Antenna device, communication device, and imaging system

Abstract

There is provided an antenna apparatus for generating or detecting electromagnetic waves, including: a first active antenna including a first oscillator and a first antenna; the second active antenna comprises a second oscillator and a second antenna; a coupling line coupling the first antenna and the second antenna; a first terminal receiving a signal for controlling a first oscillation frequency of the first oscillator, the first oscillation frequency being a first oscillation frequency before synchronization by the coupling line; and a second terminal receiving a signal for controlling a second oscillation frequency of the second oscillator independently of the first oscillation frequency, the second oscillation frequency being a second oscillation frequency before synchronization by the coupling line.

Description

Technical Field

[0001] The present invention relates to an antenna device for outputting or detecting electromagnetic waves. Background Art

[0002] As a current injection light source for generating electromagnetic waves such as terahertz waves, an oscillator formed by integrating a resonator and an element having an electromagnetic wave gain relative to the terahertz wave is known. Among them, an oscillator formed by integrating a resonant tunneling diode (RTD) and an antenna is expected to become an element operating in a frequency domain of about 1THz at room temperature. PTL 1 discloses a terahertz wave antenna array, in which a plurality of active antennas each formed by an integrated RTD oscillator and an antenna are arranged on the same substrate. In the antenna array disclosed in PTL 1, a coupling line that couples a plurality of active antennas to each other is used so that the plurality of active antennas oscillate in the same phase in synchronization with each other.

[0003] Citation List

[0004] Patent Literature

[0005] PTL 1: Japanese Patent Laid-Open No. 2014-200065

[0006] Non-patent literature

[0007] NPL 1: Jpn. J. Appl. Phys., Vol. 47, No. 6 (2008), pp. 4375-4384

[0008] NPL 2: J. Appl. Phys., Vol. 103, 124514 (2008) Summary of the invention

[0009] Technical issues

[0010] In the antenna array described in PTL 1, the phases of a plurality of active antennas can be synchronized with each other, but application of beamforming in which a beam is directed in an arbitrary direction by controlling the phase difference between the active antennas has not been studied.

[0011] Solution to the problem

[0012] The present invention provides a technique that enables beamforming to be applied in an antenna arrangement comprising a plurality of active antennas.

[0013] An antenna device according to one aspect of the present invention is an antenna device for generating or detecting electromagnetic waves, comprising: a first active antenna including a first oscillator and a first antenna; a second active antenna including a second oscillator and a second antenna; a coupling line configured to couple the first antenna and the second antenna; a first terminal configured to receive a signal for controlling a first oscillation frequency of the first oscillator before synchronization through the coupling line; and a second terminal configured to receive a signal for controlling a second oscillation frequency of the second oscillator before synchronization through the coupling line independently of the first oscillation frequency.

[0014] Advantageous Effects of the Invention

[0015] According to the present invention, beamforming may be applied in an antenna arrangement comprising a plurality of active antennas.

[0016] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. Note that throughout the drawings, the same reference numerals represent the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present invention and, together with the description, serve to explain the principles of the present invention.

[0018] Figure 1 is a block diagram schematically showing an arrangement of an antenna device;

[0019] Figure 2 is the circuit diagram of the antenna array;

[0020] Figure 3 is a schematic plan view showing an example of arrangement of antenna devices;

[0021] Figure 4A is a cross-sectional view of elements included in the antenna device;

[0022] Figure 4B is a cross-sectional view of elements included in the antenna device;

[0023] Figure 5A is a schematic diagram showing the effect of the antenna device;

[0024] Figure 5B is a schematic diagram used to explain beamforming;

[0025] Figure 6 is a block diagram schematically showing an arrangement of an antenna device;

[0026] Figure 7 is a schematic plan view showing an example of arrangement of antenna devices;

[0027] Figure 8is a schematic plan view showing elements included in the antenna device;

[0028] Fig. 9 is a schematic plan view showing elements included in the antenna device;

[0029] Fig. 10A is a cross-sectional view of elements included in the antenna device;

[0030] Fig. 10B is a cross-sectional view of elements included in the antenna device;

[0031] Fig. 10C is a cross-sectional view of elements included in the antenna device;

[0032] Fig.11 is a block diagram schematically showing an arrangement of an antenna device;

[0033] Fig.12 is a schematic plan view showing an example of arrangement of antenna devices;

[0034] Fig.13A is a cross-sectional view of elements included in the antenna device;

[0035] Fig. 13B is a cross-sectional view of elements included in the antenna device;

[0036] Fig.14A is a view showing an example of the arrangement of a camera system using an antenna device; and

[0037] Fig. 14B is a view showing an example of the arrangement of a communication system using an antenna device. DETAILED DESCRIPTION

[0038] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention. A plurality of features are described in the embodiments, but are not limited to the invention requiring all such features, and a plurality of such features may be appropriately combined. In addition, in the accompanying drawings, the same reference numerals are given to the same or similar configurations, and redundant descriptions thereof are omitted.

[0039] [First embodiment]

[0040] Reference Figures 1 to 4A and Figure 4BThe arrangement of the antenna device 10 suitable for terahertz waves according to this embodiment is described. Note that the case where the antenna device 10 is used as a transmitter will be described below in particular, but the antenna device 10 can also be used as a receiver. The terahertz wave indicates an electromagnetic wave in the frequency range of 10 GHz (inclusive) to 100 THz (inclusive), and in the example, indicates an electromagnetic wave in the frequency range of 30 GHz (inclusive) to 30 THz (inclusive).

[0041] Figure 1 1 is a block diagram for explaining an example of a system configuration of the antenna device 10. The antenna device 10 includes an element 12 in which an antenna is formed, a bias control unit 13, and a beam direction control unit 14.

[0042] Element 12 is an antenna element including an antenna array 11, which is formed by arranging a plurality of active antennas 11a to 11i in an array. The active antenna 11a is formed by integrating at least one antenna 100a and a semiconductor 101a as an oscillation source, and is configured to transmit a terahertz wave TW of an oscillation frequency f0. The same applies to the remaining active antennas, and each active antenna includes an antenna and a semiconductor, and is configured to transmit a terahertz wave TW of an oscillation frequency f0. In each of the active antennas 11a to 11i, components other than each of the semiconductors 101a to 101i as oscillation members can be interpreted as antennas, and for example, only antenna conductors or a combination of antenna conductors and ground (GND) conductors can be interpreted as antennas. Note that semiconductors 101a to 101i and antennas 100a to 100i are formed in the same shape relative to active antennas 11a to 11i, respectively. Note that "same shape" indicates the same shape in design, and also includes almost the same shape in the implemented article. Therefore, semiconductors 101a to 101i and antennas 100a to 100i have the same characteristics. Therefore, if it is not necessary to distinguish these semiconductors and antennas in particular, they will be referred to as semiconductors 101 and antennas 100 below. Each of the semiconductors 101a to 101i of active antennas 11a to 11i includes a semiconductor structure for generating or detecting terahertz waves. This embodiment will describe an example of using a resonant tunneling diode (RTD) as a semiconductor structure. Note that, as a semiconductor structure, a semiconductor with a nonlinearity (nonlinearity of a current with a voltage change in a current-voltage characteristic) of an electromagnetic wave gain or carrier relative to a terahertz wave is sufficient, and the semiconductor structure is not limited to RTD. Alternatively, an oscillator of any form other than a semiconductor structure can be used. Note that a semiconductor for generating or detecting terahertz waves will be sometimes referred to as RTD below. Active antennas 11a to 11i are electrically connected by coupling lines 102ab to 102hi as transmission lines that couple antennas to each other to cause a mutual injection locking phenomenon. For example, active antennas 11a and 11b are connected via a coupling line 102ab.

[0043] The bias control unit 13 is a power supply for controlling a bias signal to be applied to the semiconductor 101, and is electrically connected to the semiconductor 101 in the element 12 via a bias line 105. The beam direction control unit 14 supplies a control signal to the bias control unit 13 via a control line 106. The beam direction control unit 14 determines the bias voltage or current to be applied to each of the semiconductors 101a to 101i of the active antennas 11a to 11i by supplying a control signal to the bias control unit 13 via the control line 106. At least one of the bias voltage and the bias current will sometimes be referred to as "bias" hereinafter. Each of the semiconductors 101a to 101i has a characteristic that an oscillation frequency changes depending on the bias applied to the semiconductor.

[0044] Active antennas 11a to 11i oscillate at different frequencies f1 to f9 in the terahertz band according to the bias voltage applied, respectively. Active antennas 11a to 11i oscillate at a frequency f0 by mutual injection locking phenomenon through coupling lines 102ab to 102hi connected between active antennas 11a to 11i. Active antennas 11a to 11i oscillate at a frequency f0, respectively, according to the frequency f0 and the oscillation frequencies f1 to f9 in the state without mutual injection locking, respectively, with the phase oscillation calculated. That is, active antennas 11a to 11i oscillate with the phase difference corresponding to the same frequency f0 and the original oscillation frequencies f1 to f9, respectively.

[0045] In this embodiment, by focusing on the characteristics, the phase difference between each active antenna 11a to 11i is adjusted by adjusting the bias applied to each of the active antennas 11a to 11i. By adjusting the phase difference, beamforming can be performed so that the beam is directed from the vertical direction of the substrate to a predetermined direction (so that the peak of the gain of the beam is directed to a predetermined direction). In this embodiment, the beam direction control unit 14 determines the phase difference between each active antenna 11a to 11i, and supplies a control signal to the bias control unit 13 so that the bias corresponding to each phase difference is supplied to each of the active antennas 11a to 11i. The bias control unit 13 applies the bias corresponding to the control signal to each of the active antennas 11a to 11i, thereby performing beamforming so that the beam is directed to a predetermined direction. This allows the antenna array 11 to transmit the terahertz wave TW of the oscillation frequency f0 in a manner such that the peak of the antenna gain is directed from the vertical direction of the substrate to an arbitrary angle.

[0046] Figure 21 is a circuit diagram for explaining the electrical connection between active antenna 11a and 11b. Note that the description will be provided by focusing on the relationship between active antenna 11a and 11b, but this also applies to the relationship between the remaining active antennas. In active antenna 11a, the negative resistance -r of semiconductor 101a and the impedance Z of antenna 100a are connected in parallel. Note that the impedance Z includes a resistance component and an LC component caused by the structure of antenna 100a. The bias applied by bias control unit 13 to semiconductor 101a by applying a bias current is represented as power supply 13a. Note that active antenna 11b also has the same arrangement. For example, bias control unit 13 supplies the current required for driving semiconductors 101a and 101b, and separately adjusts the bias applied to semiconductors 101a and 101b. That is, antenna device 10 is configured to separately set the first bias applied to semiconductor 101a and the bias applied to semiconductor 101b. These biases are controlled when the beam direction control unit 14 supplies control signals to the bias control unit 13 via control lines 106a and 106b, respectively. Figure 2 An example of arrangement in which the beam direction control unit 14 sends a control signal to the bias control unit 13 via a signal line different for each active antenna is shown, but the present invention is not limited thereto. That is, as long as the bias control unit 13 is notified of information that can specify the bias of the semiconductor 101 to be applied to each active antenna, the bias control unit 13 can be notified of the information as a piece of information. On the other hand, the bias control unit 13 is configured to control the bias for each active antenna individually. The element 12 has a terminal (input line) for receiving a signal for controlling the magnitude of the bias for each active antenna individually. It is noted that, in the case of using an RTD as the semiconductor 101, the bias voltage is selected from the voltage in the differential negative resistance region of the RTD.

[0047] Adjacent active antennas 11a and 11b are electrically connected by coupling lines 102ab, thereby coupling antennas to each other. Coupling lines 102ab are connected to active antennas 11a and 11b via capacitors C1 and C2. Capacitors C1 and C2 are used as high-pass filters and are arranged to be capacitors configured to be short-circuited with respect to electromagnetic waves in the terahertz band and open-circuited with respect to electromagnetic waves in the low-frequency band. Note that the remaining active antennas 11b to 11i have the same arrangement. It is also noted that an arrangement in which neither capacitor C1 nor C2 is provided can be adopted.

