A narrow spectrum high power microwave direction finding calibration method and system

Abstract

The embodiment of the present application provides a narrow-spectrum high-power microwave direction-finding calibration method and system, the system comprises a plurality of radio frequency switches, the radio frequency switches are arranged between the receiving antennas of each radio frequency channel of an interferometer and power dividers; a calibration signal source is used for generating a calibration radiation signal, an output end of the calibration signal source is connected with an input end of the power divider through a wired mode, and each output end of the power divider is connected with an input end of a two-way radio frequency switch of a corresponding radio frequency channel of the interferometer through a wired mode, and the calibration radiation signal of the calibration signal source is proportionally distributed by the power divider into a plurality of calibration branch radiation signals equal to the number of radio frequency channels of the interferometer. The embodiment of the present application regenerates the external radiation calibration table by introducing the calibration signal source, ensures the accuracy of the measured phase in the whole frequency range, and effectively solves the problem that the measured phase is opposite to the real phase in some cases due to the limitation of the sampling rate.

Description

Technical Field

[0001] This invention relates to the field of electronic countermeasures and electronic reconnaissance technology, and in particular to a narrow-spectrum high-power microwave direction finding calibration method and system. Background Technology

[0002] Interferometer direction finding uses the phase difference between the signals received from a radiation source by different antennas to determine the direction of a target. Its working principle is as follows: Figure 1 As shown, assuming the distance between the radiating source and the receiving antenna is much greater than the distance between the receiving antennas (satisfying the far-field condition), A and B are two receiving antennas (capable of receiving signals within a ±90° range), the straight-line distance between A and B is D, the incident angle of the radiating source signal is θ, the signal wavelength is λ, and the phase difference of the wavefront when the signal reaches antenna elements A and B is Φ (absolute phase difference), then we have: Therefore, as long as the phase difference between the radiation source signal and the two antennas is measured, the incident direction of the radiation source can be calculated.

[0003] Existing interferometer direction finding system phase error calibration methods are all based on the design of traditional superheterodyne receivers. That is, after the signal is received by the antenna, it is frequency-converted by a frequency conversion channel and output to a direction finding digital receiver for acquisition and processing to obtain the phase difference. The principle block diagram is as follows: Figure 2 As shown. The multi-interferometer baseline direction finding scheme is a mature technology, but its processing bandwidth is limited by the bandwidth of the frequency conversion channel and the bandwidth of the direction finding digital receiver, and the instantaneous bandwidth generally does not exceed 1 GHz. For narrow-spectrum high-power microwave signals from non-cooperative parties, whose operating frequency is unknown and may burst in a single burst, traditional superheterodyne receivers that do not operate in parallel across multiple bands cannot achieve instantaneous direction finding of narrow-spectrum high-power microwave signals.

[0004] Figure 3 The diagram shown is a block diagram of a typical narrow-spectrum high-power microwave direction finding scheme. Figure 3 As shown, each channel of the interferometer consists of multiple coprime sampling rate ADCs (Analog-to-Digital Converters). Figure 3 The system uses two coprime ADCs for high-speed sampling and transmits the data to the FPGA. At the same time, the FPGA receives the frequency information output by the ultra-wideband single-bit instantaneous frequency measurement module. The FPGA selects the corresponding ADC data for processing according to the frequency of the instantaneous measurement module and calculates the phase difference of different channels.

[0005] Figure 3 The proposed scheme uses a high-speed sample-and-hold circuit and multiple low-sampling-rate ADCs to achieve instantaneous acquisition and processing of ultra-wideband signals. Different sampling rates are selected at different frequency points. However, due to the limitation of the sampling rate, the measured phase is opposite to the true phase in some cases. Summary of the Invention

[0006] In view of the above-mentioned problems existing in the prior art, the present invention provides a narrow-spectrum high-power microwave direction finding calibration method and system to solve the technical problem that the measured phase is opposite to the true phase in some cases due to the limitation of sampling rate in the prior art.

[0007] This invention provides a narrow-spectrum high-power microwave direction finding calibration system, implemented using a wired calibration method, including: Several radio frequency switches, wherein the radio frequency switches are two-to-one radio frequency switches, are respectively set between the receiving antenna and the power divider of each radio frequency channel of the interferometer via wired connection; A calibration signal source is provided, which is used to generate calibration radiation signals. Its output is connected to the input of a power divider via a wired connection. Each output of the power divider is connected to the input of a two-to-one RF switch of the corresponding RF channel of the interferometer via a wired connection. The calibration radiation signals of the calibration signal source are distributed proportionally by the power divider into multiple calibration branch radiation signals equal to the number of RF channels of the interferometer.

