A single-channel correlation interferometer direction-finding device and method based on amplitude correlation

Abstract

The present invention discloses a single-channel correlation interferometer direction-finding device and method based on amplitude correlation. The device utilizes the square amplitude of a signal synthesized by N array elements after four phase shifts and a reference array element, normalizes the square amplitude of the signal, and completes the preparation of a reference data sample library. The normalized square amplitude in the reference data sample library and the normalized square amplitude obtained when performing direction-finding are extracted to calculate correlation coefficients, respectively, and the angle corresponding to the maximum value of the correlation coefficient in different directions is searched out. The angle is the incident angle of the measured signal, that is, the direction of the incident signal. The step of calculating the phase difference in the prior art is eliminated, the influence of the array element with weak receiving signal strength in the array on the direction-finding result is weakened, and the direction-finding performance is improved.

Description

Technical Field

[0001] The present invention relates to the field of wireless signal direction finding, and in particular to a single-channel correlation interferometer direction finding device and method based on amplitude correlation. Background Art

[0002] Radio signal direction finding has always been a key technology and research hotspot in the field of signal reconnaissance and detection. Radio direction finding technology is widely used in military electronic reconnaissance, civil radio management, signal spectrum detection and other fields, and plays an increasingly important role in many fields of modern battlefields, national economy and social development.

[0003] Correlation interferometer direction finding is an excellent representative of many direction finding technologies. It uses the measured phase difference to compare with the phase difference stored in the sample library to estimate the incident angle of the signal. The phase difference data in the sample library is collected in advance by the direction finding system. Since the collected phase difference data already includes factors such as mutual coupling between array elements, array element position error and receiving channel inconsistency, comparing the measured phase difference with the value in the sample library can reduce the impact of these factors and thus improve the direction finding accuracy.

[0004] Single-channel correlation interferometers require complex device switching and longer measurement time to obtain the phase difference between a pair of array elements using a phase shifter, and obtain the phase difference between multiple groups of array elements by switching the switch array in time-sharing. Like other technologies that use phase difference direction finding, the larger the array aperture, the higher the direction finding accuracy, but at the same time, the more serious the direction finding ambiguity. In correlation interferometer direction finding, direction finding ambiguity means that the correlation coefficient calculated by the measured phase difference and the phase difference in several different directions in the sample library is close to the correlation coefficient calculated in the actual incoming wave direction, resulting in direction finding deviation. Existing correlation interferometer direction finding systems usually reduce the antenna aperture and sacrifice the direction finding accuracy to reduce ambiguity, or determine the approximate range of the incoming wave direction based on the phase difference of the shortest baseline in the array, and then search within the range, but the incoming wave direction determined based on the short baseline usually has a large error, resulting in the inability to correctly determine the incoming wave direction range. At the same time, in an array composed of multiple array elements, due to the influence of mutual coupling and occlusion between array elements, the directional pattern of the array element is distorted and deviates from the ideal omnidirectional characteristics. The array element with low signal receiving power has a larger phase measurement error, resulting in a decrease in direction finding accuracy. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a single-channel correlation interferometer direction-finding device and method based on amplitude correlation, so that the correlation interferometer can ensure the direction-finding accuracy without being equipped with a phase difference calculation module.

[0006] Technical solution: The present invention provides a single-channel correlation interferometer direction-finding device based on amplitude correlation, which includes an acquisition module, a normalization module, a correlation coefficient calculation module, and an incident signal angle calculation module;

[0007] The acquisition module comprises N array elements, at least one reference array element, a radio frequency preprocessing unit, a channel receiving unit, and a computing unit, and is used to acquire signals from different incident directions. The N array elements are phase-shifted four times and combined with one reference array element to obtain a synthetic signal. The synthetic signal is amplified and filtered by the radio frequency preprocessing unit, and the preprocessed signal is frequency-converted, filtered, and analog-to-digital converted by the channel receiving unit, and finally the square of the amplitude of the signal is extracted by the computing unit;

[0008] The normalization module is used to normalize the square amplitude of the signal obtained in the acquisition module to obtain a normalized square amplitude, and to make the normalized square amplitude into a reference data sample library;

[0009] The correlation coefficient calculation module is used to take out the normalized amplitude square from the reference data sample library, and calculate the correlation coefficient with the normalized amplitude square of the signal collected during direction finding.

