CN116706561A - Wide-angle, high-selectivity and zero-point-controllable frequency selection structure - Google Patents

Abstract

The application discloses a wide-angle, high-selectivity and zero-point-controllable frequency selective structure, wherein each frequency selective surface structure unit of the structure comprises a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a third metal layer which are sequentially bonded from top to bottom; the first metal layer, the second metal layer and the third metal layer are identical in structure size. The first metal layer comprises a first square patch, a first bending gap square ring and a second bending gap square ring are etched on the first square patch, and the two bending gap square rings are nested but not overlapped; the second metal layer comprises a second square patch, and a third bending gap square ring is etched on the second square patch; the third metal layer comprises a third square patch, a fourth bending gap square ring and a fifth bending gap square ring are etched on the third square patch, and the two bending gap square rings are nested but not overlapped. The frequency selection structure provided by the application has the advantages of wide passband, controllable zero point, insensitive polarization, high selectivity, stable oblique incidence performance and the like, and is very suitable for a modern wireless communication system.

Description

Frequency selection structure with wide angle, high selectivity and controllable zero point

technical field

The invention belongs to the field of electromagnetic field and microwave technology, in particular to a frequency selection structure with wide angle, high selectivity and controllable zero point and a design method thereof.

Background technique

Frequency selective structure (FSS, Frequencyselectivestructure) is an artificial electromagnetic structure array composed of identical units arranged in a periodic manner. It has different selectivity for space electromagnetic waves with different operating frequencies, polarization states and incident angles, so it can be regarded as a filter for space electromagnetic waves. FSS has been widely used in radome, antenna reflector, polarizer and other fields.

When externally loading an FSS radome onto a phased array antenna with scanning characteristics, it becomes critical to maintain stable filtering characteristics over a wide range of incidence angles. In addition, the high selectivity makes the wave energy output inside and outside the passband very different, which can effectively improve the communication quality and anti-interference ability of the wireless communication system, and ensure the efficient operation of the electromagnetic system.

One proposed in the document "Miniaturized-ElementBandpassFSSbyLoadingCapacitiveStructures," (P.C.Zhao, Z.Y.Zong, W.Wu, B.LiandD.G.Fang, IEEETrans.AntennasPropag., vol.67, no.5, pp.3539-3544, May2019) A convoluted frequency-selective surface can provide a cell size as small as 4.84% of the free-space wavelength at the resonant frequency, and achieve stable performance at an incident angle up to 60°. The structure has good angular stability, but its passband is two Slow side roll-off and poor out-of-band suppression.

The literature "Design and Analysis of a High-Selectivity Frequency-Selective Surface at 60GHz," (D.S.Wang, P.ZhaoandC.H.Chan, IEEETrans.Microw.TheoryTech., vol.64, no.6, pp.1694-1703, June2016) utilizes an aperture-coupled resonator ( ApertureCoupledResonators, ACRs) realized a highly selective frequency selective surface at 60 GHz, and proposed a new ACR FSS structure based on main electrical coupling. The constructed in-phase signal path generates two transmission zeros near the edge of the narrow passband, thereby The selectivity is greatly improved, and the structure has a remarkable effect in improving the selectivity, but the relatively narrow bandwidth and poor angular stability.

Contents of the invention

The object of the present invention is to solve the above-mentioned problems in the prior art, and provide a novel FSS with controllable zero point, which can realize high selectivity performance in a wide range of incident angles.

The technical solution to realize the object of the present invention is as follows: on the one hand, a frequency selective structure with wide angle, high selectivity and controllable zero point is provided, the frequency selective structure includes several frequency selective surface structure units forming a periodic array, Each of the frequency selective surface structure units includes a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer, and a third metal layer that are sequentially bonded from top to bottom; the first metal layer, The second metal layer and the third metal layer have the same structure size;

The first metal layer includes a first square patch, on which a first square ring with a bent slit and a second square ring with a bent slit are etched, and the two square rings with a bent slit overlap but do not overlap;

The second metal layer includes a second square patch on which a third bent slit square ring is etched;

The third metal layer includes a third square patch on which a fourth square ring with a bent slit and a square ring with a fifth bent slit are etched, and the two square rings with a bent slit overlap but do not overlap;

The structure of all the above-mentioned square rings with bent slits is as follows: each side of the square slit ring is provided with an inward rectangular groove;

The second bent slot square ring, the third bent slot square ring and the fourth bent slot square ring are used to generate three transmission poles; the first bent slot square ring and the fifth bent slot square ring Used to introduce two transmission zeros.

