CN109888488B - Low-profile and low-scattering ultra-broadband phased array based on polarization-selective absorber loading - Google Patents

Abstract

The invention discloses a kind of low scattering ultra wide band phased arrays of low section based on the load of polarization selectivity wave absorbing device, this it the scanning of face ± 60 ° E and the scanning of face ± 60 ° H are realized in the broadband of 6-18GHz, section height is only the 0.42 of high frequency (18GHz) wavelength.The polarization grid of radiation patch unit back up can effectively improve the cross polarization of antenna, the polarization selectivity wave absorbing device of load is not under the premise of influencing antenna itself radiance simultaneously, the cross polarization RCS for reducing antenna itself significantly within the scope of the full range frequency of Antenna Operation frequency also has good assimilation effect for the cross polarization electromagnetic wave of large angle incidence.

Description

Low-profile and low-scattering ultra-broadband phased array based on polarization-selective absorber loading

technical field

The invention belongs to the technical field of antenna engineering, in particular to a low-profile, low-scattering ultra-wide bandwidth angle-scanning phased antenna array system, specifically a polarized selective absorber (Polarization Sensitive) based on the strong mutual coupling effect Metamaterial Absorber, PSMA), with a low profile, good scattering characteristics, and a phased antenna array that can realize ultra-wide bandwidth angular scanning. It is especially suitable for platforms that require antennas with good stealth performance and low profile characteristics, and can achieve ultra-wide bandwidth angular scanning.

Background technique

With the development of information warfare, especially the rapid progress of radar detection technology, stealth technology occupies an increasingly important position in modern electronic warfare. Radar Cross Section (Radar Cross Section), referred to as RCS, is an important indicator to measure the stealth performance of the detected target. The size of the radar cross-section directly determines the stealth performance of the detected target. As one of the strong scattering sources of the carrier platform, the antenna has a huge impact on its RCS. As an active target, the antenna must be able to send and receive electromagnetic waves normally when performing stealth processing on it. Therefore, conventional stealth methods cannot directly act on the antenna. Since the traditional broadband phased array does not consider the mutual coupling between elements when designing the array elements, the operating bandwidth of the phased array is greatly affected after the array is assembled. Moreover, traditional phased array units with broadband characteristics generally have larger horizontal or vertical dimensions. If the lateral size is too large, it will affect the wide bandwidth angular scanning characteristics of the phased array; if the vertical size is too large, it will not be suitable for the realization of the planar structure, and it will not be easy to conform.

The broadband phased array antenna based on the strong mutual coupling effect is a new concept phased array antenna proposed internationally in recent years. Compared with the traditional phased array, this new type of phased array antenna with closely arranged units is more suitable for miniaturization And the design of wide bandwidth angular scanning characteristics. In 2003, Professor B. Munk of Ohio State University proposed this new wideband phased array for the first time in US Patent No. 6512487 patent "Wideband Phased Array Antenna and Associated Methods" (Wideband Phased Array Antenna and Associated Methods). It is characterized by reducing the distance, strengthening the coupling, and directly using the strong mutual coupling effect between units to form a continuous current, which overcomes the limitation of the mutual coupling effect on the antenna bandwidth and scanning angle. Research in recent years has shown that the strong mutual coupling broadband phased array antenna has very good ultra-wideband characteristics, and a wider grating-free scanning angle than the traditional phased array antenna. In addition, it also has a low profile and is flat as a whole. The structure is easy to achieve conformal shape with aircraft and other carriers, and has little influence on the overall aerodynamic performance of the carrier. However, this strong mutual coupling phased array still has disadvantages such as high antenna profile and poor two-dimensional scanning effect. At the same time, the team did not study or control the antenna scattering characteristics, so the antenna itself does not have low RCS characteristics.

Metamaterials are materials whose structures are artificially designed. Their properties are derived from their precise geometric structures and sizes. The microstructures are smaller than the wavelength they act on. In 2008, Landy proposed a wave-absorbing metamaterial on the basis of metamaterials. When electromagnetic waves are incident on the wave-absorbing metamaterial, this material exhibits complete absorption characteristics because it neither reflects nor transmits electromagnetic waves. Due to its perfect electromagnetic wave absorption performance, absorbing metamaterials open up new ideas for the stealth design of antennas.

