Antenna device, communication device, and imaging system

Abstract

To allow for applying beamforming in an antenna device including a plurality of active antennas.SOLUTION: An antenna device for generating or detecting electromagnetic waves includes: a first active antenna which includes a first oscillator and a first antenna; a second active antenna which includes a second oscillator and a second antenna; a coupling line which couples the first antenna and the second antenna; a first terminal which receives a signal for controlling a first oscillation frequency which is of the first oscillator and before being synchronized by the coupling line; and a second terminal which receives a signal for controlling the second oscillation frequency which is of the second oscillator and before being synchronized by the coupling line, independently of the first oscillation frequency.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antenna device that outputs or detects electromagnetic waves. [Background technology]

[0002] As a current injection type light source that generates electromagnetic waves such as terahertz waves, an oscillator that integrates an element having electromagnetic wave gain for terahertz waves and a resonator is known. Among these, an oscillator that integrates a resonant tunneling diode (RTD) and an antenna is expected to be an element that operates at room temperature in a frequency range around 1 THz. Patent Document 1 discloses a terahertz wave antenna array in which multiple active antennas, each integrating an RTD oscillator and an antenna, are arranged on the same substrate. In the antenna array of Patent Document 1, multiple active antennas are mutually coupled using coupling wires, and the multiple active antennas are synchronized and oscillated in phase with each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-200065 [Non-patent literature]

[0004] [Non-Patent Document 1] Jpn.J.Appl.Phys.,Vol.47,No.6(2008), pp.4375-4384 [Non-patent document 2] J.Appl.Phys.,Vol.103,124514(2008) Summary of the Invention [Problem to be solved by the invention]

[0005] The antenna array described in Patent Document 1 can synchronize the phase between multiple active antennas, but has not made much progress in applying beamforming, which controls the phase difference between the active antennas to direct a beam in any direction.

[0006] The present invention provides a technique that enables beamforming to be applied to an antenna device including multiple active antennas. [Means for solving the problem]

[0007] An antenna device according to one embodiment of the present invention is an antenna device that generates or detects electromagnetic waves, and includes: 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 that couples the first antenna to the second antenna; a first terminal that receives a signal for controlling a first oscillation frequency of the first oscillator before it is synchronized by the coupling line; and a second terminal that receives a signal for controlling a second oscillation frequency of the second oscillator before it is synchronized by the coupling line, independently of the first oscillation frequency. [Effects of the Invention]

[0008] According to the present invention, beamforming can be applied to an antenna device including a plurality of active antennas. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a block diagram illustrating a schematic configuration of an antenna device. [Figure 2] FIG. 1 is a circuit diagram of an antenna array. [Figure 3] FIG. 2 is a schematic top view illustrating an example of the configuration of an antenna device. [Figure 4] FIG. 2 is a cross-sectional view of an element included in the antenna device. [Figure 5]FIG. 1A is a schematic diagram showing the effect of the antenna device, and FIG. 1B is a schematic diagram explaining beamforming. [Figure 6] FIG. 1 is a block diagram illustrating a schematic configuration of an antenna device. [Figure 7] FIG. 2 is a schematic top view illustrating an example of the configuration of an antenna device. [Figure 8] FIG. 2 is a schematic top view showing elements included in the antenna device. [Figure 9] FIG. 2 is a schematic top view showing elements included in the antenna device. [Figure 10] FIG. 2 is a cross-sectional view of an element included in the antenna device. [Figure 11] FIG. 1 is a block diagram illustrating a schematic configuration of an antenna device. [Figure 12] FIG. 2 is a schematic top view illustrating an example of the configuration of an antenna device. [Figure 13] FIG. 2 is a cross-sectional view of an element included in the antenna device. [Figure 14] 1A is a diagram illustrating an example of the configuration of a camera system using an antenna device, and FIG. 1B is a diagram illustrating an example of the configuration of a communication system using an antenna device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] [Embodiment 1] The configuration of an antenna device 10 according to this embodiment that is applicable to terahertz waves will be described with reference to Figures 1 to 4. Note that, although the following description will be given particularly of the case where the antenna device 10 is used as a transmitter, the antenna device 10 can also be used as a receiver. Here, terahertz waves refer to electromagnetic waves within a frequency range of 10 GHz or higher and 100 THz or lower, and in one example, refer to electromagnetic waves within a frequency range of 30 GHz or higher and 30 THz or lower.

[0012] 1 shows a block diagram illustrating an example of the system configuration of an antenna device 10. The antenna device 10 includes an element 12 that forms an antenna, a bias control unit 13, and a beam direction control unit .

[0013] The element 12 is an antenna element including an antenna array 11 configured with multiple active antennas 11a-11i arranged in an array. Each active antenna 11a integrates at least one antenna 100a and a semiconductor 101a serving as an oscillation source, and is configured to emit terahertz waves TW with an oscillation frequency f0. The same applies to the other active antennas, each including an antenna and a semiconductor and configured to emit terahertz waves TW with an oscillation frequency f0. Of the active antennas 11a-11i, the components other than the semiconductors 101a-101i serving as oscillation components may be considered to be antennas. For example, only the antenna conductor or a combination of the antenna conductor and a ground (GND) conductor may be considered to be antennas. The semiconductors 101a-101i and the antennas 100a-100i are configured to have the same shape as the active antennas 11a-11i. Here, "same shape" refers to having the same shape at the time of design and also includes having approximately the same shape in an implemented product. Therefore, the semiconductors 101a to 101i and the antennas 100a to 100i are assumed to have the same characteristics. Therefore, when there is no need to distinguish between them, they will be referred to as the semiconductor 101 and the antenna 100. The semiconductors 101a to 101i of the active antennas 11a to 11i include a semiconductor structure for generating or detecting terahertz waves. In this embodiment, an example will be described in which a resonant tunneling diode (RTD) is used as this semiconductor structure. The semiconductor structure here is not limited to an RTD, and any semiconductor having electromagnetic wave gain or carrier nonlinearity (nonlinearity of current associated with voltage change in current-voltage characteristics) for terahertz waves will suffice. Also, any type of oscillator other than a semiconductor structure may be used. In the following description, such a semiconductor for generating or detecting terahertz waves may also be referred to as an RTD. The active antennas 11a to 11i are electrically connected to each other by coupling lines 102ab to 102hi, which are transmission lines that couple the antennas to generate a mutual injection locking phenomenon. For example, the active antennas 11a and 11b are connected by a coupling wire 102ab.

[0014] The bias control unit 13 is a power supply for controlling a bias signal 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 provides 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 the semiconductors 101a to 101i in each of the active antennas 11a to 11i by providing a control signal to the bias control unit 13 via the control line 106. Hereinafter, the term "bias" may refer to at least one of the bias voltage and bias current. The semiconductors 101a to 101i have a characteristic such that the oscillation frequency changes depending on the bias applied thereto.

[0015] The active antennas 11a to 11i oscillate at different terahertz frequencies f1 to f9 depending on the applied bias voltage. The coupled wires 102ab to 102hi connected between the active antennas 11a to 11i cause the active antennas 11a to 11i to oscillate at a single frequency f0 due to the mutual injection locking phenomenon. Here, the active antennas 11a to 11i oscillate with a phase calculated from the frequency difference between the frequency f0 and the oscillation frequencies f1 to f9 in the absence of mutual injection locking. In other words, the active antennas 11a to 11i oscillate at the same frequency f0 and with a phase difference corresponding to the original oscillation frequencies f1 to f9.

[0016] In this embodiment, focusing on this characteristic, the phase difference between the active antennas 11a to 11i is adjusted by adjusting the bias applied to each of the active antennas 11a to 11i. By adjusting this phase difference, it is possible to perform beamforming so that the beam points in a predetermined direction from the direction perpendicular to the substrate (so that the peak of the beam gain points in the predetermined direction). In this embodiment, the beam direction control unit 14 determines the phase difference between each of the active antennas 11a to 11i and provides a control signal to the bias control unit 13 so that a bias corresponding to the phase difference is applied to each of the active antennas 11a to 11i. The bias control unit 13 then applies a bias corresponding to the control signal to each of the active antennas 11a to 11i, thereby performing beamforming so that the beam points in the predetermined direction. As a result, the antenna array 11 can emit terahertz waves TW with an oscillation frequency f0 so that the peak of the antenna gain points in an arbitrary angle from the direction perpendicular to the substrate.

[0017] FIG. 2 is a circuit diagram illustrating the electrical connection between the active antennas 11a and 11b. While the description focuses on the relationship between the active antennas 11a and 11b, the relationship between the other active antennas is similar. The active antenna 11a is connected in parallel to the negative resistance -r of the semiconductor 101a and the impedance Z of the antenna 100a. The impedance Z includes a resistance component and an LC component due to the structure of the antenna 100a. The bias applied by the bias control unit 13 for applying a bias current to the semiconductor 101a is shown as the power supply 13a. The active antenna 11b has a similar configuration. The bias control unit 13 supplies, for example, currents required to drive the semiconductors 101a and 101b and independently adjusts the biases applied to the semiconductors 101a and 101b. In other words, the antenna device 10 is configured such that the first bias applied to the semiconductor 101a and the bias applied to the semiconductor 101b are set independently. The bias is controlled by the beam direction control unit 14 providing a control signal to the bias control unit 13 via control lines 106a and 106b. While FIG. 2 illustrates an example configuration in which the beam direction control unit 14 transmits a control signal to the bias control unit 13 via a different signal line for each active antenna, the present invention is not limited to this. In other words, as long as information capable of identifying the bias to be applied to the semiconductor 101 of each active antenna is notified to the bias control unit 13, the information may be notified to the bias control unit 13 as a single piece of information. Meanwhile, the bias control unit 13 is configured to independently control the bias for each active antenna. Furthermore, the element 12 has a terminal (input line) for receiving a signal for independently controlling the magnitude of the bias for each active antenna. When an RTD is used as the semiconductor 101, the bias voltage is selected from a voltage that falls within the negative differential resistance region of the RTD.

[0018] Adjacent active antennas 11a and 11b are electrically connected by a coupling wire 102ab, thereby mutually coupling the antennas. The coupling wire 102ab is connected to the active antennas 11a and 11b via capacitances C1 and C2. The capacitances C1 and C2 function as high-pass filters and are set to have capacitances that are short-circuited for electromagnetic waves in the terahertz band and open for electromagnetic waves in the low-frequency band. The other active antennas 11b to 11i have a similar configuration. The capacitances C1 and C2 may not be provided. (Implementation example) The structure and configuration of the antenna device 10 of the first embodiment will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a schematic top view of an element 12 in which nine active antennas 11a to 11i are arranged in a 3×3 matrix, and FIG. 4 is a cross-sectional view of the element 12 taken along lines A-A' and B-B' in FIG. 3. The element 12 may be referred to as a chip, for example. The element 12 is an element that emits or detects terahertz waves having a frequency f0 and is made of a semiconductor material. In this embodiment, the element 12 will be described as an antenna array in which nine active antennas 11a to 11i are arranged in a 3×3 matrix, as an example. Note that the example in FIG. 3 illustrates an example in which a square patch antenna is used as the antenna 100 included in each active antenna. However, this is not limited to this. For example, the number of active antennas is not limited to nine, and even when arranged in a matrix, they may be arranged in a form other than 3×3. That is, for any positive integers m and n, the active antennas 11a to 11i can be arranged in an m×n array (m or n is 2 or greater) to form the antenna array 11. Increasing the number of active antennas (i.e., m or n) can narrow the beam width and improve the beam gain in the direction of the beam. When m or n is 1, the antenna array 11 is arranged in a single row, enabling beamforming in the direction of the row. The antenna 100 may be, for example, a slot antenna or may not be a patch antenna. The active antennas 11a to 11i function as both a resonator that resonates with terahertz waves and a radiator that transmits or receives terahertz waves. In the element 12, the active antennas (antennas 100) can be arranged at a pitch (spacing) equal to or less than the wavelength of the terahertz waves to be detected or generated, or at an integer multiple of that wavelength. The discussion of this embodiment is applicable not only to antennas that radiate horizontally or vertically polarized waves, but also to antennas that radiate circularly polarized waves.

