Antenna device and relay

Abstract

Provided are an antenna device and a relay in which a wider band is achieved.　The antenna device comprises: a spiral antenna that is provided facing a window glass and that transmits and receives radio waves in a first frequency band; and a transmission unit that is connected to the spiral antenna, transmits a signal of the first frequency band, and transmits and receives radio waves in a second frequency band lower than the first frequency band.

Description

Antenna device and repeater

[0001] The present disclosure relates to an antenna device and a repeater.

[0002] Conventionally, there has been a wideband antenna including a spiral conductive portion formed on a first surface of a plate-like member, a first spiral radiating portion formed on the first surface, and a second spiral radiating portion formed on a second surface of the plate-like member opposite the first surface (see, for example, Patent Document 1).

[0003] U.S. Patent No. 4,525,720

[0004] However, there is a limit to how much bandwidth can be achieved using only a spiral antenna, as with conventional wideband antennas (spiral antennas).

[0005] Therefore, an object of the present invention is to provide an antenna device and a repeater that achieve a wider bandwidth.

[0006] An antenna device according to an embodiment of the present disclosure includes a spiral antenna that is disposed opposite a window glass and transmits and receives radio waves in a first frequency band, and a transmission unit that is connected to the spiral antenna and transmits signals in the first frequency band and transmits and receives radio waves in a second frequency band that is lower than the first frequency band.

[0007] Furthermore, it is possible to provide an antenna device and a repeater with a wider bandwidth.

[0008] 1 is a diagram showing an example of a building in which an antenna device and a repeater according to an embodiment are installed, as viewed from the side; FIG. 2 is a diagram showing an example of frequency band divisions in the antenna device and the repeater according to an embodiment; FIG. 3 is a diagram showing an example of a circuit configuration of a communication device of a repeater according to an embodiment; FIG. 4 is a diagram showing an example of a configuration of an antenna device according to an embodiment; FIG. 5 is a diagram showing an example of a configuration of an antenna device according to an embodiment; FIG. 6 is a diagram showing an example of a configuration of a reflector of the antenna device according to an embodiment; FIG. 7 is a diagram showing an example of a configuration of a spiral antenna of the antenna device according to an embodiment; FIG. 8 is a diagram showing an example of a configuration of a spiral antenna of the antenna device according to an embodiment; FIG. 9 is a diagram showing an example of a configuration of a spiral antenna of the antenna device according to an embodiment; Fig. 1 is a diagram showing an example of a simulation result of frequency characteristics of radiation efficiency of a spiral antenna and a transmission cable of an antenna device of an embodiment. Fig. 2 is a characteristic diagram showing an example of a relationship between the size of a reflecting conductor of a reflector of an antenna device of an embodiment and a lower limit frequency in the front direction of radio waves radiated in the front direction. Fig. 3 is a diagram showing an example of radiation directivity obtained by a simulation model of a spiral antenna and a reflector of an antenna device of an embodiment. Fig. 4 is a diagram showing an example of radiation directivity obtained by a simulation model of a spiral antenna and a reflector of an antenna device of an embodiment. Fig. 5 is a diagram showing an example of a state in which an antenna device of an embodiment radiates radio waves.

[0009] Hereinafter, embodiments to which the antenna device and repeater of the present disclosure are applied will be described. In the following, the same elements will be denoted by the same reference numerals, and duplicated descriptions may be omitted.

[0010] In the following description, an XYZ coordinate system is defined. The direction parallel to the X axis (X direction), the direction parallel to the Y axis (Y direction), and the direction parallel to the Z axis (Z direction) are perpendicular to one another. In the following description, the length, width, thickness, etc. of each part may be exaggerated to make the configuration easier to understand. Furthermore, terms such as parallel, right angle, orthogonal, horizontal, vertical, up and down, etc., are allowed to deviate to the extent that they do not impair the effects of the embodiments.

[0011] In the following description, "radio waves" refers to a type of electromagnetic wave, and generally, electromagnetic waves below 3 THz are called radio waves. Hereinafter, electromagnetic waves emitted from outdoor base stations or relay stations will be referred to as "radio waves," and electromagnetic waves in general will be referred to as "electromagnetic waves." In addition, in the following, "millimeter waves" or "millimeter wave band" will include not only the frequency band of 30 GHz to 300 GHz, but also the quasi-millimeter wave band of 24 GHz to 30 GHz.

[0012] The repeater of the embodiment can function as a repeater that receives radio waves arriving from a base station or relay station, performs processing such as amplification without converting the frequency, and then radiates the radio waves. The repeater of the embodiment can also function as a repeater that receives radio waves arriving from a base station, performs processing such as frequency conversion and amplification, and then radiates the radio waves.

[0013] The repeater of the embodiment is capable of transmitting and receiving radio waves in a first frequency band and radio waves in a second frequency band between the base station or the relay station. The second frequency band is lower than the first frequency band.

[0014] The radio waves in the first frequency band are radio waves in a frequency band equal to or greater than a predetermined frequency. The predetermined frequency is approximately 1 GHz to 3 GHz. Examples of the radio waves in the first frequency band include millimeter wave bands such as those of fifth-generation mobile communication systems (5G), and radio waves in a frequency band equal to or greater than a predetermined frequency of Sub-6, Long Term Evolution (LTE), Long Term Evolution (LTE-Advanced) (LTE-A), or Ultra Mobile Broadband (UMB).

[0015] The radio waves in the second frequency band are radio waves with a frequency below a predetermined frequency. The predetermined frequency is approximately 1 GHz to 3 GHz. As an example, the radio waves in the second frequency band are radio waves with a frequency below the predetermined frequency of Sub-6, LTE, LTE-A, or UMB, such as a fifth-generation mobile communication system (5G).

[0016] In addition, when the repeater of the embodiment relays and radiates radio waves received from a base station or relay station, it may perform processing such as amplification on the radio waves in the first frequency band and the second frequency band described above without converting the frequency, and then radiate the radio waves.

[0017] Furthermore, when relaying and emitting radio waves received from a base station or relay station, the repeater of the embodiment may perform processing such as frequency conversion and amplification on the radio waves in the first frequency band or the radio waves in the second frequency band described above, and radiate the radio waves as radio waves of IEEE802.11 (Wi-Fi (registered trademark)), IEEE802.16 (WiMAX (registered trademark)), IEEE802.20, UWB (Ultra-Wideband), Bluetooth (registered trademark), LPWA (Low Power Wide Area), etc. Of these, Wi-Fi and WiMAX can be used as wireless LANs (Local Area Networks).

[0018] 1 is a diagram showing an example of a building 1 in which an antenna device 100A and a repeater 100 according to an embodiment are installed, as viewed from the side. The repeater 100 includes the antenna device 100A and a device main body 101. The device main body 101 includes a communication device 150.

[0019] 1 shows base stations BS1 and BS2 and a smartphone 50 in addition to a building 1, an antenna device 100A, and a repeater 100. The base stations BS1 and BS2 are examples of external devices. Although FIG. 1 shows base stations BS1 and BS2, the external devices of the repeater 100 may be relay stations. Even if the external devices of the repeater 100 are relay stations, the repeater 100 communicates with the base stations via the relay stations.

[0020] In the following, the operation and configuration of the antenna device 100A and the repeater 100 may be described using the operation of receiving radio waves by the antenna device 100A and the repeater 100. The operation of transmitting radio waves by the antenna device 100A and the repeater 100 is the opposite operation to the operation of receiving radio waves, and therefore, the description of the operation of transmitting radio waves by the antenna device 100A and the repeater 100 may be omitted.

[0021] The building 1 may be a detached house, a building, an apartment building, or a commercial facility such as a shopping mall or a department store, an airport, a factory, a power facility, a government building, a train station, or a bus stop. The window 10 is used in these buildings 1. The window 10 includes a windowpane 11 and a window frame (the window frame on the building 1 side). The repeater 100 is installed indoors in the building 1, for example, and relays radio waves arriving from the outdoors to the indoor side and relays radio waves from the indoor side to the outdoors. Note that, as an example, a configuration in which the antenna device 100A and the repeater 100 are installed indoors in the building 1 will be described. However, the antenna device 100A and the repeater 100 may be installed outdoors as long as there are areas where radio waves in a first frequency band, described later, cannot reach and areas where they can reach.

[0022] 1, as an example, the XYZ coordinate system is defined based on the indoor main surface of the window glass 11. The indoor main surface of the window glass 11 is the main surface parallel to the XY plane on the +Z direction side of the window glass 11. The building 1 has a wall 1W parallel to the XY plane on the -Z direction side, and the window 10 is provided in the wall 1W.

[0023] As an example, base station BS1 transmits and receives radio waves in a first frequency band, and base station BS2 transmits and receives radio waves in a second frequency band. As described above, the first frequency band is a frequency equal to or greater than a predetermined frequency, and the second frequency band is a frequency less than the predetermined frequency. The predetermined frequency is approximately 1 GHz to 3 GHz. Note that, although the explanation here is divided into base station BS1 and base station BS2, one base station may transmit and receive radio waves in the first frequency band and the second frequency band. Furthermore, radio waves transmitted and received by three or more base stations may be radio waves in the first frequency band and the second frequency band.

[0024] <Frequency Band Division> Fig. 2 is a diagram showing an example of frequency band division in the antenna device 100A and the repeater 100. In Fig. 2, the horizontal axis represents frequency. Below, as an example, a configuration will be described in which the predetermined frequency located at the boundary between the first frequency band and the second frequency band is 1 GHz, the first frequency band is 1 GHz to 6 GHz, and the second frequency band is 600 MHz to 1 GHz. It is preferable that the first frequency band includes a portion of the frequency band from 1.5 GHz to 5 GHz.

[0025] The first frequency band is a frequency band of radio waves transmitted and received by base station BS1, and is divided into frequency band A and frequency band B by a boundary frequency. Frequency band A is a frequency band within the first frequency band that is higher than the boundary frequency, and frequency band B is a frequency band within the first frequency band that is equal to or lower than the boundary frequency. Frequency band A is an example of a high frequency band within the first frequency band, and frequency band B is an example of a low frequency band within the first frequency band.

[0026] The boundary frequency is the frequency at which radio waves either penetrate or do not penetrate the wall 1W of the building 1. The boundary frequency is approximately 1 GHz to 3 GHz, depending on the material and structure of the wall 1W. It is more preferable that the boundary frequency is a frequency included in the frequency band of 2.6 GHz to 3.3 GHz. Below, an example in which the boundary frequency is 3 GHz will be described.

[0027] Therefore, in the following description, radio waves with frequencies of 3 GHz or less will pass through the wall 1W of the building 1, and radio waves with frequencies higher than 3 GHz will not pass through the wall 1W of the building 1.

