JP2017152781A - Non-reciprocal metamaterial transmission line device and antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-reciprocal metamaterial transmission line device capable of transmitting a high frequency signal in a wide band.SOLUTION: In non-reciprocal metamaterial transmission line device, propagation constants in a forward direction and an opposite direction are different each other, and at least one unit cell is connected in cascade between first and second ports. The unit cell includes: a transmission line part of a microwave signal; first and second circuits that is branched and provided from the transmission line part, and equivalently includes an inductive element; and a third parallel branch circuit that equivalently includes a capacitive element. At least one unit cell includes a spontaneous magnetization so as to be magnetized to a magnetization direction different from a transmission direction of the transmission line part, and has a gyroscope anisotropy, or is magnetized by an outer magnetic field. In at least one unit cell, the first parallel branch circuit is formed on one side to a surface formed by a transmission direction and a magnetization direction. The second parallel branch circuit is formed on the other side to the surface.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a nonreciprocal metamaterial transmission line device having a forward propagation constant and a reverse propagation constant different from each other, and an antenna device using the nonreciprocal metamaterial transmission line device.

  FIG. 1 is a block diagram showing a configuration of a leaky wave antenna apparatus according to a conventional example. One of the beam scanning antennas is a leaky wave antenna, and the leaky wave antenna is, as shown in FIG. 1, when the absolute value of the effective refractive index of the transmission line constituting the leaky wave antenna device is smaller than 1. A directional antenna using a phenomenon in which a part of a signal propagating along a transmission line radiates outside as a leaky wave. In FIG. 1, the transmission line has two line conductors 101 and 102, and has a first port P1 composed of terminals T1 and T2, and a second port P2 composed of terminals T3 and T4.

  Since the angle of the radiation beam 103 is determined by the phase constant β, which is a spatial phase gradient of the electromagnetic field distribution generated on the transmission line, as shown by the following equation, the leakage wave beam is changed by changing the phase gradient on the line. It becomes possible to scan the angle θ.

Here, β is a phase constant on the transmission line, β ₀ is a phase constant in free space, and the effective refractive index n _eff takes a value of −1 ≦ n _eff ≦ 1.

  Thus, in the leaky wave antenna of the conventional example, a high frequency signal is input from one end of the transmission line. When a part of the high-frequency signal reaches the end of the transmission line without contributing to the leakage wave radiation, it is reflected at the termination and propagates in the opposite direction on the same transmission line, and unnecessary side lobes are generated by the secondary leakage wave radiation. Will be generated. As means for solving this problem, it is necessary to unnecessarily increase the antenna size (line length) or insert an impedance matching circuit at the end of the transmission line to suppress reflection. If it is desired to reduce the size of the leaky wave antenna, signal components that do not contribute to radiation are consumed when they reach the end, and radiation efficiency does not increase.

  One of the new technologies for maintaining high radiation efficiency while keeping the antenna size compact is the use of nonreciprocal metamaterials. Non-reciprocal metamaterials are metamaterials with different transmission coefficients in the forward and reverse directions.For example, in the case of forward propagation, a positive refractive index is shown. Can be shown. When this nonreciprocal material line is applied to a leaky wave antenna, the leaky wave radiation direction can be directed in the same direction even if the propagation direction of the high-frequency signal is switched along the transmission line.

  In order not to reduce the radiation efficiency of leakage waves from this nonreciprocal transmission line, a large number of input high-frequency signals can be obtained by inserting a pair of reflecting elements at both ends of the transmission line and actively using multiple reflections. It is conceivable that the portion contributes to leakage wave radiation in a specific direction. In other words, in the prior art, the power that has been wasted at the end can be effectively utilized by using the nonreciprocal line, and the radiation efficiency can be improved by the resonance structure. Such a resonant structure of a nonreciprocal metamaterial transmission line is called a pseudo traveling wave resonator and has several features.

  The first feature is that the resonance frequency does not depend on the resonator size. When this is used, the antenna shape and size can be freely changed while the resonance frequency is fixed. Another feature is that the electromagnetic field distribution in the pseudo traveling wave resonator automatically becomes uniform in amplitude, while the phase distribution has a constant phase gradient. This phase gradient is an amount determined by the non-reciprocity of the transmission line, and is a parameter that can be controlled independently regardless of the resonance condition.

Therefore, highly efficient leakage wave beam scanning can be performed by changing the nonreciprocity of the transmission line while maintaining the resonance state. When there is no nonreciprocity in the transmission line, the effective refractive index n _eff in the transmission line is 0 and the phase is the same everywhere on the transmission line, so that the leaky wave in the broadside (vertical) direction with respect to the transmission line Radiates.