[0019] As described above, each active antenna includes a semiconductor 101 as an oscillator, and adjacent antennas are coupled by coupled wires 102 to synchronize these oscillators. The active antennas and each coupled wire 102 are connected by capacitive coupling. The length of the coupled wire 102 is designed so that when adjacent antennas are connected by the coupled wire, phase matching conditions are satisfied in either the X direction or the Y direction, or both. The coupled wire 102 can be designed to have a length such that the electrical length of the coupled wire 102 between the semiconductors 101 of adjacent active antennas is an integer multiple of 2π. In other words, the length of the coupled wire 102 can be set so that when RTDs are connected by the coupled wire 102, the length of the path passing through the coupled wire 102 is an integer multiple of the wavelength of the propagating electromagnetic wave.

[0020] In the following, the configuration of each active antenna constituting element 12 will first be described, followed by the configurations of bias control unit 13 and beam direction control unit 14. After that, examples of specific materials and structural dimensions will be described, followed by a method for manufacturing element 12. Note that active antennas 11a to 11i each have a similar configuration. Therefore, in the following, when it is not necessary to distinguish between active antennas 11a to 11i, they will be collectively referred to simply as "active antennas." In other words, the configuration of the "active antenna" described below applies to each of active antennas 11a to 11i. Similarly, in the figures, the symbol "a" is attached to the component corresponding to active antenna 11a, but when it is not particularly necessary to distinguish between active antennas, the symbol will be omitted in the following description.

[0021] (About active antennas) As shown in FIG. 4, the active antenna includes a substrate 122, a conductor layer 121, a conductor constituting the antenna 100 (hereinafter, sometimes referred to as "conductor 100"), and dielectric layers 119-120. As shown in FIG. 4, the substrate 122, the conductor layer 121, and the conductor 100 are laminated in this order, and the dielectric layers 119-120 are located between the two conductor layers (wiring layers) of the conductor layer 121 and the conductor 100. The dielectric layers 119-120 are arranged in this order from the conductor layer 121 side: the dielectric layer 120 and the dielectric layer 119. The antenna configuration shown in FIG. 4 is called a microstrip antenna using a microstrip line or the like with a finite length. Here, an example using a patch antenna, which is a microstrip resonator, will be described. The conductor 100 is a patch conductor (upper conductor of the patch antenna) of the active antenna, which is arranged so as to face the conductor layer 121 via the dielectric layers 119-120. The conductor layer 121 is a ground conductor (ground conductor, GND conductor) that is electrically grounded, and also serves as a reflector layer. The active antenna has a width λ in the Y direction (resonance direction) of the conductor 100 in FIG. THz It is set to operate as a λ / 2 resonator. THz is the effective wavelength in the dielectric layers 119 to 120 of the terahertz wave that resonates in the active antenna. The wavelength of the terahertz wave in a vacuum is λ0, and the effective relative dielectric constant of the dielectric layer 119 is ε r Then, λ THz =λ0×ε r -1 / 2 It is expressed as:

[0022] The active antenna includes a semiconductor 101 (semiconductor layer, semiconductor structure). This semiconductor layer corresponds to 101a to 101i in FIG. 1 and, as described above, is a resonant tunneling diode (RTD) in this embodiment. An RTD is a typical semiconductor structure having electromagnetic wave gain in the terahertz wave frequency band and is also called an active layer. For this reason, hereinafter, the semiconductor 101 may be referred to as an "RTD." The RTD has a resonant tunneling structure layer including multiple tunnel barrier layers, and a quantum well layer is provided between the multiple tunnel barriers, providing a multiple quantum well structure that generates terahertz waves through intersubband transitions of carriers. The RTD has electromagnetic wave gain in the terahertz wave frequency range based on the photon-assisted tunneling phenomenon in the negative differential resistance region of the current-voltage characteristics and exhibits self-oscillation in the negative differential resistance region.

[0023] The semiconductor 101 is electrically connected to the conductor 100. The semiconductor structure is, for example, a mesa-type structure, and the semiconductor 101 includes an electrode (Ohmic or Schottky) that contacts the semiconductor structure and an electrode layer for connecting to upper and lower wiring layers. The semiconductor 101 is located inside the active antenna and is configured to oscillate or detect terahertz electromagnetic waves. The semiconductor 101 is composed of a semiconductor layer that has gain or nonlinearity of electromagnetic waves for terahertz waves.

[0024] The active antenna is an active antenna in which a semiconductor 101 and a patch antenna (conductor 100) are integrated. The frequency f of the terahertz wave oscillated from the active antenna alone is THz is determined by the resonant frequency of the total parallel resonant circuit that combines the patch antenna and the reactance of the semiconductor 101. Specifically, from the equivalent circuit of the oscillator described in Non-Patent Document 1, for a resonant circuit that combines the admittances of the RTD and the antenna (YRTD and Yaa), the frequency that satisfies the amplitude condition of equation (1) and the phase condition of equation (2) is the oscillation frequency f THz is determined as follows. Re[YRTD]+Re[Y11]≦0 (1) Im[YRTD]+Im[Y11]=0 (2) Here, YRTD is the admittance of the semiconductor 101, Re is the real part, and Im is the imaginary part. Because the semiconductor 101 includes an RTD, which is a negative resistance element, Re[YRTD] has a negative value. Furthermore, Y11 represents the admittance of the entire structure of the active antenna as seen from the semiconductor 101.

[0025] The semiconductor 101 may be a quantum cascade laser (QCL) structure having a multilayer structure of several hundred to several thousand semiconductor layers. In this case, the semiconductor 101 is a semiconductor layer including a QCL structure. The semiconductor 101 may be a negative resistance element, such as a Gunn diode or an IMPATT diode, which are commonly used in the millimeter-wave band. The semiconductor 101 may be a high-frequency element, such as a transistor terminated at one terminal. Examples of the transistor include a heterojunction bipolar transistor (HBT), a compound semiconductor layer-based FET, and a high electron mobility transistor (HEMT). The semiconductor 101 may be a Josephson junction with a superconductor layer and exhibiting negative differential resistance. That is, the semiconductor 101 does not have to be an RTD, and any other structure having similar characteristics may be used as long as it is a semiconductor structure for generating or detecting electromagnetic waves in a predetermined frequency band. Although an RTD is used here as a configuration suitable for terahertz waves, an antenna array compatible with electromagnetic waves in any frequency band may be realized using the configuration described in this embodiment. That is, the semiconductor 101 in this embodiment is not limited to an RTD that outputs terahertz waves, but can be formed using a semiconductor that can output electromagnetic waves in any frequency band.

[0026] In microstrip resonators such as patch antennas, a thick dielectric layer reduces conductor loss and improves radiation efficiency. The dielectric layers 119-120 must be able to be formed into thick films (typically 3 μm or more), have low loss and a low dielectric constant in the terahertz band, and be easily microfabricated (e.g., planarized or etched). While a thicker dielectric layer increases radiation efficiency, a too-thick layer can result in multimode resonance. Therefore, the upper limit of the dielectric layer thickness can be designed to be no more than 1 / 10 of the oscillation wavelength. Meanwhile, increasing the frequency and output of oscillators requires miniaturization of diodes and high current densities. Therefore, the dielectric layer must also function as an insulating structure for the diode, suppressing leakage current and preventing migration. To satisfy these two requirements, the dielectric layers 119-120 may be made of different materials.

[0027] The dielectric layer 119 is made of BCB (benzocyclobutene, manufactured by Dow Chemical Company, ε r1 Organic dielectric materials such as ε = 2), polytetrafluoroethylene, and polyimide can be used. r1 is the relative dielectric constant of the dielectric layer 119. Alternatively, inorganic dielectric materials such as TEOS oxide film or spin-on glass, which can be formed into a relatively thick film and have a low dielectric constant, may be used for the dielectric layer 119. Furthermore, the dielectric layer 120 is required to have insulating properties (the property of acting as an insulator that does not conduct electricity against DC voltage or as a high-resistance material), barrier properties (the property of preventing the diffusion of metal materials used for the electrodes), and processability (the property of being able to be processed with submicron precision). Examples of materials that satisfy these requirements include silicon oxide (ε r2 =4), silicon nitride (ε r2 =7), inorganic insulating materials such as aluminum oxide and aluminum nitride are used. r2 is the relative dielectric constant of the dielectric layer 120. The dielectric layer 118 may have the same characteristics as the dielectric layer 120.

[0028] Here, when the dielectric layers 119 to 120 have a multi-layer structure as in this embodiment, the relative dielectric constant ε ris the thickness of the dielectric layer 119 and the relative dielectric constant ε r1 and the thickness and relative permittivity ε of the dielectric layer 120 r2 From the viewpoint of impedance matching between the antenna and space, in order to reduce the difference in permittivity between the antenna and air, the dielectric layer 119 is made of a material different from that of the dielectric layer 120 and has a low permittivity (ε r1 <ε r2 In the antenna device 10, the dielectric layer does not need to have a multi-layer structure, and may have a structure made of only one layer of the above-mentioned materials.

[0029] The semiconductor 101 is disposed on a conductor layer 121 formed on a substrate 122. The semiconductor 101 and the conductor layer 121 are electrically connected. Note that, in order to reduce ohmic loss, the semiconductor 101 and the conductor layer 121 can be connected with low resistance. A via 114 is disposed on the side of the semiconductor 101 opposite to the side on which the conductor layer 121 is disposed, and the via 114 and the semiconductor 101 are electrically connected. The semiconductor 101 is embedded in a dielectric layer 120, and is surrounded by the dielectric layer 120. Note that a "via" is a through electrode that penetrates between layers.

[0030] The semiconductor 101 includes an ohmic electrode, which is a conductor that forms an ohmic connection with the semiconductor to reduce ohmic loss and RC delay due to series resistance. Examples of materials that can be used for the ohmic electrode include Ti / Au, Ti / Pd / Au, Ti / Pt / Au, AuGe / Ni / Au, TiW, Mo, and ErAs. Note that these materials are designated by element symbols, and the substances represented by each symbol will not be described in detail here. This also applies to the following description. Furthermore, by using a semiconductor with a high concentration of impurities doped in the contact area between the semiconductor and the ohmic electrode, the contact resistance can be reduced, thereby achieving higher output and higher frequencies. When an RTD is used as the semiconductor 101, the absolute value of the negative resistance, which indicates the magnitude of the gain of an RTD used in the terahertz wave band, is generally on the order of 1 to 100 Ω, and the loss of electromagnetic waves can be suppressed to 1% or less of that. Therefore, the contact resistance of the ohmic electrode can be suppressed to 1 Ω or less as a guideline. In order to operate in the terahertz wave band, the semiconductor 101 is formed so that its width is typically about 0.1 to 5 μm. Therefore, the contact resistance is set to a resistivity of 10 Ω·μm 2 The resistance is controlled to a range of 0.001 to several Ω or less.

[0031] Furthermore, the semiconductor 101 may be configured to include a metal (Schottky electrode) that forms a Schottky contact rather than an ohmic contact. In this case, the contact interface between the Schottky electrode and the semiconductor exhibits rectification, and the active antenna AA can be used as a terahertz wave detector. Note that the following describes a configuration using an ohmic electrode.

[0032] As shown in FIG. 4A, the interior of the active antenna is stacked in the following order: substrate 122, conductor layer 121, semiconductor 101, via 114, conductor 100, and bond wire 102 (conductor). Via 114 is a conductor formed inside dielectric layer 119, and conductor 100 and semiconductor 101 are electrically connected through via 114. If the width of via 114 is too large, the resonance characteristics of the patch antenna deteriorate and radiation efficiency decreases due to increased parasitic capacitance. Therefore, the width of via 114 can be configured to a dimension that does not interfere with the resonant electric field, typically, 1 / 10 or less of the effective wavelength λ of the terahertz wave at the standing oscillation frequency f0 of the active antenna. The width of via 114 may be small enough not to increase the series resistance; as a guideline, it can be reduced to approximately twice the skin depth. To minimize the series resistance to 1 Ω or less, the width of via 114 is typically in the range of 0.1 μm to 20 μm.

