Frequency selective surface

Abstract

Provided is a frequency selective surface comprising a plurality of unit cells arranged periodically, the frequency selective surface comprising: a first closed conductor of which the shape is a meander pattern; a second closed conductor of which one end is disposed opposite one end of the first closed conductor across a gap; an active element which is disposed in the gate between the one end of the first closed conductor and the one end of the second closed conductor with one terminal electrically connected to the one end of the first closed conductor and another terminal electrically connected to the one end of the second closed conductor, and of which the impedance changes depending on the voltage value of an applied control signal; a first control line which is disposed in correspondence with the first closed conductor, has a first conductor line that provides continuity to the other end of the first closed conductor and a second conductor line that electrically connects the first conductor line and the one terminal of the active element, and conveys the control signal to be applied to the active element; and a first filter disposed in the path of the second conductor line in the first control line to block electromagnetic waves of a frequency to be blocked.

Description

Frequency Selective Surface

[0001] The present disclosure relates to a frequency selective surface (FSS) that is dynamically controllable and selectively blocks electromagnetic waves in a specific frequency band.

[0002] Electromagnetic band gap (EBG) structures are known that are provided within a dielectric substrate and have the same function as a frequency selective surface, i.e., the function of blocking noise in a limited frequency range known as a cutoff frequency band. Patent Document 1 proposes an EBG structure that does not become large when set to a low frequency range.

[0003] The EBG structure shown in Patent Document 1 has a so-called mushroom structure that includes two vias connected to an electrode surface and two metal patches connected to the two vias, respectively. In Patent Document 1, in order to maintain the size of the metal patches even when the cutoff frequency is lowered, notches or gaps are provided in the metal patches in this mushroom-structured EBG structure, thereby increasing the effective electrical length.

[0004] JP 2015-061258 A

[0005] On the other hand, there is a technology for controlling the frequency characteristics of a frequency selective surface by applying an external voltage (hereinafter referred to as dynamic control). In a dynamically controllable frequency selective surface, an active element is placed between a unit cell and a conductor in which a current is induced by an incident electromagnetic wave. A control voltage is applied to the active element from the outside via a control line, and the frequency characteristics are changed by changing the conduction state of the current flowing through the active element.

[0006] Even in a dynamically controllable frequency selective surface having such active elements, it is desirable to reduce the size of the unit cell without increasing the control delay for the active elements.

[0007] The present disclosure has been made in consideration of the above points, and aims to provide a dynamically controllable frequency selective surface that allows for miniaturization of unit cells without increasing the delay in control of active elements.

[0008] The frequency selective surface according to the present disclosure is a frequency selective surface comprising a plurality of unit cells arranged periodically, each of the plurality of unit cells comprising: a first closed-circuit conductor having a meander pattern shape; a second closed-circuit conductor having one end opposed to one end of the first closed-circuit conductor across a gap; and a terminal electrically connected to one end of the first closed-circuit conductor and the other terminal electrically connected to one end of the second closed-circuit conductor in the gap between one end of the first closed-circuit conductor and one end of the second closed-circuit conductor. the first control line has a first conductor line arranged corresponding to the first closed-circuit conductor and electrically connected to the other end of the first closed-circuit conductor, and a second conductor line electrically connecting the first conductor line and one terminal of the active element, and transmits a control signal to be applied to the active element; and a first filter arranged on the path of the second conductor line in the first control line and blocking electromagnetic waves of a frequency to be blocked.

[0009] According to the present disclosure, it is possible to prevent delays in control due to control signals while achieving miniaturization for low resonance frequencies.

[0010] 1 is a front view showing a frequency selective surface according to embodiment 1; FIG. 2 is a front view showing a unit cell in the frequency selective surface according to embodiment 1; FIG. 3 is a front view showing a unit cell in the frequency selective surface of comparative example 1; FIG. 4 is a front view showing a unit cell in the frequency selective surface of comparative example 2; FIG. 5 is a front view showing a unit cell in the frequency selective surface of comparative example 3; FIG. 6 is a diagram showing verification results of transmission characteristics for electromagnetic wave frequencies obtained by electromagnetic field analysis; FIG. 7 is a diagram showing verification results of transmission characteristics for electromagnetic wave frequencies obtained by electromagnetic field analysis for different capacitance values ​​of the active element; FIG. 8 is a diagram showing verification results of a unit cell in the frequency selective surface according to embodiment 1, where the distance d between the first conductor line in the first control line and the first conductor line in the second control line is 41.0 mm; FIG. 9 is a diagram showing verification results of a unit cell in the frequency selective surface according to embodiment 1, where the distance d is 38.7 mm; FIG. 10 is a diagram showing verification results of a unit cell in the distance d is 37.2 mm; FIG. 11 is a diagram showing verification results of a unit cell in the distance d is 20.5 mm; and FIG. 12 is a diagram showing verification results of a unit cell in the distance d is 18.2 mm. 1 is a diagram showing verification results of a unit cell when the distance d is 15.9 mm; 2 is a diagram showing verification results of a unit cell when the distance d is 14.4 mm; 3 is a diagram showing verification results obtained by electromagnetic field analysis of the transmission characteristics of electromagnetic waves at frequencies in a frequency selective surface according to embodiment 1; 4 is a front view showing a frequency selective surface according to embodiment 2; and 5 is a diagram showing verification results obtained by electromagnetic field analysis of the transmission characteristics of electromagnetic waves at frequencies in different capacitance values ​​of an active element.

[0011] A frequency selective surface 100 according to a first embodiment will be described with reference to Figures 1 to 15. The frequency selective surface 100 according to the first embodiment is dynamically controllable and selectively blocks electromagnetic waves in a specific dynamically controlled frequency band. The frequency of the electromagnetic waves that is selectively blocked will be referred to as the cutoff frequency hereinafter.

[0012] The frequency selective surface 100 according to the first embodiment is used, for example, in the field of wireless communications, and is configured by periodically arranging unit cells 1, each of which has a resonant frequency equal to the cutoff frequency of electromagnetic waves, on a dielectric substrate 10 in order to effectively prevent interference and information leakage between wireless systems. Note that the unit cells 1 are FSS elements.

[0013] As shown in FIG. 1, the frequency selective surface 100 according to the first embodiment includes, as an example, a unit cell 1 １１ , 1 １２ , 1 ２１ , 1 ２２ 1, two rows in the x direction and two columns in the y direction. The number of unit cells is determined depending on the application, and a plurality of unit cells are arranged two-dimensionally. In short, the frequency selective surface 100 according to the first embodiment is made up of a plurality of unit cells 1 periodically arranged on the surface of the dielectric substrate 10. １１ , 1 １２ , 1 ２１ , 1 ２２ Equipped with.

