CN106450709B - Four-unit interconnected symmetrical oscillator circular antenna array for electric small-distance direction finding - Google Patents

Abstract

The invention relates to a four-element interconnected symmetrical dipole circular loop antenna array for direction finding with an electrically small spacing, relating to an array antenna. It includes 4 symmetrical dipole structure antennas and 2 antenna connection section structures; the 4 symmetrical dipole structure antennas are evenly arranged in a circular array, and the upper and lower parts of the 4 symmetrical dipole structures use antenna connection sections respectively The structure is directly connected, and the electric small spacing means that the spacing between adjacent units is much smaller than the working wavelength. The radiation unit includes 4 symmetrical oscillator structures with the same material and size, which are placed in parallel on the same reference plane, and are evenly angled in a circular array. Arranged at intervals; the antenna connection section structure is 4 symmetrical oscillator structures, the upper part is directly connected with the antenna connection section structure, and the lower part is directly connected with the same antenna connection section structure, and the antenna connection section structure is four cylinders The structure is a connection structure formed by regular quadrilateral connection; the antenna connection section structure and the symmetrical vibrator use the same metal material with the same diameter.

Description

Four-element interconnected symmetrical dipole circular loop antenna array for direction finding with electrically small spacing

technical field

The present invention relates to array antennas, in particular to an electrically small-pitch array antenna design for super-resolution estimation of arrival angle (Direction of Arrival, DOA).

Background technique

Spatial spectrum estimation is used to solve the problem of spatial energy distribution of received signals, so as to determine the number of signals or the direction of arrival of signals ([1] Wang Yongliang, Ding Qianjun, Li Rongfeng. Adaptive processing [M]. Beijing: Tsinghua University University Press, 2009; [2] Wang Yongliang, Chen Hui, Peng Yingning, Wan Qun. Spatial Spectrum Estimation Theory and Algorithm [M]. Beijing: Tsinghua University Press, 2004) The direction of arrival estimation is also called the angle of arrival estimation ([ 3] Haykin S, Liu K J R. Handbook on array processing and sensor networks [M]. John Wiley & Sons, 2010). Direction of arrival estimation is concerned with finding the position of a radiation source in space. Generally speaking, direction of arrival estimation mainly includes two aspects: (1) determining the number of radiation sources in space; (2) determining the spatial position of each radiation source. With the development of direction finding technology, many methods have been developed for different problems. Direction finding technology can be divided into active direction finding technology and passive direction finding technology from the perspective of active and passive reconnaissance (or antenna type). The direction-finding method that obtains the distance and azimuth of the target by emitting electromagnetic waves and receiving the scattered signals of the target is called active direction-finding technology. Since the active direction finding technology system has active radiation equipment, the spatial position of the active direction finding system is exposed, and it is easy to be detected and positioned by other equipment, which is fatal for military applications. Passive direction finding technology is more and more favored by people because of its high degree of confidentiality, and has been widely developed. Using two-unit or multi-unit array antennas to measure the arrival angle of electromagnetic waves, that is, passive direction finding technology, has many important uses ([4]Stephen E.Lipsky.Microwave passive directionfinding[M].Scitech Pub Inc., 2003).

Electrically fine-pitch arrays refer to array systems in which the array pitch is much smaller than the wavelength (generally 0.1 times the wavelength or less). This array can shrink the traditional array to 1/10, which can greatly reduce the size of the array. However, there will be a pair of contradictions between miniaturization and direction finding accuracy. The smaller the size of the array, the lower the gain of the array and the lower the signal-to-noise ratio. The smaller the cell pitch, the slower the phase difference between the cells changes. Coupled with the strong electromagnetic coupling between array elements ([5]HansenR C. Electrically small, superdirective, and superconducting antennas[M].JohnWiley&Sons, 2006), it affects the actual performance of the array antenna, making the traditional electrically small spacing array in Only relying on the improved algorithm still cannot meet the high-precision direction finding requirements. Low gain and small phase difference are the technical bottlenecks that limit the development and application of direction finding for electrically small antennas. Therefore, it is of great practical significance to develop high-precision electrically fine-pitch arrays based on new mechanisms.

Chinese patent 201610350399.5 The present invention discloses a double-loop antenna, which uses the amplitude method to measure direction, and simultaneously receives signals through the first antenna loop body and the second antenna loop body in two directions perpendicular to each other for calculation to accurately determine the source of electromagnetic wave emission direction, so as to effectively improve the resolution of the incident wave direction angle, thereby effectively improving the measurement accuracy; and because it is a double-ring structure that is vertical and nested with the coaxial center, the volume is relatively small ([6] Lu Dejian, Yuan Di. Double loop antenna [P]. Beijing: CN105870631A, 2016-08-17).

