Antenna balun, and antenna array system using the antenna balun

Abstract

To provide an antenna balun that can achieve miniaturization and an antenna array system using the antenna balun.SOLUTION: The antenna balun has a first conductor with a first electrode of the first capacitance element, a first inductance element, and a first electrode of the second capacitance element in the first layer, and a second conductor with a second electrode of the first capacitance element, a second inductance element, and a second electrode of the second capacitance element in the second layer, which is located opposite the first layer.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an antenna balun and an antenna array system using the antenna balun.

Background Art

[0002] For example, artificial satellites orbiting the Earth are equipped with antennas for communication and radio wave observation with radio base stations installed on the ground. In artificial satellites and the like, especially in the low-frequency range using linear antennas, there are cases where a stable ground conductor cannot be obtained, or there are physical or electrical interference sources in the surroundings, and it may be difficult to use an unbalanced antenna that shares a ground conductor. As a countermeasure, instead of a monopole antenna, for example, a dipole antenna or the like may be used. However, in this case, the antenna size becomes large. And when antenna efficiency is required, for example, an unbalanced-to-balanced circuit or the like may be further required.

[0003] Conventionally, a balanced antenna has been used in combination with an unbalanced-to-balanced converter called an antenna balun (for example, Patent Document 1). An antenna balun is a conversion device for correctly feeding power to a balanced antenna that operates electrically symmetrically to improve communication efficiency and interference with the outside. When the target frequency in communication is high (the wavelength λ is short) and the required communication bandwidth is narrow, as an antenna balun, those having a structure with dimensions based on the wavelength λ for communication (for example, λ / 4) are often used. Also, a method has been proposed in which an antenna balun is configured by vertically connecting unbalanced-to-balanced converter circuits in multiple stages to achieve broadband communication.

[0004] In recent years, miniaturization of antennas has been demanded. For this reason, in recent years, when the communication frequency is low or a wide communication bandwidth is required, miniaturization of the antenna balun has also been achieved by using electronic components such as coils that can achieve miniaturization.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in some cases where an antenna is used in a special environment such as outer space, the use of electronic components may not be allowed for miniaturization of the antenna balun. For this reason, there is a grounding constraint in which a sufficient grounding conductor cannot be obtained, and when an antenna is used in a special environment where electronic components cannot be used, it may be difficult to miniaturize the antenna balun.

[0007] The present invention has been made based on the above recognition of the problem, and an object thereof is to provide an antenna balun capable of achieving miniaturization, and an antenna array system using the antenna balun.

Means for Solving the Problems

[0008] To achieve the above object, an antenna balun according to an aspect of the present invention includes a first conductor provided in a first layer with a first electrode of a first capacitive element, a first inductive element, and a first electrode of a second capacitive element, and a second layer disposed opposite to the first layer, the second layer having a second electrode of the first capacitive element, a second inductive element, and a second electrode of the second capacitive element.

Effects of the Invention

[0009] According to an aspect of the present invention, miniaturization of an antenna balun and an antenna array system using the antenna balun can be achieved.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

[0011] Hereinafter, with reference to the drawings, embodiments of the antenna balun of the present invention and an antenna system using the antenna balun will be described. In an antenna system for low-frequency reception, in an environment where each antenna cannot obtain an independent and stable ground conductor, or in an environment where mechanical or electrical interference objects exist in the surroundings, it is necessary to use a balanced antenna such as a dipole antenna. In that case, the size of the dipole antenna becomes large in the low-frequency region and is subject to mounting restrictions. In addition, the waveguide-type antenna balun circuit for improving the antenna efficiency also becomes large, which is a problem.

[0012] [Configuration of Antenna Array System] FIG. 1 is a diagram showing an example of the configuration of the antenna array system according to the embodiment. The antenna array system 1 shown in FIG. 1 is, for example, an antenna array system in which a plurality of antennas 10 and a plurality of antenna baluns 20 according to the embodiment are connected in series.

[0013] Antenna 10 is a balanced antenna such as, for example, a dipole antenna. In the antenna array system 1 shown in FIG. 1, unbalanced power fed from a feeding point 30 (for example, power fed via an unbalanced transmission line such as a coaxial cable) is converted by an antenna balun 20 into balanced-phase power suitable for the antenna 10 and fed thereto. In this case, the phase by which the antenna balun 20 converts the power fed from the feeding point 30 is 180°.

