A tightly coupled dipole antenna array loaded with log-periodic dipoles

Abstract

The present invention discloses a tightly coupled dipole antenna array loaded with log-periodic dipoles, which includes four metal layers and dielectric substrates between the metal layers. The first and second metal layers are provided with tightly coupled dipole radiation patches, and each tightly coupled dipole radiation patch is connected with an auxiliary log-periodic dipole oscillator arm. The arrangement of the radiation patches and oscillator arms on the two metal layers is rotationally symmetric about the center line of the antenna element, and there is an overlap between the radiation patches of adjacent antenna elements, and an equivalent capacitance is introduced through the coupling method. The third and fourth metal layers are located between the first and second metal layers and are provided with a balanced feed balun. The impedance transformation and the reversal of the feed direction are realized by using a microstrip line with a tapered ground to a dielectric twin line. The present invention realizes the desired ultra-wideband radiation characteristics through the cooperation of the tightly coupled dipole radiation patches and the auxiliary log-periodic dipole oscillator arms, avoiding the use of additional structures such as wide-angle matching layers or frequency selective surfaces, and reducing the design cost and implementation cost.

Description

Technical Field

[0001] The present invention belongs to the technical fields of radar and communication, and particularly relates to a tightly coupled antenna array. Background Art

[0002] Based on the requirements for electromagnetic spectrum sensing and management and control, it is necessary to effectively sense and analyze microwave signals to achieve signal detection, sensing, analysis, identification, and effective regulation, management, and countermeasure. The microwave frequency band below 18 GHz is widely used in applications such as wireless communication, satellite communication, radar, detection, and imaging, and the utilization of the relevant spectrum is complex. In order to achieve the detection of microwave signals in the entire frequency band below 18 GHz, it is required that the antenna front end can achieve as wide a frequency band coverage as possible. Usually, the frequency band below 18 GHz is divided into two frequency bands of 0.2 - 2 GHz and 2 - 18 GHz, and the corresponding octave usually exceeds 9. This frequency band division method can achieve efficient system integration, but it poses extremely high requirements for the design of related devices. To achieve the required ultra-wideband design, common antenna solutions include biconical antennas, helical antennas, log-periodic antennas, etc. designed based on the non-frequency-variable antenna theory, Vivaldi antennas designed based on the gradual change theory, multi-mode antennas designed based on the multi-mode theory, tightly coupled antennas designed based on the tight coupling theory, and so on. For antennas designed based on the non-frequency-variable antenna theory, their electrical properties (such as impedance, radiation pattern, gain, etc.) hardly change with frequency, and there is an antenna module that can achieve radiation corresponding to each frequency point, and the radiation pattern is relatively stable within the operating frequency. However, these antennas usually design the antenna size according to the lowest frequency, which makes it difficult to form an array with a small array element spacing and has limitations in practical applications; the design of Vivaldi antennas is based on a tapered slot line, and the width of its radiation arm gradually increases along the antenna length. This tapered structure enables the electromagnetic wave to gradually release energy during transmission, thereby achieving efficient radiation and having broadband impedance matching characteristics. However, it has the same problem as the antennas designed based on the non-frequency-variable antenna theory. The size of Vivaldi antennas is very large, making it difficult to form an array with a small array element spacing. Moreover, its tapered slot line requires a long transformation length, resulting in Vivaldi antennas usually having a high profile. At the same time, the structural characteristics of Vivaldi antennas also limit the design of dual-polarized antennas and have limitations in practical applications; multi-mode antennas are special antennas designed based on the multi-mode theory, which can support multiple radiation modes in the same structure, thereby achieving multi-band, multi-polarization, or multi-functional operation. However, to achieve multi-mode operation, its design and manufacturing complexity are generally high, and the operating frequencies of multiple modes do not necessarily overlap. It is often used in the design of dual-band or multi-band antennas, and the radiation patterns of multiple modes usually do not coincide, which limits the application of multi-mode antennas in the ultra-wideband field. Tightly coupled antennas have attracted extensive attention in the ultra-wideband antenna field due to their compact array form, relatively simple antenna design, and broadband impedance matching characteristics.