Further, the length and width of each bent slit square ring can be adjusted to adjust the filtering characteristics of the frequency selective surface.

Further, the calculation method of the loop length of each bending gap square ring is:

Calculate the wavelength λ corresponding to the frequency of the resonant point of the bent slit square ring according to the resonant frequency calculation formula of the slit-type frequency-selective surface:

λ=c/f

Among them, c is the propagation speed of light in vacuum, and f is the resonance point frequency;

Let λ be the loop length of the bent slit square ring, and determine the side lengths of the bent slit square ring according to the loop length.

Further, the positions of the second bent slit square ring, the third bent slit square ring, and the fourth bent slit square ring are corresponding, and the structural dimensions of the three are similar, and the size difference is within a preset threshold range .

Further, the sizes of the first square ring of bending gap and the square ring of fifth bending gap can be adjusted, thereby realizing the adjustable position, which can be located in the square ring of second bending gap and the square ring of fourth bending gap respectively. The inner or outer side of the square ring is used to adjust the positions of the two transmission zeros; when the first bent square ring is located on the outer side and the fifth bent square ring is located on the inner side, the two transmission zeros are respectively located on both sides of the passband; When the square ring of the first bending gap and the square ring of the fifth bending gap are located inside or outside, the two transmission zero points are located on the same side of the passband.

Further, the first dielectric layer and the second dielectric layer both use Rogers5880 substrates.

Further, each metal layer is bonded with prepreg Rogers4450F.

On the other hand, a method for designing a frequency selection structure with wide angle, high selectivity and controllable zero point is provided, including the following steps:

1) Design the third-order band-pass Chebyshev response structure, select the dielectric plate material of the dielectric layer, and deduce the frequency selective surface structure unit period and the second bending gap square ring, The loop length of the third bending gap square ring and the fourth bending gap square ring, and determine the length of each side thereof;

2) Design the low-frequency stopband structure, deduce the loop length of the first bent slit square ring according to the resonant frequency calculation formula of the slit-type frequency-selective surface, and determine the length of each side;

3) Design the high-frequency stopband structure, deduce the loop length of the fifth bent square ring of the slot according to the resonant frequency calculation formula of the slot-type frequency selection surface, and determine the length of each side;

4) Fine-tuning the filtering characteristics of the frequency selective surface by adjusting the length and width of each bent slit square ring.

Compared with the prior art, the present invention has the remarkable advantages of:

(1) The present invention has high selectivity, uses a three-layer metal structure to introduce a transmission zero on both sides of the passband, realizes the bilateral steep drop on both sides of the passband, and reduces the transition band between the passband and the stopband.

(2) The present invention has the advantage of flexible control of the zero point, the positions of the two introduced zero points can be on both sides or on the same side, and the frequency of the zero point can be independently controlled without affecting the passband.

(3) The present invention has large angle stability, and still has good transmission response under different polarizations and 60° oblique incidence conditions.

The present invention will be described in further detail below in conjunction with the accompanying drawings.

Description of drawings

Figure 1 is a perspective view of a frequency selective structure in one embodiment.

Fig. 2 is a specific structural side view of the frequency selection structure in an embodiment.

FIG. 3 is a top view of the unit structure of the first metal layer of the frequency selective structure in one embodiment.

FIG. 4 is a top view of the unit structure of the second metal layer of the frequency selective structure in one embodiment.

FIG. 5 is a top view of the unit structure of the third metal layer of the frequency selective structure in one embodiment.

Fig. 6 is a diagram of three kinds of S-parameter simulation results that can be realized by the frequency selection structure in one embodiment.

Fig. 7 is a diagram of S-parameter simulation results of Type 1 in the frequency selection structure in an embodiment.

Fig. 8 is a graph showing the transmission coefficient of Type 1 as a function of parameter d3 in a frequency selective structure in one embodiment.

Fig. 9 is a graph showing the transmission coefficient of Type 1 as a function of parameter d5 in a frequency selective structure in one embodiment.

Fig. 10 is a graph showing transmission coefficients of Type 1 of the frequency selective structure under different incident angles of TE polarized incident waves in one embodiment.

Fig. 11 is a graph showing transmission coefficients of Type 1 of the frequency selective structure under different incident angles under TM polarized incident waves in one embodiment.

Detailed ways

In order to make the purpose, technical solution and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present application, and are not intended to limit the present application.

