Strong-coupling dual-polarization ultra-wideband phased-array antenna based on fishbone-shaped gap loading

Abstract

The invention discloses a strongly-coupled dual-polarized ultra-wideband phased-array antenna based on fishbone-shaped gap loading and a development method of the strongly-coupled dual-polarized ultra-wideband phased-array antenna. A series of fishbone-shaped gaps with different sizes and intervals are formed in the dipole, a traditional cross-shaped dipole is improved, and the working bandwidth of the antenna is expanded. Resistive loading of a traditional ultra-wideband array is not used, and the radiation efficiency is improved. The feed structure of the power divider and the double-balun is applied, so that better matching can be realized, and the profile height of the antenna is reduced. The whole antenna array adopts the light and thin dielectric substrate, a thick and heavy wide-angle impedance matching layer is omitted, and the weight is lighter. + / -45-degree scanning can be achieved within the frequency band of 0.25-1.85 GHz, and the overall height of the antenna is 0.054 times of the low-frequency wavelength.

Description

Technical Field

[0001] The invention belongs to the technical field of antenna engineering, and in particular relates to a strongly coupled dual-polarized ultra-wideband phased array antenna based on fishbone-shaped slot loading. Background Art

[0002] Compared with traditional mechanical scanning antennas, phased array antennas have the advantages of easy beam shaping, arbitrary change of beam direction, and easy formation of multiple beams. Ultra-wideband (UWB) phased arrays have attracted much attention in multi-functional applications. They use multiple beams, polarizations, and frequency bands to achieve different functions. Traditional ultra-wideband antenna units generally have relatively large lateral or longitudinal dimensions, making it difficult to achieve low-profile, conformal, and lightweight designs. Based on the above drawbacks, a new type of strongly coupled antenna has emerged in recent years. Unlike traditional broadband phased arrays, the design idea of ​​strongly coupled antennas is to use the coupling between units to expand the bandwidth of the antenna. This type of phased array antenna can combine multiple advantages such as wide bandwidth, small size, low profile, and easy conformality.

[0003] In 2018, the document "Broadband Antenna Array Aperture Made of Tightly CouplePrinted Dipoles" proposed an ultra-wideband phased array based on tight coupling technology. The antenna uses printed dipoles as radiators, adopts an "egg box" layout, has loaded coupling capacitors at the junction of adjacent array elements, and uses a double Y-shaped balun that integrates the balun and the impedance transformer in the feeding structure, achieving a standing wave ratio of less than 3 when scanning to 60° within a bandwidth of 1.2-6GHz (5:1). The design uses vertically placed dipoles and a thick dielectric matching layer, which increases the cross-sectional height and mass of the antenna, making it difficult to expand to low frequencies.

[0004] In patent CN110085975A, the inventor proposed an airborne low-scattering ultra-wideband phased array based on tight coupling technology, achieving a bandwidth of 0.5-2GHz (4:1). The design uses magnetic dipoles as the basic radiation unit, which is conducive to conformality. By loading resistive electromagnetic absorbing metamaterials designed in a conformal environment, the out-of-band RCS of the antenna itself is further reduced within a wide bandwidth, but it is difficult to achieve dual polarization and the antenna has a high profile.

[0005] In patent CN112038753A, the inventor used cross-placed electric dipoles to achieve dual polarization to address this problem, and replaced the traditional dielectric matching layer with an artificial metamaterial impedance matching layer, overcoming the shortcomings of the traditional dielectric matching layer, which is high in profile and bulky, and has more advantages in conformal processing. However, the working bandwidth of the array antenna still needs to be further expanded, and it is difficult to meet the needs of wider bandwidth.

[0006] In view of the above-mentioned problems, the present invention discloses a strongly coupled dual-polarization ultra-wideband phased array antenna based on fishbone-shaped slot loading, which is committed to achieving breakthroughs in expanding bandwidth, reducing profile, etc. Summary of the invention

[0007] The purpose of the present invention is to address the problems of insufficient working bandwidth, especially insufficient bandwidth in the low-frequency band, and high cross-section of traditional strongly coupled ultra-wideband antennas. A series of fishbone-shaped slots of different sizes and spacings are loaded on the structure of the antenna radiator, and a feeding structure of a power divider plus a double balun is adopted to achieve a cross-section height of 0.054 low-frequency wavelengths and a bandwidth of 0.25-1.85GHz (7.4:1). The working mode is dual linear polarization, and ±45 degree scanning can be achieved.