Chinese patent 201410080935.5 discloses a passive direction-finding antenna array of a phase interferometer and a phase interferometer ([7] Ai Like, Mo Shaohui, Zhen Yinbiao, Yao Shigang, Zhao Qincheng, Wang Zhibin, Zhang Haitao. Passive measurement of a phase interferometer Directional antenna array and phase interferometer [P]. Guangdong: CN103887613A, 2014-06-25), the first circular antenna array invented by it can contain multiple dual-polarized omnidirectional antenna elements, so in the direction finding process Among them, there are more combinations of phase differences, which is more conducive to improving the accuracy of direction finding and reducing the influence of complex environments.

Chinese patent 201410347386.3 discloses a new portable five-antenna element direction-finding circular array ([8] Guo Fang, Tan Dexin. New portable five-antenna element direction-finding circular array [P]. Sichuan: CN104167613A, 2014-11-26), which The purpose is to provide a five-antenna-element direction-finding circular array that is small in size, light in weight, can be quickly disassembled, and can simultaneously meet the requirements of various direction-finding systems such as interferometers, correlation interferometers, and spatial spectrum estimation.

The direction-finding antenna structures involved in the above three patents are not suitable for space-constrained platforms or low-frequency bands, although factors such as miniaturization and simple structure have been considered.

Contents of the invention

The purpose of the present invention is to solve the above-mentioned problems existing in the electrically small-pitch array, and provide a whole that connects the entire electrically small-pitch symmetric dipole array into a whole, which can enhance the electromagnetic coupling between the electrically small-pitch symmetric dipole array antennas, and improve the response of the antenna to incoming waves. The sensitivity of the angle of arrival, thereby improving the measurement accuracy of the angle of arrival of incoming waves, and can be applied to the measurement of the direction of arrival of space-constrained platforms or low-frequency signals, which is of great significance for the miniaturization, simple structure, portable and easy operation of direction-finding equipment A four-element interconnected symmetrical dipole circular loop antenna array for electrically small spacing direction finding.

The present invention includes four symmetrical oscillator structure antennas and two antenna connection section structures;

The four symmetrical oscillator structure antennas are evenly arranged in a circular array, wherein the upper and lower structures of the four symmetrical oscillators are directly connected by the antenna connection section structure, and the electrically small spacing means that the distance between adjacent units is far Smaller than the working wavelength, the radiating unit includes 4 symmetrical oscillator structures of the same material and size, which are placed in parallel on the same reference plane, and are arranged at equal angular intervals in a circular array; the antenna connection section structure is 4 symmetrical oscillators The upper part of the structure is directly connected with the antenna connection section structure, and the lower part is directly connected with the same antenna connection section structure. The antenna connection section structure is a connection structure formed by connecting four cylinder structures according to a regular quadrilateral; the antenna connection section structure and The symmetrical vibrator uses the same metal material with the same diameter.

The antenna connecting section structure is respectively located at the metal ends of the upper and lower parts of the four symmetrical oscillators, which are closest to the middle of the symmetrical oscillator, and the antenna connecting section structure is perpendicular to the main body of the symmetrical oscillator, forming two integral parts up and down, forming a new antenna structure unit , to strengthen the electromagnetic coupling between the symmetric oscillators.

The excitation position of the present invention is the same as that of the traditional symmetrical vibrator, which are both between the upper and lower arms of the vibrator antenna. Moreover, the amplitude and phase pattern of a single unit of the four-element symmetrical dipole ring array vary greatly with the distance between the upper and lower antenna connection sections of the symmetrical dipole. Large, the change of amplitude and phase becomes slower and slower with the change of observation angle. It is necessary to apply the full-wave electromagnetic simulation based on the active unit to scan the parameters to search for the optimal distance between the upper and lower antenna connection sections of the symmetrical oscillator, so that the antenna The electromagnetic coupling between the elements is the strongest, and the energy is mainly electromagnetically coupled to other element directions.

The gain of the directly connected symmetric dipole array is significantly enhanced compared with the non-directly connected situation, the actual gain of the antenna unit is significantly improved, and the directionality is stronger, and the change of the gain is more drastic under different observation angles, that is, to increase the unit gain and the sensitivity of the phase difference to the arrival angle of the target signal. In the entire range of azimuth angle variation, the symmetry of the electrically small-pitch four-element direct-connected symmetrical dipole circular ring array antenna will cause the CRB of the direction estimation of the incoming wave arrival angle to be much lower than that of the non-direct connection case, that is, the direction-finding accuracy has a significant improvement.

The advantages and positive effects of the present invention are: this topology antenna array, that is, the interconnection structure between the units, can increase the electromagnetic coupling between the units, improve the variation between the pattern amplitude and the phase difference between the units, and thus Improve the sensitivity of the antenna array element to the incoming wave direction of the target signal, thereby improving the direction finding accuracy.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the front view of the embodiment of the present invention.

