Dual-polarization ultra-wideband frequency selective surface structure based on coupling slot line

Abstract

The invention discloses a dual-polarization ultra-wideband frequency selective surface structure based on a coupling slot line, which comprises a mixed structure of a longitudinal coupling slot line and a two-dimensional periodic structure, the longitudinal coupling slot line sequentially comprises a first conductor structure, a first dielectric substrate, a second conductor structure, a second dielectric substrate, a third conductor structure, a third dielectric substrate, a fourth conductor structure, a fourth dielectric substrate, a fifth conductor structure, a fifth dielectric substrate, a sixth conductor structure, a sixth dielectric substrate, a ninth conductor structure and a tenth conductor structure from outside to inside; the two-dimensional periodic structure comprises a seventh conductor structure, a seventh dielectric substrate, an eighth conductor structure and an eighth dielectric substrate. Aiming at the difficulty that the broadband expansion of the current two-dimensional multilayer structure is limited, a method of combining a coupling slot line structure and a two-dimensional periodic structure is adopted, the wave transmission effect of the dual-polarization ultra-wideband is realized, and meanwhile, the structure also has the advantages of out-of-band steep drop and angle stability.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic waves, and in particular relates to a dual-polarization ultra-wideband frequency selective surface structure based on coupled slot lines. Background Art

[0002] The frequency selective surface (FSS) is composed of two-dimensional periodically arranged array units. It is essentially a spatial filter that can show filtering characteristics for electromagnetic waves of different frequencies and incident angles in space. It has been widely used in the fields of hybrid radar covers, absorbing materials, antenna sub-reflectors, electromagnetic shielding, etc. With the development of radar technology, ultra-wideband antennas are widely used in radar systems, and the ultra-wideband wave transmission characteristics of frequency selective surfaces have therefore become a key research object.

[0003] For traditional frequency selective surface array units, an effective way to expand bandwidth is to use a multi-layer structure to increase the filtering order of the frequency selective surface to achieve a high-order broadband filtering effect. However, the current method of increasing the number of layers of the frequency selective surface to achieve broadband wave transmission has limited expansion of bandwidth performance, and there are many problems such as large passband insertion loss, polarization sensitivity, and drastic bandwidth changes when the electromagnetic wave is obliquely incident. Therefore, how to effectively expand the bandwidth while maintaining good selection characteristics, angle stability, and polarization insensitivity is an urgent problem to be solved. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a dual-polarization ultra-wideband frequency selective surface structure based on a coupled slot line, including a hybrid structure of a longitudinal coupled slot line and a two-dimensional periodic structure, wherein the longitudinal coupled slot line includes, from outside to inside, a first conductor structure, a first dielectric substrate, a second conductor structure, a second dielectric substrate, a third conductor structure, a third dielectric substrate, a fourth conductor structure, a fourth dielectric substrate, a fifth conductor structure, a fifth dielectric substrate, a sixth conductor structure, a sixth dielectric substrate, a ninth conductor structure, and a tenth conductor structure, and the two-dimensional periodic structure includes a seventh conductor structure, a seventh dielectric substrate, an eighth conductor structure, and an eighth dielectric substrate. Aiming at the difficulty of the limited broadband expansion of the current two-dimensional multilayer structure, the present invention adopts a method of combining a coupled slot line structure and a two-dimensional periodic structure to achieve the wave transmission effect of the dual-polarization ultra-wideband, and the structure also has the advantages of steep drop out of the band and stable angle.

[0005] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0006] A dual-polarization ultra-wideband frequency selective surface structure based on a coupled slot line, comprising a first conductor structure, a second conductor structure, a third conductor structure and a fourth conductor structure constituting the slot line, and a first dielectric substrate, a second dielectric substrate, a third dielectric substrate and a fourth dielectric substrate respectively corresponding to the four conductor structures, a fifth conductor structure and a sixth conductor structure constituting the two-end slot line and the coupling slot line between the two-end slot lines and their corresponding fifth dielectric substrate and sixth dielectric substrate in sequence, a seventh conductor structure and an eighth conductor structure constituting the frequency selective surface and their corresponding seventh dielectric substrate and eighth dielectric substrate, and a ninth conductor structure and a tenth conductor structure on the back of the fifth conductor structure and the sixth conductor structure;

[0007] The first conductor structure to the fourth conductor structure are two slot lines with different slot widths printed on the corresponding dielectric substrate, wherein the first conductor structure and the second conductor structure have the same slot width, and the third conductor structure and the fourth conductor structure have the same slot width; the first conductor structure can be rotated 180° to become the third conductor structure;

[0008] The fifth conductor structure and the sixth conductor structure are composed of slot line structures located at two ends and coupling slot lines between the two end slot lines, wherein the slot lines at the two ends have the same properties as the slot lines of the first to fourth conductor structures; the fifth conductor structure is the same as the sixth conductor structure;

[0009] The seventh conductor structure and the eighth conductor structure are metal square rings printed on the corresponding dielectric substrates. The seventh conductor structure and the eighth conductor structure are the same and are printed on the outer side surfaces of the seventh dielectric substrate and the eighth dielectric substrate, respectively.

