Tight coupling dipole antenna array loaded with log-periodic oscillators

Abstract

The tight coupling dipole antenna array comprises four metal layers and dielectric substrates among the metal layers, the first metal layer and the second metal layer are provided with tight coupling dipole radiation patches, each tight coupling dipole radiation patch is connected with an auxiliary log-periodic dipole oscillator arm, and the auxiliary log-periodic dipole oscillator arms are connected with the dielectric substrates. The radiation patches and the oscillator arms on the two metal layers are arranged in a manner of rotational symmetry about the center line of the antenna array element, the radiation patches of the adjacent antenna array elements are overlapped, and equivalent capacitance is introduced in a coupling manner; the third metal layer and the fourth metal layer are located between the first metal layer and the second metal layer and provided with a balanced feed balun, and impedance conversion and reverse feed direction are achieved through microstrip line-to-dielectric double lines with gradually-changed ground. According to the invention, the expected ultra-wideband radiation characteristic is realized through cooperation of the tight coupling dipole radiation patch and the auxiliary log-periodic dipole oscillator arms, additional structures such as a wide-angle matching layer or a frequency selection surface are prevented from being used, and the design cost and the implementation cost are reduced.

Description

Technical Field

[0001] The invention belongs to the field of radar and communication technology, and in particular relates to a tightly coupled antenna array. Background Art

[0002] Based on the need for electromagnetic spectrum perception and control, it is necessary to effectively perceive and analyze microwave signals to achieve signal detection, perception, analysis, identification, effective regulation, control and countermeasures. Microwave frequency bands below 18 GHz are widely used in wireless communications, satellite communications, radar, detection and imaging, and the relevant spectrum utilization is complex. In order to achieve full-band microwave signal detection below 18 GHz, this requires the antenna front end to achieve as wide a band coverage as possible. Usually, the frequency band below 18 GHz is divided into two bands: 0.2-2 GHz and 2-18 GHz, and the corresponding octaves are usually more than 9. This frequency band division method can achieve efficient system integration, but it places extremely high demands on the design of related devices. In order to achieve the required ultra-wideband design, commonly used antenna solutions include biconical antennas, spiral antennas, logarithmic periodic antennas, etc. designed based on non-frequency-variant antenna theory, Vivaldi antennas designed based on gradient theory, multimode antennas designed based on multimode theory, and tightly coupled antennas designed based on tight coupling theory, etc. The electrical properties (such as impedance, radiation pattern, gain, etc.) of antennas designed based on the theory of non-frequency-variant antennas hardly change with frequency. At each frequency point, there is an antenna module that can achieve radiation. The radiation pattern is relatively stable within the operating frequency. However, these antennas are usually designed according to the lowest frequency. This makes it difficult to form an array with a small spacing between array elements, which has limitations in practical applications. The design of the Vivaldi antenna is based on a gradient slot line, and the width of its radiation arm gradually increases along the length of the antenna. This gradient structure allows electromagnetic waves to gradually release energy during transmission, thereby achieving efficient radiation and having broadband impedance matching characteristics. However, it has the same problem as antennas designed based on the theory of non-frequency-variant antennas. The size of the Vivaldi antenna is limited. The size is very large, which makes it difficult to form an array with a small spacing between array elements, and its gradient slot line requires a long transformation length, which makes the Vivaldi antenna usually have a higher profile. At the same time, the structural characteristics of the Vivaldi antenna also limit the design of dual-polarization antennas, which has limitations in practical applications; multi-mode antennas are special antennas designed based on multi-mode theory. They can support multiple radiation modes in the same structure, thereby realizing multi-band, multi-polarization or multi-function operation, but in order to achieve multi-mode operation, their design and manufacturing complexity is generally high, and the operating frequencies of multiple modes do not necessarily overlap. They are often used in dual-band or multi-band antenna designs. The directional patterns of multiple modes are usually not consistent, which limits the application of multi-mode antennas in the ultra-wideband field. Tightly coupled antennas have gained widespread attention in the field of ultra-wideband antennas with their compact array form, relatively simple antenna design, and broadband impedance matching characteristics.

[0003] The tightly coupled antenna array is an antenna technology that achieves broadband matching and efficient radiation by closely arranging multiple antenna units and utilizing electromagnetic coupling between antenna units. It has a very large impedance bandwidth characteristic. This design originated from Huygens' continuous patch array theory. By introducing a parasitic capacitance generated by an additional mutual coupling between antenna units to offset the input inductance introduced by the array, the impedance of each unit in the array can remain stable over a very wide frequency band and angle range. Compared with traditional microstrip patch antennas, the unit spacing is smaller and a continuous current distribution can be formed. Compared with traditional antenna arrays, the compact design of the tightly coupled antenna array significantly reduces the size and reduces the manufacturing cost. By optimizing the coupling characteristics between antenna units, interference can also be effectively suppressed and communication quality can be improved.