[0048] (Example of Implementation)

[0049] Reference Figure 3 , Figure 4A and Figure 4B The structure and arrangement of the antenna device 10 of the first embodiment will be described in detail. Figure 3is a schematic plan view of the element 12 in which nine active antennas 11a to 11i are arranged in a 3×3 matrix. Figure 4A and Figure 4B Along the Figure 3 1 is a cross-sectional view of the element 12 taken along the lines A-A' and BB' in FIG. The element 12 may be referred to as a chip, for example. The element 12 is an element that oscillates or detects a terahertz wave of a frequency f0, and is made of a semiconductor material. In this embodiment, as the element 12, an antenna array in which nine active antennas 11a to 11i are arranged in a 3×3 matrix will be exemplified. Note that in Figure 3 In the example shown in , a square patch antenna is used as the antenna 100 included in each active antenna. However, the present invention is not limited to this. For example, the number of active antennas is not limited to nine, and even if the active antennas are arranged in a matrix, they can be arranged in a form other than a 3×3 matrix. That is, for any positive integers m and n, the active antennas 11a to 11i can be arranged in an m×n matrix (m or n is 2 or more), thereby forming an antenna array 11. When the number of active antennas (i.e., m or n) increases, the beam gain in the beam orientation direction can be improved by narrowing the beam width. Note that when m or n is 1, the antenna array 11 has one column, and beamforming can be performed in the arrangement direction. The antenna 100 can be, for example, a slot antenna, and does not need to be a patch antenna. Note that each of the active antennas 11a to 11i is used as a resonator that resonates the terahertz wave and a radiator that transmits or receives the terahertz wave. In the element 12, the active antenna (antenna 100) may be arranged at a pitch (interval) equal to or less than the wavelength of the detected or generated terahertz wave or a pitch (interval) of an integral multiple of the wavelength. The discussion of this embodiment may be applied not only to antennas that transmit horizontal / vertical polarized waves but also to antennas that transmit circularly polarized waves.

[0050] As described above, each active antenna includes a semiconductor 101 as an oscillator, and the antennas arranged adjacent to each other are coupled by coupling lines 102 to synchronize the oscillators with each other. The active antenna and each coupling line 102 are connected by capacitive coupling. When adjacent antennas are connected by coupling lines, the length of the coupling line 102 is designed to meet the phase matching conditions in one or both directions of the X direction and the Y direction. The coupling line 102 can be designed to have a length such as that the electrical length in the coupling line 102 between the semiconductors 101 of adjacent active antennas is equal to an integer multiple of 2π. That is, the length of the coupling line 102 can be set to be equal to an integer multiple of the wavelength of the propagated electromagnetic wave when the RTD is connected by the coupling line 102.

[0051] First, the arrangement of each active antenna forming element 12 will be described, and then the arrangement of bias control unit 13 and beam direction control unit 14 will be described. Then, after describing the example of actual material and structural dimensions, the manufacturing method of element 12 will be explained. It is noted that the corresponding active antennas 11a to 11i have the same arrangement. Therefore, if it is not necessary to distinguish active antennas 11a to 11i in particular, they are collectively referred to as "active antennas" hereinafter. That is, the arrangement of "active antennas" to be described below is applicable to each of active antennas 11a to 11i. Similarly, the symbol "a" is added to the component corresponding to the active antenna 11a, but the symbol is omitted when it is not necessary to distinguish active antennas in particular.

[0052] (Active Antenna)

[0053] like Figure 4A and Figure 4B As shown in FIG. 1 , the active antenna includes a substrate 122, a conductor layer 121, a conductor forming the antenna 100 (hereinafter sometimes referred to as “conductor 100”), and dielectric layers 119 and 120. Note that Figure 4A and Figure 4B As shown in FIG. 1 , the substrate 122, the conductor layer 121, and the conductor 100 are stacked in this order, and the dielectric layers 119 and 120 are located between the two conductor layers (wiring layers) of the conductor layer 121 and the conductor 100. Note that the dielectric layers 119 and 120 are arranged in the order of the dielectric layer 120 and the dielectric layer 119 starting from the conductor layer 121 side. Figure 4A and Figure 4B The arrangement of the antenna shown in is called a microstrip antenna using a microstrip line having a finite length. An example of using a patch antenna as a microstrip resonator will now be described. Conductor 100 is a patch conductor (upper conductor of the patch antenna) of an active antenna arranged to face conductor layer 121 across dielectric layers 119 and 120. Conductor layer 121 serves as a ground conductor (GND conductor) for electrical grounding and also as a reflector layer. The active antenna is configured to operate as a resonator, wherein conductor 100 is disposed at Figure 3 The width in the Y direction (resonance direction) is λ THz / 2. Note that λ THz represents the effective wavelength of the terahertz wave resonating in the active antenna in the dielectric layers 119 and 120. If λ0 represents the wavelength of the terahertz wave in vacuum, and ε r represents the effective relative dielectric constant of the dielectric layer 119, then we obtain λ THz =λ0×ε r -1 / 2 .

[0054] The active antenna has a semiconductor 101 (semiconductor layer or semiconductor structure). Figure 1Each of the semiconductors 101a to 101i in corresponds to, and as described above, is a resonant tunneling diode (RTD) in this embodiment. RTD is a typical semiconductor structure having electromagnetic wave gain in the frequency band of terahertz waves, and is also referred to as an active layer. Therefore, semiconductor 101 is sometimes referred to as "RTD" hereinafter. RTD has a resonant tunneling structure layer including a plurality of tunneling barrier layers, wherein a quantum well layer is provided between the plurality of tunneling barrier layers, and has a multi-quantum well structure for generating terahertz waves by inter-subband carrier migration. RTD has a terahertz wave frequency domain electromagnetic wave gain based on a photon-assisted tunneling phenomenon in the differential negative resistance region of the current-voltage characteristic, and performs self-excited oscillation in the differential negative resistance region.

[0055] The semiconductor 101 is electrically connected to the conductor 100. The semiconductor structure is, for example, a mesa structure, and the semiconductor 101 includes an electrode (for example, an ohmic or Schottky electrode) for contacting the semiconductor structure and an electrode layer for connection to upper and lower wiring layers. The semiconductor 101 is located in an active antenna and is configured to oscillate or detect electromagnetic waves of terahertz waves. The semiconductor 101 is formed of a semiconductor layer having an electromagnetic wave gain or nonlinearity with respect to terahertz waves.

[0056] The active antenna is an active antenna formed by integrating the semiconductor 101 and the patch antenna (conductor 100). The frequency f of the terahertz wave oscillated from the single active antenna is determined based on the resonant frequency of the full parallel resonant circuit obtained by combining the reactance of the patch antenna and the semiconductor 101. THz More specifically, regarding the resonant circuit obtained by combining the RTD and the admittance of the antenna (YRTD and Yaa) from the equivalent circuit of the oscillator described in NPL 1, the frequency that satisfies the amplitude condition given by expression (1) and the phase condition given by equation (2) is determined as the oscillation frequency f THz .

[0057] Re[YRTD]+Re[Y11]≤0...(1)

[0058] Im[YRTD]+Im[Y11]=0...(2)

[0059] Where YRTD represents the admittance of semiconductor 101, Re represents the real part, and Im represents the imaginary part. Since semiconductor 101 includes RTD as a negative resistance element, Re[YRTD] has a negative value. Y11 represents the admittance of the entire structure of the active antenna when viewed from semiconductor 101.

[0060] Note that, as semiconductor 101, a quantum cascade laser (QCL) having a semiconductor multilayer structure of hundreds to thousands of layers can be used. In this case, semiconductor 101 is a semiconductor layer including a QCL structure. As semiconductor 101, a negative resistance element commonly used in millimeter wave bands, such as a Gunn diode or an IMPATT diode, can be used. As semiconductor 101, a high-frequency element, such as a transistor having one terminal terminated, can be used, and a heterojunction bipolar transistor (HBT), a compound semiconductor FET, a high electron mobility transistor (HEMT), etc. can be used as the transistor. As semiconductor 101, a differential negative resistance of a Josephson device using a superconducting layer can be used. That is, semiconductor 101 does not need to be an RTD, as long as it has a semiconductor structure for generating or detecting electromagnetic waves in a predetermined frequency band, and any structure with the same characteristics can be used. In this example, RTD is used as a component suitable for terahertz waves, but an antenna array corresponding to electromagnetic waves in any frequency band can be realized by the arrangement described in this embodiment. That is, the semiconductor 101 according to this embodiment is not limited to the RTD that outputs the terahertz wave, and can be formed using a semiconductor that can output electromagnetic waves in an arbitrary frequency band.

[0061] If a microstrip resonator such as a patch antenna has a thick dielectric layer, the conductor loss is reduced and the radiation efficiency is improved. Dielectric layers 119 and 120 require that thick films (usually 3 μm or more) can be formed, low loss / low dielectric constants are obtained in the terahertz band, and fine processing is high (flattening or etching). As the thickness of the dielectric layer increases, the radiation efficiency increases, but if the thickness is too large, multimode resonance may occur. Therefore, the thickness of the dielectric layer can be designed to be within a range where its upper limit is 1 / 10 of the oscillation wavelength. On the other hand, in order to achieve high frequency and high output of the oscillator, it is necessary to achieve miniaturization and high current density of the diode. To this end, the dielectric layer is also required to suppress leakage current and take anti-migration measures as the insulating structure of the diode. In order to meet the above two requirements, dielectric layers of different materials can be used as dielectric layers 119 and 120.

[0062] As a material for the dielectric layer 119, an organic dielectric material such as BCB (benzocyclobutene, ε-butylene) from Dow Chemical Company can be used. r1 =2), polytetrafluoroethylene or polyimide. In this example, ε r1represents the relative dielectric constant of the dielectric layer 119. A TEOS oxide film or an inorganic dielectric material such as spin-on glass, which can form a relatively thick film and has a low dielectric constant, can be used for the dielectric layer 119. The dielectric layer 120 is required to have an insulating property (a property of being an insulator or a high resistor that does not conduct electricity with respect to a DC voltage), a barrier property (a property of preventing diffusion of a metal material used for an electrode), and processability (processability with sub-micron precision). As a material that satisfies these properties, for example, silicon oxide (ε r2 =4), silicon nitride (ε r2 =7), inorganic insulating materials such as aluminum oxide or aluminum nitride. r2 represents the relative dielectric constant of the dielectric layer 120. Note that the dielectric layer 118 may also have the same characteristics as those of the dielectric layer 120.

[0063] If the dielectric layers 119 and 120 have a multilayer arrangement as in this embodiment, the relative dielectric constant ε of the dielectric layers 119 and 120 is r is based on the thickness of the dielectric layer 119 and the relative dielectric constant ε r1 and the thickness and relative dielectric constant ε of the dielectric layer 120 r2 In order to reduce the difference in dielectric constant between the antenna and air from the perspective of impedance matching between the antenna and space, a dielectric layer different from the dielectric layer 120 and having a low relative dielectric constant (ε r1 <ε r2 ) is used for the dielectric layer 119. Note that, in the antenna device 10, the dielectric layer does not need to have a multilayer arrangement, and may have a structure formed of a layer of one of the above-mentioned materials.

[0064] The semiconductor 101 is arranged on a conductor layer 121 formed on a substrate 122. The semiconductor 101 and the conductor layer 121 are electrically connected to each other. Note that in order to reduce ohmic loss, the semiconductor 101 and the conductor layer 121 may be connected with low resistance. The through hole 114 is arranged on the opposite side of the side on which the conductor layer 121 is arranged with respect to the semiconductor 101, and is electrically connected to the semiconductor 101. The semiconductor 101 is embedded in the dielectric layer 120, and the dielectric layer 120 covers the periphery of the semiconductor 101. Note that the "through hole" indicates a through electrode extending through a layer.

[0065] Semiconductor 101 includes an ohmic electrode as a conductor, which makes ohmic contact with the semiconductor to reduce RC delay and ohmic loss caused by series resistance. As the material of the ohmic electrode, for example, Ti / Au, Ti / Pd / Au, Ti / Pt / Au, AuGe / Ni / Au, TiW, Mo, ErAs, etc. can be used. It is noted that this material is represented by a chemical symbol, and the material represented by each chemical symbol will not be described in detail. The same applies to the following description. By using a semiconductor doped with an impurity semiconductor at a high concentration in the area where the semiconductor contacts the ohmic electrode to reduce the contact resistance, high output and high frequency can be achieved. In the case of using RTD as semiconductor 101, the absolute value of the negative resistance indicating the magnitude of the gain of the RTD used in the terahertz wave band is about 1 to 100Ω, so the loss of electromagnetic waves can be suppressed to 1% or less. Therefore, as a guide, the contact resistance in the ohmic electrode can be suppressed to 1Ω or less. In order to operate in the terahertz wave band, the semiconductor 101 is formed to have a width of about 0.1 to 5 μm as a typical value. Therefore, by setting the resistivity to 10 Ω·μm 2 or less, the contact resistance can be suppressed to the range of 0.001Ω to several Ω.

[0066] The semiconductor 101 may be configured to include a metal (Schottky electrode) that does not make an ohmic contact but makes a Schottky contact. In this case, the contact interface between the Schottky electrode and the semiconductor exhibits a rectifying property, and the active antenna AA can be used as a terahertz wave detector. Note that the arrangement using the ohmic electrode will be described below.

