Radio wave radiator

Abstract

Provided is a radio wave radiator comprising: a waveguide; a radiation structure that radiates radio waves; and a modulation part that modulates the radiated radio waves. A plurality of the radiation structures are arranged at intervals of 1 / 2 or less of a free space wavelength corresponding to an operation frequency. The modulation part includes a material having a sheet resistance that changes depending on the voltage. A radiation pattern changes according to the change in the sheet resistance by an applied voltage. The material having a sheet resistance that changes depending on the voltage has a sheet resistance minimum value RsL of 10,000 Ω / Sq or less at 25℃ at an applied voltage of -40 V to 40 V.

Description

Radio wave emitter

[0001] The present disclosure relates to radio wave emitters.

[0002] In recent years, there has been a growing expectation for the realization of high-speed wireless communications using radio waves in high-frequency bands such as millimeter waves. While high-frequency radio waves have the advantage of being able to use a wide bandwidth, they suffer from the problem of large radio wave loss when propagating through space. To overcome this problem, beamforming technology is required, which concentrates and radiates radio wave energy in the direction of the receiving terminal. A common beamforming technology is the phased array antenna. A phased array antenna arranges multiple antenna elements in a regular pattern and controls the directionality of radio waves by adjusting the phase of each antenna element. However, in high-frequency bands, there are problems such as large transmission loss in the transmission path and difficulty in controlling the phase of each element.

[0003] For example, U.S. Patent No. 6,277,949 describes an antenna including a wave-propagating structure and a plurality of scattering elements arranged along the wave-propagating structure, the scattering elements having inter-element spacing substantially less than a free-space wavelength corresponding to an operating frequency of the antenna, the scattering elements having a plurality of independently varying electromagnetic responses to guided wave or surface wave modes of the wave-propagating structure, the independently varying electromagnetic responses providing a varying radiation field for the antenna.

[0004] A holographic antenna with a wave propagation structure and multiple scattering elements has been proposed as a new beamforming technology that can be applied to high-frequency radio waves. However, because it relies on voltage driving of liquid crystals, it has a problem of being usable in a narrow temperature range.

[0005] The problem to be solved by one embodiment of the present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a radio wave emitter with low temperature dependency.

[0006] The present disclosure includes the following aspects: <1> A waveguide, a radiation structure that radiates radio waves, and a modulation section that modulates the radiated radio waves, wherein a plurality of the radiation structures are arranged at intervals of equal to or less than half of a free space wavelength corresponding to an operating frequency, wherein the modulation section includes a material whose sheet resistance changes with voltage, wherein the radiation pattern changes in accordance with the change in sheet resistance due to an applied voltage, and wherein the material whose sheet resistance changes with voltage has a minimum sheet resistance Rs at 25°C when an applied voltage of -40V to 40V is applied. Ｌ <2> The material whose sheet resistance changes with voltage has a maximum value Rs of sheet resistance at 25°C when an applied voltage of -40V to 40V is applied. Ｈ Rs Ｌ <3> The radio wave emitter according to <1>, wherein the material whose sheet resistance changes with voltage has a sheet resistance at 25°C of Rs １ and the sheet resistance at 80°C is Rs ２ In this case, Rs ２ / Rs １ <4> The radio wave emitter according to <1> or <2>, wherein the material whose sheet resistance changes with voltage has a sheet resistance at 25°C of Rs １ The sheet resistance at 25°C after heating at 200°C for 1 hour was Rs ３ In this case, Rs ３ / Rs １<5> The radio wave emitter according to any one of <1> to <4>, wherein the material whose sheet resistance changes with voltage is graphene. <6> The radio wave emitter according to any one of <1> to <5>, wherein the waveguide is a metal waveguide, and the radiation structure is a slot formed in the metal waveguide. <7> The radio wave emitter according to any one of <1> to <5>, wherein the waveguide has a ground electrode, a dielectric layer, and a strip conductor in this order, and a metal microstructure is provided on the strip conductor as the radiation structure, and the waveguide, the metal microstructure, and the modulation unit are arranged in this order. <8> The radio wave emitter according to any one of <1> to <5>, wherein the waveguide has a ground electrode, a dielectric layer, and a strip conductor in this order, and the radiation structure is a slot formed in the ground electrode. <9> The radio wave emitter according to any one of <1> to <5>, wherein the waveguide has a pair of metal plates and a strip dielectric sandwiched between the pair of metal plates, and the radiation structure is a slot formed in one of the pair of metal plates. <10> The radio wave emitter according to <6>, <8>, or <9>, further comprising a metal microstructure as the radiation structure, wherein the waveguide, the metal microstructure, and the modulation section are arranged in this order. <11> The radio wave emitter according to any one of <1> to <10>, wherein there are a plurality of modulation sections, and the voltages applied to the plurality of modulation sections are controlled independently. <12> The radio wave emitter according to any one of <1> to <11>, wherein the modulation section includes a substrate, an insulating layer, and a layer containing a material whose sheet resistance changes depending on the voltage. <13> The radio wave emitter according to <12>, wherein the volume resistivity of the substrate is 10 Ω cm to 50 kΩ cm. <14> The radio wave emitter according to <12> or <13>, wherein the insulating layer has a thickness of 200 nm or less.