[0028] In the following description, a frequency band that does not transmit through the wall 1W of the building 1 is referred to as a non-transmitted frequency band, and a frequency band that transmits through the wall 1W of the building 1 is referred to as a transmitted frequency band. The non-transmitted frequency band includes frequency band A in the first frequency band, and the transmitted frequency band includes frequency band B in the first frequency band and the second frequency band.

[0029] Note that when radio waves do not penetrate the wall 1W of the building 1, this does not only mean that the radio waves do not penetrate the wall 1W at all, but also means that the radio waves that penetrate the wall 1W are so weak that practically sufficient radio wave strength cannot be obtained for communication using terminals such as a smartphone 50 or a PC (Personal Computer) inside (indoors) the wall 1W of the building 1.

[0030] Radio waves in the opaque frequency band do not penetrate the wall 1W of the building 1, and therefore penetrate only through the window glass 11 of the window 10 to enter the building. Radio waves in the opaque frequency band have a high frequency and are highly directional, so they only reach the line of sight (LOS) area of ​​the window 10, making it easy for blind zones to form inside the building. The window glass 11 of the window 10 is an entry point for radio waves in the opaque frequency band in the building 1.

[0031] Furthermore, radio waves in the transmission frequency band penetrate the window glass 11 of the window 10 and the wall 1W of the building 1 and enter the building, so they reach not only the line-of-sight (LOS) area of ​​the window 10 but also the entire building 1. For this reason, radio waves in the transmission frequency band are unlikely to cause dead zones indoors.

[0032] The antenna device 100A includes a spiral antenna 110 provided on the indoor main surface of the window glass 11 of the window 10 to transmit and receive radio waves in the first frequency band to and from the outdoor base station BS1. Because the first frequency band includes an opaque frequency band (frequency band A), it is preferable that the spiral antenna 110 have directivity facing the base station BS1.

[0033] Furthermore, radio waves in frequency band B, which are part of the first frequency band included in the transmission frequency band, can pass through wall 1W and propagate indoors from various directions other than through window 10. Therefore, the spiral antenna 110 provided on the indoor-facing main surface of window glass 11 can receive radio waves in frequency band B.

[0034] The spiral antenna 110 is connected to the communication device 150 in the device main body 101 via a transmission cable 120. The transmission cable 120 is an example of a transmission section, and a coaxial cable can be used as an example. The transmission cable 120 is not limited to a coaxial cable, and can be any type of unbalanced line. The transmission cable 120 can be a transmission line with adjusted characteristic impedance, such as a microstrip line or a strip line formed on a flexible substrate, for example. However, the following describes a configuration in which a coaxial cable is used as the transmission cable 120. Because a coaxial cable has low transmission loss, it is particularly effective when the transmission cable 120 is long.

[0035] The repeater 100 includes, as an example, multiple spiral antennas 110. FIG. 1 illustrates multiple spiral antennas 110 collectively, with each spiral antenna 110 connected to a single transmission cable 120. Since FIG. 1 illustrates four transmission cables 120 as an example, a configuration in which four spiral antennas 110 are provided is also illustrated. For example, using four spiral antennas 110 enables MIMO (Multi-Input Multi-Output) communication. When MIMO communication is performed, a right-handed polarized spiral antenna 110 and a left-handed polarized spiral antenna 110 may be arranged adjacent to each other. The repeater 100 may also include a single spiral antenna 110.

[0036] Furthermore, a matching layer 140 is provided between each spiral antenna 110 and the indoor main surface of the window glass 11. As an example, the spiral antenna 110 is adhered to the window glass 11 by a fixing member such as a holder (not shown). The matching layer 140 is held between the window glass 11 and the spiral antenna 110 by a holder (not shown). Note that if there is no particular problem in not including the matching layer 140, the antenna device 100A does not need to include the matching layer 140.

[0037] In addition, when the repeater 100 performs beamforming using multiple spiral antennas 110 as a phased array antenna, a liquid crystal phase shifter may be provided on the +Z direction side of the spiral antenna 110, or a phase shifter other than a liquid crystal phase shifter may be provided.

[0038] Furthermore, in order to realize the antenna device 100A with a wider bandwidth, in order to realize communication in a second frequency band in addition to the first frequency band in which the spiral antenna 110 can communicate, it is necessary to use an antenna separate from the spiral antenna 110, or to use a larger spiral antenna that is capable of communication in the second frequency band instead of the spiral antenna 110. However, adding an antenna that transmits and receives radio waves in the second frequency band complicates the configuration of the antenna device 100A. Furthermore, because the second frequency band has a lower frequency, the antenna that transmits and receives radio waves in the second frequency band is larger than the spiral antenna 110. Furthermore, using a larger spiral antenna that is capable of communication in the second frequency band results in an increase in the size of the antenna device.

[0039] Therefore, in order to transmit and receive radio waves in the second frequency band to and from the outdoor base station BS2, the repeater 100 uses the common mode to transmit and receive radio waves in the second frequency band through the transmission cable 120. In other words, the repeater 100 uses the transmission cable 120 as an antenna for transmitting and receiving radio waves in the second frequency band.

[0040] Since radio waves in the second frequency band have a low frequency and are less likely to travel in a straight line, antenna directivity is not a significant issue. Furthermore, radio waves in the second frequency band penetrate the wall 1W and enter the interior of the building, so transmission and reception are possible even if the antenna is not located within the line-of-sight (LOS) area of ​​the window 10. For this reason, there is no problem even if the antenna for transmitting and receiving radio waves in the second frequency band is located outside the line-of-sight (LOS) area of ​​the window 10, such as the transmission cable 120.

[0041] As described above, the antenna device 100A receives radio waves in the non-transparent frequency band (frequency band A) of the first frequency band transmitted from the base station BS1 using the spiral antenna 110 located within the line-of-sight (LOS) area of ​​the window 10. The antenna device 100A also receives radio waves in frequency band B, which is within the transmitted frequency band of the first frequency band, using the spiral antenna 110. The antenna device 100A also receives radio waves in the second frequency band transmitted from the base station BS2 using the transmission cable 120. The transmission cable 120 can receive radio waves in the second frequency band even if it is located outside the line-of-sight (LOS) area of ​​the window 10.

[0042] As an example, the repeater 100 performs amplification processing, or amplification processing and frequency conversion processing, on radio waves in the first frequency band received by the spiral antenna 110 and radio waves in the second frequency band received by the transmission cable 120 in the communication device 150, and outputs the results indoors from the antenna of the communication device 150.

[0043] By outputting radio waves from the repeater 100 indoors, the radio waves can be easily received by indoor terminals such as smartphones 50 and PCs.

[0044] Furthermore, by using the existing transmission cable 120 as an antenna, there is no need to add a new antenna for transmitting and receiving radio waves in the second frequency band, and the configuration of the antenna device 100A can be simplified and made smaller.

[0045] <Circuit Configuration of Communication Device 150> Fig. 3 is a diagram showing an example of the circuit configuration of communication device 150. Communication device 150 is provided inside device main body 101 (see Fig. 1). Fig. 3 shows the configuration of a portion of the overall configuration of communication device 150 that corresponds to one spiral antenna 110. Spiral antenna 110 is connected to communication device 150 via transmission cable 120.

[0046] If the distance between the spiral antenna 110 and the communication device 150 is long, the transmission loss of radio waves in the transmission cable 120 between the spiral antenna 110 and the communication device 150 increases. Therefore, in order to reduce the transmission loss of radio waves, it is preferable to attach the communication device 150 to the window glass 11 or to the wall 1W or ceiling surrounding the window 10, for example. Alternatively, the communication device 150 may be placed on the frame of a bay window, for example. However, a certain length is necessary to generate radiation from the transmission cable 120 using the common mode.

[0047] As an example, the communication device 150 includes an array antenna 150A, a wireless module 151, a switch 152, an LNA (Low Noise Amplifier) ​​153, a mixer 154, an ADC (Analog to Digital Converter) 155, a DAC (Digital to Analog Converter) 156, a mixer 157, and a PA (Power Amplifier) ​​158.

[0048] When there are multiple spiral antennas 110, the switch 152, LNA 153, mixer 154, ADC 155, DAC 156, mixer 157, and PA 158 of the communication device 150 are provided one for each spiral antenna 110. The communication device 150 includes the same number of components from the switch 152 to the PA 158 as the number of spiral antennas 110. As an example, there is only one wireless module 151, which is common to the multiple spiral antennas 110.

[0049] As an example, the array antenna 150A is provided inside the housing of the communication device 150, or outside the communication device 150 and inside the device main body 101 (see FIG. 1). The array antenna 150A is an array antenna used when the communication device 150 transmits and receives radio waves inside the building 1. The array antenna 150A may be provided outside the housing of the communication device 150, or may be provided outside the device main body 101 (see FIG. 1). The communication device 150 may also be configured to include a single antenna instead of multiple antennas arranged in an array like the array antenna 150A.

[0050] The wireless module 151 is configured, for example, by an MCU (Micro Controller Unit), and includes a control unit 151A and a relay unit 151B that performs relay processing. The control unit 151A and the relay unit 151B are functional blocks that represent the functions executed by the MCU.

[0051] When receiving radio waves with spiral antenna 110, control unit 151A switches three-terminal switch 152 to connect spiral antenna 110 to LNA 153. When transmitting radio waves with spiral antenna 110, control unit 151A switches three-terminal switch 152 to connect spiral antenna 110 to PA 158.

[0052] The relay unit 151B includes, as an example, a Wi-Fi (registered trademark) communication unit and is connected to the array antenna 150A. The relay unit 151B transmits radio waves based on a digital signal input from the ADC 155 from the array antenna 150A to the interior of the building 1. When the relay unit 151B transmits radio waves to the interior of the building 1 via the array antenna 150A, the radio waves in the first or second frequency band received from the base station BS1 or BS2 by the spiral antenna 110 or the transmission cable 120 are relayed, and the radio waves are radiated to the interior of the building 1 where the communication device 150 is located. This radiates radio waves over a wide area inside the building 1, making it easier for indoor devices such as the smartphone 50 to receive the radio waves. The communication unit that radiates the radio waves relayed indoors by the relay unit 151B is not limited to Wi-Fi, and may be Bluetooth (registered trademark) or the like.

[0053] Furthermore, relay unit 151B performs relay processing on radio waves transmitted from an indoor terminal such as smartphone 50 and received by array antenna 150A, and outputs the result to DAC 156. This allows array antenna 150A to receive radio waves from a wide range inside building 1, making it easier for indoor terminals such as smartphone 50 to transmit radio waves.