It should be noted that if there is a directional indication (such as up, down, left, right, front, back...) in the embodiment of the present invention, the directional indication is only used to explain the position in a certain posture (as shown in the accompanying drawing). If the specific posture changes, the directional indication will also change accordingly.

In addition, if there are descriptions involving "first", "second" and so on in the embodiments of the present invention, the descriptions of "first", "second" and so on are only for descriptive purposes, and should not be interpreted as indicating or implying Its relative importance or implicitly indicates the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In addition, the technical solutions of the various embodiments can be combined with each other, but it must be based on the realization of those skilled in the art. When the combination of technical solutions is contradictory or cannot be realized, it should be considered that the combination of technical solutions does not exist , nor within the scope of protection required by the present invention.

In one embodiment, with reference to Fig. 1 and Fig. 2, a frequency selective structure with wide angle, high selectivity and controllable zero point is provided, the frequency selective structure includes several frequency selective surface structure units forming a periodic array, Each frequency selective surface structure unit includes a first metal layer 6, a first dielectric layer 9, a second metal layer 7, a second dielectric layer 10, and a third metal layer 8 bonded in sequence from top to bottom; The first metal layer 6, the second metal layer 7 and the third metal layer 8 have the same structure and size;

The first metal layer 6 includes a first square patch, on which the first square ring 1 with a bent slit and the second square ring 2 with a bent slit are etched, and the two square rings with a bent slit overlap but do not overlap;

The second metal layer 7 includes a second square patch on which a third bent slit square ring 3 is etched;

The third metal layer 8 includes a third square patch, on which the fourth bent slit square ring 4 and the fifth bent slit square ring 5 are etched, and the two bent slit square rings overlap but do not overlap;

The structure of all the above-mentioned square rings with bent slits is as follows: each side of the square slit ring is provided with an inward rectangular groove;

The second bent square ring 2, the third bent square ring 3 and the fourth bent square ring 4 are used to generate three transmission poles; the first bent square ring 1 and the fifth bent The slit square ring 5 is used to introduce two transmission zeros.

Here, the length and width of each bent slit square ring can be adjusted to adjust the filtering characteristics of the frequency selective surface.

Here, the calculation method of the loop length of each bending gap square ring is:

Calculate the wavelength λ corresponding to the frequency of the resonant point of the bent slit square ring according to the resonant frequency calculation formula of the slit-type frequency-selective surface:

λ=c/f

Among them, c is the propagation speed of light in vacuum, and f is the resonance point frequency;

Let λ be the loop length of the bent slit square ring, and determine the side lengths of the bent slit square ring according to the loop length.

The positions of the second bent slit square ring 2 , the third bent slit square ring 3 , and the fourth bent slit square ring 4 correspond to each other, and the structural dimensions of the three are the same or similar, and the size difference is within a preset threshold range .

When the electromagnetic wave is vertically incident, the part of the metal wire parallel to the direction of the electric field is equivalent to an inductance, and the gap between the metal wires with the direction of the electric field perpendicular to it is equivalent to a capacitor. Therefore, the square ring with the bent gap forms a parallel capacitance-inductance circuit. The second bent slit square ring 2, the third bent slit square ring 3 and the fourth bent slit square ring 4 are all modeled as parallel capacitance-inductance resonant circuits, producing three transmission poles; while the first bent slit square ring 1 and the fifth bent-gap square ring 5 are used as suspension resonators, which are directly coupled to the first and last resonators, and the suspension resonators are regarded as stop-band resonators integrated in the band-pass filter, which can additionally introduce two The selectivity of the filter response is greatly improved.

The position of the transmission zero point depends on the resonance lengths of the first square ring 1 with a bent slot and the square ring 5 with a fifth bent slot. As shown in Figure 1, the loop length of the first square ring with bent slot 1 is longer than that of the second square ring with bent slot 2, and its resonant frequency is lower than the operating frequency, so the transmission zero point is located in the passband left side. The loop length of the fifth square ring with bent slot 5 is shorter than that of the fourth square ring with bent slot 4 , and its resonant frequency is higher than the operating frequency, so the transmission zero point is located on the right side of the passband. Name this structural layout Type I (TypeI), and its S parameters are shown in Figure 6. Type II and Type III in the figure correspond to the following two situations respectively: If the first bending gap square ring 1 and the resonant length of the fifth bent slot square ring 5 are shorter, that is, they are respectively located inside the second bent slot square ring 2 and the fourth bent slot square ring 4, then the positions of the two transmission zeros are located in the pass The right side of the belt; if the resonance lengths of the first bending gap square ring 1 and the fifth bending gap square ring 5 are longer, that is, they are respectively located at the second bending gap square ring 2 and the fourth bending gap square ring 4 , then both transmission zeros are located to the left of the passband. (In the present invention, only the corresponding structure of Type 1 is drawn as an example, that is, Fig. 1, and the other two types can be known according to the above description.)

