Low-profile ultra-wideband wide-angle scanning phased-array antenna based on tight coupling structure

Abstract

A low-profile ultra-wideband wide-angle scanning phased-array antenna based on a tight coupling structure is composed of a metal floor and a plurality of antenna units, the antenna units extend in the X polarization direction and the Y polarization direction respectively to form a plane of any size, and an antenna array is formed; the antenna unit sequentially comprises an upper substrate, a dipole antenna and a lower substrate from top to bottom, the dipole antenna is vertically and crossly placed and comprises two layers of dielectric substrates and a layer of prepreg between the two layers of dielectric substrates, and a resistor-coated pattern is printed on the upper surface of the lower substrate.

Description

Technical Field

[0001] This invention belongs to the field of phased array antenna technology, specifically relating to a technique for eliminating short-circuit resonance and wide-angle scanning. Background Technology

[0002] Phased array antenna technology is widely used in various radar systems. It can perform rapid wide-angle scanning without moving the antenna, adaptively form multiple beams, have a distributed aperture, low radar cross section, and its overall performance changes little with the extension of working time.

[0003] Radar systems using phased array antennas can achieve beam scanning over a large airspace, acquire target information within a set airspace, quickly and flexibly change the antenna beam and pointing shape, have a short response time and high data rate, and transmit and receive electromagnetic waves of various frequency bands throughout the entire space, accurately achieving multi-target search, tracking, acquisition, and identification.

[0004] With the in-depth application and continuous development of radar systems, the requirements for the ultra-wideband and wide-angle scanning characteristics of antennas have greatly increased, and the requirements for technologies such as lightweight and low profile are also increasing.

[0005] The operating bandwidth and scanning angle of traditional broadband phased array antennas are affected by the mutual coupling effect: the mutual coupling effect between elements causes the feed energy to be coupled from one element to another. This effect affects the antenna's radiation characteristics, deteriorates the scanning standing wave ratio, and distorts the antenna's radiation pattern in an array environment.

[0006] To address the mutual coupling problem of traditional phased arrays, some scholars have proposed the concept of ultra-wideband phased array antennas based on strong mutual coupling effects. Compared with the previous idea of ​​eliminating the mutual coupling effect between elements, tightly coupled phased array antennas utilize the capacitive coupling between elements to offset the inductive loading brought by the ground plane, greatly widening the low-frequency bandwidth of the antenna.

[0007] By loading a wide-angle dielectric matching layer, the impedance matching of the antenna array under large-angle scanning can be improved, thereby increasing the scanning range of the antenna.

[0008] Strongly coupled antennas have small element electrical dimensions, resulting in a small overall antenna array size. However, to achieve a wider bandwidth, they face the limitation of excessively high antenna profile height, which is not conducive to antenna integration conformal design. Summary of the Invention

[0009] To address the aforementioned issues, a low-profile ultra-wideband angular scanning phased array antenna based on a tightly coupled structure was adopted. Based on the ultra-wideband operating principle of the tightly coupled phased array antenna, a double-layer coupled patch structure was proposed to enhance the capacitive coupling between antenna elements, thereby broadening the low-frequency bandwidth of the antenna. A resistive FSS was designed to eliminate the short-circuit resonance point of the antenna and to control the impedance matching of the antenna during large-angle scanning, achieving a large-angle scanning range exceeding ±75°.

[0010] The antenna consists of a metal ground plane and several antenna elements. The antenna elements extend along the X-polarization direction and the Y-polarization direction respectively, forming a plane of arbitrary size to form an antenna array.

[0011] The antenna unit consists of an upper substrate, a dipole antenna, and a lower substrate from top to bottom. The dipole antenna is placed vertically and includes two dielectric substrates and a prepreg layer in between. The upper surface of the lower substrate is printed with a resistive pattern to eliminate the half-wavelength resonant point of the antenna, adjust the low-frequency impedance matching of the antenna when scanning at a large angle, improve the voltage standing wave ratio, and achieve a low profile of the antenna.

[0012] Let the spacing between the antenna elements be... d The height of the antenna element from the metal floor is h The dielectric constant of the filler between the antenna element and the metal ground plane is ε r The dipole antenna is equivalent to an inductor. L dipole Let the input impedance of the antenna be... Z in The characteristic impedance of the antenna to free space is Z 0, the value is Z If Ω = 377Ω, then the impedance from the antenna to the ground is... Z g1 Use the formula Calculate the input impedance of the antenna. Z in Use the formula calculate.

[0013] when At low frequencies, the impedance reactance component increases, meaning the antenna's operating bandwidth is limited. To counteract this reactance component, coupling capacitance is added between tightly coupled antenna elements. C 1 Then the new input impedance Z inc Use the formula Calculate, add The component provides additional capacitance to cancel out low-frequency inductive reactance components, which greatly expands the range compared to traditional antennas.

