Antenna device and communication system

Abstract

To provide an antenna device and a communication system that can be used for wireless communication that supports high speed and large capacity communication.SOLUTION: An antenna device 20 includes a photodiode 21 as a first photoelectric conversion element, and a radiator 24. The photodiode 21 acquires signal light for transmitting information propagated through a hole-core fiber 12, converts it into an electric signal, and outputs the converted electric signal. The radiator 24 radiates a radio wave modulated with the electric signal output from the photodiode 21. The electric signal output from the photodiode 21 has transmission output energy for wirelessly transmitting from the radiator 24 to an adjacent device.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an antenna device and a communication system.

Background Art

[0002] With the increase in the speed and capacity of mobile communication, the frequency of wireless communication systems using optical fiber transmission has been rapidly increasing. As a result, in the antenna device of a radio base station in a wireless communication system, an amplifier for increasing the output power of the radiated radio signal has become indispensable.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, in recent years, the performance improvement of semiconductor technology is approaching its limit, and it has become difficult to increase the frequency and output power of amplifiers. Therefore, it is predicted that it will be difficult to construct a wireless communication system that can cope with further increases in the speed and capacity of future mobile communication.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide an antenna device and a communication system capable of coping with high-speed and large-capacity communication.

Means for Solving the Problems

[0006] The antenna device of the present invention for solving the above problems includes a first optoelectronic conversion element that acquires signal light for transmitting information propagated through a hollow-core fiber and converts it into an electrical signal, and outputs the converted electrical signal, and a radiator that radiates radio waves modulated by the electrical signal output from the first optoelectronic conversion element. The electrical signal output by the first optoelectronic conversion element has transmission output energy for wirelessly transmitting to an adjacent device from the radiator.

[0007] The communication system of the present invention further includes a hollow-core fiber that propagates signal light for transmitting information, and an antenna device installed in a radio base station of a mobile communication system and connected to the hollow-core fiber. The antenna device includes a first optoelectronic conversion element that acquires signal light for transmitting information propagated through a hollow-core fiber and converts it into an electrical signal, and outputs the converted electrical signal, and a radiator that radiates radio waves modulated by the electrical signal output from the first optoelectronic conversion element. The electrical signal output by the first optoelectronic conversion element has transmission output energy for wirelessly transmitting to an adjacent device from the radiator.

Advantages of the Invention

[0008] The antenna device and communication system of the present invention can be used for wireless communication corresponding to high speed and large capacity.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2A

Figure 2B

Figure 3

Best Mode for Carrying Out the Invention

[0010] Hereinafter, as an embodiment of the present invention, a wireless communication system using a holey-core fiber will be described in detail. FIG. 1 is an explanatory diagram showing the configuration of a wireless communication system 1 according to this embodiment. The wireless communication system 1 includes a transmission system 10 and an antenna device 20.

[0011] The transmission system 10 includes an optical multiplexer 11, a holey-core fiber 12, and an optical demultiplexer 13.

[0012] The optical multiplexer 11 multiplexes signal light for transmitting information and power supply light for transmitting power, and makes the multiplexed light incident on the holey-core fiber 12.

[0013] The holey-core fiber 12 propagates the incident signal light and power supply light. Since the holey-core fiber 12 has holes inside and can confine and propagate light in the hole cores, it can not only transmit high-power optical energy compared with conventional glass-core fibers, but also realize stable ultra-high-capacity transmission without distortion even for high-power optical signals due to extremely low non-linearity. It is a transmission medium.

[0014] FIG. 2A is a cross-sectional view of a photonic bandgap type holey-core fiber 12A, which is an example of the holey-core fiber 12 used in the wireless communication system 1. The photonic bandgap type holey-core fiber 12A has one center core 121, six side cores 122a, 122b, 122c, 122d, 122e, and 122f, and a cladding 123 disposed around these cores so as to surround them. The photonic bandgap type holey-core fiber 12A has the advantages of being resistant to bending and being cable-able, but has a slightly higher transmission loss and periodic loss characteristics.

[0015] FIG. 2B is a cross-sectional view of a non-resonant type holey-core fiber 12B, which is another example of the holey-core fiber 12 used in the wireless communication system 1. The non-resonant type holey-core fiber 12B has a plurality of cores 124a, 124b, 124c, 124d, 124f, 124g, and 124h arranged in a circular shape, and a cladding 125 arranged peripherally so as to surround these cores. The non-resonant type holey-core fiber 12B has the advantages of being capable of corresponding to a wide range of wavelength bands and reducing transmission loss, while having the property of being vulnerable to bending.

[0016] The optical demultiplexer 13 demultiplexes the signal light and the power supply light propagated through the holey-core fiber 12.

[0017] The antenna device 20 includes a photodiode 21 as a first photoelectric conversion element, a photoelectric conversion element 22 as a second photoelectric conversion element, a DC-DC converter 23, and a radiator 24.