The design method of the frequency selection structure of the present invention comprises the steps:

1) Design the third-order bandpass Chebyshev response structure, select the dielectric plate material of the dielectric layer, and deduce the structural unit period of the frequency selective surface and the square ring of the second bending gap according to the calculation formula of the resonant frequency of the gap-type frequency-selective surface , the loop lengths of the third bending gap square ring 3 and the fourth bending gap square ring 4, and determine the length of each side thereof;

2) Designing a low-frequency stopband structure, deriving the loop length of the first bent slit square ring 1 according to the resonant frequency calculation formula of the slit-type frequency-selective surface, and determining the lengths of its sides;

3) Designing a high-frequency stopband structure, deriving the loop length of the fifth bent slit square ring 5 according to the resonant frequency calculation formula of the slot-type frequency-selective surface, and determining the lengths of its sides;

4) Fine-tuning the filtering characteristics of the frequency selective surface by adjusting the length and width of each bent slit square ring.

Preferably, the periodic array is a rectangular array.

Preferably, the first dielectric layer 9 and the second dielectric layer 10 adopt Rogers5880 substrate; each metal patch layer adopts prepreg Rogers4450F for bonding.

As a specific example, in one of the embodiments, the present invention is further verified and explained.

Carry out further simulation analysis on Type 1. In this embodiment, the relative permittivity of the first dielectric layer 9 and the second dielectric layer 10 used is 2.2, and the thickness is 2.75 mm. The rectangular grooves provided on each side of the square gap ring are located on the side central location. The dimensional specifications of the frequency selection structure are shown in Figures 3 to 5, and the dimensional parameters are as follows: the side length of the first bent slit square ring 1 is 2*(the length l on one side of the rectangular groove on the side length ₁ = 0.9mm), 2* (the width of the rectangular groove d ₁ = 0.6mm), the length of the rectangular groove w ₁ = 0.6mm five lengths are superimposed, the side length of the second bending gap square ring 2 is 2* (the length l ₂ of one side of the rectangular groove on this side length = 0.9mm), 2*(the width d ₂ of the rectangular groove = 0.5mm), the length w ₂ of the rectangular groove = 0.2m and the five lengths are superimposed, The side length of the third bending slit square ring 3 is composed of 2*(the length l ₃ of one side of the rectangular groove on the side length=1.3mm), 2*(the width d ₃ of the rectangular groove=0.6mm), the rectangular groove The length w ₃ of the groove = 0.2mm. The five lengths are superimposed, and the side length of the fourth bending slit square ring 4 is 2* (the length l ₄ on one side of the rectangular groove on this side length = 1.2mm), 2* (the width d ₄ of the rectangular groove=0.1mm), the length w ₄ of the rectangular groove=0.3mm and the five lengths are superimposed, and the side length of the fifth bending slit square ring 5 is by 2*(the side length is located in the rectangular groove The length of one side of the groove l ₅ =0.7mm), 2*(the width of the rectangular groove d ₅ =0.4mm), the length of the rectangular groove w ₅ =0.55mm and the five lengths are superimposed. The width of each slit is c=0.1 mm.

In this embodiment, modeling and simulation is carried out in the electromagnetic simulation software CST, and its S parameters are shown in Figure 7. It can be seen that the center frequency of the frequency selection structure is 21.3GHz, and the 3dB bandwidth is about 4.5GHz (19.1GHz-23.6GHz) , the relative bandwidth is 21%. In addition, it can be clearly observed in the figure that two transmission zeros are at 17.7GHz and 25.4GHz respectively, and the introduction of transmission zeros enhances the steepness outside the passband. Figure 8 and Figure 9 are the transmission coefficient curves of type 1 with parameters d ₃ and d ₅ , respectively. It can be seen from the figure that the transmission zero point can be independently controlled by changing the corresponding physical parameters without affecting the passband.