[0054] The LNA 153 is provided between the switch 152 and the mixer 154, amplifies the radio waves received by the spiral antenna 110 or the transmission cable 120, and outputs the amplified signals while preventing deterioration of the signal-to-noise ratio.

[0055] The mixer 154 demodulates the radio wave output from the LNA 153 by mixing it with a local signal (LO) and outputs an IF (Intermediate Frequency) signal. By converting the signal into an IF signal, digital conversion can be easily performed by the ADC 155.

[0056] The ADC 155 converts the IF signal output from the mixer 154 into a digital signal and outputs the digital signal to the wireless module 151 .

[0057] When the relay unit 151B of the wireless module 151 performs relay processing on the signal received by the array antenna 150A and transmits the signal from the spiral antenna 110 or the transmission cable 120, the DAC 156 converts the signal output by the relay unit 151B into an analog signal and outputs the IF signal to the mixer 157.

[0058] The mixer 157 mixes the IF signal with a local signal (LO) to modulate it, and outputs the modulated signal to the PA 158 .

[0059] The PA 158 amplifies the signal output from the mixer 157 and outputs the amplified signal to the transmission cable 120 via the switch 152. As a result, radio waves are emitted from the transmission cable 120 or the spiral antenna 110.

[0060] When the radio waves handled by the communication device 150 are Sub-6, the communication device 150 may not include the mixers 154 and 157. In this case, the signal input to the ADC 155 and the signal output from the DAC 156 are not IF signals but signals in the Sub-6 frequency band.

[0061] Although the configuration in which the communication device 150 converts and amplifies the frequency has been described here, the communication device 150 may be configured to perform processing such as amplification without converting the frequency. In this case, an indoor smartphone 50 or the like can transmit and receive radio waves in the first frequency band and the second frequency band.

[0062] <Specific Configuration of Antenna Device 100A> The specific configuration of the antenna device 100A will be described using Figures 4A, 4B, and 4C in addition to Figure 1. Figures 4A and 4B are diagrams showing an example of the configuration of the antenna device 100A. Figure 4C is a diagram showing an example of the configuration of the reflector 130 of the antenna device 100A. Figures 4A and 4B simplify the configuration and show one spiral antenna 110 and one transmission cable 120. Figures 4A and 4B also show the window glass 11. The window glass 11 has an indoor surface 11A and an outdoor surface 11B.

[0063] The antenna device 100A includes a spiral antenna 110, a transmission cable 120, a reflector 130, a spacer 135, and a matching layer 140. The antenna device 100A is attached, for example, via a holder (not shown) so as to face the indoor surface 11A of the window glass 11. For example, such a holder is made of a resin that is transparent to visible light, and holds the substrate of the spiral antenna 110 while being fixed to the surface 11A of the window glass 11 with double-sided tape or the like.

[0064] "Transparent" to visible light means that the luminous transmittance is at least 40%, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. Resin materials that satisfy this condition include acrylic resins such as polymethyl methacrylate, cycloolefin resins, polycarbonate resins, polyethylene terephthalate (PET), and the like. The holder may also be made of transparent glass. A transparent holder can minimize obstruction of the view through the window glass 11.

[0065] <Spiral Antenna 110> The spiral antenna 110 has radiating portions formed on both sides of a substrate. The spiral antenna 110 is, for example, transparent to visible light. A matching layer 140 is provided between the spiral antenna 110 and the surface 11A of the window glass 11. For example, the spiral antenna 110 is attached to the window glass 11 using a fixing member such as a holder so that the spiral antenna 110 is parallel to the surface 11A of the window glass 11 and is spaced approximately 10 mm from the surface 11A. Here, a configuration in which the spiral antenna 110 is disposed parallel to the surface 11A of the window glass 11 is described; however, the spiral antenna 110 does not have to be parallel to the surface 11A of the window glass 11. The detailed configuration of the spiral antenna 110 will be described later using Figures 4A to 4C.

[0066] <Transmission cable 120> The transmission cable 120 has one end connected to the feed point and ground potential point of the spiral antenna 110, and the other end connected to the communication device 150 in the device main body 101. The transmission cable 120 is, for example, a coaxial cable. One end of the transmission cable 120 is connected to the feed point and ground potential point of the spiral antenna 110 via a coaxial connector 125.

[0067] The transmission cable 120 transmits signals in the first frequency band between the spiral antenna 110 and the communication device 150. The transmission cable 120 also transmits signals in the second frequency band between the spiral antenna 110 and the communication device 150, and functions as an antenna for radio waves in the second frequency band, thereby transmitting and receiving radio waves in the second frequency band.

[0068] The transmission cable 120 transmits and receives radio waves in the second frequency band of 600 MHz to 1 GHz, which is lower than the first frequency band, and therefore preferably has a length of 200 mm or more, more preferably 500 mm or more, and even more preferably 1000 mm or more.

[0069] 1, 4A, and 4B, the transmission cable 120 is connected to the lower side of the spiral antenna 110, but it may be connected to the side or upper side of the spiral antenna 110. By routing the transmission cable 120 connecting the spiral antenna 110 and the communication device 150 along the wall 1W or the like, it is possible to receive radio waves in the second frequency band that propagate indoors through the wall 1W from various directions.

[0070] <Reflector 130> As an example, the reflector 130 is fixed to the +Z direction side of the spiral antenna 110 via a spacer 135. The distance between the reflector 130 and the spiral antenna 110 is denoted as d. As an example, the reflector 130 has a rectangular shape in a plan view. As an example, the reflector 130 is transparent to visible light. The numerical range of the distance d will be described later.

[0071] The reflector 130 has a substrate 131 and a reflective conductor 132. The reflective conductor 132 is an example of a reflective portion. The substrate 131 is made of any material that can support the reflective conductor 132.

[0072] Furthermore, the substrate 131 may be transparent to visible light. "Transparent" to visible light means that the luminous transmittance is at least 40% or more, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more.

[0073] As an example, a resin substrate (resin film) may be used as the substrate 131. Examples of resin materials that satisfy the above conditions include acrylic resins such as polymethyl methacrylate, cycloolefin resins, polycarbonate resins, and polyethylene terephthalate (PET). Alternatively, a glass plate may be used as the substrate 131. Examples of glass plates that satisfy the above conditions include soda-lime glass, alkali-free glass, Pyrex (registered trademark) glass, and quartz glass. Here, as an example, a configuration in which the substrate 131 is a resin substrate will be described.

[0074] The reflective conductor 132 may be a conductor such as a metal thin film, but if the substrate 131 is transparent to visible light, it is preferable from the viewpoint of visibility that the reflective conductor 132 be formed from a mesh-like metal thin film such as copper, nickel, or gold.

[0075] The reflective conductor 132 is made of zinc oxide (ZnO), tin oxide (SnO ２ The transparent conductive film may be formed of a transparent conductive film such as tin-doped indium oxide (ITO) or indium oxide-tin oxide (IZO), a metal nitride such as titanium nitride (TiN) or chromium nitride (CrN), or a low-e film for low-e (low emissivity) glass.

[0076] As described above, when the substrate 131 is transparent to visible light and the reflective conductor 132 is made of a transparent conductor such as a mesh-like metal thin film, the reflector 130 only needs to have a visual transmittance of 50% or more.

[0077] The length of one side of the reflecting conductor 132 and the distance between the reflecting conductor 132 and the spiral antenna 110 are set to predetermined values ​​taking into consideration the radiation direction of radio waves in the first frequency band toward the +Z direction, etc. These will be described later.

[0078] <Spacer 135> The spacer 135 is a member that holds the reflector 130 relative to the spiral antenna 110. As an example, the spacers 135 are provided at the upper and lower ends between the spiral antenna 110 and the reflector 130, respectively, and are elongated rod-shaped members that extend in the X direction. The spacers 135 are not limited to these two rod-shaped members and may be, for example, frame-shaped members. As an example, the spacer 135 is made of resin that is transparent to visible light and is fixed to the substrate of the spiral antenna 110 or the like with double-sided tape or the like, and the reflector 130 is also fixed to it with double-sided tape or the like. Furthermore, as an example, the spacer 135 may be made of glass that is transparent to visible light.

[0079] The spacer 135 being transparent to visible light has the same meaning as the holder that holds the substrate of the spiral antenna 110 being transparent to visible light. The resin material that can be used to make the spacer 135 is, for example, the same as the resin material used to make the holder of the spiral antenna 110. The spacer 135 may also be made of transparent glass. The transparency of the spacer 135 can reduce obstruction of the view of the window glass 11.

[0080] The spacer 135 is not limited to a configuration that holds the reflector 130 relative to the spiral antenna 110, as long as it can hold the reflector 130 on the +Z direction side of the spiral antenna 110. For example, the spacer 135 may be configured to hold the reflector 130 relative to the surface 11A of the window glass 11.

[0081] <Matching layer 140> The matching layer 140 is provided between the surface 11A of the window glass 11 and the spiral antenna 110. The matching layer 140 is larger than the spiral antenna 110 in a plan view, and is arranged so as to encompass the outer edge of the spiral antenna 110 in a plan view. A holder that holds the matching layer 140 between the window glass 11 and the spiral antenna 110 may be fixed to the −Z direction side of the substrate of the spiral antenna 110, or may be fixed to the surface 11A of the window glass 11.

[0082] Radio waves are attenuated when they pass through the window glass 11. In order to suppress radio wave attenuation (loss), a matching layer 140 may be provided. When the spiral antenna 110 transmits and receives radio waves, the matching layer 140 adjusts the electrical length of the radio waves passing through the window glass 11 to match the impedance, thereby reducing loss. Such a matching layer 140 can be made of, for example, polycarbonate, acrylic, COP (cycloolefin polymer), PET (polyethylene terephthalate), polystyrene, glass, or the like.

[0083] 5A, 5B, and 5C are diagrams showing an example of the configuration of the spiral antenna 110. The spiral antenna 110 has a substrate 110A, a first radiating portion 111, a second radiating portion 112, and a feeder line 113. The substrate 110A is an example of a base portion.

[0084] <Substrate 110A> The substrate 110A is a plate-like member that is rectangular in plan view. The substrate 110A has a surface 110A1 located on the -Z direction side (the window glass 11 side) and a surface 110A2 located on the opposite side of the surface 110A1. The surface 110A1 is an example of a first surface, and the surface 110A2 is an example of a second surface. The surface 110A1 is provided with a first radiating portion 111 and a feeder line 113, and the surface 110A2 is provided with a second radiating portion 112. Note that, here, a configuration in which the substrate 110A is a plate-like member that is rectangular in plan view will be described. However, the base of the spiral antenna 110 may have any shape as long as it is a member that has the surfaces 110A1 and 110A2, and may be a configuration other than a plate-like member such as a substrate.