[0008] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a strongly coupled dual-polarized ultra-wideband phased array antenna based on fishbone-shaped slot loading. The antenna array comprises a double-layer thin antenna dielectric substrate (100), a cross-shaped dipole unit (101) with fishbone-shaped slots printed on the upper surface of the upper layer of the antenna dielectric substrate, a triangular parasitic patch (102) and a square parasitic patch (103) printed on the lower surface of the upper layer of the antenna dielectric substrate, a Marchand balun (201) without a short-circuit post, a Marchand balun (202) with a short-circuit post, a microstrip power divider (300) placed on a metal floor, and a metal floor (400).

[0009] The dipole layer uses a thin double-layer dielectric substrate. The upper surface of the first substrate is printed with an improved triangular cross dipole, and the blank space of the dipole at the non-crossing position is filled with the same shape rotated 90°. A series of fishbone-shaped gaps of different sizes and spacings are opened on the dipole structure. This structure can improve the low-frequency characteristics of the antenna when resistive loading is not used. A triangular parasitic patch of similar shape is printed on the lower surface. Three square coupling parasitic patches are correspondingly printed on the lower surface of the second substrate. The dipole and the parasitic patch are closely connected, and the gaps between the metal patches and the upper and lower metal patches can generate sufficient capacitive coupling to offset the inductance generated by the ground short circuit at low frequency, thereby expanding the low-frequency bandwidth.

[0010] Furthermore, two dipoles are placed in each polarization direction in the antenna unit. The dipoles in the two polarization directions are placed in a cross shape and are fed by a Marchand balun respectively. They are connected to a power divider placed on the metal ground, and the power divider is fed by a 50Ω coaxial connector. The double balun feeding method can realize the impedance transformation from the 50Ω coaxial connector to the dipole.

[0011] Furthermore, a metal strip is loaded on the right side of the two oscillators of each polarization in the antenna unit relative to the power divider. The strip is printed on the back of the Marchand balun, and the upper and lower ends are electrically connected to the dipole and the floor respectively, serving as a short-circuit column to suppress the common-mode resonance effect of the array.

[0012] Furthermore, a series of through holes and threaded holes are arranged on the metal floor for installing joints, fixing the power divider, and fixing the upper dielectric substrate. The floor and the upper dielectric substrate are supported and fixed by nylon columns.

[0013] In summary, this antenna design has the following innovations: (1) It improves the traditional idea of ​​achieving ultra-wideband characteristics based on resistive loading, achieves ultra-wideband operation without resistive loading, and improves radiation efficiency. (2) The blanks of the dipole are filled with the same shape, so that the three parts of the radiator structure are exactly the same, and the coupling capacitance is increased. (3) A series of fishbone-shaped gaps of different sizes and spacing are opened on the dipole to improve the low-frequency performance. (4) In the double balun in each polarization direction of the antenna element, the right balun with the power divider position as a reference is loaded as a short-circuit column by printing metal strips, and the left balun remains unchanged, which improves the common-mode resonance problem of the antenna array. (5) The profile height is reduced, the operating frequency band reaches 7.4 times the frequency band, and the profile height is only 0.054 low-frequency wavelengths. The traditional thick wide-angle impedance matching layer is eliminated, and the entire antenna is lighter. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The schematic diagram of the strongly coupled dual-polarized ultra-wideband phased array antenna unit based on fishbone-shaped slot loading is provided. 100 is a double-layer thin antenna dielectric substrate, 101 is a cross-type dipole unit with fishbone-shaped slots printed on the upper surface of the upper layer of the antenna dielectric substrate, 201 and 202 are Marchand baluns without short-circuit posts and with short-circuit posts, respectively, 300 is a microstrip power divider, and 400 is a metal floor.

[0015] Figure 2 and Figure 3 Schematic diagram of the entire two-dimensional planar array antenna at different angles. Figure 1 The units are arranged in a 10×4 array, stimulating the middle 8×2 units.