[0003] A tightly coupled antenna array is an antenna technology that realizes broadband matching and efficient radiation by closely arranging multiple antenna elements and utilizing the electromagnetic coupling between the antenna elements, and has excellent impedance bandwidth characteristics. This design originated from the Huygens continuous patch array theory. By introducing a parasitic capacitance generated by an additional mutual coupling between the antenna elements to cancel the input inductance introduced by the array, the impedance of each element in the array can be kept stable within a very wide frequency band and angular range. Compared with traditional microstrip patch antennas, the element spacing is smaller, and a continuous current distribution can be formed. Compared with traditional antenna arrays, the tightly coupled antenna array has a significantly reduced size and lower manufacturing cost due to its compact design. By optimizing the coupling characteristics between the antenna elements, interference can also be effectively suppressed and the communication quality can be improved.

[0004] There are a large number of design difficulties in the design and implementation of tightly coupled antenna arrays. For example: 1. The core design idea of a tightly coupled antenna array is to utilize the strong coupling effect between the antenna elements to expand the bandwidth of the frequency band. However, the small element spacing leads to a strong mutual coupling effect, which affects the impedance characteristics of the antenna elements and makes it difficult to match and adjust the antenna impedance. 2. A broadband antenna needs to maintain stable radiation characteristics at different frequencies. At the high-frequency and low-frequency ends of a tightly coupled antenna, the radiation pattern of the antenna may change significantly, resulting in a decline in beam scanning performance. 3. To optimize the impedance characteristics, a tightly coupled antenna array usually uses a frequency selective surface or a wide-angle matching layer as the antenna cover to achieve ultra-wideband impedance matching with free space. However, using these antenna cover structures may lead to the complexity of the antenna structure, increase the implementation cost, and the non-integrated processing will also significantly increase the installation errors, affecting the overall performance of the antenna. Summary of the Invention

[0005] Object of the Invention: The object of the present invention is to provide a tightly coupled dipole antenna array loaded with log-periodic dipoles, which overcomes the impedance bandwidth problems of existing ultra-wideband phased array antenna arrays and the problems of 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 object of the invention, the present invention adopts the following technical solutions:

[0007] A tightly coupled dipole antenna array loaded with log-periodic dipoles, comprising four metal layers and dielectric substrates between the metal layers. The first metal layer and the second metal layer are provided with tightly coupled dipole radiation patches having the same geometric size arranged at equal intervals in one dimension. Each tightly coupled dipole radiation patch is connected with an auxiliary log-periodic dipole oscillator arm. The arrangement of the radiation patches and oscillator arms on the first metal layer and the radiation patches and oscillator arms on the second metal layer are rotationally symmetric about the center line of the antenna element, and there is an overlap between the radiation patches of adjacent antenna elements on the first metal layer and the second metal layer, and an equivalent capacitance is introduced through the coupling method. 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, and impedance transformation and the reversal of the feed direction are realized by using a microstrip line to dielectric double line with a tapered ground plane.

[0008] Further, the auxiliary log-periodic dipole oscillator arm is located at the upper end of the tightly coupled dipole radiation patch, and the lower end of the auxiliary log-periodic dipole oscillator arm is the corner of the tightly coupled dipole. The radiation patches on the first metal layer and the second metal layer are in a segmented form. The first segment is the transition segment from the feeder 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.

[0009] Further, the length of the transition segment from the first segment of the feeder 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 oscillator arm of the longest group in the auxiliary log-periodic dipole oscillator arm.

[0010] Further, the radiation patch on the first metal layer constitutes the right radiation arm of the tightly coupled dipole, and the radiation patch on the second metal layer constitutes the left radiation arm of the tightly coupled dipole. The first-stage oscillator arm on the first metal layer constitutes the left oscillator arm of the dipole structure, then the first-stage oscillator arm on the second metal layer constitutes the right oscillator arm of the dipole structure. The second-stage oscillator arm on the first metal layer constitutes the right oscillator arm of the dipole structure, then the second-stage oscillator arm on the second metal layer constitutes the left oscillator arm of the dipole structure.

[0011] Further, the auxiliary log-periodic dipole oscillator arm includes five groups. The left oscillator arms of the first, third, and fifth groups of dipole oscillator arms are located on the first metal layer, and the right oscillator arms are located on the second metal layer. The left oscillator arms of the second and fourth groups of dipole oscillator arms are located on the second metal layer, and the right oscillator arms are located on the first metal layer. The lengths, widths, and spacings of the multiple groups of dipole oscillator arms gradually increase from the radiation direction to the feed direction.