[0004] There are many design difficulties in the design and implementation of tightly coupled antenna arrays, such as: 1. The core design idea of ​​tightly coupled antenna arrays is to use the strong coupling effect between antenna units to expand the bandwidth of the frequency band. However, the small unit spacing leads to a strong mutual coupling effect, which affects the impedance characteristics of the antenna unit and makes it difficult to match and adjust the antenna impedance. 2. Broadband antennas need to maintain stable radiation characteristics at different frequencies, but the antenna pattern of tightly coupled antennas may change significantly at high and low frequencies, resulting in reduced beam scanning performance. 3. In order to optimize the impedance characteristics, tightly coupled antenna arrays usually use frequency selective surfaces or wide-angle matching layers as antenna covers to achieve ultra-wideband impedance matching with free space. However, the use of these antenna covering structures may complicate the antenna structure and increase the implementation cost. In addition, non-integrated processing will significantly increase the errors that may occur during installation, affecting the overall performance of the antenna. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a tightly coupled dipole antenna array loaded with logarithmic periodic oscillators, which overcomes the impedance bandwidth problem of existing ultra-wideband phased array antenna arrays and the structural complexity and cost increase caused by the dependence on frequency selective surfaces or wide-angle matching layers.

[0006] Technical solution: To achieve the above-mentioned invention object, the present invention adopts the following technical solution: A tightly coupled dipole antenna array loaded with logarithmic periodic oscillators comprises four metal layers and dielectric substrates between the metal layers, wherein the first metal layer and the second metal layer are provided with tightly coupled dipole radiation patches of the same geometric size which are arranged at equal intervals in one dimension, each tightly coupled dipole radiation patch is connected with an auxiliary logarithmic periodic dipole dipole arm, the radiation patches and dipole arms on the first metal layer and the radiation patches and dipole arms on the second metal layer are arranged in a rotationally symmetrical manner about the center line of the antenna array element, and the radiation patches of adjacent antenna array elements on the first metal layer and the second metal layer overlap, and equivalent capacitance is introduced by coupling; the third metal layer and the fourth metal layer are located between the first metal layer and the second metal layer, and are provided with balanced feeding baluns, and impedance transformation and reversal of feeding direction are realized by using a microstrip line to dielectric double line with a gradient ground.

[0007] Furthermore, the auxiliary logarithmic periodic dipole arm is located at the upper end of the tightly coupled dipole radiation patch, and the lower end of the auxiliary logarithmic periodic dipole arm is the tightly coupled dipole corner; the radiation patches on the first metal layer and the second metal layer are in a segmented form, the first segment is a transition segment from the feed line to the rectangular radiation patch, and the second segment is an extension of the rectangular radiation patch; the overlapping part of the radiation patches on the first metal layer and the second metal layer is located at the end of the rectangular radiation patch.

[0008] Furthermore, the length of the transition section from the first feed line to the rectangular radiation patch does not exceed the rectangular radiation patch, and the length of the tightly coupled dipole radiation patch is not less than the length of the longest group of dipole arms in the auxiliary logarithmic periodic dipole dipole arms.

[0009] Furthermore, the radiating patch on the first metal layer constitutes the right radiating arm of the tightly coupled dipole, and the radiating patch on the second metal layer constitutes the left radiating arm of the tightly coupled dipole; if the first-level dipole arm on the first metal layer constitutes the left dipole arm of the dipole structure, then the first-level dipole arm on the second metal layer constitutes the right dipole arm of the dipole structure, and the second-level dipole arm of the first metal layer constitutes the right dipole arm of the dipole structure, then the second-level dipole arm of the second metal layer constitutes the left dipole arm of the dipole structure.

[0010] Furthermore, the auxiliary logarithmic periodic dipole dipole arms include five groups, the left dipole arms of the first, third and fifth groups of dipole dipole arms are located at the first metal layer, and the right dipole arms are located at the second metal layer; the left dipole arms of the second and fourth groups of dipole dipole arms are located at the second metal layer, and the right dipole arms are located at the first metal layer; the lengths, widths and spacings of the multiple groups of dipole dipole arms gradually increase from the radiation direction to the feeding direction.

