A tightly coupled array antenna based on an integrated microstrip balun

Abstract

A tightly coupled array antenna based on an integrated microstrip balun is composed of a plurality of polarization units, wherein the polarization unit comprises an antenna floor, a magnetic absorbing material is arranged above the antenna floor, a supporting material is arranged above the magnetic absorbing material, a radio frequency connector is arranged inside the antenna floor, the radio frequency connector is connected to one end of a coaxial feed line, and the other end of the coaxial feed line passes through the antenna floor, the magnetic absorbing material and the supporting material in sequence; a lower substrate is arranged above the supporting material; a feed balun is printed on the upper surface of the upper substrate, and a reused dipole arm is printed on the lower surface of the upper substrate; the present invention adopts a multi-layer board process, and prints an antenna radiator, a coupler and a feed balun on different copper layers of the multi-layer board respectively, so as to achieve space optimization, further optimize the antenna impedance matching, and has the characteristics of excellent performance and easy installation; the present invention adopts a feed balun in the form of a multi-order microstrip transmission line, optimizes the microstrip transmission line model of each order, and effectively improves the compactness of the antenna unit.

Description

Technical Field

[0001] The present invention relates to the technical field of tightly coupled array antennas, and in particular to a tightly coupled array antenna based on an integrated microstrip balun. Background Art

[0002] Tightly coupled array antennas have the characteristics of ultra-wideband, low profile, and compact array surface, which can meet the requirements of ultra-wideband coverage and wide-angle scanning in the current phased array antenna design. At present, array antennas are developing in the direction of planarization and modular design, and so are tightly coupled array antennas. When tightly coupled array antennas achieve ultra-wideband coverage, they often need to be equipped with a feeding balun of the corresponding working bandwidth to achieve balanced feeding, thereby optimizing the antenna matching impedance. However, conventional feeding baluns cannot achieve modular design requirements such as simple feeding structure, low profile, compact structure, and high structural strength. The modular tightly coupled array antenna in the form of Planar Ultra-wideband Modular Antenna (PUMA) without feeding balun is difficult to expand the antenna bandwidth, and the in-band resonance generated by its unbalanced feeding requires additional de-resonance design, which increases the complexity and cost of the antenna; on the other hand, when conventional tightly coupled array antennas achieve multi-frequency coverage, the impedance matching level within the frequency band is often not high. When many existing tightly coupled antenna forms achieve more than 6 times frequency coverage, the antenna impedance matching level can only reach a voltage standing wave ratio VSWR <3. Therefore, the optimized design of the radiation structure of the tightly coupled antenna and the impedance matching optimization capability of the feed balun still need to be improved.

[0003] Patent application CN202021176840.0 discloses an ultra-wideband tightly coupled antenna array and antenna device, which combines an exponential gradient balun with a gradient microstrip line to form a low-profile ultra-wideband feed balun; the balun feed line is divided into vertical and horizontal sections, both of which are trapezoidal gradient line structures for impedance matching, effectively reducing the height of conventional exponential gradient line baluns, thereby achieving an antenna profile of only 0.07 times the wavelength at low frequency. However, due to the design method of segmentation and docking of different substrates, this feed balun is not compact enough and has limited structural strength, making it unsuitable for modular array antenna design; and, due to the design requirements of low profile, its coverage bandwidth is only 4 times the frequency.

[0004] A flexible, ultra-thin, modular, ultra-wideband tightly coupled array antenna disclosed in patent application CN202111394386.5 abandons the balun design and directly uses a coaxial line to microstrip line to feed the planar printed vibrator antenna, combined with the loading of absorbing materials on the floor to achieve a low-profile design. In addition, the application fills flexible supporting materials between the absorbing material and the printed vibrator, which can realize the design of a flexible modular tightly coupled array antenna, and the antenna bandwidth can reach 9 times the frequency. However, since the antenna has no balun for balanced feeding, the impedance matching degree within its operating frequency band is limited, and the standing wave is greater than 2 at multiple frequency bands. In addition, in order to optimize the impedance matching level, the antenna vibrator arm is wide within the unit size, and dual-polarization design cannot be achieved.