[0010] The incident signal angle calculation module is used to search for the angle corresponding to the maximum value of the correlation coefficient in different directions. The angle is the incident angle of the measured signal, that is, the direction of the incident signal.

[0011] The present invention correspondingly provides a single-channel correlation interferometer direction finding method based on amplitude correlation, comprising the following steps:

[0012] (1) Collect signals from different incident directions, and obtain a composite signal by combining N array elements with a reference array element after four phase shifts. The composite signal is amplified and filtered, and then frequency-converted, filtered, and analog-to-digital converted to extract the square of the signal amplitude.

[0013] (2) normalizing the square amplitude of the signal to obtain a normalized square amplitude, and making the normalized square amplitude into a reference data sample library;

[0014] (3) taking out the normalized square amplitude from the reference data sample library, and calculating the correlation coefficient with the normalized square amplitude of the signal collected during direction finding;

[0015] (4) The angle corresponding to the maximum value of the correlation coefficient in different directions is searched out. This angle is the incident angle of the measured signal, that is, the direction of the incident signal.

[0016] Beneficial effect: Compared with the prior art, the present invention has the significant feature of utilizing the square amplitude of the synthesized signal of the reference array element after four phase shifts of N array elements, normalizing the square amplitude of the signal to complete the preparation of the reference data sample library, extracting the normalized square amplitude in the reference data sample library and the normalized square amplitude obtained when performing direction finding to calculate the correlation coefficient respectively, searching for the angle corresponding to the maximum value of the correlation coefficient in different directions, and the angle is the incident angle of the measured signal, that is, the direction of the incident signal, eliminating the step of calculating the phase difference in the prior art, weakening the influence of the array element with weak receiving signal strength on the direction finding result, and improving the direction finding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of the present invention;

[0018] Figure 2 It is a schematic diagram of the composition of the amplitude-correlated single-channel correlation interferometer direction-finding device of the present invention;

[0019] Figure 3 It is the square of the amplitude collected at a certain time when making the reference data sample library in the present invention;

[0020] Figure 4 It is the correlation coefficient of executing a certain direction finding calculation in the present invention. DETAILED DESCRIPTION

[0021] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments.

[0022] Example 1

[0023] See also Figure 1 and Figure 2 As shown, this embodiment provides a single-channel correlation interferometer direction finding device based on amplitude correlation, comprising an acquisition module, a normalization module, a correlation coefficient calculation module, and an incident signal angle calculation module;

[0024] The acquisition module includes N array elements, at least one reference array element, a radio frequency preprocessing unit, a channel receiving unit, and a computing unit, which are used to collect signals from different incident directions. The synthesized signal is obtained by four phase shifts of the N array elements and one reference array element. The synthesized signal is amplified and filtered by the radio frequency preprocessing unit, and the preprocessed signal is frequency-converted, filtered, and analog-to-digital converted by the channel receiving unit. Finally, the square of the amplitude of the signal is extracted by the computing unit.

[0025] Specifically, the acquisition module has a direction-finding antenna, which contains 9 array elements, array element 0 is located at the center of the circle, and the remaining 8 array elements are evenly distributed on the circumference. With array element 0 as a reference, the signals of array elements 1 to 8 are phase-shifted by 0°, 90°, 180° and 270° in sequence, and then synthesized with the signal of array element 0, and the square of the amplitude of the synthesized signal is calculated, and then sent to the normalization processing module for normalization processing according to the maximum value thereof;

[0026] The normalization module is used to normalize the square of the amplitude of the signal obtained in the acquisition module, and store the square of the amplitude of the normalized signal. The entire reference data is collected according to a certain frequency interval and angle interval, and finally a reference data sample library is made. Specifically, the input of the normalization module is the square of the amplitude of the synthetic signal. The normalized data is A=[a1,a2,…,a 32 ], data is collected at intervals of 1° at each frequency point to make a reference data sample library, so that the data dimension stored at each frequency point is 360×32; data is collected at intervals of 5MHz within the measurement frequency range of 200M~6000MHz, and the normalization formula is as follows:

[0027]

[0028] The preparation of the reference data sample library is as follows: each array element is phase-shifted by 0°, 90°, 180° and 270° and then synthesized with the reference array element to obtain 4 signals. The 4 signals are amplified and filtered by the RF preprocessing unit, and then subjected to necessary frequency conversion, filtering, amplification and analog-to-digital conversion by the receiving channel unit, and then the square of the amplitude is extracted by the calculation unit. For an array consisting of N array elements and 1 reference array element, the number of amplitude data collected at each frequency point and in each direction is 4N. The 4N data are normalized according to the maximum value, and the entire reference data is collected and stored according to a certain frequency interval and angle interval, and finally prepared into a reference data sample library;

[0029] The smaller the frequency and angle intervals are when making the reference data sample library, the higher the measurement accuracy of the system. However, at the same time, the longer the acquisition time is, the larger the storage space occupied by the storage sample library is, and the greater the amount of calculation of the correlation coefficient and the angle search is. For the direction finding method within a wide frequency band, the reference data sample library is made at intervals of 1MHz or 5MHz in frequency and 1° in azimuth angle. The data on other frequencies are obtained by interpolation.

[0030] See also Figure 3 As shown, when the measurement frequency is 4.5 GHz and the incident direction is 0°, 32 amplitude squares are collected by first switching the direction-finding antenna and then switching the phase shift;

[0031] The correlation coefficient calculation module is used to take out the normalized amplitude square from the reference data sample library, and calculate the correlation coefficient with the normalized amplitude square of the signal collected during direction finding. If the measured frequency point is a frequency point stored in the reference data sample library, the amplitude square of the signal is directly taken out from the reference data sample library for correlation coefficient calculation. If the amplitude square of the signal at the measured frequency point is not in the reference data sample library, two groups of amplitude squares of the signals closest to the measured frequency point are selected from the reference data sample library to interpolate to obtain reference data. The formula for calculating the first correlation coefficient is as follows:

[0032]

[0033] The second formula for calculating the correlation coefficient is as follows:

[0034]

[0035] Where A is the normalized square magnitude vector measured when performing direction finding, P j is the square vector of the amplitude of the frequency signal direction j in the reference database, and T represents the transpose;

[0036] The incident signal angle calculation module is used to search for the angle corresponding to the maximum value of the correlation coefficient in different directions. This angle is the incident angle of the measured signal, that is, the direction of the incident signal. In particular, when the angle interval of the reference data sample library is large, in order to improve the angle measurement accuracy, the maximum value of the correlation coefficient and the larger value of the adjacent correlation coefficients on the left and right sides can be used to calculate the incident angle of the measured signal by using an interpolation algorithm;

[0037] See also Figure 4 As shown in the figure, when a 4.5 GHz signal is incident on the array from a direction of 231°, the correlation coefficient is calculated using the measured normalized amplitude square and the sample data of 0° to 359° at the 4.5 GHz frequency point stored in the reference data sample library. At this time, the two methods of calculating the correlation coefficient are not much different in the main lobe of the signal incident direction, but the side lobe of the first calculation method is lower, which means that the anti-angle ambiguity performance is better.

[0038] Example 2

[0039] See also Figure 1 and Figure 2 As shown, corresponding to Embodiment 1, this embodiment provides a single-channel correlation interferometer direction finding method based on amplitude correlation, which specifically includes the following steps:

[0040] (1) Collect signals from different incident directions, obtain a composite signal by four phase shifts of N array elements and one reference array element, amplify and filter the composite signal, perform frequency conversion, filtering, and analog-to-digital conversion on the composite signal, and finally extract the square of the signal amplitude;

[0041] Specifically, the signal acquisition includes a direction-finding antenna, which includes 9 array elements, array element 0 is located at the center of the circle, and the remaining 8 array elements are evenly distributed on the circumference. With array element 0 as a reference, the signals of array elements 1 to 8 are phase-shifted by 0°, 90°, 180°, and 270° in sequence, and then synthesized with the signal of array element 0. After the synthesized signal is synthesized, the square of the amplitude of the synthesized signal is calculated, and the square of the amplitude is normalized according to the maximum value;