  When information is transmitted using a transmission line, a signal wave is a modulated wave and has a frequency spread. In order to transmit the modulated wave in the same direction, it is necessary to direct the beam in the same direction regardless of the frequency in a predetermined band. Therefore, the frequency dependence of the beam direction causes the beam direction to fluctuate and is called “beam squint”. In this manner, a beam scanning antenna that transmits and receives information in a predetermined band requires a technique for reducing beam squint.

  In a leaky wave antenna based on pseudo traveling wave resonance consisting of a nonreciprocal metamaterial transmission line, the nonreciprocity of the transmission line determines the beam angle, so beam squint, that is, fluctuations in the beam direction due to frequency changes, are transmitted. This is caused by the frequency dispersion of the nonreciprocal phase shift characteristics of the line. In other words, this corresponds to the frequency dispersion of the difference in refractive index between forward propagation and reverse propagation. Therefore, if the frequency dispersion of the effective refractive index difference due to the propagation direction of the nonreciprocal metamaterial transmission line is suppressed, the beam squint is reduced.

  So far, as a method of suppressing the beam squint of the pseudo traveling wave resonant antenna, there has been a proposal that employs a double stub structure in which stubs are inserted on both sides of the transmission line to suppress nonreciprocal frequency dispersion (for example, And Patent Documents 1 to 4). In this double stub structure, as the two inserted stubs, the shorter stub is an inductive stub for realizing a negative dielectric constant, and the other long stub is a frequency dispersion of the short stub. The higher-order inductive band was used to adjust the frequency.

Japanese Patent No. 5234667 Japanese Patent No. 5655256 International Publication No. 2012/115245 Japanese Patent Laying-Open No. 2015-181212

  However, since a long stub uses a high-order inductive region, it is set to take a singular point slightly on the lower side of the operating band, and there is a problem that the dispersibility of the line becomes strong. As a result, when a resonator is configured on the same line, the adjacent higher-order resonance mode (half-wave resonance) resonates more closely, and the band of the desired operation is narrowed under the influence. there were.

  The object of the present invention is to solve the above problems and provide a non-reciprocal metamaterial transmission line device capable of transmitting a high-frequency signal in a wide band compared to the prior art and an antenna device using the non-reciprocal metamaterial transmission line device. There is to do.

The nonreciprocal metamaterial transmission line device according to the first invention is a nonreciprocal metamaterial transmission line device in which a propagation constant in a forward direction and a propagation constant in a reverse direction are different from each other,
The nonreciprocal metamaterial transmission line device includes a transmission line portion of a microwave signal, a circuit of first and second parallel branches that are branched from the transmission line portion and equivalently include inductive elements. And at least one unit cell having a third parallel branch circuit equivalently including a capacitive element, and configured by cascading between the first and second ports,
Each of the at least one unit cell is magnetized in a magnetization direction different from the propagation direction of the transmission line portion and has a gyro anisotropy or is magnetized by an external magnetic field,
In each of the at least one unit cell, the circuit of the first parallel branch is formed on one side with respect to the plane formed by the propagation direction and the magnetization direction, The circuit is formed on the other side with respect to the surface.

  In the nonreciprocal metamaterial transmission line device, the impedance of the circuit of the first parallel branch viewed from the transmission line portion is the same inductive as the impedance of the circuit of the second parallel branch viewed from the transmission line portion. It is characterized by having an impedance of.

  In the nonreciprocal metamaterial transmission line device, the circuit parameters of the first to third parallel branches are adjusted to suppress beam squinting by reducing nonreciprocal dispersion. To do.

Furthermore, in the nonreciprocal metamaterial transmission line device, the circuit of the third parallel branch is:
(1) a capacitor formed between a pair of conductors;
(2) a capacitive stub line formed of a line conductor of a predetermined length;
(3) It includes any one of capacitor elements.

  Still further, in the nonreciprocal metamaterial transmission line device, the first and second parallel branch circuits are formed to be symmetric with respect to the center or the center line of the unit cell.

Still further, in the nonreciprocal metamaterial transmission line device, the circuits of the first and second parallel branches are respectively formed on one side with respect to a surface formed by (1) the propagation direction and the magnetization direction. One inductive stub and one inductive stub formed on the other side of the surface, or
(2) Two inductive stubs formed on one side with respect to the surface formed by the propagation direction and the magnetization direction, and two inductive stubs formed on the other side with respect to the surface It is characterized by comprising.

  Further, in the nonreciprocal metamaterial transmission line device, inductive stubs are equivalent by grounding the transmission line portion of the unit cell via via conductors instead of the first and second parallel branch circuits. It is characterized by being formed.