[0014] when At that time, the impedance from the antenna to the ground Z g1 =0, the antenna array is in a short-circuit state. That is, at this frequency, the electromagnetic waves reflected by the antenna through the ground cancel out the electromagnetic waves radiated by the antenna at the array surface, and no radiation occurs. The overall operating bandwidth is reduced. Adding a resistor between the antenna and the ground is recommended. R res That is, the resistivity pattern R res The impedance of the new antenna to the ground is... Z g2 Use the formula Calculate, when At that time, the impedance from the antenna to the ground Z g2 ≠0, the short-circuit resonant point is eliminated, and the antenna bandwidth increases.

[0015] There is a 1mm air gap between the upper substrate and the dipole antenna, which is filled with foam to match the wide-angle impedance and improve the performance of the antenna element when scanning at a large angle.

[0016] The dipole antenna has a multi-layer PCB structure. The outer surface is printed with a stripline balun, microstrip feed line, and coupling patch, while the inner surface is printed with an X-polarized dipole patch, a Y-polarized dipole patch, and a stripline feed line. The coupling patch increases the capacitive coupling between antenna elements and improves the antenna's operating bandwidth.

[0017] The energy is coaxially fed to the microstrip feed line of the dipole antenna, conducted to the stripline feed line and the dipole patch, and radiated into free space. Attached Figure Description

[0018] Figure 1 This is a diagram of the antenna unit structure.

[0019] Figure 2 This is a diagram of a dipole antenna structure.

[0020] Figure 3 This is an antenna array diagram.

[0021] Figure 4 This is a simulation diagram of the standing wave ratio of the active voltage in the vertical plane.

[0022] Figure 5 This is a simulation diagram of the standing wave ratio of active voltage in the horizontal plane.

[0023] Figure 6 This is the vertical plane gain pattern at 14 GHz under 0° scanning conditions.

[0024] Figure 7 This is the horizontal gain pattern at 14 GHz under 0° scanning conditions.

[0025] Figure 8It shows the vertical plane radiation pattern of the 14GHz frequency point at scanning angles of 0°, 30°, 45°, and 60°.

[0026] Figure 9 It shows the horizontal plane radiation pattern of the 14GHz frequency point at scanning angles of 0°, 30°, 45°, and 60°. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0028] The three-dimensional structure of the antenna element is as follows Figure 1 As shown, the dipole antennas 107 are arranged vertically in a cross pattern. The thickness of the lower substrate 108 is 1 mm, the relative permittivity is 2.92, and the height from the metal ground plane is 3 mm. The upper surface is printed with a resistive pattern 104 with a resistance of 50 ohms, which eliminates the half-wavelength resonant point of the antenna and adjusts the impedance matching of the antenna at low frequencies when scanning at large angles, thereby improving the voltage standing wave ratio.

[0029] The dipole antenna 107 has a relative permittivity of 2.2 and a thickness of 0.6 mm. Its structure is as follows: Figure 2 As shown, the outer surface is printed with a stripline balun 112, a microstrip feed line 113, and a coupling patch 106, while the inner surface is printed with an X-polarized dipole patch 102, a Y-polarized dipole patch 103, and a stripline feed line 111.

[0030] The strip feeder 111 is divided into 7 segments: the first segment is 0.5mm wide and 1mm long; the second segment is 0.4mm wide and 3mm long; the third segment is 0.4mm wide and 1mm long; the fourth segment is 0.35mm wide and 4mm long; the fifth segment is 0.3mm wide and 3.5mm long; the head of the fifth segment is 0.3mm wide, the tail is 1.2mm wide, and the length is 0.6mm; the sixth segment is 1.2mm wide and 3mm long; and the seventh segment is 1.2mm wide and 2mm long.

[0031] The coaxial inner core 114 of the RF connector 105 of the X-polarized unit and the RF connector 110 of the Y-polarized unit conducts current to the microstrip feed line 113 and the stripline feed line 111, and couples energy to the dipole patch 102 through the coupling feeding method, radiating it into free space.

[0032] The size of the antenna array is as follows Figure 3 As shown, the metal ground plane 109 is 7mm thick, the upper substrate 101 is 2mm thick, the relative permittivity is 2.2, it has wide-angle impedance matching, it is supported and fixed with foam, and there is a 1mm air gap between it and the dipole substrate. Twelve antenna elements are arranged along the x-direction with an element spacing of 8.3mm, and twelve antenna elements are arranged along the y-direction with an element spacing of 8.3mm.

