Ultra-wideband large-angle scanning phased array antenna loaded with a gradient impedance matching layer

Abstract

The present invention provides an ultra-wideband large-angle scanning phased array antenna loaded with a gradient impedance matching layer. The antenna element in the phased array antenna includes: a feeding structure and a radiation structure; the feeding structure includes: a transverse dielectric substrate, a metal floor on its lower surface, and a gradient transmission line on its upper surface, a first longitudinal dielectric substrate, and a Marchand balun disposed on its surface; the radiation structure includes: a second longitudinal dielectric substrate, a dipole and an impedance matching patch structure disposed on its surface; meanwhile, a metal coupling patch is also disposed between the units to introduce strong capacitive coupling. The present invention utilizes the longitudinal gradient impedance matching layer to achieve a good transformation from the dipole radiator to the impedance of free space, realizes wide-angle scanning and reduces the antenna manufacturing cost; utilizes the metal coupling patch to achieve low-frequency impedance matching and expand the array bandwidth; in addition, the profile height is also reduced by improving the feeding structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of antenna engineering, and particularly relates to an ultra-wideband large-angle scanning phased array antenna loaded with a gradient impedance matching layer. Background Art

[0002] Ultra-wideband phased array antennas can accommodate many communication frequency bands. Traditional radio electronic systems require multiple antenna arrays operating at different frequency bands to achieve complex functions, while an ultra-wideband antenna array can reduce the volume, weight, and cost of the system by several times. Therefore, ultra-wideband phased array antenna technology has broad application prospects in military and civilian fields. An ideal phased array antenna should have high gain, narrow beam width, large scanning range, and long detection distance. However, the scanning range of a typical phased array antenna is only ±45° or ±60°. If a two-dimensional phased array antenna can achieve large-angle scanning, a large number of antennas, costs, and spaces can be saved, which is more conducive to the integration of large systems. Therefore, large-angle scanning of phased array antennas has very important research value.

[0003] For example, the literature "I.D. Hinostroza Sáenz, R. Guinvarc'h, R.L. Haupt and K. Louertani, 《A dual-polarized wideband planar phased array with spiral antennas》, IEEE Trans. Antennas Propag., vol. 62, no. 9, pp. 4547-4553, 2014" uses planar spiral antennas to achieve a very wide bandwidth, but there are impedance matching problems during large-angle scanning, and it is difficult to achieve wideband large-angle scanning. For example, the literature "R.W. Kindt and W.R. Pickles, 《Ultrawideband All-Metal Flared-Notch Array Radiator》, IEEE Trans. Antennas Propag., vol. 58, no. 11, pp. 3568-3575, 2010" uses Vivaldi antennas to achieve a relatively wide bandwidth, but its height is relatively high, which is not conducive to low-profile design. Moreover, during diagonal plane (D-plane) scanning, its high-frequency cross-polarization deteriorates severely.

[0004] In a UWB array, impedance matching generally deteriorates gradually with the increase of the scanning angle. In the literature "S.N. Makarov and A. Puzella, 《Scan impedance for an infinite dipole array: Hansen's formulas compared with Ansoft HFSS simulations》, IEEE Antennas Propag. Mag., vol. 49, no. 4, pp. 143 - 156, 2007", the point - frequency impedance characteristics of an infinite dipole antenna array during large - angle scanning in the E - plane, H - plane, and D - plane have been analyzed. The analysis results show that the real part of the impedance decreases to 0 Ω with the increase of the scanning angle. The imaginary part of the impedance fluctuates less during E - plane and D - plane scanning, but during H - plane scanning, the imaginary part of the impedance increases with the increase of the scanning angle. Therefore, the input impedance varies with the scanning angle, greatly increasing the matching difficulty of the antenna during large - angle scanning.

[0005] In the literature "D. Cavallo, W.H. Syed and A. Neto, 《Connected - Slot Array With Artificial Dielectrics: A 6 to 15 GHz Dual - Pol Wide - Scan Prototype》, IEEE Trans. Antennas Propag., vol. 66, no. 6, pp. 3201 - 3206 2018", a multi - layer matching layer is used to achieve large - angle scanning of a UWB array, achieving scanning of 80° in the E - plane and 70° in the H - plane. However, the number of dielectric layers reaches seven, resulting in a relatively high manufacturing cost of the antenna.

