Dual-polarization low insertion loss flat bandpass frequency selective surface for radio telescopes

Abstract

The present invention discloses a dual-polarization low-insertion-loss flat-type bandpass frequency selective surface for a radio telescope, which includes three metal layers and two dielectric substrate layers. In addition, the present invention also flexibly adopts slotted capacitive coupling, metal frames and rotationally symmetric metal strips to control the passband range and zero-point transmission effect of the frequency selective surface. Moreover, by optimizing the design with a miniaturized curved structure, not only can the requirements of process processing accuracy be met, but also excellent out-of-band transmission zero-point design standards can be achieved. Finally, the application of semi-cured sheets and the strategy of adjusting the side length of metal patches can meet the bandwidth and loss requirements. This invention provides an efficient, low-loss frequency selection solution with broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of radio astronomy, and more particularly to a dual-polarization low insertion loss flat bandpass frequency selective surface for a radio telescope. Background Art

[0002] As people's demand for exploring the unknown universe in outer space continues to grow, the detection technology of millimeter and submillimeter bands has also made great progress. Satellite microwave atmospheric remote sensing requires devices with high receiving sensitivity to detect weak atmospheric molecular radiation, while traditional spatial filtering structures will bring unacceptable losses and cannot meet the requirements of multi-frequency observation and high-sensitivity and high-efficiency radio source detection and rapid identification. Therefore, domestic and foreign scholars have discussed and studied the performance of frequency selective surfaces for millimeter and submillimeter band signal reception.

[0003] The existing frequency selective surface structures at home and abroad are generally divided into three categories: multi-mode three-dimensional periodic frequency selective surface, printed circuit board (PCB) process frequency selective surface, and all-metal frequency selective surface. Among them, although the multi-layer cascaded three-dimensional periodic structure can achieve higher selectivity, it is relatively large in overall size and inconvenient for practical application; the all-metal structure has high processing requirements and is expensive, and it is not easy to achieve low-pass characteristics. Therefore, a low-loss dual-polarization bandpass frequency selective surface with multi-layer PCB process is proposed. Summary of the invention

[0004] The invention is based on the dual-polarization low insertion loss flat bandpass frequency selective surface design of the millimeter wave radio telescope, with three poles in the passband and one transmission zero point outside the band and a laminated structure, so that the surface has smaller insertion loss and higher angle stability, more flexible optimization and improvement, and a wider range of applications.

[0005] In order to achieve the above object, the present invention is implemented by adopting the following technical solution: the multi-layer bandpass frequency selective surface structure comprises:

[0006] A first metal layer, a second metal layer, a third metal layer, and a first dielectric substrate layer and a second dielectric substrate layer between every two adjacent metal layers;

[0007] The first metal layer, the first dielectric substrate layer, the second metal layer, the second dielectric substrate layer and the third metal layer are sequentially stacked and combined together to form a multi-layer bandpass frequency selective surface structure.

[0008] Furthermore, the first metal layer and the third metal layer are identical square metal patch arrays, which are arranged two-dimensionally and periodically along a horizontal plane.

[0009] Furthermore, the second metal layer is composed of a metal frame and a central rotationally symmetrical metal strip.

[0010] Furthermore, the third metal layer and the second dielectric substrate layer are completely identical to the first metal layer and the first dielectric substrate layer, and are distributed in a horizontal mirror-symmetrical manner.

[0011] Furthermore, the first and third metal layers form an open-slot capacitive coupling.

[0012] Furthermore, the second metal frame and the central rotationally symmetric metal strip respectively control the inductive part and the transmission zero point in the passband of the frequency selective surface.

[0013] Furthermore, the central rotationally symmetrical metal strip adopts a miniaturized bending structure, which not only meets the processing accuracy requirements but also reaches the out-of-band transmission zero point design standard.

[0014] Furthermore, the first dielectric substrate layer and the second metal layer are bonded with a prepreg, and the bandwidth and loss requirements are met by reducing the side length of the metal patch on the same side.

