Annular ultra-wide frequency selective surface unit based on liquid crystal material and antenna

Abstract

The invention relates to an annular ultra-wide frequency selective surface unit based on a liquid crystal material and an antenna. The annular ultra-wide frequency selective surface unit sequentially comprises a first dielectric layer, a first metal tuning patch layer, a liquid crystal substrate, a second metal tuning patch layer and a second dielectric layer from top to bottom, on the X frequency band, the first metal tuning patch layer is inductive, the second metal tuning patch layer is capacitive, the sizes of patches in the first metal tuning patch layer and the second metal tuning patch layer are changed, so that the interaction of equivalent inductance and equivalent capacitance between the patches is tuned, the band elimination function is achieved, the liquid crystal substrate is equivalent to a variable capacitor, and the band elimination function is achieved. The dielectric constant is changed through the electric adjustable characteristic, so that the coupling capacitance of the liquid crystal substrate is changed, and the dynamic adjustment of the resonant frequency is realized. The broadband airborne stealth radar antenna effectively solves the problems that a traditional airborne radar antenna is small in bandwidth and tuning range, and meets the development requirements of a miniaturized and integrated broadband airborne stealth radar antenna.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to an annular ultra-wide frequency selective surface unit and an antenna based on liquid crystal materials. Background Art

[0002] Airborne radar antennas have high gain, narrow beam, and target detection and tracking capabilities. They are one of the main solutions to meet the military's multi-dimensional communication and command requirements. Mechanical scanning, phased array scanning, frequency scanning, phase gradient scanning and other technologies are often used, but they all have certain limitations in some aspects. For example, mechanical scanning is slow and not suitable for rapidly changing targets or scenes. The complex phased array scanning system and the large number of electronic components may cause thermal management problems. Frequency scanning may interfere with other communications or radar systems when changing frequencies. Phase gradient scanning has limited directivity and may require complex algorithms and control strategies to achieve beam shapes. At the same time, the performance trade-offs between antenna gain and stealth, and bandwidth and stealth limit the performance of radar antennas in practical applications. Broadband stealth antennas require materials that can work effectively over a wide frequency range. Traditional materials may find it difficult to simultaneously meet the requirements of stealth, gain and mechanical strength. In summary, traditional radar antennas have been unable to meet the requirements of high flexibility, high stealth, high integration, low cost and fast scanning for military communication applications.

[0003] Frequency Selective Surface (FSS) is a key technology to achieve antenna stealth. FSS is an electromagnetic surface composed of periodically arranged conductive units, which can selectively transmit or reflect electromagnetic waves according to the frequency, polarization state and incident angle of the electromagnetic waves. FSS can be designed to transmit electromagnetic waves within a specific frequency range and reflect electromagnetic waves within other frequency ranges. When the antenna system on the aircraft uses FSS, it can selectively transmit electromagnetic waves of the operating frequency and reflect electromagnetic waves of the non-operating frequency, thereby reducing the radar cross-section (RCS) of the antenna system and achieving a stealth effect. FSS can be used as part of the radome and integrated with the antenna system to improve not only the stealth performance of the antenna, but also the overall performance and reliability of the antenna.

[0004] At present, the research on frequency selective surfaces has achieved some results in FSS unit design and wider frequency range. Currently, one-dimensional and two-dimensional periodic arrays are mostly used, or units with different periods are combined to realize multi-band FSS. However, the traditional FSS structure is usually fixed in design and can only work at its design frequency. Due to the limitations of periodicity and unit size, its flexibility and bandwidth are usually limited, which is not conducive to further realizing the stealth performance of airborne radar antennas in a wide frequency band and improving its practical application value. Therefore, it is necessary to combine new materials and new structures to design a new frequency selective surface with wide-band bandstop to optimize the broadband stealth performance of existing radar antennas.

[0005] In the current design of radar stealth antennas, commonly used FSS structures include patch type and aperture type. However, in actual design applications, in order to achieve the purpose of reducing the radar scattering cross section and improving antenna performance, a comprehensive design method is usually adopted to comprehensively design the basic units of the two to obtain an excellent FSS that meets the indicators. In addition, the design of traditional FSS often has a certain staticity. They are designed to work at a specific center frequency or frequency range, which determines that they can only show the best frequency selection characteristics at a predetermined frequency. Once the design is completed, its operating frequency range is fixed and it is difficult to adapt to different frequency requirements. At the same time, due to its physical characteristics of periodicity and size, the bandwidth and flexibility of FSS are limited, and it is difficult to expand to a wider frequency range. These problems make it difficult for airborne radar antennas to further achieve stealth performance in a wide frequency band and meet the actual application scenario requirements in current military communications. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a ring-shaped ultra-wide frequency selective surface unit and antenna based on liquid crystal materials, which solves the shortcomings of the prior art.