[0014] Each unit cell 1 １１ , 1 １２ , 1 ２１ , 1 ２２ In the first embodiment, the occupied area arranged on the surface of the dielectric substrate 10 is a rectangular area of ​​48 mm in the x direction (dx) and 48 mm in the y direction (dy) shown in FIG. １１ , 1 １２ , 1 ２１ , 1 ２２ have the same configuration, and therefore, in the following description, in order to avoid complexity, when describing the unit cells, the subscripts attached to the reference numerals will be omitted except when a distinction is required.

[0015] As shown in FIGS. 1 and 2, the unit cell 1 includes a first closed-circuit conductor 11a, a second closed-circuit conductor 11b, an active element 12, and a first conductor line 13a. １ and the second conductor line 13a ２ The first control line 13a and the first conductor line 13b have １ and the second conductor line 13b ２ The second control line 13b has a first filter 14a and a second filter 14b.

[0016] The first closed-circuit conductor 11a and the second closed-circuit conductor 11b are each a conductive layer formed by printing or the like on the surface of the dielectric substrate 10. A current is induced in each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b by the electric field of an electromagnetic wave incident on the frequency selective surface 100.

[0017] The first closed-circuit conductor 11a and the second closed-circuit conductor 11b each have a meander pattern shape, and one end of each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b (the end on the apex side in the shapes shown in Figures 1 and 2) is arranged opposite to each other with a gap between them. The first closed-circuit conductor 11a and the second closed-circuit conductor 11b each have a cutout C in their outer shape relative to their occupied area, and the cutout C lengthens the effective electrical length of each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b, resulting in a meandering meander pattern in which the flow of current induced by the electric field of the incident electromagnetic wave.

[0018] Since the effective electrical length of each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b is long, the frequency of the blocking band for the target electromagnetic waves of each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b can be lowered without expanding the area occupied by each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b for placement.

[0019] The outer shape of the occupied area of ​​each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b is a shape in which multiple notches C are formed inward from each equal side of an isosceles triangle and parallel to the base. The shapes of each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b are symmetrical with respect to a perpendicular line drawn from the apex angle of the isosceles triangle to the base.

[0020] The first closed-circuit conductor 11a and the second closed-circuit conductor 11b are arranged opposite each other across a gap on the surface of the dielectric substrate 10. The first closed-circuit conductor 11a and the second closed-circuit conductor 11b are arranged on the periphery of an isosceles triangle with the apex side at the center and the base parallel to the y-axis. The outer shape of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b has a plurality of rectangular branches parallel to the base that become shorter from the periphery to the center, with a notch C between adjacent branches.

[0021] In the present disclosure, the shape of a conductor in which the flow of current meanders is called a meander pattern, and the first closed-circuit conductor 11a and the second closed-circuit conductor 11b are not limited to shapes in which the flow of current meanders by providing notches in their outer shapes, but may also be meander patterns in which the flow of current meanders by meandering the conductors themselves.

[0022] The active element 12 is disposed on the surface of the dielectric substrate 10 in the gap between the first closed-circuit conductor 11a and the second closed-circuit conductor 11b, which are arranged facing each other. The first closed-circuit conductor 11a and the second closed-circuit conductor 11b are arranged point-symmetrically with respect to the active element 12.

[0023] The active element 12 has two terminals: one terminal is electrically connected to a connection portion at one end of the first closed-circuit conductor 11a, and the other terminal is electrically connected to a connection portion at one end of the second closed-circuit conductor 11b.

[0024] The active element 12 is an element whose impedance changes depending on the voltage applied to it. The active element 12 is a variable capacitance diode (varactor diode). The first closed-circuit conductor 11a and the second closed-circuit conductor 11b, which are connected to two terminals of the active element 12, also function as transmission lines for control signals for applying voltage to the active element 12.

[0025] The meander pattern shapes of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b, that is, the effective electrical length and the impedance of the active element 12, are set as follows: That is, the above settings are set so that when an electromagnetic wave is incident on the frequency selective surface 100, a resonance phenomenon occurs in the first closed-circuit conductor 11a and the second closed-circuit conductor 11b, respectively, due to the electric field of the incident electromagnetic wave, and in the current flowing through the first closed-circuit conductor 11a and the second closed-circuit conductor 11b and the active element 12, with respect to the current due to the electromagnetic wave at a specific frequency, that is, the cutoff frequency.

[0026] The frequency of the electromagnetic wave at which the current resonance phenomenon occurs is called the resonant frequency. In short, the meander pattern shapes of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b and the impedance of the active element 12 are set so that the resonant frequency becomes the cutoff frequency. Since the impedance of the active element 12 can be changed by the voltage value of the applied control signal, the resonant frequency of the first closed-circuit conductor 11a, the second closed-circuit conductor 11b, and the active element 12 can be dynamically changed.

[0027] The first control line 13a and the second control line 13b each transmit a control signal for applying a control voltage to the active element 12. The control signal is a DC signal or a signal having only a cutoff frequency, i.e., a frequency component lower than the resonant frequency. The first control line 13a is disposed corresponding to the first closed-circuit conductor 11a, and the second control line 13b is disposed corresponding to the second closed-circuit conductor 11b.

[0028] First conductor line 13a in first control line 13a １ is formed by a conductor arranged linearly around the periphery of the first closed-circuit conductor 11a, parallel to the y-axis in FIG. １ is arranged to be in contact with or cross the other end of the first closed-circuit conductor 11a, in this example, the linear conductor located at the end on the bottom side, and is electrically connected to the other end of the first closed-circuit conductor 11a.

[0029] First conductor line 13a １ The first conductor line 13a may also serve as a linear conductor located at the other end of the first closed-circuit conductor 11a. １ is the unit cell 1 arranged in the column direction, i.e., the y direction in FIG. １１ and unit cell 1 １２ , and unit cell 1 ２１ and unit cell 1 ２２ 1, and control signals are applied from arrows A1 and A3 shown in FIG.

[0030] Second conductor line 13a in first control line 13a ２ is the first conductor line 13a １and one terminal of the active element 12, and the first conductor line 13a １ The control signal transmitted from the second conductor line 13a is transmitted to one terminal of the active element 12. ２ is the second conductor line 13a ２ By disposing the first filter 14a in the path of the second conductor line 13a, the current induced by the incident electromagnetic wave is ２ Block the flow of water into the area.