An antenna device according to a second invention is
The nonreciprocal metamaterial transmission line device;
A reflective element is inserted into each of the first and second ports to operate the nonreciprocal metamaterial transmission line device as a pseudo traveling wave resonator, and a microwave signal to be transmitted or received to the first port is input or It is characterized by outputting.

  Therefore, according to the nonreciprocal metamaterial transmission line device according to the present invention, it is possible to transmit a high-frequency signal in a wide band as compared with the prior art. In addition, according to the antenna device using the nonreciprocal metamaterial transmission line device according to the present invention, it is possible to transmit and receive high-frequency signals in a wider band than in the prior art.

It is a block diagram which shows the structure of the leaky wave antenna apparatus which concerns on a prior art example. It is a longitudinal cross-sectional view which shows the structure of the nonreciprocal metamaterial transmission line apparatus which concerns on a comparative example. It is a top view which shows the structure of the nonreciprocal metamaterial transmission line apparatus based on Embodiment 1. FIG. It is a graph which shows a dispersion curve when the magnetic field direction is set to the upper direction in the nonreciprocal metamaterial transmission line device of FIG. It is a graph which shows a dispersion | distribution curve when the magnetic field direction is set to the downward direction in the nonreciprocal metamaterial transmission line device of FIG. It is a top view which shows the structure of the pseudo traveling wave resonator antenna apparatus using the nonreciprocal metamaterial transmission line apparatus based on Embodiment 2. FIG. It is a graph which shows the reflective characteristic of the antenna apparatus of FIG. It is a graph which shows the frequency dependence of the beam angle of the antenna apparatus of FIG. It is a graph which shows the beam scanning characteristic when the applied magnetic field is changed in the antenna apparatus of FIG. It is a top view which shows the structure of the nonreciprocal metamaterial transmission line apparatus which concerns on the modification 1. FIG. It is a top view which shows the structure of the nonreciprocal metamaterial transmission line apparatus which concerns on the modification 2. FIG. It is a top view which shows the structure of the nonreciprocal metamaterial transmission line apparatus which concerns on the modification 3. FIG. It is a longitudinal cross-sectional view about the A-A 'line | wire of FIG. 11A. It is a top view which shows the structure of the nonreciprocal metamaterial transmission line apparatus which concerns on the modification 4. 10 is a plan view showing a configuration of a nonreciprocal metamaterial transmission line device according to Modification 5. FIG.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each following embodiment, the same code | symbol is attached | subjected about the same component.

FIG. 2 is a longitudinal sectional view showing a configuration of a nonreciprocal metamaterial transmission line device according to a comparative example. In FIG. 2, for example, a rectangular parallelepiped ferrite square bar 10 is sandwiched between a pair of dielectric substrates 13 and 14 having a thickness d having a ground conductor 11 on the back surface, and a line conductor is formed on the ferrite square bar 10. A strip conductor 12 having a width w is formed. Here, for example, using the permanent magnet 40, the magnetic field _Mef is applied to the ferrite square bar 10 in the upward direction (referred to as a direction perpendicular to the substrate surface from the ground conductor 11 toward the strip conductor 12). When applied, the ferrite square bar 10 is magnetized. In the transmission line device configured as described above, the strip conductor 12 and the ground conductor 11 constitute a microstrip line.

  The nonreciprocal phase shift of the right / left-handed composite transmission line breaks the space reversal symmetry with the use of a ferromagnetic, ferrimagnetic (ferrite square bar 10 in FIG. 2) or artificial structure that breaks the time reversal symmetry. This occurs in combination with the asymmetry of the waveguide structure. As a specific example, the electromagnetic field distribution of the edge guide mode propagating along the perpendicular magnetization microstrip line is distributed asymmetrically on one side of the strip edge on the transverse cross section perpendicular to the propagation direction, and the polarized side propagates. It has the property of switching in direction. On the other hand, when a stub is inserted asymmetrically with respect to both side surfaces of the central microstrip line in order to give asymmetry to the waveguide structure, the electromagnetic wave feels different waveguide structures depending on how the propagation direction is selected. Therefore, nonreciprocity appears. At this time, the nonreciprocal phase shift characteristic is given by the following equation.

  However, Δβ represents an average value of the phase constants βp and βm in the forward direction and the reverse direction. If the forward and reverse phase constants are equal, Δβ is zero.