Fig. 10 and Fig. 11 are the transmission curves of the frequency selective structure of the present invention in the case of 60° oblique incidence under TE and TM polarized incident waves respectively. It can be seen that under the incidence of TE wave, the insertion loss in the passband slightly increases, and the center frequency is almost unchanged; under the incidence of TM wave, the characteristics of the passband and stopband remain basically stable. Therefore, the frequency selective structure of the present invention has good angular stability and polarization stability.

In summary, the frequency selection structure proposed by the present invention has the advantages of wide passband, controllable zero point, polarization insensitivity, high selectivity, and stable oblique incidence performance, and is very suitable for modern wireless communication systems.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. The above-mentioned embodiments and descriptions only illustrate the principles of the present invention. Within the spirit and principles, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

Claims (9)

1. A wide-angle, high-selectivity and zero-controllable frequency selective structure, characterized in that the frequency selective structure comprises a plurality of frequency selective surface structural units forming a periodic array, and each frequency selective surface structural unit comprises a first metal layer (6), a first dielectric layer (9), a second metal layer (7), a second dielectric layer (10) and a third metal layer (8) which are sequentially bonded from top to bottom; the first metal layer (6), the second metal layer (7) and the third metal layer (8) are identical in structural size;

the first metal layer (6) comprises a first square patch, a first bending gap square ring (1) and a second bending gap square ring (2) are etched on the first square patch, and the two bending gap square rings are nested but not overlapped;

the second metal layer (7) comprises a second square patch, and a third bending gap square ring (3) is etched on the second square patch;

the third metal layer (8) comprises a third square patch, a fourth bending gap square ring (4) and a fifth bending gap square ring (5) are etched on the third square patch, and the two bending gap square rings are nested but not overlapped;

the structure of all the bending gap square rings is as follows: each side of the square slit ring is provided with an inward rectangular groove;

the second bending slit square ring (2), the third bending slit square ring (3) and the fourth bending slit square ring (4) are used for generating three transmission poles; the first bending slit square ring (1) and the fifth bending slit square ring (5) are used for introducing two transmission zero points.

2. The wide angle, high selectivity, zero controllable frequency selective structure of claim 1, wherein each of the meander slit square rings is adjustable in length and width for adjusting the filter characteristics of the frequency selective surface.

3. The wide angle, high selectivity, zero controllable frequency selective structure of claim 1, wherein the loop length of each folded slit square ring is calculated by:

calculating the wavelength lambda corresponding to the resonance point frequency of the bent slit square ring according to a resonance frequency calculation formula of the slit type frequency selection surface:

λ＝c/f

wherein c is the propagation speed of light in vacuum, and f is the resonant point frequency;

let lambda be the loop length of the bending gap square ring, determine each side length of the bending gap square ring according to the loop length.

4. The wide-angle, high-selectivity and zero-point-controllable frequency selective structure according to claim 1, wherein the positions of the second bending slit square ring (2), the third bending slit square ring (3) and the fourth bending slit square ring (4) are corresponding, the structural sizes of the three are similar, and the size difference is within a preset threshold range.

5. The wide-angle, high-selectivity and zero-point-controllable frequency selection structure according to claim 2, wherein the dimensions of the first bending slit square ring (1) and the fifth bending slit square ring (5) are adjustable, so that the positions are adjustable, and the first bending slit square ring and the fifth bending slit square ring can be respectively positioned at the inner side or the outer side of the second bending slit square ring (2) and the fourth bending slit square ring (4) and used for adjusting the positions of two transmission zero points; when the first bending slit square ring (1) is positioned at the outer side and the fifth bending slit square ring (5) is positioned at the inner side, two transmission zero points are respectively positioned at two sides of the passband; when the first bending slit square ring (1) and the fifth bending slit square ring (5) are both positioned at the inner side or the outer side, two transmission zero points are positioned at the same side of the passband.

6. The wide-angle, high-selectivity, zero-controllable frequency selective structure according to claim 1, characterized in that the first dielectric layer (9) and the second dielectric layer (10) are both Rogers5880 substrates.

7. The wide angle, high selectivity, zero controllable frequency selective structure of claim 1, wherein each metal layer is bonded using prepreg Rogers 4450F.

8. The wide angle, high selectivity, zero controllable frequency selective structure of claim 1, wherein the periodic array is a rectangular array.

9. The wide angle, high selectivity, zero controllable frequency selective structure according to claim 1, characterized in that the relative dielectric constant of the first dielectric layer (9), the second dielectric layer (10) is 2.2 and the thickness is 2.75mm.