[0033] Simulation results of the vertical plane active voltage standing wave ratio as a function of frequency are as follows: Figure 4 As shown, the active voltage standing wave ratio is less than 2.3 throughout the entire 2-18 GHz frequency band.

[0034] Simulation results of the horizontal active voltage standing wave ratio as a function of frequency are as follows: Figure 5 As shown, the active voltage standing wave ratio is less than 3.2 throughout the entire 2-18 GHz frequency band.

[0035] The vertical plane gain pattern at 14 GHz under 0° scanning conditions is shown below. Figure 6 As shown, the cross-polarization performance is good and the waveform is normal.

[0036] The horizontal gain pattern at 14 GHz under 0° scanning conditions is as follows: Figure 7 As shown, the cross-polarization performance is good and the waveform is normal.

[0037] The vertical plane radiation patterns of the 14GHz frequency point at scanning angles of 0°, 30°, 45°, and 60° are as follows: Figure 8 As shown, the scanning beam is stable, the pointing is accurate, and the cross-polarization performance is good.

[0038] The horizontal radiation patterns at the 14GHz frequency point under scanning angles of 0°, 30°, 45°, and 60° are as follows: Figure 9 As shown, the scanning beam is stable, the pointing is accurate, and the cross-polarization performance is good.

[0039] The above are embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A low-profile, ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure, characterized in that, include: It consists of a metal ground plane and several antenna elements, which extend along the X-polarization direction and the Y-polarization direction respectively, forming a plane of arbitrary size to form an antenna array; The antenna unit consists of an upper substrate, a dipole antenna, and a lower substrate from top to bottom. The dipole antennas are arranged vertically and crosswise, including two dielectric substrates and a prepreg layer in between. The upper surface of the lower substrate is printed with a resistive pattern.

2. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 1, characterized in that, The dipole antenna has a multi-layer PCB structure. The outer surface is printed with a stripline balun, a microstrip feed line, and a coupling patch. The inner surface is printed with an X-polarized dipole patch, a Y-polarized dipole patch, and a stripline feed line. The coupling patch increases the capacitive coupling between antenna elements.

3. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 2, characterized in that, The bottom of the X-polarized antenna unit and the Y-polarized antenna unit has an RF connector. The current is conducted to the microstrip feed line and the stripline feed line through the coaxial inner core. The energy is coupled to the dipole patch through the coupling feeding method and radiated into free space.

4. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 2, characterized in that, include: Let the spacing between the antenna elements be... d The height of the antenna element from the metal floor is h The dielectric constant of the filler between the antenna element and the metal ground plane is ε r The dipole antenna is equivalent to an inductor. L dipole Let the input impedance of the antenna be... Z in The characteristic impedance of the antenna to free space is Z If 0, then the impedance from the antenna to the ground is... Z g1 Use the formula Calculate the input impedance of the antenna. Z in Use the formula calculate.

5. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 4, characterized in that, include: when When the impedance reactance component increases, the coupling capacitance component increases between the tightly coupled antenna elements. C 1 New input impedance Z inc Use the formula Calculate, add This component provides additional capacitance to counteract the low-frequency inductive reactance component.

6. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 4, characterized in that, include: when At that time, the impedance from the antenna to the ground Z g1 =0, the antenna array is in a short-circuit state, then add a resistive layer between the antenna and the ground. R res The impedance of the new antenna to the ground Z g2 Use the formula Calculate the impedance from the antenna to the ground. Z g2 ≠0, eliminating short-circuit resonance points.

7. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 2, characterized in that, The strip feeder is divided into 7 segments, including: the first segment is 0.5mm wide and 1mm long; the second segment is 0.4mm wide and 3mm long; the third segment is 0.4mm wide and 1mm long; the fourth segment is 0.35mm wide and 4mm long; the fifth segment is 0.3mm wide and 3.5mm long; the fifth segment has a head width of 0.3mm, a tail width of 1.2mm, and a length of 0.6mm; the sixth segment is 1.2mm wide and 3mm long; and the seventh segment is 1.2mm wide and 2mm long.

8. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 1, characterized in that, The upper substrate has a thickness of 2 mm, a relative permittivity of 2.2, and a 1 mm air gap with the dipole substrate; the dipole antenna has a thickness of 0.6 mm and a relative permittivity of 2.2; the lower substrate has a thickness of 1 mm, a relative permittivity of 2.92, and a height of 3 mm from the metal ground plane; the antenna element spacing is 8.3 mm; and the metal ground plane has a thickness of 7 mm.

9. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 8, characterized in that, Foam is filled between the upper substrate and the dipole antenna.

10. The low-profile ultra-wide bandwidth angular scanning phased array antenna based on a tightly coupled structure according to claim 1, characterized in that, The resistance of the overlay resistor pattern is 50 ohms.

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