[0011] Furthermore, the balanced-fed balun backplane adopts an exponential gradient line structure for impedance matching, and the frequency band covered by the balanced-fed balun is expanded by adjusting the slope of the gradient line.

[0012] Furthermore, the balanced feed balun includes a coaxial joint connection section metal strip, a trapezoidal impedance transformation section, a feed line section, a coaxial joint connection section metal backplane and an exponential impedance transformation section; the feed line section and the exponential impedance transformation section constitute a dielectric double-wire structure; the top of the feed line section is connected to the auxiliary logarithmic periodic dipole oscillator arm through a probe, and the bottom end is connected to the trapezoidal impedance transformation section; the trapezoidal impedance transformation section is connected to the coaxial feed line through the coaxial joint connection section metal strip for feeding; the coaxial joint connection section metal strip adopts a microstrip line structure truncated on the ground.

[0013] Furthermore, the tightly coupled dipole radiating patch and the auxiliary log-periodic dipole arm are reversely fed via a balanced feeding balun and a probe, and the feeding line first passes through the auxiliary log-periodic dipole arm and then feeds to the tightly coupled dipole radiating patch, thereby forming forward unidirectional radiation.

[0014] Furthermore, the feeding probe is located in the dielectric substrate between the first metal layer and the third metal layer, and in the dielectric substrate between the fourth metal layer and the second metal layer, and the current is transmitted reversely to the first metal layer and the second metal layer through the feeding probe, thereby forming the radiation condition of the tightly coupled dipole antenna.

[0015] Furthermore, the tightly coupled dipole antenna array is a one-dimensional linear array, which is processed in subarray units. One end of the subarray is provided with an outwardly extending protrusion matching the tightly coupled dipole radiation patch, and the other end is provided with a recess matching the protrusion.

[0016] Beneficial effects: The present invention provides a tightly coupled dipole antenna array loaded with log-periodic oscillators. The balanced feeding balun adopts a microstrip line with a gradient ground to a dielectric double line to achieve ultra-wideband impedance transformation and reverse the feeding direction. By adjusting the length of the radiating arm and the coupling area between the radiating arms, the parasitic inductance and coupling capacitance characteristics of the antenna can be adjusted to achieve a bandwidth exceeding the length limit of the radiating arm. In the auxiliary log-periodic dipole arm, the free space impedance matching of the tightly coupled dipole antenna array without a wide-angle matching layer is achieved by adjusting the length change of the log-periodic dipole, the dipole spacing, and the longest and shortest dipole arm lengths, and the bandwidth is expanded to high frequencies. Compared with the prior art, the present invention has the following advantages: (1) The present invention proposes a solution for a tightly coupled antenna with a log-periodic structure. Combining the characteristics of a tightly coupled antenna and a log-periodic dipole array, the balanced feeding balun is used to achieve reverse feeding direction, thereby achieving ultra-wideband performance of the antenna and avoiding the use of additional structures such as wide-angle matching layers or frequency selective surfaces, thereby reducing design costs and implementation costs.

[0017] (2) The present invention uses a dipole antenna arm with a logarithmic periodic structure as the upper cover of a tightly coupled dipole antenna, replacing the use of a frequency selective surface to achieve integrated processing. At the same time, the logarithmic periodic dipole radiation arm can be used to expand the bandwidth to high frequencies while maintaining the stability of the radiation pattern, thereby increasing the application range of the antenna.

[0018] (3) The tightly coupled antenna array provided by the present invention has a compact and simple structure. It is easy to manufacture and can be assembled by screwing together, so the production and maintenance costs are low. It is detachable and has a wide range of applications. The array has good stability. The impedance of each unit in the array can remain stable within a very wide frequency band and angle range, thus achieving the wide bandwidth and angle characteristics of the array. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the overall structure stacking of an embodiment of the present invention.

[0020] Figure 2 It is a schematic perspective view from a top view of an embodiment of the present invention.

[0021] Figure 3 It is a schematic diagram of an oblique-angle dissection of an embodiment of the present invention.

[0022] Figure 4 It is an enlarged schematic diagram of a tightly coupled dipole radiation patch in an embodiment of the present invention.

[0023] Figure 5 It is an enlarged schematic diagram of the auxiliary logarithmic periodic dipole vibrator arm in an embodiment of the present invention.

[0024] Figure 6 Schematic diagram of the layering of the auxiliary logarithmic periodic dipole dipole arms in an embodiment of the present invention; (a) is a schematic diagram of the distribution of the dipole arms on the second metal layer; (b) is a schematic diagram of the distribution of the dipole arms on the first metal layer.