[0033] In FIG. 4(b), the conductor 100 is electrically connected to the wiring 111 through the via 110, and the wiring 111 is electrically connected to the bias control unit 13 through the bias line 105, which is a wiring formed within the chip. The bias line 105 is disposed between the conductor 100 and the conductor layer 121, more specifically, between the dielectric layer 119 and the dielectric layer 120. The bias line 105 is disposed at a position that does not overlap with the conductor 100 in a planar view so as not to be affected by or affect the radiation of the antenna. Two wirings 111 are drawn out from each antenna. For example, in FIGS. 3 and 4(b), vias 110a1 and 110a2 are drawn out from the conductor 100a of the active antenna 11a and connected to the wirings 111a1 and 111a2, respectively. The wirings 111a1 and 111a2 are then both electrically connected to the bias control unit 13 through the bias line 105a. The bias control unit 13 is a power supply for supplying a bias signal to the semiconductor 101 of the active antenna. Therefore, a bias is supplied to the semiconductor 101 of each antenna by connecting the bias line 105 to wiring 111 drawn from each antenna. In this embodiment, a bias line 105 is provided for each active antenna, so that the bias applied to the semiconductor 101 of each active antenna can be set individually. The bias control unit 13 independently controls the bias for the semiconductor 101 of each active antenna, for example, via terminals for separately controlling the bias for each of the multiple active antennas provided in the element 12.

[0034] The via 110 is a connection portion for electrically and mechanically connecting the wiring 111 to the conductor 100. A structure that electrically connects upper and lower layers is called a via. The conductor layer 121 and the conductor 100 not only function as components of the patch antenna, but also serve as electrodes for injecting current into the RTD, which is the semiconductor 101, when connected to these vias. In this embodiment, materials with a resistivity of 1×10 Ω·m or less can be used for the via 110 and the wiring 111. Specifically, metals and metal compounds such as Ag, Au, Cu, W, Ni, Cr, Ti, Al, AuIn alloy, and TiN can be used as the material.

[0035] The width of the via 110 is smaller than the width of the conductor 100. The width of the conductor 100 here refers to the width in the electromagnetic wave resonance direction within the active antenna (i.e., the Y direction in FIG. 3). The width of the portion (connection portion) of the wiring 111 connected to the via 110 is smaller (thinner) than the width of the conductor 100 (active antenna). These widths can be set to 1 / 10 or less of the effective wavelength λ (λ / 10 or less) of the terahertz wave of the oscillation frequency f0 standing in the active antenna. This is because the radiation efficiency can be improved by arranging the via 110 and the wiring 111 at dimensions and positions that do not interfere with the resonant electric field within the active antenna.

[0036] Furthermore, the via 110 can be positioned at a node of the electric field of the terahertz wave of oscillation frequency f0 standing in the active antenna. In this case, the via 110 and the wiring 111 are configured to have impedances sufficiently higher than the absolute value of the negative differential resistance of the RTD (semiconductor 101) in a frequency band near the oscillation frequency f0. In other words, the via 110 and the wiring 111 are connected to another active antenna so as to present a high impedance to the RTD at the oscillation frequency f0. In this case, the other active antenna is isolated (separated) at the frequency f0 through the path via the bias line 105. This prevents the current of oscillation frequency f0 induced in each active antenna via the bias line 105 and the bias control unit 13 from affecting adjacent antennas. Furthermore, interference between the electric field of oscillation frequency f0 standing in the active antenna and these power supply members is suppressed.

[0037] The bias control unit 13 is disposed 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 low-frequency parasitic oscillation. The stabilization circuit is configured to have an impedance lower than the absolute value of the negative resistance corresponding to the gain of the semiconductor 101 in the frequency band from DC to 10 GHz. For stabilization at relatively high frequencies from 0.1 to 10 GHz, an AC short circuit in which a TiW resistive layer and an MIM (Metal-Insulator-Metal) capacitor are connected in series may be disposed in each of the bias lines 105a to 105i. In this case, the MIM capacitor has a large capacitance within the above-mentioned frequency range, for example, a capacitance of approximately several pF.

[0038] (About the antenna array) In FIG. 3, antenna array 11 is configured with nine active antennas 11a to 11i arranged in a 3×3 matrix. Each active antenna individually oscillates terahertz waves at frequencies f1 to f9. The number of active antennas is not limited to nine; for example, 16 active antennas may be arranged in a 4×4 matrix, or 15 active antennas may be arranged in a 3×5 matrix. Adjacent antennas are coupled to each other by coupling wire 102, and are synchronized with each other by mutual injection locking, outputting terahertz waves with an oscillation frequency of f0. Mutual injection locking is a phenomenon in which multiple self-excited oscillators oscillate in synchronization with each other through mutual interaction. For example, active antenna 11a and active antenna 11d are coupled to each other by coupling wire 102ad and are further coupled to each other via conductor layer 121. The same applies to other adjacent active antennas. Note that "mutually coupled" refers to a relationship in which a current induced in one active antenna acts on another adjacent active antenna due to the coupling, thereby changing their respective transmission and reception characteristics. When mutually coupled active antennas synchronize in phase or opposite phase, mutual injection locking occurs, causing mutual strengthening or weakening of the electromagnetic fields between the active antennas. This makes it possible to adjust the increase or decrease of antenna gain. Note that in this embodiment, the entire coupling line coupling the active antennas is referred to as coupling line 102. Furthermore, the coupling lines coupling each antenna that constitutes coupling line 102 are referred to using the alphabet corresponding to each active antenna. For example, the coupling line coupling active antenna 11a and active antenna 11d is referred to as coupling line 102ad.

[0039] The oscillation conditions of the antenna array 11 are determined by the conditions of mutual injection locking in a configuration in which two or more individual RTD oscillators are coupled, as described in Non-Patent Document 2. Specifically, consider the oscillation conditions of an antenna array in which active antenna 11a and active antenna 11b are coupled by coupling line 102ab. In this case, two oscillation modes occur: positive-phase mutual injection locking and anti-phase mutual injection locking. The oscillation conditions for the positive-phase mutual injection locking oscillation mode (even mode) are expressed by equations (4) and (5), and the oscillation conditions for the anti-phase mutual injection locking oscillation mode (odd mode) are expressed by equations (6) and (7). Positive phase (even mode): Frequency f=feven Yeven=Y11+Y12+YRTD Re(Yeven)≦0 (4) Im(Yeven)=0 (5) Out of phase (odd mode): frequency f=fodd Yodd=Y11+Y12-YRTD Re(Yodd)≦0 (6) Im(Yodd)=0 (7) Here, Y12 is the mutual admittance between the active antenna 11a and the active antenna 11b. Y12 is proportional to the coupling constant that represents the strength of coupling between the antennas, and ideally, the real part of -Y12 is large and the imaginary part is zero. The antenna array 11 of this embodiment is coupled under the condition of mutual injection locking in positive phase, and the oscillation frequency f0 is approximately equal to five-even. Similarly, the other antennas are coupled to each other via coupling lines 102 so as to satisfy the above-mentioned condition of mutual injection locking in positive phase.

[0040] Bonded wire 102 is a microstrip line in which dielectric layers 118-120 are sandwiched between the conductor of bonded wire 102 and conductor layer 121 or bias line 105. For example, as shown in FIG. 4( a), bonded wire 102ab has a structure in which dielectric layers 118-120 are sandwiched between the conductor of bonded wire 102ab and conductor layer 121 or bias line 105. Similarly, bonded wire 102bc has a structure in which dielectric layers 118-120 are sandwiched between the conductor of bonded wire 102bc and conductor layer 121 or bias line 105.

[0041] The antenna array 11 is an antenna array configured such that the antennas are coupled to each other by AC coupling (alternating current coupling, capacitive coupling). For example, the upper conductor layer (102bc in FIG. 4(a)) of the coupled wire 102bc overlaps the conductor 100, which is the patch conductor of each of the active antennas 11b and 11c, with the dielectric layer 118 sandwiched between them in a planar view, forming a capacitive coupling connection. More specifically, the conductor of the coupled wire 102bc overlaps the conductor 100 by 5 μm in a planar view near the radiation ends of the active antennas 11b and 11c, with the dielectric layer 118 sandwiched between them, forming capacitive structures C1 and C2. The capacitive structures C1 and C2 correspond to the capacitors C1 and C2 in the circuit diagram of FIG. 3. The capacitors C1 and C2 in this configuration function as high-pass filters, shorting terahertz-band electromagnetic waves and opening low-frequency-band electromagnetic waves, thereby contributing to suppressing multimode oscillation. However, this configuration is not an essential requirement, and a DC-coupling configuration may be used in which the conductor of the coupling wire 102bc is directly coupled (connected) to the conductors 100 of the active antennas 11b and 11c. An antenna array synchronized by DC coupling can synchronize adjacent antennas with strong coupling, making it easier to achieve synchronization by pull-in. Note that although the coupling between the active antennas 11b and 11c has been described as an example here, the same applies to the coupling between the other active antennas 11a to 11i.

[0042] In the antenna array 11, the active antenna conductor 100, the conductor of the coupled wire 102, and the bias line 105 are arranged on different layers. In this way, the active antenna conductor 100 and coupled wire 102 that transmit high-frequency (terahertz-band) electromagnetic waves and the bias wiring layer that transmits low-frequency (DC to several tens of GHz) electromagnetic waves can be arranged on different layers. This allows for flexible design of the layout, such as the width, length, and routing of the transmission lines within each layer. Furthermore, as shown in FIG. 4(a), the coupled wire 102 and the bias line 105 cross each other when viewed from above (in a plan view), thereby achieving a more compact layout. This allows for an increased number of antennas to be arranged even in an antenna array in which antennas are arranged in an m×n (m≧2, n≧2) matrix.

[0043] In the terahertz band, resistance due to the skin effect increases, making conductor loss associated with high-frequency transmission between antennas non-negligible. As the current density between conductor layers increases, conductor loss per unit length (dB / mm) increases. In the case of a microstrip line, conductor loss per unit length (dB / mm) is inversely proportional to the square of the dielectric thickness. Therefore, to improve the radiation efficiency of the antenna array, conductor loss can be reduced by thickening the dielectric material constituting not only the antenna but also the coupled wire 102. In contrast, the antenna array 11 of this embodiment has a configuration in which the bias line 105 is disposed on the dielectric layer 120, and the conductors of the antenna conductor 100 and coupled wire 102, through which high-frequency electromagnetic waves such as those in the terahertz band are transmitted, are disposed on the dielectric layer 119. This configuration suppresses the reduction in radiation efficiency of the antenna array due to conductor loss in the terahertz band. From the viewpoint of conductor loss, the thickness of the dielectric constituting the bonded wire 102 is preferably 1 μm or more. In one example, by setting the dielectric thickness to 2 μm or more, conductor loss in the terahertz band can be reduced to approximately 20%. Similarly, from the viewpoint of conductor loss, a wide distance can be ensured in the thickness direction between the conductor constituting the bonded wire 102 and the bias line 105 and the conductor layer 121. For the bias line 105, setting the dielectric thickness to 2 μm or less, for example, 1 μm or less, allows the bias line 105 to function as a low-impedance transmission line up to the gigahertz band. Furthermore, even when the dielectric thickness is set to 2 μm or more, connecting a shunt component composed of a resistive layer and an MIM capacitor to the bias line 105 allows the bias line 105 to function as a low-impedance transmission line, thereby suppressing low-frequency oscillation.