[0007] According to one embodiment of the present invention, a radio wave emitter with low temperature dependency is provided.

[0008] FIG. 1 is a cross-sectional view showing the configuration of one embodiment of a radio wave emitter according to the present disclosure. FIG. 2 is a cross-sectional view showing the configuration of another embodiment of a radio wave emitter according to the present disclosure. FIG. 3 is a cross-sectional view showing the configuration of another embodiment of a radio wave emitter according to the present disclosure. FIG. 4 is a cross-sectional view showing the configuration of another embodiment of a radio wave emitter according to the present disclosure. FIG. 5 is a cross-sectional view showing the configuration of another embodiment of a radio wave emitter according to the present disclosure. FIG. 6 is a schematic cross-sectional view of a waveguide used in Example 1. FIG. 7 is a schematic cross-sectional view of a modulation section used in Example 1. FIG. 8 shows a radiation pattern under condition 1 of Example 1. FIG. 9 shows a radiation pattern under condition 2 of Example 1. FIG. 10 shows a radiation pattern under condition 3 of Example 1. FIG. 11 shows a radiation pattern of Comparative Example 1. FIG. 12 shows a radiation pattern at 25°C of Comparative Example 2. FIG. 13 shows a radiation pattern at 80°C of Comparative Example 2.

[0009] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples. The elements in the drawings shown in the present disclosure are not necessarily drawn to scale, and emphasis is placed on clearly illustrating the principles of the present disclosure, with emphasis being placed on certain parts.

[0010] [Radio wave emitter] The radio wave emitter according to the present disclosure includes a waveguide, a radiation structure that emits radio waves, and a modulation section that modulates the radiated radio waves, wherein a plurality of the radiation structures are arranged at intervals of equal to or less than half of a free space wavelength corresponding to an operating frequency, the modulation section includes a material whose sheet resistance changes with voltage, and the radiation pattern changes as the sheet resistance changes with the applied voltage, and the material whose sheet resistance changes with voltage has a minimum sheet resistance Rs at 25°C when an applied voltage of -40V to 40V is applied. Ｌ is 10,000 Ω / □ or less.

[0011] The radio wave emitter according to the present disclosure includes a waveguide, a radiation structure for emitting radio waves, and a modulation section for modulating the radiated radio waves, wherein a plurality of radiation structures are arranged at intervals of not more than half the free space wavelength corresponding to the operating frequency, and the modulation section includes a material whose sheet resistance changes with voltage, thereby modulating the intensity of the radio waves radiated from the radiation structure and controlling the directionality of the radio waves. By using a material whose sheet resistance changes with voltage, it is possible to obtain the effect of low temperature dependency. Furthermore, the material whose sheet resistance changes with voltage has a minimum sheet resistance Rs at 25°C when an applied voltage of -40V to 40V is used. Ｌ Since the sheet resistance is 10,000 Ω / □ or less, the radiation pattern changes significantly as the sheet resistance changes due to the applied voltage.