[0025] Figure 7 Schematic diagram of the structure of a balanced-feed balun in an embodiment of the present invention; (a) is a schematic diagram of a back panel; (b) is a schematic diagram of a front panel.

[0026] Figure 8 Schematic diagrams of the structures of the metal layers of the one-dimensional subarray example of the present invention; wherein (a) is a schematic diagram of the structure of the first metal layer of the one-dimensional subarray; (b) is a schematic diagram of the structure of the third metal layer of the one-dimensional subarray; (c) is a schematic diagram of the structure of the fourth metal layer of the one-dimensional subarray; and (d) is a schematic diagram of the structure of the second metal layer of the one-dimensional subarray.

[0027] Fig. 9 4 is a comparison diagram of the simulated and measured standing wave curves of an embodiment of the present invention.

[0028] Fig.10The gain curve at 0° on the E-plane for the simulation and measurement comparison of the tightly coupled dipole antenna array with 22 antenna elements.

[0029] Fig.11 The gain curve at 30° on the E-plane for the simulation and measurement comparison of the tightly coupled dipole antenna array with 22 antenna elements.

[0030] Fig.12 The gain curve at 60° on the E-plane for the simulation and measurement comparison of the tightly coupled dipole antenna array with 22 antenna elements.

[0031] In the figure, 1: upper dielectric substrate; 2: middle dielectric substrate; 3: lower dielectric substrate; 4: first metal layer; 5: second metal layer; 6: third metal layer; 7: fourth metal layer; 8: balanced feed balun; 9: tightly coupled dipole radiation patch; 10: auxiliary logarithmic periodic dipole arm; 11: tightly coupled dipole corner; 12: overlap of radiation patch; 13: transition section of rectangular radiation patch; 14: rectangular radiation patch; 15: first group of dipole arms; 16: second group of dipole arms; 17: third group of dipole Sub-dipolar arm; 18: the fourth group of dipole dipole arms; 19: the fifth group of dipole dipole arms; 15-2, 16-1, 17-2, 18-1, 19-2: the left dipole arms of the first to fifth groups of dipole dipole arms; 15-1, 16-2, 17-1, 18-2, 19-1: the right dipole arms of the first to fifth groups of dipole dipole arms; 20: the metal strip of the coaxial connector connection section; 21: the trapezoidal impedance transformation section; 22: the feeder section; 23: the probe; 24: the metal back plate of the coaxial connector connection section; 25: the exponential impedance transformation section. DETAILED DESCRIPTION

[0032] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0033] The embodiment of the present invention discloses a tightly coupled dipole antenna array loaded with logarithmic periodic dipoles, which is mainly composed of a balanced feeding balun, a tightly coupled dipole radiation patch and auxiliary logarithmic periodic dipole dipole arms. The structure includes four metal layers and a dielectric substrate between the metal layers. The first metal layer and the second metal layer are provided with tightly coupled dipole radiation patches of the same geometric size arranged at equal intervals in one dimension. Each tightly coupled dipole radiation patch is connected to an auxiliary logarithmic periodic dipole dipole arm. The radiation patches and dipole arms on the first metal layer and the radiation patches and dipole arms on the second metal layer are arranged in a rotationally symmetrical manner about the center line of the antenna array element. The radiation patches on the first metal layer and the second metal layer of adjacent antenna array elements overlap. Equivalent capacitance is introduced by coupling to offset the inductance introduced by itself, so that it can work over a very wide frequency band. The third metal layer and the fourth metal layer are located between the first metal layer and the second metal layer, and are provided with a balanced feed balun. The balanced feed balun adopts a microstrip line with a gradient ground to a dielectric double line to achieve impedance transformation and reversal of the feeding direction.

[0034] Figures 1 to 3 A specific form of a tightly coupled dipole antenna array loaded with logarithmic periodic oscillators is given. Figure 1 As shown, the main structure of the antenna array includes an upper dielectric substrate 1, a middle dielectric substrate 2 and a lower dielectric substrate 3. The upper surface of the upper dielectric substrate 1 is provided with a first metal layer 4, the lower surface of the lower dielectric substrate 3 is provided with a second metal layer 5, and the upper surface and the lower surface of the middle dielectric substrate 2 are respectively provided with a third metal layer 6 and a fourth metal layer 7. In this embodiment, the antenna circuit is processed by a traditional PCB process, the metal layer on the dielectric substrate is copper, the copper layer thickness is 35μm, and the dielectric substrates are all Rogers 4003 with a thickness of 1mm and a dielectric constant of 3.55.