[0015] Beneficial effects of the present invention:

[0016] (1) The present invention introduces an out-of-band transmission zero point by introducing an equivalent series resonant structure in the second metal layer, and further adjusts the zero point position by adjusting the metal structure, thereby achieving the passband characteristics of the low-frequency K band and the stopband characteristics of the high-frequency Q band;

[0017] (2) The present invention achieves the purpose of widening the frequency band and stabilizing the performance at multiple incident angles by using a multi-layer dielectric substrate combined with a multi-resonator;

[0018] (3) By miniaturizing the structural design of the intermediate metal layer, the center frequency required for the passband is met and the physical size is reduced, thereby realizing this low-loss, dual-polarization, low-frequency band passband characteristic selection surface, which is suitable for multi-frequency observation systems in the field of radio astronomy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic structural diagram of a dual-polarization low insertion loss flat bandpass frequency selective surface for a millimeter-wave radio astronomical telescope according to the present invention;

[0021] Figure 2 It is a structural side view of a dual-polarization low insertion loss flat bandpass frequency selective surface for a millimeter wave radio astronomical telescope according to the present invention;

[0022] Figure 3 It is a top view of the first metal layer of the dual-polarization low insertion loss flat bandpass frequency selective surface used for the millimeter wave radio astronomical telescope of the present invention;

[0023] Figure 4 It is a top view of the metal layer of the intermediate layer of the dual-polarization low insertion loss flat bandpass frequency selective surface used for the millimeter wave radio astronomical telescope of the present invention;

[0024] Figure 5 is a dual-polarization frequency response curve diagram of a frequency selective surface in a specific embodiment of the present invention;

[0025] Figure 6 4 is a frequency response curve diagram of a frequency selective surface at different incident angles in a specific embodiment of the present invention.

[0026] In the figure, 1-selected surface, 2-first metal layer, 3-first dielectric substrate layer, 4-second metal layer, 5-second dielectric substrate layer, 6-third metal layer. DETAILED DESCRIPTION

[0027] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Typical embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in the present invention. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0028] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0029] The general concept of the present invention is as follows: The present invention discloses a dual-polarization low insertion loss flat bandpass frequency selective surface for a radio telescope, which is stacked up by three metal structures, two dielectric substrates and one adhesive structure, and introduces inductive and capacitive coupling through the metal and dielectric substrate layers. The two two-dimensional periodic array structures arranged in the first metal layer (2) and the third metal layer (6) can adjust the capacitive coupling strength of the overall frequency selective surface, and the capacitor combined with the dielectric substrate and the inductive structure of the middle layer can produce a basic non-resonant bandpass response to the incident electromagnetic wave; and then introduce a band-stop structure into the middle layer to suppress the out-of-band transmission of the high-frequency part. Compared with the traditional frequency selective surface, the present invention is based on the design of the dual-polarization low insertion loss flat bandpass frequency selective surface of the millimeter-wave radio telescope, with three poles in the passband and one transmission zero point outside the band and a stacked structure, so that the surface has smaller insertion loss and higher angle stability, more flexible optimization and improvement, and a wider range of applications.

[0030] like Figure 1-2 As shown, Figure 1 Shown is a schematic diagram of the structure of a dual-polarization low insertion loss flat bandpass frequency selective surface for a millimeter wave radio telescope, in which (1) is the three-dimensional structure of the selection surface. Figure 2 The figure shows a side view of a dual-polarization low insertion loss flat bandpass frequency selective surface unit structure for a millimeter wave radio telescope, where (3) and (5) are dielectric substrates, the relative dielectric constant of the dielectric substrate F4B is 2.2, and the thickness of the two dielectric substrates is 0.762 mm. The overall plane size of the frequency selective surface is 1.9 mm × 1.9 mm.

[0031] A dual-polarization low insertion loss flat bandpass frequency selective surface (1) for a radio telescope comprises a first metal layer (2), a second metal layer (4), a third metal layer (6), and a first dielectric substrate layer (3) and a second dielectric substrate layer (5) between each two adjacent metal layers. The first metal layer (2) and the third metal layer (6) are identical square metal patch arrays, arranged two-dimensionally periodically along a horizontal plane; the second metal layer (4) is composed of a metal frame (9) and a central rotationally symmetrical metal strip (10); the third metal layer (6) and the second dielectric substrate layer (5) are identical to the first metal layer (2) and the first dielectric substrate layer (3), and are distributed in a horizontal mirror-image symmetrical manner.

[0032] The first metal layer (2) and the third metal layer (6) form an open-slot capacitive coupling; the second metal frame (9) and the central rotationally symmetrical metal strip (10) respectively control the inductive part and the transmission zero point in the passband of the frequency selective surface.

[0033] The central rotationally symmetrical metal strip (10) adopts a miniaturized curved structure, which not only meets the actual processing accuracy requirements but also meets the out-of-band transmission zero point design standard; the first dielectric substrate layer (3) and the second metal layer (4) are bonded with a prepreg, and the bandwidth and loss requirements are met by reducing the side length of the metal patch on the same side.

[0034] A three-layer metal two-dimensional periodic arrangement structure and two dielectric substrate layers between adjacent metal layers: the first metal layer (2) and the third metal layer (6) are square metal patch arrays arranged periodically with a certain spacing; the middle second metal layer (4) is composed of a metal frame and a central rotationally symmetrical miniaturized structure at the center; and two completely identical dielectric substrate layers are embedded between the three metal layers.