As shown in FIG. 2, the variables B ₁ and B _{2 in the} expression (2) are the values on the left and right side surfaces of the ferrite square bar 10 that is a magnetic material in the perpendicular magnetization microstrip line toward the propagation direction. is that the admittance _{Y 1} and _{Y 2} of the imaginary part susceptance. Since the variable p is the length of the unit cell and l _NR is the length of the line portion occupied by the asymmetric structure portion, l _NR / p represents the ratio of the nonreciprocal line portion in the unit cell length. Furthermore, the angular frequency ω _{m =} γμ _{0 M S} is related to the magnitude of the off-diagonal components of the permeability tensor, represented by a vertical magnetization M _S and the gyromagnetic ratio of the ferrite rectangular bar 10 gamma, time-reversal symmetry Represents the size of the tear. On the other hand, the factor (B ₁ -B ₂ ) is the difference between the susceptances B ₁ and B ₂ of the two inserted stubs, and represents the asymmetry of the waveguide structure, that is, the breaking of the space inversion symmetry.

In the right-hand / left-handed composite transmission line structure composed of the perpendicular magnetization microstrip line according to the comparative example of FIG. 2, the susceptance of the inductive stub L inserted to obtain a negative dielectric constant is −1 / ωL. The fact that the non-reciprocity seen when inserting this inductive stub from one direction is proportional to the reciprocal of the operating frequency is a well-known fact in non-reciprocal right / left-handed composite transmission lines, If B ₁ = 0 and B ₂ = −1 / ωL using the formula (2), the explanation can be made easily.

Assuming that equation (1) is approximately established, in order to make the frequency dispersion of the nonreciprocal phase shift characteristic zero, (B ₁ -B ₂ ) may be directly proportional to the frequency. Such a combination of susceptances B ₁ and B ₂ can be easily configured by using a capacitive element. For example, in FIG. 2, if a capacitive stub C is inserted only on the right side, B ₁ = 0 and B ₂ = ωC, so that non-reciprocity proportional to the operating frequency can be expected. However, on the other hand, in order to construct a right-hand / left-handed composite transmission line, it is difficult to develop a negative dielectric constant with only an inductive stub, and insertion of the inductive stub is indispensable.

  Embodiments according to the present invention employ asymmetric insertion of capacitive stubs for nonreciprocity, while inductive stubs are nonreciprocal to achieve a negative dielectric constant. It is proposed to insert symmetrically from both sides of the microstrip line so that it does not contribute to.

Embodiment 1. FIG.
FIG. 3 is a plan view showing the configuration of the nonreciprocal metamaterial transmission line device according to the first embodiment. Embodiment 1 shows a proposed right-hand / left-handed composite transmission line in which the frequency dispersion of the proposed nonreciprocal phase shift characteristic is zero. In FIG. 3, a perpendicularly magnetized ferrite square bar 10 (for example, directly below a metal strip conductor 12 of a microstrip line in which a plurality of unit cells 20 each composed of a ground conductor (for example, 11 in FIG. 2) and a strip conductor 12 are connected in cascade. In contrast to the structure in which the magnetic field is applied by the permanent magnet 40 in FIG. 2, a capacitor Cs (however, the capacitor 2Cs at the ports P1 and P2 at both ends) is inserted in the series branch of the unit cell 20, and the strip conductor. On one side of 12 (referring to one side perpendicular to the longitudinal direction of the line, the lower side of FIG. 3), a stub conductor 17 (dielectric substrate 14 is interposed) via a strip conductor 16 to form a capacitive stub. The stub conductor 17 and the ground conductor 11 form a capacitor, and both sides of the strip conductor 12 (the one perpendicular to the longitudinal direction of the line) On both sides of the (horizontal plane) (hereinafter referred to as both sides), the top and bottom sides in FIG. A pair of stub conductors 15a and 15b are inserted. Here, the stub conductor 15a is formed at the end closer to the second port P2 on both sides of the strip conductor 12, and the stub conductor 15b is at the end closer to the first port P1 on both sides of the strip conductor 12. It is formed.

  Further, of the first port P1 and the second port P2 at both ends of the transmission line, a strip conductor 12P1 is formed on the dielectric substrates 13 and 14 for the first port P1, and the second port P2 Therefore, the strip conductor 12P2 is formed on the dielectric substrates 13 and 14.

  In the above embodiment, the ferrite square bar 10 is magnetized in the vertical direction by the permanent magnet 40 (FIG. 2) provided immediately below the line. However, the present invention is not limited to this, and the ferrite square bar 10 is magnetized in advance. May be.