In Chinese Patent Application No. 201110321595.7, "Low RCS Microstrip Antenna Based on Complete Absorber", a microstrip antenna designed based on the wave-absorbing properties of the wave-absorbing metamaterial is proposed. On the floor of the microstrip antenna After loading the absorbing metamaterial, the RCS of the microstrip antenna can be reduced by 8-15dB. However, since the microstrip antenna design itself is a narrow-band structure, its own working frequency band is not wide, it is difficult to meet the ultra-wideband characteristics required by modern radar systems, and it is also difficult to achieve the wide-angle scanning performance of the phased array. At the same time, the microwave-absorbing metamaterial designed by this patent is composed of a metal ring, and its working frequency band is narrow, so it cannot be applied to the antenna form with ultra-wideband characteristics.

In order to further optimize the radiation performance of strongly coupled antenna arrays and control their scattering performance, some improved forms of strongly coupled antenna arrays have been proposed. The Chinese patent application number is 201710509295.9 patent "Low-profile low-RCS ultra-wide bandwidth angular scanning strong mutual coupling phased array antenna based on polarization conversion material". Reducing the RCS of the antenna has a certain effect. However, in order not to affect the radiation performance of the antenna, this structure is only suitable for RCS reduction outside the working frequency band of the antenna.

Stefan Varault published an article entitled "RCS Reduction with a Dual polarized self-ComplementaryConnected Array Antenna" in IEEE Transactions on Antennas and Propagation in 2017. This article proposes a circuit model of a dual-polarized checkerboard-shaped self-complementary antenna. Using this circuit model to quickly optimize the reflection coefficient of the array unit, a phased array with ultra-wideband and low-scattering characteristics is finally designed. However, when optimizing the scattering of the antenna, this article only considered the scattering of the mode item of the antenna, and did not have a specific analysis of the scattering of the structural item of the antenna. In addition, the designer did not design a suitable feed structure for this antenna, but only considered the antenna radiation characteristics under ideal conditions. Therefore, the engineering realization of this antenna is still a big challenge.

In the Chinese patent "Improved low-profile low-scattering strong-coupling ultra-broadband phased array" with application number 201810200308.9, a design idea for the balance of radiation and scattering in phased array antenna design is proposed, but when evaluating its scattering characteristics , only considers the single-station RCS when the co-polarized wave is incident vertically, and does not reduce the RCS when the cross-polarized wave is incident, and does not give the RCS reduction effect when the electromagnetic wave is obliquely incident at a large angle.

In the Chinese patent "A Low RCS Ultra-Wideband Connected Long Slot Antenna Array Based on Resistive Metamaterial Loading" with the application number 201811565247.2, it is proposed to load periodically arranged resistive patches on the strongly coupled connected long slot antenna . The resistive patch constitutes an electromagnetic metamaterial with frequency selectivity, and realizes wideband and large-angle RCS reduction outside the working frequency band of the antenna without affecting the radiation performance of the antenna basically. However, this patent does not reduce the RCS within the working frequency band of the antenna.

Based on the above application requirements, the present invention proposes a low-profile low-scattering ultra-wideband phased array loaded by a polarization-selective absorber, which realizes RCS reduction when cross-polarized electromagnetic waves are incident within the working frequency band of the antenna, and simultaneously evaluates The RCS reduction effect of oblique incidence of electromagnetic waves at different angles is shown.

Contents of the invention

Under the background of the above-mentioned invention, the present invention proposes a novel low-scattering ultra-broadband strong mutual coupling phase that loads a polarization-selective absorber (PSMA) above the radiation sheet on the basis of Munk's theory of strongly coupled antenna arrays. control array antenna. In the 6-18GHz frequency band, the E-plane ±60°, the H-plane ±60° scanning performance, the wide-bandwidth angular scanning performance with a VSWR of less than 3, and the total section height of the antenna (including the wide-angle impedance matching layer) is only 0.42 high frequency (18GHz) wavelength. And by placing multiple layers of periodically arranged resistive patches between the wide-angle impedance matching layers, a loaded absorber is formed. The absorber can operate in the antenna working frequency band without affecting the antenna radiation performance. Significantly reduces the RCS of the incident wave as a cross-polarized electromagnetic wave.