[0085] The substrate 110A is formed of any material that is transparent to the radio waves radiated from the base stations BS1 and BS2 and that can support the first radiating portion 111, the second radiating portion 112, and the feeder line 113. "Transparent to the radiated radio waves" means, for example, that the transmission loss is 10 dB or less. "The substrate 110A is transparent to the radiated radio waves" means that the transmission loss of the substrate 110A is 10 dB or less, preferably 6 dB or less, more preferably 3 dB or less, and even more preferably 1 dB or less.

[0086] The substrate 110A may be transparent to visible light. "Transparent" to visible light means that the luminous transmittance is at least 40% or more, preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more.

[0087] As an example, a resin substrate (resin film) may be used as the substrate 110A. Examples of resin materials that satisfy the above conditions include acrylic resins such as polymethyl methacrylate, cycloolefin resins, polycarbonate resins, and polyethylene terephthalate (PET). Alternatively, a glass plate may be used as the substrate 110A. Examples of glass plates that satisfy the above conditions include soda-lime glass, alkali-free glass, Pyrex (registered trademark) glass, and quartz glass. Here, as an example, a configuration in which the substrate 110A is a resin substrate will be described.

[0088] <First radiating portion 111> The first radiating portion 111 is provided on the surface 110A1 of the substrate 110A and has a feed point 111A, an open end 111B, a connection portion 111C, and an extension portion 111D. The first radiating portion 111 is a radiating portion that extends in a spiral shape between the feed point 111A located toward the center in a planar view and the open end 111B located on the outer side in a planar view. The feed line 113 also has a spiral shape in a planar view, and the first radiating portion 111 extends between the feed point 111A and the open end 111B.

[0089] The first radiating portion 111 is configured with a conductive film formed on the surface 110A1. The conductive film that configures the first radiating portion 111 will be described later together with the conductive films that configure the second radiating portion 112 and the power supply line 113.

[0090] The portion of first radiating portion 111 between feed point 111A and connection portion 111C is a logarithmic spiral portion. Furthermore, the portion of first radiating portion 111 between connection portion 111C and open end 111B is an extension portion 111D. Extension portion 111D is added to the logarithmic spiral portion from feed point 111A to connection portion 111C, and is, for example, a linear conductor portion. For example, such first radiating portion 111 is integrally formed from feed point 111A to open end 111B.

[0091] The first radiating portion 111 has two outer edges in plan view, which are an inner edge and an outer edge sandwiching the line width of the spiral pattern of the first radiating portion 111 in plan view.

[0092] The logarithmic spiral portion is a portion of first radiating portion 111 in which two outer edges have a shape based on a logarithmic spiral, and is a portion between feed point 111A and connection portion 111C. As an example, the spiral shape of first radiating portion 111 having the logarithmic spiral portion is a shape that spirals counterclockwise from feed point 111A on the center side toward open end 111B in a planar view seen from the −Z direction side.

[0093] The logarithmic spiral portion has a shape in which its line width increases from the feed point 111A on the central side toward the connection portion 111C. The inner and outer edges of the first radiating portion 111 do not have to perfectly match the logarithmic spiral shape in a planar view, and may deviate to some extent. Because the first radiating portion 111 has a line width, the inner and outer edges, particularly on the central side, may be interrupted midway through the logarithmic spiral or may deviate from the logarithmic spiral shape. The inner and outer edges of the first radiating portion 111 do not have to perfectly match the logarithmic spiral shape in a planar view due to, for example, adjustments to the shape of the details when forming the first radiating portion 111 with a mesh-like metal thin film, as described below. The phrase "the outer edge of the logarithmic spiral portion has a shape based on a logarithmic spiral in a planar view" means that deviation from such a strict logarithmic spiral is permitted.

[0094] Note that, as an example, a configuration will be described in which the first radiating portion 111 includes a logarithmic spiral portion having a shape based on a logarithmic spiral, but the shape of the outer edge of the spiral portion included in the first radiating portion 111 may be a spiral shape other than a logarithmic spiral. For example, the shape of the outer edge of the spiral portion included in the first radiating portion 111 may have a shape based on a spiral shape such as an Archimedean spiral.

[0095] As an example, the line width of the extension 111D is constant from the connection 111C to the open end 111B. The extension 111D is provided to generate a current of a common mode component. Details thereof will be described later with reference to FIGS. 7A and 7B. The shape and size of the extension 111D are not limited to those shown in FIG. 5B, and may have various shapes and sizes. Modified examples of the spiral antenna 110 will be described later with reference to FIGS. 8A and 8B.

[0096] Furthermore, the length between feed point 111A and open end 111B of first radiating portion 111 is λe / 6 to λe / 3 or 2λe / 3 to 5λe / 6, where λe is the electrical length of the wavelength of radio waves in the second frequency band. The reason for this will be described later with reference to Figures 7A and 7B.

[0097] <Second radiating portion 112> The second radiating portion 112 is provided on the surface 110A2 of the substrate 110A, and has an open end 112A, an end portion 112B, a connection portion 112C, and an extension portion 112D. The second radiating portion 112 is maintained at ground potential by connecting the end portion 112B to the shielded wire via the coaxial connector 125 of the transmission cable 120. The second radiating portion 112 overlaps with the feeder line 113 in a plan view, and together with the feeder line 113, form a microstrip line.

[0098] As an example, the second radiating section 112 has a shape obtained by rotating the first radiating section 111 by 180 degrees in a plan view around the center of the spiral of the first radiating section 111. In other words, the second radiating section 112 has a shape in which the open end 112A, the end section 112B, the connection section 112C, and the extension section 112D correspond to the feed point 111A, the open end 111B, the connection section 111C, and the extension section 111D of the first radiating section 111, respectively.

[0099] The second radiating section 112 has a configuration in which the first radiating section 111 is rotated 180 degrees in a plan view, so that the feed point 111A becomes an open end 112A, and an end section 112B corresponding to the open end 111B is connected to the shield wire of the transmission cable 120. For this reason, a description of the shapes of the open end 112A, end section 112B, connecting section 112C, and extension section 112D of the second radiating section 112 will be omitted.

[0100] Furthermore, as will be described in detail later, having the second radiating portion 112 and the first radiating portion 111 have the same shape and length, which has the advantage of providing good current characteristics due to the symmetry between the second radiating portion 112 and the first radiating portion 111. However, because the second radiating portion 112 serves as the ground line of the microstrip line, its relationship with the electrical length λe, such as the length of the first radiating portion 111, is not that important. Therefore, the length between the open end 112A and the end 112B of the second radiating portion 112 may be shorter than the length between the feed point 111A and the open end 111B of the first radiating portion 111. Making the second radiating portion 112 shorter than the first radiating portion 111 allows the spiral antenna 110 to be made smaller.

[0101] <Feeder Line 113> The feeder line 113 has a connection portion 113A and an end portion 113B, and has a spiral shape in a plan view. The feeder line 113 has a constant line width from the connection portion 113A to the end portion 113B.

[0102] The connection portion 113A is connected to the feed point 111A of the first radiating portion 111. The end portion 113B is connected to the core wire of the transmission cable 120 via the coaxial connector 125, and thereby receives the signal of the first frequency band transmitted from the device main body 101 as input.

[0103] In a plan view, the feed line 113 extends in a spiral shape between the spiral portions from the feed point 111A to the open end 111B of the first radiating portion 111. The gap between the spiral portion of the feed line 113 and the spiral portion of the first radiating portion 111 becomes wider from the connecting portion 113A toward the end portion 113B.

[0104] The spiral portion of the feed line 113 from the connection portion 113A to the end portion 113B overlaps with the second radiating portion 112 in a planar view. The feed line 113 forms a microstrip line together with the second radiating portion 112 at ground potential. The length of the portion of the feed line 113 from the connection portion 113A to the end portion 113B is equal to the length of the second radiating portion 112 from the open end 112A to the end portion 112B.

[0105] As an example, such a feeder line 113 has a shape based on a logarithmic spiral. The meaning of the feeder line 113 having a shape based on a logarithmic spiral is the same as the meaning of the first radiating section 111 having a shape based on a logarithmic spiral. For example, the logarithmic spiral may be interrupted midway toward the center, and the shape of the feeder line 113 may not completely match the shape of a logarithmic spiral in a planar view due to adjustments to the shape of the details when forming the feeder line 113 from a mesh-like metal thin film, which will be described later. The meaning of the feeder line 113 having a shape based on a logarithmic spiral in a planar view is that deviations from such a strict logarithmic spiral are permitted.

[0106] <Conductive Films of First Radiating Section 111, Second Radiating Section 112, and Power Supply Line 113>

[0107] When the substrate 110A is transparent to visible light, it is preferable from the viewpoint of visibility that the first radiating section 111, the second radiating section 112, and the power supply line 113 are formed from a mesh-like thin metal film such as copper, nickel, or gold.

[0108] The first radiating portion 111, the second radiating portion 112, and the power supply line 113 are made of zinc oxide (ZnO), tin oxide (SnO ２ The transparent conductive film may be formed of a transparent conductive film such as tin-doped indium oxide (ITO) or indium oxide-tin oxide (IZO), a metal nitride such as titanium nitride (TiN) or chromium nitride (CrN), or a low-e film for low-e (low emissivity) glass.

[0109] As described above, when the substrate 110A is transparent to visible light and the first radiating section 111, the second radiating section 112, and the power supply line 113 are made of a transparent conductor such as a mesh-like metal thin film, the spiral antenna 110 only needs to have a visual transmittance of 50% or more.

[0110] <Radiation Directivity of Spiral Antenna 110> Fig. 6A is a diagram showing an example of radiation directivity obtained from a simulation model of spiral antenna 110. The radiation directivity shown in Fig. 6A is the radiation directivity of the simulation model of spiral antenna 110 alone, and is the radiation directivity in a state where reflector 130 is not present.

[0111] 6A shows the radiation directivity in the AZ (Azimuth) direction as a gain [dBi]. The AZ direction is a direction within the XZ plane in FIGS. 5A and 5B, with 0 degrees corresponding to the −Z direction and 180 degrees corresponding to the +Z direction.

[0112] FIG. 6A shows the radiation directivity when the length of the substrate 110A in the X direction is set to 160 mm and the length in the Y direction is set to 120 mm, and radio waves of 0.7 GHz, 1.7 GHz, 2.5 GHz, 3.7 GHz, and 4.5 GHz are radiated from the spiral antenna 110 in an electromagnetic field simulation.

[0113] It was confirmed that substantially uniform radiation was obtained at 0 degrees and 180 degrees at all frequencies of 0.7 GHz, 1.7 GHz, 2.5 GHz, 3.7 GHz, and 4.5 GHz.