[0006] It can be found that the key to the design of a UWB large - angle scanning array antenna is to overcome the impedance matching problem under the condition of drastic change of the antenna input - port impedance during wide - angle scanning. Existing design schemes generally achieve this through methods such as optimizing the design of the feeding structure, loading lossy materials, and loading multi - layer matching layers. However, from the above - mentioned research status, the design of UWB large - angle antenna arrays faces some challenges. First, the manufacturing cost of the existing wide - angle matching layer in the form of multi - layer dielectric stacking is high, and it is difficult to simultaneously achieve large - angle scanning of 70° in both the E - plane and H - plane. Second, it is difficult to design a broadband feeding structure. The feeding structure of a UWB array not only needs to achieve large impedance transformation but also needs to meet the conversion from an unbalanced port to a balanced port. The existing impedance transformer designs face problems such as narrow bandwidth, high profile, or complex design, and it is difficult to simultaneously achieve an impedance transformer with ultra - wideband, low profile, light weight, and simple design. Summary of the Invention

[0007] Aiming at the problem that it is difficult for existing ultra-wideband antennas to achieve low profile, large-angle scanning and low cost at the same time, the present invention proposes an ultra-wideband large-angle scanning phased array antenna loaded with a gradient impedance matching layer. Based on the principle of tight coupling, the present invention adopts a novel gradient impedance matching structure, combines the characteristics of impedance gradient lines and Marchand baluns, and realizes 70° scanning in the E-plane and H-plane under the conditions of a 2.1-fold frequency bandwidth and a profile height of 0.71 times the high-frequency wavelength.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] An ultra-wideband large-angle scanning phased array antenna based on loading a gradient impedance matching layer, characterized in that: the phased array antenna is composed of a plurality of antenna units arranged periodically;

[0010] The antenna unit includes a feeding structure and a radiation structure;

[0011] The feeding structure includes a transverse dielectric substrate, a first longitudinal dielectric substrate, a metal floor, a gradient transmission line, and a Marchand balun;

[0012] The metal floor is arranged on the lower surface of the transverse dielectric substrate;

[0013] The gradient transmission line is arranged on the upper surface of the transverse dielectric substrate, one end of which is used as a feeding input port and the other end is connected to the unbalanced input end of the Marchand balun;

[0014] The first longitudinal dielectric substrate is vertically placed above the transverse dielectric substrate;

[0015] The Marchand balun is arranged on the surface of the first longitudinal dielectric substrate, including an unbalanced input end and a balanced output end, and is used to achieve broadband impedance matching;

[0016] The radiation structure includes a second longitudinal dielectric substrate, a dipole, and an impedance matching patch structure;

[0017] The second longitudinal dielectric substrate is an upward extension of the first longitudinal dielectric substrate;

[0018] The dipole includes two dipole arms arranged on the front surface of the second longitudinal dielectric substrate and mirror-symmetrical, and the two dipole arms are connected to the balanced output end of the Marchand balun; a narrow gap is arranged between the dipole arms of adjacent antenna units;

[0019] The impedance matching patch structure includes at least two sets of tapered impedance matching patches sequentially arranged on the surface of the second longitudinal dielectric substrate from bottom to top; each set of the tapered impedance matching patches includes a row of front tapered metal patches and a row of back tapered metal patches whose projections coincide with each other, and the tapered metal patches are all tapered structures with gradually decreasing widths from bottom to top; the tapered impedance matching patches in each group and the second longitudinal dielectric substrate in the middle thereof together form a tapered impedance matching layer for improving the large-angle scanning ability.

[0020] Further, the antenna unit further includes two metal coupling patches arranged on the back surface of the second longitudinal dielectric substrate and a metal short circuit line arranged on the back surface of the first longitudinal dielectric substrate; the projections of the two metal coupling patches are respectively located at the ends of the two dipole arms, and the metal coupling patches of adjacent antenna units are connected to each other and connected to the metal floor through the metal short circuit line.

[0021] Further, the tapered transmission line is a bent stepped tapered transmission line, a linear tapered transmission line or an exponential tapered transmission line for reducing the volume of the antenna unit.

[0022] Further, the Marchand balun includes a first transmission line and a second transmission line arranged on the back surface of the first longitudinal dielectric substrate and a third transmission line arranged on the front surface of the first longitudinal dielectric substrate;

[0023] The first transmission line is an L-shaped transmission line with a gradually changing width, one end of which is connected to the tapered transmission line, and the other end is connected to one end of the second transmission line, and the connection position is located on the center line of the first longitudinal dielectric substrate; the second transmission line is an L-shaped transmission line with a uniform line width and greater than the line width of the first transmission line, and the other end thereof is open; the third transmission line is an open rectangular ring metal patch that is symmetric about the left and right, and the opening position is located in the upper branch, and the lower branch of the open rectangular ring metal patch is connected to the metal floor to form a short circuit structure, and the upper branch extends two arms to connect to the dipole.