[0044] The length of the conductor of the coupled wire 102 is designed to satisfy the phase matching condition in either or both of the X and Y directions in FIG. 3 when connecting adjacent antennas with the coupled wire. The coupled wire 102 can be designed, for example, to have a length such that the electrical length between the RTDs of adjacent antennas is an integer multiple of 2π. That is, the length of the coupled wire 102 is set so that the length of the path through the coupled wire 102 when connecting the RTDs is an integer multiple of the wavelength of the propagating electromagnetic wave. For example, in FIG. 3, the coupled wire 102ad extending in the X direction can be set to a length such that the electrical length between the semiconductor 101a and the semiconductor 101d is 4π. The coupled wire 102ab extending in the Y direction can be set to a length such that the electrical length between the semiconductor 101a and the semiconductor 101b is 2π. Note that the electrical length here refers to the wiring length taking into account the propagation speed of the high-frequency electromagnetic wave propagating through the coupled wire 102. The electrical length of 2π corresponds to one wavelength of the electromagnetic wave propagating through the coupled wire 102. With this design, the semiconductors 101 of the active antennas 11a to 11i are mutually injection locked in phase with each other. The error range of the electrical length at which mutual injection locking occurs is ±1 / 4π.

[0045] As shown in Figures 3 and 4, elements 12 are configured so that semiconductors 101 included in active antennas 11a to 11i constituting antenna array 11 are applied with bias lines 105 arranged between the antennas. Separating the bias lines 105, which are wiring within the chip, allows for the bias control unit 13 to drive the antennas individually or on the same channel, thereby controlling the drive method. Furthermore, it is possible to adjust for operating point differences between antennas due to thickness and shape variations, wiring resistance, and other factors that occur during fabrication. This makes it possible to address frequency and phase differences between each antenna that arise when the number of active antennas is increased, thereby making it easier to achieve synchronization effects through the array. Note that bias lines 105 do not necessarily need to be arranged on the same layer, and they do not necessarily need to be separated so that all active antennas can be individually controlled. For example, bias lines may be stacked in a multilayer wiring configuration, as in element 42 shown in Figure 10 (described below), or bias lines may be provided for each antenna row, as in element 22 shown in Figure 7 (described below), so that a common bias is applied to some antennas. In this case, by reducing the number of power supply devices or wiring that constitute the bias control section 13, it is possible to reduce the power consumption of the antenna device 10 and simplify the configuration.

[0046] (Regarding the bias control section) The bias control unit 13 is connected to the control line 106 and has a function of changing the bias applied to the semiconductors 101a to 101i according to a signal received from the beam direction control unit 14. Note that in order to change the voltage for each semiconductor, the bias control unit 13 may use separate power supplies corresponding to the number of antennas, or may use a combination of a number of power supplies less than the number of antennas, variable voltage regulators, variable resistors, transistors, etc. The bias control unit 13 can use these functions to apply different voltages in parallel to each of the bias lines 105a to 105i.

[0047] 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. As described above, the oscillation frequency f of the active antenna can be calculated based on the admittance YRTD of the semiconductor 101. THz That is, the oscillation frequency f of one active antenna unit is determined. THz changes depending on the bias applied to the semiconductor 101. As the bias voltage increases, the oscillation frequency f THz The bias applied to the active antenna is determined by the range of the negative resistance region of the semiconductor 101, and the amount of frequency change differs depending on the width of the negative resistance region. Here, the "width of the negative resistance region" refers to the magnitude of the voltage difference between the lower and upper limit voltages of the negative resistance region. In this embodiment, the bias control unit 13 can perform individual bias control for each active antenna via the bias line 105. Therefore, even if the antenna array 11 includes two or more semiconductors 101 with different widths of the negative resistance region due to dimensional variations, frequency control can be easily performed.

[0048] (Regarding the beam direction control unit 14) The beam direction control unit 14 is connected to the bias control unit 13 via a control line 106 and has the function of providing a control signal to the bias control unit 13. The control signal provided to the bias control unit 13 may vary depending on the device used as the bias control unit 13. For example, if the device used as the bias control unit 13 is configured using a transistor, a voltage signal applied to the gate of the transistor may be provided as a control signal from the beam direction control unit 14 to the bias control unit 13. The beam direction control unit 14 may have, for example, an information table correlating the bias applied to each active antenna with the beam direction. In this case, the beam direction control unit 14 can provide the bias control unit 13 with a control signal that sets the applied voltage required for beamforming according to the information table. The beam direction control unit 14 may also have an information table correlating the bias applied to each active antenna with the expected phase. In this case, the beam direction control unit 14 determines the beam to be formed (the beam direction) according to, for example, the state of the transmission path between the active antenna and the communication partner device, and determines the phase value to be set in each active antenna corresponding to the beam. Then, the beam direction control unit 14 can refer to the information table to identify the bias that should be applied to each active antenna so that the phase becomes the determined phase value, and transmit a control signal corresponding to the identification result to the bias control unit 13.

[0049] Here, the occurrence of phase change due to bias change in an active antenna will be explained using FIG. 5(a). The oscillation frequency of a single active antenna is determined by the resistance and LC components of the semiconductor 101 and the resistance and LC components due to the structure of the antenna 100. Since the depletion layer capacitance of the semiconductors 101a to 101i changes as a semiconductor characteristic depending on the bias applied, the oscillation frequency of each active antenna 11a to 11i changes depending on the bias applied. In this embodiment, as described above, the active antennas 11a to 11i are coupled by coupling lines 102ab to 102hf and oscillate at the same oscillation frequency f0 due to the mutual injection locking phenomenon. Here, for example, assume that the active antenna 11a oscillates at frequency f1 due to the applied bias, and then oscillates at frequency f0 due to the mutual injection locking phenomenon between the active antenna 11a and the other active antennas 11b to 11i.

[0050] Here, the relational expression between the angular velocity difference and phase between two oscillators described in Non-Patent Document 2 is applied to this embodiment. Then, from the frequency difference between the frequency f0 at which the antenna array 11 oscillates due to mutual injection locking shown in Fig. 5(a) and the oscillation frequency f1 when the active antenna 11a is not mutually injection locked, the phase difference φ1 of the active antenna 11a is calculated by the following equation (1): TIFF0007780383000001.tif20150 Note that φ1 is the oscillation phase of the active antenna 11a, and P1 is the oscillation power. P0 is the oscillation power of the antenna array 11, and Q is the Q value of the active antenna 11a. The sharper the frequency spectrum, the higher the Q value, and it is used as an output index of the oscillation circuit. As shown in Figure 5(a), this phase difference φ1 can be changed within the range of -π / 2 to π / 2. Similarly, the other active antennas 11b to 11i can also be oscillated by changing their phase differences.

[0051] Next, as an example, focusing on the three active antennas 11a to 11c along the line A - A' in FIG. 3, the principle that enables tilting the beam from the direction perpendicular to the substrate when these active antennas radiate electromagnetic waves will be described using FIG. 5(b). For example, it is assumed that the bias applied to the active antennas 11a to 11c in the A - A' direction by the bias control unit 13 is increased step by step. That is, the bias applied to the active antenna 11a is the lowest, the bias applied to the active antenna 11c is the highest, and the bias applied to the active antenna 11b is intermediate. In this case, the oscillation frequencies f1 to f3 of the individual active antennas 11a to 11c have the relationship f1 < f2 < f3. Here, in the present embodiment, as described above, the semiconductors 101a to 101c included in the active antennas 11a to 11c inject power into each other via the coupling lines 102ab and 102bc, and the oscillation frequency becomes f0 due to the mutual injection synchronization phenomenon. At this time, when the oscillation frequency f2 of the individual active antenna 11b is equal to f0, the phase difference φ2 of the active antenna 11b after mutual injection synchronization becomes 0. On the other hand, for the active antennas 11a and 11c after mutual injection synchronization, according to the above formula (1), the phase differences φ1 and φ3 are determined based on the oscillation frequencies f1 and f3 of the individual antennas, respectively. In this case, the phase differences between the active antenna 11b and the active antennas 11a and 11c are φ2 - φ1 = -φ1 and φ3 - φ2 = φ3. Note that it is assumed that the oscillation frequency f2 of the individual active antenna 11b is not equal to f0 in many cases. In this case, the phase difference φ2 of the active antenna 11b is determined in the same manner as the active antennas 11a and 11c. Then, the phase differences between the active antenna 11b and the active antennas 11a and 11c are φ2 - φ1 and φ3 - φ2. However, what is important in beamforming is the relationship between φ2 - φ1 and φ3 - φ2. For φ2 common to both equations, even if it is assumed to be 0, there is no substantial difference. Therefore, here φ2 = 0 is set.

[0052] FIG. 5(b) illustrates the directional control of radio waves emitted from active antennas 11a-11c, the phase difference of which is determined as described above. Consider the case where adjacent active antennas are spaced apart by a common distance d and output radio waves in a direction θ. For radio waves to be emitted in the direction θ, when the leftmost antenna emits radio waves with phase α, the phase of the radio waves emitted from the antenna to its right, a distance d × sinθ ahead, must also be α. Furthermore, the phase of the radio waves emitted from the rightmost antenna, a distance 2d × sinθ ahead, must also be α. Now, assume that the phase of the radio waves emitted from the second antenna from the left is shifted by φ. In this case, if λ × (φ / 2π) = d × sinθ holds, where λ is the wavelength of the radio waves, the radio waves emitted from the second antenna from the left will be in phase with the radio waves emitted from the leftmost antenna at a position d × sinθ ahead. Therefore, once the radiation direction θ of the radio wave is determined, the phase difference to be set between adjacent antennas is determined according to the following equation (2). The phase difference between the second antenna from the left and the rightmost antenna is determined in the same manner. Therefore, for example, bias control is performed to obtain φ1 and φ3 such that φ2 - φ1 = -φ1 satisfies the φ in equation (2) above, and φ3 - φ2 = φ3 satisfies the φ in equation (2) above, thereby enabling the beam to be directed in the direction of θ. That is, the phase difference to be set between the multiple active antennas is determined based on the predetermined direction θ to which the beam should be directed, and the oscillation frequency of the oscillator of each active antenna is set to obtain that phase difference. The antenna direction θ can also be changed depending on the shape, type, and array arrangement of the antenna. In this way, the antenna device 10 according to this embodiment is capable of beamforming at any angle by controlling the bias applied to the oscillator (semiconductor 101) included in each active antenna.

[0053] (Specific materials and structural dimensions) A specific example of the antenna array 11 will be described. The antenna array 11 is a semiconductor device capable of single-mode oscillation in the frequency band of 0.45 to 0.50 THz. The substrate 122 is a semi-insulating InP substrate. The semiconductor 101 is configured with a multiple quantum well structure made of InGaAs / AlAs lattice-matched to the substrate 122, and in this embodiment, an RTD with a double barrier structure is used. This is also called an RTD semiconductor heterostructure. The current-voltage characteristics of the RTD used in this embodiment are measured to have a peak current density of 9 mA / μm 2 and the negative differential conductance per unit area is 10 mS / μm 2 The semiconductor 101 is formed in a mesa structure and is composed of a semiconductor structure including an RTD and an ohmic electrode for electrical connection to the semiconductor structure. The mesa structure is circular with a diameter of 2 μm, and the magnitude of the negative differential resistance of the RTD in this case is approximately -30 Ω per diode. In this case, the negative differential conductance (GRTD) of the semiconductor 101 including the RTD is estimated to be approximately 30 mS, and the diode capacitance (CRTD) is estimated to be approximately 10 fF.

[0054] The active antenna 11 is a patch antenna having a structure in which dielectric layers 119 and 120 are sandwiched between a conductor 100, which is a patch conductor, and a conductor layer 121, which is a ground conductor. The conductor 100 is a square patch antenna with a side length of 150 μm, and the resonator length (L) of the antenna is 150 μm. A semiconductor 101 including an RTD is integrated inside the antenna.

[0055] The conductor 100, which is a patch conductor, is made of a metal layer (metal containing Ti / Au (=5 / 300 nm)) mainly made of a thin Au film with low resistivity. The conductor layer 121, which is a ground conductor, is made of a Ti / Pd / Au layer (20 / 20 / 200 nm) and a Pd / Au layer (20 / 20 / 200 nm) with an electron concentration of 1×10 cm -3 The dielectric layer 119 is made of a 5 μm thick BCB (benzocyclobutene, manufactured by Dow Chemical Co., Ltd., ε r1The dielectric layers 118 and 120 are made of 1 μm thick silicon oxide (SiO2, plasma CVD, ε r2 =4), and the total thickness of the two layers is 2 μm.