[0031] As a result, the effective electrical length is determined by the path passing through the first closed-circuit conductor 11a, which is a meander pattern, and the second conductor line 13a ２ This prevents the resonant frequency from becoming higher due to the addition of the first closed-circuit conductor 11a, and maintains the effect of miniaturization achieved by forming the first closed-circuit conductor 11a into a meander pattern.

[0032] A second conductor line 13a is connected to one terminal of the active element 12. ２ via the first conductor line 13a １ and the second conductor line 13a ２ The electrical length from one terminal of the active element 12 to the connection point of the first closed-circuit conductor 11a to the first conductor line 13a is １ The electrical length is shorter than the electrical length to the point of electrical continuity between the first closed-circuit conductor 11a and the first closed-circuit conductor 11b. Therefore, a delay in the transmission of a control signal for controlling the impedance of the active element 12 to one terminal of the active element 12 can be prevented.

[0033] Second conductor line 13a ２ is formed by conductors arranged in a straight line on a perpendicular line drawn from the apex angle to the base of an isosceles triangle in the occupied area in which the first closed-circuit conductor 11a is arranged, inside the first closed-circuit conductor 11a, in this example, as shown in Figures 1 and 2.

[0034] First conductor line 13b in second control line 13b １ is formed by a conductor arranged linearly around the second closed-circuit conductor 11b, parallel to the y-axis in FIG. １is disposed in contact with or crossing the other end of the second closed-circuit conductor 11b, in this example the linear conductor located on the bottom side, and is electrically connected to the other end of the second closed-circuit conductor 11b.

[0035] First conductor line 13b １ The first conductor line 13b may also serve as a linear conductor located at the other end of the second closed-circuit conductor 11b. １ is the unit cell 1 arranged in the column direction, i.e., the y direction in FIG. １１ and unit cell 1 １２ , and unit cell 1 ２１ and unit cell 1 ２２ 1. Control signals are applied from arrows A2 and A4 in FIG.

[0036] First conductor line 13a in first control line 13a １ and the first conductor line 13b in the second control line 13b １ 2, the distance d between the first conductor line 13a and the first control line 13a. １ and the first conductor line 13b in the second control line 13b １ The difference in position in the x direction between the two is 43.3 mm in the example shown in FIG.

[0037] Second conductor line 13b in second control line 13b ２ is the first conductor line 13b １ and the other terminal of the active element 12, and the first conductor line 13b １ The second conductor line 13b transmits a control signal transmitted from the second conductor line 13b to the other terminal of the active element 12. ２ is the second conductor line 13b ２ By disposing the second filter 14b in the path of the second conductor line 13b, the current induced by the incident electromagnetic wave is ２ Block the flow of water into the area.

[0038] As a result, the effective electrical length is determined by the path passing through the second closed-circuit conductor 11b, which is a meander pattern, and the second conductor line 13b ２ This prevents the resonant frequency from becoming higher due to the addition of the second closed-circuit conductor 11b, and maintains the effect of miniaturization achieved by forming the second closed-circuit conductor 11b in a meander pattern.

[0039] The other terminal of the active element 12 is connected to the second conductor line 13b. ２ via the first conductor line 13b １ and the second conductor line 13b ２ The electrical length from the other terminal of the active element 12 to the connection point of the first conductor line 13b via the second closed-circuit conductor 11b is １ The length of the first closed-circuit conductor 11b is shorter than the electrical length to the electrical connection point between the first closed-circuit conductor 11a and the second closed-circuit conductor 11b. Therefore, a delay in the transmission of the control signal for controlling the impedance of the active element 12 to the other terminal of the active element 12 can be prevented.

[0040] Second conductor line 13b ２ is formed by a conductor arranged in a straight line on the perpendicular line drawn from the apex angle to the base of the isosceles triangle of the occupied area in which the second closed-circuit conductor 11b is arranged, inside the second closed-circuit conductor 11b, in this example, as shown in Figures 1 and 2.

[0041] The first filter 14a is a filter for filtering the second conductor line 13a in the first control line 13a. ２ The first filter 14a has a characteristic of blocking current near the cutoff frequency, that is, the resonance frequency.

[0042] The first filter 14a is connected to the second conductor line 13a. ２ is divided into two at the center, and the divided second conductor line 13a ２ The second conductor line 13a is a filter component arranged in the gap between the first conductor line 13a and the second conductor line 13a. ２ are electrically connected by a filter component. The first filter 14a is connected to the second conductor line 13a. ２ The second conductor line 13b is located at the center of the ２ The filter may be formed by the pattern shown in FIG.

[0043] The second filter 14b is a second conductor line 13b in the second control line 13b. ２ The second filter 14b has a characteristic of blocking current near the cutoff frequency, that is, the resonance frequency.

[0044] The second filter 14b is a second conductor line 13b. ２ is divided into two at the center, and the divided second conductor line 13b ２ The second conductor line 13b is a filter component arranged in the gap between the first conductor line 13b and the second conductor line 13b. ２ The second filter 14b is electrically connected to the second conductor line 13b by a filter component. ２ The second conductor line 13b is located at the center of the ２ The filter may be formed by the pattern shown in FIG.

[0045] Next, the operation of the frequency selective surface 100 according to the first embodiment will be described. １１ , 1 １２ , 1 ２１ , 1 ２２ Since the control signal is transmitted to the first conductor line 13a of the first control line 13a, the operation of one unit cell 1 will be described. １ and the first conductor line 13b in the second control line 13b １ Apply to.

[0046] First conductor line 13a in first control line 13a １ The control signal applied to the second conductor line 13a ２ Since the control signal is a DC signal or a signal having only frequency components lower than the cutoff frequency, i.e., the resonant frequency, the control signal passes through the first filter 14 a and is applied to one terminal of the active element 12.

[0047] First conductor line 13b in second control line 13b １ The control signal applied to the second conductor line 13b ２ The control signal passes through the second filter 14b and is applied to the other terminal of the active element 12. Since the control signal is applied to both the one terminal and the other terminal of the active element 12, the impedance of the active element 12 is controlled to an impedance corresponding to the voltage value of the applied control signal.

[0048] In the first control line 13a, the first conductor line 13a１ to the second conductor line 13a ２ A control signal is applied to one terminal of the active element 12 through the first filter 14a, and is then applied to the first conductor line 13b through the second control line 13b. １ to the second conductor line 13b ２ Furthermore, since the control signal is applied to the other terminal of the active element 12 after passing through the second filter 14b, delays in transmission of the control signal for controlling the impedance of the active element 12 to the active element 12 can be prevented.

[0049] The resonant frequency of the first closed-circuit conductor 11a, the second closed-circuit conductor 11b and the active element 12 can be dynamically changed by changing the impedance of the active element 12 according to the voltage value of the control signal applied by the first control line 13a and the voltage value of the control signal applied by the second control line 13b.