[0008] In addition, embodiments of the present invention also provide a narrow-spectrum high-power microwave direction finding calibration system, which is implemented using a wireless calibration method, including, A calibration signal source, wherein the calibration signal source is used to generate a calibration radiation signal; A transmitting antenna is provided, which is set on the calibration signal source and is positioned directly opposite the receiving antenna of the interferometer. The transmitting antenna and the receiving antenna are polarized in the same way and meet the far-field distance requirements.

[0009] In addition, this invention also provides a narrow-band high-power microwave direction finding calibration method, implemented based on the narrow-band high-power microwave direction finding calibration system described in any of the above embodiments, including the following steps. Step S1: Select a matching calibration method based on the characteristics of the interferometer; Step S2: Power on the device to put the direction finding calibration system into normal direction finding working mode; Step S3: Control the interferometer to clear the external radiation calibration table; Step S4: Set the calibration signal source to radiate a fixed pulse signal, and set the calibration signal source status to "on". Step S5: The interferometer receives the radiated signal, and its ultra-wideband single-bit instantaneous frequency measurement module measures the radiation source parameters of the pulse signal, determines the sampling rate channel selected for each radio frequency channel, and stores the phase difference of the corresponding sampling rate channel after phase correction. Step S6: Verify whether the radiation source parameters measured in step S5 and the radiation source parameters set in step S4 meet the consistency requirements. If not, increase the radiation power of the calibration signal source and execute step S4. If they meet the requirements, record the phase difference of the corresponding sampling rate channel after phase correction stored in step S5. Step S7, according to the frequency step parameters △f The radiation frequency of the calibration signal source is changed sequentially, and then the process proceeds to step S4 until all frequency points are tested. Step S8: Generate an external radiation calibration table based on the phase difference values ​​corresponding to all frequency points, and send it to the interferometer receiver's internal field table.

[0010] In one embodiment, the method for determining the sampling rate channel for each RF channel in step S5 is as follows: judge f 测 Does it satisfy the following formula?

[0011] in, n It is a positive integer not less than 1. k It is a positive integer not less than 2. f 测 This indicates the frequency of the pulse signal measured by the ultra-wideband single-bit instantaneous frequency measurement module. fs 1 and fs 2 represents the sampling rates of the two coprime ADC1 and ADC2 corresponding to each RF channel; If the conditions are met, the ADC2 sampling rate channel is selected; otherwise, the ADC1 sampling rate channel is selected.

[0012] In one embodiment, the phase difference is corrected in step S5 as follows: Determine whether the following expression is true.

[0013] in, f 测 This indicates the frequency of the pulse signal measured by the ultra-wideband single-bit instantaneous frequency measurement module. fs The sampling rate of the corresponding sampling rate channel determined in step S5. Indicates rounding down; If the above formula holds true, then the phase difference of the corresponding sampling rate channel is stored directly; Otherwise, the phase difference of the corresponding sampling rate channel is inverted before storage.

[0014] In one embodiment, the radiation source parameters include frequency, pulse repetition period, and pulse width.

[0015] Compared with the prior art, the beneficial effects of the narrow-spectrum high-power microwave direction finding calibration method and system provided by the embodiments of the present invention are as follows: the embodiments of the present invention regenerate the external radiation calibration table by introducing a calibration signal source, thereby ensuring the accuracy of phase measurement in all frequency ranges and effectively solving the problem that the measured phase is opposite to the true phase in some cases due to the limitation of the sampling rate. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the interferometer direction finding principle involved in the background section of this invention; Figure 2 This is a schematic diagram of a multi-interferometer baseline direction finding scheme involved in the background section of this invention; Figure 3 This is a schematic diagram of a typical narrow-spectrum high-power microwave direction finding scheme involved in the background section of this invention; Figure 4 This is a schematic diagram of a narrow-spectrum high-power microwave direction finding calibration system provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of another narrow-spectrum high-power microwave direction finding calibration system provided in an embodiment of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] Various embodiments and features of this application are described herein with reference to the accompanying drawings.

[0019] These and other features of this application will become apparent from the following description of preferred forms of embodiments given as non-limiting examples, with reference to the accompanying drawings.