Fig. 2 is a top view structural diagram of an embodiment of the present invention.

Fig. 3 is a comparison of the _S11 parameters of the embodiment for different vertical distances between the symmetrical vibrator and when the diameter of the vibrator is 0.1λ.

FIG. 4 is a comparison of the amplitudes of the antenna unit 1 when the vibrator diameter is 0.1λ with a symmetrical vibrator spaced apart from top to bottom according to an embodiment of the present invention.

FIG. 5 is a comparison of the phase pattern diagrams of the antenna unit 1 when the symmetrical dipoles are spaced vertically apart and the diameter of the dipole is 0.1λ according to the embodiment of the present invention.

Fig. 6 is a comparison of the S parameters of an antenna array with the same parameters but not directly connected in consideration of electromagnetic coupling when the diameter of the vibrator is 0.1λ according to the embodiment of the present invention.

FIG. 7 is a directional diagram of the antenna unit 1 when the dipole diameter is 0.1λ according to the embodiment of the present invention.

Fig. 8 shows the phase difference change when the vibrator diameter is 0.1λ according to the embodiment of the present invention

Figure 9 shows the embodiment of the present invention when the vibrator diameter is 0.1λ, the signal-to-noise ratio SNR=15dB, the sampling frequency is three times the operating frequency, that is, f _s =3f ₀ , and the number of snapshots K=300 is not directly related to the consideration of electromagnetic coupling Comparison chart of mean square error of DOA for sub-Monte Carlo simulation of the same parameter antenna array.

Fig. 10 is a schematic perspective view of the three-dimensional structure of the embodiment of the present invention.

Detailed ways

The present invention provides an electrically small-pitch symmetric dipole array antenna structure based on dipole interconnection. In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. The specific implementation steps are as follows:

1) Take the symmetric dipole array antenna with a diameter of 0.1λ as an example

2) Its parameters are set so that the unit antenna is in the xOy plane, as shown in Figure 1, four symmetrical oscillator structure antennas with the same material and size: antenna unit 1, antenna unit 2, antenna unit 3, and antenna unit 4 are at the origin As the center of the circle, the operating frequency is 1GHz, and the corresponding diameter is 0.1 times the wavelength, that is, Φ _ARRAY = 0.1λ = 30mm Arranged on a circle, the vibrator radius R = 0.05λ = 1.5mm; the length of the four vibrators is determined by the half-wave symmetrical vibrator The basic model is optimized to obtain L = 69mm; the port of each unit is loaded with an impedance of 73.2Ω, which is equivalent to the load.

3) The structure of the antenna connection section is that the upper half of the four symmetrical vibrator structures are directly connected using the antenna connection section structure, and the lower half is directly connected using the same antenna connection section structure. The antenna connection section structure is arranged in a regular quadrilateral; the antenna connection section The structure and the symmetrical vibrator use the same metal material with the same diameter. The front view, top view and perspective view of the structural diagram of the symmetric dipole array antenna interconnected by dipoles are shown in Figures 1, 2 and 10.

4) Within a certain parameter range, the electromagnetic simulation based on the active unit is used to scan the parameters to search for the optimal distance ph between the antenna connecting section structure and the feeding point, and the distance between the upper and lower antenna connecting section structures of the symmetrical vibrator is The distance is twice the distance between the antenna connection section structure and the feed point, which is 2×ph. As shown in Figure 3, the change of the S ₁₁ parameter of the four-element symmetrical oscillator circular array with a diameter of 0.1λ with the distance between the antenna connection section structure and the feeding point is obtained. It can be concluded that the same as the linear array, the greater the distance between the connecting section structure of the symmetrical dipole antenna and the feeding point, the more the port resonance characteristics of the antenna unit will shift to high frequencies, and the resonance characteristics will be worse. In the entire observed frequency range, the overall decrease of S ₁₁ parameters is more obvious. As shown in Figures 4 and 5, the amplitude and phase patterns of the four-element symmetrical vibrator circular array antenna unit 1 with a diameter of 0.1λ vary with the distance ph between the connecting section structure of the symmetrical vibrating antenna and the feeding point. It can be seen that The amplitude and phase vary greatly with the distance ph between the connecting section structure of the symmetrical dipole antenna and the feeding point, but the trend of the two changes is consistent. The amplitude and phase changes more and more slowly. The maximum radiation direction of the antenna unit 1 is , which verifies that the electromagnetic coupling between the antenna units is very strong, and the energy is mainly electromagnetically coupled to other unit directions. It can be seen from the above that the distance between the optimal symmetrical dipole antenna connection section structure and the feed point is ph=3mm, that is, the distance between the upper and lower antenna connection section structures of the symmetrical element is 2×ph=6mm.