[0016] Figure 4 102 is a triangular metal patch, similar to the shape of a dipole, printed on the back of the first dielectric substrate and aligned with the center of the dipole. 103 is a square metal patch, printed on the back of the second dielectric substrate. The gaps between the parasitic patches and between the upper and lower patches can generate sufficient capacitive coupling, thereby improving the low-frequency bandwidth.

[0017] Figure 5 It is a feeding structure of a power divider plus a double balun. 201 and 202 are Marchand baluns without and with short-circuit posts, respectively. Square holes are opened on the upper and lower grounds of the balun to optimize impedance matching. 203 is the short-circuit post loaded on the right balun. 204 is the vertical connection between the balun and the dipole. 205 is the vertical connection between the balun and the power divider. 300 is a microstrip power divider. 301 is the isolation resistor of the power divider. 302 is the vertical connection between the power divider and the balun. 400 is a metal floor.

[0018] Figure 6 and Figure 7 They are the simulation results of the 0-45 degree scanning active standing wave of a typical port when the array antenna scans on the E-plane and H-plane.

[0019] Figure 8 and Fig. 9 They are the simulation results of the 0-45 degree scanning radiation efficiency of the entire antenna when the array antenna scans on the E plane and the H plane.

[0020] Fig.10 , 11 1 and 12 are the simulation results of the scanning radiation patterns of the array antenna at low frequency 0.4 GHz, medium frequency 0.9 GHz, and high frequency 1.8 GHz when scanning on the E plane.

[0021] Fig.13 , 14 , 15 are the simulation results of the scanning patterns of the array antenna at low frequency 0.4 GHz, medium frequency 0.9 GHz, and high frequency 1.8 GHz when scanning in the H plane. DETAILED DESCRIPTION

[0022] like Figure 1 As shown, the tightly coupled ultra-wideband low-profile conformal phased array antenna based on resistance ring loading in this embodiment is composed of a double-layer thin antenna dielectric substrate 100, a cross-type dipole unit 101 with fishbone-shaped gaps printed on the upper surface of the upper layer of the antenna dielectric substrate, a Marchand balun 201 without short-circuit posts, a Marchand balun 202 with short-circuit posts, a microstrip power divider 300, and a metal floor 400.

[0023] The antenna dielectric substrates all use Rogers RO4350 dielectric substrates. The radiation patch layer 100 is a double-layer dielectric substrate pressed together. The feed balun is a stripline structure, which is composed of a double-layer dielectric plate pressed together. The floor is made of metal aluminum plate. The back of the microstrip power divider and the metal floor need to be glued together with conductive glue, and holes are opened on the power divider dielectric substrate and the floor to fix them. The vertical connection between the balun and the power divider and the electrical connection between the balun and the dipole are ensured by welding. The antenna layer and the floor opening are fixed with nylon columns.

[0024] Figure 5 The power divider and balun dielectric substrate shown in the figure both use Rogers RO4350 dielectric substrate. The balun is a stripline structure. The upper and lower grounds of the balun are connected through metallized vias, and the ends are welded to the metal floor to ensure grounding. The power divider is welded on the floor. The one-to-two method can realize the conversion of the coaxial connector from 50Ω to 100Ω. The balun stripline structure can bear the change from 100Ω to the input impedance of the antenna layer, and the impedance matching is well achieved without increasing the length of the balun.

[0025] The overall profile height of the antenna is 0.054 times the low-frequency wavelength, excluding the thickness of the metal floor, and the spacing between adjacent units is 75mm.

[0026] Figure 6 The simulation results of active standing waves when the array antenna scans 0°, 30° and 45° on the E plane are shown in Figure 1. It can be seen that good matching performance is achieved in the 0.25-1.85 GHz frequency band.

[0027] Figure 7 The simulation results of active standing waves when the array antenna scans 0°, 30° and 45° on the H plane are shown in Figure 1. It can be seen that good matching performance is achieved in the 0.25-1.85GHz frequency band.

[0028] Figure 8 The simulation results of the radiation efficiency of the array antenna when scanning 0°, 30° and 45° on the E plane are shown in Figure 1. It can be seen that the radiation efficiency is relatively high except for a few frequency points in the 0.25-1.85GHz frequency band.