[0005] Therefore, one of the urgent problems to be solved in the current field of tightly coupled antenna technology is how to realize the integrated design of the feed balun, and on this basis further improve the impedance matching level within the antenna working frequency band, and combine the characteristics of high strength, compactness, and modular array antennas, which is in line with the development trend of modular ultra-wideband array antennas in the future. Such a design is expected to improve the performance of the antenna, while meeting the needs of broadband antenna systems for simplified structure and easy installation. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a tightly coupled array antenna based on an integrated microstrip balun, adopt a feeding balun in the form of a multi-order microstrip transmission line, and optimize the microstrip transmission line models of each order through field-path coordination, so as to quickly and accurately obtain a multi-order microstrip line balun that can achieve impedance matching optimization within the antenna working frequency band, without occupying additional space outside the antenna radiator, effectively improving the compactness of the antenna unit, and meeting the modular design needs of the antenna; using a multi-layer board process, the antenna radiator, coupler, and feeding balun are respectively printed on different copper layers of the multi-layer board, so as to maximize the space optimization of the radiator, coupler, and feeding balun, further optimize the antenna impedance matching, and have the characteristics of excellent performance and easy installation.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A tightly coupled array antenna based on an integrated microstrip balun is composed of a plurality of polarization units, wherein the polarization units include an antenna floor, a magnetic absorbing material is arranged above the antenna floor, a supporting material is arranged above the magnetic absorbing material, a radio frequency connector is arranged inside the antenna floor, the radio frequency connector is connected to one end of a coaxial feed line, and the other end of the coaxial feed line passes through the antenna floor, the magnetic absorbing material and the supporting material in sequence from bottom to top; a lower substrate is arranged above the supporting material, a coupling body is printed on the lower surface of the lower substrate, and the lower substrate and the upper substrate are pressed together by a film; a feed balun is printed on the upper surface of the upper substrate, a multiplexed dipole arm is printed on the lower surface of the upper substrate, a metallized via is also arranged on the upper substrate, and a feed balun end is connected to the other arm of the dipole antenna through the metallized via.

[0009] The radio frequency connector is integrated with the coaxial feed line.

[0010] The inner core of the coaxial feed line penetrates upwardly through the lower substrate, the adhesive film and the upper substrate respectively, and is connected to the feeding balun on the top layer, and the outer skin of the coaxial feed line is connected to the multiplexing dipole arm.

[0011] The coaxial feed line is a rigid cable and is vertically placed between the antenna floor, the magnetic absorbing material and the supporting material.

[0012] The supporting material is made of rigid material.

[0013] The feeding balun is in the form of a multi-order microstrip transmission line.

[0014] The multiplexing oscillator arm and the feeding balun are respectively printed on the upper surface and the lower surface of the same area of ​​the upper substrate.

[0015] The lower substrate is provided with a lower substrate hole for the coaxial feed line to pass through.

[0016] The adhesive film is provided with an adhesive film hole for the coaxial feed line to pass through.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. In the present invention, the upper surface of the upper substrate is printed with a feed balun, the lower surface of the upper substrate is printed with a multiplexing dipole arm, and the lower surface of the lower substrate is printed with a coupling body, and the three do not interfere with each other. Compared with the direct coupling method using a radiator in a conventional tightly coupled antenna, it can provide great freedom for the structural design of radiation, coupling and feed baluns, provide more sufficient space for the impedance matching optimization design of the antenna, and also realize single / dual polarization design as needed.

[0019] 2. The overall structure of the antenna array of the present invention adopts a multi-layer vertical interconnected form including a radiation and feeding layer, a support layer, an absorbing layer and a floor, which can effectively ensure the overall structural strength of the array antenna and has the characteristics of modularity, easy installation and strong portability.

[0020] 3. The feeding balun in the present invention adopts the form of a multi-order microstrip transmission line, takes the radiator as the ground, and relies on a dielectric substrate to achieve an integrated design with the radiator, does not occupy additional space, ensures the compactness between the antenna and its feeding structure, and takes into account the balanced feeding design and modular design requirements of the antenna.

[0021] 4. Compared with conventional feeding baluns, the feeding balun in the present invention can not only complete basic impedance transformation due to its multi-order microstrip transmission line form characteristics, but also can further optimize the transmission network parameters of the antenna main port by adjusting the characteristic impedance of each order transmission line on this basis. With the help of the theoretical model of microstrip transmission line and the field-path synergy method, the antenna impedance matching optimization design can be completed quickly and accurately for specific antenna radiation parameters.