[0067] like Figure 4A As shown in , the substrate 122, the conductor layer 121, the semiconductor 101, the through hole 114, the conductor 100 and the coupling line 102 (conductor) are stacked in this order in the active antenna. The through hole 114 is a conductor formed in the dielectric layer 119, and the conductor 100 and the semiconductor 101 are electrically connected via the through hole 114. If the width of the through hole 114 is too large, the radiation efficiency deteriorates due to the degradation of the resonant characteristics of the patch antenna and the increase of the parasitic capacitance. Therefore, the width of the through hole 114 can be set to a width that does not interfere with the resonant electric field, usually 1 / 10 or less of the effective wavelength λ of the terahertz standing wave of the oscillation frequency f0 in the active antenna. The width of the through hole 114 can be small to the extent that the series resistance is not increased, and as a guide, it can be reduced to about twice the skin depth. Considering that the series resistance is reduced to a value not exceeding 1Ω, as a guide, the width of the through hole 114 generally falls within the range of 0.1μm (inclusive) to 20μm (inclusive).

[0068] refer to Figure 4B, the conductor 100 is electrically connected to the wiring 111 via the through hole 110, and the wiring 111 is electrically connected to the bias control unit 13 via the bias line 105 which is a wiring formed in the chip. The bias line 105 is arranged between the conductor 100 and the conductor layer 121, and more specifically, at the midpoint between the dielectric layers 119 and 120. Note that the bias line 105 is arranged at a position that does not overlap with the conductor 100 in a plan view so as not to be affected by the antenna radiation or affect the antenna radiation. Two wirings 111 are extracted from each antenna. For example, referring to Figure 3 and Figure 4B , with respect to the conductor 100a of the active antenna 11a, through holes 110a1 and 110a2 are led out and connected to wirings 111a1 and 111a2, respectively. Wirings 111a1 and 111a2 are electrically connected to the bias control unit 13 via bias lines 105a. The bias control unit 13 is a power supply for supplying a bias signal to the semiconductor 101 of the active antenna. Therefore, if the bias line 105 is connected to the wiring 111 led out from each antenna, the bias is supplied to the semiconductor 101 of each antenna. In this embodiment, when the bias line 105 is prepared separately for each active antenna, the bias to be applied to the semiconductor 101 in each active antenna can be set separately. For example, the bias control unit 13 controls the bias to be applied to the semiconductor 101 of each active antenna separately via a terminal for separately controlling the bias of each of the multiple active antennas provided in the element 12.

[0069] The through hole 110 is a connection portion for electrically and mechanically connecting the wiring 111 to the conductor 100. The structure that electrically connects the upper layer and the lower layer is called a through hole. In addition to the role as a member forming a patch antenna, the conductor layer 121 and the conductor 100 are also connected to these through holes to serve as electrodes for injecting current into the RTD as the semiconductor 101. In this embodiment, as the through hole 110 and the wiring 111, a material with a resistivity of 1×10-6Ω·m or less can be used. More specifically, as a material, a metal or a metal compound such as Ag, Au, Cu, W, Ni, Cr, Ti, Al, AuIn alloy, or TiN is used.

[0070] The width of the through hole 110 is smaller than the width of the conductor 100. The width of the conductor 100 is related to the resonance direction of the electromagnetic wave in the active antenna (ie, Figure 3The width of the portion of the wiring 111 connected to the through hole 110 (connecting portion) is smaller (thinner) than the width of the conductor 100 (active antenna). These widths may be 1 / 10 or less (λ / 10 or less) of the effective wavelength λ of the terahertz standing wave of the oscillation frequency f0 in the active antenna. This is because if the through hole 110 and the wiring 111 are arranged at positions where the widths are such that they do not interfere with the resonant electric field in the active antenna, the radiation efficiency can be improved.

[0071] The position of through hole 110 can be arranged at the node of the electric field of the terahertz standing wave of oscillation frequency f0 in the active antenna. At this time, through hole 110 and wiring 111 are configured so that the impedance is fully higher than the absolute value of the differential negative resistance of the RTD as semiconductor 101 in the frequency band near the oscillation frequency f0. In other words, through hole 110 and wiring 111 are connected to another active antenna, so that high impedance is obtained when looking from RTD at oscillation frequency f0. In this case, another active antenna is isolated (separated) on the path via bias line 105 at frequency f0. Therefore, the current of the oscillation frequency f0 induced by each active antenna does not affect the adjacent antenna via bias line 105 and bias control unit 13. In addition, the interference between the standing electric field of the oscillation frequency f0 in the active antenna and these power supply components is suppressed.

[0072] The bias control unit 13 is arranged outside the chip to supply a bias signal to the semiconductor 101 of each antenna. The bias control unit 13 may include a stabilization circuit for suppressing parasitic oscillations at low frequencies. The stabilization circuit is set to have an impedance lower than the absolute value of the negative resistance corresponding to the gain of the semiconductor 101 in a frequency band from DC to 10 GHz. In order to stabilize the relatively high frequency of 0.1 to 10 GHz, an AC short circuit can be arranged by connecting a resistive layer of TiW and a MIM (metal-insulator-metal) capacitor in series to each of the bias lines 105a to 105i. In this case, the MIM capacitor has a large capacity in the above-mentioned frequency range, and has a capacity of about several pF in the example.

[0073] (Antenna Array)

[0074] Figure 3The arrangement of the antenna array 11 is shown, in which nine active antennas 11a to 11i are arranged in a 3×3 matrix, and each of these active antennas individually oscillates the terahertz wave of each of the frequencies f1 to f9. It is noted that the number of active antennas is not limited to nine. For example, 16 active antennas can be arranged in a 4×4 matrix, or 15 active antennas can be arranged in a 3×5 matrix. Adjacent antennas are mutually coupled through a coupling line 102, and synchronized with each other through a mutual injection locking phenomenon to output a terahertz wave of an oscillation frequency f0. The mutual injection locking phenomenon is a phenomenon in which multiple self-excited oscillators are pulled to oscillate synchronously with each other through interaction. For example, active antennas 11a and 11d are mutually coupled through a coupling line 102ad, and are mutually coupled via a conductor layer 121. The same applies to other adjacent active antennas. It is noted that "mutual coupling" indicates the relationship between the changes in the transmission / reception characteristics of each other when the current induced by a given active antenna acts on another adjacent active antenna through coupling. If mutually coupled active antennas are synchronized with each other in the same phase or opposite phase, the mutual injection locking phenomenon causes the electromagnetic fields between the active antennas to strengthen or weaken each other. This can adjust the increase / decrease of the gain of the antenna. Note that in this embodiment, in order to generally represent the coupling line of the coupled active antenna, it is described as coupling line 102. The letters corresponding to the active antenna are used to describe the coupling line that forms the coupling line 102 and couples the antenna. For example, the coupling line of the coupled active antennas 11a and 11d is described as coupling line 102ad.

[0075] The oscillation condition of the antenna array 11 is determined by the condition of mutual injection locking in the arrangement in which two or more individual RTD oscillators are coupled as described in NPL 2. More specifically, the oscillation condition of the antenna array in which the active antennas 11a and 11b are coupled by the coupling line 102ab is considered. At this time, two oscillation modes of positive phase mutual injection locking and negative phase mutual injection locking occur. The oscillation condition of the oscillation mode (even mode) of the positive phase mutual injection locking is expressed by expression (4) and equation (5), and the oscillation condition of the oscillation mode (odd mode) of the negative phase mutual injection locking is expressed by expression (6) and equation (7).

[0076] Positive phase (even mode): frequency f = feven

[0077] Yeven=Y11+Y12+YRTD

[0078] Re(Yeven)≤0...(4)

[0079] Im(Yeven)=0...(5)

[0080] Negative phase (odd mode): frequency f = fodd

[0081] Yodd=Y11+Y12-YRTD

[0082] Re(Yodd)≤0...(6)

[0083] Im(Yodd)=0...(7)

[0084] Wherein Y12 represents the mutual admittance between the active antennas 11a and 11b. Y12 is proportional to the coupling constant representing the coupling strength between the antennas, and ideally, the real part of -Y12 is large and the imaginary part is zero. In the antenna array 11 of this embodiment, the active antennas are coupled under the positive phase mutual injection locking condition, and an oscillation frequency f0≈feven is obtained. Similarly, with respect to the remaining antennas, the antennas are coupled by the coupling line 102 to satisfy the above-mentioned positive phase mutual injection locking condition.

[0085] The coupled line 102 is a microstrip line obtained by sandwiching dielectric layers 118 to 120 by the conductor of the coupled line 102 and the conductor layer 121 or the bias line 105. Figure 4A As shown in FIG. 1 , the coupled line 102ab has a structure in which dielectric layers 118 to 120 are sandwiched by the conductor of the coupled line 102ab and the conductor layer 121 or the bias line 105. Similarly, the coupled line 102bc has a structure in which dielectric layers 118 to 120 are sandwiched by the conductor of the coupled line 102bc and the conductor layer 121 or the bias line 105.

[0086] The antenna array 11 is an antenna array having an arrangement in which antennas are coupled by AC coupling (capacitive coupling). For example, in a plan view, the upper conductor layer ( Figure 4A 102bc) in the coupling line 102 overlaps with the conductor 100 as the patch conductor of each of the active antennas 11b and 11c by sandwiching the dielectric layer 118, and is connected to the conductor 100 by capacitive coupling. More specifically, in a plan view, the conductor of the coupling line 102bc overlaps with the conductor 100 by only 5 μm by sandwiching the dielectric layer 118 near the radiation end of each of the active antennas 11b and 11c, thereby forming each of the capacitor structures C1 and C2. The capacitor structures C1 and C2 are connected to the conductor 100 by the dielectric layer 118 near the radiation end of each of the active antennas 11b and 11c. Figure 3The capacitor C1 and C2 in the circuit diagram shown in correspondence. The capacitor C1 and C2 of this arrangement are used as high-pass filters, and contribute to suppressing multimode oscillation by short-circuiting the electromagnetic waves in the terahertz band and opening the electromagnetic waves with respect to the low-frequency band. However, this arrangement is not necessarily required, and the arrangement of DC coupling can be used so that the conductor of the coupling line 102bc is directly coupled (directly connected) with the conductor 100 of the active antenna 11b and 11c. Since the antenna array synchronized by DC coupling can synchronize adjacent antennas by strong coupling, the antenna array is easy to perform pull-in synchronization operation. It is noted that the coupling between active antenna 11b and 11c has been illustrated, but this is also applicable to the coupling between the remaining active antennas 11a to 11i.

[0087] In the antenna array 11, the conductor 100 of the active antenna, the conductor of the coupling line 102, and the bias line 105 are arranged in different layers. In this way, the conductor 100 of the active antenna and the coupling line 102 that transmits high-frequency (frequency in the terahertz band) electromagnetic waves and the bias wiring layer that transmits low-frequency (DC to tens of GHz) electromagnetic waves can be arranged in different layers. This can freely set the width, length, and layout of the transmission line in each layer, such as wiring. Figure 4A As shown in , when viewed from above (in a plan view), the coupling line 102 and the bias line 105 intersect each other, thereby obtaining a layout-saving arrangement. Even in an antenna array in which antennas are arranged in an m×n (m≥2, n≥2) matrix, this can increase the number of antennas to be arranged.

[0088] It is noted that due to the increase in resistance caused by the skin effect in the terahertz band, the conductor loss caused by high-frequency transmission between antennas cannot be ignored. As the current density between the conductor layers increases, the conductor loss per unit length (dB / mm) increases. In the case of a microstrip line, the conductor loss per unit length (dB / mm) is inversely proportional to the square of the dielectric thickness. Therefore, in order to improve the radiation efficiency of the antenna array, in addition to the antenna, the conductor loss can also be reduced by increasing the thickness of the dielectric forming the coupling line 102. In contrast, the antenna array 11 of this embodiment has an arrangement in which the bias line 105 is arranged in the dielectric layer 120 and the conductor 100 of the antenna that transmits high-frequency electromagnetic waves such as frequencies in the terahertz band and the conductor of the coupling line 102 are arranged in the upper layer of the dielectric layer 119. This arrangement can suppress the decrease in the radiation efficiency of the antenna array and the conductor loss in the terahertz band. From the perspective of conductor loss, the thickness of the dielectric forming the coupling line 102 is preferably 1μm or greater. In the example, the dielectric thickness is set to 2 μm or more, so the loss of conductor loss in the terahertz band is suppressed to about 20%. Similarly, from the viewpoint of conductor loss, a wide interval in the thickness direction between the conductor forming the coupling line 102 and the bias line 105 and the conductor layer 121 can be ensured. By setting the dielectric thickness to 2 μm or less, or 1 μm or less in the example, the bias line 105 can be used as a low impedance line almost up to the gigahertz band. Even if the dielectric thickness is set to 2 μm or more, low-frequency oscillation can be suppressed by connecting a shunt component formed by a resistance layer and a MIM capacitor to the bias line 105 to use it as a low impedance line.