[0007] The object of the present invention is achieved by the following technical solution: an annular ultra-wide frequency selective surface unit based on liquid crystal material, which comprises, from top to bottom, a first dielectric layer, a first metal tuning patch layer, a liquid crystal substrate, a second metal tuning patch layer, and a second dielectric layer; In the X-band, the first metal tuning patch layer is inductive, and the second metal tuning patch layer is capacitive. By changing the patch sizes in the first metal tuning patch layer and the second metal tuning patch layer, the equivalent inductance and equivalent capacitance between the patches are tuned to achieve the band-stop function. The liquid crystal substrate is equivalent to a variable capacitor. The dielectric constant is changed by the electrically adjustable characteristics, thereby changing the coupling capacitance of the liquid crystal substrate, thereby achieving dynamic adjustment of the resonant frequency. When an electromagnetic wave is incident on the frequency selective surface unit, the first metal tuning patch layer generates an induced current for the electromagnetic wave. If the frequency of the electromagnetic wave matches the resonant frequency of the frequency selective surface unit, the electromagnetic wave resonates between the frequency selective surface units, causing the electromagnetic wave to be reflected. Otherwise, the electromagnetic wave is transmitted or partially transmitted.

[0008] The first metal tuning patch layer includes a circular patch and a square patch; the circular patch is arranged inside the square patch, and on a two-dimensional horizontal plane, the square patch is regarded as an equivalent capacitor, and the equivalent capacitance is controlled by adjusting the size in combination with the circular patch.

[0009] The second metal tuning patch layer includes a circular patch and a cross-shaped patch; the circular patch is located at the center of the cross-shaped patch, and in the vertical direction, the cross-shaped patch is regarded as two inductors connected across the liquid crystal substrate.

[0010] The annular patch is composed of multiple concentric rings and two crossed metal strips. The two crossed metal strips are connected to the square frame patch, and the multiple concentric rings are arranged on the two crossed metal strips.

[0011] An antenna with an annular ultra-wide frequency selective surface unit based on liquid crystal material, the antenna comprises a plurality of frequency selective surface units, and the plurality of frequency selective surface units are arranged in the form of an array.

[0012] The present invention has the following advantages: a ring-shaped ultra-wide frequency selective surface unit and antenna based on liquid crystal material, which effectively solves the problems of small bandwidth and small tuning range of traditional airborne radar antennas, and meets the development needs of miniaturized, integrated wide-band airborne stealth radar antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the exploded structure of the frequency selective surface unit of the present invention; Figure 2 It is a structural schematic diagram of the antenna of the present invention; In the figure: 1-first dielectric layer, 2-second dielectric layer, 3-liquid crystal substrate, 4-annular patch, 5-square patch, 6-circular patch, 7-cross patch. DETAILED DESCRIPTION

[0014] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the detailed description of the embodiments of the present application provided below in conjunction with the drawings is not intended to limit the scope of protection of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application. The present invention is further described below in conjunction with the drawings.

[0015] One of the embodiments of the present invention relates to an annular ultra-wide frequency selective surface (FSS) unit structure based on liquid crystal material. The design mainly works in the X-band. Based on the characteristics of liquid crystal materials, a broadband band-stop frequency selective surface with a resonant structure is designed to effectively solve the problems of small bandwidth and small tuning range of traditional airborne radar antennas, and meet the development needs of miniaturized, integrated wide-band airborne stealth radar antennas.

[0016] like Figure 1 As shown, the frequency selective surface unit based on liquid crystal includes, from top to bottom, a first dielectric layer 1, a first metal tuning patch layer, a liquid crystal substrate 3, a second metal tuning patch layer and a second dielectric layer 2. The first metal tuning patch layer and the second metal tuning patch layer are used as positive and negative electrodes to add a DC bias so that a potential difference can be formed in the liquid crystal material layer to make its dielectric constant electrically adjustable. Among them, the first dielectric layer 1 and the second dielectric layer 2 are both made of RogersRO4035 with a dielectric constant of 3.66, which can reduce the size of the frequency selective surface unit and protect the internal circuit at the same time.

[0017] In the X-band, the first metal tuning patch layer is inductive, and the second metal tuning patch layer is capacitive. By changing the patch sizes in the first metal tuning patch layer and the second metal tuning patch layer, the equivalent inductance and equivalent capacitance between the patches are tuned to interact with each other, thereby realizing the band-stop function. When combined with the liquid crystal material of the liquid crystal substrate 3, it not only broadens the frequency range of the stop band, but also realizes a flat response within the passband and a sharp attenuation characteristic outside the band; the liquid crystal substrate 3 is equivalent to a variable capacitor, and the dielectric constant is changed by the electrically adjustable characteristic, thereby changing the coupling capacitance of the liquid crystal substrate 3, thereby realizing the dynamic adjustment of the resonant frequency; When an electromagnetic wave is incident on the frequency selective surface unit, the first metal tuning patch layer generates an induced current for the electromagnetic wave. If the frequency of the electromagnetic wave matches the resonant frequency of the frequency selective surface unit, the electromagnetic wave resonates between the frequency selective surface units, causing the electromagnetic wave to be reflected. Otherwise, the electromagnetic wave is transmitted or partially transmitted.