[0012] Further, the backplane of the balanced feed balun adopts an exponential tapered line structure for impedance matching, and the coverage frequency band of the balanced feed balun is extended by adjusting the slope of the tapered line.

[0013] Further, the balanced feed balun includes a coaxial connector connection section metal strip, a trapezoidal impedance transformation section, a feed section, a coaxial connector connection section metal backplane, and an exponential impedance transformation section; the feed section and the exponential impedance transformation section form a dielectric twin-wire structure; the top end of the feed section is connected to the auxiliary log-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 fed through the coaxial connector connection section metal strip connected to the coaxial feeder; the coaxial connector connection section metal strip adopts a ground-truncated microstrip line structure.

[0014] Further, the tightly coupled dipole radiation patch and the auxiliary log-periodic dipole oscillator arm are reversely fed through the balanced feed balun and the probe. The feeding feeder first passes through the auxiliary log-periodic dipole oscillator arm and then feeds to the tightly coupled dipole radiation patch to form forward single-directional radiation.

[0015] Further, the feeding probe is located in the dielectric substrates between the first metal layer and the third metal layer, and between the fourth metal layer and the second metal layer. The current is reversely transmitted to the first metal layer and the second metal layer through the feeding probe to constitute the radiation condition of the tightly coupled dipole antenna.

[0016] Further, the tightly coupled dipole antenna array is a one-dimensional linear array, which is processed in units of sub-arrays. One end of the sub-array is provided with a protruding portion extending outward and matching the tightly coupled dipole radiation patch, and the other end is provided with a recessed portion matching the protruding portion.

[0017] Beneficial effects: A tightly coupled dipole antenna array loaded with a log-periodic oscillator provided by the present invention. The balanced feed balun uses a microstrip line with a tapered ground to transform to a dielectric twin-wire to achieve ultra-wideband impedance transformation and reverse the feeding direction. By adjusting the length of the radiation arms and the coupling area between the radiation arms, the parasitic inductance and coupling capacitance characteristics of the antenna can be adjusted to achieve a bandwidth exceeding the radiation arm length limit. In the auxiliary log-periodic dipole oscillator arm, by adjusting the length change of the log-periodic dipole, the dipole spacing, and the lengths of the longest and shortest dipole oscillator arms, free-space impedance matching of the tightly coupled dipole antenna array without a wide-angle matching layer is achieved, and the bandwidth is extended to high frequencies. Compared with the prior art, the present invention has the following advantages:

[0018] (1) The present invention proposes a scheme of a tightly coupled antenna with a log-periodic structure. Combining the characteristics of the tightly coupled antenna and the log-periodic dipole array, the balanced feed balun is used to reverse the feeding direction, realizing the ultra-wideband performance of the antenna, and avoiding the use of additional structures such as wide-angle matching layers or frequency selective surfaces, reducing the design cost and implementation cost.

[0019] (2) The present invention uses the dipole antenna arms with a log-periodic structure as the upper layer covering of the tightly coupled dipole antenna, replacing the use of the frequency selective surface, achieving integrated processing. At the same time, the log-periodic dipole radiation arms can be used to expand the bandwidth to higher frequencies, while maintaining the stability of the radiation pattern and increasing the application range of the antenna.

[0020] (3) The tightly coupled antenna array provided by the present invention has a compact and simple structure; it is convenient for processing and manufacturing, and can adopt an assembly method of screwing together with assembled screws, with low production and maintenance costs; it is detachable and has a wide range of applications; the array has good stability, and the impedance of each unit in the array can remain stable within a very wide frequency band and angle range, realizing the broadband and wide-angle characteristics of the array. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall structure lamination of an embodiment of the present invention.

[0022] Figure 2 It is a schematic perspective view of the top view angle of an embodiment of the present invention.

[0023] Figure 3 It is a schematic dissection view of the oblique view angle of an embodiment of the present invention.

[0024] Figure 4 It is an enlarged schematic diagram of the tightly coupled dipole radiation patch in an embodiment of the present invention.

[0025] Figure 5 It is an enlarged schematic diagram of the auxiliary log-periodic dipole antenna arm in an embodiment of the present invention.