[0114] <Frequency Characteristics of Gain of Spiral Antenna 110> Fig. 6B is a diagram showing an example of frequency characteristics of gain obtained from a simulation model of spiral antenna 110. The frequency characteristics of gain shown in Fig. 6B are frequency characteristics of gain for the simulation model of spiral antenna 110 alone, that is, frequency characteristics of gain in a state in which reflector 130 is not present.

[0115] FIG. 6B shows FrontGain (gain in the 0 degree direction) and PeakGain (maximum gain), and the two almost overlap.

[0116] The length of the substrate 110A in the X direction was set to 160 mm, and the length in the Y direction was set to 120 mm, and in an electromagnetic field simulation, the frequency of the radio waves radiated from the spiral antenna 110 was increased from 700 MHz, thereby obtaining the gain frequency characteristic shown in Fig. 6B. As a result, the gain began to rise from 700 MHz, and the gain frequency characteristic was obtained, showing a gain of approximately 1.7 [dBi] to approximately 3.8 [dBi], which is a level usable for wireless communication.

[0117] Fig. 6C is a diagram showing an example of the frequency characteristics of gain obtained from the simulation model of spiral antenna 110. The frequency characteristics of gain shown in Fig. 6C are the frequency characteristics of gain for the simulation model of spiral antenna 110 alone, that is, the frequency characteristics of gain in a state in which reflector 130 is not present.

[0118] The length of the substrate 110A in the X direction was set to 70 mm and the length in the Y direction to 55 mm, and the frequency of the radio waves radiated from the spiral antenna 110 was increased from 700 MHz, thereby obtaining the gain frequency characteristics shown in Figure 6C.

[0119] As a result, the gain rises from about 1.4 GHz, and the frequency characteristics of the gain were obtained, showing a gain level usable for wireless communication of about 1.2 [dBi] to about 3.5 [dBi]. The FrontGain (gain in the 0 degree direction) and the PeakGain (maximum gain) almost overlapped.

[0120] From the results in FIG. 6A, it was confirmed that the spiral antenna 110 radiates radiation evenly in the −Z direction (front direction) and the +Z direction (rear direction).

[0121] 6B and 6C , it was confirmed that reducing the size of the spiral antenna 110 increases the lower limit frequency of the frequency band at which a level of gain usable for wireless communication is obtained. Increasing the lower limit frequency enables the miniaturization of the spiral antenna 110. The lower limit frequency is the lowest frequency of the frequency band at which a level of gain usable for wireless communication is obtained, and is the lowest frequency of the first frequency band at which the spiral antenna 110 can communicate.

[0122] Compared to a spiral antenna 110 with lengths of 160 mm and 120 mm in the X and Y directions, the size of a spiral antenna 110 with lengths of 70 mm and 55 mm in the X and Y directions is less than one-fourth the size. It is preferable to increase the lower limit frequency of the first frequency band of the spiral antenna 110 to reduce the size of the spiral antenna 110. This makes it possible to provide a spiral antenna 110 that achieves both a wider bandwidth and a smaller size.

[0123] <Principle of Radiation in Transmission Cable 120> Fig. 7A is a diagram illustrating the principle of radiation in the transmission cable 120. Fig. 7A shows the first radiating portion 111, the feeder line 113, and the second radiating portion 112 stretched out in a straight line. Fig. 7A also shows with arrows the currents flowing through the first radiating portion 111, the second radiating portion 112, and the feeder line 113 at a certain moment. The direction of the arrow indicates the direction of the current, and the length of the arrow indicates the magnitude of the current.

[0124] In Fig. 7A, the first radiating portion 111 does not have the extension portion 111D, and the position of the open end 111B1 is equal to the position of the connecting portion 111C shown in Fig. 5B. The second radiating portion 112 does not have the extension portion 112D, and the position of the end portion 112B1 is equal to the position of the connecting portion 112C shown in Fig. 5C. That is, in Fig. 7A, the lengths of the first radiating portion 111 and the second radiating portion 112 are equal, and are shorter by the length of the extension portions 111D and 112D compared to Figs. 5B and 5C.

[0125] 7A , the length L of the first radiating portion 111 is set to L=λe / 2, where λe is the electrical length of the wavelength of radio waves in the second frequency band. Because the lengths of the first radiating portion 111 and the second radiating portion 112 are equal, the length of the second radiating portion 112 is also λe / 2. Furthermore, because the lengths of the second radiating portion 112 and the feeder line 113 are equal, the length of the feeder line 113 is also λe / 2.

[0126] In this state, a standing wave occurs in the second frequency band in the first radiating portion 111, so the current at the feed point 111A (connection portion 113A) is zero amperes. Also, because the open end 112A of the second radiating portion 112 is an open end, the current at the open end 112A is zero amperes. Then, currents of opposite phases are generated in the feed line 113 and the second radiating portion 112 that form the microstrip line.

[0127] Because the currents in the second radiator 112 and the feeder line 113 are in opposite phases, the currents flowing in the core wire and shield wire of the coaxial cable serving as the transmission cable 120 are also in opposite phases, resulting in a non-radiating state for the transmission cable 120. This is because the radio waves radiated from the currents flowing in the core wire and shield wire cancel each other out. Note that this also holds true when the lengths of the second radiator 112 and the feeder line 113 in Fig. 7A are different from those described above.

[0128] <Explanation of Operation in Fig. 7B> Next, a description will be given using Fig. 7B. Fig. 7B is a diagram illustrating the principle of radiation in the transmission cable 120. Fig. 7B shows the first radiating portion 111, the feeder line 113, and the second radiating portion 112 stretched out in a straight line. Fig. 7B also shows with arrows the currents flowing through the first radiating portion 111, the second radiating portion 112, and the feeder line 113 at a certain moment. The direction of the arrow indicates the direction of the current, and the length of the arrow indicates the magnitude of the current.

[0129] In Fig. 7B, the first radiating portion 111 has an extension portion 111D. Furthermore, the second radiating portion 112 does not have the extension portion 112D (see Fig. 5C), and the position of the end portion 112B1 is the same as the position of the connection portion 112C shown in Fig. 5C. In Fig. 7B, the length of the feed line 113 is the same as the length of the second radiating portion 112. The lengths of the second radiating portion 112 and the feed line 113 shown in Fig. 7B are the same as the lengths of the second radiating portion 112 and the feed line 113 shown in Fig. 7A.

[0130] 7B , because the length of the first radiating portion 111 is longer than λe / 2, a standing wave is generated in the first radiating portion 111, and as a result, the current at the feed point 111A (connection portion 113A) does not become zero amperes. Also, because the open end 112A of the second radiating portion 112 is an open end, the current at the open end 112A is zero amperes. In this state, the currents flowing through the feed line 113 and the second radiating portion 112, which constitute the microstrip line, are different from each other but are not in opposite phase.

[0131] Because the currents in the second radiating portion 112 and the feeder line 113 are not in opposite phase, the currents flowing in the core wire and shield wire of the coaxial cable serving as the transmission cable 120 are also not in opposite phase, and the transmission cable 120 enters a radiation state. This is because the radio waves radiated from the currents flowing in the core wire and shield wire do not cancel each other out. Note that this also holds true when the lengths of the second radiating portion 112 and the feeder line 113 in Fig. 7A are not the above-mentioned lengths.

[0132] In this way, when the phases of the currents flowing through the core wire and shield wire of the coaxial cable serving as the transmission cable 120 are different, the current contains a common mode component. Because the antenna device 100A transmits and receives radio waves in the second frequency band through the transmission cable 120 using the common mode, an element that cancels out the common mode component, such as a balun, is not connected between the spiral antenna 110 and the transmission cable 120. In other words, one of the features of the antenna device 100A is that it does not include a balun.

[0133] In order for the antenna device 100A to transmit and receive radio waves in the second frequency band via the transmission cable 120 using the common mode, it is necessary that the currents flowing in the core wire and shield wire of the coaxial cable serving as the transmission cable 120 do not have opposite phases. The condition for the currents flowing in the core wire and shield wire to have opposite phases is that the length of the first radiating portion 111 is λe / 2 or an integer multiple of λe / 2.

[0134] To include an in-phase component in the current flowing through the core wire and the shield wire to an extent that the common mode can be utilized, it is sufficient to shift the length of the first radiating portion 111 by λe / 6 from λe / 2. For the same reason, the minimum length of the first radiating portion 111 is λe / 6. From the perspective of miniaturizing the spiral antenna 110, the maximum length of the first radiating portion 111 is, for example, 5λe / 6, which is λe minus λe / 6.

[0135] For this reason, the length between the feed point 111A and the open end 111B of the first radiating portion 111 may be λe / 6 to λe / 3, or 2λe / 3 to 5λe / 6, which allows for both a wider bandwidth due to the generation of a common mode in the transmission cable 120 and a smaller spiral antenna 110.

[0136] <Length of First Radiating Portion 111 and Length of Extension Portion 111D> Figures 8A and 8B are diagrams showing modified examples of the spiral antenna 110. In the spiral antenna 110 shown in Figures 8A and 8B, the length of the first radiating portion 111 is different from the length of the first radiating portion 111 shown in Figure 5B.

[0137] The first radiating portion 111 shown in Fig. 8A does not have the extension portion 111D (see Fig. 5B ), and the position of the open end 111B is located closer to the feed point 111A than the connection portion 111C shown in Fig. 5B . The length from the feed point 111A to the open end 111B of such a first radiating portion 111 is shorter than λe / 2, where λe is the electrical length of the wavelength of radio waves in the second frequency band.

[0138] As explained using FIG. 7A , when the length of the first radiating section 111 is λe / 2, resonance of the current in the second frequency band occurs in the first radiating section 111, so that the current at the feed point 111A becomes zero amperes, and the radiation caused by the currents in the second radiating section 112 and the feed line 113 is canceled out.

[0139] 8A , by making the length from the feed point 111A of the first radiating portion 111 to the open end 111B shorter than λe / 2, the condition where the currents in the second radiating portion 112 and the feed line 113 are in opposite phase is not met. As a result, the radio waves radiated from the currents flowing in the core wire and shield wire of the coaxial cable serving as the transmission cable 120 do not cancel each other out.

[0140] That is, by making the length from the feed point 111A to the open end 111B of the first radiating portion 111 shorter than λe / 2, a current of a common mode component is generated, and radio waves are emitted from the transmission cable 120. This enables the transmission cable 120 to transmit and receive radio waves in the second frequency band.

[0141] The first radiating portion 111 shown in Fig. 8B has an extension portion 111D that is longer than the extension portion 111D shown in Fig. 5B. The extension portion 111D extends from the connection portion 111C in the +Y direction, bends in the -X direction, and extends to just before a corner on the -X and +Y direction sides of the substrate 110A. The open end 111B is located just before a corner on the -X and +Y direction sides of the substrate 110A.