[0035] The capacitive coupling of the gap between the patch structures of the first metal layer (2) and the third metal layer (6) can further adjust the transmission bandwidth by controlling the transmission pole in the passband. The first dielectric substrate layer (3) and the second dielectric substrate layer (5) can adjust the position of the transmission zero point by changing their characteristic parameters such as thickness and dielectric constant. The outer metal frame of the second metal layer (4) can control the inductive part of the frequency selective surface, and the central rotationally symmetrical structure controls the out-of-band suppression through the inductive coupling introduced by the metal strips and the capacitive coupling of the gap between the strips.

[0036] Figure 3 The figure shows the top view of the first and third metal layers of a dual-polarization low insertion loss flat bandpass frequency selective surface for millimeter wave radio telescopes. The top view of the first metal layer (2) and the third metal layer (6) of the frequency selective surface (1) are shown. They are identical arrays of square metal patches. The metal patches are strictly arranged in a two-dimensional periodic manner along the horizontal plane. By controlling the distance between the patches, open-slot capacitive coupling can be achieved, thereby affecting the passband characteristics of the frequency selective surface.

[0037] Figure 4 The figure shows a top view of the second metal layer (4) of a dual-polarization low insertion loss flat bandpass frequency selective surface for a millimeter wave radio telescope, wherein the outer metal frame mainly controls the transmission bandwidth in the low frequency passband, and the inner central rotationally symmetric pattern controls the suppression degree in the high frequency stopband. The figure shows a top view of the second metal layer (4) of the frequency selective surface (1). The second metal layer (4) is composed of a metal frame (9) and a central rotationally symmetric metal strip (10). The metal frame (9) mainly controls the transmission bandwidth in the low frequency passband, while the inner central rotationally symmetric pattern (10) controls the suppression degree in the high frequency stopband. By adjusting the size of the metal frame (9) and the shape of the rotationally symmetric metal strip (10), the inductive part and the transmission zero point in the passband can be precisely controlled, thereby optimizing the frequency selection performance in specific practical applications.

[0038] Figure 5 The figure shows the transmission coefficient amplitude curve of the dual-polarization low insertion loss flat bandpass frequency selective surface for millimeter-wave radio telescopes. The curve shows the transmission performance of the filter within the passband range. The passband center frequency is set at 22.7GHz, and the 1dB fractional bandwidth reaches 49.9% (17.03-28.37GHz), which means that within this frequency range, the signal size is only reduced by 1dB. It can be seen that the insertion loss of this filter is very small, less than 0.1dB. At the same time, this also shows that this filter can meet the dual-polarization low loss characteristics, that is, when the maximum incident angle is 45°, the performance of the filter can still be maintained well.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A dual-polarization low insertion loss flat bandpass frequency selective surface for radio telescopes, characterized by: The bandpass frequency selective surface comprises: A first metal layer (2), a second metal layer (4), a third metal layer (6), and a first dielectric substrate layer (3) and a second dielectric substrate layer (5) between every two adjacent metal layers; The first metal layer (2) and the third metal layer (6) are both composed of array square patches (7) and metal wire grids (8); The first metal layer (2), the first dielectric substrate layer (3), the second metal layer (4), the second dielectric substrate layer (5) and the third metal layer (6) are sequentially stacked and combined together to form a multi-layer bandpass frequency selective surface structure; The array square patches of the first metal layer (2) and the third metal layer (6) are arranged in a two-dimensional periodic manner along a horizontal plane; The second metal layer (4) is composed of a plurality of metal frames (9) and a central rotationally symmetrical metal strip (10) located within the metal frames; The third metal layer (6) is completely identical to the first metal layer (2), the second dielectric substrate layer (5) is completely identical to the first dielectric substrate layer (3), and the third metal layer (6), the second dielectric substrate layer (5) and the first metal layer (2), the first dielectric substrate layer (3) are distributed in a mirror-symmetrical manner; The array square patch (7) has a capacitive coupling characteristic, and the metal wire grid (8) has an inductive coupling characteristic; The metal frame (9) and the central rotationally symmetrical metal strip (10) respectively control the inductive part and the transmission zero point in the passband of the frequency selective surface; The central rotationally symmetrical metal strip (10) adopts a miniaturized curved structure, which not only meets the processing accuracy requirements but also reaches the design standard of the zero point of out-of-band transmission; The first dielectric substrate layer (3) and the second metal layer (4) are bonded together using a prepreg.

Images