[0020] It should also be understood that although this application has been described with reference to some specific examples, those skilled in the art can certainly implement many other equivalent forms of this application, which have the features described in the claims and are therefore all within the scope of protection defined herein.

[0021] The above and other aspects, features and advantages of this application will become more apparent when taken in conjunction with the accompanying drawings and in view of the following detailed description.

[0022] Specific embodiments of this application are described below with reference to the accompanying drawings; however, it should be understood that the claimed embodiments are merely examples of this application, which can be implemented in various ways. Well-known and / or repeated functions and structures are not described in detail to ascertain the true intent based on the user's historical operations, and to avoid unnecessary or redundant details that would obscure this application. Therefore, the specific structural and functional details claimed herein are not intended to be limiting, but merely serve as the basis and representative basis for the claims to teach those skilled in the art to use this application in various ways with substantially any suitable detailed structure.

[0023] This specification may use the phrases “in one embodiment,” “in another embodiment,” “in yet another embodiment,” or “in other embodiments,” all of which may refer to one or more of the same or different embodiments according to this application.

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The embodiments described are for illustrative purposes only and are not intended to limit the scope of the invention. The following description, in conjunction with... Figure 1-5 The preferred embodiments of the present invention will be described in further detail below: like Figure 4-5 As shown, calibration can be performed using wired calibration or wireless radiation calibration.

[0025] This invention provides a narrow-spectrum high-power microwave direction finding calibration system, implemented using a wired calibration method, including: Several radio frequency switches, wherein the radio frequency switches are two-to-one radio frequency switches, are respectively set between the receiving antenna and the power divider of each radio frequency channel of the interferometer via wired connection; A calibration signal source is provided, which is used to generate calibration radiation signals. Its output is connected to the input of a power divider via a wired connection. Each output of the power divider is connected to the input of a two-to-one RF switch of the corresponding RF channel of the interferometer via a wired connection. The calibration radiation signals of the calibration signal source are distributed proportionally by the power divider into multiple calibration branch radiation signals equal to the number of RF channels of the interferometer.

[0026] like Figure 4 The diagram shown illustrates wired calibration. In this embodiment, a calibration signal source, a power divider, and RF switches are used. Each antenna RF channel has a 2-to-1 RF switch (the switch's operating frequency and power tolerance should meet system requirements). The calibration signal source radiates the signal, and both RF switches are switched to the corresponding ports of the power divider. Each channel operates in parallel, and processing is performed within the FPGA.

[0027] Another embodiment of the present invention provides a narrow-spectrum high-power microwave direction finding calibration system, which is implemented using a wireless calibration method, including: A calibration signal source, wherein the calibration signal source is used to generate a calibration radiation signal; A transmitting antenna is provided, which is set on the calibration signal source and is positioned directly opposite the receiving antenna of the interferometer. The transmitting antenna and the receiving antenna are polarized in the same way and meet the far-field distance requirements.

[0028] like Figure 5 The diagram shown illustrates wireless radiation calibration. In this embodiment, a calibration signal source and a transmitting antenna are primarily used. The external radiation source (calibration signal source) faces the receiving antenna. The polarization of the radiating antenna and the receiving antenna are consistent and meet the far-field distance requirements. Each channel operates in parallel, and processing is performed within the FPGA.

[0029] Taking a two-element receiving antenna as an example, the sampling rates of the two coprime ADC1 and ADC2 are respectively fs 1 and fs 2, and fs 2 ＞ fs 1. The phases of the receiving antenna a sampled by the two ADCs are respectively φa 2 -fs 1. φa 2 -fs 2. The phases of the receiving antenna b sampled by the two ADCs are respectively φb 2 -fs 1 ,φb 2 -fs 2. Due to the different sampling rates of the two ADCs, there are two sets of measurement phase differences between the two antennas, namely... and .