[0022] In summary, the present invention adopts a multi-layer board process to print the antenna radiator, coupler and feed balun on different copper layers of the multi-layer board respectively, so as to maximize the space optimization of the radiator, coupler and feed balun, further optimize the antenna impedance matching, and has the characteristics of excellent performance, simple structure and easy installation; the present invention adopts a feed balun in the form of a multi-order microstrip transmission line, and optimizes the microstrip transmission line model of each order through field-path coordination, so as to quickly and accurately obtain a multi-order microstrip line balun that can achieve impedance matching optimization within the antenna working frequency band, without occupying additional space outside the antenna radiator, effectively improving the compactness of the antenna unit, and meeting the modular design needs of the antenna. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the present invention.

[0024] Figure 2 It is a schematic diagram of the overall layout of an embodiment of the present invention.

[0025] Figure 3 It is a schematic diagram of a multi-layer vertical interconnection modularization according to an embodiment of the present invention.

[0026] Figure 4 It is a graph of the measured and simulated active voltage standing wave ratio of the present invention.

[0027] Among them: 1. Multiplexing dipole arm; 2. Feed balun; 3. Coupler; 4. Magnetic absorbing material; 5. RF connector; 6. Coaxial feed line; 7. Support material; 8. Antenna floor; 9. Upper substrate; 10. Metallized via; 11. Lower substrate; 12. Adhesive film; 13. Lower substrate hole; 14. Adhesive film hole. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0029] Reference Figure 1 A tightly coupled array antenna based on an integrated microstrip balun is composed of a plurality of polarization units, wherein the polarization unit includes an antenna floor 8, and a magnetic absorbing material 4 is arranged above the antenna floor 8. To further optimize the impedance matching of the antenna, the magnetic absorbing material 4 is applied above the antenna floor 8 to eliminate the impedance matching short-circuit point caused by the floor reflection on the tightly coupled antenna, and the antenna profile is effectively reduced. A supporting material 7 is filled between the magnetic absorbing material 4 and the lower substrate 11 to further enhance the overall strength of the antenna array, improve the modular design of the antenna array, and solve the problems of low impedance matching level in the working frequency band of conventional ultra-wideband tightly coupled antennas, and the contradiction between balanced feeding and modular design.

[0030] The magnetic absorbing material 4 may be a rubber-type ferrite-filled magnetic absorbing material. The supporting material 7 may be a rigid material with low dielectric constant, low loss, and low density, such as honeycomb (dielectric constant of about 1.008) and polymethacrylimide (PMI) rigid foam (dielectric constant less than 1.1), that is, a rigid material with a dielectric constant close to that of air is preferred, and the supporting material 7 is only used for support and does not affect the electrical performance.

[0031] An RF connector 5 is provided inside the antenna floor 8, and the RF connector 5 is connected to one end of the coaxial feed line 6, and the other end of the coaxial feed line 6 passes through the antenna floor 8, the magnetic absorbing material 4 and the supporting material 7 from bottom to top in sequence; the present invention also customizes the RF connector 5, and the coaxial feed line 6 and the RF connector 5 made of rigid material are welded together, and the RF connector 5 is embedded in the antenna floor 8. The coaxial feed line 6 not only completes the task of feeding, but also plays a role of vertical support between the antenna floor 8 and the upper substrate 9 printed with the reused dipole arm 1, and the filling of the supporting material 7 can further enhance the modular characteristics of the antenna array.

[0032] A lower substrate hole 13 and an adhesive film hole 14 are designed on the lower substrate 11 and the adhesive film 12 respectively, so that the coaxial feed line 6 is connected to the multiplexed dipole arm 1. At this time, the coaxial feed line 6 plays both a feeding role and a supporting role, further strengthening the overall structural strength of the antenna and realizing the modular design of the antenna.

[0033] A lower substrate 11 is arranged above the supporting material 7 , and a coupling body 3 is printed on the lower surface of the lower substrate 11 . The lower substrate 11 and the upper substrate 9 are pressed together into one by an adhesive film 12 .