[0012] On the other hand, JP-A No. 2013-539949 does not mention materials whose sheet resistance changes depending on voltage.

[0013] <Waveguide> The radio wave emitter according to the present disclosure includes a waveguide. The waveguide is not particularly limited as long as it has the function of propagating radio waves from one point to another.

[0014] Examples of the waveguide include a metal waveguide, a planar waveguide, and a dielectric waveguide. The metal waveguide may be a rectangular waveguide having a rectangular cross section, or a circular waveguide having a circular cross section. The metal constituting the metal waveguide is not particularly limited, and examples thereof include silver, copper, aluminum, and brass. The metal waveguide may also be one in which a metal film is coated on the surface of a resin.

[0015] Examples of planar waveguides include a microstrip line, a strip line, a slot line, a coplanar line, a suspended line, an inverted suspended line, and an inverted microstrip line.

[0016] An example of the dielectric waveguide is a non-radiative dielectric waveguide (NRD).

[0017] <Radiation Structure> The radio wave emitter according to the present disclosure includes a radiation structure that radiates radio waves. The radiation structure may have any structure that can radiate radio waves, and the specific structure is not particularly limited.

[0018] For example, if the waveguide is a metal waveguide, the radiating structure is preferably a slot formed in the metal waveguide.

[0019] For example, when the waveguide is a strip line having a ground electrode, a dielectric layer, and a strip conductor in this order, it is preferable that a metal microstructure is provided as a radiation structure on the strip conductor.

[0020] Furthermore, when the waveguide is a strip line having a ground electrode, a dielectric layer, and a strip conductor in this order, the radiation structure may be a slot formed in the ground electrode.

[0021] When the waveguide is a dielectric waveguide having a pair of metal plates and a strip dielectric sandwiched between the pair of metal plates, the radiating structure is preferably a slot formed in one of the metal plates.

[0022] In addition, when the radio wave emitter according to the present disclosure has a slot as the radiation structure, it may further have a metal microstructure as the radiation structure. In the radio wave emitter according to the present disclosure, it is preferable that the waveguide, the metal microstructure, and the modulation section are arranged in this order.

[0023] The metal microstructure is preferably a structure that can change radiation characteristics (for example, broaden the band or suppress loss) by being placed near the slot. Examples of the metal microstructure include a circular, square, rectangular, ring-shaped, or other planar metal structure.

[0024] The radiating structures are arranged at intervals of ½ or less of the free-space wavelength corresponding to the operating frequency. By setting the intervals between the radiating structures to ½ or less of the free-space wavelength, the generation of side lobes can be suppressed. The intervals between the radiating structures are preferably ⅓ or less of the free-space wavelength, more preferably ¼ or less. Furthermore, the intervals between the radiating structures are preferably 1 / 10 or more of the free-space wavelength.

[0025] <Modulation Section> The radio wave emitter according to the present disclosure includes a modulation section that modulates the radiated radio wave. The modulation section includes a material whose sheet resistance changes depending on the voltage.

[0026] (Materials whose sheet resistance changes with voltage) Materials whose sheet resistance changes with voltage have a minimum sheet resistance Rs at 25°C when an applied voltage is between -40V and 40V. Ｌ is 10,000Ω / □ or less. Ｌ By making the resistance equal to or less than 10,000 Ω / □, it is possible to increase the modulation of the radio wave intensity.

[0027] Rs Ｌ is 10,000Ω / □ or less, preferably 5000Ω / □ or less, and more preferably 1000Ω / □ or less. Ｌ The lower limit of the sheet resistance is, for example, 100 Ω / □. In the present disclosure, the sheet resistance is measured using the voltage-current characteristics of a field-effect transistor.

[0028] Maximum sheet resistance Rs at 25°C with an applied voltage of -40V to 40V Ｈ Rs Ｌ The ratio of Rs is preferably 0.5 or less, more preferably 0.2 or less, and even more preferably 0.1 or less. Ｈ Rs Ｌ The lower limit of the ratio is, for example, 0.01. Ｈ Rs Ｌ When the ratio is 0.5 or less, the modulation of the radio wave intensity can be increased.