[0018] The photodiode 21 acquires the signal light propagated through the holey-core fiber 12 and converts the acquired signal light into an electrical signal having transmission output energy for wirelessly transmitting to a device such as a mobile terminal within an adjacent predetermined range.

[0019] The photoelectric conversion element 22 acquires the power supply light propagated through the holey-core fiber 12 and converts it into electricity. The DC-DC converter 23 converts the voltage of the electricity converted by the photoelectric conversion element 22 into a voltage suitable for driving the photodiode 21.

[0020] The radiator 24 radiates radio waves modulated by the electrical signal converted by the photodiode 21 into space.

[0021] A case where such a wireless communication system 1 is used in a mobile communication system and the antenna device 20 is installed in a radio base station of the mobile communication system will be described.

[0022] In the transmission system 10, an optical multiplexer 11 multiplexes the signal light and the power supply light and makes them incident on the holey-core fiber 12, and the holey-core fiber 12 propagates this signal light and power supply light. As described above, the holey-core fiber 12 is a transmission medium with extremely low non-linearity compared to a conventional glass-core fiber. As a result, the transmission system 10 enables optical signal transmission with a high output power that was impossible in a transmission system using a conventional glass-core fiber. For example, the transmission system 10 can simultaneously transmit signal light with an output power exceeding 20 dBm and power supply light exceeding 30 dBm.

[0023] An optical demultiplexer 13 is installed in a radio base station and demultiplexes the signal light and the power supply light propagated by the holey-core fiber 12.

[0024] In the antenna device 20, a photoelectric conversion element 22 acquires the power supply light propagated by the holey-core fiber 12 and converts it into electricity. Then, a DC-DC converter 23 converts the voltage of the electricity converted by the photoelectric conversion element 22 into a voltage suitable for driving the photodiode 21.

[0025] The photodiode 21 is driven by the energy of the electricity converted by the DC-DC converter 23, acquires the signal light propagated by the holey-core fiber 12, and converts the acquired signal light into an electrical signal having a high RF (Radio Frequency) output energy for wirelessly transmitting it to a device within a predetermined range, for example, within a range of several kilometers in radius.

[0026] A radiator 24 radiates radio waves modulated by the electrical signal converted by the photodiode 21 into space. Since the radiated radio waves have a high RF output energy, an electrical signal can be wirelessly transmitted from the antenna device 20 to a device such as a mobile terminal within a predetermined adjacent range.

[0027] Since the antenna device 20 of the present embodiment operates as described above, an amplifier for amplifying the electrical signal converted from the transmitted signal light becomes unnecessary.

[0028] In an antenna device used in a mobile communication system that employed a conventional glass core fiber, since there is a limit to the transmission power of the glass core fiber, the output power of the signal light obtained from the glass core fiber is less than 20 dBm. In this case, the antenna device converts the acquired signal light into an electrical signal using a photodiode, and amplifies the converted electrical signal with an amplifier to output an electrical signal having a high RF output energy required for radio wave radiation.

[0029] On the other hand, in the future, the spread of 5G / 6G mobile communication systems that enable high-capacity communication is predicted. To construct such a mobile communication system for high-capacity communication using a glass core fiber, it is necessary to increase the frequency and capacity of the amplifier of the antenna device in the radio base station. However, in recent years, since the performance improvement of semiconductor technology is approaching its limit, it is expected to become difficult to configure an amplifier corresponding to such communication technology.

[0030] In addition, since power is required to drive the photodiode and the amplifier, conventionally, a power supply circuit has been installed in the antenna device, and equipment for supplying power from the power line near the radio base station to this power supply circuit is required. For this reason, the configuration of the antenna device becomes large and the installation location is restricted, and when laying the antenna device, in addition to communication facility work, electrical facility work needs to be carried out, which is time-consuming and costly. Also, there is a problem that if a power outage occurs due to a disaster such as a major earthquake in the laying area, the antenna device goes silent and the mobile communication service cannot be provided.

[0031] On the other hand, in the wireless communication system 1 according to the present embodiment, a signal light having a high output power is transmitted to the antenna device 20 using the holey fiber 12. In the antenna device 20, a high RF output photodiode 21 is used to convert the signal light having a high output power transmitted through the holey fiber 12 into an electrical signal having a high RF output energy. As a result, the antenna device 20 can radiate the electrical signal converted by the photodiode 21 as radio waves into space without using an amplifier and wirelessly transmit the electrical signal to a device within a predetermined range.

[0032] In the antenna device 20 configured without using an amplifier in this way, since the frequency characteristics of the photoelectric conversion are determined only by the photodiode 21, the output power of the output electrical signal can be improved without being restricted by the performance limit of semiconductor technology.