[0034] A feeding balun 2 is printed on the upper surface of the upper substrate 9, and a multiplexing dipole arm 1 is printed on the lower surface of the upper substrate 9. At this time, the multiplexing dipole arm 1 serves as both the radiator of the antenna and the ground of the feeding balun 2. The feeding balun 2 is the integrated microstrip feeding balun proposed in the present invention.

[0035] A metallized via hole 10 is also provided on the upper substrate 9 , and the end of the feed balun 2 is connected to the other arm of the dipole antenna through the metallized via hole 10 .

[0036] The inner core of the coaxial feed line 6 penetrates the lower substrate 11, the adhesive film 12 and the upper substrate 9 upwards, and is connected to the top-layer feed balun 2. The outer skin of the coaxial feed line 6 is connected to the multiplexed dipole arm 1, and the end of the feed balun 2 is connected to the other arm of the dipole antenna through the metallized via 10 to complete the feeding. This balun structure is integrated with the antenna radiator in the upper and lower layers of the same dielectric substrate, which greatly realizes the intensive use of the antenna space, and through the multi-stage optimization design of the feed balun 2, it can effectively realize the optimization of the total impedance matching of the antenna.

[0037] Reference Figure 2 , Figure 2 This is an embodiment of the present invention. In this embodiment, a tightly coupled array antenna based on an integrated microstrip balun is composed of a plurality of antenna periodic units. The antenna periodic unit contains two components, namely, a horizontal polarization unit and a vertical polarization unit, that is, the antenna unit is a dual-polarization unit. Since the present invention adopts a multi-layer board process, the antenna radiator, the coupler, and the feed balun are respectively printed on different copper layers of the multi-layer board. When the antenna adopts a dual-polarization unit design, it can also ensure design freedom and high performance, and has the advantages of saving space without affecting antenna performance.

[0038] The present invention adopts a feeding balun 2 in the form of a multi-microstrip transmission line to replace the traditional feeding balun, optimizes the microstrip transmission line models of each order through field-path coordination, takes antenna impedance matching as the optimization condition, and thus quickly and accurately obtains a multi-order microstrip line balun that can achieve impedance matching optimization within the antenna working frequency band; the feeding balun 2 takes the radiator as the ground and is integrated with the radiator and printed on a dielectric substrate, without occupying additional space outside the antenna radiator, effectively improving the compactness of the antenna unit and meeting the modular design requirements of the antenna.

[0039] The present invention adopts a multi-layer board process, and a feed balun 2 is printed on the upper surface of the upper substrate 9, a multiplexing dipole arm 1 is printed on the lower surface of the upper substrate 9, and a coupling body 3 is printed on the lower surface of the lower substrate 11. The three do not interfere with each other, and the space optimization of the feed balun 2, the multiplexing dipole arm 1 and the coupling body 3 is maximized, thereby further optimizing the antenna impedance matching.

[0040] Reference Figure 2 In the embodiment, the antenna is designed as a horizontal-vertical dual-polarization unit, and the ends of the two polarization units are centrally distributed, so the radiators of the horizontal and vertical polarization units are L-shapedly distributed, so the antenna array is arranged as follows: Figure 2 The periodic unit distribution shown in .

[0041] Reference Figure 3 The overall structure of the antenna array is a modular form of multi-layer vertical interconnection, including a radiation and feeding layer, a support layer, an absorbing layer and a floor. Among them, the radiation and feeding layer includes: a multiplexing dipole arm 1, a feeding balun 2, a coupling body 3, an upper substrate 9, a lower substrate 11 and a film 12; the support layer includes: a support material 7; the absorbing layer includes: a magnetic absorbing material 4; and the floor includes: an antenna floor 8.

[0042] On the one hand, the tightly coupled array antenna proposed in the present invention adopts a microstrip integrated balun for feeding. Compared with the conventional tightly coupled array antenna, the balun is in the form of a multi-order microstrip line. The length and width of the microstrip lines of each order can be automatically optimized and designed through a microstrip line mathematical model and circuit software. Combined with the design method of a multi-layer board, the radiator, coupler and feeding balun are placed on different copper layers respectively, which can maximize the adjustment effect of the feeding balun on the antenna port impedance within the same spatial range.