[0026] Figure 6 It is a schematic diagram of the layer separation of the auxiliary log-periodic dipole antenna arm in an embodiment of the present invention; wherein (a) is a schematic diagram of the distribution of the antenna arms on the second metal layer; (b) is a schematic diagram of the distribution of the antenna arms on the first metal layer.

[0027] Figure 7 It is a schematic diagram of the structure of the balanced feed balun in an embodiment of the present invention; wherein (a) is a schematic diagram of the back plate; (b) is a schematic diagram of the front plate.

[0028] Figure 8 It is a schematic diagram of the structure of each metal layer of a one-dimensional sub-array example of the present invention; wherein (a) is a schematic diagram of the structure of the first metal layer of the one-dimensional sub-array; (b) is a schematic diagram of the structure of the third metal layer of the one-dimensional sub-array; (c) is a schematic diagram of the structure of the fourth metal layer of the one-dimensional sub-array; (d) is a schematic diagram of the structure of the second metal layer of the one-dimensional sub-array.

[0029] Figure 9 It is a comparison diagram of the standing wave curves of simulation and actual measurement of an embodiment of the present invention.

[0030] Figure 10Gain curve of the E-plane 0° direction for the simulation and measurement comparison of a 22-antenna-element tightly coupled dipole antenna array.

[0031] Figure 11 Gain curve of the E-plane 30° direction for the simulation and measurement comparison of a 22-antenna-element tightly coupled dipole antenna array.

[0032] Figure 12 Gain curve of the E-plane 60° direction for the simulation and measurement comparison of a 22-antenna-element tightly coupled dipole antenna array.

[0033] 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 log-periodic dipole oscillator arm; 11: tightly coupled dipole corner; 12: overlapping part of radiation patches; 13: transition section of rectangular radiation patch; 14: rectangular radiation patch; 15: first group of dipole oscillator arms; 16: second group of dipole oscillator arms; 17: third group of dipole oscillator arms; 18: fourth group of dipole oscillator arms; 19: fifth group of dipole oscillator arms; 15-2, 16-1, 17-2, 18-1, 19-2: left oscillator arms of the first to fifth groups of dipole oscillator arms; 15-1, 16-2, 17-1, 18-2, 19-1: right oscillator arms of the first to fifth groups of dipole oscillator arms; 20: coaxial connector connection section metal strip; 21: trapezoidal impedance transformation section; 22: feed line section; 23: probe; 24: coaxial connector connection section metal backplane; 25: exponential impedance transformation section. Detailed implementation manners

[0034] The technical solutions of the present invention will be further introduced below in conjunction with the accompanying drawings and specific embodiments.

[0035] A tightly coupled dipole antenna array loaded with log-periodic oscillators disclosed in an embodiment of the present invention mainly consists of a balanced feed balun, tightly coupled dipole radiation patches, and auxiliary log-periodic dipole oscillator arms. Structurally, it includes four metal layers and dielectric substrates between the metal layers. The first metal layer and the second metal layer are provided with tightly coupled dipole radiation patches with the same geometric size arranged at equal intervals in one dimension. Each tightly coupled dipole radiation patch is connected to an auxiliary log-periodic dipole oscillator arm. The arrangement of the radiation patches and oscillator arms on the first metal layer is rotationally symmetric about the center line of the antenna element with respect to the radiation patches and oscillator arms on the second metal layer, and there is an overlap between the radiation patches of adjacent antenna elements on the first metal layer and the second metal layer. An equivalent capacitance is introduced through the coupling method to cancel the inductance introduced by itself, so that it can operate in 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 uses a microstrip line with a tapered ground to a dielectric twin line to achieve impedance transformation and inversion of the feed direction.

[0036] Figures 1 to 3 A specific form of a tightly coupled dipole antenna array loaded with log-periodic oscillators is given. As Figure 1 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, and the lower surface of the lower dielectric substrate 3 is provided with a second metal layer 5. 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 the traditional PCB process. The metal layer on the dielectric substrate is copper, the thickness of the copper layer is 35 μm, and the dielectric substrates are all Rogers 4003 with a thickness of 1 mm and a dielectric constant of 3.55.