[0089] Note that if adjacent antennas are connected via coupling lines, the length of the conductor of the coupling line 102 is designed to satisfy Figure 3 The coupling line 102 may be designed to have a length such that the electrical length between the RTDs of adjacent antennas is equal to an integer multiple of 2π. That is, the length of the coupling line 102 is set so that the length of the path through the coupling line 102 when the RTDs are connected through the coupling line 102 is equal to an integer multiple of the wavelength of the propagated electromagnetic wave. For example, in Figure 3In the embodiment, the coupling line 102ad extending in the X direction can be set so that the electrical length between the semiconductors 101a and 101d is equal to the length of 4π. In addition, the coupling line 102ad extending in the Y direction can be set so that the electrical length between the semiconductors 101a and 101b is equal to the length of 2π. It is noted that the electrical length indicates the wiring length taking into account the propagation speed of the high-frequency electromagnetic wave propagating in the coupling line 102. The electrical length of 2π corresponds to the length of one wavelength of the electromagnetic wave propagating in the coupling line 102. With this design, the semiconductors 101 of the active antennas 11a to 11i are mutually injection-locked in the positive phase. It is noted that the error range of the electrical length at which mutual injection locking occurs is ±1 / 4π.

[0090] like Figure 3 , Figure 4A and Figure 4B As shown in , the element 12 is formed so that the bias line 105 arranged between the antennas applies a bias to each semiconductor 101 included in the active antennas 11a to 11i forming the antenna array 11. By separating the bias line 105 as wiring in the chip, it can be driven in the same channel, or driven individually by the bias control unit 13, so that the driving method can be controlled. The deviation of the operating point between the antennas caused by changes in thickness or shape caused by formation or wiring resistance, etc. can be adjusted. This can cope with the deviation of the frequency and phase difference between the antennas caused by the increase in the number of active antennas, making it easier to obtain the synchronization effect of the array. Note that the bias line 105 does not need to be always arranged in the same layer, nor does it need to be separated to control all active antennas individually. For example, the bias line can be formed by stacking multiple layers of wiring, as described later. FIG. 10A to FIG. 10C Alternatively, bias lines may be prepared for each column of antennas to apply a common bias to some antennas, as will be described later. Figure 7 In this case, by reducing the power supply device or wiring forming the bias control unit 13, it is possible to save power of the antenna device 10 and simplify the antenna device 10.

[0091] (Bias Control Unit)

[0092] The bias control unit 13 is connected to the control line 106, and has a function of changing the bias to be applied to each of the semiconductors 101a to 101i by a signal received from the beam direction control unit 14. Note that, in order to change the voltage of each semiconductor, the bias control unit 13 may use a separate power supply corresponding to the number of antennas, or use a combination of power supplies whose number is less than the number of antennas, variable voltage devices, variable resistors, transistors, etc. The bias control unit 13 may apply different voltages to the bias lines 105a to 105i in parallel using these functions.

[0093] The admittance (YRTD) of the semiconductor 101 changes depending on the bias. This is because the depletion layer capacitance of the semiconductor 101 changes depending on the bias. Then, as described above, the oscillation frequency f of the active antenna is determined based on the admittance YRTD of the semiconductor 101. THz That is, the oscillation frequency f in an active antenna THz changes depending on the bias applied to the semiconductor 101. Note that as the bias voltage increases, the oscillation frequency f THz becomes higher. The bias to be applied to the active antenna is determined within the range of the negative resistance region of the semiconductor 101, and the amount of change in frequency varies depending on the area of ​​the negative resistance region. The "area of ​​the negative resistance region" indicates the magnitude of the voltage difference between the lower limit value and the upper limit value of the voltage of the negative resistance region. In this embodiment, the bias control unit 13 can perform separate bias control on each active antenna via the bias line 105. Therefore, even if the antenna array 11 includes two or more semiconductors 101 with different areas of negative resistance regions due to dimensional changes, frequency control can be easily performed.

[0094] (Beam direction control unit 14)

[0095] The beam direction control unit 14 is connected to the bias control unit 13 via a control line 106, and has a function of supplying a control signal to the bias control unit 13. The control signal supplied to the bias control unit 13 may be different depending on the device used as the bias control unit 13. For example, in the case where a device used as the bias control unit 13 is formed using a transistor, a voltage signal applied to the gate of the transistor may be supplied from the beam direction control unit 14 to the bias control unit 13 as a control signal. The beam direction control unit 14 may have, for example, an information table that associates the bias applied to each active antenna with the directivity of the beam. In this case, the beam direction control unit 14 may supply such a control signal that sets the applied voltage required for beamforming according to the information table to the bias control unit 13. The beam direction control unit 14 may have an information table that associates the bias applied to each active antenna with the phase expected to be obtained. In this case, for example, the beam direction control unit 14 determines the beam to be formed (the directional direction of the beam) according to the state of the transmission path with the communication partner device, and determines the phase value to be set in each active antenna corresponding to the beam. Then, referring to the information table, the beam direction control unit 14 can specify the bias to be applied for each active antenna so that the phase is the determined phase value, and transmit a control signal corresponding to the specified result to the bias control unit 13.

[0096] Reference Figure 5AThe phase change caused by the bias change in the active antenna is described. The oscillation frequency of a single active antenna is determined by the resistance component and LC component of the semiconductor 101 and the resistance component and LC component caused by the structure of the antenna 100. Since the depletion layer capacitance as the semiconductor characteristic of each of the semiconductors 101a to 101i depends on the applied bias and changes, the oscillation frequency of each of the active antennas 11a to 11i changes according to the applied bias. In this embodiment, as described above, the active antennas 11a to 11i are coupled by coupling lines 102ab to 102hf, and oscillate with identical oscillation frequency f0 by mutual injection locking phenomenon. In this example, for example, it is assumed that the active antenna 11a oscillates with frequency f1 by the applied bias, and then oscillates with frequency f0 by the mutual injection locking phenomenon with the remaining active antennas 11b to 11i.

[0097] The relational expression between the phase and the angular velocity difference between the two oscillators described in NPL 2 is applied to this embodiment. Then, based on Figure 5A The frequency difference between the frequency f0 at which the antenna array 11 shown in FIG. 1 oscillates by mutual injection locking and the oscillation frequency f1 when the active antenna 11a does not perform mutual injection locking, the phase difference of the active antenna 11a is calculated by the following equation:

[0098]

[0099] Note that, represents the oscillation phase of the active antenna 11a, and P1 represents the oscillation power. In addition, P0 represents the oscillation power of the antenna array 11, and Q represents the Q value of the active antenna 11a. As the spectrum becomes sharper, the Q value becomes higher, and the Q value is used as an output index of the oscillation circuit. Figure 5A As shown in It can be changed within the range of -π / 2 to π / 2. In addition, the remaining active antennas 11b to 11i can be similarly oscillated by changing the phase difference.

[0100] Then, as an example, by focusing on Figure 3 The three active antennas 11a to 11c taken along the line A-A' in FIG. Figure 5BDescribe the principle of tilting the beam from the direction perpendicular to the substrate when these active antennas emit electromagnetic waves. For example, assume that the bias control unit 13 gradually increases the bias to be applied to each of the active antennas 11a to 11c in the A-A' direction. That is, assume that the bias to be applied to the active antenna 11a is the lowest, the bias to be applied to the active antenna 11c is the highest, and the bias to be applied to the active antenna 11b is between the two. In this case, the oscillation frequencies f1 to f3 of the corresponding active antennas 11a to 11c have the relationship of f1 < f2 < f3. In this embodiment, as described above, the semiconductors 101a to 101c included in the active antennas 11a to 11c inject power via the coupling lines 102ab and 102bc, and due to the mutual injection locking phenomenon, the oscillation frequency becomes f0. At this time, when the oscillation frequency f2 of a single active antenna 11b is equal to f0, the phase difference of the active antenna 11b after mutual injection locking is 0. On the other hand, based on the oscillation frequencies f1 and f3, the phase difference of the active antenna 11a after mutual injection locking is determined by the above equation (1) and the phase difference of the active antenna 11c In this case, the phase differences between the active antenna 11b and the active antennas 11a and 11c are respectively given by and Suppose the oscillation frequency f2 of a single active antenna 11b is not often equal to f0. In this case, the phase difference of the active antenna 11b is determined similar to the active antennas 11a and 11c Then, the phase differences between the active antenna 11b and the active antennas 11a and 11c are respectively given by and However, The relationship between is important for beamforming, and even if it is assumed that the common of the two expressions is 0, there is no substantial difference. Therefore, set

[0101] Figure 5B shows the direction control of the electromagnetic wave whose phase difference is specified and emitted from the active antennas 11a to 11c as described above. Consider the case where the distance between adjacent active antennas is generally d and the radio wave is output in the direction θ. In order to emit a radio wave in the direction θ, at the moment when the antenna arranged on the leftmost side emits a radio wave with a phase α, the phase of the radio wave emitted from the antenna arranged on the right side of the antenna and traveling a distance d×sinθ in parallel needs to be α. In addition, the phase of the radio wave emitted from the antenna arranged on the rightmost side and traveling a distance 2d×sinθ in parallel also needs to be α. Suppose the phase of the radio wave emitted from the second antenna from the left changes At this time, when λ represents the wavelength of the radio wave, if If the phase difference between adjacent antennas is determined by the following equation, then the radio wave emitted from the second antenna on the left is in phase with the radio wave emitted from the leftmost antenna at a position where the radio wave emitted from the second antenna on the left has traveled a distance of d×sinθ. Therefore, by determining the emission direction θ of the radio wave, the phase difference to be set between adjacent antennas is determined by the following equation:

[0102]

[0103] The phase difference between the second antenna on the left and the rightmost antenna is similarly determined. Therefore, for example, the bias control can be performed so that the beam is oriented toward the direction θ, thereby obtaining Satisfying the above equation (2) and Satisfying the above equation (2) of and That is, based on the predetermined direction θ to which the beam is to be directed, the phase difference to be set between the plurality of active antennas is determined, and the oscillation frequency of the oscillator of each active antenna is set to obtain the phase difference. Note that the direction θ of the antenna can be changed by the shape and type of the antenna and the array arrangement. In this way, the antenna device 10 according to this embodiment can perform beamforming at an arbitrary angle by controlling the bias to be applied to the oscillator (semiconductor 101) included in each active antenna.

[0104] (Actual material and structural dimensions)

[0105] A practical example of the antenna array 11 will be described. The antenna array 11 is a semiconductor device that can perform single-mode oscillation in a frequency band of 0.45 THz to 0.50 THz. The substrate 122 is a semi-insulating InP substrate. The semiconductor 101 is formed of an InGaAs / AlAs multiple quantum well structure lattice-matched to the substrate 122, and an RTD with a double barrier structure is used in this embodiment. This is also referred to as a semiconductor heterostructure of an RTD. As the current-voltage characteristic of the RTD used in this embodiment, the measured value of the peak current density is 9 mA / μm 2 , and the measured value of the differential negative conductance per unit area is 10 mS / μm 2 The semiconductor 101 is formed into a mesa structure and is formed of a semiconductor structure including an RTD and an ohmic electrode for electrically connecting to the semiconductor structure. The mesa structure has a circular shape with a diameter of 2 μm, and the magnitude of the differential negative resistance of the RTD at this time is about -30Ω per diode. In this case, it is estimated that the differential negative conductance (GRTD) of the semiconductor 101 including the RTD is about 30 mS and the diode capacity (CRTD) is about 10 fF.

[0106] The active antenna 11 is a patch antenna having a structure in which dielectric layers 119 and 120 are sandwiched by a conductor 100 as a patch conductor and a conductor layer 121 as a ground conductor. This patch antenna is a square patch antenna in which one side of the conductor 100 is 150 μm, and the resonator length (L) of the antenna is 150 μm. In the antenna, a semiconductor 101 including an RTD is integrated.

[0107] The conductor 100 as a patch conductor is formed of a metal layer mainly including an Au thin film having a low resistivity (metal including Ti / Au (=5 / 300nm)). The conductor layer 121 as a ground conductor is formed of a Ti / Pd / Au layer (20 / 20 / 200nm) and a -3 The dielectric layer 119 is formed of a semiconductor layer of n+-InGaAs layer (100 nm) or larger, and the metal and the semiconductor are connected with a low resistance ohmic contact. The dielectric layer 119 is made of BCB (benzocyclobutene, ε-butylene, Dow Chemical Company) with a thickness of 5 μm. r1 =2). Each of the dielectric layers 118 and 120 is made of silicon oxide (SiO2, plasma CVD, ε r2 =4) was formed, and the total film thickness of the two layers was 2 μm.

[0108] In the periphery of the semiconductor 101, the conductor layer 121, the semiconductor 101, the through hole 114 formed of a conductor including Cu, the conductor 100, and the conductor of the coupling line 102 are stacked in order from the substrate 122 side, and they are electrically connected. The RTD as the semiconductor 101 is arranged in the resonance direction (i.e., Figure 3 The input impedance when a high frequency is supplied from the RTD to the patch antenna is determined based on the position of the RTD in the antenna. Figure 4B As shown in FIG. 1 , the conductor 100 is connected to a wiring 111 existing in the same layer as the bias line 105 arranged on the dielectric 120 via a through hole 110 formed by Cu. The bias line 105 and the wiring 111 are formed by a metal layer containing Ti / Au (=5 / 300nm) stacked on the dielectric layer 120. The wiring 111 is connected to the bias control unit 13 via the bias line 105 as a common wiring formed in the chip. The active antenna is designed to provide a bias control unit 13 at a frequency f by setting a bias in a negative resistance region of the RTD included in the semiconductor 101. THz =0.5THz and an oscillation with a power of 0.2mW is obtained.