[0050] When an electromagnetic wave of a frequency to be blocked is incident on the frequency selective surface 100, a current induced by the incident electromagnetic wave is filtered by the first filter 14a and then filtered through the second conductor line 13a. ２ The current induced by the incident electromagnetic waves is blocked from flowing into the second conductor line 13b by the second filter 14b, and almost all of the current is blocked from flowing into one terminal of the active element 12. ２ The flow to the other terminal of the active element 12 is blocked, and the flow to the other terminal of the active element 12 is almost completely blocked.

[0051] Therefore, when an electromagnetic wave of a frequency to be blocked is incident on the frequency selective surface 100, the second conductor line 13a in the first control line 13a ２ and the first filter 14a and the second conductor line 13b in the second control line 13b. ２ The second filter 14b can be considered to be substantially non-existent.

[0052] In other words, when electromagnetic waves of a frequency that is desired to be blocked are incident on the frequency selective surface 100, the characteristics of the frequency selective surface 100 according to the first embodiment with respect to the electromagnetic waves of the frequency that is desired to be blocked are determined by the second conductor lines 13a in the first control line 13a and the second control line 13b. ２, 13b ２ The characteristics of the frequency selective surface are almost the same as those when the first filter 14a and the second filter 14b are not present.

[0053] That is, when an electromagnetic wave is incident on the frequency selective surface 100, the electric field of the incident electromagnetic wave induces a current in the first closed-circuit conductor 11 a, the second closed-circuit conductor 11 b, and the active element 12. Because the resonant frequency of the first closed-circuit conductor 11 a, the second closed-circuit conductor 11 b, and the active element 12 is set to the cutoff frequency, when the frequency of the electromagnetic wave incident on the frequency selective surface 100 is the cutoff frequency, a current resonance phenomenon occurs in the first closed-circuit conductor 11 a, the second closed-circuit conductor 11 b, and the active element 12. As a result, the frequency selective surface 100 selectively blocks electromagnetic waves whose frequency is the resonant frequency.

[0054] Next, we will explain the results of electromagnetic field analysis of the relationship between the frequency of an electromagnetic wave incident on a frequency selective surface and the transmission coefficient of the frequency selective surface. For comparison with the results of the frequency selective surface 100 according to the first embodiment, we will also explain the results of comparative examples 1 to 3.

[0055] 3, Comparative Example 1 is a unit cell 2 on a frequency selective surface including a first conductor 21a, a second conductor 21b, an active element 12, a first control line 23a, and a second control line 23b. The first conductor 21a and the second conductor 21b in Comparative Example 1 are solid conductive layers each having an isosceles triangle shape, and do not form closed-circuit conductors. The unit cell 2 shown in Comparative Example 1 is also a unit cell 2 on a frequency selective surface 100 according to the first embodiment, including a first conductor 21a, a second conductor line 13a, and a second control line 23b. ２ and the second conductor line 13b of the second control line 13b ２ There is no equivalent to the first filter 14a and the second filter 14b.

[0056] 4, the unit cell 3 in the frequency selective surface includes the first closed-circuit conductor 31a, the second closed-circuit conductor 31b, the active element 12, the first control line 33a, and the second control line 33b. The unit cell 3 in the comparative example 2 has a smaller second conductor line 13a of the first control line 13a than the unit cell 1 in the frequency selective surface 100 according to the first embodiment. ２ and the second conductor line 13b of the second control line 13b ２ There is no equivalent to the first filter 14a and the second filter 14b.

[0057] As shown in FIG. 5, the comparative example 3 includes a first closed-circuit conductor 41a, a second closed-circuit conductor 41b, an active element 12, and a first conductor line 43a. １ and the second conductor line 43a ２ The first control line 43a and the first conductor line 43b have １ and the second conductor line 43b ２ The unit cell 4 of the frequency selective surface includes a second control line 43b having the first filter 14a and the second filter 14b. Compared to the unit cell 1 of the frequency selective surface 100 of the first embodiment, the unit cell 4 of the comparative example 3 does not include any filter equivalent to the first filter 14a and the second filter 14b.

[0058] The occupied areas in the unit cells 2, 3, and 4 of each of Comparative Examples 1 to 3 are the same as the occupied area in the unit cell 1 of the frequency selective surface 100 according to embodiment 1. The positional relationship between the first conductor 21 a, the first closed-circuit conductor 31 a, the first closed-circuit conductor 41 a and the second conductor 21 b, the second closed-circuit conductor 31 b, the second closed-circuit conductor 41 b, and the active element 12 in each of the unit cells 2, 3, and 4 of Comparative Examples 1 to 3 is also the same as the positional relationship between the first closed-circuit conductor 11 a and the second closed-circuit conductor 11 b, and the active element 12 in the unit cell 1 of the frequency selective surface 100 according to embodiment 1.

[0059] FIG. 6 shows the results of electromagnetic field analysis of the transmission characteristics of the frequency selective surface 100 according to the first embodiment and comparative examples 1 to 3 with respect to the frequency of the electromagnetic wave. In FIG. 6, the horizontal axis represents the frequency of the incident electromagnetic wave, and the vertical axis represents the transmission coefficient. The transmission coefficient is the ratio of the power of the transmitted electromagnetic wave to the power of the incident electromagnetic wave. The smaller the value on the vertical axis, the smaller the amount of transmission.

[0060] 6, curve E represents the verification result for the frequency selective surface 100 according to the first embodiment, curve R1 represents the verification result for comparative example 1, curve R2 represents the verification result for comparative example 2, and curve R3 represents the verification result for comparative example 3. min , R1 min , R2 min , R3 min indicates the peaks corresponding to the lowest resonance frequencies in the frequency selective surface 100 according to the first embodiment, the first comparative example, the second comparative example, and the third comparative example.

[0061] In the verification, the active element 12 was a variable capacitance diode with a capacitance of 37.35 pF. In addition, in the unit cell 1 of the frequency selective surface 100 according to the first embodiment, the first filter 14a and the second filter 14b were configured by connecting a 1 MΩ resistor, a 54.8 nH inductor, and a 1 pF capacitor in parallel. The resistors, inductors, and capacitors of the filters constituting the first filter 14a and the second filter 14b were set to values ​​that would increase the impedance of the filters near the frequency of the electromagnetic waves to be blocked.