[0142] The length from the feeding point 111A to the open end 111B of the first radiating portion 111 is longer than λe / 2, where λe is the electrical length of the wavelength of radio waves in the second frequency band.

[0143] 8B , by making the length from the feed point 111A of the first radiating portion 111 to the open end 111B longer than λe / 2, the condition where the currents in the second radiating portion 112 and the feed line 113 are in opposite phases is not met. As a result, the radio waves radiated from the currents flowing in the core wire and shield wire of the coaxial cable serving as the transmission cable 120 do not cancel each other out.

[0144] That is, by making the length from the feed point 111A of the first radiating portion 111 to the open end 111B longer than λe / 2, a current of a common mode component is generated, and radio waves are emitted from the transmission cable 120. This enables the transmission cable 120 to transmit and receive radio waves in the second frequency band.

[0145] Even when the length from the feed point 111A to the open end 111B of the first radiating portion 111 is set to be longer than λe / 2, the length between the feed point 111A and the open end 111B of the first radiating portion 111 only needs to be 2λe / 3 to 5λe / 6. This is to achieve both a further broadband due to the generation of a common mode in the transmission cable 120 and a compact spiral antenna 110.

[0146] Fig. 9 is a diagram showing an example of simulation results of the frequency characteristics of the radiation efficiency of the spiral antenna 110 and the transmission cable 120. The simulation results shown in Fig. 9 were obtained by electromagnetic field simulation. In Fig. 9, the horizontal axis represents frequency [GHz], and the vertical axis represents radiation efficiency (Total Radiation Efficiency) [%].

[0147] In the simulation, the length of the spiral antenna 110 in the X direction was set to 70 mm, the length in the Y direction was set to 55 mm, and the length of the transmission cable 120 was set to 800 mm.

[0148] The radiation efficiency when the length of the extension 111D is set to 25 mm (solid line) and the radiation efficiency when the length of the extension 111D is set to 0 mm (dashed line) are shown.

[0149] As shown in FIG. 9, it was confirmed that the frequency band in which the radiation efficiency is high shifts when the length of the extension portion 111D is 25 mm and when it is 0 mm.

[0150] When the length of the extension portion 111D is 25 mm, the frequency bands with a radiation efficiency of 60% or higher were approximately 0.4 GHz, approximately 0.6 GHz, and approximately 1.4 GHz to approximately 1.8 GHz. The band of approximately 1.4 GHz to approximately 1.8 GHz included in the first frequency band and the band of approximately 0.6 GHz included in the second frequency band were obtained. It is believed that the band of approximately 1.4 GHz to approximately 1.8 GHz was radiation from the spiral antenna 110, and the band of approximately 0.6 GHz was radiation from the transmission cable 120.

[0151] Furthermore, when the length of the extension portion 111D was 0 mm, the frequency bands in which the radiation efficiency was 60% or higher were the band of approximately 0.9 GHz and the band of approximately 1.45 GHz to approximately 1.9 GHz. The band of approximately 1.45 GHz to approximately 1.9 GHz, which is included in the first frequency band, and the band of approximately 0.9 GHz, which is included in the second frequency band, were obtained. It is believed that the band of approximately 1.45 GHz to approximately 1.9 GHz was radiation from the spiral antenna 110, and the band of approximately 0.9 GHz was radiation from the transmission cable 120.

[0152] When the length of the extension portion 111D is 0 mm, the overall radiation efficiency tends to be lower than when the length of the extension portion 111D is 25 mm. However, it was found that even when the length of the extension portion 111D is 0 mm, the radiation of the transmission cable 120 is not completely canceled out, and a certain degree of radiation can be obtained.

[0153] As described above, it has been confirmed that by changing the length of the extension portion 111D, it is possible to adjust the first frequency band of radiation by the spiral antenna 110 and the second frequency band of radiation by the transmission cable 120. The length of the extension portion 111D can be set so that a desired frequency band can be obtained from each of the first frequency band and the second frequency band.

[0154] 10A is a characteristics diagram showing an example of the relationship between the size of the reflecting conductor 132 of the reflector 130 and the front-direction lower-limit frequency of radio waves radiated in the front direction. The front-direction lower-limit frequency is the lower-limit frequency of radio waves radiated in the front direction of the antenna device 100A, and is different from the lower-limit frequency of the frequency band at which a gain at a level usable for wireless communication is obtained, as shown in FIGS. 6B and 6C .

[0155] Here, as an example, the reflecting conductor 132 is square in plan view, and the size of the reflecting conductor 132 is the length (mm) of one side. The front direction is the direction facing the outside of the window glass 11 with respect to the spiral antenna 110, and is the -Z direction with respect to the spiral antenna 110. The rear direction is the +Z direction with respect to the reflecting conductor 132 of the reflector 130 located on the +Z direction side of the spiral antenna 110.

[0156] The lower limit frequency in the front direction is the lower limit frequency of the frequency band where the gain of radio waves on the front side of the spiral antenna 110 is 5 dB or more greater than the gain of radio waves on the back side of the reflecting conductor 132. The gain of radio waves on the back side of the reflecting conductor 132 and the gain of radio waves on the front side of the spiral antenna 110 are gains obtained at points that are the same distance from the spiral antenna 110 in the Z direction.

[0157] In the simulation, it was confirmed that the radiation intensity in the −Z direction and the radiation intensity in the +Z direction of the spiral antenna 110 changed by changing the size of the reflecting conductor 132 .

[0158] 10A , when the size of the reflective conductor 132 was set to 15 mm, 20 mm, 25 mm, 30 mm, and 45 mm, the lower limit frequency in the front direction decreased from approximately 4 GHz to approximately 3 GHz as the size of the reflective conductor 132 increased from 15 mm to 30 mm. Furthermore, when the size of the reflective conductor 132 was larger than 30 mm, the degree of decrease in the lower limit frequency in the front direction tended to decrease, but at 45 mm, it was approximately 2.8 GHz.

[0159] From these results, it was confirmed that the front direction lower limit frequency changes depending on the size of the reflective conductor 132. It was also confirmed that radio waves in a frequency band equal to or greater than the front direction lower limit frequency in the first frequency band are reflected in the -Z direction by the reflective conductor 132, and radio waves in a frequency band less than the front direction lower limit frequency in the first frequency band propagate in the +Z direction without being reflected by the reflective conductor 132. The front direction lower limit frequency obtained in this simulation was approximately 2.8 GHz to approximately 4 GHz. It is possible to further lower the front direction lower limit frequency by further increasing the size of the reflective conductor 132.

[0160] Incidentally, among the radio waves in the first frequency band radiated in the +Z direction from the spiral antenna 110, radio waves below the lower limit frequency in the front direction are not reflected in the -Z direction by the reflecting conductor 132, and therefore do not propagate outdoors but propagate indoors. In addition, the lower limit frequency in the front direction can be set to about 3 GHz, which is the boundary frequency.

[0161] Therefore, by adjusting the size of the reflecting conductor 132 and setting the frontal lower limit frequency to the boundary frequency (3 GHz) between frequency bands A and B, the following state can be obtained. That is, among the radio waves radiated from the spiral antenna 110 in the -Z direction, radio waves in frequency band A can be radiated toward the window glass 11, and among the radio waves radiated from the spiral antenna 110 in the +Z direction, radio waves in frequency band A can be reflected by the reflecting conductor 132 and radiated toward the window glass 11. Furthermore, among the radio waves radiated from the spiral antenna 110 in the -Z direction, radio waves in frequency band B can be radiated toward the window glass 11, and among the radio waves radiated from the spiral antenna 110 in the +Z direction, radio waves in frequency band B can be radiated toward the indoors. The radio waves in frequency band B radiated toward the indoors propagate through the wall 1W to the outdoors.

[0162] As described above, by adjusting the size of the reflective conductor 132 and setting the frontal lower limit frequency to the desired boundary frequency, radio waves in frequency band A can be radiated toward base station BS1 through the window glass 11. "Through the window glass 11" means that the radio waves are transmitted through the window glass 11. Furthermore, among the radio waves radiated from the spiral antenna 110 in the -Z direction, radio waves in frequency band B can be radiated toward base station BS1 through the window glass 11. Furthermore, among the radio waves radiated from the spiral antenna 110 in the +Z direction, radio waves in frequency band B can be transmitted through the wall 1W and propagated outdoors. Radio waves in frequency band B propagated outdoors are reflected by the walls of the building, etc., and reach base station BS1. Therefore, a state is achieved in which all radio waves radiated from the spiral antenna 110 reach base station BS1.

[0163] To set the front lower limit frequency to the desired boundary frequency in this way, if the effective wavelength on the reflecting conductor 132 of the current generated by the radio wave at the front lower limit frequency (boundary frequency) is λcg, the length of one side of the reflecting conductor 132 should be set to λcg / 3 or more and 2λcg / 3 or less. This range can be obtained by converting the size of the reflecting conductor 132 in the result of Figure 10A into the effective wavelength λcg. The effective wavelength λcg is the electrical length of the reflecting conductor 132 at wavelength λc, and is expressed as λcg = λc × {(εr + 1) / 2} １／２ where λc is the wavelength in free space of the radio wave at the boundary frequency (lower limit frequency in the front direction). εr is the relative dielectric constant of the substrate 131.

[0164] By arranging the reflecting conductor 132 on the opposite side of the spiral antenna 110 from the window glass 11, it is possible to increase the amount of radiation of radio waves in frequency band A that travels toward base station BS1 through the window glass 11. Also, it is possible to ensure that radio waves in frequency band B travel along two paths: one that travels through the window glass 11 toward base station BS1, and another that travels through the wall 1W, is reflected by a building wall, or the like, and then travels toward base station BS1.

[0165] In this regard, by setting the length of one side of the reflecting conductor 132 to λcg / 2±λcg / 6, in addition to the effect of further widening the bandwidth, the spiral antenna 110 can be selectively oriented in the direction of radiation for each frequency band. To achieve the effect of selectively oriented in the direction of radiation for each frequency band without achieving the effect of further widening the bandwidth, the antenna device 100A may be configured such that the transmission cable 120 does not transmit or receive radio waves in the second frequency band. In this case, the first radiating portion 111 and the second radiating portion 112 of the spiral antenna 110 may not include the extension portions 111D and 112D. Furthermore, the communication device 150 may be configured to amplify only signals in the first frequency band, or to amplify and frequency convert only signals in the first frequency band.