[0029] For materials whose sheet resistance changes with voltage, the sheet resistance at 25°C is Rs １ and the sheet resistance at 80°C is Rs ２ In this case, Rs ２ / Rs １is preferably 0.5 to 2.0. Note that "sheet resistance at 25°C" means the sheet resistance measured at 25°C in the absence of applied voltage, and "sheet resistance at 80°C" means the sheet resistance measured at 80°C in the absence of applied voltage.

[0030] Rs ２ / Rs １ When the value is 0.5 to 2.0, the temperature dependency of the radio wave emitter is further reduced, and the temperature range in which it can be operated is wide.

[0031] For materials whose sheet resistance changes with voltage, the sheet resistance at 25°C is Rs １ The sheet resistance at 25°C after heating at 200°C for 1 hour is Rs ３ In this case, Rs ３ / Rs １ is preferably 0.8 to 1.2. ３ / Rs １ When the value is 0.8 to 1.2, the durability against heat is excellent.

[0032] The material whose sheet resistance changes with voltage is Rs Ｌ There are no particular limitations on the material as long as it has a resistivity of 10,000 Ω / □ or less, but graphene is preferred from the viewpoint of excellent durability against heat.

[0033] In the radio wave emitter according to the present disclosure, the radiation pattern changes in accordance with a change in sheet resistance due to an applied voltage. Specifically, the sheet resistance changes when a voltage is applied, and the angular distribution of the radiation pattern changes according to the amount of change. From this viewpoint, it is preferable that the voltages applied to the modulation sections are independently controlled in accordance with the sheet resistance corresponding to the desired change in the radiation pattern.

[0034] The modulation section preferably includes a substrate, an insulating layer, and a layer containing a material whose sheet resistance changes depending on voltage.

[0035] (Substrate) From the viewpoints of strength and heat resistance, the substrate is preferably a quartz substrate, a glass substrate, a ceramic substrate, or a silicon substrate. Among these, from the viewpoint of flatness, the substrate is preferably a silicon substrate.

[0036] From the viewpoint of radio wave transparency and voltage controllability, the volume resistivity of the substrate is preferably 10 Ωcm to 50 kΩcm, and more preferably 100 Ωcm to 5 kΩcm. In the present disclosure, the volume resistivity is measured using a four-probe method.

[0037] The thickness of the substrate is, for example, 10 μm to 1000 μm, and is determined by measuring the thickness at 10 points using a spectral interference wafer thickness meter and calculating the arithmetic average of the measured values.

[0038] (Insulating Layer) The insulating layer is a layer having insulating properties. In the present disclosure, "insulating" means a layer having a volume resistivity of 1×10 １０ Ωcm or more (preferably, 1×10 １２ This means that the resistance is greater than or equal to Ωcm.

[0039] The material constituting the insulating layer is not particularly limited as long as it is an insulating material, and examples thereof include SiO ２ Examples include:

[0040] From the viewpoint of capacitance, the thickness of the insulating layer is preferably 200 nm or less, and more preferably 100 nm or less. The lower limit of the thickness of the insulating layer is, for example, 10 nm. The thickness of the insulating layer is measured using an ellipsometer.

[0041] (Layer containing a material whose sheet resistance changes with voltage) The layer containing a material whose sheet resistance changes with voltage contains a material whose sheet resistance changes with voltage, and may further contain components other than the material whose sheet resistance changes with voltage, as necessary. Details of the material whose sheet resistance changes with voltage are as described above.

[0042] Furthermore, the modulation section preferably further includes a metal layer, which can increase modulation of radio wave intensity. When the modulation section further includes a metal layer, it is preferable that the metal layer and a layer containing a material whose sheet resistance changes with voltage are provided on the same plane. The modulation section is produced, for example, by forming an insulating layer on a substrate, then forming a metal layer having a plurality of openings of a predetermined size on the insulating layer, and forming a layer containing a material whose sheet resistance changes with voltage in the openings.

[0043] Examples of metals that can be used to form the metal layer include gold, nickel, chromium, titanium, silver, copper, and platinum. These metals can be used alone or in combination of two or more.