[0024] Further, the lower side of the open rectangular ring metal patch is connected to the metal floor through a metal via or directly welded to the metal floor.

[0025] Further, the distance between adjacent two sets of tapered impedance matching patches is 0.3 mm to 1 mm.

[0026] Further, a row of front tapered metal patches includes 3 to 6 tapered metal patches. In terms of working principle:

[0027] First, the present invention sequentially disposes at least two sets of gradient impedance matching patches from bottom to top on the surface of the second longitudinal dielectric substrate, thereby forming a longitudinal gradient impedance matching layer, achieving a good transformation of the impedance from the dipole radiator to free space; at the same time, there is a certain distance between adjacent gradient impedance matching layers, avoiding the resonance point caused by the overall excessive height of the matching layer; at the same time, the gradient impedance matching patch shares one layer of dielectric substrate with the radiation dipole, reducing the antenna production and manufacturing cost.

[0028] Secondly, the dipole array placed on the floor will introduce a strong inductance at low frequencies due to the influence of the floor. Different from general array antennas that eliminate the coupling between elements, the present invention introduces a strong capacitive coupling by setting metal coupling patches between the elements to offset the influence of the floor, achieve low-frequency impedance matching, and expand the array bandwidth.

[0029] Finally, in the Marchand balun, a large impedance is formed between the first transmission line and the second transmission line, and this impedance is approximately the input impedance of the dipole; a smaller impedance is formed between the second transmission line and the third transmission line, and the end of the second transmission line is open; at the same time, the lower part of the third transmission line is short-circuited, and a smaller impedance is exhibited between its two side arms; therefore, the Marchand balun preferably achieves broadband impedance transformation and the conversion from an unbalanced port to a balanced port; in addition, the present invention etches the gradient transmission line on the horizontally placed transverse dielectric substrate, significantly reducing the profile height caused by the feeding structure.

[0030] In summary, the beneficial effects of the present invention are as follows:

[0031] 1. The present invention designs a novel low-cost gradient broadband wide-angle impedance matching layer, which can achieve impedance matching during large-angle scanning within the bandwidth, and the scanning angles in the E / H planes can reach 70°.

[0032] 2. The present invention etches the impedance gradient line on the horizontally placed transverse dielectric substrate, greatly reducing the overall profile height of the antenna array. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of a 4×4 array of the ultra-wideband large-angle scanning antenna of the present invention;

[0034] Figure 2 It is an overall 3D schematic diagram of the ultra-wideband large-angle scanning antenna unit of the present invention;

[0035] Figure 3 It is a schematic diagram of the structure of the ultra-wideband large-angle scanning antenna unit of the present invention;

[0036] Figure 4 It is a top view of the ultra-wideband large-angle scanning antenna unit of the present invention;

[0037] Figure 5 This is the front view of the ultra-wideband large-angle scanning antenna element of the present invention;

[0038] Figure 6 This is the rear view of the ultra-wideband large-angle scanning antenna element of the present invention;

[0039] Figure 7 This is the simulation curve of the H-plane scanning standing wave ratio of the antenna element in a specific embodiment of the present invention;

[0040] Figure 8 This is the simulation curve of the E-plane scanning standing wave ratio of the antenna element in a specific embodiment of the present invention

[0041] Figure 9 This is the simulation curve of the radiation efficiency of the antenna array in a specific embodiment of the present invention.

[0042] Explanation of the reference numerals in the drawings: 1. Feeding structure, 11. Transverse dielectric substrate, 111. Gradual transmission line, 112. Metal floor, 12. First longitudinal dielectric substrate, 121. First transmission line, 122. Second transmission line, 123. Third transmission line, 124. Metal short-circuit line, 125. Metal coupling patch, 21. Second longitudinal dielectric substrate, 211. Dipole, 212. First group of gradually-varying impedance matching patches, 213. Second group of gradually-varying impedance matching patches. Detailed implementation manners

[0043] The implementation manners of the present invention will be described in detail below with reference to the drawings and embodiments.

[0044] Refer to Figure 1 , a phased array antenna based on loading a gradually-varying impedance matching layer in this embodiment is composed of a plurality of antenna elements arranged periodically. Refer to Figure 2 , Figure 3 , the antenna element includes a feeding structure and a radiation structure.

[0045] The feeding structure includes a transverse dielectric substrate, a first longitudinal dielectric substrate, a metal floor, a gradual transmission line, and a Marchand balun.