  The ladder-type nonreciprocal right / left-handed transmission line, which is the nonreciprocal metamaterial transmission line, has a ladder-type transmission line structure in which, for example, as shown in FIG. It is. Here, the configuration of the unit cell 20 includes a transmission line portion having a nonreciprocal phase transition phenomenon having different propagation constants in the forward direction and the reverse direction, a capacitive element in a series branch circuit, and an inductive element in a parallel branch circuit. Are equivalently inserted (see FIG. 2). Circuits or devices targeted as the above transmission line configurations include printed circuit boards, waveguides, dielectrics used in microwaves, millimeter waves, quasi-millimeter waves, terahertz waves, such as strip lines, microstrip lines, slot lines, and coplanar lines. This includes not only body lines but also all configurations that support guided modes or attenuation modes including plasmons, polaritons, magnons, etc., or combinations thereof, and free space that can be described as an equivalent circuit.

  The transmission line having the irreversible phase transition phenomenon includes a material having gyro anisotropy in part or in whole in the transmission line configuration shown above, and a magnetization direction (different from the propagation direction of electromagnetic waves) More preferably, the transmission line is composed of a transmission line that is magnetized in a direction orthogonal to the propagation direction and has an asymmetry with respect to a plane formed by the propagation direction and the magnetization direction. As the transmission line having the nonreciprocal phase transition phenomenon, in addition to the transmission line, a lumped constant element having an equivalent nonreciprocal phase transition function and sufficiently smaller than the wavelength is also targeted. As the material having the above gyro anisotropy, a dielectric constant tensor or a magnetic permeability tensor representing the characteristics of the material by spontaneous magnetization, magnetization induced by a direct-current or low-frequency magnetic field applied from the outside, or circular motion of free charge, or Both include all cases expressed as states having gyro anisotropy. Specific examples include ferrimagnetic materials such as ferrite used in microwaves and millimeter waves, ferromagnetic materials, solid plasmas (semiconductor materials, etc.) and liquids, gas plasma media, and microfabrication. Examples include magnetic artificial media that are configured.

  Capacitive elements inserted in the above-mentioned series branch circuit include not only distributed constant type capacitive elements used in capacitors, microwaves, millimeter wave circuits, etc. often used in electric circuits, but equivalently, in transmission lines It may be a circuit or a circuit element in which the effective permeability of the electromagnetic wave mode propagating through the channel has a negative value. Specific examples of negative effective permeability include a split ring resonator made of metal, a spatial arrangement including at least one magnetic resonator such as a spiral configuration, or a dielectric resonator in a magnetic resonance state All microwave circuits operating in the waveguide mode or attenuation mode with negative effective magnetic permeability, such as the edge mode propagating along the ferrite substrate microstrip line, as an equivalent circuit It can be used because the circuit is described as a line that operates predominantly as a capacitive element. In addition to the above, the capacitive element inserted into the series branch circuit may be a series connection, a parallel connection, or a combination of a capacitive element and an inductive element. The element or circuit of the part to be inserted may be capacitive as a whole.

  As an inductive element inserted into the above-mentioned parallel branch circuit, only a lumped constant type element such as a coil used in an electric circuit or a distributed constant type inductive element such as a short-circuit stub used in a microwave or millimeter wave circuit is used. Alternatively, a circuit or element having a negative effective dielectric constant of the electromagnetic wave mode propagating through the transmission line can be used. Specifically, a spatial arrangement including at least one electric resonator such as a thin metal wire or a metal sphere, or a spatial arrangement of a dielectric resonator in an electric resonance state as well as a metal, or a TE mode is cut off. Transmission in which the parallel branch is dominantly operated as an inductive element as an equivalent circuit for all microwave circuits operating in the waveguide mode or attenuation mode having a negative effective dielectric constant, such as waveguides and parallel plate lines in the region It can be used because it is described as a track. In addition to the above, the inductive element inserted into the parallel branch circuit may be a series connection, a parallel connection, or a combination of a capacitive element and an inductive element. The part to be inserted may be a circuit or an element that exhibits inductivity as a whole.

FIG. 4A is a graph showing a dispersion curve when the magnetic field direction is set upward (referred to as a direction from the ground conductor 11 to the strip conductor 12) in the nonreciprocal metamaterial transmission line device of FIG. FIG. 4B is a graph showing a dispersion curve when the magnetic field direction is set downward (referred to as a direction from the strip conductor 12 to the ground conductor 11) in the nonreciprocal metamaterial transmission line device of FIG. The present inventors perform simulation of the nonreciprocal metamaterial transmission line device (also referred to as nonreciprocal composite right / left handed transmission line device) of FIG. 3 by electromagnetic field simulation, and the effective magnetization is γμ ₀ Mef = 170 mT. FIG. 4A and FIG. 4B show dispersion curves and nonreciprocal phase shift characteristics obtained from the transmission characteristics of FIG.