[0037] As Figure 2 and Figure 3As shown in the figure, in the first metal layer 4 and the second metal layer 5, there is a one-dimensional tightly coupled dipole antenna array composed of a number of geometrically identical tightly coupled dipole radiation patches 9 arranged at equal intervals in one dimension. The arrangement of the radiation patches on the first metal layer 4 and the radiation patches on the second metal layer 5 is symmetric about the center line of the antenna element by rotating 180 degrees. The radiation patches on the first metal layer 4 form the right radiation arm of the tightly coupled dipole, and the radiation patches on the second metal layer 5 form the left radiation arm of the tightly coupled dipole. In the first metal layer 4 and the second metal layer 5, there is an auxiliary log-periodic dipole oscillator arm 10 forming an auxiliary log-periodic dipole matching radiation array. The arrangement of the oscillator arms on the first metal layer 4 and the oscillator arms on the second metal layer 5 is symmetric about the center line of the antenna element by rotating 180 degrees and is arranged in an interleaved manner. For example, if the first-stage oscillator arm on the first metal layer 4 forms the left oscillator arm of the dipole structure, then the first-stage oscillator arm on the second metal layer 5 forms the right oscillator arm of the dipole structure. If the second-stage oscillator arm on the first metal layer 4 forms the right oscillator arm of the dipole structure, then the second-stage oscillator arm on the second metal layer 5 forms the left oscillator 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 oscillator arm placement position and placement form. In the third metal layer 6 and the fourth metal layer 7, there is a balanced feed balun 8. One end of it is directly connected to the coaxial connector, and the other end feeds the radiation patch through a probe.

[0038] As Figure 4 shown in the figure, the main structure of the antenna array is the tightly coupled dipole radiation patch 9. The auxiliary log-periodic dipole oscillator arm 10 realizes ultra-wideband matching and is located at the upper end of the tightly coupled dipole radiation patch 9. The lower end of the auxiliary log-periodic dipole oscillator arm 10 is the tightly coupled dipole corner 11. The tightly coupled dipole radiation patch 9 is essentially a dipole antenna. An equivalent capacitance is introduced between it and the adjacent dipole through a strong coupling method to cancel the inductance introduced by itself, so that it can work in a very wide frequency band. The radiation patch is in a segmented form. The first segment is the transition segment 13 from the feeder to the rectangular radiation patch, and the second segment is the extension of the rectangular radiation patch 14. The overlapping part 12 of the radiation patches on the first metal layer 4 and the second metal layer 5 is located at the end of the rectangular radiation patch 14. The length of the transition segment 13 from the feeder to the rectangular radiation patch should not exceed half of the overall radiation patch to avoid affecting the distribution of low-frequency radiation current elements. The width of the tightly coupled dipole radiation patch 9 should not be less than the width of the longest group of oscillator arms in the auxiliary log-periodic dipole oscillator arm 10. The length of the tightly coupled dipole radiation patch 9 should not be less than the length of the longest group of oscillator arms in the auxiliary log-periodic dipole oscillator arm 10. The coupling length of the tightly coupled dipole radiation patch 9 affects the low-frequency performance of the antenna array. The tightly coupled dipole antenna in this embodiment does not require the use of a reflector backplane.

[0039] The main structure of the auxiliary log-periodic dipole matching radiation array is a dipole oscillator arm with a log-periodic topological structure transformation. The rear end of the middle feeder extends outward to form an extension body, and the extension body and the log-periodic dipole form a log-periodic dipole end-fire radiator. The lengths of multiple groups of dipole oscillator arms of the auxiliary log-periodic dipole oscillator arm 10 gradually increase from front to back, the widths of multiple groups of dipole oscillator arms gradually increase from front to back, and the distances between adjacent dipole oscillator arms gradually increase from front to back. During specific design, the length, width, and adjacent spacing of the auxiliary log-periodic dipole oscillator arm 10 can satisfy the following relationships:

[0040]

[0041] Among them, τ represents the scale factor, representing the scaling ratio of the log-period; l n 、 l n+1 represent the lengths of the nth and (n + 1)th stage oscillator arms respectively, where 1 ≤ n ≤ N - 1 and N is the number of oscillator arm stages; w n 、 w n+1 represent the widths of the nth and (n + 1)th stage oscillator arms respectively, where 1 ≤ n ≤ N - 1; s n 、 s n+1 represent the distances between the nth and (n + 1)th stage oscillator arms and between the (n + 1)th and (n + 2)th stage oscillator arms respectively, where 1 ≤ n ≤ N - 2.