[0062] As is clear from FIG. 6, the following can be said: When comparing Comparative Example 1 and Comparative Example 2, the resonant frequency R2 in Comparative Example 2 is min is the resonance frequency R1 in Comparative Example 1 minIn other words, by providing the notch C in the first conductor 21a and the second conductor 21b in Comparative Example 1 to form the first closed-circuit conductor 31a and the second closed-circuit conductor 31b having a meander pattern as shown in Comparative Example 2, the effective electrical length of each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b is increased, and the resonant frequency can be significantly lowered in the same occupied area. In other words, the occupied area of ​​the unit cell can be reduced for a low resonant frequency, resulting in a smaller frequency selective surface 100.

[0063] Although a low resonant frequency can be obtained in Comparative Example 2, when a control signal is applied to the active element 12 from the first control line 33a and the second control line 33b, the control signal passes through each of the first closed-circuit conductor 11a and the second closed-circuit conductor 11b, which have longer effective electrical lengths, resulting in a large delay in control of the active element 12.

[0064] In order to prevent a large delay in the control of the active element 12, as shown in Comparative Example 3, compared to Comparative Example 2, the first control line 43a is replaced with the first conductor line 43a. １ and a second conductor line 43a connecting one terminal of the active element 12 to the ２ as the second control line 43b and the first conductor line 43b １ and the other terminal of the active element 12. ２ When the comparison example 3 is compared with the comparison example 2, the delay in the control of the active element 12 is suppressed, but the resonant frequency R3 in the comparison example 3 is min is the resonant frequency R2 in Comparative Example 2 min It is higher than

[0065] Comparative Example 3 is a second conductor line 43a ２ and the second conductor line 43b ２ By providing the first conductor line 43a, the current induced by the incident electromagnetic wave flows through the first conductor line 43a. １ to the second conductor line 43a ２ a path through which current flows to one terminal of the active element 12 via the first conductor line 43b １to the second conductor line 43b ２ Since a path is created through which current flows to the other terminal of the active element 12 via the min is the resonant frequency R2 in Comparative Example 2 min It becomes higher compared to

[0066] In contrast, the frequency selective surface 100 according to the first embodiment is obtained by adding a first filter 14 a and a second filter 14 b to the components of the third comparative example. Because the first filter 14 a and the second filter 14 b each pass a control signal, the frequency selective surface 100 according to the first embodiment can suppress an increase in the delay in control of the active element 12, similar to the third comparative example.

[0067] Furthermore, the resonant frequency E min is the resonant frequency R2 in Comparative Example 2 min That is, the frequency selective surface 100 according to the first embodiment has a second conductor line 13a of the first control line 13a, which is equivalent to the first control line 13a of the second conductor line 13a of the first control line 13a. ２ and the second conductor line 13b of the second control line 13b ２ By providing the first filter 14a and the second filter 14b, the first conductor line 43a １ to the second conductor line 43a ２ a path through which current flows to one terminal of the active element 12 via the first conductor line 43b １ to the second conductor line 43b ２ However, the first filter 14a does not pass the current induced by the incident electromagnetic wave of the resonant frequency through the second conductor line 13a. ２ and the first conductor line 43a １ The second filter 14b connects the second conductor line 13b to one terminal of the active element 12. ２ and the first conductor line 43b １ The path from the terminal A to the other terminal of the active element 12 is cut off.

[0068] As is clear from the verification results shown in FIG. 6, the frequency selective surface 100 according to the first embodiment has the first closed-circuit conductor 31a and the second closed-circuit conductor 31b which are meander patterns, and the first conductor line 43a １ and the second conductor line 43a ２ The first control line 43a and the first conductor line 43b have １ and the second conductor line 43b ２ The second control line 43b having the first filter 14a and the second filter 14b is provided, so that the size can be reduced for a low resonance frequency, and the control signal is transmitted through the first conductor line 43a. １ and the first conductor line 43b １ The path from the power supply 11 to the active element 12 can be shortened.

[0069] Next, the results of verifying the transmission coefficient for the frequency of the electromagnetic wave by changing the capacitance value of the active element 12 in the frequency selective surface 100 according to embodiment 1 through electromagnetic field analysis will be described with reference to Fig. 7. For comparison with the verification results of the frequency selective surface 100 according to embodiment 1, the verification results of comparative example 2 will also be described.

[0070] In Fig. 7, the horizontal axis represents the frequency of the incident electromagnetic wave, and the vertical axis represents the transmission coefficient. １ The curve E is a result of verification when the capacitance value of the active element 12 is set to 37.35 pF in the frequency selective surface 100 according to the first embodiment. ２ 1 shows the results of the verification when the capacitance value of the active element 12 is set to 2.38 pF in the frequency selective surface 100 according to the first embodiment, and curve R2 １ The curve R2 shows the verification results when the capacitance value of the active element 12 is set to 37.35 pF in Comparative Example 2. ２ 10 shows the verification results when the capacitance value of the active element 12 in Comparative Example 2 is set to 2.38 pF.

[0071] As is clear from the verification results shown in FIG. 7, in the frequency selective surface 100 according to the first embodiment, the resonant frequency E 1min and the resonant frequency E when the capacitance value of the active element 12 is 2.38 pF. 2minThe resonant frequency E when the capacitance value of the active element 12 is 37.35 pF is 1min and the resonant frequency E at 2.38 pF 2min The resonant frequency R2 when the capacitance value of the active element 12 in Comparative Example 2 is 37.35 pF 1min and the resonant frequency R2 at 2.38 pF 2min are equivalent to each other.

[0072] That is, the frequency selective surface 100 according to the first embodiment can change the resonant frequency of the frequency selective surface by changing the capacitance value of the active element 12. In short, in the frequency selective surface 100 according to the first embodiment, the transmission characteristics of electromagnetic waves on the frequency selective surface change as the characteristics of the active element 12 change, that is, the characteristics of the frequency selective surface can be dynamically controlled by changing the characteristics of the active element 12.

[0073] Next, in the frequency selective surface 100 according to the first embodiment, the first conductor line 13a in the first control line 13a １ and the first conductor line 13b in the second control line 13b １ The transmission coefficient for the frequency of the electromagnetic wave was verified by electromagnetic field analysis while changing the distance d between the electrodes. The verification results for unit cell 1 with the distance d set to the following eight values ​​will be described with reference to Figure 15. In Figure 15, the horizontal axis represents the frequency of the incident electromagnetic wave, and the vertical axis represents the transmission coefficient.