[0109] Each of the through holes 110 and 114 has a columnar structure with a diameter of 10 μm. The wiring 111 is formed by a pattern formed by a metal layer containing Ti / Au (=5 / 300 nm) and having a width of 10 μm and a length of 75 μm in the resonance direction (=A-A' direction). The through hole 110 is connected to the conductor 100 at the center of the resonance direction (=A-A' direction) and at the end of the conductor 100 in the CC' direction. This connection position corresponds to the frequency f in the active antenna 11a. THz It corresponds to a node of the electric field of the terahertz standing wave (that is, a position where the amplitude of the standing wave always becomes zero).

[0110] The antenna array 11 is an antenna array in which active antennas are arranged in a matrix. In this embodiment, as an example, an antenna array in which nine active antennas 11a to 11i are arranged in a 3×3 matrix has been described. Each active antenna is designed to have an individual oscillation frequency of f THz The active antennas are arranged at a pitch (interval) of 340 μm in both the A-A' direction and the B-B' direction. Adjacent antennas are coupled to each other through a coupling line 102 comprising a conductor made of Ti / Au (=5 / 300 nm), and the oscillation frequency f is controlled by a bias driven by THz =0.5±0.02THz and oscillate by mutual injection locking.

[0111] (Manufacturing method)

[0112] Next, a manufacturing method (forming method) of the antenna array 11 will be described.

[0113] (1) First, on a substrate 122 made of InP, a semiconductor multilayer film structure based on InGaAs / AlAs is formed by epitaxial growth, which forms a semiconductor 101 including an RTD. This is formed by molecular beam epitaxy (MBE), metal organic vapor phase epitaxy (MOVPE), or the like.

[0114] (2) An ohmic electrode Ti / Pd / Au layer (20 / 20 / 200 nm) of the semiconductor 101 is formed by sputtering deposition.

[0115] (3) The semiconductor 101 is formed into a circular mesa shape having a diameter of 2 μm, thereby forming a mesa structure. To form the mesa shape, photolithography and dry etching by ICP (Inductively Coupled Plasma) are used.

[0116] (4) After forming the conductor layer 121 on the substrate 122 by a lift-off process on the etched surface, silicon oxide is deposited to a thickness of 2 μm by a plasma CVD method to obtain the dielectric layer 120 .

[0117] (5) A Ti / Au layer (=5 / 300 nm) is formed on the dielectric layer 120 as a conductor for forming the bias line 105 and the wiring 111 .

[0118] (6) BCB with a thickness of 5 μm was embedded and planarized using spin coating and dry etching to obtain a dielectric layer 119 .

[0119] (7) The BCB and silicon oxide forming the portions of the through holes 110 and 114 are removed by photolithography and dry etching to form a through hole (contact hole). At this time, by using photolithography including grayscale exposure, the taper angle of the through hole formed in the dielectric layers 119 and 120 can also be arbitrarily controlled.

[0120] (8) The via holes 110 and 114 are formed in the via holes by a conductor including Cu. To form the via holes 110 and 114, Cu is embedded in the via holes and planarized using sputtering, electroplating, and chemical mechanical polishing.

[0121] (9) Electrode Ti / Au layers (=5 / 300 nm) are deposited by sputtering to obtain the conductor 100 of each antenna. The conductor 100 is patterned by photolithography and dry etching by ICP (Inductively Coupled Plasma).

[0122] (10) Silicon nitride is deposited to a thickness of 0.1 μm by a plasma CVD method to obtain a dielectric layer 118. An electrode Ti / Au layer (=5 / 300 nm) is deposited by sputtering to obtain a conductor forming the coupling line 102. The conductor of the coupling line 102 is patterned by photolithography and dry etching by ICP (Inductively Coupled Plasma).

[0123] (11) Finally, the bias line 105 and the bias control unit 13 are connected by wire bonding or the like, thereby completing the antenna array 11.

[0124] Note that the bias control unit 13 supplies power to the antenna device 10. Generally, if a bias is applied to supply a bias current in a differential negative resistance region, the antenna device 10 operates as an oscillator.

[0125] [Second embodiment]

[0126] The above embodiment has explained the arrangement that can individually (independently) control the oscillation frequency of each oscillator included in a plurality of active antennas. This embodiment will describe the arrangement that groups some active antennas and performs common control on the active antennas. Figure 6 is a block diagram for explaining the system configuration of the antenna device 20 according to this embodiment, and Figure 72 is a schematic plan view showing the antenna device 20 when viewed from above. Note that, for simplicity of description, detailed description of the same components as those of the antenna device 10 among the components of the antenna device 20 according to this embodiment will be omitted.

[0127] like Figure 6 As shown in, similar to the antenna device 10 of the first embodiment, the antenna device 20 of this embodiment includes an element 22, which includes an antenna array 21 in which active antennas 21a to 21i are arranged in an array, a bias control unit 23 and a beam direction control unit 24. These functions are roughly the same as those in the antenna device 10 of the first embodiment. That is, the beam direction control unit 24 is connected to the bias control unit 23 via a control line 206, and supplies a control signal to the bias control unit 23 so that the beam is directed to a predetermined direction. The bias control unit 23 is configured to supply a bias to each of the oscillators 201a to 201i included in the active antennas 21a to 21i via each bias line 205. The active antennas 21a to 21i include oscillators 201a to 201i and antennas 200a to 200i, respectively.

[0128] In this embodiment, a first group of antennas are connected to each other through a coupling line 202 for mutual injection locking and a second group of antennas are provided to control their oscillation frequencies together. For example, assuming that nine active antennas 21a to 21i are arranged in a 3×3 matrix, as shown in FIG. Figure 7 At this time, the active antennas arranged in the X direction are coupled through the coupling line 202 to establish synchronization through mutual injection locking, and the active antennas arranged in the Y direction are subjected to common oscillation frequency control using a common bias line. Figure 7 In the example shown in, active antenna 21a, 21d and 21g use coupling lines 202ad and 202dg to couple with each other. Similarly, active antenna 21b, 21e and 21h use coupling lines 202be and 202eh to couple with each other, and active antenna 21c, 21f and 21i use coupling lines 202cf and 202fi to couple with each other. Then, mutual injection locking is established between each active antenna coupled by coupling lines. On the other hand, active antenna 21a, 21b and 21c are connected to common bias line 205a. Active antenna 21d, 21e and 21f are connected to common bias line 205d, and active antenna 21g, 21h and 21i are connected to common bias line 205g.

[0129] As described above, when the synchronization of the oscillation frequency is established by mutual injection locking, the active antennas arranged in the X direction transmit radio waves at the same frequency. On the other hand, when the active antennas arranged in the Y direction use a common bias line 205, the phase difference between the active antennas coupled by the coupling line 202 can be made common. That is, the active antennas 21a, 21d and 21g are mutually injection locked at the oscillation frequency f 01 When the active antennas 21b, 21e and 21h are oscillated, the oscillation phase difference between them is appropriately set, so that the beam can be directed to any direction on the XZ plane. Note that Z represents an axis in the direction from back to front, which intersects the XY plane perpendicularly, and the XZ plane is a plane specified by the X-axis and the Z-axis. In addition, the relationship between the oscillation phase difference and the beam direction is determined according to the above equation (2). In addition, the active antennas 21b, 21e and 21h can be mutually injection locked at an oscillation frequency f 02 When oscillating, the beam is directed in the same direction as the beam formed by active antennas 21a, 21d and 21g in the XZ plane. That is, since the bias line 205 is common, the phase difference between active antennas 21b and 21e is equal to the phase difference between active antennas 21a and 21d. Similarly, the phase difference between active antennas 21e and 21h is equal to the phase difference between active antennas 21d and 21g. Similarly, active antennas 21c, 21f and 21i can be mutually injection locked at an oscillation frequency f 03 When oscillating, the beam is oriented in the same direction as the beam formed by the active antennas 21a, 21d and 21g in the XZ plane. It is noted that in an environment where the individual differences of the oscillator 201 are sufficiently small, for example, in the three antenna groups of the active antennas 21a to 21c, the active antennas 21d to 21f and the active antennas 21g to 21i, the active antennas oscillate at almost the same oscillation frequency. Therefore, the oscillation frequency f after mutual injection locking is 01 to f 03 In addition, even in an environment where there are certain individual differences, for example, by averaging in the active antenna group that is the target of mutual injection locking, the oscillation frequency f after mutual injection locking is expected to be 01 to f 03 Almost the same.

[0130] As described above, three groups each including three active antennas arranged in the X direction operate to make the beams face the same direction by applying a bias to each group of active antennas arranged in the Y direction. As a result, for example, the antenna device can be used in an environment where it is only necessary to control the beam direction on the XZ plane and to form the element 22 with a relatively simple arrangement. By reducing the coupling line 202 formed to reduce the power consumption in the coupling line 202, the power consumption in the entire antenna device 20 can be suppressed. In addition, since the number of targets to be controlled by the bias control unit 23 is reduced, the power supply and power supply circuit of the bias control unit 23 can be reduced, thereby reducing the weight of the antenna device 20.

[0131] Note that if Figure 8 As shown in , three groups each including three active antennas arranged in the Y direction are configured to operate so that the beam is oriented in the same direction by the bias of each group of active antennas arranged in the X direction. With this arrangement, the direction of the beam on the YZ plane can be controlled. Generally speaking, in an antenna array in which active antennas are arranged in a matrix, the active antennas arranged in a first direction are coupled by coupling lines, and the active antennas arranged in a second direction different from the first direction are not coupled by coupling lines. This synchronizes the oscillation frequency of the active antenna only by mutual injection locking between each active antenna arranged in the first direction. In addition, the oscillation frequency before synchronization is made common to the active antenna arranged in the second direction. This can make the oscillation frequency before the mutual injection locking caused by the coupling in the first direction common to the active antenna arranged in the second direction. Therefore, in the case of forming a plurality of groups each including an active antenna arranged in the first direction, a plurality of groups can make the beam oriented in the same direction on a plane including the first direction and a direction perpendicular to the antenna device.

[0132] [Third embodiment]

[0133] Each of the above embodiments has explained an example in which an element is formed on one substrate. This embodiment will describe an example in which an element is formed by combining a plurality of substrates. Fig. 9 is a schematic plan view of the element 42 according to this embodiment. FIG. 10A to FIG. 10C is a cross-sectional view of the element 42. Note that, in order to simplify the description, a detailed description of the same components as those of the antenna device 10 will be omitted.

[0134] like Fig. 9As shown in , element 42 also includes an antenna array, in which nine active antennas 41a to 41i, each including a conductor 400 and a semiconductor 401, are arranged in a 3×3 matrix. Similar to each of the above embodiments, the active antennas 41a to 41i are interconnected via coupling lines 402 and are configured to synchronize the oscillation frequency by mutual injection locking. Each active antenna includes a through hole 437, an opening 436, a MIM capacitor 426, a resistive layer 427, and a bias line 408.

[0135] Reference FIG. 10A to FIG. 10C Describe separately Fig. 9 The layer arrangement of the A-A' section, the B-B' section and the CC' section in the active antenna 41a to 41i. Each of the active antennas 41a to 41i includes at least a conductor 400 as the upper conductor of the patch antenna, a conductor 409 used as a GND layer and a reflector layer, and a semiconductor 401 arranged therebetween. It is noted that the semiconductor 401 is a compound semiconductor, and a resonant tunneling diode (RTD) is used as a semiconductor structure 462, for example. Each of the active antennas 41a to 41i also includes a through hole 403 for connection between the conductor 400 and the semiconductor 401. In addition, an upper conductor of a coupling line 402 for coupling the conductor 400 of the active antenna is also arranged. A bias line 408 is arranged between the conductors 400 and 409, and the bias line 408 is located at a midpoint between the dielectric layers 404 and 405. The bias line 408 is connected to the conductor 400 via a through hole 407. In addition, the conductor 409 used as the GND layer is grounded.

[0136] In the semiconductor 401, an upper electrode layer 463, a semiconductor structure 462, and a lower electrode layer 464 are stacked in order from the conductor 400 side, and they are electrically connected. The semiconductor structure 462 is a semiconductor structure having an electromagnetic wave gain or nonlinearity relative to a terahertz wave, and RTD is used in this embodiment. The upper electrode layer 463 and the lower electrode layer 464 have a structure used as an electrode layer for connecting contact electrodes (ohmic and Schottky electrodes) above and below the semiconductor structure 462 and upper and lower wiring layers so as to apply a potential difference or current to the semiconductor structure 462. The upper electrode layer 463 and the lower electrode layer 464 can be made of a metal material (Ti / Pd / Au / Cr / Pt / AuGe / Ni / TiW / Mo / ErAs, etc.) called an ohmic electrode or a Schottky electrode or a semiconductor doped with impurities.