[0044] Specific configuration examples of the radio wave emitter according to the present disclosure will be described below with reference to FIGS. 1 to 5. FIG.

[0045] 1 includes a metal waveguide 11, a slot 11a formed in the metal waveguide 11 as a radiation structure, and a modulation section 12. The modulation section 12 is formed at a position opposite to the slot 11a.

[0046] 2 has, as a waveguide, a dielectric layer 21, a strip conductor 22 which is a line arranged on one surface of the dielectric layer 21, and a ground electrode 23 which is arranged on the other surface of the dielectric layer 21. The strip conductor 22 is a linear conductor and is provided as a straight line on a part of the dielectric layer 21. The ground electrode 23 is provided on the entire surface of the dielectric layer 21.

[0047] The radio wave emitter 200 also has, as a radiation structure, metal microstructures 24 and a modulation section 25. A plurality of the metal microstructures 24 are arranged at positions overlapping the strip conductor 22 in a plan view of the radio wave emitter 200. The modulation section 25 is formed at a position facing the metal microstructures 24.

[0048] 3 has, as a waveguide, a dielectric layer 31, a strip conductor 32 arranged on one surface of the dielectric layer 31, and a ground electrode 33 arranged on the other surface of the dielectric layer 31. The strip conductor 32 is a linear conductor and is provided as a straight line on a part of the dielectric layer 31.

[0049] The radio wave emitter 300 also has a radiation structure including slots 33a formed in the ground electrode 33, and a modulation section 34. A plurality of slots 33a are arranged at positions overlapping the strip conductor 32 in a plan view of the radio wave emitter 300. The modulation section 34 is formed at a position facing the slots 33a.

[0050] 4 has, as a waveguide, a strip dielectric 41, a metal plate 42 arranged on one surface of the strip dielectric 41, and a metal plate 43 arranged on the other surface of the strip dielectric 41. The strip dielectric 41 is a linear dielectric, and is sandwiched between the two metal plates 42 and 43 to form a linear line.

[0051] The radio wave emitter 400 also has slots 42a formed in the metal plate 42 as a radiation structure, and a modulation section 44. A plurality of slots 42a are arranged at positions overlapping the strip dielectric 41 in a plan view of the radio wave emitter 400. The modulation section 44 is formed at a position facing the slots 42a.

[0052] The radio wave emitter 500 shown in Fig. 5 is a modified example of the radio wave emitter 100. The radio wave emitter 500 has a metal waveguide 51, a slot 51a formed in the metal waveguide 51 as a radiation structure, a metal microstructure 52, and a modulation section 53. The metal microstructure 52 is formed at a position facing the slot 51a. The modulation section 53 is formed at a position facing the metal microstructure 52.

[0053] The above embodiment will be specifically described below using examples, but the above embodiment is not limited to these examples.

[0054] Example 1 Fabrication of Graphene FET Device Single-layer graphene manufactured by 2D Materials Research Institute was transferred onto a thermal oxide film of a p-type Si substrate (volume resistivity: 1000 Ωcm) on which a 90 nm thermal oxide film had been formed. A photoresist (product name "AZ5214E" manufactured by Merck) was applied to the single-layer graphene, followed by pre-baking, pattern exposure, post-baking, full-surface exposure, and development to form a resist pattern. Next, graphene in areas where the resist pattern was not formed was removed by oxygen plasma treatment, and the resist pattern was dissolved in an organic solvent (acetone) to obtain a graphene thin line pattern. A photoresist (product name "AZ5214E" manufactured by Merck) was again applied to the substrate on which the graphene thin line pattern had been formed, followed by baking, pattern exposure, and development to form a resist perforation pattern that would serve as an electrode portion. Next, 10 nm of Ni and 30 nm of Au were evaporated, and the metal thin film on the resist was removed together with the resist by lift-off to form metal electrodes (a laminated film of 10 nm of Ni and 30 nm of Au) only in the perforated pattern area. In this way, a graphene FET device (the channel length of the graphene part between the electrodes was 50 μm, and the channel width was 5 μm) was fabricated.