[0042] For example Figure 5 and Figure 6As shown, exemplarily, the auxiliary log-periodic dipole oscillator arms 10 include five groups, namely the first group of dipole oscillator arms 15, the second group of dipole oscillator arms 16, the third group of dipole oscillator arms 17, the fourth group of dipole oscillator arms 18, and the fifth group of dipole oscillator arms 19. The left oscillator arm 15-2 of the first group of dipole oscillator arms 15 is located on the first metal layer 4, and the right oscillator arm 15-1 is located on the second metal layer 5; the left oscillator arm 16-1 of the second group of dipole oscillator arms 16 is located on the second metal layer 5, and the right oscillator arm 16-2 is located on the first metal layer 4; the left oscillator arm 17-2 of the third group of dipole oscillator arms 17 is located on the first metal layer 4, and the right oscillator arm 17-1 is located on the second metal layer 5; the left oscillator arm 18-1 of the fourth group of dipole oscillator arms 18 is located on the second metal layer 5, and the right oscillator arm 18-2 is located on the first metal layer 4; the left oscillator arm 19-2 of the fifth group of dipole oscillator arms 19 is located on the first metal layer 4, and the right oscillator arm 19-1 is located on the second metal layer 5. In this embodiment, the auxiliary log-periodic dipole oscillator arms 10 are placed in an interleaved manner to establish relatively symmetric boundary conditions to ensure the balance of the radiation pattern, and at the same time ensure that adjacent dipole units have a 180° phase shift to minimize the interference between them. The shorter end of the auxiliary log-periodic dipole oscillator arms 10 is located in the radiation direction, and the longer end of the oscillator arms is located in the feeding direction. The feeding current is fed into the shorter end of the oscillator arms instead of the longer end of the oscillator arms.

[0043] As Figure 7 shown, the balanced feeding balun 8 includes a coaxial connector connection section metal strip 20, a trapezoidal impedance transformation section 21, a feeding section 22, a coaxial connector connection section metal backplane 24, and an exponential impedance transformation section 25, where the feeding section 22 and the exponential impedance transformation section 25 form a dielectric twin-line structure. The top end of the feeding section 22 is connected to the auxiliary log-periodic dipole oscillator arms 10 through a probe 23, and the bottom end is connected to the trapezoidal impedance transformation section 21; the trapezoidal impedance transformation section 21 is connected to the coaxial feeder through the coaxial connector connection section metal strip 20 for feeding. The feeding connector is a coaxial feeding port, and the feeding connector can be directly fixed on the middle dielectric substrate 2 by means of screw fixation. The coaxial connector connection section metal strip 20 adopts a ground-truncated 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-type tapered line structure for impedance matching, and the front plate adopts a trapezoidal impedance transformation structure. The exponential-type tapered line structure can cover an ultra-wide frequency band by adjusting the slope of the tapered line. Specifically, the balanced feeding 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:

[0044]

[0045] where Z (z ) is the characteristic impedance of the transmission line at position z; Z 0 is the characteristic impedance of the starting end of the transmission line ( z = 0); z is the distance along the length of the transmission line; δ is the impedance change coefficient, which determines the rate of change of the characteristic impedance and can be determined by the following formula:

[0046]

[0047] where L is the total length of the transmission line; Z L is the characteristic impedance of the end of the transmission line ( z = L ); In represents the natural logarithm.

[0048] In this embodiment, the balanced feed balun 8 provided on the middle dielectric substrate 2 reversely transmits the current of the dielectric twin-line structure to the first metal layer 4 and the second metal layer 5 in the form of a probe 23, constituting the radiation condition of the tightly coupled dipole antenna. The feeding probe 23 is located in the dielectrics of the upper dielectric substrate 1 and the lower dielectric substrate 3. The middle dielectric substrate 2 is a transmission layer, and the feeder line of this layer in the antenna part is a dielectric twin-line structure. After being matched by the balanced feed balun 8, the twin-line currents are equal in amplitude and opposite in phase, 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 log-periodic dipole oscillator arm 10 are reversely fed through the balanced feed balun 8 and the probe 23. The feeder line of the feed first passes through the auxiliary log-periodic dipole oscillator arm 10 and then feeds to the tightly coupled dipole radiation patch 9, forming a forward single-directional radiation to ensure that the radiation direction is towards the end-fire direction rather than the feed direction.

