0036] f Right1 =f c1 +B / 2

[0037] The left boundary frequency value of Sig2 is

[0038] f Left2 =f c2 -B / 2

[0039] The right boundary frequency value of Sig2 is

[0040] f Right2 =f c2 -B space +B / 2

[0041] (3) The phase difference of the discrete points of the overlapping part of the two sub-pulses is calculated, and the amplitude is multiplied to obtain the expression of the result sub-pulse at each discrete point.

[0042] The specific calculation process is:

[0043] S31, conjugate the frequency overlapped part extracted from one of the sub-pulses. It should be noted that when the phase of Sig1 is used as the reference phase, Sig1 is conjugated, and then Sig2 is phase compensated; when the phase of Sig2 is used as the reference phase, Sig2 is conjugated, and then Sig1 is phase compensated. The specific implementation steps of the present invention are only described with Sig1 as the reference phase.

[0044] The sub-pulse exists in the form of complex numbers, according to the Euler formula e jφ =cosφ+j sinφ It can be seen that taking the conjugate of Sig1 means taking its phase negative.

[0045]

[0046] S32, multiply the conjugated result by the frequency overlap part extracted by Sig2 to obtain the result sub-pulse. The calculation process of each discrete point of the result sub-pulse can be expressed as:

[0047]

[0048] Among them A 1 , A 2 , A represent the amplitudes of Sig1 discrete point, Sig2 discrete point, and result sub-pulse discrete point respectively. The phase of the result sub-pulse discrete point is the phase difference between the two sub-pulses. The theoretically obtained result is that the phase of each discrete point of the sub-pulse is Only the amplitude is different, but due to the presence of noise in engineering applications, the phase of each discrete point is Random error.

[0049] (4) Obtain the mean of the real and imaginary parts of the discrete points in the frequency overlapping part.

[0050] The real parts of the discrete points obtained in the previous step are summed and averaged to get the mean of the real parts, and the imaginary parts are summed and averaged to get the mean of the imaginary parts. This step is mainly to eliminate the random errors caused by noise.

[0051] (5) Calculate the mean phase of the discrete points in the frequency overlapping part.

[0052] The phase is the atan value of the mean of the imaginary part and the mean of the real part, and the calculation process is:

[0053]

[0054] This phase is the phase difference between the two sub-pulses Sig2 and Sig1. After calculating the phase difference between Sig2 and Sig1, the phase compensation of Sig2 can be realized, so as to extract the spectrum for synthesis. When performing spectrum synthesis, the frequency domain range of each sub-pulse is generally intercepted as the center frequency f c ±B space / 2, such as Figure 2 As shown, it is a schematic diagram of spectrum synthesis using stepped frequency sub-pulses.

[0055] Embodiment 2:

[0056] The present invention proposes a simple calculation method for the phase difference of step-frequency sub-pulses based on DSP. The method can be used for DSP programming to realize the operation of simply and quickly calculating the phase difference between step-frequency sub-pulses when performing spectrum synthesis of large bandwidth without occupying redundant memory. The method calculates the difference of the phase of each discrete point of the frequency overlap part of two step-frequency sub-pulses, then calculates the mean, and finally calculates the phase of the mean to obtain the phase difference of the two sub-pulses. Its characteristics are: 1) The steps are simple and easy to execute, because the two steps of first filling the overlapping part of the sub-pulse frequency with zero and then converting from the frequency domain to the time domain are omitted, but the calculation is performed directly in the frequency domain, so the operation steps are simplified; 2) It occupies less DSP memory, the sub-pulse does not need to be filled with zero, so there is no need to allocate memory to store the value 0, on the other hand, no time domain sub-pulses need to be generated, so there is no need to define new variables, which can also further save DSP memory; 3) The program running time is short, which is also due to saving two steps.

[0057] The beneficial effects of the present invention are as follows: the steps are simple and easy to execute, and the two operations of first filling zeros at the overlapping parts of the sub-pulse frequencies and converting from the frequency domain to the time domain are omitted, and calculations are performed directly in the frequency domain; less DSP memory is occupied, and no zero filling is required, so this part of the memory is not required. On the other hand, no time domain sub-pulses need to be generated, which can further save DSP memory; the program running time is short, which is also due to the saving of two steps.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A simple calculation method for step-frequency sub-pulse phase difference based on DSP, characterized in that: The method comprises the following steps: S1, obtaining two adjacent stepped frequency sub-pulses received by a stepped frequency radar; S2, extracting the frequency overlap of two sub-pulses; S3, calculating the difference between the phases of the discrete points of the overlapping part of the two sub-pulse frequencies, multiplying the amplitudes, and obtaining the expression of the result sub-pulse at each discrete point; S4, obtaining the mean of the real part and the imaginary part of the discrete points of the frequency overlap part; S5. Calculate the average phase of the discrete points of the frequency overlapping part, which is the phase difference between the two sub-pulses.

2. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 1, characterized in that: The S1 includes: c1 and f c2 are the center frequencies of two adjacent stepped frequency sub-pulses Sig1 and Sig2, respectively, and B space is the step bandwidth between two adjacent sub-pulses, that is, the step amount, and B is the distribution bandwidth of each sub-pulse.

3. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 2, characterized in that: S2 includes: the left and right boundaries of the frequency overlap part of the two sub-pulses are: The left boundary frequency value of Sig1 is f Left1 =f c1 +B space -B / 2 The right boundary frequency value of Sig1 is f Right1 =f c1 +B / 2 The left boundary frequency value of Sig2 is f Left2 =f c2 -B / 2 The right boundary frequency value of Sig2 is f Right2 =f c2 -B space +B / 2.

4. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 3 is characterized in that: The S3 includes: S31, conjugating the frequency overlapping part extracted from one of the sub-pulses; S32, performing a dot product between the conjugated result and the frequency overlapping portion extracted from the second sub-pulse to obtain a result sub-pulse.

5. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 4 is characterized in that: In S31, when the phase of Sig1 is used as the reference phase, Sig1 takes conjugation, and then Sig2 performs phase compensation; when the phase of Sig2 is used as the reference phase, Sig2 takes conjugation, and then Sig1 performs phase compensation.

6. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 4 is characterized in that: The S31 includes: the sub-pulse exists in the form of a complex number, according to the Euler formula It can be seen that conjugating Sig1 means negative phase:

7. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 6 is characterized in that: The step S32 includes: the calculation process of each discrete point of the result sub-pulse is expressed by the formula: Where A1, A2, and A represent the amplitudes of the discrete points of Sig1, Sig2, and the discrete points of the result sub-pulse, respectively; the phase of the discrete point of the result sub-pulse is the phase difference between the two sub-pulses. The theoretically obtained result is that the phase of each discrete point of the sub-pulse is Only the amplitude is different, but due to the presence of noise in engineering applications, the phase of each discrete point is ± Random error.

8. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 7, characterized in that: The S4 includes: adding and averaging the real parts of the discrete points obtained by the S3 operation to obtain the mean of the real parts, and adding and averaging the imaginary parts to obtain the mean of the imaginary parts.

9. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 8, characterized in that: The S5 includes: the mean of the phase of the discrete points of the frequency overlap part is the atan value of the mean of the imaginary part and the mean of the real part, and the calculation process is: This phase is the phase difference between the two sub-pulses Sig2 and Sig1.

10. The DSP-based simple calculation method for step-frequency sub-pulse phase difference as claimed in claim 9, characterized in that: After S5, the method further includes: after calculating the phase difference between Sig2 and Sig1, performing phase compensation on Sig2, thereby extracting the spectrum for synthesis.

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