  However, in FIGS. 4A and 4B, the case of inputting from the first port P1 in FIG. 3 as the positive direction of the flow of the high-frequency signal power is selected. FIGS. 4A and 4B also show the measurement results when a circuit having the same structural parameters as the simulation is prototyped and an external DC magnetic field of 135 mT is applied using the permanent magnet 40. The result when the vertically upward direction facing the direction opposite to the ground plane with respect to the dielectric substrates 13 and 14 and the ferrite square bar 10 is selected as the positive direction of the applied magnetic field, and the magnetization and magnetic field directions are set to the positive direction. 4A is shown in FIG. 4A and is taken in the negative direction.

  In FIGS. 4A and 4B, a one-dot chain line that passes through the origin is drawn. This is a case of nonreciprocal phase shift characteristics without frequency dispersion, and is also a condition that the beam squint becomes zero. As is clear from FIG. 4, it can be seen that the dispersion curves of the circuits that were manufactured by making a trial production are in good agreement with the characteristics of the line in which the beam squint is almost zero.

  According to the non-reciprocal metamaterial transmission line device according to the present embodiment, the non-reciprocal metamaterial transmission line device having a forward propagation constant and a reverse propagation constant different from each other, Are a first transmission line portion of a microwave signal (a microstrip line formed by the strip conductor 12 and the ground conductor 11), and a first and a second portion that are provided separately from the transmission line portion and that include equivalent inductive elements. At least one unit cell having a parallel branch circuit (inductive stub with stub conductors 15a and 15b) and a third parallel branch circuit (capacitive stub with stub conductor 17) equivalently including a capacitive element. 20 is connected in cascade between the first and second ports P1, P2. Here, each of the at least one unit cell 20 is magnetized in a magnetization direction different from the propagation direction of the transmission line portion and has a gyro anisotropy or is magnetized by an external magnetic field, In each of the at least one unit cell 20, the circuit of the first parallel branch is formed on one side with respect to the plane formed by the propagation direction and the magnetization direction, and the second parallel branch This circuit is formed on the other side of the surface.

  Here, preferably, the impedance of the circuit of the first parallel branch viewed from the transmission line portion is set to the same inductive impedance as the impedance of the circuit of the second parallel branch viewed from the transmission line portion. Is done. Moreover, it is preferable that the parameters of the circuits of the first to third parallel branches are adjusted so as to suppress beam squint.

  As described above, according to the present embodiment, the non-reciprocal dispersion can be easily reduced by the line structure of the first embodiment, and the non-reciprocal frequency dispersion band can be widened. Can be transmitted. Further, as described above, the beam squint can be greatly reduced as compared with the prior art. Thereby, in the beam scanning antenna, the problem that the beam direction fluctuates with the change of the operating frequency can be solved.

Embodiment 2. FIG.
FIG. 5 is a plan view showing a configuration of a pseudo traveling wave resonator antenna device using a nonreciprocal metamaterial transmission line device according to the second embodiment. In the second embodiment, a reflection element is inserted so that both ends of the nonreciprocal metamaterial transmission line device according to the first embodiment are short-circuited, and a 50Ω feeder is directly connected to one reflection element at a position where impedance matching can be obtained. By connecting, an antenna device using a pseudo traveling wave resonator is configured. Specifically, the following points are different from the non-reciprocal metamaterial transmission line device of FIG.
(1) A strip conductor 21 having a line length of λg / 4 and having an open end at the line end P1E is connected to the first port P1 on the dielectric substrate 18, and the strip conductor 21 supplies 50Ω. A feeder line strip conductor 22 connected at a position where impedance matching can be obtained by an electric wire was formed on the dielectric substrate 18. The strip conductors 21 and 22 constitute a line conductor of a microstrip line.
(2) In the second port P2, a strip conductor 23 is formed on the dielectric substrate 19 so as to be a short-circuited end at the line end P2E. The line end P2E is grounded to the ground conductor 11 via a via conductor penetrating in the thickness direction.
(3) The width of the strip conductor 16 is made the same as the width of the stub conductor 17, so that the strip conductor 16 becomes a capacitive stub with respect to the ground conductor 11, and the capacitance value can be increased as compared with the first embodiment.

  FIG. 6 is a graph showing the reflection characteristics of the antenna apparatus of FIG. 5 when the number of unit cells is 10. As is clear from FIG. 6, the notch portion where the reflection is reduced corresponds to each resonance mode, and the present inventors have found that the desired resonance operation related to the present embodiment has a frequency of 5.76 GHz. It was confirmed from the state of the electromagnetic field distribution obtained from the electromagnetic field simulation that it corresponds to the case.