[0166] <Distance d Between Spiral Antenna 110 and Reflecting Conductor 132> When radio waves in frequency band A radiated in the +Z direction from spiral antenna 110 are reflected in the -Z direction by reflecting conductor 132, they propagate through window 10 toward base station BS1 together with the radio waves radiated in the -Z direction from spiral antenna 110. At this time, it is appropriate to set distance d within the following range so that the radio waves reflected in the -Z direction by reflecting conductor 132 and the radio waves radiated in the -Z direction from spiral antenna 110 do not have opposite phases. This is because if the radio waves reflected in the -Z direction by reflecting conductor 132 and the radio waves radiated in the -Z direction from spiral antenna 110 have opposite phases, the strength of the radio waves radiated in the -Z direction from antenna device 100A will decrease.

[0167] The condition for the radio waves reflected in the -Z direction by the reflecting conductor 132 and the radio waves radiated in the -Z direction from the spiral antenna 110 to be in phase is that the distance d is λc / 4, where λc is the wavelength in free space of the radio waves at the boundary frequency (the lower limit frequency in the front direction). This condition is obtained by taking into consideration the distance 2d from the spiral antenna 110 that the radio waves radiated in the +Z direction and reflected in the -Z direction by the reflecting conductor 132 take to return to the spiral antenna 110, and the fact that the phase of the radio waves is shifted by 180 degrees when reflected by the reflecting conductor 132.

[0168] In practice, the phase of the radio waves reflected in the -Z direction by the reflecting conductor 132 and the phase of the radio waves radiated from the spiral antenna 110 in the -Z direction do not need to be completely in phase; they need only be approximately in phase. Therefore, the distance d need not necessarily be strictly λc / 4; it may be within a range of λc / 6 to λc / 3. For the condition of d = λc / 4, which results in perfect phase inversion, if the distance d is within a range of λc / 6 to λc / 3, sufficient strength of the radio waves radiated from the antenna device 100A in the -Z direction can be ensured. The range of λc / 6 to λc / 3 represents the distance d corresponding to the phase range in which power is approximately 1.5 dB lower than the maximum power of the combined radio waves of the radio waves radiated from the spiral antenna 110 in the -Z direction and the radio waves radiated from the spiral antenna 110 in the +Z direction and reflected in the -Z direction by the reflecting conductor 132. The maximum power of the combined radio waves is the power obtained when the distance d is λc / 4.

[0169] 10B and 10C are diagrams showing an example of radiation directivity obtained from a simulation model of the spiral antenna 110 and the reflector 130. The radiation directivity shown in Fig. 10B and 10C is the radiation directivity of a simulation model in which the reflector 130 is placed on the +Z direction side of the spiral antenna 110. The simulation model of the reflector 130 has a conductor equivalent to the reflecting conductor 132.

[0170] 10B and 10C, the radiation directivity in the AZ (Azimuth) direction is shown in gain [dBi]. The AZ direction is a direction within the XZ plane in FIGS. 5A and 5B, with 0 degrees corresponding to the −Z direction and 180 degrees corresponding to the +Z direction.

[0171] 10B shows the radiation directivity when the length of the substrate 110A in the X direction is set to 70 mm, the length in the Y direction is set to 55 mm, and the size of the reflective conductor 132 is set to 20 mm, and radio waves of 0.7 GHz, 1.7 GHz, 2.5 GHz, 3.7 GHz, and 4.5 GHz are radiated from the spiral antenna 110 in an electromagnetic field simulation. Also, FIG. 10C shows the radiation directivity when the size of the reflective conductor 132 is changed to 30 mm among the simulation conditions of FIG. 10B.

[0172] 10B and 10C, the radiated wave of 0.7 GHz was hardly observed. This is thought to be because the lengths of the substrate 110A of the spiral antenna 110 in the X and Y directions are 70 mm and 55 mm, respectively, which is a size that radiates radio waves of approximately 1.4 GHz or higher.

[0173] 10B, it was confirmed that for 1.7 GHz, 2.5 GHz, and 3.7 GHz, substantially uniform radiation was obtained at 0 degrees (front) and 180 degrees (rear). Also, for 4.5 GHz, it was confirmed that radiation was strong in the 0 degree (front) direction and weak in the 180 degree (rear) direction.

[0174] In Figure 10C, at 3.7 GHz and 4.5 GHz, it was confirmed that the radiation in the 0 degree (front) direction was strong and the radiation in the 180 degree (rear) direction was weak, similar to Figure 10B. Furthermore, at 3.7 GHz, it was confirmed that the radiation in the 0 degree (front) direction tended to be stronger and the radiation in the 180 degree (rear) direction tended to be weaker compared to Figure 10B. At 4.5 GHz, it was confirmed that the radiation in the 0 degree (front) direction tended to be even stronger and the radiation in the 180 degree (rear) direction tended to be even weaker compared to Figure 10B.

[0175] As such, from the radiation directivity in Figures 10B and 10C, it was confirmed that by changing the size of the reflective conductor 132, it is possible to adjust the balance of radiation in the 0 degree (front) direction and the 180 degree (rear) direction.

[0176] It was confirmed that the 3.7 GHz and 4.5 GHz radio waves included in frequency band A are reflected in the -Z direction by the reflective conductor 132, resulting in stronger radiation in the 0 degree (front) direction. It was confirmed that the 1.7 GHz and 2.5 GHz radio waves included in frequency band B are hardly reflected by the reflective conductor 132, resulting in approximately uniform radiation at 0 degree (front) and 180 degrees (rear).

[0177] As can be seen from the results shown in Figures 10A to 10C, by adjusting the size of the reflective conductor 132 and setting the lower limit frequency in the front direction to the desired boundary frequency, radio waves in frequency band A can be emitted toward base station BS1 through the window glass 11, and radio waves in frequency band B that are not reflected by the reflective conductor 132 can be transmitted through the window glass 11 or wall 1W and reach base station BS1.

[0178] <Summary of Radio Wave Radiation from Antenna Device 100A> FIG. 11 is a diagram schematically illustrating an example of a state in which the antenna device 100A radiates radio waves.

[0179] With respect to radiation in the front direction, antenna device 100A obtains radio waves of frequency band A and radio waves of frequency band B. Radio waves of frequency band A are radio waves radiated in the −Z direction from spiral antenna 110 and radio waves radiated in the +Z direction from spiral antenna 110 and reflected in the −Z direction by reflecting conductor 132. Radio waves of frequency band B are radio waves radiated in the −Z direction from spiral antenna 110.

[0180] Furthermore, radio waves in frequency band B are obtained for radiation toward the rear. Radio waves in frequency band B are radiated in the +Z direction from spiral antenna 110 and are not reflected by reflecting conductor 132 and are radiated in the +Z direction. If frequency band B includes a band close to 3 GHz, the transmittance of wall 1W will be low, but this is not a particular problem because no cellular system band exists between 2.7 GHz and 3.2 GHz. If adjusting the length of spiral antenna 110 or the size of reflecting conductor 132 results in an unnecessary band with high gain in frequency band B other than the desired band (e.g., 1.5 GHz), the unnecessary band may be set to 2.7 GHz to 3.2 GHz, where no cellular system band exists.

[0181] Furthermore, the transmission cable 120 can emit radio waves in the second frequency band. Because the radio waves in the second frequency band emitted by the transmission cable 120 have low directivity, the radiation characteristics are not significantly affected regardless of the direction in which the transmission cable 120 extends. In addition to the first frequency band in which the spiral antenna 110 can emit radio waves, the transmission cable 120 can emit radio waves in the second frequency band, thereby enabling the antenna device 100A to have a wider bandwidth.

[0182] <Effects> The antenna device 100A includes a spiral antenna 110 that is disposed opposite the window glass 11 and transmits and receives radio waves in a first frequency band, and a transmission cable 120 (transmitter) that is connected to the spiral antenna 110 and transmits signals in the first frequency band, as well as transmitting and receiving radio waves in a second frequency band that is lower than the first frequency band. Therefore, in addition to the first frequency band in which the spiral antenna 110 transmits and receives radio waves in the first frequency band, the transmission cable 120 transmits and receives radio waves in the second frequency band, thereby expanding the band in which communication is possible.

[0183] Therefore, it is possible to provide the antenna device 100A with an even wider bandwidth.

[0184] Furthermore, the transmission cable 120 may be a coaxial cable. If a coaxial cable is used as the transmission cable 120, signals can be transmitted with reduced loss even when the transmission cable 120 is long due to routing or other reasons.

[0185] The length of the coaxial cable may be 200 mm or more. Since the transmission cable 120 made of a coaxial cable transmits signals in a second frequency band that is lower than the first frequency band, a certain length is required in order to function as an antenna that radiates radio waves. If the length of the coaxial cable is 200 mm or more, it can radiate radio waves in the second frequency band of approximately 600 MHz to 1 GHz.

[0186] The spiral antenna 110 may also include a substrate 110A (base) having a surface 110A1 (first surface) and a surface 110A2 (second surface) opposite the surface 110A1, a first radiating portion 111 provided on the surface 110A1 and extending in a spiral shape in a planar view from a feed point 111A located toward the center in a planar view, a feed line 113 provided on the surface 110A1 and extending in a spiral shape in a planar view from a connection portion 113A connected to the feed point 111A to the first radiating portion 111, and a spiral-shaped second radiating portion 112 provided on the surface 110A2 and overlapping with the feed line 113 in a planar view. The spiral antenna 110 configured as described above can reliably transmit and receive radio waves in the first frequency band, and by using the spiral antenna 110 with a transmission cable 120, an antenna device 100A with an even wider bandwidth can be provided.

[0187] Furthermore, the first radiating portion 111 and the second radiating portion 112 may include logarithmic spiral portions (111A to 111C) whose outer edges in a plan view have a shape based on a logarithmic spiral. By including such logarithmic spiral portions (111A to 111C), radio waves in the first frequency band can be radiated over a wide band.

[0188] Furthermore, the end of first radiating portion 111 opposite feed point 111A is open end 111B, and first radiating portion 111 may have extension portion 111D provided between logarithmic spiral portion (111A to 111C) and open end 111B. By changing the current distribution in spiral antenna 110 with extension portion 111D, the currents in the core wire and shield wire of transmission cable 120 are no longer in opposite phase, enabling more reliable radiation from transmission cable 120 and achieving an even wider bandwidth.

[0189] Furthermore, the end of the first radiating portion 111 opposite the feed point 111A is an open end 111B, and when the electrical length of the wavelength of radio waves in the second frequency band is λe, the length between the feed point 111A and the open end 111B may be λe / 6 to λe / 3, or 2λe / 3 to 5λe / 6. This makes it possible to achieve both a further broadband due to the generation of a common mode in the transmission cable 120 and a miniaturized spiral antenna 110.