[0055] <Measurement of Sheet Resistance> The fabricated graphene FET device was placed in a vacuum chamber at a vacuum level of 3×10 －３ The device was subjected to a vacuum heat treatment at 200°C for 10 hours at 100 Pa, and then allowed to cool to 25°C. Using a semiconductor parameter analyzer (B1500A, KEYSIGHT), a drain voltage of 0.1 V was applied to the electrodes at both ends of the graphene channel, and a gate voltage was applied to the p-type Si substrate through the pedestal of the vacuum chamber. The drain current-gate voltage characteristics (IV characteristics) were measured while sweeping the gate voltage from -40 V to +40 V. From the obtained IV characteristics, the sheet resistance Rs when gate voltages of 0 V and 40 V were applied at 25°C was calculated. １ was calculated.

[0056]

[0057] Minimum sheet resistance Rs at 25°C when applied voltage is between -40V and 40V Ｌ The resistance was 390 Ω / □.

[0058] <Evaluation of Temperature Dependence of Sheet Resistance> The IV characteristics were similarly measured with the inside of the vacuum chamber heated to 80°C, and the sheet resistance Rs when gate voltages of 0 V and 40 V were applied at 80°C was ２ was calculated.

[0059]

[0060] <Evaluation of thermal durability of sheet resistance> After heating the inside of a vacuum chamber at 200°C for 1 hour, the device was allowed to cool to 25°C. Similarly, the IV characteristics were measured, and the sheet resistance Rs when gate voltages of 0V and 40V were applied at 25°C after the thermal durability test was ３ was calculated.

[0061]

[0062] The simulation was carried out using commercially available software (COMSOL Multiphysics, finite element method).

[0063] The waveguide shown in Figure 6 was used. The waveguide shown in Figure 6 is a waveguide with a rectangular cross section and an inner diameter of 7.112 mm x 3.556 mm. The thickness of the outer wall is 1.015 mm and the material is copper (electrical conductivity σ = 5.8 x 10 ７ S / m) Four slots (Slot 1 to Slot 4) were formed on the upper surface of the waveguide as a radiation structure.

[0064] In Fig. 6, L4 denotes the slot length, W4 denotes the slot width, and O4 denotes the offset. Slot 1: slot length 3.98 mm, slot width 0.55 mm, offset 1.3 mm Slot 2: slot length 3.99 mm, slot width 0.55 mm, offset 1.55 mm Slot 3: slot length 4.01 mm, slot width 0.55 mm, offset 1.87 mm Slot 4: slot length 3.97 mm, slot width 0.55 mm, offset 2.6 mm

[0065] As shown in Fig. 7, a modulation section was fabricated by laminating an insulating layer 72, graphene 73, an Au / Ni film 74, and a protective layer 75 in this order on a p-type silicon substrate 71 (volume resistivity 1000 Ωcm) having a thickness of 200 µm. The insulating layer 72 was 90 nm thick and was made of a 20 mm x 10 mm SiO２ A 50 nm thick Au / Ni film 74 having four openings each measuring 4.5 mm x 9 mm was formed on the insulating layer 72. Graphene 73 was formed in the four openings each measuring 4.5 mm x 9 mm. The protective layer 75 was a 90 nm thick Al ２ O ３ On the surface of the silicon substrate 71 opposite to the surface in contact with the insulating layer 72, an Au / Ni film 76 was formed in a pattern as a ground electrode.

[0066] The modulation section was disposed at a position 200 μm away from the upper surface of the waveguide 80 so that the waveguide 80 and the surface of the protective layer 75 faced each other.

[0067] By applying a gate voltage between the Au / Ni film 76 and the Au / Ni film 74, the sheet resistance of the graphene 73 changed, and the radiation pattern changed.

[0068] The radiation pattern (electric field intensity) of the radio wave emitter when a radio wave of 28 GHz was incident was analyzed under the sheet resistance condition at 25°C (condition 1) shown in Table 1. Fig. 8 shows the radiation pattern under condition 1 of Example 1.