[0033] In the wireless communication system 1, by using the holey fiber 12 capable of transmitting a large-capacity optical signal, it becomes possible to transmit the signal light and the power supply light to the antenna device 20 at the same time. In the antenna device 20, the photodiode 21 can be driven only by the energy of the power supply light transmitted from the holey fiber 12. As a result, the power transmission equipment from the external power facility to the antenna device 20 and the power supply circuit in the antenna device 20 become unnecessary, and the antenna device 20 can be miniaturized and easily installed. That is, by connecting only one holey fiber 12 to the antenna device 20, it becomes possible to transmit the signal light and supply power to the antenna device 20. In addition, since the antenna device 20 installed in this way is driven by the energy of the power supply light transmitted from the holey fiber 12, it is not affected even if a power outage occurs within the laying area, and a disaster-resistant antenna device 20 can be configured, and its usefulness for future mobile communication systems is extremely high.

[0034] FIG. 3 is a graph showing the output power performance of an existing amplifier and a high RF output photodiode.

[0035] The ○ with a dotted line in the graph is an example of the top performance data of an amplifier using CMOS (Complementary Metal Oxide Semiconductor), and the dotted line L1 is its regression line, that is, it shows the frequency characteristics of the amplifier using CMOS. Also, the ● in the graph is an example of the top performance data of an amplifier using GaAs (gallium arsenide), and the thick line L2 is its regression line, that is, it shows the frequency characteristics of the amplifier using GaAs. Further, the ○ in the graph is an example of the top performance data of an amplifier using GaN (gallium nitride), and the thin line L3 is its regression line, that is, it shows the frequency characteristics of the amplifier using GaN. As shown by the frequency characteristics of each amplifier in the graph, the output power of each amplifier decreases as the frequency increases for the transmission of wireless signals.

[0036] In the current mobile communication system, since wireless signals in the sub-6 band with a frequency band of 6 GHz or less are used, there is a lot of data in this band for each amplifier in the graph of FIG. 3. However, in the near future, the use of wireless signals in the 28 GHz band and even higher frequency bands is assumed.

[0037] Band B in the graph shows the frequency characteristics calculated from the performance of currently commercially available high RF output photodiodes. Among the top performance data of each amplifier described above, there are also those with a level higher than that of Band B, but the proportion is low. It can be seen that the frequency characteristics of the current high RF output photodiodes have high performance comparable to those of each amplifier. In the future, it is considered that the high RF output photodiodes will be improved in performance compared to those currently on the market, and there is also sufficient expectation that high RF output photodiodes having a power exceeding that of the above-described amplifiers will be developed.

[0038] By using a high RF output photodiode having such high frequency characteristics, the antenna device 20 of the present embodiment can be simply configured without using an amplifier and applied to a radio base station of a mobile communication system corresponding to increased capacity.

[0039] In addition, by using this antenna device 20, it is possible to construct a wireless communication system that can cope with high speed and large capacity with a simple configuration without being restricted by the performance limits of semiconductor technology and is robust against disasters.

Explanation of Signs

[0040] 1 Wireless communication system 10 Transmission system 11 Optical multiplexer 12 Hole-core fiber 12A Photonic bandgap type hole-core fiber 12B Non-resonant type hole-core fiber 13 Optical demultiplexer 20 Antenna device 21 Photodiode 22 Photoelectric conversion element 23 DC-DC converter 24 Radiator 121 Center core 122a, 122b, 122c, 122d, 122e Side core 123 Cladding 124a, 124b, 124c, 124d, 124f, 124g Core 125 Cladding

Claims

1. A first photoelectric conversion element that acquires signal light for transmitting information propagated through a hollow-core fiber, converts it into an electrical signal, and outputs the converted electrical signal; A radiator that radiates radio waves modulated by the electrical signal output from the first photoelectric conversion element, and an antenna device, The electrical signal output by the first photoelectric conversion element has transmission output energy for wirelessly transmitting to an adjacent device from the radiator.

2. Further comprising a second photoelectric conversion element that acquires power supply light for transmitting power propagated through the hollow-core fiber and converts it into an electrical signal, The first photoelectric conversion element uses the energy of the electrical signal converted by the second photoelectric conversion element to convert the signal light into an electrical signal. The antenna device according to claim 1.

3. A hollow-core fiber that propagates signal light for transmitting information, and an antenna device installed in a radio base station and connected to the hollow-core fiber, The antenna device is, A first photoelectric conversion element that acquires signal light for transmitting information propagated through a hollow-core fiber, converts it into an electrical signal, and outputs the converted electrical signal; A radiator that radiates radio waves modulated by the electrical signal output from the first photoelectric conversion element, and a communication system, The electrical signal output by the first photoelectric conversion element has transmission output energy for wirelessly transmitting to an adjacent device from the radiator.

4. The hollow-core fiber is a photonic bandgap type hollow-core fiber or a non-resonant type hollow-core fiber. The communication system according to claim 3.

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