  FIG. 7 is a graph showing the frequency dependence of the beam angle of the antenna apparatus of FIG. 5 when the number of unit cells is 10 and 20. As is apparent from FIG. 7, when a radiated beam is formed using the pseudo traveling wave resonator antenna device composed of the nonreciprocal metamaterial transmission line device proposed in this embodiment, the change in the beam direction accompanying the change in frequency, that is, It can be seen that the beam squint is greatly reduced. However, the beam squint is not completely zero, and a slight upward slope remains. If the influence of this slight phase gradient is allowed, the ratio band from 5.4 GHz to 5.9 GHz is about 8.5% in the case of the 10-cell structure, and from 5.5 GHz in the case of the 20-cell structure. It can be confirmed that the beam squint reduction technology is functioning in the region of about 6% of the specific bandwidth up to 5.8 GHz.

FIG. 8 is a graph showing the beam scanning characteristics when the applied magnetic field is changed in the antenna apparatus of FIG. FIG. 8 shows the numerical calculation results of the change in beam angle and the frequency dependence when the applied magnetic field to the antenna device is changed. Although there is a large variation in the center frequency of operation between the case where no DC magnetic field is applied and the case where the DC magnetization is applied and the effective magnetization is γμ ₀ M _ef = 170 mT, the frequency still varies from 5.5 GHz to 5.75 GHz. It can be seen that the beam can be continuously scanned from −8 ° to 10 ° in a state where the beam squint is greatly reduced over a specific bandwidth of about 5%.

  As described above, according to the present embodiment, a pseudo traveling wave resonator is configured by inserting reflective elements at both ends of the nonreciprocal metamaterial transmission line device according to the first embodiment, and a microwave signal is transmitted to this. An antenna device can be configured to input and transmit or receive and output a microwave signal. The antenna device can transmit and receive a broadband microwave signal compared to the prior art, and can significantly reduce the beam squint compared to the prior art.

Modified example.
In the following, modifications of the first embodiment will be described, but each modification can constitute an antenna device as in the second embodiment.

  FIG. 9 is a plan view showing the configuration of the nonreciprocal metamaterial transmission line device according to the first modification. As shown in FIG. 9, the nonreciprocal metamaterial transmission line device according to Modification 1 does not form the strip conductor 16 and has an open end compared to the nonreciprocal metamaterial transmission line device according to the first embodiment. In addition, a capacitive stub is formed by a strip conductor 16A as a distributed constant circuit which has a capacitance with a predetermined line length.

  FIG. 10 is a plan view showing a configuration of a nonreciprocal metamaterial transmission line device according to Modification 2. As shown in FIG. 10, the nonreciprocal metamaterial transmission line device according to the modified example 2 is replaced with a capacitive stub conductor 17 as a distributed constant circuit as compared with the nonreciprocal metamaterial transmission line device according to the modified example 1. Thus, the chip capacitor C17 whose end is grounded is connected to the ground conductor 11 via a via conductor penetrating in the thickness direction.

  FIG. 11A is a plan view showing a configuration of a nonreciprocal metamaterial transmission line device according to Modification 3, and FIG. 11B is a longitudinal sectional view taken along line A-A ′ of FIG. 11A. 11A and 11B, the nonreciprocal metamaterial transmission line device according to the modified example 3 is formed of only the stub conductor 17 as compared with the nonreciprocal metamaterial transmission line device according to the first embodiment. It is characterized in that the center of the strip conductor 12 constituting the conductor is grounded to the ground conductor 11 via a via conductor 41 penetrating in the thickness direction. Instead of the stub conductors 15a and 15b in FIG. 3, an inductive stub circuit is configured by grounding the via conductor 41. Modification 3 shows an example of an inductive shunt branch insertion method that suppresses the influence on nonreciprocity. By inserting a via conductor 41 in the center of a strip conductor 12 that is a line conductor, FIG. Although a large inductance cannot be obtained like the stub conductors 15a and 15b, non-reciprocity is not affected.

  FIG. 12 is a plan view showing a configuration of a nonreciprocal metamaterial transmission line device according to Modification 4. As shown in FIG. 12, the nonreciprocal metamaterial transmission line device according to the modified example 4 includes a stub in addition to the inductive stub conductors 15a and 15b as compared with the nonreciprocal metamaterial transmission line device according to the first embodiment. Conductors 15c and 15d are inserted. The stub conductor 15c is formed at an end portion closer to the first port P1 on both sides of the strip conductor 12, and the stub conductor 15d is formed at an end portion closer to the second port P2 on both sides of the strip conductor 12. . The inductive stub conductors 15a to 15d in the fourth modification are inductive parallel branches so as to be line-symmetric with respect to the center line of the strip conductor 12 constituting the line conductor (referred to as the center line in the width direction of the line). It is an example in which a circuit is inserted.