[0137] An active antenna is formed by a conductor 400 of the antenna, a semiconductor 401, a conductor 409 (reflector), dielectric layers 404 and 405, and a via 403 connecting the conductor 400 and the semiconductor 401. In order to apply a control signal to the semiconductor 401, a bias line 408, a via 407, a MIM capacitor 426, and a resistance layer 427 provided individually for each active antenna are connected to the active antenna, as shown in FIG. Fig. 10B and Fig. 10C The MIM capacitor 426 is a capacitive element sandwiching a dielectric layer by a metal element, and is arranged to suppress low-frequency parasitic oscillations caused by the bias circuit. The active antennas are connected by coupling lines 402 to establish synchronization between the antennas at terahertz frequencies.

[0138] A bonding surface BS is provided on the lower surface of the first substrate 451 on which the antenna array and the semiconductor are integrated, and the first substrate 451 is bonded to the second substrate 452 including the integrated circuit via the bonding surface BS. At this time, "bonding" is defined as the first substrate 451 and the second substrate 452 sharing the same bonding surface BS. The bonded second substrate 452 is formed by including a second semiconductor substrate as a base material and an integrated circuit region forming a driving circuit. By metal bonding such as Cu-Cu bonding, such as SiO x -SiO x The bonding is performed by insulator bonding such as bonding, adhesive bonding using an adhesive such as BCB, hybrid bonding which is a combination of these, etc. As the bonding process, low-temperature bonding using plasma activation or conventional heat compression bonding is used. A method of bonding semiconductor wafers of the same size, a method of bonding semiconductor wafers of different sizes, a method of bonding a plurality of semiconductor chips separately to a wafer (tiling), etc. are used.

[0139] In the antenna array 41, as the dielectric layer 431 of the first substrate 451 on which the semiconductor 401 is integrated, a semi-insulating InP substrate (4 inches) as a compound semiconductor substrate on which the semiconductor 401 is crystal-grown is used. In this embodiment, the dielectric layer 431 will sometimes be referred to as "compound semiconductor substrate 431" hereinafter. From the perspective of reducing wiring inductance, the thickness of the compound semiconductor substrate 431 is 100 μm or less, and 10 μm or less in the example. The plate thickness is the wavelength of the terahertz wave to be operated or less, typically λ / 10 or less, and λ / 20 or less in the example. A bonding surface BS is provided on the lower surface of the compound semiconductor substrate 431 as the base material of the first substrate 451, and a second substrate 452 including an integrated circuit is bonded. In this embodiment, as an example, a composite material using Cu-Cu bonding and SiO x -SiO x The hybrid bonding of the bonding is a tiling method of bonding the cut first substrate 451 to a 12-inch Si integrated circuit substrate.

[0140] In the first substrate 451, a dielectric layer 448, a compound semiconductor substrate 431, a conductor 409, a dielectric layer 405, a dielectric layer 404, and a dielectric layer 412 are stacked in order from the side of the bonding surface BS with the second substrate 452. In the dielectric layers 405 and 404, through holes 403 and 407, a conductor 400, and a bias line 408 are formed. In the dielectric layer 412, a conductor of the coupling line 402 is formed. The surface on the bonding surface BS side of the first substrate 451 and the second substrate 452 is arranged at a position opposite to the semiconductor 401 across the conductor 409 as a reflector. A through hole 437 extending through the InP semiconductor 431 is formed in the compound semiconductor substrate 431. As a material of the through hole 437, for example, Cu or Au is used. The dielectric layer 448 and the electrode layer 438 for bonding are flattened at the bonding surface BS, and undergo bonding processing in a state where the flat bonding surface BS is exposed. In the second substrate 452, the second semiconductor substrate 434 as a base material and the dielectric layer 432 are stacked in this order, and the conductor 440, the through hole 441, and the bonding electrode layer 439 forming the multilayer wiring are formed in the dielectric layer 432. The dielectric layer 432 and the electrode layer 439 are flattened at the bonding surface BS, and are subjected to a bonding process in a state where the flat bonding surface BS is exposed. For the dielectric layers 432 and 448, a material such as silicon oxide (SiO x ), silicon nitride (Si x N y ), inorganic insulating materials such as silicon oxynitride (SiON), carbon-containing silicon oxide (SiOC) or silicon carbide (SiC).

[0141] refer to Fig. 10A , the conductor 409 is electrically connected to the through hole 437g formed in the compound semiconductor substrate 431 and the bonding electrode layer 437g formed in the dielectric layer 448 in sequence to reach the bonding surface BS. In addition, the conductor 440 as the GND of the second substrate 452 is connected to the through hole 441g formed in the integrated circuit region 454 and the bonding electrode layer 439g in sequence to reach the bonding surface BS. The electrode layer 438g of the first substrate 451 and the electrode layer 439g of the second substrate 452 are electrically connected at the bonding surface BS, thereby sharing the GND potential of the two substrates.

[0142] refer to Fig. 10B, the bias line 408 connected to the semiconductor 401 of the first substrate 451 is electrically connected to the transistor TRb (MOSFET) for bias control provided in the integrated circuit region 454 of the second substrate 452. The bias line 408 of the first substrate 451 is electrically connected to the through hole 407, the wiring layer 435 provided in the opening 436 of the conductor 409, the through hole 437b, and the bonding electrode layer 438b formed in the dielectric layer 448 in sequence to reach the bonding surface BS. Similarly, the transistor TRb formed in the integrated circuit region 454 of the second substrate 452 is connected to the through hole 441b formed in the integrated circuit region 454 and the bonding electrode layer 439b in sequence to reach the bonding surface BS.

[0143] refer to Fig. 10C In order to apply a control signal to the semiconductor 401, a bias line 408, a via 407, a via 414, a MIM capacitor 426 and a resistance layer 427 provided separately for each antenna are connected to the first substrate 451. The MIM capacitor 426 is formed by sandwiching a dielectric layer by a conductor 413 and a conductor 409 as a GND layer. Similarly, a MIM capacitor 455 is provided in the second substrate 452.

[0144] The bias line 408 of the antenna array and the transistor TRa of the integrated circuit region 454 are electrically connected at the bonding surface BS and made conductive, so that a control signal can be applied to each active antenna individually. The MOSFET of the transistor TRb also serves as a bias control unit and operates as a switching regulator, so that the bias to the semiconductor 401 can be controlled individually via the bias line 408. Alternatively, an arrangement may be adopted in which a terminal for applying a bias is additionally provided on the second substrate 452, and the transistor TRa operates as an analog switch that individually switches the on / off of the bias to the active antenna to supply a voltage from the outside of the second substrate 452.

[0145] Note that, as an example of enhancing the bonding strength, dummy electrode layers 438d and 439d that are not connected to the signal line can be provided on the bonding surface BS. By widely distributing the dummy electrode layers 438d and 439d in the area where the wiring electrode is unnecessary, the bonding strength can be enhanced, thereby improving the yield and reliability. In addition, by widely distributing and arranging the GND electrode layers 438g and 439g and the dummy electrode layers 438d and 439d on the entire bonding surface BS, the influence of the electromagnetic wave noise caused by the integrated circuit of the second substrate 452 on the terahertz antenna of the first substrate 451 can be reduced.

[0146] In an active array antenna of terahertz waves, in order to individually control each antenna, multiple wirings are necessary, such as bias lines for powering compound semiconductors, coupling lines for synchronization between antennas, and control lines for injecting baseband signals into antennas. On the other hand, in order to improve the gain of the antenna, it is necessary to increase the number of antennas, but the wiring inductance caused by the layout increases with the increase in the number of antennas, thereby interfering with the implementation of high frequency. In contrast, in this embodiment, an antenna substrate (first substrate 451) of a compound semiconductor including an antenna array and a Si integrated circuit substrate 452 are stacked by semiconductor bonding technology. This eliminates the need to integrate or externally connect the peripheral circuits necessary for controlling the active antenna array to the implementation form on the compound semiconductor substrate. This can suppress the increase in inductance caused by wiring routing, and generally suppresses the inductance to 1nH or less, thereby suppressing the signal loss or signal delay of the baseband signal subjected to modulation control at a high frequency of 1GHz or more.

[0147] Since there is no circuit unrelated to the transmission / reception of terahertz waves in the periphery of the active antenna or the number of such circuits can be made sufficiently small, the noise caused by unnecessary reflection is reduced, so that the characteristics of the antenna can be maximized. If the bias signal of the compound semiconductor or the like is controlled for each antenna, each bias wiring needs to be arranged separately. In contrast, in this embodiment, the first substrate 451 including the antenna array can be directly connected to the integrated circuit of the second substrate 152 via the through hole 437. If an antenna array is used, the wiring can be arranged on the back side of the antenna substrate (first substrate 451) of the compound semiconductor including the antenna array (i.e., the back side of the conductor 409 as a reflector). Therefore, the number of active antennas included in the antenna array can be increased without being affected by the layout. In addition, the second substrate 452 including the integrated circuit can form a complex circuit such as a detection circuit or a signal processing circuit using conventional CMOS integrated circuit technology. Therefore, by using the arrangement described in this embodiment, the antenna device can be made more advanced and cost-effective, so that it is easy to use electromagnetic waves in the terahertz band.

[0148] [Fourth embodiment]

[0149] Reference Figures 11 to 13A and Fig. 13B Another arrangement of antenna device 50 is described. Fig.11 is a block diagram for explaining the system configuration of the antenna device 50. Fig.12 is a schematic plan view showing the antenna device 50 when viewed from above. Fig.13A and Fig. 13B is a cross-sectional view of element 52. Note that Figures 11 to 13A and Fig. 13B, for simplicity of description, a detailed description of the same components as the antenna device 10 will be omitted.

[0150] like Fig.11 As shown in, the antenna device 50 includes an element 52, which includes an antenna array 51, wherein active antennas 51a to 51i are arranged in the array, and each active antenna 51a to 51i includes an antenna 500 and a semiconductor 501 as an oscillator. The antenna device 50 also includes a bias control unit 53 to be electrically connected to the element 52 and a beam direction control unit 54 that supplies a signal to the bias control unit 53 via a control line 506. It is noted that in this embodiment, the antennas included in the active antennas 51a to 51i are also coupled to each other through coupling lines and are configured to cause a mutual injection locking phenomenon. The element 52 of this embodiment also includes oscillation units 55a to 55i, each of which oscillates terahertz waves and is electrically connected to the active antennas 51a to 51i, respectively. Each of the oscillation units 55a to 55i is electrically connected to a corresponding one of the active antennas 51a to 51i. Furthermore, the oscillation units 55a to 55i are electrically connected to the bias control unit 53 via bias lines 505a to 505i, respectively, and the bias control unit 53 supplies a bias to each of the oscillation units 55a to 55i individually. Furthermore, the bias control unit 53 supplies a common bias to the semiconductors 501a1 to 501i1.

[0151] The oscillation units 55a to 55i are formed of, for example, microstrip line resonators and include semiconductors 501a2 to 501i2 and resonant units 525a to 525i, respectively. Fig.13A and Fig. 13B For example, by focusing on Fig.13A The active antenna 51a shown in FIG. 5, the oscillation unit 55a connected to the active antenna 51a includes a semiconductor 501a2 and a resonance unit 525a, which are connected through a through hole 514a2. Fig. 13B In the active antenna 51i shown in FIG. 5 , the resonant unit 525i is connected to the bias control unit 53 via the through hole 524i2 and the bias line 505i. Note that the through holes 524a2 to 524i2 are vertical structures for electrically connecting the bias lines 505a to 505i to the resonant units 525a to 525i. In addition to the role of a member forming a microstrip line resonator, the resonant units 525a to 525i are also connected to the through holes 524a1 to 524i1 to serve as electrodes for injecting current into the semiconductors 501a2 to 501i2.

[0152] In an example, each of the through holes 524a1 to 524i1 may be disposed in each of the resonant units 525a to 525i to oscillate at a frequency f THzAt the node of the electric field of the electromagnetic wave standing wave. At this time, the through holes 524a1 to 524i1 and the bias lines 505a to 505i are configured so that the impedance is sufficiently higher than the absolute value of the differential negative resistance of the semiconductors 501a2 to 501i2 in the frequency band around the oscillation frequency f0. In other words, the through holes 524a1 to 524i1 and the bias lines 505a to 505i are connected to the resonant units 525a to 525i, thereby obtaining a high impedance when viewed from the semiconductor (RTD) at the oscillation frequency f0.