[0014] Furthermore, in the antenna array system 1 shown in FIG. 1, a three-stage antenna balun array 20A is configured by connecting three antenna baluns 20 in cascade, and power from the feeding point 30 converted by each antenna balun array 20A is fed to the corresponding antenna 10. More specifically, the feeding point 30 is connected to the first stage of the antenna balun array 20A, and power converted by each antenna balun 20 is fed from the third-stage antenna balun 20 to each of the antennas 10a and 10b that are paired in the antenna 10. By connecting the antenna baluns 20 in cascade, the communication bandwidth in the antenna 10 can be widened, that is, broadened.

[0015] The antenna balun array 20A is an example of the "array unit" in the claims.

[0016] The antenna balun 20 is a balun that focuses on low-frequency communication. The antenna balun 20 does not use electronic components such as coils, but is composed of an inductance element (L) and a capacitance element (C) using the circuit technology of a composite right / left-handed (CRLH) waveguide based on metamaterial technology. As a result, the antenna balun 20 can be miniaturized compared to a simple waveguide-type balun. More specifically, in a simple waveguide-type balun, for example, it is necessary to be configured with a dimension of λ / 4 of the operating frequency (a dimension corresponding to half the length of the antenna 10), but the antenna balun 20 can be configured with a dimension of, for example, λ / 40, which corresponds to the dimension of an electronic component.

[0017] [Configuration of Antenna Balun] FIG. 2 is a diagram showing an example of the structure of the antenna balun 20 according to the embodiment. FIG. 2 shows the structure of one antenna balun 20. The antenna balun 20 includes a conductor 20-1 having a predetermined thickness and a conductor 20-2. FIG. 2(a) shows an example of the arrangement of the conductor 20-1 and the conductor 20-2 when the antenna balun 20 is configured. FIG. 2(b) shows the cross-sectional structure of the antenna balun 20 shown in FIG. 2(a). As shown in FIG. 2(b), in the antenna balun 20, the conductor 20-1 and the conductor 20-2 are arranged to face each other with an insulator IS interposed therebetween. In other words, the antenna balun 20 is formed of two layers of conductors, the conductor 20-1 and the conductor 20-2. The insulator IS is a dielectric used when forming a capacitance element, such as resin, for example. FIGS. 2(c) and 2(d) each show an example of the shape of the conductor 20-1 or the conductor 20-2 when the antenna balun 20 shown in FIG. 2(a) is disassembled (however, the insulator IS is omitted).

[0018] The conductor 20-1 is an example of the "first layer" and the "first conductor" in the claims. The conductor 20-2 is an example of the "second layer" and the "second conductor" in the claims.

[0019] Each of the conductors 20-1 and 20-2 is, for example, a metal plate such as a copper plate or an iron plate. Each of the conductors 20-1 and 20-2 may be a plate of the same metal material as the antenna 10, such as aluminum or brass. In each of the conductor 20-1 and the conductor 20-2, in addition to the right-handed system as the original parallel lines, a left-handed meander line inductor LL&LR and a left-handed MIM (Metal-Insulator-Metal) capacitor CR&CL formed between the conductor and the other conductor constitute a CRLH waveguide. More specifically, from the terminal P1 to the terminal P2, a left-handed inductance element LL connected in parallel to the right-handed parallel line and a left-handed capacitance element CL connected in series to the right-handed parallel line are formed. From the terminal P1 to the terminal P3, a left-handed inductance element LR connected in parallel to the right-handed parallel line and a left-handed capacitance element CR connected in series to the right-handed parallel line are formed. In FIG. 2, as an example of the embodiment, a case is shown in which the inductance element LL and the inductance element LR are formed in separate conductor layers in a region up to half (L / 2) of the balun length L. By the CRLH circuit, the balun length L is, for example, a length of λ / 40 (0.025λ).