[0046] Among them, the length and width of the transverse dielectric substrate are both 52.5 mm, the relative dielectric constant of the dielectric is 2.2, and the thickness is 1.024 mm. The metal floor is disposed on the lower surface of the transverse dielectric substrate. Refer to Figure 4 , the gradual transmission line is a bent linear gradual transmission line disposed on the upper surface of the transverse dielectric substrate, chamfering is performed at the bending position, and the width of the gradual transmission line gradually changes from 3.04 mm to 0.56 mm; one end of the gradual transmission line serves as a feeding input port and the other end is connected to the first transmission line.

[0047] The upper surface of the horizontal dielectric substrate is provided with a groove for embedding the first longitudinal dielectric substrate; the lower end of the first longitudinal dielectric substrate is embedded in the groove. The height of the first longitudinal dielectric substrate is 46 mm, the width is 52.5 mm, the dielectric constant is 2.2, and the thickness is 1.024 mm.

[0048] The Marchand balun is used to achieve broadband impedance matching. Refer to Figure 5 、 Figure 6 , and includes a first transmission line and a second transmission line disposed on the back surface of the first longitudinal dielectric substrate, and a third transmission line disposed on the front surface of the first longitudinal dielectric substrate. The first transmission line is an L-shaped transmission line with a width gradually changing from 0.56 mm to 0.2 mm. One end thereof is connected to the tapered transmission line, and the other end is connected to one end of the second transmission line, and the connection position is located on the center line of the first longitudinal dielectric substrate. The second transmission line is an L-shaped transmission line with a line width of 4.3 mm. The end connected to the first transmission line is chamfered, and the other end is open-circuited. The third transmission line is an open rectangular loop metal patch, the arm width thereof is 35 mm, the inner side length is 25 mm, and the width of the open slit in the upper side branch is 0.5 mm; the lower side branch of the open rectangular loop metal patch is welded to the metal floor to form a short-circuit structure, and the upper side branch extends out of the two arms to connect the dipole.

[0049] The radiation structure includes a second longitudinal dielectric substrate, a dipole, and an impedance matching patch structure.

[0050] Among them, the second longitudinal dielectric substrate is an extension section of the first longitudinal dielectric substrate upward, and the extended length is 41.5 mm.

[0051] The dipole includes two dipole arms disposed on the front surface of the second longitudinal dielectric substrate and mirror-symmetrical. The dipole arms are composed of an isosceles trapezoidal part with an upper base length of 2 mm, a lower base length of 15 mm, and a height of 12.2 mm, and a rectangular part with a length of 13.8 mm and a width of 15 mm. The upper bases of the isosceles trapezoidal parts of the two dipole arms are oppositely arranged with a spacing of 0.5 mm, and the rectangular part is an extension of the lower base; the two dipole arms are connected to the balanced output ends of the Marchand balun; a narrow slit with a width of 0.4 mm is provided between the dipole arms of adjacent antenna units.

[0052] The impedance matching patch structure includes a first set of tapered impedance matching patches and a second set of tapered impedance matching patches that are sequentially arranged on the surface of the second longitudinal dielectric substrate from bottom to top. The heights of the two sets of tapered impedance matching patches are both 24 mm, and each includes 4 front tapered metal patches and 4 back tapered metal patches whose projections coincide with them. Among them, the distance between the first set of tapered impedance matching patches and the dipole is 0.65 mm. The widths of the tapered metal patches gradually change from 11.8 mm to 10.8 mm, and the widths of the gaps between the corresponding tapered metal patches gradually change from 1.3 mm to 2.33 mm. The distance between the second set of tapered impedance matching patches and the first set of tapered impedance matching patches is 0.5 mm. The widths of the tapered metal patches gradually change from 10.68 mm to 8.13 mm, and the widths of the gaps between the corresponding tapered metal patches gradually change from 2.44 mm to 5 mm; that is, the width of the tapered impedance matching patch on the upper side is greater than the width of the tapered impedance matching patch on the lower side.

[0053] The antenna unit further includes two metal coupling patches arranged on the back surface of the second longitudinal dielectric substrate and a metal short circuit line arranged on the back surface of the first longitudinal dielectric substrate. The projections of the two metal coupling patches are respectively located at the ends of the two dipole arms, and the metal coupling patches of adjacent antenna units are connected to form an integral rectangular shape and are connected to the metal floor through the metal short circuit line; among them, the length of the metal coupling patch is 8 mm and the width is 9 mm, and the line width of the metal short circuit line is 2 mm.

[0054] The simulation result of the unit active standing wave of the infinite planar array based on the unit described in the above embodiment is as Figure 6 shown. As can be seen from the figure, this embodiment has a working bandwidth of 0.73 - 1.66 GHz (2.27:1), and the unit active standing wave during the E-plane and H-plane scans of the array is lower than 2.5, that is, the scanning range of ±70° in the E-plane and H-plane is achieved.