The technical solution proposed by the present invention is as follows: use the strong mutual coupling dipole printed on the dielectric layer as the radiation unit of the antenna, and print a rectangular patch on the back of the dipole radiation unit to strengthen the terminal coupling. The dielectric layer of the dipole radiation unit and the metal ground are supported by a dielectric substrate, and holes are drilled on the dielectric substrate to reduce the equivalent dielectric constant and move the scanning blind spot caused by surface waves out of the working frequency band. At the same time, the antenna adopts an unbalanced feed structure, and the metallized vias at both ends of the dipole arm are grounded, so that the common-mode resonance caused by the unbalanced feed is moved out of the working frequency band of the antenna. Two layers of wide-angle matching layers are placed above the dipole radiating unit to compensate for changes in antenna radiation impedance during phased array scanning and improve the wide-angle scanning capability of strongly mutually coupled phased arrays. In order to load the absorber above the antenna to improve the antenna's scattering performance without increasing the height of the section, the resistive patches that are periodically arranged are placed between the wide-angle matching layers, and the printed on the back of the dipole radiating unit Together, the polarization grids form the absorber. The whole antenna array is formed by the periodic structure of above-mentioned antenna unit, therefore, the antenna unit structure of the present invention comprises: the unbalanced feeding structure (1) of antenna; The metal short-circuit post (2) that is used to suppress common-mode resonance; Has certain thickness The metal floor (3); the dielectric substrate (4) used to support the antenna structure; the dipole radiating unit (5); the capacitor sheet (6) on the back of the dipole radiating unit; the printed on the back of the dipole radiating unit Polarized grid (7); the first wide-angle impedance matching layer (8); the second wide-angle impedance matching layer (9); the first layer has a snake-shaped resistive patch with self-coupling capacitance (10); the second Parallel capacitive resistors (11) loaded at the end of one layer of resistive patch unit; second layer of resistive patch (12).

The innovation of the present invention lies in that: a wave absorber with polarization selectivity is loaded above the strong-coupling antenna unit, while reducing antenna scattering, the radiation performance of the antenna is basically not affected, and the low-profile characteristic of the antenna is ensured. The absorber is composed of three parts: periodically arranged resistive patch, polarization grid and dielectric layer. Among them, the dielectric layer is not only used to form a wave absorber, but also serves as a wide-angle impedance matching layer to compensate for impedance changes caused by antenna scanning, improve wide-angle scanning standing waves, and reduce mode term scattering within the antenna's operating frequency band. The polarization grid is printed on the back of the dipole radiating unit in a strip shape perpendicular to the radiating patch. This structure replaces the metal ground of the absorber, so that the distance between the resistive patch and the ground is reduced. Furthermore, the change trend of the reactance caused by the metal ground with frequency is more gentle than before, which is beneficial to realize impedance matching in a wide frequency band. In addition to the above functions, the polarization grid can also reduce the cross-polarization of the antenna at low frequencies; the polarization grid printed on the back can reflect the cross-polarization component of the back radiation of the dipole unit, and because the polarization grid and the dipole The distance between them is only 0.03 high-frequency (18GH) wavelengths, the reflected cross-polarized component and the forward radiation are superimposed in antiphase, and the cross-polarized radiation beams cancel each other out. The periodic resistive patch is not a simple long strip; it is slightly changed on the basis of the long strip, adopting a winding and serpentine shape. This shape produces self-coupling capacitance, which compensates the inductance caused by the metal ground, and is more conducive to the impedance matching between the absorber and free space. At the end of the first layer of periodic resistive patch units, a parallel capacitive sheet structure is added to enhance the coupling between the units. This method improves the absorption efficiency of the absorber at low frequencies, thereby effectively reducing the scattering of the structural items of the antenna.

To sum up, the benefit of the present invention is that a low-profile low-scattering ultra-broadband phased array based on polarization-selective absorber loading is proposed. In the 6-18GHz frequency band, it realizes that the E-plane and H-plane ±60° scanning VSWR is less than 3, and at the same time, it can significantly reduce the normal incidence time in the full frequency band of the antenna without affecting the radiation performance of the antenna itself. Cross polarized RCS. Moreover, the absorber can greatly reduce the scattering of the antenna in the large angle range of the X-band.

Description of drawings

Figure 1 is a perspective view of a low-profile low-scattering ultra-wideband phased antenna array based on polarization-selective absorbers. The antenna array shown in this figure is 7×14 in size.