[0035] like Figure 2 and Figure 3As shown, the first metal layer 4 and the second metal layer 5 are provided with a one-dimensional tightly coupled dipole antenna array composed of a plurality of tightly coupled dipole radiating patches 9 of the same geometric size arranged in one dimension at equal intervals. The arrangement of the radiating patches on the first metal layer 4 and the radiating patches on the second metal layer 5 is symmetrical when the center line of the antenna array element is rotated 180 degrees. The radiating patches on the first metal layer 4 constitute the right radiating arm of the tightly coupled dipole, and the radiating patches on the second metal layer 5 constitute the left radiating arm of the tightly coupled dipole. The first metal layer 4 and the second metal layer 5 are provided with an auxiliary logarithmic periodic dipole matching radiating array composed of auxiliary logarithmic periodic dipole dipole arms 10. The arrangement of the dipole arms on the first metal layer 4 and the dipole arms on the second metal layer 5 is symmetrical when the center line of the antenna array element is rotated 180 degrees, and they are arranged in a staggered manner. For example, if the first-level dipole arm on the first metal layer 4 constitutes the left dipole arm of the dipole structure, then the first-level dipole arm on the second metal layer 5 constitutes the right dipole arm of the dipole structure, and the second-level dipole arm on the first metal layer 4 constitutes the right dipole arm of the dipole structure, then the second-level dipole arm on the second metal layer 5 constitutes the left dipole arm of the dipole structure, and so on. Each array unit of the first metal layer 4 and the second metal layer 5 has the same dipole arm placement position and placement form. A balanced feeding balun 8 is provided in the third metal layer 6 and the fourth metal layer 7, one end of which is directly connected to the coaxial joint connector, and the other end feeds the radiation patch by means of a probe.

[0036] like Figure 4 As shown, the main structure of the antenna array is a tightly coupled dipole radiating patch 9, and the auxiliary logarithmic periodic dipole arm 10 realizes ultra-wideband matching and is located at the upper end of the tightly coupled dipole radiating patch 9. The lower end of the auxiliary logarithmic periodic dipole arm 10 is a tightly coupled dipole corner 11. The tightly coupled dipole radiating patch 9 is essentially a dipole antenna, which introduces an equivalent capacitance between it and the adjacent dipoles through strong coupling to offset the inductance introduced by itself, so that it can work over a very wide frequency band. The radiating patch is in a segmented form, the first section is a transition section 13 from the feed line to the rectangular radiating patch, and the second section is an extension of the rectangular radiating patch 14; the overlap 12 of the radiating patches on the first metal layer 4 and the second metal layer 5 is located at the end of the rectangular radiating patch 14. The length of the transition section 13 from the feed line to the rectangular radiation patch should not exceed half of the overall radiation patch, so as not to affect the distribution of the low-frequency radiation current element; the width of the tightly coupled dipole radiation patch 9 should not be less than the width of the longest arm of the auxiliary logarithmic periodic dipole dipole arm 10; the length of the tightly coupled dipole radiation patch 9 should not be less than the length of the longest arm of the auxiliary logarithmic periodic dipole dipole arm 10. The coupling length of the tightly coupled dipole radiation patch 9 affects the low-frequency performance of the antenna array, and the tightly coupled dipole antenna of this embodiment does not need to use a reflective backplane.

[0037] The main structure of the auxiliary logarithmic periodic dipole matching radiation array is a dipole arm with a logarithmic periodic topological structure transformation. The rear end of the intermediate feeder extends outward to form an extension body, and the extension body and the logarithmic periodic dipole form a logarithmic periodic dipole end-fire radiator. The length of multiple groups of dipole arms of the auxiliary logarithmic periodic dipole arm 10 gradually increases from front to back, the width of multiple groups of dipole arms gradually increases from front to back, and the distance between adjacent dipole arms gradually increases from front to back. In the specific design, the length, width and adjacent spacing of the auxiliary logarithmic periodic dipole arm 10 can satisfy the following relationship:

[0038] in, τ It represents the scale factor, which represents the degree of scaling of the logarithmic period; l n , l n+1 Respectively represent the length of the nth and n+1th level oscillator arms, 1≤n≤N-1, N is the number of oscillator arms; w n , w n+1 Respectively represent the width of the nth and n+1th level oscillator arms, 1≤n≤N-1; s n , s n+1 They respectively represent the distances between the nth and n+1th level vibrator arms and between the n+1th and n+2th level vibrator arms, 1≤n≤N-2.