[0020] As shown in FIG. 2(b), the conductors 20-1 and 20-2 are arranged to face each other with the insulator IS interposed therebetween. In the antenna balun 20, a capacitor element CL having an MIM structure with the first electrode CL-A and the second electrode CL-B as electrodes is configured, and a capacitor element CR having an MIM structure with the first electrode CR-A and the second electrode CR-B as electrodes is configured. By changing the sizes (areas) of the first electrode CL-A and the second electrode CL-B, the capacitance value of the capacitor element CL can be changed (adjusted, optimized), and by changing the areas of the first electrode CR-A and the second electrode CR-B, the capacitance value of the capacitor element CR can be adjusted.

[0021] As shown in FIG. 2, in the conductors 20-1 and 20-2, a portion of the conductor formed thin (hereinafter, for ease of explanation, referred to as a "conductive wire") is formed to be folded back (forming a meander line structure). In the antenna balun 20, the inductance element LL and the inductance element LR are respectively constituted. By changing the length, width (thinness), and number of folds of the conductive wire in the meander line structure, the inductance values of the inductance element LL and the inductance element LR can be adjusted.

[0022] The capacitance element CL is an example of the "first capacitance element" in the claims, and the inductance element LL is an example of the "first inductance element" in the claims. The capacitance element CR is an example of the "second capacitance element" in the claims, and the inductance element LR is an example of the "second inductance element" in the claims.

[0023] In the antenna balun 20, a feeding point 30 is connected to the conductors 20-1 and 20-2 on the terminal P1 side. And in the antenna balun 20, the antenna 10 is connected to the terminal P2 of the conductor 20-1 and the terminal P3 of the conductor 20-2. More specifically, the center wire of the coaxial cable for transmitting the power from the feeding point 30 is connected to the terminal P1 of the conductor 20-1 constituting the antenna balun 20, and the ground (grounding) wire of the coaxial cable is connected to the terminal P1 of the conductor 20-2. This connection may be reversed. Then, one side of the antenna 10 (for example, antenna 10a) is connected to the terminal P2 of the conductor 20-1 constituting the antenna balun 20, and the other side of the antenna 10 (for example, antenna 10b) is connected to the terminal P3 of the conductor 20-2.

[0024] Here, the equivalent circuit of the antenna balun 20 will be described. FIG. 3 is a circuit diagram showing the equivalent circuit of the antenna balun 20 according to the embodiment. FIG. 3 also shows the load impedance Z30 of the feeding point 30 connected to each of the antenna baluns 20, the load impedance Z11 of one antenna 10, and the load impedance Z12 of the other antenna 10 together.

[0025] As shown in FIG. 3, in the left-handed waveguide LH, a capacitive element CL is connected in series in the path from terminal P1 to terminal P2, and an inductive element LL is connected in parallel between the capacitive element CL and terminal P2. On the other hand, in the right-handed waveguide RH, an inductive element LR is connected in series in the path from terminal P1 to terminal P3, and a capacitive element CR is connected in parallel between the inductive element LR and terminal P3. Then, the inductive element LL and the capacitive element CR are connected in series, and the connection point between the inductive element LL and the capacitive element CR is connected to a common ground with the load impedance Z30, the load impedance Z11, and the load impedance Z12. If the positive and negative (feeding positive and negative) of the feeding point of terminal P1 are reversed, the relationship between the left-handed and right-handed systems is reversed. Since it is actually formed on a parallel line as shown in FIG. 2, an operation can be obtained in which a left-handed circuit is added from each of the feeding positive and negative to a normal right-handed circuit.

[0026] Thus, in the antenna balun 20, a circuit of a CRLH waveguide as shown in the equivalent circuit diagram of FIG. 3 is realized by the structure shown in FIG. 2. Thereby, in the antenna balun 20, the phase of the power imbalance fed from the feeding point 30 can be converted into a balanced phase of 180° suitable for the antenna 10 and fed.

[0027] Here, an example of the characteristics of the antenna balun 20 will be described. FIG. 4 is a diagram showing an example of the phase characteristics of the antenna balun 20 according to the embodiment. The phase characteristics shown in FIG. 4 are the S21 and S31 characteristics when the balun length L in the structure of the antenna balun 20 shown in FIG. 2 is 0.025λ. The antenna balun 20 can maintain a phase difference of 180° between the characteristic S21 and the characteristic S31 within the verified frequency range (band).