[0010] The ninth conductor structure and the tenth conductor structure are rectangular metal sheets printed on the back of the fifth dielectric substrate and the sixth dielectric substrate respectively, and the ninth conductor structure and the tenth conductor structure are the same.

[0011] Preferably, the first dielectric substrate to the sixth dielectric substrate are all made of Roger AD 320A dielectric plates with a thickness of 0.6 mm, a dielectric constant of 3.2, and a loss tangent of 0.003.

[0012] Preferably, the seventh dielectric substrate and the eighth dielectric substrate are both made of Roger AD 320A dielectric plates with a thickness of 0.5 mm, a dielectric constant of 3.2, and a loss tangent of 0.003.

[0013] The beneficial effects of the present invention are as follows:

[0014] (1) The present invention achieves TE and TM dual-polarization broadband filtering effects by using a hybrid structure of a two-dimensional periodic structure and longitudinally coupled slot lines, and the passband bandwidth reaches an ultra-wideband of 128% (90% wave transmittance).

[0015] (2) The present invention realizes good transmission characteristics of TE and TM dual-polarized electromagnetic waves in the oblique incident angle range of 0-55°. A 90% transmittance can be achieved within an incident angle of 45°, and an 80% transmittance can be achieved at an incident angle of 55°.

[0016] (3) The present invention realizes good out-of-band steepness of dual-polarized electromagnetic waves in the oblique incident angle range of 0-55°, with a low-frequency cutoff transition band of 0.52 GHz and a high-frequency cutoff transition band of 0.35 GHz. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The first figure is a structure of an ultra-wideband wave-transmitting frequency selective surface unit provided by the present invention;

[0018] Figure 2 The second figure is a structure of an ultra-wideband wave-transmitting frequency selective surface unit provided by the present invention;

[0019] Figure 3 An equivalent circuit diagram of an ultra-wideband wave-transmitting frequency selective surface provided by the present invention;

[0020] Figure 4 A schematic diagram of an upper first conductor structure and a lower first dielectric substrate provided by the present invention, and also a schematic diagram of an upper second conductor structure and a lower second dielectric substrate;

[0021] Figure 5 A schematic diagram of an upper third conductor structure and a lower third dielectric substrate provided by the present invention, and also a schematic diagram of an upper fourth conductor structure and a lower fourth dielectric substrate;

[0022] Figure 6 A schematic diagram of the fifth conductor structure of the upper layer and the fifth dielectric substrate of the lower layer provided by the present invention, and also a schematic diagram of the sixth conductor structure of the upper layer and the sixth dielectric substrate of the lower layer;

[0023] Figure 7 A schematic diagram of the seventh conductor structure of the upper layer and the seventh dielectric substrate of the lower layer provided by the present invention, and also a schematic diagram of the eighth conductor structure of the upper layer and the eighth dielectric substrate of the lower layer;

[0024] Figure 8 A schematic diagram of the ninth conductor structure of the upper layer and the fifth dielectric substrate of the lower layer provided by the present invention, and also a schematic diagram of the tenth conductor structure of the upper layer and the sixth dielectric substrate of the lower layer;

[0025] Fig. 9 A schematic diagram of the current continuity processing of the coupled slot line portion during actual processing is provided for the present invention;

[0026] Fig.10The wave transmission coefficient diagram of the ultra-wideband frequency selective surface at different angles under TE polarization simulated by the present invention;

[0027] Fig.11 Figure 3 is a diagram of the wave transmission coefficient of the ultra-wideband frequency selective surface at different angles under TM polarization simulated by the present invention.