5) Compared with the traditional non-directly connected four-unit symmetrical oscillator, Figure 6 can be obtained, that is, the S-parameter comparison diagram of the direct-connected four-unit symmetrical oscillator circular array considering electromagnetic coupling and the same parameter antenna array not directly connected considering electromagnetic coupling . Considering the symmetry of the array, only the interaction between antenna unit 1, antenna unit 2 and antenna unit 3 is discussed here. As shown in FIG. 6 , at a working frequency of 1 GHz, the S ₃₁ of the antenna elements is less than -10 dB, and the impedance matching characteristics of the array elements are better than those of non-direct connections. However, S ₂₁ is about -8dB, and S ₃₁ is less than -15dB, indicating that there is a certain degree of energy electromagnetic coupling between adjacent antenna ports, but the energy electromagnetic coupling between non-adjacent units is not obvious.

6) Compared with the traditional non-directly connected four-element symmetric dipole, Figure 7 can be obtained, that is, the actual gain of the four-element direct-connected symmetric dipole array antenna unit 1 with small electrical spacing. It can be seen that the gain of the directly connected symmetric dipole array is significantly enhanced compared with the non-directly connected situation, and the actual gain of the antenna unit is increased by about 5dB, and the directivity is stronger, and the change of the gain is more drastic.

7) Compared with the traditional non-directly connected four-element symmetric dipole, the phase difference change of the four-element electrically small-pitch direct-connected symmetric dipole array antenna can be obtained as shown in FIG. 8 . Wherein, Φ ₂₁ represents the phase difference between the unit antenna unit 1 and the antenna unit 2, and Φ ₃₁ represents the phase difference between the unit antenna unit 1 and the antenna unit 3. In the case of indirect electromagnetic coupling, the range of phase difference between unit antenna unit 1 and antenna unit 2 is 90°, while in the case of direct electromagnetic coupling, the range of phase difference between unit antenna unit 1 and antenna unit 2 is 140° °. In the case of indirect electromagnetic coupling, the range of phase difference between unit antenna unit 1 and antenna unit 3 is 124°, while in the case of direct electromagnetic coupling, the range of phase difference between unit antenna unit 1 and antenna unit 3 is 150° °. It can be concluded that the direct electromagnetic coupling has a larger phase difference between the antenna elements than the non-direct connection, which improves the sensitivity of the entire antenna array to the incoming wave direction of the target signal.

8) Compared with the traditional non-directly connected four-unit symmetric oscillator, the Cramereau boundary for the estimation of the arrival angle direction of the four-unit electrically small spacing can be obtained as shown in Figure 9 and the multiple signal classification algorithm (Multiple Signal Classification Method, MUSIC ) The mean square error of the incoming wave arrival angle direction estimate. It can be seen that within the entire range of azimuth angle variation, the mean square error of the CRB with a diameter of 0.1λ four-element direct-connected symmetrical oscillator circular array and the direction estimation of the incoming wave arrival angle using the MUSIC algorithm is much lower than that of the non-directly connected case. It is caused by the symmetry of the antenna of the four-element symmetric dipole array with electrically small spacing. In the case of indirect electromagnetic coupling, the direction finding accuracy of the array is 0.38°. In contrast, the direction-finding accuracy of the direct-connected electromagnetically coupled four-element circular array is 0.25° within the entire observation angle range, which indicates that the direction-finding accuracy of the antenna array has been improved.

Claims (1)

1. A four-element interconnected symmetrical oscillator circular antenna array for direction finding with small electrical spacing, which is characterized in that it includes 4 symmetrical oscillator structure antennas and 2 antenna connection section structures; The four symmetrical oscillator structure antennas are evenly arranged in a circular array, wherein the upper and lower structures of the four symmetrical oscillators are directly connected by the antenna connection section structure, and the electrically small spacing means that the distance between adjacent units is far Smaller than the working wavelength, the radiating unit includes 4 symmetrical oscillator structures of the same material and size, which are placed in parallel on the same reference plane, and are arranged at equal angular intervals in a circular array; the antenna connection section structure is 4 symmetrical oscillators The upper part of the structure is directly connected with the antenna connection section structure, and the lower part is directly connected with the same antenna connection section structure. The antenna connection section structure is a connection structure formed by connecting four cylinder structures according to a regular quadrilateral; the antenna connection section structure and The symmetrical vibrator uses the same metal material with the same diameter; The antenna connecting section structure is respectively located at the metal ends of the upper and lower parts of the four symmetrical oscillators, which are closest to the middle of the symmetrical oscillator, and the antenna connecting section structure is perpendicular to the main body of the symmetrical oscillator, forming two integral parts up and down, forming a new antenna structure unit , to strengthen the electromagnetic coupling between the symmetric oscillators.