[0190] The spiral antenna 110 may further include a reflective conductor 132 (reflective portion) that is rectangular in plan view and is provided on the opposite side of the window glass 11 from the spiral antenna 110. The first frequency band has a high frequency band (frequency band A) and a low frequency band (frequency band B) that is lower than the high frequency band. If the wavelength at the boundary frequency between the high frequency band and the low frequency band is λc and the electrical length of the reflective conductor 132 (reflective portion) at wavelength λc is λcg, the length of one side of the reflective conductor 132 may be λcg / 2±λcg / 6, and the distance between the spiral antenna 110 and the reflective conductor 132 may be λcg / 6 to λc / 3. The size of the reflective conductor 132 can be adjusted to set the front-facing lower limit frequency to the boundary frequency (3 GHz) between frequency bands A and B. This increases the radiation intensity of radio waves in frequency band A in the front direction, and allows radio waves in frequency band B in the rear direction to pass through wall 1W and propagate outdoors without being reflected by reflective conductor 132, allowing all radio waves in frequency bands A and B to reach base station BS1.

[0191] The first frequency band may include a portion of the 3 GHz to 6 GHz frequency band, and the second frequency band may include a portion of the 600 MHz to 1 GHz frequency band. By using the first frequency band that is a portion of the 3 GHz to 6 GHz frequency band and the second frequency band that is a portion of the 600 MHz to 1 GHz frequency band, it is possible to provide the antenna device 100A with an even wider bandwidth.

[0192] The first frequency band may further include a part of the frequency band from 1.5 GHz to 3 GHz. By including such a frequency band, it is possible to provide the antenna device 100A with an even wider bandwidth.

[0193] The antenna device 100A includes a spiral antenna 110 that is disposed opposite the window glass 11 and that transmits and receives radio waves in a first frequency band, a transmission cable 120 (transmission section) that is connected to the spiral antenna 110 and that transmits signals in the first frequency band, and a reflecting conductor 132 that is rectangular in plan view and that is disposed on the opposite side of the spiral antenna 110 from the window glass 11, wherein the first frequency band has a high frequency band (frequency band A) and a low frequency band (frequency band B) that is lower than the high frequency band, and where the wavelength at the boundary frequency between the high frequency band and the low frequency band is λc and the electrical length at the reflecting conductor 132 (reflecting section) of wavelength λc is λcg, the length of one side of the reflecting conductor 132 is λcg / 2±λcg / 6, and the distance between the spiral antenna 110 and the reflecting conductor 132 is λc / 6 to λc / 3. By adjusting the size of the reflective conductor 132 and setting the front lower limit frequency to the boundary frequency (3 GHz) between frequency bands A and B, it is possible to increase the radiation intensity of radio waves of frequency band A in the front direction. Furthermore, in the rear direction, radio waves of frequency band B can be transmitted through the wall 1W and propagated outdoors without being reflected by the reflective conductor 132, allowing all radio waves of frequency bands A and B to reach base station BS1.

[0194] Therefore, it is possible to provide the antenna device 100A in which the spiral antenna 110 has selectivity for the radiation direction of the radio waves radiated for each frequency band.

[0195] Furthermore, the first frequency band may include a part of the frequency band from 1.5 GHz to 5 GHz, so that the antenna device 100A can be provided in which one of the selectable frequency bands is a part of the frequency band from 1.5 GHz to 5 GHz.

[0196] The boundary frequency may be a frequency included in the frequency band of 2.6 GHz to 3.3 GHz, and the antenna device 100A can be provided in which the spiral antenna 110 has selectivity for the radiation direction of the radio waves for each frequency band, using the boundary frequency included in the frequency band of 2.6 GHz to 3.3 GHz as the boundary.

[0197] Furthermore, the antenna may include a plurality of spiral antennas 110. This enables communication using a plurality of channels, such as MIMO communication.

[0198] The spiral antenna 110 may further include a matching layer 140 provided between the window glass 11 and the spiral antenna 110. When the spiral antenna 110 transmits and receives radio waves, loss can be reduced by adjusting the electrical length of the radio waves passing through the window glass 11 to match the impedance.

[0199] Furthermore, the spiral antenna 110 may be transparent, which makes it possible to realize the antenna device 100A that is inconspicuous even when placed over the window glass 11 and does not impair visibility.

[0200] The repeater 100 includes the above-described antenna device 100A and a communication device 150 that is connected to the spiral antenna 110 via a transmission cable 120 and performs wireless communication in a first frequency band via the spiral antenna 110 and in a second frequency band via the transmission cable 120. Therefore, in addition to the first frequency band in which the spiral antenna 110 transmits and receives radio waves, the transmission cable 120 transmits and receives radio waves in the second frequency band, thereby expanding the band in which communication is possible.

[0201] Therefore, it is possible to provide a repeater 100 with an even wider bandwidth.

[0202] The repeater 100 includes the antenna device 100A in which the spiral antenna 110 has selectivity for the radiation direction of radio waves for each frequency band. The repeater 100 includes the above-mentioned antenna device 100A and a communication device 150 that is connected to the spiral antenna 110 via a transmission cable 120 and performs wireless communication in a first frequency band via the spiral antenna 110. Therefore, in addition to the first frequency band in which the spiral antenna 110 transmits and receives radio waves, the transmission cable 120 transmits and receives radio waves in a second frequency band, thereby expanding the band in which communication is possible.

[0203] Therefore, it is possible to provide a repeater 100 in which the spiral antenna 110 has selectivity for the direction of radiation of radio waves for each frequency band.

[0204] The above describes exemplary antenna devices and repeaters of the present disclosure, but the present disclosure is not limited to the specifically disclosed embodiments, and various modifications and variations are possible without departing from the scope of the claims.

[0205] This international application claims priority based on Japanese Patent Application No. 2023-090316, filed on May 31, 2023, the entire contents of which are incorporated herein by reference.

[0206] 100A Antenna device 100 Repeater 110 Spiral antenna 110A Substrate (an example of a base) 110A1 Surface (an example of a first surface) 110A2 Surface (an example of a second surface) 111 First radiating section 111A Feeding point 111B, 111B1 Open end 111C Connection section 111D Extension section 112 Second radiating section 112A Open end 112B, 112B1 End section 112C Connection section 112D Extension section 113 Feeder line 113A Connection section 113B End section 120 Transmission cable (an example of a transmission section) 125 Coaxial connector 130 Reflector 131 Substrate 132 Reflecting conductor (an example of a reflecting section) 140 Matching layer 150 Communication device 150A Array antenna 151 Wireless module 151A Control unit 151B Relay unit

Claims

1. a spiral antenna disposed opposite the window glass and configured to transmit and receive radio waves in the first frequency band; a transmission unit connected to the spiral antenna, for transmitting signals in the first frequency band and for transmitting and receiving radio waves in a second frequency band lower than the first frequency band; An antenna device comprising:

2. The antenna device according to claim 1 , wherein the transmission section is a coaxial cable.

3. 3. The antenna device according to claim 2, wherein the length of the coaxial cable is 200 mm or more.

4. The spiral antenna comprises: a base having a first surface and a second surface opposite the first surface; a first radiating portion provided on the first surface and extending in a spiral shape in plan view from a feeding point located on a central side in plan view; a feeder line provided on the first surface and extending in a spiral shape from a connection portion connected to the feed point to the first radiation portion in a plan view; a spiral-shaped second radiation portion provided on the second surface and overlapping with the power supply line in a plan view; 4. The antenna device according to claim 1, further comprising:

5. The antenna device according to claim 4 , wherein the first radiating portion and the second radiating portion each include a logarithmic spiral portion whose outer edge in a plan view has a shape based on a logarithmic spiral.

6. an end of the first radiating portion opposite the feed point is an open end, The antenna device according to claim 5 , wherein the first radiating portion has an extension portion provided between the logarithmic spiral portion and the open end.

7. an end of the first radiating portion opposite the feed point is an open end, 5. The antenna device according to claim 4, wherein, when the electrical length of the wavelength of the radio wave in the second frequency band is λe, the length between the feed point and the open end is λe / 6 to λe / 3, or 2λe / 3 to 5λe / 6.

8. The spiral antenna further includes a reflector that is rectangular in plan view and is provided on the opposite side of the window glass from the spiral antenna, the first frequency band includes a high frequency band and a low frequency band that is lower than the high frequency band, 4. The antenna device according to claim 1, wherein, when a wavelength at a boundary frequency between the high frequency band and the low frequency band is λc and an electrical length of the wavelength λc at the reflecting portion is λcg, a length of one side of the reflecting portion is λcg / 2±λcg / 6, and a distance between the spiral antenna and the reflecting portion is λc / 6 to λc / 3.

9. the first frequency band includes a part of a frequency band from 3 GHz to 6 GHz, The antenna device according to claim 1 , wherein the second frequency band includes a part of a frequency band from 600 MHz to 1 GHz.

10. The antenna device according to claim 9 , wherein the first frequency band further includes a part of a frequency band from 1.5 GHz to 3 GHz.

11. a spiral antenna disposed opposite the window glass and configured to transmit and receive radio waves in the first frequency band; a transmission unit connected to the spiral antenna and configured to transmit a signal in the first frequency band; a reflecting portion having a rectangular shape in a plan view, the reflecting portion being provided on the opposite side of the spiral antenna from the window glass; Including, the first frequency band includes a high frequency band and a low frequency band that is lower than the high frequency band, an antenna device in which, when a wavelength at a boundary frequency between the high frequency band and the low frequency band is λc and an electrical length of the wavelength λc at the reflecting portion is λcg, a length of one side of the reflecting portion is λcg / 2±λcg / 6, and a distance between the spiral antenna and the reflecting portion is λc / 6 to λc / 3.

12. The antenna device according to claim 11 , wherein the first frequency band includes a portion of a frequency band from 1.5 GHz to 5 GHz.

13. 13. The antenna device according to claim 11, wherein the boundary frequency is a frequency included in a frequency band of 2.6 GHz to 3.3 GHz.

14. The antenna device according to claim 1 or 11, comprising a plurality of the spiral antennas.

15. 12. The antenna device according to claim 1 or 11, further comprising a matching layer provided between the window glass and the spiral antenna.

16. 12. The antenna device according to claim 1 or 11, wherein the spiral antenna is transparent.

17. An antenna device according to any one of claims 1 to 3; a communication device connected to the spiral antenna via the transmission unit, performing wireless communication in the first frequency band via the spiral antenna, and performing wireless communication in the second frequency band via the transmission unit; Including, repeater.

18. an antenna device according to claim 11 or 12; a communication device connected to the spiral antenna via the transmission unit and performing wireless communication in the first frequency band via the spiral antenna; Including, repeater.