[0049] As Figure 8 shown in (a), (b), (c), and (d) of

[0050] The effects of the present invention will be described below in conjunction with a specific design example of a tightly coupled dipole antenna array loaded with a log-periodic dipole. In this design example, the antenna element spacing is set to 24.4 mm, the fixed screw hole spacing is 24.4 mm, the aperture is 2 mm, and the overall height of the antenna is 32 mm. The designed operating frequency is from 2 to 18 GHz. Accordingly, the lengths of the auxiliary log-periodic dipole oscillator arms from top to bottom are 2.2 mm, 3.2 mm, 4 mm, 6.2 mm, and 7 mm in sequence; the widths of the auxiliary log-periodic dipole oscillator arms from top to bottom are 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, and 1 mm in sequence; the length of the tightly coupled dipole radiation patch is 13 mm, where the length of the tapered 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 4.5 mm trapezoidal transformation, while the starting width of the metal backplane 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 a 13.2 mm exponential gradient transformation, and together with the front plate metal strip line, it forms a dielectric two-wire structure. A transition area connected to the SMA connector is designed at the coaxial feed port, and holes are drilled according to the corresponding SMA model.

[0051] As Figure 9 shown, a comparison diagram of the standing wave curves of the designed antenna array is given. The solid line is the measured curve, and the dashed line is the simulated curve. It can be seen that the measured standing wave coefficient and the simulated standing wave coefficient of the designed antenna match within the impedance bandwidth range of 2 GHz to 18 GHz. The impedance bandwidth of the designed antenna can cover 2 GHz to 18 GHz, meeting the requirement that the standing wave coefficient VSWR is less than 3.

[0052] As Figure 10 shown, a main polarization gain curve and a comparison diagram of the designed antenna array in the E-plane at 0° are given. The number of array elements is 22. The solid line is the measured curve, and the dashed line is the simulated curve. It can be seen that the measured gain and the simulated gain of the designed antenna match within the range of 2 GHz to 18 GHz.

[0053] As Figure 11 shown, a main polarization gain curve and a comparison diagram of the designed antenna array in the E-plane at 30° are given. The number of array elements is 22. The solid line is the measured curve, and the dashed line is the simulated curve. It can be seen that the measured gain and the simulated gain of the designed antenna match within the range of 2 GHz to 18 GHz.

[0054] As Figure 12As shown, the main polarization gain curve and comparison diagram of the designed antenna array in the E-plane at 60° are given. The number of array elements is 22. The solid line is the measured curve, and the dashed line is the simulated curve. It can be seen that in the range of 2 GHz to 18 GHz, the measured gain and the simulated gain of the designed antenna are in good agreement.

[0055] It should be noted that unless otherwise specified, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those skilled in the art to which the present invention pertains. It should be understood that the orientation or positional relationship indicated by terms such as up, down, front, back, etc. is based on the orientation or positional relationship shown in the drawings, and 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 thus should not be construed as a limitation to the present invention. In addition, terms such as first, second, etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. In the description of the present invention, the meaning of "a plurality" is more than two, unless otherwise specifically defined; unless otherwise clearly specified and defined, terms such as "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection, an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features, and these modifications or replacements do not make the corresponding technical solutions 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, wherein the first metal layer and the second metal layer are provided with tightly coupled dipole radiation patches of the same geometric size and arranged at equal intervals in one dimension, each tightly coupled dipole radiation patch is connected with an auxiliary logarithmic periodic dipole dipole arm, the auxiliary logarithmic periodic dipole 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 dipole arm is a tightly coupled dipole corner, 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 adjacent antenna array elements are arranged in a rotationally symmetrical manner about the center line of the antenna array element. The radiation patches of the element 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 a balanced feeding balun is provided, and 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; 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 in the reverse direction to the first metal layer and the second metal layer through the feeding probe, forming the radiation condition of the tightly coupled dipole antenna.

2. A tightly coupled dipole antenna array loaded with logarithmic periodic oscillators according to claim 1, characterized in that: 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 portion 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 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 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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