[0042] (2) The square amplitude of the signal in the reference data sample library is normalized, and the square amplitude of the normalized signal is stored. The entire reference data is collected according to a certain frequency interval and angle interval, and finally a reference data sample library is prepared. The square amplitude of the signal is The normalized data is A=[a1,a2,…,a 32 ], data is collected at intervals of 1° at each frequency point to make a reference data sample library, so that the data dimension stored at each frequency point is 360×32; data is collected at intervals of 5MHz within the measurement frequency range of 200M~6000MHz, and the normalization formula is as follows:

[0043]

[0044] Specifically, the reference data sample library is prepared as follows: each array element is phase-shifted by 0°, 90°, 180° and 270° and then synthesized with the reference array element to obtain 4 signals. The 4 signals are amplified, filtered and processed by the radio frequency preprocessing unit, and then subjected to necessary frequency conversion, filtering, amplification and analog-to-digital conversion by the receiving channel unit, and then the square of the amplitude is extracted by the calculation unit. For an array consisting of N array elements and 1 reference array element, the number of amplitude data collected at each frequency point and in each direction is 4N. The 4N data are normalized according to the maximum value, and the entire reference data is collected and stored according to a certain frequency interval and angle interval, and finally prepared into a reference data sample library;

[0045] The smaller the frequency and angle intervals are when making the reference data sample library, the higher the measurement accuracy of the system. However, at the same time, the longer the acquisition time is, the larger the storage space occupied by the storage sample library is, and the greater the amount of calculation of the correlation coefficient and the angle search is. For the direction finding method within a wide frequency band, the reference data sample library is made at intervals of 1MHz or 5MHz in frequency and 1° in azimuth angle. The data on other frequencies are obtained by interpolation.

[0046] See also Figure 3 As shown, when the measurement frequency is 4.5 GHz and the incident direction is 0°, 32 amplitude squares are collected by first switching the direction-finding antenna and then switching the phase shift;

[0047] (3) Take the normalized square amplitude from the reference data sample library, and calculate the correlation coefficient with the normalized square amplitude of the signal collected during direction finding. If the measured frequency point is a frequency point stored in the reference data sample library, directly take the data from the reference data sample library to calculate the correlation coefficient. If the reference data sample library does not have the square amplitude of the signal at the measured frequency point, select the square amplitude of two groups of signals closest to the measured frequency point from the sample library to interpolate and obtain the reference data. The formula for calculating the first correlation coefficient is as follows:

[0048]

[0049] The second formula for calculating the correlation coefficient is as follows:

[0050]

[0051] Where A is the normalized square magnitude vector measured when performing direction finding, P j is the square vector of the amplitude of the frequency signal direction j in the reference database, and T represents the transpose;

[0052] (4) Search for the angle corresponding to the maximum value of the correlation coefficient in different directions. This angle is the incident angle of the measured signal, that is, the direction of the incident signal. In particular, when the angle interval of the reference database is large, in order to improve the angle measurement accuracy, the maximum value of the correlation coefficient and the larger value of the adjacent correlation coefficients on its left and right sides can be used to calculate the incident angle of the measured signal using an interpolation algorithm.

[0053] See also Figure 4 As shown in the figure, when a 4.5 GHz signal is incident on the array from a direction of 231°, the correlation coefficient is calculated using the measured normalized amplitude square and the sample data of 0° to 359° at the 4.5 GHz frequency point stored in the reference data sample library. At this time, the two methods of calculating the correlation coefficient are not much different in the main lobe of the signal incident direction, but the side lobe of the first calculation method is lower, which means that the anti-angle ambiguity performance is better.