[0029] Fig. 9 The simulation results of the radiation efficiency of the array antenna when scanning 0°, 30° and 45° on the H plane are shown in Figure 1. It can be seen that the radiation efficiency is relatively high except for a few frequency points in the 0.25-1.85GHz frequency band.

[0030] Fig.10 This is the simulation result of the scanning pattern of the array antenna at the low frequency of 0.4GHz when scanning on the E plane. The pattern beam has good directivity and the polarization isolation is above 34dB.

[0031] Fig.11 This is the simulation result of the scanning pattern of the array antenna at the intermediate frequency of 0.9 GHz when scanning on the E plane. The pattern beam has good directivity and the polarization isolation is above 28 dB.

[0032] Fig.12 This is the simulation result of the scanning pattern of the array antenna at the high frequency of 1.8GHz when scanning on the E plane. The pattern beam has good directivity, the cross polarization is slightly increased, but the isolation is still above 14dB.

[0033] Fig.13 This is the simulation result of the scanning pattern of the array antenna at the low frequency of 0.4GHz when scanning in the H plane. The pattern beam has good directivity and the polarization isolation is above 37dB.

[0034] Fig.14 This is the simulation result of the scanning pattern of the array antenna at the intermediate frequency of 0.9 GHz when scanning in the H plane. The pattern beam has good directivity and the polarization isolation is above 35 dB.

[0035] Fig.15 This is the simulation result of the scanning pattern of the array antenna at the high frequency of 1.8GHz when scanning in the H plane. The directivity of the pattern beam is good, the cross polarization is slightly increased, but the isolation is still above 13dB.

[0036] The above-mentioned embodiments only express the specific implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed. It should be understood that they are only presented in an exemplary form and cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. A strongly coupled dual-polarized ultra-wideband phased array antenna based on fishbone slot loading, characterized in that: The invention comprises a double-layer thin antenna dielectric substrate (100), a cross-type dipole unit (101) with fishbone-shaped gaps printed on the upper surface of the upper layer of the antenna dielectric substrate, a triangular parasitic patch (102) and a square parasitic patch (103) printed on the lower surface of the upper layer of the antenna dielectric substrate, a Marchand balun (201) without a short-circuit post, a Marchand balun (202) with a short-circuit post, a microstrip power divider (300) placed on a metal floor, and a metal floor (400), wherein the microstrip power divider and the Marchand balun are both printed on a thin dielectric substrate, the microstrip power divider dielectric substrate is placed parallel to the antenna dielectric substrate, the balun is placed perpendicular to the antenna dielectric substrate, and the overlapping portion is fixed by opening a rectangular groove.

2. The strongly coupled dual-polarized ultra-wideband phased array antenna based on herringbone slot loading according to claim 1, characterized in that A combination of triangular and square parasitic patches is used to tightly connect with the dipole antenna structure to enhance the coupling between antenna units. A series of fishbone-shaped gaps of varying sizes and spacing are opened on the dipole. The resistive loading of traditional ultra-wideband array antennas is not used, which effectively expands the working bandwidth of the low-frequency band and improves the radiation efficiency.

3. The strongly coupled dual-polarized ultra-wideband phased array antenna based on herringbone slot loading according to claim 1, characterized in that A feeding structure of a power divider plus a double balun is applied. In the antenna unit, the same polarization direction includes two dipoles, which are fed by a Marchand balun respectively and connected to a one-to-two power divider. This can well achieve impedance matching from the characteristic impedance of the coaxial connector to the dipole. The balun undertakes less impedance transformation function, which can realize the miniaturization of the balun and reduce the overall profile height of the antenna.

4. The strongly coupled dual-polarized ultra-wideband phased array antenna based on herringbone slot loading according to claim 1, characterized in that The dielectric substrates are all made of light, thin, and easy-to-bend flexible dielectrics, eliminating the traditional thick and wide-angle impedance matching layer, and are lighter in weight; the array antenna uses a metal floor to enhance the mechanical strength, and the metal floor and the lower surface of the power divider are bonded with conductive glue to ensure good electrical connection between the metal floor and other structures that need to share a common ground.

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