[0030] In addition, the present invention also provides a narrow-spectrum high-power microwave direction finding calibration method, which is implemented based on a narrow-spectrum high-power microwave direction finding calibration system described in any embodiment of the present invention, and includes the following steps. Step S1: Select the appropriate calibration method based on the characteristics of the interferometer. If it is external radiation calibration (wireless calibration), align the radiation source antenna with the normal of the interferometer receiving antenna (the distance is far enough to meet the far-field condition of the antenna); if it is internal calibration (wired calibration), divide the calibration signal source signal through a power divider (phase consistency meets system requirements) and input it to the two channels of the direction finding system respectively. Step S2: Power on the device to put the direction finding calibration system into normal direction finding working mode; Step S3: Control the interferometer to clear the external radiation calibration table; Step S4: Set the calibration signal source to radiate a fixed pulse signal, with the frequency set to [frequency value missing]. fmin Then, set parameters such as cycle recurrence (PRI) and pulse width (PW) (specific parameters are set according to the direction finding equipment functions), and then set the calibration signal source status to on; Step S5: The interferometer receives the radiated signal, and its ultra-wideband single-bit instantaneous frequency measurement module measures the radiation source parameters of the pulse signal, including frequency, pulse repetition period, pulse width, etc., determines the sampling rate channel selected for each radio frequency channel, and stores the phase difference of the corresponding sampling rate channel after phase correction. The method for determining the sampling rate channel for each radio frequency channel is as follows: judge f 测 Does it satisfy the following formula? (1) in, n It is a positive integer not less than 1. k A positive integer not less than 2 ( k The value of is mainly considered f 测 The smaller the difference from the actual frequency, the better. k (the smaller the value, the better). f 测 This indicates the frequency of the pulse signal measured by the ultra-wideband single-bit instantaneous frequency measurement module. fs 1 and fs 2 represents the sampling rates of the two coprime ADC1 and ADC2 corresponding to each RF channel; If satisfied, then select the ADC2 sampling rate channel (taking the phase difference as ). Otherwise, select the ADC1 sampling rate channel (taking the phase difference as ). ); Based on this, the phase difference is corrected as follows: Based on the ADC determined by equation (1), determine whether equation (2) holds to determine whether the phase difference is inverted. (2) in, f 测 This indicates the frequency of the pulse signal measured by the ultra-wideband single-bit instantaneous frequency measurement module. fs The sampling rate of the corresponding sampling rate channel determined in step S5. Indicates rounding down; If the above formula holds true, then the phase difference of the corresponding sampling rate channel is stored directly; Otherwise, invert the phase difference of the corresponding sampling rate channel before storing it; Step S6: Verify whether the radiation source parameters measured in step S5 and the radiation source parameters set in step S4 meet the consistency requirements. If not, increase the radiation power of the calibration signal source and execute step S4. If they meet the requirements, record the phase difference of the corresponding sampling rate channel after phase correction stored in step S5. That is, determine the selected sampling rate channel according to formula (1) and store the phase difference of the sampling rate channel according to formula (2). Step S7, according to the frequency step parameters △f The radiation frequency of the calibration signal source is changed sequentially, and then the process proceeds to step S4 until all frequency points are tested. Step S8: Generate an external radiation calibration table based on the phase difference values ​​corresponding to all frequency points, and send it to the interferometer receiver's internal field table.

[0031] The value of the phase difference is illustrated below using wireless radiation calibration as an example.

[0032] Example 1 (1) Set up a ground radiation source with a frequency of 10.5 GHz, a cycle of 100 μs, and a pulse width of 1 μs.

[0033] (2) The sampling rates of the two coprime samples are 1.5 GHz and 1.7 GHz, respectively.

[0034] (3) The ultra-wideband single-bit instantaneous frequency measurement module measures the frequency of the radiation source as 10.495 GHz, the cycle length as 100 μs, and the pulse width as 1 μs.

[0035] (4) Take k=2. According to formula (1), when n=14, 10.4<10.495<10.6, which satisfies formula (1). Select the phase difference of the 1.7GHz sampling rate channel.

[0036] (5) Calculate according to formula (2), If equation (2) is satisfied, there is no need to invert it; the phase difference of the 1.7GHz sampling rate channel can be stored directly.

[0037] Example 2 (1) Set up a ground radiation source with a frequency of 11 GHz, a cycle of 100 μs, and a pulse width of 100 ns.

[0038] (2) The sampling rates of the two coprime samples are 1.5 GHz and 1.7 GHz, respectively.

[0039] (3) At this time, the ultra-wideband single-bit instantaneous frequency measurement module measures the frequency of the radiation source as 10.97 GHz, the cycle length as 100 μs, and the pulse width as 99.9 ns.

[0040] (4) Take k=2 and calculate according to formula (1). When n=14, it does not satisfy 10.4<10.97<10.6; when n=15, it does not satisfy 11.15<10.97<11.35; select the phase difference of the 1.5GHz sampling rate channel.