[0039] like Figure 5 and Figure 6As shown, illustratively, the auxiliary logarithmic periodic dipole arms 10 include five groups, namely a first group of dipole arms 15 , a second group of dipole arms 16 , a third group of dipole arms 17 , a fourth group of dipole arms 18 and a fifth group of dipole arms 19 . The left dipole arm 15-2 of the first group of dipole dipole arms 15 is located at the first metal layer 4, and the right dipole arm 15-1 is located at the second metal layer 5; the left dipole arm 16-1 of the second group of dipole dipole arms 16 is located at the second metal layer 5, and the right dipole arm 16-2 is located at the first metal layer 4; the left dipole arm 17-2 of the third group of dipole dipole arms 17 is located at the first metal layer 4, and the right dipole arm 17-1 is located at the second metal layer 5; the left dipole arm 18-1 of the fourth group of dipole dipole arms 18 is located at the second metal layer 5, and the right dipole arm 18-2 is located at the first metal layer 4; the left dipole arm 19-2 of the fifth group of dipole dipole arms 19 is located at the first metal layer 4, and the right dipole arm 19-1 is located at the second metal layer 5. In this embodiment, the auxiliary logarithmic periodic dipole dipole arms 10 are staggered to establish relatively symmetrical boundary conditions to ensure the balance of the radiation pattern and ensure that adjacent dipole units have a 180° phase offset to minimize interference between them. The shorter end of the auxiliary logarithmic periodic dipole dipole arm 10 is located in the radiation direction, and the longer end of the dipole arm is located in the feeding direction, and the feeding current is fed from the shorter end of the dipole arm instead of from the longer end of the dipole arm.

[0040] like Figure 7 As shown, the balanced feeding balun 8 includes a coaxial joint connection section metal strip 20, a trapezoidal impedance transformation section 21, a feed line section 22, a coaxial joint connection section metal back plate 24, and an exponential impedance transformation section 25, wherein the feed line section 22 and the exponential impedance transformation section 25 form a dielectric double-line structure. The top of the feed line section 22 is connected to the auxiliary logarithmic periodic dipole oscillator arm 10 through a probe 23, and the bottom is connected to the trapezoidal impedance transformation section 21; the trapezoidal impedance transformation section 21 is connected to the coaxial feed line through the coaxial joint connection section metal strip 20 for feeding. The feed joint is a coaxial feeding port, and the feed joint can be directly fixed on the middle-layer dielectric substrate 2 by threaded fixing. The coaxial joint connection section metal strip 20 adopts a ground-cut microstrip line structure, and the trapezoidal impedance transformation section 21 is not a complete microstrip line structure. In this embodiment, the backplane adopts an exponential gradient line structure for impedance matching, and the front plate adopts a trapezoidal impedance transformation structure. The exponential gradient line structure adjusts the slope of the gradient line so that the balanced feed balun 8 can cover an ultra-wide frequency band. Specifically, the balanced feed balun 8 gradually changes the characteristic impedance along the length of the transmission line, and its characteristic impedance changes according to an exponential law along the length of the transmission line:

[0041] in, Z ( z) is the characteristic impedance of the transmission line at position z; Z 0 is the start of the transmission line ( z =0) characteristic impedance; z is the distance along the length of the transmission line; δ is the impedance variation coefficient, which determines the rate at which the characteristic impedance changes and can be determined by the following formula:

[0042] in, L is the total length of the transmission line; Z L is the end of the transmission line ( z = L )’s characteristic impedance; In Represents the natural logarithm.

[0043] In this embodiment, the balanced feeding balun 8 provided on the middle dielectric substrate 2 transmits the current of the dielectric double-wire structure in reverse to the first metal layer 4 and the second metal layer 5 through the probe 23, thereby forming the radiation condition of the tightly coupled dipole antenna. The feeding probe 23 is located in the dielectric of the upper dielectric substrate 1 and the lower dielectric substrate 3. The middle dielectric substrate 2 is a transmission layer, and the feed line of this layer in the antenna part is a dielectric double-wire structure. After matching through the balanced feeding balun 8, the double-wire currents are equal in amplitude and opposite in phase, thereby constructing the current condition of the radiation units of the upper and lower dielectric substrates. The tightly coupled dipole radiation patch 9 and the auxiliary logarithmic periodic dipole dipole arm 10 are reversely fed through the balanced feeding balun 8 and the probe 23. The feeding feed line first passes through the auxiliary logarithmic periodic dipole dipole arm 10, and then feeds to the tightly coupled dipole radiation patch 9, thereby forming forward unidirectional radiation, so as to ensure that the radiation direction is in the end-fire direction rather than the feeding direction.