[0028] Description of the drawings: 1-first dielectric substrate, 2-first conductor structure, 3-second dielectric substrate, 4-second conductor structure, 5-third dielectric substrate, 6-third conductor structure, 7-fourth dielectric substrate, 8-fourth conductor structure, 9-fifth dielectric substrate, 10-fifth conductor structure, 11-sixth dielectric substrate, 12-sixth conductor structure, 13-seventh dielectric substrate, 14-seventh conductor structure, 15-eighth dielectric substrate, 16-eighth conductor structure, 17-ninth conductor structure, 18-tenth conductor structure. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0030] In view of the problems of limited passband bandwidth, polarization sensitivity and angular instability of the existing FSS structure, a new FSS structure is explored to obtain ultra-wideband wave transmission while taking into account the out-of-band steep drop characteristics, angular stability, and polarization insensitivity characteristics. Therefore, the present invention proposes an ultra-wideband wave-transmitting frequency selective surface with a coupling slot line hybrid. The structure achieves an ultra-wideband filtering effect of 128% relative bandwidth under the condition of dual-polarized electromagnetic wave incidence through the combination of longitudinal coupling slot lines and two-dimensional periodic structures, and at the same time has an angular stability within 55° and an out-of-band steep cutoff characteristic, which is better than the performance of the existing FSS structure.

[0031] The present invention provides an ultra-wideband wave-transmitting frequency selective surface unit structure based on a coupled slot line, comprising: a first conductor structure, a second conductor structure, a third conductor structure and a fourth conductor structure constituting the slot line and a first dielectric substrate, a second dielectric substrate, a third dielectric substrate and a fourth dielectric substrate corresponding thereto respectively; a fifth conductor structure and a sixth conductor structure constituting the coupled slot line and a fifth dielectric substrate and a sixth dielectric substrate corresponding thereto in sequence; a seventh conductor structure and an eighth conductor structure constituting a traditional frequency selective surface and a seventh dielectric substrate and an eighth dielectric substrate corresponding thereto; and a ninth conductor structure and a tenth conductor structure on the back of the fifth conductor structure and the sixth conductor structure.

[0032] The first conductor structure to the fourth conductor structure are two groove lines with different groove widths printed on the corresponding dielectric substrate. The first conductor structure is the same as the second conductor structure, the third conductor structure is the same as the fourth conductor structure, and the first conductor structure can be turned into the third conductor structure by rotating 180°.

[0033] The fifth conductor structure and the sixth conductor structure are composed of slot line structures located at two ends and coupling slot lines between the slot lines at the two ends. The fifth conductor structure and the sixth conductor structure are the same.

[0034] The seventh conductor structure and the eighth conductor structure are metal square rings printed on corresponding dielectric substrates. The seventh conductor structure and the eighth conductor structure are the same and are printed on the outer side surfaces of the seventh dielectric substrate and the eighth dielectric substrate, respectively.

[0035] The ninth conductor structure and the tenth conductor structure are rectangular metal sheets printed on the back of the fifth dielectric substrate and the sixth dielectric substrate respectively, and the ninth conductor structure and the tenth conductor structure are the same.

[0036] In one embodiment of the present invention, the first dielectric substrate to the sixth dielectric substrate all use Roger AD 320A dielectric plates with a thickness of 0.6 mm, a dielectric constant of 3.2, and a loss tangent of 0.003.

[0037] In one embodiment of the present invention, the seventh dielectric substrate and the eighth dielectric substrate are Roger AD 320A dielectric plates with a thickness of 0.5 mm, a dielectric constant of 3.2, and a loss tangent of 0.003.

[0038] Example:

[0039] See also Figure 1 and Figure 2 , Figure 1 An ultra-wideband wave-transmitting frequency-selective surface unit structure provided by an embodiment of the present invention Figure 1 , Figure 2 An ultra-wideband wave-transmitting frequency-selective surface unit structure provided by an embodiment of the present invention Figure 2 An embodiment of the present invention provides an ultra-wideband wave-transmitting frequency selective surface unit structure, including: a first conductor structure, a second conductor structure, a third conductor structure, a fourth conductor structure, a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, a fourth dielectric substrate, a fifth conductor structure, a sixth conductor structure, a fifth dielectric substrate, a sixth dielectric substrate, a ninth conductor structure, a tenth conductor structure, a seventh conductor structure, an eighth conductor structure, a seventh dielectric substrate, and an eighth dielectric substrate constituting a traditional frequency selective surface, constituting a slot line structure.

[0040] See also Figure 1 and Figure 2 The first dielectric substrate, the second dielectric substrate to the sixth dielectric substrate all use Roger AD 320A dielectric plates with a thickness of 0.6 mm, the seventh dielectric substrate and the eighth dielectric substrate use Roger AD320A dielectric plates with a thickness of 0.5 mm, and the relative dielectric constant of all dielectric substrates is 3.2 and the loss tangent is 0.003.

