JP2018157565A - Leakage coaxial cable and radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leakage coaxial cable usable at a plurality of frequency bands and a radio communication system.SOLUTION: A leakage coaxial cable includes: a central conductor; an insulator covering the central conductor concentrically; and an outer conductor which covers the insulator concentrically and on which slot groups made up of one or more elongate-hole shaped slots are periodically provided in a length direction of the leakage coaxial cable. Slot length Ls, i.e. length in a longitudinal direction of the slots is between first slot length tuned in to a first band and second slot length tuned in to a second band at a higher frequency than the first band.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a leaky coaxial cable and a wireless communication system.

  The leaky coaxial cable is a cable in which a hole called a slot for leaking radio waves is provided in the outer conductor of the coaxial cable, and is called an LCX (LCX: Leaky CoaXial) cable. Through such a slot, the leaky coaxial cable can radiate (send) a signal input to the cable as an electromagnetic wave to the outside of the cable and receive an electromagnetic wave from the outside. That is, the leaky coaxial cable can be used as an elongated transmission / reception antenna having both functions of a transmission line and an antenna (see, for example, Patent Document 1 and Patent Document 2).

  In the Wi-Fi standard, which is one of the standards of a wireless LAN (Local Area Network), the 2.4 GHz band and the 5 GHz band are used. In recent years, a communication service using a transmission / reception antenna using an LCX cable has been provided in, for example, a subway, but an LCX cable that can provide a service in the 2.4 GHz band and the 5 GHz band is desired.

JP 2002-271237 A JP 2009-004948 A

  In the prior art, the slot size and interval are designed in accordance with the intended frequency band. FIG. 17 is a diagram illustrating a structure example of a leaky coaxial cable 900 according to the related art. As shown in FIG. 17, the leaky coaxial cable 900 includes a center conductor 902, an insulator 903, an outer conductor 904, and a sheath 905. The outer conductor 904 includes a plurality of slots 901.

  The center conductor 902 is a copper wire having an outer diameter of 5 mm. The insulator 903 is an insulator having an outer diameter of 12 mm, and is formed so as to cover the central conductor 902 concentrically. The outer conductor 904 is, for example, copper having a thickness of 0.1 mm, and is formed so as to cover the insulator 903 concentrically. The slot 901 has a long hole shape and is provided to open to the outer conductor 904. The sheath 905 is made of polyethylene, for example, and is formed so as to cover the outer conductor 904 concentrically.

  When the leaky coaxial cable 900 shown in FIG. 17 is designed for a frequency band of 2.4 GHz band, the slots 901 are formed in the outer conductor 904 with a pitch P of 85 mm, at equal intervals, and in a zigzag manner. The slot 901 has a length Ls of 26 mm, a width Ws of 2 mm, and an angle θs with respect to the axial direction of 15 °.

Leakage coaxial cable 900 designed for 2.4 GHz band is divided into 2.4 GHz band (2.0, 2.2, 2.4, 2.6 GHz) and 5 GHz band (4.8, 5.0, 5.2). (5.4, 5.6 GHz) The transmission loss and coupling loss measured when used for both will be described.
FIG. 18 is a diagram showing the measurement result of the transmission loss of the leaky coaxial cable 900 designed for the 2.4 GHz band according to the prior art. In FIG. 18, the horizontal axis represents frequency (GHz) and the vertical axis represents transmission loss (dB / m). The measured frequency is 0.1 to 9 GHz. As shown in FIG. 18, the 2.4 GHz band transmission loss of the design value is as low as 0.2 dB / m. On the other hand, the transmission loss in the 5 GHz band, which is not a design value, is very high at 15 dB / m. As described above, the reason why the transmission loss greatly increases in the 5 GHz band is that, as shown in FIG. 18, when the wavelength used is about half the wavelength of the slot 901, strong resonance occurs and the LCX cable acts as an antenna. To do. For this reason, as shown in FIG. 18, a transmission loss peak occurs at 5 GHz, which is approximately twice the design value of 2.4 GHz. The resonance frequency fo of the slot 901 is expressed by the following equation (1).

In Equation (1), C ₀ is the speed of light (about 3 × 10 ⁸ (m / s)), and εr is the dielectric constant of the insulator. When substituting Ls = 26 mm, Ws = 2 mm, and εr = 1.2 of the slot 901 into the equation (1), the resonance frequency fo is about 4.9 GHz, which almost coincides with the measurement result of FIG.

  FIG. 19 is a diagram illustrating a measurement result of the coupling loss of the leaky coaxial cable 900 designed for the 2.4 GHz band according to the related art. In FIG. 19, the horizontal axis represents frequency (GHz) and the vertical axis represents coupling loss (dB). The measured frequencies are 2 GHz band and 5 GHz band. As shown in FIG. 19, the design value of 2.4 GHz band coupling loss is 60 ± 10 dB, which is a standard value for an LCX cable. On the other hand, the coupling loss in the 5 GHz band, which is not a design value, is very low at about 40 dB. This is because, in the leaky coaxial cable 900 designed for the 2.4 GHz band, as shown in FIG. 18, the slot 901 resonates in the 5 GHz band and operates as an antenna to generate strong radiation. In FIG. 19, a indicates a range of 60 ± 5 dB, and b indicates a range of 60 ± 10 dB.

  As shown in the measurement results of FIGS. 18 and 19, even if an LCX cable designed for the 2.4 GHz band is to be used for 5 GHz, the transmission loss increases in the 5 GHz band, and the coupling loss decreases. The LCX cable could not be used with a long length.

  When the leaky coaxial cable 900 shown in FIG. 17 is designed for a frequency band of 5 GHz, the slots 901 are formed in the outer conductor 904 with a pitch P of 43 mm and at equal intervals and zigzag. The slot 901 has a length Ls of 13 mm, a width Ws of 2 mm, and an angle θs with respect to the axial direction of 25 °.

The measurement results of transmission loss and coupling loss when the leaky coaxial cable 900 designed for the 5 GHz band is used in both the 2.4 GHz band and the 5 GHz band will be described.
FIG. 20 is a diagram illustrating a measurement result of transmission loss of a leaky coaxial cable 900 designed for the 5 GHz band according to the related art. In FIG. 20, the horizontal axis represents frequency (GHz) and the vertical axis represents transmission loss (dB / m). The measured frequency is 0.1 to 9 GHz. As shown in FIG. 20, the 2.4 GHz band transmission loss, which is not a design value, is as low as 0.1 dB / m. Further, the transmission loss in the designed 5 GHz band is 0.3 dB / m. As described above, the reason why the transmission loss in the 5 GHz band is improved with respect to FIG. 18 is that the frequency causing resonance is shifted to about 9 GHz, which is higher than 5 GHz, as shown in FIG. When the resonance frequency is calculated using Equation (1), it is about 9.1 GHz.