[0044] like Figure 8 (a), (b), (c), and (d) are schematic diagrams of the metal layer structures of the one-dimensional linear array. The antenna array is processed in subarray units. One end of the subarray is provided with an outwardly extending protrusion that matches the tightly coupled dipole radiation patch, and the other end is provided with a recessed portion that matches the protrusion. The subarray in the figure is composed of 8 antenna units. After the subarray is processed, nylon screws are passed through the fixing holes to fix the three dielectric substrates. At the same time, the extended fixing structures on both sides can extend the subarray to realize the assembly of antennas with 8 times the number of array units.

[0045] The effect of the present invention is described below with reference to a specific design example of a tightly coupled dipole antenna array loaded with logarithmic periodic oscillators. In this design example, the antenna array element spacing is set to 24.4 mm, the fixing screw hole spacing is 24.4 mm, the aperture is 2 mm, and the overall antenna height is 32 mm. The design operating frequency is between 2 and 18 GHz, and the lengths of the auxiliary logarithmic periodic dipole arms are determined to be 2.2 mm, 3.2 mm, 4 mm, 6.2 mm, and 7 mm from top to bottom; the widths of the auxiliary logarithmic periodic dipole arms are determined to be 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and 1 mm from top to bottom; the length of the tightly coupled dipole radiation patch is 13 mm, of which the length of the gradient transition section is 5.7 mm, the width of the rectangular radiation patch is 2 mm, and the patch overlap length is 4 mm; in the balanced feed balun, the starting width of the metal strip line on the front plate is 2.1 mm, which is transformed into a metal strip line with a length of 14.42 mm and a width of 1.1 mm through a trapezoidal transformation of 4.5 mm, while the starting width of the metal back plate is 10 mm, which is transformed into a metal strip line with a length of 5.72 mm and a width of 1.1 mm through an exponential gradient transformation of 13.2 mm, and together with the metal strip line on the front plate, it forms a dielectric double-line structure. A transition area is designed for connecting the coaxial feeding port to the SMA connector, and holes are punched according to the corresponding SMA model.

[0046] like Fig. 9 As shown in the figure, a comparison diagram of the standing wave curves of the designed antenna array is given. The solid line is the measured curve, and the dotted line is the simulation curve. It can be seen that the impedance bandwidth of the designed antenna is in the range of 2 GHz to 18 GHz, and the measured standing wave coefficient is consistent with the simulated standing wave coefficient. The impedance bandwidth of the designed antenna can cover 2 GHz to 18 GHz, satisfying the standing wave coefficient VSWR less than 3.

[0047] like Fig.10 As shown, the main polarization gain curve and comparison diagram of the designed antenna array in the 0° direction of the E plane are given. The number of array units is 22. The solid line is the measured curve, and the dotted line is the simulation curve. It can be seen that the measured gain of the designed antenna is consistent with the simulated gain in the range of 2GHz to 18GHz.

[0048] like Fig.11 As shown, the main polarization gain curve and comparison diagram of the designed antenna array in the 30° direction of the E plane are given. The number of array units is 22. The solid line is the measured curve, and the dotted line is the simulation curve. It can be seen that the measured gain of the designed antenna is consistent with the simulated gain in the range of 2GHz to 18GHz.

[0049] like Fig.12As shown, the main polarization gain curve and comparison diagram of the designed antenna array in the 60° direction of the E plane are given. The number of array units is 22. The solid line is the measured curve, and the dotted line is the simulation curve. It can be seen that the measured gain of the designed antenna is consistent with the simulated gain in the range of 2GHz to 18GHz.