[0055] The simulation result of the unit efficiency of the infinite planar array based on the unit described in the above embodiment is as Figure 9 shown. As can be seen from the figure, the efficiency of this embodiment is higher than 80% in the frequency band of 0.73 - 1.66 GHz.

[0056] The above is only a specific embodiment of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An ultra-wideband, wide-angle scanning phased array antenna based on a gradient impedance matching layer, characterized in that: The phased array antenna is composed of a number of antenna units arranged periodically; The antenna unit includes a feeding structure and a radiation structure; The feeding structure includes a transverse dielectric substrate, a first longitudinal dielectric substrate, a metal floor, a gradient transmission line, and a Marchand balun; The metal floor is arranged on the lower surface of the lateral dielectric substrate; The tapered transmission line is arranged on the upper surface of the lateral dielectric substrate, one end of which serves as a feed input port and the other end of which is connected to the unbalanced input end of the Marchand balun; The first longitudinal dielectric substrate is vertically placed above the transverse dielectric substrate; The Marchand balun is arranged on the surface of the first longitudinal dielectric substrate, and comprises an unbalanced input end and a balanced output end, and is used to achieve broadband impedance matching; The radiation structure includes a second longitudinal dielectric substrate, a dipole, and an impedance matching patch structure; The second longitudinal dielectric substrate is an upward extension of the first longitudinal dielectric substrate; The dipole comprises two dipole arms which are arranged on the front side of the second longitudinal dielectric substrate and are mirror-symmetrical, and the two dipole arms are connected to the balanced output end of the Marchand balun; a narrow gap is arranged between the dipole arms of adjacent antenna units; The impedance matching patch structure comprises at least two groups of gradient impedance matching patches arranged in sequence from bottom to top on the surface of the second longitudinal dielectric substrate; each group of gradient impedance matching patches comprises a row of front gradient metal patches and a row of back gradient metal patches overlapping with their projections, and the gradient metal patches are all gradient structures with gradually decreasing width from bottom to top; each group of gradient impedance matching patches and the second longitudinal dielectric substrate in between them together constitute a gradient impedance matching layer, which is used to improve the large-angle scanning capability.

2. The ultra-wideband large-angle scanning phased array antenna based on a gradient impedance matching layer as claimed in claim 1, characterized in that: The antenna unit also includes two metal coupling patches arranged on the back side of the second longitudinal dielectric substrate and a metal short-circuit line arranged on the back side of the first longitudinal dielectric substrate; the projections of the two metal coupling patches are respectively located at the ends of the two dipole arms, and the metal coupling patches of adjacent antenna units are connected to each other and connected to the metal floor through the metal short-circuit line.

3. The ultra-wideband large-angle scanning phased array antenna based on a gradient impedance matching layer as claimed in claim 2, characterized in that: The Marchand balun includes a first transmission line and a second transmission line arranged on the back side of the first longitudinal dielectric substrate, and a third transmission line arranged on the front side of the first longitudinal dielectric substrate; The first transmission line is an L-shaped transmission line with a gradient width, one end of which is connected to the gradient transmission line, and the other end is connected to one end of the second transmission line, and the connection position is located on the midline of the first longitudinal dielectric substrate; the second transmission line is an L-shaped transmission line with a uniform line width and greater than the line width of the first transmission line, and the other end of which is open-circuited; the third transmission line is an open rectangular ring metal patch with left-right mirror symmetry, and its opening position is located in the upper branch, the lower branch of the open rectangular ring metal patch is connected to the metal floor to form a short-circuit structure, and the upper branch extends two arms to connect the dipole.

4. The ultra-wideband large-angle scanning phased array antenna based on a gradient impedance matching layer as claimed in claim 3, characterized in that: The lower side of the open rectangular ring metal patch is connected to the metal floor through a metal via, or is directly connected to the metal floor by welding.

5. The ultra-wideband large-angle scanning phased array antenna based on a gradient impedance matching layer as claimed in claim 4, characterized in that: The gradient transmission line is a bent step gradient transmission line, a linear gradient transmission line or an exponential gradient transmission line.

6. The ultra-wideband large-angle scanning phased array antenna based on a gradient impedance matching layer as claimed in claim 4 or 5, characterized in that: The spacing between two adjacent groups of tapered impedance matching patches is 0.3 mm to 1 mm.

7. The ultra-wideband large-angle scanning phased array antenna based on a gradient impedance matching layer as claimed in claim 6, characterized in that: A row of front gradient metal patches includes 3 to 6 gradient metal patches.

Images