[0153] The active antennas 51a to 51i are biased by a common bias line 505 and thus operate at the same frequency f THz Oscillate. On the other hand, the oscillation units 55a to 55i are biased by different bias lines, so they oscillate with different frequencies f1 to f9 respectively. In the combination of active antennas 51a to 51i and corresponding oscillation units 55a to 55i, active antennas 51a to 51i and oscillation units 55a to 55i oscillate with frequencies f1' to f9' respectively via coupling lines 502a to 502i by mutual injection locking. Even between each active antenna 51a to 51i, mutual injection locking occurs via coupling lines 502ab to 502hi, and antenna array 51 oscillates with frequency f0. Active antennas 51a to 51i oscillate with phase differences determined based on the frequency difference between frequency f0 and oscillation frequency f1' to f9' respectively, without mutual injection locking. This allows antenna array 51 to transmit a terahertz wave TW with an oscillation frequency f0 at an arbitrary angle to the vertical direction of the substrate.

[0154] Then, reference will be made to Fig.12 , Fig.13A and Fig. 13B An example of arrangement and structure on the element 52 is described in detail. The bias line 505 electrically connected to the antennas 500a to 500i is shared by the active antennas 51a to 51i. In the example, the bias voltage is supplied from the bias control unit 53 outside the semiconductor substrate to the active antenna 51a to 51i. Fig.12 The bias line 505 shown in FIG. 52 includes oscillation units 55a to 55i corresponding to the active antennas 51a to 51i, respectively. Each of the oscillation units 55a to 55i has an arrangement including, for example, a microstrip line resonator, and includes a semiconductor such as an RTD and a resonant unit. Fig.13AAs shown in , semiconductors 501a to 501i are electrically connected to conductor 521 as a GND conductor, and are also electrically connected to corresponding antennas 500a to 500i via through holes 514a1 to 514i1, respectively. In addition, semiconductors 501a2 to 501i2 of oscillation units 55a to 55i are electrically connected to conductor 521, and are also electrically connected to resonance units 525a to 525i via through holes 514a2 to 514i2, respectively. Resonance units 525a to 525i are electrically connected to bias lines 505a to 505i via feeding through holes 524a to 524i, respectively, for applying bias voltage to semiconductors 501a2 to 501g2. For example, the bias voltage is supplied by a bias control unit 53 outside element 52 via bias lines 505a to 505i. The bias lines 505a to 505i are connected to the vias 524a to 524i, and are connected to the resonant units 525a to 525i and the vias 514a1 to 514i1. The bias voltage is supplied to the RTDs 501a2 to 501g2 via these connections.

[0155] The through holes 514a2 to 514i2 and the through holes 524a to 524i connected to the resonant units 525a to 525i are connection parts for electrically and mechanically connecting the bias lines 505a to 505i to the resonant units 525a to 525i and the semiconductors 501a2 to 501i2. In addition to the role as a member forming a microstrip line resonator, the resonant units 525a to 525i are also connected to these through holes to serve as electrodes for injecting current into the semiconductors 501a2 to 501g2. In an example, the positions of the through holes 524a to 524i can be arranged at the nodes of the electric field of the standing waves of the electromagnetic waves of the oscillation frequencies f1 to f9 in the resonant units 525a to 525i, respectively. At this time, the through holes 524a to 524i and the resonant units 525a to 525i are configured so that the impedance is sufficiently higher than the absolute value of the differential negative resistance of the semiconductors 501a2 to 501g2 as RTDs in the frequency band around the frequencies f1 to f9. In other words, the through holes 524a to 524i and the bias lines 505a to 505i are connected to the resonant units 525a to 525i so as to THz A high impedance is obtained when viewed from the semiconductor (RTD).

[0156] The coupling lines 502a to 502i are arranged between the antennas 500a to 500i and the resonant units 525a to 525i. The coupling lines 502a to 502i transmit the signals oscillating in the oscillation units 55a to 55i to the active antennas 51a to 51i, respectively. Since each signal oscillates at a frequency in the terahertz band, for example, it is necessary to design the line width, thickness, and line length of each of the coupling lines 502a to 502i as correctly as possible. Therefore, these can be formed by a pattern on the substrate 522. Reference Fig.13A, the coupling lines 502a to 502i are not directly coupled between the resonant units 525a to 525i and the antennas 500a to 500i, and are connected by capacitive coupling. It is sufficient to transmit only the high-frequency component of the signal to be transmitted, and only the AC (alternating current) component is transmitted without transmitting any DC (direct current) component. Note that a capacitive coupling portion may be provided in the middle of each of the coupling lines 502a to 502i.

[0157] exist Fig.13A and Fig. 13B In the embodiment, insulators and dielectric layers 518 to 520 are arranged around semiconductors 501a1 to 501i1 or 501a2 to 501i2, antennas 500a to 500i, resonant units 525a to 525i, and coupling lines 502a to 502i. By properly arranging the insulators and dielectric layers, the insulation between the antennas or resonant units is ensured, and the dielectric constant around the antennas or resonant units is adjusted. Since the dielectric constant is associated with the wavelength of the high-frequency signal of the microstrip line passing through the antenna or resonant unit, the dielectric constant is an important parameter. When the dielectric constant is appropriately adjusted, the performance of the antenna device 50 can be fully obtained.

[0158] As described above, the antenna device 50 of this embodiment includes an oscillation unit, which injects power into each active antenna to synchronize the frequency. Utilizing this arrangement, compared with the power injection between the active antennas, power can be injected into the active antenna with relatively high power. This may result in a certain change in the phase difference with a relatively small frequency difference in the above equation (2). This can easily adjust the phase, thereby efficiently performing beamforming. In this embodiment, since the phase difference is changed without changing the bias to be applied to the active antenna, the change of the oscillation power between the active antennas can be suppressed and an electromagnetic wave with greater power can be emitted.

[0159] [Fifth embodiment]

[0160] This embodiment will describe a case where the antenna device of one of the above-described embodiments is applied to a terahertz camera system (imaging system). Fig.14A The following description is provided. The terahertz camera system 1100 includes a transmission unit 1101 that transmits terahertz waves and a receiving unit 1102 that detects terahertz waves. In addition, the terahertz camera system 1100 includes a control unit 1103 that controls the operations of the transmission unit 1101 and the receiving unit 1102 based on an external signal, processes an image based on the detected terahertz wave, or outputs the image to the outside. The antenna device of each embodiment can be used as the transmission unit 1101 or the receiving unit 1102.

[0161] The terahertz wave emitted from the transmitting unit 1101 is reflected by the object 1105 and detected by the receiving unit 1102. The camera system including the transmitting unit 1101 and the receiving unit 1102 may also be referred to as an active camera system. Note that in a passive camera system not including the transmitting unit 1101, the antenna device of each of the above embodiments may be used as the receiving unit 1102.

[0162] By using the antenna device of each of the above-described embodiments that can perform beamforming, the detection sensitivity of the camera system can be improved, thereby obtaining a high-quality image.

[0163] [Sixth embodiment]

[0164] This embodiment will describe a case where the antenna device of one of the above-described embodiments is applied to a terahertz communication system (communication device). Fig. 14B The following description is provided. The antenna device can be used as an antenna 1200 of a communication system. As a communication system, a simple ASK method, a superheterodyne method, a direct conversion method, etc. are assumed. A communication system using a superheterodyne method includes, for example, an antenna 1200, an amplifier 1201, a mixer 1202, a filter 1203, a mixer 1204, a converter 1205, a digital baseband modulator-demodulator 1206, and local oscillators 1207 and 1208. In the case of a receiver, a terahertz wave received via the antenna 1200 is converted into an intermediate frequency signal by the mixer 1202, and then converted into a baseband signal by the mixer 1204, and an analog waveform is converted into a digital waveform by the converter 1205. Afterwards, the digital waveform is demodulated in the baseband to obtain a communication signal. In the case of a transmitter, after the communication signal is modulated, the communication signal is converted from a digital waveform to an analog waveform by the converter 1205, frequency-converted via mixers 1204 and 1202, and then output from the antenna 1200 as a terahertz wave. The communication system using the direct conversion method includes an antenna 1200, an amplifier 1211, a mixer 1212, a modulator-demodulator 1213, and a local oscillator 1214. In the direct conversion method, the mixer 1212 directly converts the received terahertz wave into a baseband signal when receiving, and the mixer 1212 converts the baseband signal to be transmitted into a signal in the terahertz band when transmitting. The remaining components are the same as those in the superheterodyne method. The antenna device according to each of the above-mentioned embodiments can perform beamforming of terahertz waves by electrical control of a single chip. Therefore, radio waves can be aligned between a transmitter and a receiver. By using the antenna device of each of the above-mentioned embodiments that can perform beamforming, in a communication system, radio quality such as a signal-to-noise ratio can be improved, and a large amount of information can be transmitted in a wide coverage area at a low cost.

[0165] [Other embodiments]

[0166] The embodiments of the present invention have been described above. However, the present invention is not limited to these embodiments, and various modifications and changes can be made within the spirit and scope of the present invention.

[0167] For example, in each of the above embodiments, a method for controlling the phase difference between multiple active antennas by changing the bias applied to the RTD has been described. However, this embodiment is not limited thereto. That is, any antenna device can be formed, which is configured to control the phase difference by controlling the oscillation frequency of each oscillator when active antennas each including an oscillator are arranged in an array and the oscillators are synchronized with each other by mutual injection locking. In general, this antenna device includes: a first active antenna, the first active antenna including a first oscillator and a first antenna conductor; a second active antenna, the second active antenna including a second oscillator and a second antenna conductor; and a coupling line coupling the first antenna conductor and the second antenna conductor. Then, this antenna device includes at least a terminal (input line) for enabling the first oscillation frequency of the first oscillator and the second oscillation frequency of the second oscillator to be individually controlled. By enabling the first oscillation frequency and the second oscillation frequency to be individually controlled, the phase difference between the active antennas can be generated according to the above equation (2), so that the control can be performed so that the beam is oriented in an arbitrary direction. Note that this antenna device can be formed as an antenna module integrated with the bias control unit 13, for example.

[0168] In addition, in each of the above-mentioned embodiments, an example of a case where the antenna conductors included in two active antennas arranged at adjacent positions in the array arrangement among a plurality of active antennas are coupled has been explained, but the present invention is not limited thereto. As long as wiring is possible, two antenna conductors included in two active antennas that are not adjacent to each other may also be coupled.

[0169] In addition, each of the above embodiments has explained a method of forming an antenna device using a stacked structure, but the present invention is not limited thereto. That is, the above discussion can be applied to an antenna device that does not use a stacked structure. In this case, for example, the above semiconductor 101 can be replaced by a semiconductor structure or an arbitrary oscillating device. By Figure 2 By designing another structure according to the circuit diagram shown in , an antenna device having the same performance as the antenna device described in the embodiment can be obtained.

[0170] Each of the above embodiments assumes that the carriers are electrons. However, the present invention is not limited thereto, and holes can be used. In addition, the materials of the substrate and the dielectric are selected according to the application, and semiconductor layers such as silicon, gallium arsenide, indium arsenide, gallium phosphide, glass, ceramics, and resins such as polytetrafluoroethylene or polyethylene terephthalate can be used.

[0171] In each of the above embodiments, a square patch antenna is used as a terahertz wave resonator, but the shape of the resonator is not limited thereto. For example, a resonator having a structure using a patch conductor of a polygonal shape such as a rectangular shape or a triangular shape, a circular shape, an elliptical shape, etc. may be used.

[0172] The number of differential negative resistance elements integrated in the element is not limited to one, and a resonator including a plurality of differential negative resistance elements can be used. The number of lines is not limited to one, and an arrangement including a plurality of lines can be used. By using the antenna device described in each of the above embodiments, terahertz waves can be oscillated and detected.

[0173] In each of the above-mentioned embodiments, a double barrier RTD made of InGaAs / AlAs grown on an InP substrate is described as an RTD. However, the present invention is not limited to the structure and material system, and even another combination of structure and material can provide elements of the present invention. For example, an RTD with a triple barrier quantum well structure or an RTD with a multi-barrier quantum well structure of four or more barriers can be used.

[0174] As the material of the RTD, each of the following combinations can be used.

[0175] ·GaAs / AlGaAs, GaAs / AlAs and InGaAs / GaAs / AlAs formed on GaAs substrate

[0176] InGaAs / InAlAs, InGaAs / AlAs and InGaAs / AlGaAsSb formed on InP substrate

[0177] InAs / AlAsSb and InAs / AlSb formed on InAs substrate

[0178] ·SiGe / SiGe formed on Si substrate

[0179] The above-mentioned structure and material can be appropriately selected depending on the desired frequency and the like.

[0180] [Overview of Embodiments]

[0181] At least some of the above embodiments are summarized as follows.

[0182] (Item 1)

[0183] An antenna device for generating or detecting electromagnetic waves, characterized by comprising:

[0184] A first active antenna, comprising a first oscillator and a first antenna;

[0185] A second active antenna, comprising a second oscillator and a second antenna;

[0186] a coupling line configured to couple the first antenna and the second antenna;

[0187] a first terminal configured to receive a signal for controlling a first oscillation frequency of the first oscillator before synchronization through the coupling line; and

[0188] The second terminal is configured to receive a signal for controlling a second oscillation frequency of the second oscillator independently of the first oscillation frequency before synchronization through the coupling line.