[0069] 8, different radiation patterns were obtained when a voltage was applied only to Slot 2 and Slot 3 and when a voltage was applied only to Slot 1 and Slot 4. This result shows that the radio wave emitter of the present disclosure can control the radiation pattern in accordance with the change in sheet resistance due to the applied voltage.

[0070] Next, the radiation pattern (electric field intensity) of the radio wave emitter when a radio wave of 28 GHz was incident was analyzed under the sheet resistance condition at 80°C (condition 2) shown in Table 2. Fig. 9 shows the radiation pattern under condition 2 of Example 1.

[0071] As shown in FIG. 9, there is only a slight difference in the radiation pattern between Condition 1 and Condition 2, and the radio wave emitter of the present disclosure is expected to have low temperature dependency.

[0072] Next, under the condition of sheet resistance when heated at 200°C for 1 hour and then cooled to 25°C (condition 3) shown in Table 3, the radiation pattern (electric field intensity) of the radio wave emitter when radio waves of 28 GHz were incident thereon was analyzed.

[0073] FIG. 10 shows the radiation pattern under condition 3 of Example 1.

[0074] As shown in FIG. 10, there is only a slight difference in the radiation pattern between Condition 1 and Condition 3, and the radio wave emitter of the present disclosure is expected to have excellent heat durability.

[0075] Comparative Example 1 A simulation was performed in the same manner as in Example 1, except that the graphene in Example 1 was changed to pentacene (film thickness: 100 nm), which is an organic semiconductor. The sheet resistance of pentacene was measured by the following method.

[0076] <Fabrication of Pentacene FET> Metal electrodes (width 160 μm, distance between electrodes 1.5 mm) were formed on an n-type Si substrate (volume resistivity 0.01 Ω cm) on which a thermal oxide film of 250 nm had been formed by mask deposition of Ni (10 nm) and Au (30 nm). ２ The surface of the pentacene FET (pentacene film thickness: 100 nm) was hydrophobized by oxygen plasma treatment and HMDS (1,1,1,3,3,3-hexamethyldisilazane) treatment. A chloroform solution (15 mg / mL) of 13,6-N-sulfinylacetamidopentacene (pentacene precursor) was spin-coated onto the hydrophobized thermal oxide film, and then the pentacene precursor was converted to pentacene by heat treatment at 200°C for 1 minute in a nitrogen atmosphere.

[0077] <Measurement of Sheet Resistance> Using a semiconductor parameter analyzer (B1500A, KEYSIGHT), a drain voltage of −50 V was applied between the metal electrodes of the fabricated pentacene FET, and a gate voltage was applied to the n-type Si substrate, and the drain current-gate voltage characteristics (IV characteristics) were measured while sweeping the gate voltage from −40 V to +40 V. From the obtained IV characteristics, the sheet resistance Rs was calculated when gate voltages of 0 V and −40 V were applied at 25° C.

[0078]

[0079] FIG. 11 shows the radiation pattern in the first comparative example.

[0080] The antenna structure of Comparative Example 1 has a sheet resistance R ｓＬ Since the resistance is greater than 10,000 Ω / □, the change in the radiation pattern is small, and it was found that this is not suitable for a radio wave emitter.

[0081] [Comparative Example 2] A simulation was performed on a liquid crystal active antenna in which the radiation pattern changes depending on the dielectric constant of the liquid crystal. The waveguide of Comparative Example 2 used in the simulation was the same as the waveguide of Example 1 except for the slot length.

[0082] Slot 1: Slot length 4.58 mm, slot width 0.55 mm, offset 1.3 mm Slot 2: Slot length 4.59 mm, slot width 0.55 mm, offset 1.55 mm Slot 3: Slot length 4.61 mm, slot width 0.55 mm, offset 1.87 mm Slot 4: Slot length 4.77 mm, slot width 0.55 mm, offset 2.6 mm

[0083] The modulation section was fabricated by laminating a metal batch and a liquid crystal layer in this order on a 500 μm thick, 20 mm x 10 mm glass wafer. Specifically, four 50 nm thick, 4.5 mm x 9 mm metal batches were provided on the glass wafer, and a liquid crystal layer was then placed on top of them. The liquid crystal layer was a layer made of 4'-pentyl-4-biphenylcarbonitrile (5CB).