[0041] See also Figure 3 , Figure 3 An equivalent circuit diagram of an ultra-wideband frequency selective surface structure provided by an embodiment of the present invention. Among them, the first conductor structure and the first dielectric substrate can be equivalent to two transmission lines with characteristic impedances of Z1 and Z2, and electrical lengths of Θ1 and Θ2, respectively. In another polarization direction, the second conductor structure and the second dielectric substrate are also equivalent to this structure. Since the third conductor structure and the third dielectric substrate are symmetrical with the first conductor structure and the first dielectric substrate, the third conductor structure and the third dielectric substrate can also be equivalent to two transmission lines with characteristic impedances of Z1 and Z2, and electrical lengths of Θ1 and Θ2, respectively. In another polarization direction, the fourth conductor structure and the fourth dielectric substrate can also be equivalent to this structure. The fifth conductor structure, the ninth conductor structure and the fifth dielectric substrate can be regarded as the structure of a transmission line, a coupled slot line and a transmission line, respectively. Among them, the transmission line has symmetry, and the characteristic impedance of the equivalent transmission line is Z3, and the electrical length is Θ3. The coupled slot line can be equivalent to a coupled transmission line with a short-circuited terminal. The coupled transmission line can be characterized by an even-mode impedance (Z e ) and odd-mode impedance (Z o ) is a series circuit as shown in box 1. In another polarization direction, the sixth conductor structure, the tenth conductor structure and the sixth dielectric substrate can also be equivalent to this structure. Characteristic impedance Z e , Z o The electrical length θ4 can be extracted from the Y matrix of the coupled slot line. When the electrical length of the coupled slot line is 90°, calculate Y 11 =0 frequency (denoted as f0). At f0, calculate Y 12 , and its value is recorded as y. At the frequency of 0.5f0, calculate Y 11 , whose value is x. The characteristic impedance of the coupled slot line is Z e , Z o It can be obtained by the following formula.

[0042]

[0043] The coupled slot line can be further simplified into a π-type circuit in box 2. t is the characteristic impedance of the equivalent parallel grounded transmission line, with an electrical length of Θ4; Z s is the characteristic impedance of the equivalent series transmission line, and the electrical length is Θ4. The characteristic impedance Z of the π-type circuit s , Z t , and Z e , Z o The following relations are satisfied:

[0044]

[0045] Zt =Z e (4) It can be seen from the simplified equivalent circuit that the structure has high-order wave transmission characteristics, so it can greatly expand the bandwidth.

[0046] See also Figure 4 , Figure 4 A schematic diagram of an upper first conductor structure and a lower first dielectric substrate provided by an embodiment of the present invention, wherein a portion of the figure shows two slot lines with two slot widths. Figure 4 It also shows a schematic diagram of an upper second conductor structure and a lower second dielectric substrate provided by an embodiment, Figure 4 The relevant parameters are: p=6mm; w1=2.9mm; w2=2.4mm; h1=8mm; h2=4mm; s1=1.5mm.

[0047] See also Figure 5 , Figure 5 A schematic diagram of an upper third conductor structure and a lower third dielectric substrate provided by an embodiment of the present invention, wherein a portion of the figure shows two slot lines with two slot widths. Figure 5 It also shows a schematic diagram of an upper fourth conductor structure and a lower fourth dielectric substrate provided by the embodiment, Figure 5 The relevant parameters are: p=6mm; w3=2.9mm; w4=2.4mm; h3=8mm; h4=4mm; s2=1.5mm.

[0048] See also Figure 6 , Figure 6 A schematic diagram of an upper fifth conductor structure and a lower fifth dielectric substrate provided by an embodiment of the present invention, wherein a portion of the figure is a coupling slot line, which is the main resonant part of the present invention. Figure 6 It also shows a schematic diagram of the upper sixth conductor structure and the lower sixth dielectric substrate provided by the embodiment, Figure 6 The relevant parameters are: p=6mm; w5=1.4mm; w6=0.2mm; w7=0.2mm; h5=3mm; h6=7.6mm; h7=13.4mm; s3=1.5mm.

[0049] See also Figure 7 , Figure 7 A schematic diagram of an upper seventh conductor structure and a lower seventh dielectric substrate provided by an embodiment of the present invention, wherein part of the figure is a dielectric substrate with a printed metal square ring. Figure 7 It also shows a schematic diagram of an upper eighth conductor structure and a lower eighth dielectric substrate provided by the embodiment, Figure 7 The relevant parameters are: p=6mm; l1=4.7mm; l2=1.6mm; s4=0.7mm.