[0028] Next, the passing characteristics of the antenna balun 20 will be described with reference to FIG. 5. FIG. 5 is a diagram showing an example of the passing characteristics of the antenna balun 20 according to the embodiment. In the frequency band of the verified frequency, the antenna balun 20 can obtain a frequency with a strong (high) signal intensity and a frequency with a weak (low) signal intensity for each of the characteristics S21 and S31. In other words, in the antenna array system 1, the frequency band with a strong (high) signal intensity of the antenna balun 20 can be used as the passing band of the communication frequency, and the frequency band with a weak (low) signal intensity can be used as the insensitive band of the communication frequency. In other words, in the antenna array system 1, the same effect as that of configuring a filter by the antenna balun 20 can be obtained.

[0029] In the antenna balun 20, since the characteristics as shown in FIGS. 4 and 5 can be obtained, as described above, by adjusting (that is, optimizing) the capacitance values of the capacitor elements CL and CR and the inductance values of the inductor elements LL and LR, the communication characteristics required in the communication of the antenna array system 1 can be realized. That is, according to the characteristics shown in FIG. 4, a stable 180° phase difference can be maintained in the paired antenna 10, and according to the characteristics shown in FIG. 5, one or both of the passing band and the insensitive band of the communication frequency can be formed, efficient communication can be performed, and external interference to the communication can be suppressed. Further, as described above, by cascading a plurality of antenna baluns 20, the broadbanding of the communication of the antenna array system 1 can be realized.

[0030] Here, an example of cascading the antenna balun 20 will be described. FIG. 6 is a diagram showing an example of the structure of the antenna balun array 20A according to the embodiment. FIG. 6 shows the structure of the antenna balun array 20A in which the antenna balun 20 having the structure shown in FIG. 2 is cascaded in three stages. As shown in FIG. 6, when configuring the antenna balun array 20A, the conductors 20-1 and the conductors 20-2 that make up each of the antenna baluns 20 to be connected are connected to each other. Thereby, the antenna balun array 20A in which a plurality of antenna baluns 20 are cascaded can be easily configured.

[0031] In FIG. 6, an example is shown in which each of the conductor 20-1 and the conductor 20-2 that make up the second-stage antenna balun 20 is rotated 180° in the horizontal direction (around the X-axis in FIG. 6) and connected, and further, each of the conductor 20-1 and the conductor 20-2 that make up the third-stage antenna balun 20 is rotated 180° in the horizontal direction and connected. And in FIG. 6, an example is shown in which the conductors of the first electrode CL-A of the conductor 20-1 that make up each of the first-stage and second-stage antenna baluns 20 are connected to each other, and the conductors of the second electrode CR-B of the conductor 20-2 that make up each of the first-stage and second-stage antenna baluns 20 are connected to each other. For this reason, in FIG. 6, the terminals of the portions where the conductors of the electrodes are connected to each other are omitted. That is, in FIG. 6, the conductors that make up each of the second-stage and third-stage antenna baluns 20 are inverted left and right, and the portions where the lengths of the conductors of the electrodes are extended are connected to each other (directly connected) to form an antenna balun array 20A in which the antenna balun 20 is cascaded in three stages. However, the connection method of each conductor when configuring the antenna balun array 20A is not limited to the example shown in FIG. 6. For example, without rotating the conductors of the second stage and the third stage, that is, the positions where the inductance elements are formed are the same for all three stages, they may be connected. In this case, they may be connected to each other by extending the length of the conductor at the portion where the conductors of the electrodes are connected to each other.

[0032] [Mounting Example of Antenna Array System] Next, a mounting example of the antenna array system 1 will be described. FIG. 7 is a diagram showing a mounting example of the antenna array system 1 according to the embodiment. FIG. 7 shows an example of the case where the antenna array system 1 is mounted on an artificial satellite AS which is a spacecraft. As described above, the antenna balun 20 can be miniaturized. For this reason, the antenna array system 1 can be attached (mounted) not only to the antenna array section AA of the artificial satellite AS but also to various locations. FIG. 7 schematically shows an example of the case where the antenna array system 1 is attached to each of the positions of the main body of the artificial satellite AS, the end of the solar panel paddle, and the end of the antenna of the Synthetic Aperture Radar (SAR).