[0056] Around the semiconductor 101, the conductor layer 121, the semiconductor 101, the via 114 made of a conductor containing Cu, the conductor 100, and the conductor of the bonded wire 102 are stacked and electrically connected in this order from the substrate 122 side. The RTD, which is the semiconductor 101, is positioned at a position shifted 40% (60 μm) of one side of the conductor 100 from the center of gravity of the conductor 100 in the resonance direction (direction A-A' in FIG. 3). The position of the RTD within the antenna determines the input impedance when feeding high frequency power from the RTD to the patch antenna. As shown in FIG. 4(b), the conductor 100 is connected to a wiring 111 on the same layer as the bias line 105 arranged on the dielectric 120 via a via 110 made of Cu. The bias line 105 and the wiring 111 are formed of a metal layer containing Ti / Au (=5 / 300 nm) stacked on the dielectric layer 120. The wiring 111 is connected to the bias control unit 13 via the bias line 105, which is a common wiring formed within the chip. The active antenna is configured such that a bias is set in the negative resistance region of the RTD included in the semiconductor 101, and the frequency f THz It is designed to achieve oscillation with a power of 0.2 mW at =0.5 THz.

[0057] The vias 110 and 114 have a cylindrical structure with a diameter of 10 μm. The wiring 111 is configured as a pattern formed of a metal layer containing Ti / Au (=5 / 300 nm) with a width of 10 μm and a length of 75 μm in the resonance direction (=A-A' direction). The via 110 is at the center in the resonance direction (=A-A' direction) and is connected to the conductor 100 at the end of the conductor 100 in the C-C' direction. This connection position is located at the center of the f THz This corresponds to a node of the electric field of the terahertz wave (i.e., a position where the amplitude of the standing wave is always 0).

[0058] The antenna array 11 is an antenna array in which active antennas are arranged in a matrix. In this embodiment, an antenna array in which nine active antennas 11a to 11i are arranged in a 3×3 matrix is ​​described as an example. Each active antenna individually transmits a frequency f THz The antennas are designed to emit terahertz waves of 100 kHz and are arranged at a pitch (spacing) of 340 μm in both the A-A' and B-B' directions. Adjacent antennas are mutually coupled by coupling wires 102 including a conductor made of Ti / Au (=5 / 300 nm), and the oscillation frequency f THz =0.5±0.02 THz, they oscillate by mutual injection locking.

[0059] (Production method) Next, a method for manufacturing (fabrication) the antenna array 11 will be described.

[0060] (1) First, an InGaAs / AlAs-based semiconductor multilayer structure constituting the semiconductor 101 including the RTD is formed by epitaxial growth on an InP substrate 122. This is formed by a method such as molecular beam epitaxy (MBE) or metalorganic vapor phase epitaxy (MOVPE).

[0061] (2) An ohmic electrode Ti / Pd / Au layer (20 / 20 / 200 nm) constituting the semiconductor 101 is formed by sputtering.

[0062] (3) The semiconductor 101 is shaped into a circular mesa shape with a diameter of 2 μm to form a mesa structure. Here, photolithography and dry etching using ICP (inductively coupled plasma) are used to form the mesa shape.

[0063] (4) After the conductor layer 121 is formed on the substrate 122 by the lift-off method on the etched surface, a silicon oxide film having a thickness of 2 μm that will become the dielectric layer 120 is formed by the plasma CVD method.

[0064] (5) On the dielectric layer 120, a Ti / Au layer (=5 / 300 nm) is formed as a conductor that constitutes the bias line 105 and the wiring 111.

[0065] (6) Using spin coating and dry etching, a 5 μm thick BCB layer is filled and planarized to form the dielectric layer 119.

[0066] (7) Via holes (contact holes) are formed by removing the BCB and silicon oxide from the portions where the vias 110 and 114 are to be formed by photolithography and dry etching. At this time, by using photolithography including grayscale exposure, the taper angles of the via holes formed in the dielectric layers 119 and 120 can also be controlled as desired.

[0067] (8) Vias 110 and 114 are formed in the via holes by a conductor containing Cu. The via holes are filled with Cu and planarized using sputtering, electroplating, and chemical mechanical polishing.

[0068] (9) An electrode Ti / Au layer (=5 / 300 nm) that will become the conductor 100 of each antenna is formed by sputtering. The conductor 100 is patterned by photolithography and dry etching using ICP (inductively coupled plasma).

[0069] (10) A silicon nitride film having a thickness of 0.1 μm is formed by plasma CVD to become the dielectric layer 118. A Ti / Au electrode layer (=5 / 300 nm) that will become the conductor constituting the bond wire 102 is formed by sputtering. The conductor of the bond wire 102 is patterned by photolithography and dry etching using ICP (inductively coupled plasma).

[0070] (11) Finally, the antenna array 11 is completed by connecting the bias line 105 and the bias control unit 13 by wire bonding or the like.

[0071] Power is supplied to the antenna device 10 from the bias control section 13, and when a bias current is supplied by applying a bias that is normally in the negative differential resistance region, the antenna device 10 operates as an oscillator.

[0072] [Embodiment 2] In the above-described embodiment, a configuration has been described in which the oscillation frequencies of the oscillators included in multiple active antennas can be individually (independently) controlled. In this embodiment, a configuration will be described in which some active antennas are grouped and common control is performed on these active antennas. FIG. 6 shows a diagram illustrating the system configuration of an antenna device 20 according to this embodiment, and FIG. 7 shows a schematic top view of the antenna device 20 as viewed from above. Note that, for simplicity, detailed description of the configuration of the antenna device 20 according to this embodiment that is the same as that of the antenna device 10 will be omitted.

[0073] 6, the antenna device 20 of this embodiment includes an element 22 including 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, similar to the antenna device 10 of the first embodiment. These elements have roughly the same functions as those of 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 the bias control unit 23 with a control signal for directing a beam in a predetermined direction. The bias control unit 23 is configured to supply a bias to each of the oscillators 201a to 201i included in each of the active antennas 21a to 21i via a bias line 205. The active antennas 21a to 21i include oscillators 201a to 201i and antennas 200a to 200i.

[0074] In this embodiment, a first group of antennas are connected to each other by coupling lines 202 for mutual injection locking, and a second group of antennas share common oscillation frequency control. For example, as shown in FIG. 7, nine active antennas 21a to 21i are arranged in a 3×3 matrix. Active antennas arranged in the X direction are coupled by coupling lines 202 to establish synchronization through mutual injection locking, and common oscillation frequency control is performed for active antennas arranged in the Y direction using a common bias line. In the example of FIG. 7, active antennas 21a, 21d, and 21g are coupled to each other by coupling lines 202ad and 202dg. Similarly, active antennas 21b, 21e, and 21h are coupled to each other by coupling lines 202be and 202eh, and active antennas 21c, 21f, and 21i are coupled to each other by coupling lines 202cf and 202fi. Mutual injection locking is established between the active antennas coupled by the coupling lines. On the other hand, active antennas 21a, 21b, and 21c are connected to a common bias line 205a, active antennas 21d, 21e, and 21f are connected to a common bias line 205d, and active antennas 21g, 21h, and 21i are connected to a common bias line 205g.

[0075] In this way, the active antennas arranged in the X direction radiate radio waves at the same frequency by establishing synchronization of the oscillation frequencies through mutual injection locking. On the other hand, by using a common bias line 205 for the active antennas arranged in the Y direction, the phase difference between the active antennas coupled by the coupling line 202 can be made common. In other words, the active antennas 21a, 21d, and 21g radiate radio waves at the same frequency by mutual injection locking. 01By appropriately setting the oscillation phase difference between these active antennas while oscillating at this frequency, it is possible to direct the beam in any direction on the XZ plane. Note that Z here refers to an axis that intersects perpendicularly with the XY plane and runs from the back to the front, and the XZ plane is a plane specified by the X and Z axes. The relationship between the oscillation phase difference and the direction of the beam is determined according to the above-mentioned formula (2). Furthermore, when the active antennas 21b, 21e, and 21h oscillate at an oscillation frequency f 02 While oscillating at an oscillation frequency f, the active antennas 21c, 21f, and 21i can direct a beam in the same direction in the XZ plane as the beams formed by the active antennas 21a, 21d, and 21g. That is, since the bias line 205 is shared, the phase difference between the active antennas 21b and 21e becomes equal to the phase difference between the active antennas 21a and 21d. Similarly, the phase difference between the active antennas 21e and 21h becomes equal to the phase difference between the active antennas 21d and 21g. Similarly, the active antennas 21c, 21f, and 21i can oscillate at an oscillation frequency f by mutual injection locking. 03 While oscillating at , the beam can be directed in the same direction in the XZ plane as the beam formed by the active antennas 21a, 21d, and 21g. In an environment where the individual differences of the oscillator 201 are sufficiently small, for example, three antenna groups, active antennas 21a to 21c, active antennas 21d to 21f, and active antennas 21g to 21i, oscillate at approximately the same oscillation frequency. Therefore, the oscillation frequency f after mutual injection locking 01 ~f 03 Even in an environment where there is a certain degree of individual difference, for example, by averaging in a group of active antennas that are the target of mutual injection locking, the oscillation frequency f 01 ~f 03 is expected to be approximately equal.

[0076] In this way, three groups, each including three active antennas, arranged in the X direction operate to direct beams in the same direction by the bias of each group of active antennas arranged in the Y direction. As a result, for example, the element 22 can be used in an environment where beam direction control is sufficient only in the XZ plane, and it is possible to form the element 22 with a relatively simple configuration. Furthermore, by reducing the number of coupling wires 202 formed, power consumption in the coupling wires 202 can be reduced, thereby suppressing power loss in the antenna device 20 as a whole. Furthermore, because the number of objects to be controlled by the bias control unit 23 is reduced, the number of power supplies and power supply circuits included in the bias control unit 23 can be reduced, and the weight of the antenna device 20 can also be reduced.

[0077] As shown in FIG. 8, three groups, each including three active antennas, arranged in the Y direction may be configured to operate by biasing each group of active antennas arranged in the X direction so that beams are directed in the same direction. This configuration makes it possible to control the beam direction in the YZ plane. Generally speaking, in an antenna array in which active antennas are arranged in a matrix, active antennas arranged in a first direction are coupled by coupling lines, while active antennas arranged in a second direction different from the first direction are not coupled by coupling lines. This allows the oscillation frequencies of the active antennas arranged in the first direction to be synchronized by mutual injection locking only. Furthermore, the oscillation frequencies before synchronization are made common for the active antennas arranged in the second direction. This allows the oscillation frequencies before mutual injection locking occurs due to coupling in the first direction to be common for the active antennas arranged in the second direction. This allows multiple groups of active antennas arranged in the first direction to be formed, and allows the multiple groups to direct beams in the same direction in a plane including the first direction and a direction perpendicular to the antenna device.

[0078] [Embodiment 3] In the above-described embodiment, an example in which an element is formed on one substrate has been described. In this embodiment, an example in which an element is formed by combining multiple substrates will be described. FIG. 9 is a top view of an element 42 according to this embodiment, and FIG. 10 is a cross-sectional view of the element 42. In the following description, detailed description of the same configuration as that of the antenna device 10 will be omitted for simplicity.

[0079] 9, the 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. Similarly to the above-described embodiment, the active antennas 41a to 41i are connected to one another via coupling wires 402, and are configured to synchronize their oscillation frequencies through mutual injection locking. Each active antenna includes a through via 437, an opening 436, an MIM capacitor 426, a resistive layer 427, and a bias line 408.