[0084] The modulation section was arranged so that the waveguide and the liquid crystal layer faced each other.

[0085] By applying a gate voltage between the metal batch and the waveguide, the liquid crystal molecules were oriented, changing the dielectric constant in the vertical direction and thus the radiation pattern.

[0086] The radiation pattern (electric field strength) of the radio wave emitter was analyzed when a 28 GHz radio wave was incident at an applied voltage of 0 V to 40 V at 25°C and 80°C. Fig. 12 shows the radiation pattern of Comparative Example 2 at 25°C. Fig. 13 shows the radiation pattern of Comparative Example 2 at 80°C.

[0087] 12 and 13, the radiation pattern changes at 25° C., but does not change at 80° C. This indicates that the liquid crystal antenna has a high temperature dependency and a narrow operating temperature range.

[0088] The disclosure of Japanese Patent Application No. 2024-048726, filed on March 25, 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

Claims

1. A waveguide, a radiation structure for emitting radio waves, and a modulation section for modulating the radiated radio waves, wherein a plurality of the radiation structures are arranged at intervals of 1 / 2 or less of the free space wavelength corresponding to the operating frequency, wherein the modulation section includes a material whose sheet resistance changes with voltage, wherein the radiation pattern changes with the change in sheet resistance due to the applied voltage, and wherein the material whose sheet resistance changes with voltage has a minimum sheet resistance Rs at 25°C when an applied voltage of -40V to 40V is applied. Ｌ A radio wave emitter having a resistance of 10,000 Ω / □ or less.

2. The material whose sheet resistance changes with voltage has a maximum sheet resistance Rs at 25°C when an applied voltage of -40V to 40V is applied. Ｈ Rs Ｌ 2. The radio wave emitter according to claim 1, wherein the ratio is 0.5 or less.

3. The material whose sheet resistance changes with voltage is Rs １ and the sheet resistance at 80°C is Rs ２ In this case, Rs ２ / Rs １ 3. The radio wave emitter according to claim 1, wherein the value of σ is 0.5 to 2.

0.

4. The material whose sheet resistance changes with the voltage is Rs １ The sheet resistance at 25°C after heating at 200°C for 1 hour is Rs ３ In this case, Rs ３ / Rs １ 3. The radio wave emitter according to claim 1, wherein the value of σ is 0.8 to 1.

2.

5. The radio wave emitter according to claim 1 or 2, wherein the material whose sheet resistance changes with voltage is graphene.

6. The radio wave emitter according to claim 1, wherein the waveguide is a metal waveguide, and the radiation structure is a slot formed in the metal waveguide.

7. The radio wave emitter according to claim 1 or 2, wherein the waveguide has a ground electrode, a dielectric layer, and a strip conductor in this order, and a metal microstructure is provided on the strip conductor as the radiation structure, and the waveguide, the metal microstructure, and the modulation section are arranged in this order.

8. The radio wave emitter according to claim 1, wherein the waveguide has a ground electrode, a dielectric layer, and a strip conductor in this order, and the radiation structure is a slot formed in the ground electrode.

9. The radio wave emitter according to claim 1, wherein the waveguide comprises a pair of metal plates and a strip dielectric sandwiched between the pair of metal plates, and the radiation structure is a slot formed in one of the pair of metal plates.

10. A radio wave emitter according to claim 6, claim 8 or claim 9, further comprising a metal microstructure as the radiation structure, wherein the waveguide, the metal microstructure and the modulation section are arranged in this order.

11. A radio wave emitter according to claim 1 or claim 2, wherein there are a plurality of said modulation sections, and the voltages applied to the plurality of modulation sections are controlled independently of each other.

12. The radio wave emitter according to claim 1 or 2, wherein the modulation section includes a substrate, an insulating layer, and a layer containing a material whose sheet resistance changes depending on the voltage.

13. The radio wave emitter according to claim 12, wherein the volume resistivity of the substrate is 10 Ωcm to 50 kΩcm.

14. The radio wave emitter according to claim 12, wherein the insulating layer has a thickness of 200 nm or less.

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