  FIG. 21 is a diagram illustrating a measurement result of the coupling loss of the leaky coaxial cable 900 designed for the 5 GHz band according to the related art. In FIG. 21, the horizontal axis represents frequency (GHz) and the vertical axis represents coupling loss (dB). The measured frequencies are 2 GHz band and 5 GHz band. As shown in FIG. 21, the 2.4 GHz band coupling loss, which is not the design value, is too high at 70 dB. On the other hand, the coupling loss in the 5 GHz band, which is a design value, is a standard value of about 60 ± 10 dB. This is because the leaky coaxial cable 900 designed for the 5 GHz band has a weaker radiation because the length Ls of the slot 901 is half that of Ls = 26 mm when designed for the 2.4 GHz band. It is.

  As shown in the measurement results of FIG. 20 and FIG. 21, even if an LCX cable designed for the 5 GHz band is used for 2.4 GHz, the coupling loss in the 2.4 GHz band becomes high and cannot be used. .

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a leaky coaxial cable that can be used in a plurality of frequency bands, and a wireless communication system.

  In order to achieve the above object, a leaky coaxial cable (10) according to an aspect of the present invention includes a center conductor (102), an insulator concentrically covering the center conductor (high foam insulator 103), A slot group (101 ′) consisting of two or more slot-shaped slots (101) is periodically provided at a pitch Ps in the length direction of the leaky coaxial cable while covering the insulator concentrically. A slot length Ls, which is a length in the longitudinal direction of the slot, is a first slot length in which a coupling loss has a value within a predetermined range in a first band (for example, 2.4 GHz band). And a second slot length in which the coupling loss is a value within a predetermined range in a second band (for example, 5 GHz band) having a frequency higher than that of the first band.

  In order to achieve the above object, a leaky coaxial cable (100) according to one aspect of the present invention includes a center conductor (102), an insulator concentrically covering the center conductor (highly foamed insulator 103), A slot group (101 ′) comprising a slot (101 ′) having a slot shape (101) that covers the insulator concentrically and has a number Ns (where Ns is an integer of 1 or more) in the length direction of the leaky coaxial cable. Is a slot length Ls which is a length in the longitudinal direction of the slot, and the resonance frequency of the slot is a first band (for example, 2). .4 GHz band) in which the coupling loss is a value within a predetermined range, and the coupling loss is a value within a predetermined range in a second band having a frequency higher than the first band (for example, 5 GHz band). And The between the second resonance frequency due to the slot length, which is the slot length Ls.

  In the leaky coaxial cable according to one aspect of the present invention, the value of the predetermined range of the coupling loss may be 60 ± 5 dB.

  In the leaky coaxial cable according to one aspect of the present invention, the pitch Ps is radiated using at least the first radiation mode in the first band, and is at least the first in the second band. You may make it form so that it may radiate | emit using a radiation mode and a 2nd radiation mode.

In the leaky coaxial cable according to one aspect of the present invention, the slot is inclined at an angle θs (°) in the length direction of the leaky coaxial cable, and the number Ns of the slots (where Ns is an integer of 1 or more). The slot length Ls (mm) is expressed by the following relational expression Ls = (0.01θs−2) Ns−0.1θs + 21
The relationship may be as follows.

In the leaky coaxial cable according to one aspect of the present invention, the slot length Ls may be in a range of ± 10% of the relational expression.
In the leaky coaxial cable according to one aspect of the present invention, the slot length Ls may be in a range of ± 5% of the relational expression.

In the leaky coaxial cable according to one aspect of the present invention, the slot angle θs may be between 5 ° and 90 °.
In the leaky coaxial cable according to one aspect of the present invention, the first band may be a 2.4 GHz band, and the second band may be a 5 GHz band.

  In the leaky coaxial cable according to one aspect of the present invention, λo is a free space wavelength with respect to a use frequency, εr is a dielectric constant of an insulator, and the pitch Ps is λo / (1 + √ (εr) ) May be larger.

  In order to achieve the above object, a wireless communication system (1) according to one aspect of the present invention is configured to transmit radio waves transmitted or received by any one of the leaky coaxial cables in the first frequency band and the second frequency band. A receiving or transmitting antenna, and terminals (41, 42) having the antenna.

  According to the present invention, a leaky coaxial cable that can be used in a plurality of frequency bands and a wireless communication system can be provided.

It is a figure which shows the structural example of the leaky coaxial cable which concerns on this embodiment. It is a figure which shows the measurement system of a transmission loss. It is a figure which shows the measurement system of coupling loss. It is a figure which shows the combination of the slot angle of the various leaky coaxial cables made as an experiment, the number of slots, and slot length. It is a figure which shows the relationship between the slot number Ns and the slot length Ls of the trial leaky coaxial cable. It is a figure which shows the measurement result of the coupling loss of 2.4 GHz band and 5 GHz band with respect to the slot angle θs of 15 ° and the number of slots Ns of 1 or 2. It is a figure which shows the measurement result of the coupling loss of 2.4 GHz band and 5 GHz band with respect to the slot angle (theta) s of 15 degrees and the number of slots Ns of 3 and 4. It is a figure which shows the measurement result of the coupling loss of 2.4 GHz band and 5 GHz band with respect to the slot angle (theta) s of 15 degrees and the number Ns of 5 slots. FIG. 5 is a diagram showing a measurement result of coupling loss by a combination of the slot angle θs, the number of slots Ns, and the slot length Ls shown in FIG. 4. FIG. 5 is a diagram showing a measurement result of coupling loss by a combination of the slot angle θs, the number of slots Ns, and the slot length Ls shown in FIG. 4. It is a figure which shows the result of having calculated slot number Ns and slot length Ls by using slot angle (theta) s as a parameter to the relational expression of Formula (4) which concerns on this embodiment. FIG. 12 is a diagram in which the calculation result shown in FIG. 11 is superimposed on the actual measurement result of the coupling loss in FIG. 10. It is a figure which shows the slot length Ls of the leaky coaxial cable for 2.4 GHz band exclusive use, 5 GHz band exclusive use, and both 2.4 GHz band and 5 GHz band, and a coupling loss on the same conditions. It is a figure which shows the result of having calculated the slot resonant frequency in the optimal slot length Ls which concerns on this embodiment. It is a figure which shows the example of arrangement | positioning of the slot of the leaky coaxial cable which concerns on this embodiment. It is a figure which shows the structural example of the radio | wireless communications system using the leaky coaxial cable which concerns on this embodiment. It is a figure which shows the structural example of the leaky coaxial cable which concerns on a prior art. It is a figure which shows the measurement result of the transmission loss of the leaky coaxial cable designed for 2.4 GHz band concerning a prior art. It is a figure which shows the measurement result of the coupling loss of the leaky coaxial cable designed for 2.4 GHz band concerning a prior art. It is a figure which shows the measurement result of the transmission loss of the leaky coaxial cable designed for 5 GHz bands based on a prior art. It is a figure which shows the measurement result of the coupling loss of the leaky coaxial cable designed for 5 GHz bands based on a prior art. It is a figure which shows the radiation mode chart of the leaky coaxial cable in case the 2nd pitch between the slot groups which concerns on this embodiment is 85 mm. It is a figure which shows the radiation mode chart of the leaky coaxial cable in case the 2nd pitch between slot groups is 60 mm. It is a figure which shows the radiation mode chart of the leaky coaxial cable in case the 2nd pitch between slot groups is 114 mm.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating a structure example of a leaky coaxial cable 10 according to the present embodiment.
As shown in FIG. 1, the leaky coaxial cable 10 includes a center conductor 102, a highly foamed insulator 103 (insulator), an outer conductor 104, and a sheath 105. The outer conductor 104 includes a plurality of slots 101.