[0080] The layer configurations of the A-A' cross sections, the B-B' cross sections, and the C-C' cross sections in FIG. 9 will be described with reference to FIG. 10. Each of the active antennas 41a to 41i includes at least a conductor 400, which is the upper conductor of the patch antenna, a conductor 409, which is both a GND layer and a reflector layer, and a semiconductor 401 disposed therebetween. The semiconductor 401 is a compound semiconductor, and for example, a resonant tunneling diode (RTD) is used as the semiconductor structure 462. Each of the active antennas 41a to 41i further includes a via 403 for connecting the conductor 400 and the semiconductor 401. An upper conductor of a coupling wire 402 that couples the conductors 400 of the active antenna is disposed. A bias line 408 is disposed between the conductors 400 and 409, and the bias line 408 is located midway between the dielectric layer 404 and the dielectric layer 405. The bias line 408 is connected to the conductor 400 via a via 407. Furthermore, the conductor 409, which is a GND layer, is grounded.

[0081] The semiconductor 401 is formed by stacking an upper electrode layer 463, a semiconductor structure 462, and a lower electrode layer 464 in this order from the conductor 400 side, and these are electrically connected. The semiconductor structure 462 is a semiconductor structure having electromagnetic wave gain or nonlinearity for terahertz waves, and in this embodiment, an RTD is used. The upper electrode layer 463 and the lower electrode layer 464 also serve as electrode layers for connecting contact electrodes (ohmic or Schottky) above and below the semiconductor structure 462 with upper and lower wiring layers in order 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 metal materials known as ohmic electrodes or Schottky electrodes (such as Ti, Pd, Au, Cr, Pt, AuGe, Ni, TiW, Mo, ErAs), or semiconductors doped with impurities.

[0082] Each active antenna is composed of an antenna conductor 400, a semiconductor 401, a conductor 409 (reflector), dielectric layers 404 and 405, and a via 403 connecting the conductor 400 and the semiconductor 401. To apply a control signal to the semiconductor 401, a bias line 408 and a via 407, an MIM capacitor 426, and a resistive layer 427, which are individually provided for each active antenna, are connected to the active antenna, as shown in FIGS. 10(b) and 10(c). The MIM capacitor 426 is a capacitive element in which metal is sandwiched between dielectric layers, and is arranged to suppress low-frequency parasitic oscillations caused by a bias circuit. The active antennas are connected by a coupling wire 402 for synchronizing the antennas at terahertz frequencies.

[0083] A bonding surface BS is provided on the bottom surface of the first substrate 451 on which the antenna array and semiconductor are integrated, and the first substrate 451 is bonded to a second substrate 452 including an integrated circuit via the bonding surface BS. Here, "bonded" is defined as the first substrate 451 and the second substrate 452 sharing the same bonding surface BS. The second substrate 452 to be bonded is configured to include a second semiconductor substrate as a base material and an integrated circuit region on which a drive circuit is formed. Metal bonding such as CuCu bonding, SiO X / SiO XBonding is performed using insulator bonding such as SiO2 bonding, adhesive bonding using adhesives such as BCB, and hybrid bonding, which is a combination of these. Bonding processes include low-temperature bonding using plasma activation and conventional thermocompression bonding. Also used are bonding of semiconductor wafers of the same size, bonding of semiconductor wafers of different sizes, and bonding of multiple semiconductor chips spaced apart on a wafer (tiling).

[0084] In the antenna array 41, a semi-insulating InP substrate (4 inches) which is a compound semiconductor substrate on which the semiconductor 401 is crystal-grown is used as the dielectric layer 431 of the first substrate 451 on which the semiconductor 401 is integrated. Hereinafter, in this embodiment, the dielectric layer 431 may be referred to as the "compound semiconductor substrate 431". Hereinafter, from the viewpoint of reducing wiring inductance, the thickness of the compound semiconductor substrate 431 is thinned to 100 μm or less, for example, 10 μm or less. The plate thickness is set to the wavelength of the terahertz wave to be operated, typically λ / 10 or less, for example, λ / 20 or less. A bonding surface BS is provided on the lower surface of the compound semiconductor substrate 431 which is the base material of the first substrate 451, and a second substrate 452 including an integrated circuit is bonded to the bonding surface BS. In this embodiment, as an example, a CuCu bonding and SiO X / SiO X A tiling technique is used in which the cut-out first substrate 451 is bonded to a 12-inch Si integrated circuit substrate using hybrid bonding.

[0085] The first substrate 451 is formed by laminating 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 in this order from a bonding surface BS with the second substrate 452. Vias 403 and 407, a conductor 400, and a bias line 408 are formed in the dielectric layers 405 and 404, respectively. The conductor of the bonded wire 402 is formed in the dielectric layer 412. The bonding surface BS side of the first substrate 451 with the second substrate 452 is positioned opposite the semiconductor 401, with the conductor 409 serving as a reflector interposed therebetween. A through via 437 is formed in the compound semiconductor substrate 431 so as to penetrate the InP substrate 431. The through via 437 is made of, for example, Cu or Au. The bonding dielectric layer 448 and the electrode layer 438 are planarized at the bonding surface BS, and the bonding process is performed with the flat bonding surface BS exposed. On the second substrate 452 side, a second semiconductor substrate 434 as a base material and a dielectric layer 432 are laminated in this order, and within the dielectric layer 432, conductors 440 constituting multilayer wiring, vias 441, and an electrode layer 439 for bonding are formed. The dielectric layer 432 and the electrode layer 439 are flattened at the bonding surface BS, and the bonding process is carried out with the flat bonding surface BS exposed. The dielectric layers 432 and 448 are made of silicon oxide (SiO X ), silicon nitride (Si x N y Inorganic insulating materials such as silicon oxynitride (SiON), silicon dioxide containing carbon (SiOC), and silicon carbide (SiC) are used.

[0086] 10(a), conductor 409 is electrically connected in this order to via 437g provided in compound semiconductor substrate 431 and electrode layer 437g for bonding formed in dielectric layer 448, and reaches bonding surface BS. Conductor 440, which is the GND of second substrate 452, is connected in this order to via 441g formed in integrated circuit region 454 and electrode layer 439g for bonding, and reaches bonding surface BS. Electrode layer 438g of first substrate 451 and electrode layer 439g of second substrate 452 are electrically connected at bonding surface BS, so that the GND potential of both substrates is shared.

[0087] 10(b), a bias line 408 connected to the semiconductor 401 of the first substrate 451 is electrically connected to a bias control transistor TRb (MOS-FET) provided in an integrated circuit region 454 of the second substrate 452. The bias line 408 of the first substrate 451 is electrically connected in this order to the via 407, the wiring layer 435 provided in the opening 436 of the conductor 409, the through via 437b, and the bonding electrode layer 438b provided in the dielectric layer 448, and reaches the bonding surface BS. Similarly, the transistor TRb formed in the integrated circuit region 454 of the second substrate 452 is connected in this order to the via 441b and the bonding electrode layer 439b formed in the integrated circuit region 454, and reaches the bonding surface BS.

[0088] 10(c), bias lines 408, vias 407, 414, MIM capacitors 426, and resistive layers 427, which are individually provided for each active antenna, are connected to a first substrate 451 in order to apply a control signal to a semiconductor 401. The MIM capacitors 426 are configured such that a dielectric layer is sandwiched between a conductor 413 and a conductor 409, which is a GND layer. Similarly, an MIM capacitor 455 is provided on a second substrate 452.

[0089] The bias line 408 of the antenna array and the transistor TRa in the integrated circuit region 454 are electrically connected at the junction surface BS, thereby becoming conductive and enabling the application of control signals to each active antenna individually. The MOS-FET of the transistor TRb also serves as a bias control unit, and by operating as a switching regulator, can individually control the bias for the semiconductor 401 via the bias line 408. Alternatively, a terminal for applying a bias may be separately provided on the second substrate 452, and the transistor TRa may be operated as an analog switch that individually switches the bias for the active antennas on and off, so that a voltage can be supplied from outside the second substrate 452.

[0090] As an example of increasing the bonding strength, dummy electrode layers 438d and 439d that are not connected to signal lines may be provided on the bonding surface BS. By widely distributing the dummy electrode layers 438d and 439d in areas where wiring electrodes are not required, the bonding strength can be increased, improving yield and reliability. Furthermore, by widely distributing the GND electrode layers 438g and 439g and the dummy electrode layers 438d and 439d over the entire bonding surface BS, the influence of electromagnetic noise caused by the integrated circuit on the second substrate 452 on the terahertz antenna on the first substrate 451 can be reduced.

[0091] In a terahertz wave active array antenna, individual control of each antenna requires multiple wiring lines, such as bias lines for energizing the compound semiconductor, coupling lines for synchronizing between antennas, and control lines for injecting baseband signals into the antennas. While increasing the number of antennas is necessary to improve antenna gain, increasing the number of antennas increases wiring inductance due to layout, potentially hindering higher frequencies. In contrast, in this embodiment, a compound semiconductor antenna substrate (first substrate 451) including the antenna array and a Si integrated circuit substrate 452 are stacked using semiconductor bonding technology. This eliminates the need to integrate peripheral circuits required for active antenna array control on the compound semiconductor substrate or to implement an external connection. This suppresses the increase in inductance due to wiring, typically keeping it to less than 1 nH, thereby reducing signal loss and delay of baseband signals modulated at high frequencies of 1 GHz or higher.

[0092] Furthermore, since there are no circuits unrelated to the transmission and reception of terahertz waves around the active antenna, or the number of such circuits can be sufficiently reduced, noise due to unnecessary reflections is reduced, allowing the antenna characteristics to be maximized. When controlling the bias signal of a compound semiconductor for each antenna, it is necessary to arrange each bias wiring individually. In contrast, in this embodiment, the first substrate 451 including the antenna array can be directly connected to the integrated circuit on the second substrate 152 via the through via 437. When using an antenna array, wiring can be arranged on the back side of the compound semiconductor antenna substrate (first substrate 451) including the antenna array (i.e., on the back side of the conductor 409 serving as a reflector). This allows the number of active antennas included in the antenna array to be increased without being affected by the layout. Furthermore, the second substrate 452 including the integrated circuit can be configured with complex circuits such as detection circuits and signal processing circuits using conventional CMOS integrated circuit technology. Therefore, using a configuration such as that of this embodiment enables the sophistication and cost reduction of antenna devices, making it possible to easily utilize electromagnetic waves in the terahertz band.

[0093] [Embodiment 4] The configuration of yet another antenna device 50 will be described with reference to Figures 11 to 13. Figure 11 is a block diagram illustrating the system configuration of antenna device 50, Figure 12 is a schematic top view of antenna device 50 as viewed from above, and Figure 13 is a cross-sectional view of element 52. Note that in Figures 11 to 13, detailed description of the same configuration as antenna device 10 will be omitted for simplicity.

[0094] As shown in FIG. 11, the antenna device 50 has an element 52 including an antenna array 51 in which active antennas 51a-51i, each of which has a semiconductor 501 as an oscillator and an antenna 500, are arranged in an array. The antenna device 50 also includes a bias control unit 53 electrically connected to the element 52, and a beam direction control unit 54 that provides a signal to the bias control unit 53 via a control line 506. Note that, in this embodiment as well, the antennas included in the active antennas 51a-51i are mutually coupled by coupling lines, so that mutual injection locking occurs. The element 52 of this embodiment further includes oscillators 55a-55i that oscillate terahertz waves and are electrically connected to the active antennas 51a-51i. The oscillators 55a-55i are electrically connected to the corresponding active antennas 51a-51i, respectively. The oscillators 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 biases to the oscillators 55a to 55i individually. The bias control unit 53 also supplies a common bias to the semiconductors 501a1 to 501i1.

[0095] The oscillation units 55a to 55i are configured, for example, using microstrip line-type resonators, and as shown in FIG. 13, include semiconductors 501a2 to 501i2, such as RTDs, and resonance units 525a to 525i. For example, when focusing on the active antenna 51a in FIG. 13(a), the oscillation unit 55a connected to the active antenna 51a includes a semiconductor 501a2 and a resonance unit 525a, which are connected by a via 514a2. When focusing on the active antenna 51i in FIG. 13(b), the resonance unit 525i is connected to the bias control unit 53 through a via 524i2 and a bias line 505i. The vias 524a2 to 524i2 are vertical structures for electrically connecting the bias lines 505a to 505i to the resonance units 525a to 525i. The resonating portions 525a to 525i not only serve as components that constitute the microstrip line resonators, but also serve as electrodes for injecting current into the semiconductors 501a2 to 501i2 by being connected to the vias 524a1 to 524i1.