  FIG. 13 is a plan view showing a configuration of a nonreciprocal metamaterial transmission line device according to Modification 5. As shown in FIG. 13, the nonreciprocal metamaterial transmission line device according to Modification 5 is characterized in that only the stub conductors 15 c and 15 b among the four stub conductors 15 a to 15 d of Modification 4 are formed. The inductive stub conductors 15c and 15b in the modified example 5 are inductive parallel branches so as to be line symmetric with respect to the center line of the strip conductor 12 constituting the line conductor (referred to as the center line in the width direction of the line). It is an example in which a circuit is inserted.

  As described above, the antenna device may be configured by replacing the portion of the nonreciprocal metamaterial transmission line device of the second embodiment with the first to fifth modifications.

  As described above in detail, according to the nonreciprocal metamaterial transmission line device according to the present invention, it is possible to transmit a high-frequency signal in a wide band as compared with the prior art. In addition, according to the antenna device using the nonreciprocal metamaterial transmission line device according to the present invention, it is possible to transmit and receive high-frequency signals in a wide band as compared with the prior art, and to significantly reduce the beam squint compared to the prior art. .

10 ... Ferrite square bar,
11: Ground conductor,
12, 12P1, 12P2 ... strip conductors,
13, 14 ... dielectric substrate,
15a, 15b, 15c, 15d ... stub conductors,
16, 16A ... strip conductors,
17 ... Stub conductor,
18, 19 ... dielectric substrate,
20: Unit cell,
21, 22 ... strip conductors,
40 ... Permanent magnet,
41 ... via conductor,
C17: chip capacitor,
Cs: Series capacitor,
P1-P3 ... port
P1E, P2E: Line ends.

Claims (8)

A non-reciprocal metamaterial transmission line device in which the propagation constant in the forward direction and the propagation constant in the reverse direction are different from each other,
The nonreciprocal metamaterial transmission line device includes a transmission line portion of a microwave signal, a circuit of first and second parallel branches that are branched from the transmission line portion and equivalently include inductive elements. And at least one unit cell having a third parallel branch circuit equivalently including a capacitive element, and configured by cascading between the first and second ports,
Each of the at least one unit cell is magnetized in a magnetization direction different from the propagation direction of the transmission line portion and has a gyro anisotropy or is magnetized by an external magnetic field,
In each of the at least one unit cell, the circuit of the first parallel branch is formed on one side with respect to the plane formed by the propagation direction and the magnetization direction, A nonreciprocal metamaterial transmission line device, wherein the circuit is formed on the other side with respect to the surface.   The impedance of the circuit of the first parallel branch viewed from the transmission line portion is the same inductive impedance as the impedance of the circuit of the second parallel branch viewed from the transmission line portion. Item 2. The nonreciprocal metamaterial transmission line device according to Item 1.   The nonreciprocal metamaterial according to claim 1 or 2, wherein the parameters of the circuits of the first to third parallel branches are adjusted so as to suppress beam squinting by reducing nonreciprocal dispersion. Transmission line device. The circuit of the third parallel branch is
(1) a capacitor formed between a pair of conductors;
(2) a capacitive stub line formed of a line conductor of a predetermined length;
(3) The nonreciprocal metamaterial transmission line device according to any one of claims 1 to 3, wherein the non-reciprocal metamaterial transmission line device includes any one of capacitor elements.   5. The circuit according to claim 1, wherein the circuits of the first and second parallel branches are formed to be symmetric with respect to a center or a center line of the unit cell. Non-reciprocal metamaterial transmission line device. The circuits of the first and second parallel branches are respectively (1) one inductive stub formed on one side with respect to the surface formed by the propagation direction and the magnetization direction, and the surface And one inductive stub formed on the other side, or
(2) Two inductive stubs formed on one side with respect to the surface formed by the propagation direction and the magnetization direction, and two inductive stubs formed on the other side with respect to the surface The non-reciprocal metamaterial transmission line device according to claim 5, wherein   2. An inductive stub is equivalently formed by grounding a transmission line portion of the unit cell via a via conductor instead of the circuit of the first and second parallel branches. The nonreciprocal metamaterial transmission line device according to any one of? The nonreciprocal metamaterial transmission line device according to any one of claims 1 to 7,
A reflective element is inserted into each of the first and second ports to operate the nonreciprocal metamaterial transmission line device as a pseudo traveling wave resonator, and a microwave signal to be transmitted or received to the first port is input or An antenna device characterized by output.

Images