  The center conductor 102 is, for example, a copper wire having an outer diameter of 5 mm. The highly foamed insulator 103 is an insulator having an outer diameter of 12 mm, for example, and is formed so as to cover the central conductor 102 concentrically. The outer conductor 104 is, for example, copper having a thickness of 0.1 mm, an outer diameter is 13 mm, and is formed so as to cover the highly foamed insulator 103 concentrically. The slots 101 are formed in the outer conductor 104 at equal intervals with a first pitch Ps ′ (mm).

  Slot 101 (11), slot 101 (12),... Slot 101 (1Ns) are the first slot group 101 '. Slot 101 (21), slot 101 (22),... Slot 101 (2Ns) are the second slot group 101 '. As described above, in the leaky coaxial cable 10 of the present embodiment, a slot group consisting of slots having a long hole shape with a number Ns (where Ns is an integer of 1 or more) in the lengthwise direction of the leaky coaxial cable is periodic. Are provided on the outer conductor 104.

As shown in FIG. 1, the slot 101 has a long hole shape, such as an ellipse or a rounded quadrangle with rounded corners. Further, the slot 101 is provided so as to open to the outer conductor 104. The slot 101 has a length Ls (mm) and a width Ws of 2 mm. Ns slots (where Ns is an integer of 1 or more) are arranged at equal intervals of the first pitch Ps ′ in the axial direction of the central conductor 102. The interval between the slot 101 (11) of the first slot group 101 ′ and the slot 101 (21) of the second slot group 101 ′ is the second pitch Ps (mm). The slot 101 (12) adjacent to the first slot 101 (11) of the first slot group 101 ′ and the slot 101 (22) adjacent to the second slot 101 (21) of the second slot group 101 ′. Is the second pitch Ps. As shown in FIG. 1, the Ns slots included in the first slot group 101 ′ and the Ns slots included in the second slot group 101 ′ are the shape of each slot and the slot arrangement. The pattern is the same. Thus, the interval between the first slot group 101 ′ and the second slot group 101 ′ is the second pitch Ps.
The slots of the first slot group 101 ′ and the second slot group 101 ′ are at an angle (hereinafter also referred to as slot angle) −θs (°) in a direction perpendicular to the longitudinal direction of the leaky coaxial cable 10. Is formed. Between the first slot group 101 ′ and the second slot group 101 ′, slots having an angle + θs (°) in the direction perpendicular to the longitudinal direction of the leaky coaxial cable 10 have the first pitch Ps. Ns pieces are formed at equal intervals. In the longitudinal direction of the second slot group (the position of the sheath 105 in FIG. 1), slots having an angle + θs (°) in the direction perpendicular to the longitudinal direction of the leaky coaxial cable 10 have the first pitch Ps, etc. Ns pieces are formed at intervals.
The sheath 105 is, for example, 15 mm in outer diameter and made of polyethylene, and is formed so as to cover the outer conductor 104 concentrically.

  Note that the approximate value of the second pitch Ps (mm) between the slot groups 101 ′ described above is expressed by the following equation (2).

  In Equation (2), λo is a free space wavelength with respect to the operating frequency, and εr is the relative dielectric constant of the insulator.

Next, a measurement system for transmission loss and coupling loss of the leaky coaxial cable 10 will be described.
FIG. 2 is a diagram illustrating a transmission loss measurement system. As shown in FIG. 2, the transmission loss is measured by connecting a transmission loss measuring device to both ends of the leaky coaxial cable 10.
FIG. 3 is a diagram illustrating a coupling loss measurement system. FIG. 3A is a side view, and FIG. 3B is a plan view. FIG. 3 is also a diagram illustrating a situation in which the lengthwise polarization of the leaky coaxial cable 10 is measured.
The separation distance between the leaky coaxial cable 10 and the antenna 20 is rm. An input signal input from one end of the leaky coaxial cable 10 is Pin. A terminator 11 is connected to the leaky coaxial cable 10. The output from the antenna 20 is Pout. The antenna 20 is a half-wave standard dipole antenna.

  The measurement is performed by moving the antenna 20 in parallel with the position of the upper part rm of the leaky coaxial cable 10. The coupling loss between the polarization Ex in the length direction of the leaky coaxial cable 10 and the polarization Ey in the direction perpendicular to the length direction of the leaky coaxial cable 10 matches the element (element) of the antenna 20 with the polarization direction. To measure. The coupling loss Lc (dB) is expressed as the following equation (3).

Next, in order to examine the leaky coaxial cable 10 that can handle both the 2.4 GHz band and the 5 GHz band, various leaky coaxial cables 10 were prototyped and the coupling loss was measured. The outer diameter of the center conductor 102 is 5 mm, the outer diameter of the highly foamed insulator 103 is 12 mm, the outer diameter of the outer conductor 104 is 13 mm, the outer diameter of the sheath 105 is 15 mm, the slot width Ws is 2 mm, The 2 pitch Ps is 85 mm.
FIG. 4 is a diagram showing combinations of the slot angle θs, the number of slots Ns, and the slot length Ls of various types of prototyped leaky coaxial cables 10. FIG. 5 is a diagram showing the relationship between the number of slots Ns and the slot length Ls of the prototype leaky coaxial cable 10.