[0096] In one example, the vias 524a1 to 524i1 are connected to the resonator units 525a to 525i at a constant oscillation frequency f THz The vias 524a1-524i1 and the bias lines 505a-505i can be arranged at nodes of the electric field of the electromagnetic wave. In this case, the vias 524a1-524i1 and the bias lines 505a-505i are configured to have impedances that are sufficiently higher than the absolute value of the negative differential resistance of the semiconductors 501a2-501i2 in a frequency band near the oscillation frequency f0. In other words, the vias 524a1-524i1 and the bias lines 505a-505i are connected to the respective resonating units 525a-525i so as to have high impedance when viewed from the semiconductor (RTD) at the oscillation frequency f0.

[0097] The active antennas 51a to 51i are biased by a common bias line 505, and therefore, receive the same frequency f THzThe active antennas 51a to 51i oscillate at frequencies f1' to f9'. Meanwhile, the oscillators 55a to 55i are biased by different bias lines, so they oscillate at different frequencies f1 to f9. In combinations of the active antennas 51a to 51i and the corresponding oscillators 55a to 55i, mutual injection locking occurs via coupled lines 502a to 502i, causing the active antennas 51a to 51i and the oscillators 55a to 55i to oscillate at frequencies f1' to f9'. Furthermore, mutual injection locking also occurs between the active antennas 51a to 51i via coupled lines 502ab to 502hi, causing the antenna array 51 to oscillate at frequency f0. The active antennas 51a to 51i oscillate with a phase difference determined based on the difference between the oscillation frequencies f1' to f9' and the frequency f0 in the absence of mutual injection locking. This allows the antenna array 51 to emit terahertz waves TW at an oscillation frequency f0 at any angle relative to the substrate perpendicular direction.

[0098] Next, an example of the arrangement and structure on the element 52 will be described in detail with reference to FIGS. 12 and 13. A bias line 505 electrically connected to the antennas 500a to 500i is shared by each of the active antennas 51a to 51i. In one example, a bias voltage is supplied to the bias line 505 in FIG. 12 from a bias control unit 53 outside the semiconductor substrate. The element 52 has oscillators 55a to 55i corresponding to the active antennas 51a to 51i, respectively. The oscillators 55a to 55i have a configuration including, for example, a microstrip line type resonator, and are configured including a semiconductor such as an RTD and a resonator. As shown in FIG. 13(a), the semiconductors 501a to 501i are electrically connected to a conductor 521, which is a GND conductor, and are electrically connected to the corresponding antennas 500a to 500i through vias 514a1 to 514i1. The semiconductors 501a2 to 501i2 of the oscillation units 55a to 55i are also electrically connected to the conductor 521 and to the resonator units 525a to 525i through the vias 514a2 to 514i2. The resonator units 525a to 525i are also electrically connected to bias lines 505a to 505i for applying bias voltages to the semiconductors 501a2 to 501g2 through the power supply vias 524a to 524i. The bias voltage is supplied from the outside of the element 52 by the bias control unit 53 through the bias lines 505a to 505i, for example. The bias lines 505a to 505i are connected to the vias 524a to 524i and to the resonator units 525a to 525i and the vias 514a1 to 514i1. The bias voltage is supplied to the RTDs 501a2 to 501g2 through these connections.

[0099] The vias 514a2-514i2 and vias 524a-524i connected to the resonator units 525a-525i are connecting units for electrically and mechanically connecting the bias lines 505a-505i to the resonator units 525a-525i and semiconductors 501a2-501i2. In addition to serving as components constituting the microstrip line resonators, the resonator units 525a-525i also serve as electrodes for injecting current into the semiconductors 501a2-501g2 when connected to these vias. In one example, the vias 524a-524i can be positioned at nodes of the electric field of the electromagnetic waves of the oscillation frequencies f1-f9 present in the resonator units 525a-525i. At this time, the vias 524a to 524i and the resonating units 525a to 525i are configured to have impedances sufficiently higher than the absolute value of the negative differential resistance of the semiconductors 501a2 to 501g2, which are RTDs, in the frequency band around the frequencies f1 to f9. THz The resonating units 525a to 525i are connected so that the semiconductor (RTD) has high impedance.

[0100] Coupled wires 502a-502i are arranged between the antennas 500a-500i and the resonators 525a-525i. These coupled wires 502a-502i transmit signals generated in the oscillators 55a-55i to the active antennas 51a-51i. Because the signals oscillate at frequencies in the terahertz band, for example, the width, thickness, and length of the coupled wires 502a-502i must be designed as accurately as possible. For this reason, these can be formed by patterns on the substrate 522. Referring to FIG. 13(a), the coupled wires 502a-502i do not directly couple the resonators 525a-525i to the antennas 500a-500i, but rather connect by capacitive coupling. This is because only the high-frequency components of the signals to be transmitted are required to be transmitted, and DC (direct current) components are not passed, and only AC (alternating current) components are passed. It is also possible to provide a capacitive coupling portion midway along the coupled lines 502a to 502i.

[0101] 13(a) and 13(b), insulating layers and dielectric layers 518-520 are arranged around the semiconductors 501a1-501i1, semiconductors 501a2-501i2, antennas 500a-500i, resonator units 525a-525i, and coupled wires 502a-502i. By appropriately arranging these insulating layers and dielectric layers, insulation between the antennas and resonator units is ensured and the dielectric constant around the antennas and resonator units is adjusted. The dielectric constant is an important parameter because it is related to the wavelength of a high-frequency signal passing through a microstrip line such as an antenna or resonator unit. By appropriately adjusting the dielectric constant, it is possible to obtain sufficient performance from the antenna device 50.

[0102] As described above, the antenna device 50 of this embodiment has an oscillator that injects power into each active antenna to synchronize the frequencies. This configuration allows for power injection into the active antennas at a relatively high power compared to the power injection between the active antennas. This allows for a constant phase difference change with a relatively small frequency difference in the above equation (2). This facilitates phase adjustment and enables efficient beamforming. Furthermore, in this embodiment, the phase difference is changed without changing the bias applied to the active antennas, thereby reducing variations in oscillation power between the active antennas and enabling electromagnetic waves to be emitted with stronger power.

[0103] [Embodiment 5] In this embodiment, a case will be described in which the antenna device of any of the above-described embodiments is applied to a terahertz camera system (imaging system). The following description will be made with reference to FIG. 14(a). The terahertz camera system 1100 has a transmitter 1101 that emits terahertz waves and a receiver 1102 that detects terahertz waves. Furthermore, the terahertz camera system 1100 has a controller 1103 that controls the operation of the transmitter 1101 and the receiver 1102 based on an external signal, and processes an image based on the detected terahertz waves or outputs the image to the outside. The antenna device of each embodiment may be the transmitter 1101 or the receiver 1102.

[0104] Terahertz waves emitted from transmitting unit 1101 are reflected by subject 1105 and detected by receiving unit 1102. A camera system having such transmitting unit 1101 and receiving unit 1102 may also be called an active camera system. Note that in a passive camera system without transmitting unit 1101, the antenna device of each of the above-described embodiments can be used as receiving unit 1102.

[0105] By using the antenna device of each embodiment that is capable of beamforming, it is possible to improve the detection sensitivity of the camera system and obtain high-quality images.

[0106] [Embodiment 6] In this embodiment, a case will be described in which the antenna device according to any of the above-described embodiments is applied to a terahertz communication system (communication device). The following description will be given with reference to FIG. 14(b). The antenna device can be used as an antenna 1200 in the communication system. Possible communication systems include a simple ASK system, a superheterodyne system, a direct conversion system, and the like. A superheterodyne communication system 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 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. The analog waveform is converted into a digital waveform by the converter 1205. The digital waveform is then demodulated at baseband to obtain a communication signal. In the transmitter, a communication signal is modulated and then converted from a digital waveform to an analog waveform by converter 1205. It is then frequency-converted via mixer 1204 and mixer 1202 and output as a terahertz wave from antenna 1200. A direct-conversion communication system includes antenna 1200, amplifier 1211, mixer 1212, modulator / demodulator 1213, and local oscillator 1214. In the direct-conversion system, during reception, mixer 1212 directly converts the received terahertz wave into a baseband signal. During transmission, mixer 1212 converts the baseband signal to be transmitted into a terahertz signal. The other configurations are the same as those of the superheterodyne system. The antenna devices according to the above-described embodiments can perform terahertz wave beamforming by electrical control of the chip alone. This allows for alignment of radio waves between transmitters and receivers. Therefore, by using the antenna device of each embodiment capable of beamforming, it is possible to improve wireless quality such as signal-to-noise ratio in a communication system, and transmit large amounts of information over a wide coverage area at low cost.

[0107] [Other embodiments] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0108] For example, in the above-described embodiment, a method for controlling the phase difference between multiple active antennas by varying the bias applied to the RTD was described. However, this embodiment is not limited to this. That is, any antenna device can be formed in which active antennas, each including an individual oscillator, are arranged in an array and synchronized by mutual injection locking, and the phase difference can be controlled by controlling the oscillation frequency of each oscillator. Generally, this antenna device includes a first active antenna including a first oscillator and a first antenna conductor, a second active antenna including a second oscillator and a second antenna conductor, and a coupling line connecting the first antenna conductor and the second antenna conductor. This antenna device also includes at least a terminal (input line) for individually controlling the first oscillation frequency of the first oscillator and the second oscillation frequency of the second oscillator. By independently controlling the first oscillation frequency and the second oscillation frequency, the phase difference between the active antennas can be generated according to the above-described equation (2), thereby enabling control of beam direction. This antenna device may be configured as an antenna module integrated with the bias control unit 13, for example.

[0109] In the above-described embodiment, the antenna conductors included in two active antennas that are adjacent to each other in an array arrangement are coupled to each other, but this is not limiting. If wiring is possible, two antenna conductors included in two non-adjacent active antennas may also be coupled to each other.

[0110] Furthermore, in the above-described embodiment, a method for forming an antenna device using a laminated structure has been described, but the present invention is not limited to this. That is, the above discussion can also be applied to an antenna device that does not use a laminated structure. In this case, for example, the semiconductor 101 described above can be read as a semiconductor structure or any oscillator device. For other structures, it is possible to obtain an antenna device with performance similar to that of the antenna device discussed in this embodiment by designing it according to a circuit diagram such as that shown in FIG. 2.

[0111] In the above-described embodiment, the carriers are assumed to be electrons, but the present invention is not limited to this and may be implemented using holes. Materials for the substrate and dielectric may be selected according to the intended use, and include semiconductor layers such as silicon, gallium arsenide, indium arsenide, and gallium phosphide, and resins such as glass, ceramic, polytetrafluoroethylene, and polyethylene terephthalate.

[0112] Furthermore, although the above-described embodiment uses a square patch antenna as a terahertz wave resonator, the shape of the resonator is not limited to this. For example, a resonator having a structure using a patch conductor of a polygonal shape such as a rectangle or a triangle, a circle, an ellipse, or the like may be used.

[0113] Furthermore, the number of negative differential resistance elements integrated in the element is not limited to one, and a resonator including multiple negative differential resistance elements may be used. The number of lines is also not limited to one, and a configuration having multiple lines may be used. By using the antenna device described in the above-mentioned embodiments, it is possible to oscillate and detect terahertz waves.

[0114] In addition, in each of the above-described embodiments, a double-barrier RTD made of InGaAs / AlAs grown on an InP substrate has been described as the RTD. However, the present invention is not limited to these structures and material systems, and other structures and material combinations can also be used to provide the device of the present invention. For example, an RTD with a triple-barrier quantum well structure or an RTD with four or more multi-barrier quantum wells may also be used.

[0115] Furthermore, the following combinations may be used as materials for the RTD. GaAs / AlGaAs, GaAs / AlAs, InGaAs / GaAs / AlAs formed on GaAs substrate InGaAs / InAlAs, InGaAs / AlAs, InGaAs / AlGaAsSb formed on InP substrate InAs / AlAsSb and InAs / AlSb grown on InAs substrates ·SiGe / SiGe formed on a Si substrate The above-mentioned structure and materials can be appropriately selected depending on the desired frequency and the like.