[0033] Although FIG. 7 shows an example of the case where the antenna array system 1 is mounted on the artificial satellite AS, the antenna array system 1 can be mounted on various things such as spacecrafts and moving objects where there are many restrictions on antenna mounting, not only on the artificial satellite AS. The spacecraft may be an artificial satellite that orbits along a predetermined orbit over the surface of the earth, over the surface of other celestial bodies or objects, or a geostationary satellite targeted at a specific position, or an observation satellite that goes out to observe other celestial bodies or objects (and may return to the earth). Other celestial bodies include other planets different from the earth such as Mars and Venus, satellites such as the moon and Titan, and asteroids such as Itokawa and Ryugu. Other objects include rocks and the like. Instead of artificial satellites and observation satellites, the moving object may be, for example, another flying object such as an airplane or a drone.

[0034] [Modification Example of Configuration of Antenna Balun] In the structure of the antenna balun 20 shown in FIG. 2, the case is shown where, in each conductor, an electrode having a balun length L for forming a capacitive element is formed, and an inductive element is formed in a region up to half (L / 2) of the balun length L. However, the form of forming each of the capacitive element and the inductive element in each conductor constituting the antenna balun 20 is not limited to the form shown in FIG. 2. FIG. 8 is a diagram showing another example of the structure of the antenna balun 20 according to the embodiment. FIG. 8 shows two other examples of forming an inductive element in each conductor constituting the antenna balun 20.

[0035] In FIGS. 8(a-1) and (a-2), an example is shown in which the inductive element LL and the inductive element LR are formed in a region up to the balun length L of each capacitive element. More specifically, FIG. 8(a-1) shows a conductor 21-1, which is a modified example of the conductor 20-1, in which the inductive element LL is formed in a region up to the balun length L of the first electrode CL-A of the capacitive element CL and the first electrode CR-A of the capacitive element CR. On the other hand, FIG. 8(a-2) shows a conductor 21-2, which is a modified example of the conductor 20-2, in which the inductive element LR is formed in a region up to the balun length L of the second electrode CL-B of the capacitive element CL and the second electrode CR-B of the capacitive element CR.

[0036] In FIGS. 8(b-1) and (b-2), an example is shown in which the regions for forming the inductive element LL and the inductive element LR are the same as those of the antenna balun 20, but the conductive lines are formed in different directions. More specifically, FIG. 8(b-1) shows a conductor 22-1, which is a modified example of the conductor 20-1, in which the direction of the conductive line for forming the inductive element LL is made orthogonal to the direction of the balun length L of the first electrode CL-A of the capacitive element CL and the first electrode CR-A of the capacitive element CR. On the other hand, FIG. 8(b-2) shows a conductor 22-2, which is a modified example of the conductor 20-2, in which the direction of the conductive line for forming the inductive element LR is made orthogonal to the direction of the balun length L of the second electrode CL-B of the capacitive element CL and the second electrode CR-B of the capacitive element CR.

[0037] As described above, the form of forming each of the capacitor element and the inductor element in each of the conductors constituting the antenna balun 20 can be formed in any manner as long as it is within the range where the communication characteristics required for the antenna array system 1 can be realized by adjusting (optimizing) the capacitance value of the capacitor elements CL and CR and the inductance value of the inductor elements LL and LR. Therefore, in an example shown in FIGS. 2 and 8, the case where the antenna balun 20 is formed of two layers of conductors, the conductor 20-1 and the conductor 20-2, which form each of the capacitor element and the inductor element, is shown. However, the number of layers of the conductors forming the antenna balun 20 is not limited to two layers. For example, the antenna balun 20 may be formed of four layers of conductors. More specifically, a capacitor element may be formed in two layers facing each other with an insulator IS interposed therebetween, and an inductor element may be formed in each of the two outer layers facing the phases of the respective conductors with another insulator interposed therebetween. At this time, the layer of the conductor forming each capacitor element and the layer of the conductor forming the inductor element may be changed.