[0189] (Item 2)

[0190] The antenna device according to item 1 is characterized in that, for the coupling line, a length of a path when the first oscillator and the second oscillator are connected via the coupling line is set based on an electrical length of an electromagnetic wave in the coupling line.

[0191] (Item 3)

[0192] The antenna device according to item 2 is characterized in that, for the coupled line, the length of the path is set to be equal to the electrical length of the electromagnetic wave which is an integral multiple of 2π.

[0193] (Item 4)

[0194] The antenna device according to any one of items 1 to 3 is characterized in that each of the first oscillator and the second oscillator is a semiconductor structure including a negative resistance element.

[0195] (Item 5)

[0196] The antenna device according to item 4 is characterized in that the negative resistance element is a resonant tunneling diode.

[0197] (Item 6)

[0198] The antenna device according to item 4 or 5 is characterized in that the semiconductor structure of the first oscillator and the semiconductor structure of the second oscillator have the same shape.

[0199] (Item 7)

[0200] The antenna device according to any one of items 4 to 6 is characterized in that

[0201] The first oscillation frequency is determined based on a magnitude of a bias to be applied to the first oscillator, and the first terminal is a terminal configured to receive the bias to be applied to the first oscillator, and

[0202] The second oscillation frequency is determined based on a magnitude of a bias to be applied to the second oscillator, and the second terminal is a terminal configured to receive the bias to be applied to the second oscillator.

[0203] (Item 8)

[0204] The antenna device according to item 7 is characterized in that a bias having a magnitude in a negative resistance region of the negative resistance element is applied to each of the first oscillator and the second oscillator.

[0205] (Item 9)

[0206] The antenna device according to any one of items 1 to 8, characterized in that the first oscillation frequency and the second oscillation frequency are set based on a phase difference between electromagnetic waves to be obtained by the first active antenna and the second active antenna after synchronizing the oscillation frequencies of the first oscillator and the second oscillator with each other via a coupling line, the phase difference corresponding to a direction in which beams formed by the first active antenna and the second active antenna are to be directed.

[0207] (Item 10)

[0208] The antenna device according to any one of items 1 to 9 is characterized in that a plurality of active antennas including a first active antenna and a second active antenna are arranged in a matrix.

[0209] (Item 11)

[0210] The antenna device according to item 10 is characterized in that

[0211] In the arrangement in the matrix, among the active antennas arranged in a first direction, the antennas included in the active antennas are coupled through coupling lines, and among the active antennas arranged in a second direction different from the first direction, the antennas included in the active antennas are not coupled through coupling lines, and

[0212] With respect to the active antennas arranged in the second direction, a terminal configured to commonly control an oscillation frequency of an oscillator included in each of the active antennas before synchronization through the coupling line is provided.

[0213] (Item 12)

[0214] The antenna device according to item 11 is characterized in that the first active antenna and the second active antenna are arranged in a first direction.

[0215] (Item 13)

[0216] The antenna device according to any one of items 1 to 12 is characterized in that the first antenna and the second antenna are arranged at an interval not greater than a wavelength of the electromagnetic wave.

[0217] (Item 14)

[0218] The antenna device according to any one of items 1 to 12 is characterized in that the first antenna and the second antenna are arranged at an interval equal to an integral multiple of the wavelength of the electromagnetic wave.

[0219] (Item 15)

[0220] The antenna device according to any one of items 1 to 14 is characterized in that each of the first antenna and the second antenna is a patch antenna.

[0221] (Item 16)

[0222] The antenna device according to any one of items 1 to 14 is characterized in that each of the first antenna and the second antenna is a slot antenna.

[0223] (Item 17)

[0224] The antenna device according to any one of items 1 to 16 is characterized in that the first antenna and the second antenna have the same shape.

[0225] (Item 18)

[0226] The antenna device according to any one of items 1 to 17 is characterized in that the coupling line capacitively couples the first antenna and the second antenna.

[0227] (Item 19)

[0228] The antenna device according to any one of items 1 to 17 is characterized in that the coupling line directly couples the first antenna and the second antenna.

[0229] (Item 20)

[0230] The antenna device according to any one of items 1 to 19, characterized in that

[0231] the first oscillator includes a third oscillator controlled to oscillate at an oscillation frequency common to the first oscillator and the second oscillator and a fourth oscillator controlled to oscillate at an independent oscillation frequency relative to the first oscillator, and the first oscillation frequency is an oscillation frequency obtained when the oscillation frequency of the third oscillator and the oscillation frequency of the fourth oscillator are synchronized with each other, and

[0232] The second oscillator includes a fifth oscillator controlled to oscillate at an oscillation frequency common to the first oscillator and the second oscillator and a sixth oscillator controlled to oscillate at an independent oscillation frequency relative to the second oscillator, and the first oscillation frequency is an oscillation frequency obtained when the oscillation frequency of the fifth oscillator and the oscillation frequency of the sixth oscillator are synchronized with each other.

[0233] (Item 21)

[0234] The antenna device according to any one of items 1 to 20 is characterized in that

[0235] The antenna device is formed on a first substrate, the first substrate includes a first active antenna, a second active antenna, and a plurality of wirings, through which signals for controlling the first oscillation frequency and the second oscillation frequency are transmitted,

[0236] the first substrate includes a plurality of through electrodes respectively connected to the plurality of wirings, and the plurality of through electrodes are formed to reach a bonding surface where the first substrate is bonded to another substrate, and

[0237] The plurality of through-electrodes function as first and second terminals.

[0238] (Item 22)

[0239] The antenna device according to item 21 is characterized by further comprising a second substrate, the second substrate comprising a plurality of electrodes, the plurality of electrodes being configured to output signals for controlling the first oscillation frequency and the second oscillation frequency respectively,

[0240] wherein the plurality of electrodes are formed on a bonding surface of the second substrate bonded to another substrate, and

[0241] The first substrate and the second substrate are bonded at a bonding surface, and the plurality of electrodes on the second substrate are electrically connected to the plurality of through electrodes.

[0242] (Item 23)

[0243] The antenna device according to any one of items 1 to 22 is characterized in that the electromagnetic wave is an electromagnetic wave in a terahertz band.

[0244] (Item 24)

[0245] A communication device, comprising:

[0246] An antenna device as defined in any of items 1 to 23;

[0247] a transmitting unit configured to transmit electromagnetic waves; and

[0248] The receiving unit is configured to detect electromagnetic waves.

[0249] (Item 25)

[0250] An imaging system, comprising:

[0251] An antenna device as defined in any of items 1 to 23;

[0252] a transmitting unit configured to transmit electromagnetic waves to the object; and

[0253] The detection unit is configured to detect the electromagnetic wave reflected by the object.

[0254] The present invention is not limited to the above embodiments, and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, in order to make the public aware of the scope of the present invention, the following claims are made.

[0255] This application claims the benefit of Japanese Patent Application No. 2022-067823 filed on April 15, 2022, which is hereby incorporated herein by reference.

Claims

1. An antenna device for generating or detecting electromagnetic waves, Features include: A first active antenna, comprising a first oscillator and a first antenna; A second active antenna, comprising a second oscillator and a second antenna; a coupling line configured to couple the first antenna and the second antenna; a first terminal configured to receive a signal for controlling a first oscillation frequency of the first oscillator before synchronization through the coupling line; as well as A second terminal is configured to receive a signal for controlling a second oscillation frequency of the second oscillator before synchronization through the coupling line independently of the first oscillation frequency.

2. The antenna device according to claim 1, It is characterized in that For the coupling line, the length of a path when the first oscillator and the second oscillator are connected via the coupling line is set based on the electrical length of the electromagnetic wave in the coupling line.

3. The antenna device according to claim 2, It is characterized in that For the coupled line, the length of the path is set to be equal to the electrical length of the electromagnetic wave which is an integer multiple of 2π.

4. The antenna device according to any one of claims 1 to 3, Features Each of the first oscillator and the second oscillator is a semiconductor structure including a negative resistance element.

5. The antenna device according to claim 4, Features The negative resistance element is a resonant tunneling diode.

6. The antenna device according to claim 4 or 5, Features The semiconductor structure of the first oscillator and the semiconductor structure of the second oscillator have the same shape.

7. The antenna device according to any one of claims 4 to 6, Features: The first oscillation frequency is determined based on a magnitude of a bias to be applied to the first oscillator, and the first terminal is a terminal configured to receive the bias to be applied to the first oscillator, and The second oscillation frequency is determined based on a magnitude of a bias to be applied to the second oscillator, and the second terminal is a terminal configured to receive the bias to be applied to the second oscillator.

8. The antenna device according to claim 7, Features A bias having a magnitude in a negative resistance region of the negative resistance element is applied to each of the first oscillator and the second oscillator.

9. The antenna device according to any one of claims 1 to 8, Features The first oscillation frequency and the second oscillation frequency are set based on a phase difference between electromagnetic waves to be obtained by the first active antenna and the second active antenna after synchronizing the oscillation frequencies of the first oscillator and the second oscillator with each other via the coupling line, the phase difference corresponding to a direction in which a beam formed by the first active antenna and the second active antenna is to be directed.

10. The antenna device according to any one of claims 1 to 9, Features A plurality of active antennas including the first active antenna and the second active antenna are arranged in a matrix.

11. The antenna device according to claim 10, Features: In the arrangement in the matrix, among the active antennas arranged in a first direction, the antennas included in the active antennas are coupled through the coupling line, and among the active antennas arranged in a second direction different from the first direction, the antennas included in the active antennas are not coupled through the coupling line, and With respect to the active antennas arranged in the second direction, a terminal configured to commonly control an oscillation frequency of an oscillator included in each of the active antennas before synchronization through the coupling line is provided.

12. The antenna device according to claim 11, Features The first active antenna and the second active antenna are arranged in the first direction.

13. The antenna device according to any one of claims 1 to 12, Features The first antenna and the second antenna are arranged at an interval not greater than a wavelength of an electromagnetic wave.

14. The antenna device according to any one of claims 1 to 12, Features The first antenna and the second antenna are arranged at an interval equal to an integral multiple of a wavelength of an electromagnetic wave.

15. The antenna device according to any one of claims 1 to 14, Features Each of the first antenna and the second antenna is a patch antenna.

16. The antenna device according to any one of claims 1 to 14, Features Each of the first antenna and the second antenna is a slot antenna.

17. The antenna device according to any one of claims 1 to 16, Features The first antenna and the second antenna have the same shape.

18. The antenna device according to any one of claims 1 to 17, Features The coupling line capacitively couples the first antenna and the second antenna.

19. The antenna device according to any one of claims 1 to 17, Features The coupling line directly couples the first antenna and the second antenna.

20. The antenna device according to any one of claims 1 to 19, Features the first oscillator includes a third oscillator controlled to oscillate at an oscillation frequency common to the first oscillator and the second oscillator and a fourth oscillator controlled to oscillate at an oscillation frequency independent of the first oscillator, and the first oscillation frequency is an oscillation frequency obtained when the oscillation frequency of the third oscillator and the oscillation frequency of the fourth oscillator are synchronized with each other, and The second oscillator includes a fifth oscillator controlled to oscillate at an oscillation frequency common to the first oscillator and the second oscillator and a sixth oscillator controlled to oscillate at an independent oscillation frequency relative to the second oscillator, and the first oscillation frequency is an oscillation frequency obtained when the oscillation frequency of the fifth oscillator and the oscillation frequency of the sixth oscillator are synchronized with each other.

21. The antenna device according to any one of claims 1 to 20, Features: The antenna device is formed on a first substrate, the first substrate includes the first active antenna, the second active antenna, and a plurality of wirings, and signals for controlling the first oscillation frequency and the second oscillation frequency are transmitted through the plurality of wirings, the first substrate includes a plurality of through electrodes respectively connected to the plurality of wirings, and the plurality of through electrodes are formed to reach a bonding surface where the first substrate is bonded to another substrate, and The plurality of through-electrodes function as the first terminal and the second terminal.

22. The antenna device according to claim 21, Features Also included is a second substrate, the second substrate includes a plurality of electrodes, the plurality of electrodes are configured to output signals for controlling the first oscillation frequency and the second oscillation frequency respectively, wherein the plurality of electrodes are formed on a bonding surface of the second substrate to another substrate, and The first substrate and the second substrate are bonded at the bonding surface, and the plurality of electrodes on the second substrate are electrically connected to the plurality of through electrodes.

23. The antenna device according to any one of claims 1 to 22, Features The electromagnetic waves are electromagnetic waves in the terahertz band.

24. A communication device, Features include: The antenna device as defined in any one of claims 1 to 23; A transmitting unit configured to transmit electromagnetic waves; as well as The receiving unit is configured to detect the electromagnetic wave.

25. An imaging system, Features include: The antenna device as defined in any one of claims 1 to 23; A transmitting unit configured to transmit electromagnetic waves to an object; as well as The detection unit is configured to detect the electromagnetic wave reflected by the object.

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