[0074] 15 , curve E1 represents the verification result of the unit cell 1 shown in FIG. 2 when the distance d is 43.3 mm, curve E2 represents the verification result of the unit cell 1 shown in FIG. 8 when the distance d is 41.0 mm, curve E3 represents the verification result of the unit cell 1 shown in FIG. 9 when the distance d is 38.7 mm, curve E4 represents the verification result of the unit cell 1 shown in FIG. 10 when the distance d is 37.2 mm, curve E5 represents the verification result of the unit cell 1 shown in FIG. 11 when the distance d is 20.5 mm, curve E6 represents the verification result of the unit cell 1 shown in FIG. 12 when the distance d is 18.2 mm, curve E7 represents the verification result of the unit cell 1 shown in FIG. 13 when the distance d is 15.9 mm, and curve E8 represents the verification result of the unit cell 1 shown in FIG. 14 when the distance d is 14.4 mm.

[0075] In the verification, the capacitance value of the active element 12 was set to 37.35 pF, and the first filter 14a and the second filter 14b were configured by connecting a 1 MΩ resistor, a 54.8 nH inductor, and a 1 pF capacitor in parallel.

[0076] As is clear from FIG. 15, the greater the distance d, that is, the greater the width of the first conductor line 13a in the first control line 13a. １ and the first conductor line 13b in the second control line 13b １ The farther away from the active element 12 the first conductor line 13a is, the lower the resonant frequency tends to be. １ and the first conductor line 13b １ The further away they are from the active element 12, the smaller the size can be for a lower resonant frequency.

[0077] In other words, one end of the first closed-circuit conductor 11a is connected to one terminal of the active element 12, and the other end of the first conductor line 13a is connected to the other terminal of the first closed-circuit conductor 11a. １ The other end of the second closed-circuit conductor 11b is connected to one end of the active element 12, and the first conductor line 13b is connected to the other end of the second closed-circuit conductor 11b. １ It is most preferable to place

[0078] First conductor line 13a １ and the first conductor line 13b １ Even if they are located far from the active element 12, as described above, the second conductor line 13a of the first control line 13a ２ and the second conductor line 13b of the second control line 13b ２ Since the first filter 14a and the second filter 14b are provided, the control signal is input to the first conductor line 43a. １ and the first conductor line 43b １ This shortens the path from the power supply 11 to the active element 12, thereby preventing the control delay from increasing.

[0079] In the frequency selective surface 100 of embodiment 1, in each of a plurality of periodically arranged unit cells 1, the first closed-circuit conductor 11a and the second closed-circuit conductor 11b, to which each of the two terminals of the active element 12 arranged between the unit cells 1 is electrically connected at one end, are each shaped as a meander pattern, thereby enabling the frequency selective surface to be dynamically controlled by the active element 12 and having a low resonant frequency for incident electromagnetic waves to be miniaturized.

[0080] Furthermore, the frequency selective surface 100 according to the first embodiment includes a first control line 13a and a second control line 13b that transmit a control signal to be applied to the active element 12, and a first conductor line 13a that is electrically connected to the other end of the corresponding closed-circuit conductor 11a, 11b. １ , 13b １ , and the first conductor line 13a １ , 13b １ and the active element 12. ２ , 13b ２ This prevents a delay in the control of the active element 12 by the control signal. In short, the frequency selective surface 100 according to the first embodiment can be made smaller for a low resonant frequency while preventing a delay in the control by the control signal.

[0081] In the first embodiment, the first closed-circuit conductor 11a and the second closed-circuit conductor 11b in each unit cell 1 each have a meander pattern, but at least one of the closed-circuit conductors may have a meander pattern.

[0082] Second Embodiment A frequency selective surface 100A according to a second embodiment will be described with reference to Figures 16 and 17. The frequency selective surface 100 according to the first embodiment has a second conductor line 13a in the first control line 13a. ２ is disposed inside the first closed-circuit conductor 11a, and the second conductor line 13b in the second control line 13b ２ is disposed inside the second closed-circuit conductor 11b.

[0083] In contrast, the frequency selective surface 100A according to the second embodiment has a second conductor line 13a in the first control line 13a. ２ is disposed outside the first closed-circuit conductor 11a, and the second conductor line 13b in the second control line 13b ２ The difference is that the second conductor line 13a is disposed outside the second closed-circuit conductor 11b, and the other points are the same. ２ and the second conductor line 13b ２ 16, the same reference numerals as those in FIGS. 1 and 2 denote the same or corresponding parts.

[0084] As shown in FIG. 16, the unit cell 1 in the frequency selective surface 100A according to the second embodiment includes a first closed-circuit conductor 11a, a second closed-circuit conductor 11b, an active element 12, and a first conductor line 13a. １ and the second conductor line 13a ２１ , 13a ２２ The first control line 13a and the first conductor line 13b have １ and the second conductor line 13b ２１ , 13b ２２ a second control line 13b having a first filter 14a; １ , 14a ２ and the second filter 14b １ , 14b ２ Equipped with.

[0085] Second conductor line 13a in first control line 13a ２１ , 13a ２２ is disposed outside the first closed-circuit conductor 11a. ２１ , 13a ２２ is the second conductor line 13a forming the first path. ２１ and a second conductor line 13a forming a second path. ２２ It consists of:

[0086] A second conductor line 13a forming the first path ２１ is formed by a conductor arranged linearly along one of the equilateral sides outside the occupied area of ​​the isosceles triangle in which the first closed-circuit conductor 11a is arranged, and the first conductor line 13a１ and one terminal of the active element 12, and the first conductor line 13a １ The control signal transmitted from the second conductor line 13a is transmitted to one terminal of the active element 12. ２１ The first path includes a first filter 14a. １ By arranging the second conductor line 13a, the current induced by the incident electromagnetic wave is ２１ Block the flow of water into the area.

[0087] A second conductor line 13a forming a second path ２２ is formed by a conductor linearly arranged along the other equilateral side outside the occupied area of ​​the isosceles triangle in which the first closed-circuit conductor 11a is arranged, and the first conductor line 13a １ and one terminal of the active element 12, and the first conductor line 13a １ The control signal transmitted from the second conductor line 13a is transmitted to one terminal of the active element 12. ２２ The second path is connected to the first filter 14a. ２ By arranging the second conductor line 13a, the current induced by the incident electromagnetic wave is ２２ Block the flow of water into the area.

[0088] As a result, the effective electrical length is determined by the path passing through the first closed-circuit conductor 11a, which is a meander pattern, and the second conductor line 13a ２１ , 13a ２２ This prevents the resonant frequency from becoming higher due to the addition of the first closed-circuit conductor 11a, and maintains the effect of miniaturization achieved by forming the first closed-circuit conductor 11a into a meander pattern.

[0089] The control signal is transmitted through the first conductor line 13a. １ to the second conductor line 13a ２１ and the second conductor line 13a ２２ , and therefore, a delay in the transmission of the control signal for controlling the impedance of the active element 12 to one terminal of the active element 12 can be prevented.