  As shown in FIG. 4, when the slot angle θs is 15 ° and the number of slots Ns is 1, three types of leaky coaxial cables 10 having a slot length Ls of 19 mm, 18 mm, and 17 mm were manufactured. In the case where the slot angle θs is 15 ° and the number of slots Ns is two, one type of leaky coaxial cable 10 having a slot length Ls of 16 mm was prototyped. In the case where the slot angle θs is 15 ° and the number of slots Ns is 3, two types of leaky coaxial cables 10 having a slot length Ls of 15 mm and 14 mm were made as prototypes. In the case where the slot angle θs is 15 ° and the number of slots Ns is 4, one type of leaky coaxial cable 10 having a slot length Ls of 12 mm was prototyped. In the case where the slot angle θs is 15 ° and the number of slots Ns is 5, three types of leaky coaxial cables 10 having a slot length Ls of 11 mm, 10 mm, and 9 mm were prototyped.

  In the case where the slot angle θs is 45 ° and the number of slots Ns is 1, three types of leaky coaxial cables 10 having a slot length Ls of 16 mm, 15 mm, and 14 mm were manufactured. In the case where the slot angle θs is 45 ° and the number of slots Ns is two, one type of leaky coaxial cable 10 having a slot length Ls of 13.5 mm was prototyped. In the case where the slot angle θs is 45 ° and the number of slots Ns is 3, three types of leaky coaxial cables 10 having a slot length Ls of 13 mm, 12 mm, and 11 mm were prototyped. In the case where the slot angle θs is 45 ° and the number of slots Ns is 4, one type of leaky coaxial cable 10 having a slot length Ls of 10.5 mm was prototyped. In the case where the slot angle θs is 45 ° and the number of slots Ns is 5, three types of leaky coaxial cables 10 having a slot length Ls of 10 mm, 9 mm, and 8 mm were prototyped.

  In the case where the slot angle θs is 90 ° and the number of slots Ns is 1, three types of leaky coaxial cables 10 having a slot length Ls of 12 mm, 11 mm, and 10 mm were prototyped. When the slot angle θs was 90 ° and the number of slots was two, one type of leaky coaxial cable 10 having a slot length of 10 mm was prototyped. In the case where the slot angle θs is 90 ° and the number of slots Ns is 3, two types of leaky coaxial cables 10 having a slot length Ls of 10 mm and 8 mm were prototyped. In the case where the slot angle θs is 90 ° and the number of slots Ns is 4, one type of leaky coaxial cable 10 having a slot length Ls of 8 mm was prototyped. In the case where the slot angle θs is 90 ° and the number of slots Ns is 5, three types of leaky coaxial cables 10 having a slot length Ls of 8 mm, 7 mm, and 6 mm were prototyped.

  FIG. 6 is a diagram showing the measurement results of the coupling loss in the 2.4 GHz band and the 5 GHz band when the slot angle θs is 15 ° and the number of slots Ns is 1 or 2. FIG. FIG. 7 is a diagram showing the measurement results of the coupling loss in the 2.4 GHz band and the 5 GHz band for the slot angle θs of 15 ° and the number of slots Ns of 3 and 4. FIG. 8 is a diagram illustrating measurement results of coupling loss in the 2.4 GHz band and the 5 GHz band when the slot angle θs is 15 ° and the number of slots Ns is five. 6 to 8, the horizontal axis represents frequency (GHz) and the vertical axis represents coupling loss (dB).

  FIG. 6A shows the measurement result of the coupling loss when the slot angle θs is 15 °, the number of slots Ns is 1, and the slot length Ls is 19 mm. FIG. 6B shows a measurement result of coupling loss when the slot angle θs is 15 °, the number of slots Ns is 1, and the slot length Ls is 18 mm. FIG. 6C shows a measurement result of coupling loss when the slot angle θs is 15 °, the number of slots Ns is 1, and the slot length Ls is 17 mm. FIG. 6D shows the measurement result of the coupling loss when the slot angle θs is 15 °, the number of slots Ns is 2, and the slot length Ls is 16 mm.

  FIG. 7A shows the measurement result of the coupling loss when the slot angle θs is 15 °, the number of slots Ns is 3, and the slot length Ls is 15 mm. FIG. 7B shows the measurement result of the coupling loss when the slot angle θs is 15 °, the number of slots Ns is 3, and the slot length Ls is 14 mm. FIG. 7C shows a measurement result of coupling loss when the slot angle θs is 15 °, the number of slots Ns is 4, and the slot length Ls is 12 mm.

  FIG. 8A shows the measurement result of the coupling loss when the slot angle θs is 15 °, the number of slots Ns is 5, and the slot length Ls is 11 mm. FIG. 8B shows a measurement result of coupling loss when the slot angle θs is 15 °, the number of slots Ns is 5, and the slot length Ls is 10 mm. FIG. 8C shows a measurement result of coupling loss when the slot angle θs is 15 °, the number of slots Ns is 5, and the slot length Ls is 9 mm.

Similarly, the coupling loss was measured at the slot angle θs of 45 ° and 90 ° at the slot number Ns of 1 to 5 and the slot length Ls shown in FIG. Note that the transmission loss due to the combination of the slot angle θs, the number of slots Ns, and the slot length Ls shown in FIG. 4 was 0.5 dB / m or less, respectively.
9 and 10 are diagrams showing the measurement results of the coupling loss by the combination of the slot angle θs, the number of slots Ns, and the slot length Ls shown in FIG. In FIG. 10, the horizontal axis represents the number of slots Ns (number), and the vertical axis represents the number of slots Ls (mm).

9 and 10, ▪ represents the coupling loss in the range where the slot angle θs is 15 ° and the coupling loss is 60 ± 5 dB. □ represents the coupling loss in the range where the slot angle θs is 15 ° and the coupling loss is 60 ± 6 to 10 dB. X represents a coupling loss with a slot angle θs of 15 ° and a coupling loss of 60 ± 11 dB or more.
The symbol ▲ represents the coupling loss in the range where the slot angle θs is 45 ° and the coupling loss is 60 ± 5 dB. Δ represents a coupling loss in a range where the slot angle θs is 45 ° and the coupling loss is 60 ± 6 to 10 dB. * Represents a coupling loss with a slot angle θs of 45 ° and a coupling loss of 60 ± 11 dB or more.
● represents a coupling loss in the range where the slot angle θs is 90 ° and the coupling loss is 60 ± 5 dB. O represents the coupling loss in the range where the slot angle θs is 90 ° and the coupling loss is 60 ± 6 to 10 dB. + Represents a coupling loss with a slot angle θs of 90 ° and a coupling loss of 60 ± 11 dB or more.