[0050] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present invention should be the common meanings understood by technicians in the field to which the present invention belongs. It should be understood that the orientation or positional relationship indicated by the terms upper, lower, front, back, etc. is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms first, second, etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. In the description of the present invention, the meaning of multiple is more than two, unless otherwise clearly specified and defined; unless otherwise clearly specified and defined, the terms connected, connected, etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents, and these modifications or replacements do not make the corresponding technical solutions essentially deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A tightly coupled dipole antenna array loaded with logarithmic periodic oscillators, characterized in that: The invention comprises four metal layers and a dielectric substrate between the metal layers. The first metal layer and the second metal layer are provided with tightly coupled dipole radiation patches of the same geometric size arranged at equal intervals in one dimension. Each tightly coupled dipole radiation patch is connected with an auxiliary logarithmic periodic dipole dipole arm. The radiation patches and dipole arms on the first metal layer and the radiation patches and dipole arms on the second metal layer are arranged in a rotationally symmetrical manner about the center line of the antenna array element. The radiation patches of adjacent antenna array elements on the first metal layer and the second metal layer overlap, and an equivalent capacitance is introduced by coupling. The third metal layer and the fourth metal layer are located between the first metal layer and the second metal layer, and are provided with a balanced feeding balun. A microstrip line with a gradient ground is used to convert the dielectric double line to realize impedance transformation and reversal of the feeding direction.

2. A tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 1, characterized in that: The auxiliary logarithmic periodic dipole arm is located at the upper end of the tightly coupled dipole radiation patch, and the lower end of the auxiliary logarithmic periodic dipole arm is the tightly coupled dipole corner; the radiation patches on the first metal layer and the second metal layer are in segmented form, the first segment is the transition segment from the feed line to the rectangular radiation patch, and the second segment is the extension of the rectangular radiation patch; the overlapping part of the radiation patches on the first metal layer and the second metal layer is located at the end of the rectangular radiation patch.

3. A tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 2, characterized in that: The length of the transition section from the first section of the feed line to the rectangular radiation patch does not exceed the rectangular radiation patch, and the length of the tightly coupled dipole radiation patch is not less than the length of the longest group of dipole arms in the auxiliary logarithmic periodic dipole dipole arms.

4. The tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 1, characterized in that: The radiating patch on the first metal layer constitutes the right radiating arm of the tightly coupled dipole, and the radiating patch on the second metal layer constitutes the left radiating arm of the tightly coupled dipole; if the first-level dipole arm on the first metal layer constitutes the left dipole arm of the dipole structure, then the first-level dipole arm on the second metal layer constitutes the right dipole arm of the dipole structure, and the second-level dipole arm on the first metal layer constitutes the right dipole arm of the dipole structure, then the second-level dipole arm on the second metal layer constitutes the left dipole arm of the dipole structure.

5. The tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 1, characterized in that: The auxiliary logarithmic periodic dipole dipole arms include five groups. The left dipole arms of the first, third and fifth groups of dipole dipole arms are located at the first metal layer, and the right dipole arms are located at the second metal layer; the left dipole arms of the second and fourth groups of dipole dipole arms are located at the second metal layer, and the right dipole arms are located at the first metal layer; the lengths, widths and spacings of the multiple groups of dipole dipole arms gradually increase from the radiation direction to the feeding direction.

6. The tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 1, characterized in that: The balanced-fed balun backplane adopts an exponential gradient line structure to achieve impedance matching. By adjusting the slope of the gradient line, the frequency band covered by the balanced-fed balun is expanded.

7. The tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 1, characterized in that: The balanced feeding balun includes a coaxial joint connection section metal strip, a trapezoidal impedance transformation section, a feed line section, a coaxial joint connection section metal back plate and an exponential impedance transformation section; the feed line section and the exponential impedance transformation section form a dielectric double-wire structure; the top of the feed line section is connected to the auxiliary logarithmic periodic dipole oscillator arm through a probe, and the bottom end is connected to the trapezoidal impedance transformation section; the trapezoidal impedance transformation section is connected to the coaxial feed line through the coaxial joint connection section metal strip for feeding; the coaxial joint connection section metal strip adopts a ground-cut microstrip line structure.

8. The tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 1, characterized in that: The tightly coupled dipole radiating patch and the auxiliary logarithmic periodic dipole oscillator arm are reversely fed through a balanced feeding balun and a probe. The feeding line first passes through the auxiliary logarithmic periodic dipole oscillator arm and then feeds to the tightly coupled dipole radiating patch, forming forward unidirectional radiation.

9. The tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 8, characterized in that: The feeding probe is located in the dielectric substrate between the first metal layer and the third metal layer, and in the dielectric substrate between the fourth metal layer and the second metal layer. The current is transmitted reversely to the first metal layer and the second metal layer through the feeding probe, forming the radiation condition of the tightly coupled dipole antenna.

10. The tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 1, characterized in that: The tightly coupled dipole antenna array is a one-dimensional linear array, which is processed in subarray units. One end of the subarray is provided with an outwardly extending protrusion matching the tightly coupled dipole radiation patch, and the other end is provided with a recess matching the protrusion.

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