[0041] (5) Calculate according to formula (2), If equation (2) is satisfied, there is no need to invert it; the phase difference of the 1.5GHz sampling rate channel can be stored directly.

[0042] It should be noted that, for convenience, only a typical two-interferometer baseline folding direction finding calibration procedure is described in this embodiment of the invention. Other interferometers can be implemented by referring to the above embodiment.

[0043] The above embodiments are merely exemplary embodiments of the present invention and are not intended to limit the present invention. The scope of protection of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to the present invention within its spirit and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of the present invention.

Claims

1. A narrow-spectrum high-power microwave direction finding calibration method, characterized in that: Includes the following steps, Step S1: Select a matching calibration method based on the characteristics of the interferometer; Step S2: Power on the device to put the direction finding calibration system into normal direction finding working mode; Step S3: Control the interferometer to clear the external radiation calibration table; Step S4: Set the calibration signal source to radiate a fixed pulse signal, and set the calibration signal source status to "on". Step S5: The interferometer receives the radiated signal. Its ultra-wideband single-bit instantaneous frequency measurement module measures the radiation source parameters of the pulse signal, determines the sampling rate channel selected for each RF channel, and stores the phase difference of the corresponding sampling rate channel after phase correction. The method for determining the sampling rate channel for each RF channel is as follows: judge f 测 Does it satisfy the following formula? in, n It is a positive integer not less than 1. k It is a positive integer not less than 2. f 测 This indicates the frequency of the pulse signal measured by the ultra-wideband single-bit instantaneous frequency measurement module. fs 1 and fs 2 represents the sampling rates of the two coprime ADC1 and ADC2 corresponding to each RF channel; If the conditions are met, the ADC2 sampling rate channel is selected; otherwise, the ADC1 sampling rate channel is selected. The phase difference is corrected in the following way: Determine whether the following expression is true. in, f 测 This indicates the frequency of the pulse signal measured by the ultra-wideband single-bit instantaneous frequency measurement module. fs The sampling rate of the corresponding sampling rate channel determined in step S5. Indicates rounding down; If the above formula holds true, then the phase difference of the corresponding sampling rate channel is stored directly; Otherwise, invert the phase difference of the corresponding sampling rate channel before storing it; Step S6: Verify whether the radiation source parameters measured in step S5 and the radiation source parameters set in step S4 meet the consistency requirements. If not, increase the radiation power of the calibration signal source and execute step S4. If they meet the requirements, record the phase difference of the corresponding sampling rate channel after phase correction stored in step S5. Step S7, according to the frequency step parameters △f The radiation frequency of the calibration signal source is changed sequentially, and then the process proceeds to step S4 until all frequency points are tested. Step S8: Generate an external radiation calibration table based on the phase difference values ​​corresponding to all frequency points, and send it to the interferometer receiver's internal field table.

2. The narrow-spectrum high-power microwave direction finding calibration method according to claim 1, characterized in that: The radiation source parameters include frequency, pulse repetition period, and pulse width.

3. A narrow-spectrum high-power microwave direction finding calibration system, implemented based on the narrow-spectrum high-power microwave direction finding calibration method as described in claim 1 or 2, characterized in that: This is achieved using a wired calibration method, including: Several radio frequency switches, wherein the radio frequency switches are two-to-one radio frequency switches, are respectively set between the receiving antenna and the power divider of each radio frequency channel of the interferometer via wired connection; A calibration signal source is provided, which is used to generate calibration radiation signals. Its output is connected to the input of a power divider via a wired connection. Each output of the power divider is connected to the input of a two-to-one RF switch of the corresponding RF channel of the interferometer via a wired connection. The calibration radiation signals of the calibration signal source are distributed proportionally by the power divider into multiple calibration branch radiation signals equal to the number of RF channels of the interferometer.

4. A narrow-spectrum high-power microwave direction finding calibration system, implemented based on the narrow-spectrum high-power microwave direction finding calibration method as described in claim 1 or 2, characterized in that: This is achieved using wireless calibration, including: A calibration signal source, wherein the calibration signal source is used to generate a calibration radiation signal; A transmitting antenna is provided, which is set on the calibration signal source and is positioned directly opposite the receiving antenna of the interferometer. The transmitting antenna and the receiving antenna are polarized in the same way and meet the far-field distance requirements.

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