Fig. 2 is a structural diagram of a periodic unit in Fig. 1, and the low-profile low-scattering ultra-wideband phased antenna array loaded by the polarization-selective absorber described in Fig. 1 includes a series of such structures arranged periodically. Each such periodic unit includes the following parts: an unbalanced feed structure for the antenna (1); a metal short-circuit column (2) for suppressing common-mode resonance; a metal floor with a certain thickness (3); for supporting the antenna The dielectric substrate (4) of the structure; the dipole radiation unit (5); the polarization grid (7) printed on the back of the dipole radiation unit; the wide-angle impedance matching layer (8) (9); Resistive patches (10)(11)(12).

Fig. 3 is the standing wave ratio of the antenna unit in the specific embodiment 1 when scanning the H surface in the 6-18GHz frequency band. It can be seen from the figure that the low-profile low-scattering ultra-wideband phased antenna array developed in Example 1 based on the polarization-selective absorber load has a standing wave ratio of less than 3.0 when scanning the H plane at 0-60° in the 6-18GHz frequency band.

Fig. 4 is the standing wave ratio of the antenna unit in the specific embodiment 1 when scanning the E plane in the 6-18 GHz frequency band. It can be seen from the figure that the low-profile and low-scattering ultra-broadband phased antenna array developed in Example 1 based on the polarization-selective absorber load has a standing wave ratio of less than 3.0 when the E-plane 0-60° scans in the 6-18GHz frequency band.

Fig. 5 is a comparison diagram of the main polarization and cross polarization when the antenna unit in the 6-18GHz full frequency band is side-firing with a polarization-selective absorber loaded above the antenna radiation patch and without implementing the above method in Embodiment 2. It can be seen from the figure that after implementing the above method, the full-band gain is basically the same as that without implementing the above method, and the cross polarization is reduced by more than 10dB compared with before. It is illustrated that the implementation of the above method basically does not affect the main polarization gain of the antenna, and greatly improves the cross polarization.

Fig. 6 is the single-station RCS result graph when the cross-polarized wave is vertically incident in the specific embodiment 2, and it also shows the cross-polarized wave vertically incident in the case of embodiment 2 without the polarized selective absorber The single-station RCS result plots for comparison. It can be seen that when the cross-polarized wave is vertically incident, Example 2 has a significant RCS reduction effect in the whole frequency band.

Fig. 7 is the radiation efficiency of the antenna in the side-firing of the specific embodiment 2. It can be seen from the figure that the radiation efficiency of the antenna is above 92% in the whole frequency band where the antenna works, and the radiation efficiency of 6GHz-17GHz is above 97%.

Fig. 8 is a single-site RCS result graph when the cross-polarized waves are obliquely incident from the E plane and the H plane at 60° angles before and after loading the polarization selective absorber in the specific embodiment 2. It can be seen that when the cross-polarized wave is obliquely incident at a large angle, the working frequency band of the antenna in Example 2 has a significant RCS reduction effect.

Fig. 9 is a diagram of single-station RCS results of the antenna when 12 GHz cross-polarized waves are incident from different angles of the E plane and the H plane before and after loading the polarization selective absorber in the specific embodiment 2. It can be seen from the figure that Example 2 has better scattering characteristics in a large angle range.

Fig. 10 is the radiation pattern of the specific embodiment 1, the operating frequency of the antenna is 12 GHz, and the side-firing and scanning angles are 30° and 60°. It can be seen from the figure that the array has stable beam pointing in side-firing and different scanning angles, and the radiation performance during scanning is good.

specific implementation plan

Example 1

Referring to Fig. 1 to Fig. 2, embodiment 1 is composed of a layer of periodic structure printed with closely arranged even units, and uses periodic boundary conditions to simulate the simulation of the present invention in an infinite array environment. The structure of the antenna unit of the present invention is described as follows: the unbalanced feeding structure (1) of the antenna; the metal short-circuit column (2) for suppressing common mode resonance; the metal floor (3) with a certain thickness; The dielectric substrate (4); the dipole radiation unit (5); the capacitor sheet (6) on the back of the dipole unit; the polarization grid (7) printed on the back of the radiation unit; the first wide-angle impedance matching layer (8 ); the second layer wide-angle impedance matching layer (9); the first layer has a snake-shaped resistive patch (10) with self-coupling capacitance; the parallel capacitive block (11) loaded at the end of the first layer resistive patch unit ; The second layer of resistive patch (12).