  9 and 10, in the coupling loss Lc1 / coupling loss Lc2, the coupling loss Lc1 represents the coupling loss in the 2.4 GHz band, and the coupling loss Lc2 represents the coupling loss in the 5 GHz band.

  A statistical method is used for the measurement results of the coupling loss shown in FIGS. 9 and 10, and the relationship as the optimum condition among the slot angle θs (°), the number of slots Ns (pieces), and the slot length Ls (mm) is obtained. As a result of calculation, it was found that the following expression (4) is obtained. The optimum condition is that the coupling loss is 60 ± 5 dB in both the 2.4 GHz band and the 5 GHz band.

Note that the condition of the expression (4) is that the slot width Ws is 2 mm and the pitch Ps between the slot groups is 85 mm.
FIG. 11 is a diagram illustrating the result of calculating the number of slots Ns and the slot length Ls using the slot angle θs as a parameter in the relational expression (4) according to the present embodiment. In FIG. 11, there are six types of slot angles θs: 15 °, 30 °, 45 °, 60 °, 75 °, and 90 °. Further, there are five types of slots Ns, 1 to 5.

  When the slot angle θs is 15 °, the optimum slot length Ls with one slot number Ns is 17.7 mm, the optimum slot length Ls with two slot numbers Ns is 15.8 mm, and the slot number Ns. The optimum slot length Ls for three slots is 14.0 mm, the optimum slot length Ls for four slots Ns is 12.1 mm, and the optimum slot length Ls for five slots Ns is 10.4 mm. 3 mm.

  When the slot angle θs is 30 °, the optimum slot length Ls with one slot number Ns is 16.3 mm, the optimum slot length Ls with two slot numbers Ns is 14.6 mm, and the slot number Ns. The optimum slot length Ls for three slots is 12.9 mm, the optimum slot length Ls for four slots Ns is 11.2 mm, and the optimum slot length Ls for five slots Ns is 9. 5 mm.

  When the slot angle θs is 45 °, the optimum slot length Ls with one slot number Ns is 15.0 mm, the optimum slot length Ls with two slot numbers Ns is 13.4 mm, and the slot number Ns. The optimum slot length Ls for the three slots is 11.9 mm, the optimum slot length Ls for the four slots Ns is 10.3 mm, and the optimum slot length Ls for the five slots Ns is 8. 8 mm.

  When the slot angle θs is 60 °, the optimum slot length Ls with one slot number Ns is 13.6 mm, the optimum slot length Ls with two slot numbers Ns is 12.2 mm, and the slot number Ns. The optimum slot length Ls for the three slots is 10.8 mm, the optimum slot length Ls for the four slots Ns is 9.4 mm, and the optimum slot length Ls for the five slots Ns is 8. 0 mm.

  When the slot angle θs is 75 °, the optimum slot length Ls with one slot number Ns is 12.3 mm, the optimum slot length Ls with two slot numbers Ns is 11.0 mm, and the slot number Ns. The optimum slot length Ls for the three slots is 9.8 mm, the optimum slot length Ls for the four slots Ns is 8.5 mm, and the optimum slot length Ls for the five slots Ns is 7. 3 mm.

  When the slot angle θs is 90 °, the optimal slot length Ls with one slot number Ns is 10.9 mm, the optimal slot length Ls with two slot numbers Ns is 9.8 mm, and the slot number Ns. The optimum slot length Ls for the three slots is 8.7 mm, the optimum slot length Ls for the four slots Ns is 7.6 mm, and the optimum slot length Ls for the five slots Ns is 6. 5 mm.

  Thus, when the number of slots Ns increases or the slot angle θs increases, the disturbance of the current flowing in the axial direction of the leaky coaxial cable 10 inside the outer conductor 104 of the leaky coaxial cable 10 increases and the coupling loss decreases. (The amount of radiation increases.) For this reason, as the number of slots Ns increases or the slot angle θs increases, the slot length Ls also decreases. The calculation results in FIG. 11 confirm this phenomenon.

12 is a diagram in which the calculation result shown in FIG. 11 is superimposed on the actual measurement result of the coupling loss in FIG. In FIG. 12, the horizontal axis represents the number of slots Ns (number), and the vertical axis represents the slot length Ls (mm). In FIG. 12, the chain line indicates a range of ± 5% of the slot length Ls, and the alternate long and short dash line indicates a range of ± 10% of the slot length Ls.
From FIG. 12, if the slot length Ls ± 5% calculated using equation (4) is used, the coupling loss can be 60 ± 5 dB. Further, if the slot length Ls ± 10% calculated using the equation (4) is used, the coupling loss can be 60 ± 10 dB. In the present embodiment, the value of the predetermined range of the coupling loss is 60 ± 10 dB.

  Accordingly, in order to determine Ls of the slot 101 of the leaky coaxial cable 10, the slot length Ls is calculated by substituting the slot angle θs and the number of slots Ns into the equation (4). Subsequently, if the calculated slot length Ls is ± 10%, the leaky coaxial cable 10 having a coupling loss of 60 ± 10 dB can be determined. Alternatively, if the calculated slot length Ls is ± 5%, the leaky coaxial cable 10 having a coupling loss of 60 ± 5 dB can be determined.

Here, leaky coaxial cables for 2.4 GHz band, 5 GHz band, and both 2.4 GHz band and 5 GHz band under the same conditions will be described. Note that the expressions “dedicated to 2.4 GHz band” and “dedicated to 5 GHz band” do not mean that it can be used only in that frequency band, but mean “when used in that frequency band”.
The conditions are as follows: the outer diameter of the central conductor 102 is 5 mm, the outer diameter of the highly foamed insulator 103 is 12 mm, the outer diameter of the outer conductor 104 is 13 mm, the outer diameter of the sheath 105 is 15 mm, the number of slots Ns is 1, and the slot width Ws. Is 2 mm, the slot angle θs is 15 °, and the second pitch Ps between the slot groups is 85 mm.

As described above, the slot length Ls when the leaky coaxial cable is designed exclusively for the 2.4 GHz band is 26 mm. The coupling loss in this case was about 55 dB in the 2.4 GHz band and about 40 dB in the 5 GHz band.
Further, from FIG. 10, the optimum slot length Ls dedicated to the 2.4 GHz band is 18.5 mm. It can be seen from FIG. 10 that there is an optimum Ls with a coupling loss of 60 dB between Ls of 18 mm with a coupling loss of 62 dB and Ls of 19 mm with a coupling loss of 55 dB. Therefore, the optimum slot length Ls is set to 18.5 mm, which is an intermediate value between Ls 18 mm and Ls 19 mm.