[0043] like Figure 4 As shown, the simulation and measured results of the active voltage standing wave ratio of the array units of the antenna array prototype are both below 2, indicating that the impedance matching degree is very high and the reflected energy is less than 10%. For the current tightly coupled antennas, the impedance matching level is often only VSWR < 3 when achieving more than 6 times the frequency coverage. For example, although the antenna described in patent application CN202111394386.5 can also achieve 9 times the frequency band coverage, its in-band impedance matching level is only VSWR < 2. This shows that the design method proposed in the present invention can further optimize the bandwidth and its impedance matching level on the basis of conventional tightly coupled antennas, achieve a better tightly coupled antenna design, and can effectively optimize the antenna impedance matching.

[0044] On the other hand, the microstrip integrated feeding balun adopted by the present invention is integrated with the antenna radiator, and does not need to occupy any space outside the radiator, avoiding the occupation of the antenna profile space by the traditional balun, and structurally ensuring the low profile characteristics of the antenna. Combined with the loading of the absorbing material, the antenna profile height is further reduced, and the planar design of the array is realized. The antenna profile height can reach 0.047 times the wavelength of the lower sideband. On this basis, the present invention also combines the support layer, the integrally welded rigid cable and the RF connector design, and the antenna array presents a layered vertical interconnected structure. The structure is stable, reliable, and high in strength, and has the advantages of a tightly coupled symmetrical vibrator antenna array and PUMA, and finally realizes the planar modular design of a tightly coupled array antenna.

Claims

1. A tightly coupled array antenna based on an integrated microstrip balun, consisting of a plurality of polarization units, characterized in that: The polarization unit comprises an antenna floor (8), a magnetic wave absorbing material (4) is arranged above the antenna floor (8), a supporting material (7) is arranged above the magnetic wave absorbing material (4), a radio frequency connector (5) is arranged inside the antenna floor (8), the radio frequency connector (5) is connected to one end of a coaxial feed line (6), and the other end of the coaxial feed line (6) passes through the antenna floor (8), the magnetic wave absorbing material (4) and the supporting material (7) in sequence from bottom to top; a lower substrate (11) is arranged above the supporting material (7), a coupling body (3) is printed on the lower surface of the lower substrate (11), and the lower substrate (11) and the upper substrate (9) are pressed together by means of an adhesive film (12). The invention relates to an integrated circuit; a feeding balun (2) is printed on the upper surface of the upper substrate (9), a multiplexing dipole arm (1) is printed on the lower surface of the upper substrate (9), and a metallized via hole (10) is also provided on the upper substrate (9); the end of the feeding balun (2) is connected to the other arm of the dipole antenna through the metallized via hole (10); the multiplexing dipole arm (1) serves as both a radiator of the antenna and a ground of the feeding balun (2); the feeding balun (2) adopts a multi-order microstrip transmission line form, and optimizes the microstrip transmission line model of each order by means of field-path synergy; the multiplexing dipole arm (1) and the feeding balun (2) are respectively printed on different layers in the same area of ​​the multi-layer dielectric substrate.

2. A tightly coupled array antenna based on an integrated microstrip balun according to claim 1, characterized in that: The radio frequency connector (5) and the coaxial feed line (6) are arranged as one piece.

3. A tightly coupled array antenna based on an integrated microstrip balun according to claim 1, characterized in that: The inner core of the coaxial feed line (6) penetrates upward through the lower substrate (11), the adhesive film (12) and the upper substrate (9) respectively, and is connected to the feeding balun (2) on the top layer, and the outer skin of the coaxial feed line (6) is connected to the multiplexing dipole arm (1).

4. The tightly coupled array antenna based on an integrated microstrip balun according to claim 1, characterized in that: The coaxial feed line (6) is a rigid cable and is vertically placed between the antenna floor (8), the magnetic wave absorbing material (4) and the supporting material (7).

5. The tightly coupled array antenna based on integrated microstrip balun according to claim 1, characterized in that: The supporting material (7) is made of a rigid material.

6. The tightly coupled array antenna based on integrated microstrip balun according to claim 1, characterized in that: The lower substrate (11) is provided with a lower substrate hole (13) for the coaxial feed line (6) to pass through.

7. The tightly coupled array antenna based on integrated microstrip balun according to claim 1, characterized in that: The adhesive film (12) is provided with an adhesive film hole (14) for the coaxial feed line (6) to pass through.

Images