[0090] Second conductor line 13b in second control line 13b２１ , 13b ２２ is disposed outside the second closed-circuit conductor 11b. ２１ , 13b ２２ is the second conductor line 13b forming the first path ２１ and a second conductor line 13b forming a second path. ２２ It consists of:

[0091] A second conductor line 13b forming the first path ２１ is formed by a conductor arranged linearly along one of the equilateral sides outside the occupied area of ​​the isosceles triangle in which the second closed-circuit conductor 11b is arranged, and the first conductor line 13b １ and the other terminal of the active element 12, and the first conductor line 13b １ The control signal transmitted from the second conductor line 13b is transmitted to the other terminal of the active element 12. ２１ is connected to the first path through the second filter 14b. １ By arranging the second conductor line 13b, the current induced by the incident electromagnetic wave is ２１ Block the flow of water into the area.

[0092] A second conductor line 13b forming a second path ２２ is formed by a conductor arranged linearly along the other equilateral side outside the occupied area of ​​the isosceles triangle in which the second closed-circuit conductor 11b is arranged, and the first conductor line 13b １ and the other terminal of the active element 12, and the first conductor line 13b １ The second conductor line 13b forms a second path and transmits a control signal transmitted from the second conductor line 13b to the other terminal of the active element 12. ２２ The second path includes a second filter 14b. ２ By arranging the second conductor line 13b, the current induced by the incident electromagnetic wave is ２２ Block the flow of water into the area.

[0093] As a result, the effective electrical length is determined by the path passing through the second closed-circuit conductor 11b, which is a meander pattern, and the second conductor line 13b ２１ , 13b ２２This prevents the resonant frequency from becoming higher due to the addition of the first closed-circuit conductor 11a, and maintains the effect of miniaturization achieved by forming the first closed-circuit conductor 11a into a meander pattern.

[0094] The control signal is transmitted through the first conductor line 13b. １ to the second conductor line 13b ２１ and the second conductor line 13b ２２ , and therefore, a delay in the transmission of the control signal for controlling the impedance of the active element 12 to the other terminal of the active element 12 can be prevented.

[0095] First filter 14a １ , 14a ２ represents the second conductor line 13a in the first control line 13a ２１ The first filter 14a is disposed in the path (first path) of the １ and the second conductor line 13a in the first control line 13a ２２ The first filter 14a is disposed in the path (second path) ２ The first filter 14a disposed in the first path １ and a first filter 14a disposed in the second path. ２ Each blocks electromagnetic waves of the target frequency.

[0096] First filter 14a １ and the first filter 14a ２ Each has a cutoff frequency, that is, the characteristic of cutting off current near the resonant frequency.

[0097] A first filter 14a disposed in the first path １ is the second conductor line 13a ２１ is divided into two at the end on the active element 12 side, and the divided second conductor line 13a ２１ The second conductor line 13a is a filter component arranged in the gap between the first conductor line 13a and the second conductor line 13a. ２１ are electrically connected by a filter component. １ is the second conductor line 13a ２１ The second conductor line 13a is connected to the end of the active element 12 side of the ２１The filter may be formed by the pattern shown in FIG.

[0098] A first filter 14a disposed in the second path ２ is the second conductor line 13a ２２ is divided into two at the end on the active element 12 side, and the divided second conductor line 13a ２２ The second conductor line 13a is a filter component arranged in the gap between the first conductor line 13a and the second conductor line 13a. ２２ are electrically connected by a filter component. ２ is the second conductor line 13a ２２ The second conductor line 13a is connected to the end of the active element 12 side of the ２２ The filter may be formed by the pattern shown in FIG.

[0099] Second filter 14b １ , 14b ２ is the second conductor line 13b in the second control line 13b ２１ The second filter 14b is disposed in the path (first path) of １ and the second conductor line 13b in the second control line 13b ２２ The second filter 14b is disposed in the path (second path) of ２ It consists of:

[0100] A second filter 14b disposed in the first path １ and a second filter 14b disposed in the second path. ２ Each of the second filters 14b blocks electromagnetic waves of the target frequency. １ and the second filter 14b ２ Each has a cutoff frequency, that is, the characteristic of cutting off current near the resonant frequency.

[0101] A second filter 14b disposed in the first path １ is the second conductor line 13b ２１ is divided into two at the end on the active element 12 side, and the divided second conductor line 13b ２１ The second conductor line 13b is a filter component arranged in the gap between the first conductor line 13b and the second conductor line 13b. ２１ are electrically connected by a filter component.１ is the second conductor line 13b ２１ The second conductor line 13b is connected to the end of the active element 12 side of the ２１ The filter may be formed by the pattern shown in FIG.

[0102] A second filter 14b disposed in the second path ２ is the second conductor line 13b ２２ is divided into two at the end on the active element 12 side, and the divided second conductor line 13b ２２ The second conductor line 13b is a filter component arranged in the gap between the first conductor line 13b and the second conductor line 13b. ２２ are electrically connected by a filter component. ２ is the second conductor line 13b ２２ The second conductor line 13b is connected to the end of the active element 12 side of the ２２ The filter may be formed by the pattern shown in FIG.

[0103] The operation of the frequency selective surface 100A according to the second embodiment is substantially the same as the operation of the frequency selective surface 100 according to the first embodiment, and therefore a description thereof will be omitted.

[0104] Next, the results of verifying the transmission coefficient for the frequency of the electromagnetic wave by electromagnetic field analysis when the capacitance value of the active element 12 is changed in the frequency selective surface 100A according to the second embodiment will be described with reference to Fig. 17. The verification of the frequency selective surface 100A according to the second embodiment also involves the second conductor line 13a in the first control line 13a. ２１ , 13a ２２ and the second conductor line 13b in the second control line 13b ２１ , 13b ２２ and the first filter 14a １ , 14a ２ and the second filter 14b １ , 14b differ from the frequency selective surface 100 according to the first embodiment, and other conditions are the same as those of the frequency selective surface 100 according to the first embodiment.

[0105] In Fig. 17, the horizontal axis represents the frequency of the incident electromagnetic wave, and the vertical axis represents the transmission coefficient. １The curve E is a result of verification when the capacitance value of the active element 12 is set to 37.35 pF in the frequency selective surface 100 according to the first embodiment. ２ 1 shows the results of the verification when the capacitance value of the active element 12 is set to 2.38 pF in the frequency selective surface 100 according to the first embodiment. ３ 1 shows the results of a test performed on the frequency selective surface 100A according to the second embodiment when the capacitance of the active element 12 is set to 37.35 pF. ４ 10 shows the verification results when the capacitance value of the active element 12 in the frequency selective surface 100A according to the second embodiment is set to 2.38 pF.