[0050] See also Figure 8 , Figure 8A schematic diagram of an upper ninth conductor structure and a lower fifth dielectric substrate provided by an embodiment of the present invention, wherein a portion of the figure shows two slot lines with two slot widths. Figure 8 It also shows a schematic diagram of the upper tenth conductor structure and the lower sixth dielectric substrate provided by the embodiment, Figure 8 The relevant parameters are: p=6mm; h7=13.4mm; l3=7.8mm; l4=3mm; s5=1.5mm; s6=2.8mm.

[0051] The present invention requires fine adjustment of the structure at the intersection of the structure, that is, the intersection of the first conductor structure, the first dielectric substrate, and the second conductor structure, the second dielectric substrate; the intersection of the third conductor structure, the third dielectric substrate, and the fourth conductor structure, the fourth dielectric substrate; the intersection of the fifth conductor structure, the fifth dielectric substrate, and the sixth conductor structure, the sixth dielectric substrate to ensure the feasibility and assemblability of the structure. The following takes the first conductor and the first dielectric substrate as an example to describe the specific processing method.

[0052] See also Fig. 9 , Fig. 9 The first conductor structure and the first dielectric substrate are processed by slotting one side of the conductor structure and the dielectric substrate to ensure the assemblability of the structure, and drilling the other side to ensure the continuity of the current. The second conductor structure and the second dielectric substrate interlaced with the first conductor structure and the first dielectric substrate need to be slotted and drilled in the opposite direction, and fixed by solder after being assembled with the first conductor structure and the first dielectric substrate, and the solder passes through the drilled holes to achieve the current continuity between adjacent units. Experiments show that this treatment does not affect the original filtering characteristics.

[0053] See also Fig.10 and Fig.11 , Fig.10 It is a wave transmission coefficient diagram of the ultra-wideband frequency selective surface at different incident angles under TE polarization simulated by the present invention, Fig.11 The transmission coefficient diagram of the ultra-wideband frequency selective surface at different angles under TE polarization simulated by the present invention; the embodiment of the present invention realizes six transmission poles in the passband, and the 90% transmission bandwidth realized within the 45° incident angle is 2.26-10.4GHz (relative bandwidth 128%). The 80% transmission bandwidth within the 55° incident angle is 2.32-9.97GHz (relative bandwidth 124%).

Claims

1. A dual-polarization ultra-wideband frequency selective surface structure based on coupled slot lines, characterized in that: A first conductor structure, a second conductor structure, a third conductor structure and a fourth conductor structure constituting a slot line, and a first dielectric substrate, a second dielectric substrate, a third dielectric substrate and a fourth dielectric substrate corresponding to the four conductor structures respectively, a fifth conductor structure and a sixth conductor structure constituting a slot line at both ends and a coupling slot line between the slot lines at both ends and a fifth dielectric substrate and a sixth dielectric substrate corresponding thereto in sequence, a seventh conductor structure and an eighth conductor structure constituting a frequency selective surface and a seventh dielectric substrate and an eighth dielectric substrate corresponding thereto, and a ninth conductor structure and a tenth conductor structure on the back of the fifth conductor structure and the sixth conductor structure; The first conductor structure to the fourth conductor structure are two slot lines with different slot widths printed on the corresponding dielectric substrate, wherein the first conductor structure and the second conductor structure have the same slot width, and the third conductor structure and the fourth conductor structure have the same slot width; the first conductor structure can be rotated 180° to become the third conductor structure; The fifth conductor structure and the sixth conductor structure are composed of slot line structures located at two ends and coupling slot lines between the two end slot lines, wherein the slot lines at the two ends have the same properties as the slot lines of the first to fourth conductor structures; The fifth conductor structure is the same as the sixth conductor structure; The seventh conductor structure and the eighth conductor structure are metal square rings printed on the corresponding dielectric substrates. The seventh conductor structure and the eighth conductor structure are the same and are printed on the outer side surfaces of the seventh dielectric substrate and the eighth dielectric substrate, respectively. The ninth conductor structure and the tenth conductor structure are rectangular metal sheets printed on the back of the fifth dielectric substrate and the sixth dielectric substrate respectively, and the ninth conductor structure and the tenth conductor structure are the same.

2. The dual-polarization ultra-wideband frequency selective surface structure based on coupled slot lines according to claim 1, characterized in that: The first dielectric substrate to the sixth dielectric substrate all adopt Roger AD 320A dielectric plates with a thickness of 0.6 mm, a dielectric constant of 3.2, and a loss tangent of 0.

003.

3. The dual-polarization ultra-wideband frequency selective surface structure based on coupled slot lines according to claim 1, characterized in that: The seventh dielectric substrate and the eighth dielectric substrate are both made of Roger AD 320A dielectric plates with a thickness of 0.5 mm, a dielectric constant of 3.2, and a loss tangent of 0.003.

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