[0038] As described above, in the antenna balun 20 of the embodiment, an antenna balun using the circuit technology of the CRLH waveguide is realized without using individual electronic components. As a result, in the antenna array system 1 using the antenna balun 20 of the embodiment, even when used in a special environment such as an environment where a stable ground conductor cannot be obtained or an environment where interference objects exist around, it is possible to maintain a stable phase difference, perform efficient communication, and suppress external interference to the communication. Furthermore, the antenna array system 1 using the antenna balun 20 of the embodiment has many radiations, becomes very high temperature or very low temperature, and cannot be easily maintained (maintenance), that is, in an even more special environment such as outer space where long life is required, the same effect can be obtained, and since the antenna balun 20 of the embodiment does not use individual electronic components or special materials, long life can be realized. And since the antenna balun 20 of the embodiment can be miniaturized by using the circuit technology of the CRLH waveguide, it facilitates mounting on an artificial satellite AS or the like of the antenna array system 1 using the antenna balun 20 of the embodiment, and weight reduction can also be realized.

[0039] In the above-described embodiment, the case where the moving body is an artificial satellite that moves while orbiting on a predetermined orbit above the earth's surface has been described. However, the moving body may be a rocket that performs ballistic flight. When this rocket is a multi-stage rocket, for example, a mechanism for coupling and launching the upper stage (uppermost stage) of the rocket with an artificial satellite AS mounted, such as a satellite mounting section, and sending the artificial satellite AS onto a predetermined orbit can also be considered in the same way as orbiting above the earth's surface (including the case of a shorter time than the artificial satellite AS). And as an antenna array system that communicates with such a satellite mounting section, it is conceivable to use the antenna array system 1 using the antenna balun 20 of the embodiment.

[0040] As described above, the embodiments for carrying out the present invention have been described using embodiments, but the present invention is not limited to such embodiments at all, and various modifications and substitutions can be made without departing from the gist of the present invention.

Explanation of Signs

[0041] 1 ··· Antenna array system 10, 10a, 10b ··· Antenna 20 ··· Antenna balun 20A ··· Antenna balun array 20-1 ··· Conductor 20-2 ··· Conductor CL ··· Capacitive element CL-A ··· First electrode CL-B ··· Second electrode CR ··· Capacitive element CR-A ··· First electrode CR-B ··· Second electrode LL ··· Inductance element LR ··· Inductance element P1 ··· Terminal P2 ··· Terminal P3 ··· Terminal Z30 ··· Load impedance Z11 ··· Load impedance Z12 ··· Load impedance LH ··· Left-handed waveguide RH ··· Right-handed waveguide 30 ··· Feeding point AS ··· Artificial satellite (spacecraft) AA ··· Antenna array section

Claims

1. A first layer includes a first conductor having a first electrode of a first capacitive element, a first inductive element, and a first electrode of a second capacitive element; A second layer disposed opposite to the first layer includes a second conductor having a second electrode of the first capacitive element, a second inductive element, and a second electrode of the second capacitive element; An antenna balun comprising the above.

2. The first capacitive element is a capacitive element having a MIM (Metal-Insulator-Metal) structure with an insulator sandwiched between the first electrode of the first capacitive element and the second electrode of the first capacitive element; The second capacitive element is a capacitive element having a MIM structure with the insulator sandwiched between the first electrode of the second capacitive element and the second electrode of the second capacitive element; The first inductive element and the second inductive element are inductive elements having a meander line structure. The antenna balun according to Claim 1.

3. The first capacitive element and the first inductive element form a left-handed waveguide; The second capacitive element and the second inductive element form a right-handed waveguide; When the feeding positive and negative are reversed, the relationship is reversed; A left-handed waveguide is formed at the connection point of each antenna with respect to the right-handed waveguide formed by parallel lines. The antenna balun according to Claim 2.

4. The first capacitive element, the first inductive element, the second capacitive element, and the second inductive element form a frequency insensitive band. The antenna balun according to Claim 3.

5. An array section in which the antenna baluns according to any one of Claims 1 to 4 are connected in series in multiple stages; Comprising; An antenna array system using an antenna balun.

6. The first capacitive element, the first inductive element, the second capacitive element, and the second inductive element form either or both of a broadened frequency passband and an insensitive band. An antenna array system using the antenna balun according to Claim 5.

7. A plurality of the array sections are provided, and a balanced antenna is provided between each of the array sections. An antenna array system using the antenna balun according to Claim 5 or Claim 6.

8. Mounted on a moving body moving in the air An antenna array system using the antenna balun according to any one of claims 5 to 7.

9. The moving body is a satellite. An antenna array system using the antenna balun according to claim 8.

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