Claims

1. A single-channel correlation interferometer direction finding device based on amplitude correlation, characterized in that: It includes acquisition module, normalization module, correlation coefficient calculation module and incident signal angle calculation module; The acquisition module comprises N array elements, at least one reference array element, a radio frequency preprocessing unit, a channel receiving unit, and a computing unit, and is used to acquire signals from different incident directions. The N array elements are phase-shifted four times and combined with one reference array element to obtain a synthetic signal. The synthetic signal is amplified and filtered by the radio frequency preprocessing unit, and the preprocessed signal is frequency-converted, filtered, and analog-to-digital converted by the channel receiving unit, and finally the square of the amplitude of the signal is extracted by the computing unit; The normalization module is used to normalize the square amplitude of the signal obtained in the acquisition module to obtain a normalized square amplitude, and to make the normalized square amplitude into a reference data sample library; The correlation coefficient calculation module is used to take out the normalized amplitude square from the reference data sample library, and calculate the correlation coefficient with the normalized amplitude square of the signal collected during direction finding. The incident signal angle calculation module is used to search for the angle corresponding to the maximum value of the correlation coefficient in different directions. The angle is the incident angle of the measured signal, and the incident angle corresponds to the direction of the incident signal.

2. The single-channel correlation interferometer direction finding device based on amplitude correlation according to claim 1, characterized in that: The preparation of the reference data sample library includes: synthesizing each array element with the reference array element after phase shifting by 0°, 90°, 180° and 270° to obtain 4 signals, calculating the square of the amplitude of the 4 signals, for an array consisting of N array elements and 1 reference array element, the number of data collected at each frequency point and in each direction is 4N, the 4N data are normalized using their maximum value, and the collection and storage are completed according to certain frequency intervals and angle intervals, and finally a reference data sample library is prepared.

3. The single-channel correlation interferometer direction finding device based on amplitude correlation according to claim 2, characterized in that: For direction finding within a wide frequency band, a reference data sample library is prepared at intervals of 1 MHz or 5 MHz in frequency and at intervals of 1° in azimuth, and data at other frequency points are obtained by interpolation.

4. The single-channel correlation interferometer direction finding device based on amplitude correlation according to claim 2 or 3, characterized in that: If there is no data of the measured frequency point in the reference data sample library, two sets of data closest to the measured frequency point are selected from the reference data sample library, and the reference data of the frequency point is obtained by linear interpolation and the correlation coefficient is calculated.

5. A single-channel correlation interferometer direction finding method based on amplitude correlation, characterized in that: The following steps are involved: (1) Collect signals from different incident directions, and obtain a composite signal by combining N array elements with a reference array element after four phase shifts. The composite signal is amplified and filtered, and then frequency-converted, filtered, and analog-to-digital converted to extract the square of the signal amplitude. (2) normalizing the square amplitude of the signal to obtain a normalized square amplitude, and making the normalized square amplitude into a reference data sample library; (3) taking out the normalized square amplitude from the reference data sample library, and calculating the correlation coefficient with the normalized square amplitude of the signal collected during direction finding; (4) The angle corresponding to the maximum value of the correlation coefficient in different directions is searched out. The angle is the incident angle of the measured signal, and the incident angle corresponds to the direction of the incident signal.

6. The single-channel correlation interferometer direction finding method based on amplitude correlation according to claim 5, characterized in that: The preparation of the reference data sample library is as follows: each array element is phase-shifted by 0°, 90°, 180° and 270° and then synthesized with the reference array element to obtain four signals. The square amplitudes of the four signals are calculated. For an array consisting of N array elements and 1 reference array element, the number of data collected at each frequency point and in each direction is 4N. The 4N data are normalized using their maximum value, and the collection and storage are completed at certain frequency intervals and angle intervals to finally prepare a reference data sample library.

7. The single-channel correlation interferometer direction finding method based on amplitude correlation according to claim 6, characterized in that: For direction finding within a wide frequency band, a reference data sample library is prepared at intervals of 1 MHz or 5 MHz in frequency and at intervals of 1° in azimuth, and data at other frequency points are obtained by interpolation.

8. The single-channel correlation interferometer direction finding method based on amplitude correlation according to claim 6 or 7, characterized in that: If there is no data of the measured frequency point in the reference data sample library, two sets of data closest to the measured frequency point are selected from the reference data sample library, and the reference data of the frequency point is obtained by linear interpolation and the correlation coefficient is calculated.

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