[0018] Furthermore, the first metal tuning patch layer includes a circular patch 4 and a square patch 5; the circular patch 4 is arranged inside the square patch 5, and on a two-dimensional horizontal plane, the square patch 5 is regarded as an equivalent capacitor, and combined with the circular patch 4, the equivalent capacitance is controlled by adjusting the size.

[0019] Among them, the annular patch 4 is composed of multiple concentric rings and two crossed metal strips, the two crossed metal strips are connected to the square patch 5, and the multiple concentric rings are arranged on the two crossed metal strips; the ring width is 0.4mm, the maximum circle radius is 2.6mm, and the center radius is 1.3mm.

[0020] Furthermore, the second metal tuning patch layer includes a circular patch 6 and a cross-shaped patch 7 ; the circular patch 6 is located at the center of the cross-shaped patch 7 , and in the vertical direction, the cross-shaped patch 7 is regarded as two inductors connected across the liquid crystal substrate 3 .

[0021] The radar antenna also meets the requirements of wide range tuning, such as Figure 2 As shown, another embodiment of the present invention relates to an antenna with an annular ultra-wide frequency selective surface unit based on liquid crystal material. The antenna includes multiple frequency selective surface units, and the multiple frequency selective surface units are designed to be a 4×4 array to achieve an X-band resonant agile antenna. At the same time, an upper and lower resonant structure is adopted. The array period is reduced through the annular structure, the coupling between units is increased, the resonant frequency is reduced to increase the bandwidth, and it has good frequency stability.

[0022] When a bias voltage is applied to continuously change the dielectric constant of the liquid crystal from 2.4 to 3.2, the resonant frequency of the FSS array will change in the X-band. The central operating frequency is 9.52 GHz, and the tuning bandwidth reaches 3.5 GHz, achieving continuous tunability of the FSS stopband.

[0023] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used for various other combinations, modifications and improvements, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A ring-shaped ultra-wide frequency selective surface unit based on liquid crystal material, characterized in that: It comprises, from top to bottom, a first dielectric layer (1), a first metal tuning patch layer, a liquid crystal substrate (3), a second metal tuning patch layer and a second dielectric layer (2); In the X-band, the first metal tuning patch layer is inductive, and the second metal tuning patch layer is capacitive. By changing the patch sizes in the first metal tuning patch layer and the second metal tuning patch layer, the interaction between the equivalent inductance and equivalent capacitance of the tuning patches is achieved, thereby realizing a band-stop function. The liquid crystal substrate (3) is equivalent to a variable capacitor, and the dielectric constant is changed through the electrically adjustable characteristics, thereby changing the coupling capacitance of the liquid crystal substrate (3), thereby realizing dynamic adjustment of the resonant frequency. When an electromagnetic wave is incident on the frequency selective surface unit, the first metal tuning patch layer generates an induced current for the electromagnetic wave. If the frequency of the electromagnetic wave matches the resonant frequency of the frequency selective surface unit, the electromagnetic wave resonates between the frequency selective surface units, causing the electromagnetic wave to be reflected. Otherwise, the electromagnetic wave is transmitted or partially transmitted.

2. The annular ultra-wide frequency selective surface unit based on liquid crystal material according to claim 1, characterized in that: The first metal tuning patch layer comprises a circular patch (4) and a square patch (5); the circular patch (4) is arranged inside the square patch (5); on a two-dimensional horizontal plane, the square patch (5) is regarded as an equivalent capacitor; and in combination with the circular patch (4), the equivalent capacitance is controlled by adjusting the size.

3. The annular ultra-wide frequency selective surface unit based on liquid crystal material according to claim 1, characterized in that: The second metal tuning patch layer comprises a circular patch (6) and a cross-shaped patch (7); the circular patch (6) is located at the center of the cross-shaped patch (7); in the vertical direction, the cross-shaped patch (7) is regarded as two inductors connected across the liquid crystal substrate (3).

4. The annular ultra-wide frequency selective surface unit based on liquid crystal material according to claim 2, characterized in that: The annular patch (4) is composed of a plurality of concentric circular rings and two crossed metal strips, the two crossed metal strips are connected to the square frame patch (5), and the plurality of concentric circular rings are arranged on the two crossed metal strips.

5. An antenna based on a ring-shaped ultra-wide frequency selective surface unit of liquid crystal material, characterized in that: The antenna comprises a plurality of frequency selective surface units as claimed in any one of claims 1 to 4, and the plurality of frequency selective surface units are arranged in the form of an array.

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