  Further, from FIG. 10, the optimum slot length Ls when a leaky coaxial cable is designed exclusively for the 5 GHz band is more preferably about 17.0 mm at which the coupling loss is about 60 dB in the 5 GHz band. In this case, the coupling loss in the 2.4 GHz band is about 65 dB from FIG.

  On the other hand, as described above, the optimum slot length Ls of the leaky coaxial cable 10 of the present embodiment corresponding to both the 2.4 GHz band and the 5 GHz band is 17.7 mm (≈18 mm) as shown in FIG. there were. The coupling loss in this case was 62 dB in the 2.4 GHz band and 55 dB in the 5 GHz band as shown in FIG.

These results are summarized as shown in FIG. FIG. 13 is a diagram illustrating the slot length Ls and coupling loss of the leaky coaxial cable for 2.4 GHz band, 5 GHz band, and both 2.4 GHz band and 5 GHz band, under the same conditions.
Thus, the slot length Ls of the leaky coaxial cable 10 of the present embodiment has the relationship of the following equation (5). The coupling loss in this case was 62 dB in the 2.4 GHz band and 55 dB in the 5 GHz band.

That is, the slot 101 of the leaky coaxial cable 10 according to the present embodiment has a slot length Ls of 18.5 mm dedicated to the 2.4 GHz band when the slot width Ws, the slot angle θs, and the second pitch Ps between the slot groups are the same. It is shorter and longer than 17.0 mm dedicated to the 5 GHz band.
As shown in FIG. 13, the slot length Ls for both the 2.4 GHz band and the 5 GHz band can be simply calculated using the following equation (6).

  For example, when the value of FIG. 13 is substituted into Expression (6), the slot length Ls for both 2.4 GHz band and 5 GHz band is 17.7 mm (= (18.5 + 17.0) / 2) (2 decimal places) The value in the digit is rounded down).

Next, the slot resonance frequency (hereinafter referred to as the slot resonance frequency) will be described.
FIG. 14 is a diagram illustrating a result of calculating the slot resonance frequency at the optimum slot length Ls according to the present embodiment. The slot resonance frequency can be calculated by substituting the slot width Ws = 2 mm, the optimum slot length Ls, Co, and εr = 1.2 into the above-described equation (1).
As shown in FIG. 14, when the slot number Ns is 1 and the slot angle θs is 15 °, 30 °, 45 °, 60 °, 75 °, and 90 °, the slot resonance frequency is about 6.9 GHz in order. 7.5 GHz, about 8.1 GHz, about 8.8 GHz, about 9.6 GHz, and about 10.6 GHz. The slot resonance frequencies when the slot number Ns is 2 and the slot angle θs is 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° are about 7.7 GHz, about 8.2 GHz, and about 8.9 GHz, about 9.6 GHz, about 10.5 GHz, and about 11.6 GHz. The slot resonance frequencies when the number of slots Ns is 3 and the slot angle θs is 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° are about 8.6 GHz, about 9.2 GHz, and about 9.8 GHz, about 10.7 GHz, about 11.6 GHz, and about 12.8 GHz. The slot resonance frequencies when the number of slots Ns is 4 and the slot angle θs is 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° are about 9.7 GHz, about 10.4 GHz, and about 11.1 GHz, about 12.0 GHz, about 13.0 GHz, and about 14.3 GHz. The slot resonance frequencies when the slot number Ns is 5 and the slot angle θs is 15 °, 30 °, 45 °, 60 °, 75 °, and 90 ° are about 11.1 GHz, about 11.9 GHz, and about 12.7 GHz, about 13.7 GHz, about 14.7 GHz, and about 16.1 GHz.

Here, the slot resonance frequencies are compared under the condition that the number of slots Ns is 1, the second pitch Ps between the slot groups is 85 mm, the slot angle θs is 15 °, and the slot width Ws is 2 mm.
The slot resonance frequency of the leaky coaxial cable dedicated to the 2.4 GHz band is about 4.9 GHz when the slot length Ls is 26 mm, and about 6.7 GHz when the optimum slot length Ls is 18.5 mm.
The slot resonance frequency in the leaky coaxial cable dedicated to the 5 GHz band is about 7.2 GHz since the slot length Ls = 17.0 mm is the optimum slot length as described above.
The optimum slot length Ls of the leaky coaxial cable 10 optimized for both the 2, 4 GHz band and the 5 GHz band is about 17.7 mm as described above. For this reason, the slot resonance frequency in the leaky coaxial cable in both the 2.4 GHz band and the 5 GHz band is about 6.9 GHz.
As described above, the slot resonance frequency of the leaky coaxial cable 10 of the present embodiment has the relationship of the following expression (7).

  That is, the slot resonance frequency of the leaky coaxial cable 10 of the present embodiment is a value between the slot resonance frequency dedicated for 2.4 GHz and the slot resonance frequency dedicated for 5 GHz.

  Here, in order to correspond to both the 2.4 GHz band and the 5 GHz band, a case where the resonance frequency of the slot is set to be dedicated to the 5 GHz band or more will be considered. As shown in FIG. 19 of the prior art, a leaky coaxial cable designed with a slot resonance frequency exclusively for the 2.4 GHz band has a coupling loss of 60 ± 5 dB in the 2.4 GHz band, but the coupling loss is about 40 dB in the 5 GHz band. It is low. As described above, when both the 2.4 GHz band and the 5 GHz band are used, the desired coupling loss cannot be obtained in the higher band. On the other hand, as shown in FIG. 21 of the prior art, in the leaky coaxial cable in which the slot resonance frequency is designed exclusively for the 5 GHz band, even if a coupling loss of 60 ± 5 dB is obtained in the 5 GHz band, the coupling loss is about 70 dB in the 2.4 GHz band. It is expensive. As described above, when both the 2.4 GHz band and the 5 GHz band are used, the intended coupling loss cannot be obtained in the lower band. Therefore, as described above, in this embodiment, in order to correspond to both the 2.4 GHz band and the 5 GHz band, the slot resonance frequency is set to the slot resonance frequency of the leaky coaxial cable dedicated to the 2.4 GHz band and the 5 GHz band. It was made to be between the slot resonance frequency of the dedicated leaky coaxial cable. When this is expanded, in order to correspond to both the first band B1 and the second band B2, the slot resonance frequency is changed to the dedicated slot resonance frequency of the first band B1 and the dedicated band resonance of the second band B2. What is necessary is just to be between slot resonance frequencies. However, as described above, this condition is that the outer diameter of the center conductor 102, the outer diameter of the highly foamed insulator 103, the outer diameter of the outer conductor 104, the outer diameter of the sheath 105, the slot width Ws, the slot angle θs, the slot group The second pitch Ps between them and the number of slots Ns are the same for 2.4 GHz band only, 5 GHz band only, and both 2.4 GHz band and 5 GHz band (this embodiment). That is, for example, when the number of slots Ns is 3, the slot length Ls for both the 2.4 GHz band and the 5 GHz band (this embodiment) is the slot resonance frequency dedicated to the 2.4 GHz band with Ns3 slots and the number of slots. The slot resonance frequency is between Ns3 slot resonance frequencies dedicated to the 5 GHz band.