[0106] 17, the frequency selective surface 100A according to the second embodiment and the frequency selective surface 100 according to the first embodiment exhibit substantially the same resonant frequencies. The frequency selective surface 100A according to the second embodiment has the same effect as the frequency selective surface 100 according to the first embodiment.

[0107] In the second embodiment, the first closed-circuit conductor 11a and the second closed-circuit conductor 11b in each unit cell 1 each have a meander pattern, but at least one of the closed-circuit conductors may have a meander pattern.

[0108] It should be noted that the embodiments may be freely combined, any of the components of the embodiments may be modified, or any of the components of the embodiments may be omitted.

[0109] The frequency selective surface according to the present disclosure is used in the field of wireless communication, and is applied to the frequency selective surface to effectively prevent interference and information leakage between wireless systems.

[0110] 100 Frequency selective surface, 10 Dielectric substrate, 1, 1 １１ , 1 １２ , 1 ２１ , 1 ２２ Unit cell, 11a: first closed-circuit conductor, 11b: second closed-circuit conductor, 12: active element, 13a: first control line, 13b: second control line, 13a １ , 13b １ First conductor line, 13a ２ , 13b ２A second conductor line, 14a a first filter, and 14b a second filter.

Claims

1. A frequency selective surface comprising a plurality of unit cells arranged periodically, each of the plurality of unit cells comprising: a first closed conductor having a meander pattern shape; a second closed conductor having one end facing one end of the first closed conductor with a gap therebetween; an active element having one terminal electrically connected to one end of the first closed conductor and the other terminal electrically connected to one end of the second closed conductor in the gap between one end of the first closed conductor and one end of the second closed conductor, the active element having an impedance that changes depending on the voltage value of an applied control signal; and a first control line arranged corresponding to the first closed conductor, the first control line having a first conductor line conducting with the other end of the first closed conductor and a second conductor line electrically connecting the first conductor line and one terminal of the active element, the first control line transmitting a control signal to be applied to the active element. a first filter disposed on a path of the second conductor line of the first control line, for blocking electromagnetic waves of a frequency to be blocked.

2. A frequency selective surface as claimed in claim 1, comprising: a second control line that transmits a control signal to be applied to the active element; and a second filter that is arranged in the path of the second conductor line of the second control line, the second control line having a meander pattern shape for the second closed conductor and a first conductor line that is electrically connected to the other end of the second closed conductor and a second conductor line that electrically connects the first conductor line and the other terminal of the active element. The second control line has a meander pattern shape for the second closed conductor and a second conductor line that is electrically connected to the other terminal of the active element.

3. A frequency selective surface as described in claim 1 or claim 2, wherein the electrical length from the active element via the second conductor line in the first control line to the connection point between the first conductor line and the second conductor line in the first control line is shorter than the electrical length from the active element via the first closed-circuit conductor to the conduction point between the first conductor line in the first control line and the first closed-circuit conductor.

4. The frequency selective surface of claim 2, wherein the electrical length from the active element, via the second conductor line in the first control line, to the connection point between the first conductor line and the second conductor line in the first control line is shorter than the electrical length from the active element, via the first closed-circuit conductor, to the connection point between the first conductor line in the first control line and the first closed-circuit conductor, and the electrical length from the active element, via the second conductor line in the second control line, to the connection point between the first conductor line and the second conductor line in the second control line is shorter than the electrical length from the active element, via the second closed-circuit conductor, to the connection point between the first conductor line in the second control line and the second closed-circuit conductor.

5. A frequency selective surface according to any one of claims 1 to 4, wherein the meander pattern in the shape of the first closed conductor occupies an area in the shape of an isosceles triangle for placement, with multiple notches formed inward from each equal side of the isosceles triangle parallel to the base, and is symmetrical with respect to a perpendicular line drawn from the apex angle of the isosceles triangle to the base.

6. The frequency selective surface according to claim 5, wherein the end where the first closed-circuit conductor and the second closed-circuit conductor are arranged opposite to each other is the end on the apex side.

7. A frequency selective surface as described in claim 2, wherein the meander pattern in the shape of the first closed-circuit conductor has an occupied area for placement in the first closed-circuit conductor that is an isosceles triangular area, with multiple notches formed inward from each equal side of the isosceles triangle parallel to the base, and is symmetrical with respect to a perpendicular line drawn from the apex angle of the isosceles triangle to the base; and wherein the meander pattern in the shape of the second closed-circuit conductor has an occupied area for placement in the second closed-circuit conductor that is an isosceles triangular area, with multiple notches formed inward from each equal side of the isosceles triangle parallel to the base, and is symmetrical with respect to a perpendicular line drawn from the apex angle of the isosceles triangle to the base.

8. The frequency selective surface according to claim 7, wherein the end where the first closed-circuit conductor and the second closed-circuit conductor are arranged opposite to each other is the end on the apex side.

9. A frequency selective surface as described in any one of claims 1 to 8, wherein the resonant frequency determined by the shape of the first closed-circuit conductor and the impedance of the active element is set to the cutoff frequency of electromagnetic waves incident on the frequency selective surface.

10. A frequency selective surface according to any one of claims 1 to 9, wherein the second conductor line of the first control line is arranged inside the first closed-loop conductor.

11. A frequency selective surface as described in any one of claims 2, 4, 7, or 8, wherein the second conductor line of the second control line is arranged inside the second closed-loop conductor.

12. A frequency selective surface according to any one of claims 1 to 9, wherein the second conductor line of the first control line is arranged outside the first closed-loop conductor.

13. A frequency selective surface according to any one of claims 2, 4, 7, or 8, wherein the second conductor line of the second control line is positioned outside the second closed-circuit conductor.

14. A frequency selective surface according to any one of claims 1 to 13, wherein the first filter is a filter component arranged in a gap between two halves of a second conductor line in the first control line, and the two halves of the second conductor line are electrically connected by the filter component.

15. A frequency selective surface according to any one of claims 2, 4, 7, or 8, wherein the second filter is a filter component disposed in a gap between two halves of the second conductor line of the second control line, and the two halves of the second conductor line are electrically connected by the filter component.

16. A frequency selective surface according to any one of claims 1 to 13, wherein the first filter is a filter formed by patterning a second conductor line in the first control line.

17. A frequency selective surface according to any one of claims 2, 4, 7, or 8, wherein the second filter is a filter formed by patterning a second conductor line in the second control line.

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