[0116] [Summary of the embodiment] At least some of the above-described embodiments can be summarized as follows.

[0117] (Item 1) An antenna device for generating or detecting electromagnetic waves, 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 that couples the first antenna and the second antenna; a first terminal for receiving a signal for controlling a first oscillation frequency of the first oscillator before being synchronized by the coupled line; a second terminal for receiving a signal for controlling a second oscillation frequency of the second oscillator, the second oscillation frequency being before being synchronized by the coupled line, independently of the first oscillation frequency; An antenna device comprising:

[0118] (Item 2) the length of the path when the first oscillator and the second oscillator are connected via the coupled line is set based on the electrical length of the electromagnetic wave in the coupled line; 2. The antenna device according to item 1,

[0119] (Item 3) 3. The antenna device according to item 2, wherein the length of the coupling line is set to be an electrical length of the electromagnetic wave that is an integer multiple of 2π.

[0120] (Item 4) 4. The antenna device according to any one of items 1 to 3, wherein the first oscillator and the second oscillator are semiconductor structures including negative resistance elements.

[0121] (Item 5) 5. The antenna device according to item 4, wherein the negative resistance element is a resonant tunneling diode.

[0122] (Item 6) 6. The antenna device according to item 4 or 5, wherein the semiconductor structure of the first oscillator and the semiconductor structure of the second oscillator have the same shape.

[0123] (Item 7) the first oscillation frequency is determined based on the magnitude of a bias applied to the first oscillator, and the first terminal is a terminal that receives the bias applied to the first oscillator; the second oscillation frequency is determined based on the magnitude of a bias applied to the second oscillator, and the second terminal is a terminal that receives the bias applied to the second oscillator. 7. The antenna device according to any one of items 4 to 6,

[0124] (Item 8) 8. The antenna device according to item 7, wherein the bias having a magnitude corresponding to the negative resistance region of the negative resistance element is applied to the first oscillator and the second oscillator.

[0125] (Item 9) 9. The antenna device according to any one of items 1 to 8, wherein the first oscillation frequency and the second oscillation frequency are set based on a phase difference of the electromagnetic waves to be obtained in the first active antenna and the second active antenna after the oscillation frequencies of the first oscillator and the second oscillator are synchronized via the coupling wire, the phase difference corresponding to a direction in which a beam formed by the first active antenna and the second active antenna should point.

[0126] (Item 10) 10. The antenna device according to any one of items 1 to 9, wherein a plurality of active antennas including the first active antenna and the second active antenna are arranged in a matrix.

[0127] (Item 11) In the matrix arrangement, the antennas included in the active antennas arranged in a first direction are coupled by the coupling lines between the active antennas, and the antennas included in the active antennas arranged in a second direction different from the first direction are not coupled by the coupling lines between the active antennas, a terminal for commonly controlling the oscillation frequency of an oscillator included in each of the active antennas arranged in the second direction, the oscillation frequency being before being synchronized by the coupling line; Item 11. The antenna device according to item 10.

[0128] (Item 12) Item 12. The antenna device according to item 11, wherein the first active antenna and the second active antenna are arranged side by side in the first direction.

[0129] (Item 13) 13. The antenna device according to any one of items 1 to 12, wherein the first antenna and the second antenna are arranged at an interval equal to or less than the wavelength of the electromagnetic wave.

[0130] (Item 14) 13. The antenna device according to any one of items 1 to 12, wherein the first antenna and the second antenna are arranged at an interval that is an integral multiple of the wavelength of the electromagnetic wave.

[0131] (Item 15) 15. The antenna device according to any one of claims 1 to 14, wherein the first antenna and the second antenna are patch antennas.

[0132] (Item 16) 15. The antenna device according to any one of claims 1 to 14, wherein the first antenna and the second antenna are slot antennas.

[0133] (Item 17) 17. The antenna device according to any one of items 1 to 16, wherein the first antenna and the second antenna have the same shape.

[0134] (Item 18) 18. The antenna device according to any one of items 1 to 17, wherein the coupling line is capacitively coupled to the first antenna and the second antenna.

[0135] (Item 19) 18. The antenna device according to any one of claims 1 to 17, wherein the coupling line is directly coupled to the first antenna and the second antenna.

[0136] (Item 20) the first oscillator includes a third oscillator controlled to oscillate at a common oscillation frequency with respect to the first oscillator and the second oscillator, and a fourth oscillator controlled to oscillate at an oscillation frequency separate from the first oscillator, and the first oscillation frequency is an oscillation frequency obtained by synchronizing an oscillation frequency of the third oscillator with an oscillation frequency of the fourth oscillator; the second oscillator includes a fifth oscillator controlled to oscillate at a common oscillation frequency with respect to the first oscillator and the second oscillator, and a sixth oscillator controlled to oscillate at an individual oscillation frequency with respect to the second oscillator, and the first oscillation frequency is an oscillation frequency obtained by synchronizing an oscillation frequency of the fifth oscillator with an oscillation frequency of the sixth oscillator. 20. The antenna device according to any one of items 1 to 19, characterized in that:

[0137] (Item 21) the antenna device is formed on a first substrate including the first active antenna, the second active antenna, and a plurality of wirings through which signals for controlling the first oscillation frequency and the second oscillation frequency, respectively, are transmitted; the first substrate includes a plurality of through electrodes connected to the plurality of wirings, respectively, and the plurality of through electrodes are formed so as to reach a bonding surface for bonding the first substrate to another substrate; 21. The antenna device according to any one of items 1 to 20, wherein the plurality of through electrodes function as the first terminal and the second terminal.

[0138] (Item 22) a second substrate including a plurality of electrodes for outputting signals for controlling the first oscillation frequency and the second oscillation frequency, the plurality of electrodes are formed on a bonding surface where the second substrate is bonded to another substrate, the first substrate and the second substrate are bonded to each other at their bonding surfaces, and the plurality of electrodes on the second substrate are electrically connected to the plurality of through electrodes; 22. The antenna device according to item 21,

[0139] (Item 23) 23. The antenna device according to any one of items 1 to 22, wherein the electromagnetic waves are electromagnetic waves in the terahertz band.

[0140] (Item 24) The antenna device according to any one of items 1 to 23, a transmitter that emits the electromagnetic wave; a receiving unit that detects the electromagnetic waves; A communication device comprising:

[0141] (Item 25) The antenna device according to any one of items 1 to 23, a transmitter that emits the electromagnetic waves toward a subject; a detection unit that detects the electromagnetic waves reflected by the subject; An imaging system comprising:

[0142] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0143] 10, 20, 50: Antenna device, 11, 21, 51: Antenna array, 13, 23, 53: Bias control section, 14, 24, 54: Beam direction control section and phase control section, 101: Semiconductor (RTD), 100: Antenna conductor, 102: Coupled wire, 105, 205, 305, 408, 505: Bias line

Claims

1. An antenna device for generating or detecting electromagnetic waves, 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 wire coupling the first antenna and the second antenna; a first terminal for receiving a signal for controlling a first oscillation frequency of the first oscillator before being synchronized by the coupled line; a second terminal for receiving a signal for controlling a second oscillation frequency of the second oscillator, the second oscillation frequency being independent of the first oscillation frequency before being synchronized by the coupled wire; An antenna device comprising:

2. the length of the path when the first oscillator and the second oscillator are connected via the coupled line is set based on the electrical length of the electromagnetic wave in the coupled line; 2. The antenna device according to claim 1.

3. 3. The antenna device according to claim 2, wherein the length of the path of the coupled line is set to be an electrical length of the electromagnetic wave that is an integer multiple of 2π.

4. 2. The antenna device according to claim 1, wherein the first oscillator and the second oscillator are semiconductor structures including negative resistance elements.

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

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

7. the first oscillation frequency is determined based on the magnitude of a bias applied to the first oscillator, and the first terminal is a terminal that receives the bias applied to the first oscillator; the second oscillation frequency is determined based on the magnitude of a bias applied to the second oscillator, and the second terminal is a terminal that receives the bias applied to the second oscillator.

5. The antenna device according to claim 4.

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

9. 2. The antenna device according to claim 1, wherein the first oscillation frequency and the second oscillation frequency are set based on a phase difference of the electromagnetic waves to be obtained in the first active antenna and the second active antenna after the oscillation frequencies of the first oscillator and the second oscillator are synchronized via the coupled wire, the phase difference corresponding to a direction in which a beam formed by the first active antenna and the second active antenna should point.

10. 2. The antenna device according to claim 1, wherein a plurality of active antennas including the first active antenna and the second active antenna are arranged in a matrix.

11. In the matrix arrangement, the antennas included in the active antennas arranged in a first direction are coupled by the coupling lines, and the antennas included in the active antennas arranged in a second direction different from the first direction are not coupled by the coupling lines, a terminal for commonly controlling the oscillation frequency of an oscillator included in each of the active antennas arranged in the second direction, the oscillation frequency being before being synchronized by the coupling line; 11. The antenna device according to claim 10.

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

13. 2. The antenna device according to claim 1, wherein the first antenna and the second antenna are arranged at a distance equal to or less than the wavelength of the electromagnetic wave.

14. 2. The antenna device according to claim 1, wherein the first antenna and the second antenna are arranged at an interval that is an integral multiple of the wavelength of the electromagnetic wave.

15. 2. The antenna device according to claim 1, wherein the first antenna and the second antenna are patch antennas.

16. 2. The antenna device according to claim 1, wherein the first antenna and the second antenna are slot antennas.

17. 2. The antenna device according to claim 1, wherein the first antenna and the second antenna have the same shape.

18. 2. The antenna device according to claim 1, wherein the coupling line is capacitively coupled to the first antenna and the second antenna.

19. 2. The antenna device according to claim 1, wherein the coupling line is directly coupled to the first antenna and the second antenna.

20. the first oscillator includes a third oscillator controlled to oscillate at a common oscillation frequency with respect to the first oscillator and the second oscillator, and a fourth oscillator controlled to oscillate at an oscillation frequency separate from the first oscillator, and the first oscillation frequency is an oscillation frequency obtained by synchronizing an oscillation frequency of the third oscillator with an oscillation frequency of the fourth oscillator; the second oscillator includes a fifth oscillator controlled to oscillate at a common oscillation frequency with respect to the first oscillator and the second oscillator, and a sixth oscillator controlled to oscillate at an individual oscillation frequency with respect to the second oscillator, and the first oscillation frequency is an oscillation frequency obtained by synchronizing an oscillation frequency of the fifth oscillator with an oscillation frequency of the sixth oscillator.

2. The antenna device according to claim 1.

21. the antenna device is formed on a first substrate including the first active antenna, the second active antenna, and a plurality of wirings through which signals for controlling the first oscillation frequency and the second oscillation frequency, respectively, are transmitted; the first substrate includes a plurality of through electrodes connected to the plurality of wirings, respectively, and the plurality of through electrodes are formed so as to reach a bonding surface for bonding the first substrate to another substrate; The antenna device according to claim 1 , wherein the plurality of through electrodes function as the first terminal and the second terminal.

22. a second substrate including a plurality of electrodes for outputting signals for controlling the first oscillation frequency and the second oscillation frequency, the plurality of electrodes are formed on a bonding surface where the second substrate is bonded to another substrate, the first substrate and the second substrate are bonded to each other at their bonding surfaces, and the plurality of electrodes on the second substrate are electrically connected to the plurality of through electrodes; 22. The antenna device according to claim 21.

23. 2. The antenna device according to claim 1, wherein the electromagnetic waves are in the terahertz band.

24. an antenna device according to any one of claims 1 to 23; a transmitter that emits the electromagnetic wave; a receiving unit that detects the electromagnetic waves; A communication device comprising:

25. an antenna device according to any one of claims 1 to 23; a transmitter that emits the electromagnetic waves toward a subject; a detection unit that detects the electromagnetic waves reflected by the subject; An imaging system comprising:

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