Next, an example of arrangement in the slot of the leaky coaxial cable 10 of the present embodiment will be described.
FIG. 15 is a view showing an example of the slot arrangement of the leaky coaxial cable 10 according to the present embodiment. In the example shown in FIG. 15, the slot angle θs is 45 °.
The leaky coaxial cable 10A is an example in which the number of slots Ns is 1, and the slot length is Lsa. The second pitch between the slot 101 (11) of the first slot group 101 ′ and the slot 101 (21) of the second slot group 101 ′ is Ps.
The leaky coaxial cable 10B is an example in which the number of slots Ns is 3, and the slot length is Lsb shorter than Lsa. The second pitch between the first slot 101 (11) of the first slot group 101 ′ and the first slot 101 (21) of the second slot group 101 ′ is Ps, The second pitch between the second slot 101 (12) of the slot group 101 ′ and the second slot 101 (22) of the second slot group 101 ′ is Ps, and the first slot group 101 ′. The second pitch between the third slot 101 (13) and the third slot 101 (23) of the second slot group 101 ′ is Ps.

  In FIG. 15, a slot 101 (11), a slot 101 (12), and a slot 101 (13) form one slot group 101 '. In the leaky coaxial cable 10A, the slot 101 (11) is one slot group 101 '. As described above, in the leaky coaxial cable 10 of the present embodiment, a slot group consisting of slots having a long hole shape with a number Ns (where Ns is an integer of 1 or more) in the lengthwise direction of the leaky coaxial cable is periodic. Are provided on the outer conductor 104.

  Thus, in the present embodiment, when a plurality of slots 101 are arranged, they are arranged in order to the right of the first slot. In the leaky coaxial cable 10B, the first pitch Ps ′ between the first slot 101 (11) and the second slot 101 (12), the second slot 101 (12), and the third slot 101 (13). ) And the first pitch Ps ′ have the same length.

  Here, the first pitch Ps ′ when the number of slots 101 is Ns is expressed by the following equation (8). For example, the first pitch Ps' between slots in the case of three is (1/9) Ps.

As described above, the leaky coaxial cable 10 of the present embodiment corresponds to a plurality of frequency bands of 2.4 GHz band and 5 GHz band, so that the resonance frequency of the slot 101 is the slot resonance frequency dedicated to the 2.4 GHz band and the 5 GHz band. The frequency is shifted to a frequency between the dedicated slot resonance frequency. As a result, in the leaky coaxial cable 10 of this embodiment, when the number of slots Ns is the same, the slot length Ls of the slot 101 is shorter than the slot length dedicated for the 2.4 GHz band and longer than the slot length dedicated for the 5 GHz band.
Also, the leaky coaxial cable 10 of the present embodiment has a large coupling loss when the slot length is shortened, so the slot 101 (12) having the same slot length Ls is adjacent to the first slot 101 (11).・ By providing a plurality of, it is possible to obtain an optimum coupling loss.

  In the present embodiment, the outer diameter of the center conductor 102 is 5 mm, the outer diameter of the highly foamed insulator 103 is 12 mm, the outer diameter of the outer conductor 104 is 13 mm, the outer diameter of the sheath 105 is 15 mm, the slot width Ws is 2 mm, The relationship between the slot length Ls, the slot angle θs, and the number of slots Ns in which the leaky coaxial cable 10 having the second pitch Ps between the slot groups of 85 mm can be used in both the 2.4 GHz band and the 5 GHz band is expressed by the equation (4 ).

  Thereby, according to this embodiment, the leaky coaxial cable 10 which can be used in a several frequency band is realizable.

  The above-described leaky coaxial cable 10 can transmit or receive radio waves in the 2.4 GHz band and the 5 GHz band.

<Wireless communication system>
Next, a radio communication system 1 using the above-described leaky coaxial cable 10 will be described.
FIG. 16 is a diagram illustrating a configuration example of the wireless communication system 1 using the leaky coaxial cable 10 according to the present embodiment.
As shown in FIG. 16, an access point 30 is connected to the leaky coaxial cable 10. The access point 30 transmits and receives radio waves in the 2.4 GHz band and the 5 GHz band using the leaky coaxial cable 10.
The terminal 41 is, for example, a smartphone, a tablet terminal, a portable game device, or the like, and performs wireless communication using the 2.4 GHz band. The terminal 41 includes an antenna 411 that receives or transmits radio waves in at least the 2.4 GHz band.
The terminal 42 is, for example, a smartphone, a tablet terminal, a portable game device, or the like, and performs wireless communication using a 5 GHz band. The terminal 43 includes an antenna 421 that receives or transmits radio waves in at least the 5 GHz band.

As a result of experiments using the wireless communication system 1 shown in FIG. 16, stable wireless communication was possible in both the 2.4 GHz band and the 5 GHz band.
Also from this experimental result, it was confirmed that the leaky coaxial cable 10 of the present embodiment can achieve good wireless communication in both the 2.4 GHz band and the 5 GHz band.

In the example described above, the leaky coaxial cable 10 corresponding to the 2.4 GHz band and the 5 GHz band has been described as an example, but the plurality of bands may be other frequency bands. For example, in the case of the first band B1 and the second band B2 having a frequency higher than that of the first band B1, settings are made so as to satisfy at least one of the following conditions.
Condition I. Setting the slot resonant frequency of the leaky coaxial cable between the slot resonant frequency of the leaky coaxial cable dedicated to the first band B1 and the slot resonant frequency of the leaky coaxial cable dedicated to the second band B2 II. The slot length Ls is shorter than the slot length Ls of the leaky coaxial cable dedicated to the first band B1, and longer than the slot length Ls of the leaky coaxial cable dedicated to the second band B2. Setting conditions III. The best slot length Ls ₁ in the first band B1, the optimal average of the slot length Ls ₂ in the second band B2 (equation (6))

  Thus, by setting so as to satisfy at least one of the conditions I to III, it is possible to provide the leaky coaxial cable 10 that can handle two bands.

<Second Pitch Ps Between Slot Groups 101 ′ of Leaky Coaxial Cable 10>
Next, the second pitch Ps between the slot groups 101 ′ of the leaky coaxial cable 10 in the embodiment will be further described.