3 to 6 show the standing wave ratio and radiation characteristics of the unit in embodiment 1 during scanning. It can be seen from FIG. 3 and FIG. 4 that the broadband phased array of the first embodiment has at least a 3:1 impedance bandwidth, and realizes two-dimensional wide-angle scanning in the range of 6-186 Hz. It can be seen from Figure 5 that after the absorber is loaded on the antenna radiation patch, its full-band gain is basically the same as that without the above method, which shows that the loading of the resistive material has no obvious deterioration effect on the radiation performance of the antenna. Moreover, after loading the absorber, the cross-polarization of the antenna is greatly improved.

Figure 10 shows the radiation pattern of Example 1. It can be seen from Figure 10 that the antenna array has stable beam pointing at different scanning angles, indicating that the radiation performance during scanning is good.

Example 2

specifically. Extending each antenna unit (as shown in Figure 2) along the two-dimensional direction of the front can constitute a low-profile low-scattering ultra-wideband phase-controlled antenna loaded by a 7×14 polarization-selective absorber in Figure 1. array. Other structures are the same as those in Embodiment 1, and will not be repeated here.

Considering the conditions of the existing simulation hardware facilities, the RCS of the array antenna in the first embodiment adopts the unit analysis method for the RCS of the phased array antenna in the electromagnetic simulation, and the unit is simulated under periodic boundary conditions. Figures 7 to 9 show the comparison diagrams of the single-station RCS results at different angles of incidence in Example 2 and Example 2 without absorbers. It can be seen that the phased array developed in Example 2 has good performance. Low RCS characteristics.

In this implementation example, the array is a 10×10 area array composed of periodic units shown in FIG. 2 . Based on the antenna unit described in Figure 2, the infinite array environment can be extended to any practical finite array according to actual application requirements.

Having described various embodiments of the present invention, it should be understood that they have been presented by way of example only, and not limitation. Accordingly, it will be apparent to those skilled in the art that various changes in form and details can be made without departing from the spirit and scope of the invention without requiring inventive effort. All of the above should be considered as the scope of the present invention.

Claims (4)

1. A low-profile low-scattering ultra-broadband phased array based on polarization-selective absorber loading, which includes: an unbalanced feed structure (1) for the antenna; two metal short-circuit columns (2); metal with a certain thickness floor (3); a dielectric substrate (4) positioned above the metal floor for support; a dipole radiation unit (5) with a strong capacitive coupling structure printed on the upper surface of the supporting dielectric substrate, and the two metal short-circuit columns are respectively set On the left and right arms of the dipole radiating element; the capacitive sheet (6) printed on the back of the dipole radiating element; the polarization grid (7) printed on the back of the dipole radiating element; the first layer above the supporting dielectric substrate A wide-angle impedance matching layer (8); a second layer of wide-angle impedance matching layer (9) located above the first layer of wide-angle impedance matching layer; placed between the first layer of wide-angle impedance matching layer and the second layer of wide-angle impedance matching The first layer between the layers has a snake-shaped resistive patch (10) with self-coupling capacitance; a parallel capacitive resistive patch (11) loaded at the end of the snake-shaped resistive patch unit; placed on the second layer wide-angle impedance The second layer of resistive patch (12) on the upper surface of the matching layer; the loaded polarization selective absorber consists of: multilayer resistive patch (10)(11)(12), first layer and second layer The wide-angle impedance matching layer (8) (9) and the polarization grid (7) are composed of three parts. 2. The low-profile low-scattering ultra-broadband phased array loaded based on the polarization-selective wave absorber according to claim 1, wherein a multilayer resistive patch is placed between wide-angle impedance matching layers; A wave absorber is loaded above the strong-coupling antenna unit to reduce antenna scattering while ensuring the low-profile characteristics of the antenna. 3. The low-profile low-scattering ultra-broadband phased array loaded based on the polarization-selective absorber according to claim 1, further characterized in that the polarization-selective absorbing is loaded above the dipole radiation unit of the antenna The absorber can not only absorb the normal incident electromagnetic wave in the full frequency band of the antenna, but also is insensitive to the incident angle of the electromagnetic wave, and can significantly reduce the RCS of the antenna in the wide frequency band and large angle range; and the loaded absorber , has the characteristic of polarization selection, and ensures that the antenna has a high radiation efficiency. 4. The low-profile low-scattering ultra-broadband phased array based on polarization-selective absorber loading according to claim 1, further characterized in that: the polarization grid printed on the back of the dipole radiation unit is canceled by reflection The principle can greatly reduce cross-polarization within the antenna operating frequency band.