  First, the mode generation frequency fsm (MHz) and the mode resonance frequency fsrm (MHz) will be described. The mode generation frequency fsm is a frequency at which the m-th order mode is generated, and is a frequency at which the radiation angle is −90 ° as will be described later. The mode resonance frequency fsrm is the m-th order mode resonance frequency and is a frequency at which the radiation angle becomes 0 ° as will be described later. The mode is a radiation mode.

Since the second pitch Ps giving the mode generation frequency is expressed by the following equation (9), the mode generation frequency fsm (MHz) is expressed by the following equation (10). In Equation (9), Co is the speed of light, and εr is the relative dielectric constant of the insulator. Further, m represents an mode, for example m = 1 is theta _-1 mode (first radiation mode).

From the equation (10), the mode generation frequency fs1 (GHz) of the θ- ₁ mode is 1.68 GHz as in the following equation (11).

From Expression (10), the mode generation frequency fs2 (GHz) in the θ- ₂ mode (second radiation mode) is 3.37 GHz as shown in the following Expression (12).

From the equation (10), the mode generation frequency fs3 (GHz) in the θ- ₃ mode (third radiation mode) is 5.05 GHz as in the following equation (13).

  Next, since the second pitch Ps giving the mode resonance frequency is expressed by the following equation (14), the mode resonance frequency fsrm (MHz) is expressed by the following equation (15).

From the equation (15), the mode resonance frequency fsr1 (GHz) of the θ- ₁ mode is 3.22 GHz as in the following equation (16).

From the equation (15), the mode resonance frequency fsr2 (GHz) of the θ- ₂ mode is 6.44 GHz as in the following equation (17).

FIG. 22 shows the mode generation frequency fsm (fs1, fs2, fs3) and the mode resonance frequency fsrm (fsr1, fsr2) described above on the mode chart.
FIG. 22 is a diagram showing a radiation mode chart of the leaky coaxial cable 10 when the pitch according to the present embodiment is 85 mm. In FIG. 22, the horizontal axis represents frequency (MHz), and the vertical axis represents radiation angle (°). FIG. 22 shows the calculation result when the second pitch Ps between the slot groups is 85 mm and the relative dielectric constant εr is 1.2. Further, the symbol g21 is the lowest order mode θ- ₁ mode, the symbol g22 is the θ- ₂ mode, and the symbol g23 is the θ- ₃ mode.

As indicated by reference numeral g21 in FIG. 22, in the θ- ₁ mode of the lowest order mode, the mode generation frequency fs1 is 1.68 GHz, and the mode resonance frequency fsr1 is 3.22 GHz. Further, as indicated by reference sign g21, the radiation angle of the mode generation frequency fs1 is −90 °, the radiation angle of the mode resonance frequency fsr1 is 0 °, and the radiation angle of the frequency equal to or higher than the mode resonance frequency fsr1 is from 0 °. It increases to a positive angle.

As indicated by reference sign g22, in the θ- ₂ mode, the mode generation frequency fs2 is 3.37 GHz. As indicated by reference sign g22, the radiation angle of the mode generation frequency fs2 is −90 °, and the radiation angle approaches 0 ° toward the 6.44 GHz of the mode resonance frequency fsr2 as the frequency increases. The radiation angle becomes 0 ° at the mode resonance frequency fsr2, and the radiation angle having a frequency equal to or higher than the mode resonance frequency fsr2 increases from 0 ° to a positive angle.

Further, as indicated by reference numeral g23, the theta _-3 mode, mode generating frequency fs3 is 5.05GHz. Further, as indicated by reference sign g23, the radiation angle of the mode generation frequency fs3 is −90 °, and the radiation angle approaches 0 ° toward the mode resonance frequency fsr3 as the frequency increases. Note that the radiation angle becomes 0 ° at the mode resonance frequency fsr3, and the radiation angle having a frequency equal to or higher than the mode resonance frequency fsr3 increases from 0 ° to a positive angle.

Then, as shown in FIG. 22, by setting the second pitch Ps between the slot groups 101 ′ to 85 mm, the θ- ₁ mode contributes to radiation in the 2.4 GHz band. In the 5 GHz band, the θ- ₁ mode, the θ- ₂ mode, and the θ- ₃ mode contribute to radiation. Thus, in the present embodiment, the leaky coaxial cable 10 can be radiated in both the 2.4 GHz band and the 5 GHz band by setting the second pitch Ps between the slot groups to 85 mm.

Here, the condition of the second pitch Ps between the slot groups will be examined.
The wavelength λo of 2.4 GHz is 125 mm. Under this condition, the lower limit of the second pitch Ps between the slot groups is Ps> 125 / (1 + √1.2) = 60 mm.

FIG. 23 is a diagram showing a radiation mode chart of the leaky coaxial cable when the pitch is 60 mm. In FIG. 23, the horizontal axis represents frequency (MHz) and the vertical axis represents radiation angle (°). FIG. 23 shows the calculation result when the second pitch Ps between the slot groups is 60 mm and the relative dielectric constant εr is 1.2. Symbol g31 is the θ- ₁ mode of the lowest order mode, and symbol g32 is the θ- ₂ mode.

When the second pitch Ps between the slot groups is 60 mm, radiation occurs in both the 2.4 GHz band and the 5 GHz band. However, the mode generation frequency fs1 of the θ- ₁ mode is 2.39 GHz according to the equation (10). For this reason, at 2.4 GHz to be used, since the radiation angle is approximately −90 °, it cannot be used. That is, in order to radiate in both the 2.4 GHz band and the 5 GHz band, the second pitch Ps between the slot groups is too short at the lower limit of 60 mm.

Next, a case where the second pitch Ps between the slot groups is longer than 85 mm is confirmed.
As described above, the wavelength λo of 2.4 GHz is 125 mm. A case where the second pitch Ps between the slot groups is substantially matched with the used wavelength is confirmed. However, the wavelength used here is not the free space wavelength λo but the wavelength inside the leaky coaxial cable 10. The second pitch Ps between the slot groups under this condition is about 114 mm (≈λo / √ (εr) = 125 / √ (1.2)).

FIG. 24 is a diagram showing a radiation mode chart of the leaky coaxial cable when the second pitch between the slot groups is 114 mm. In FIG. 24, the horizontal axis represents frequency (MHz), and the vertical axis represents radiation angle (°). FIG. 24 shows the calculation result when the second pitch Ps between the slot groups is 114 mm and the relative dielectric constant εr is 1.2. Symbol g41 is the lowest order θ- ₁ mode, symbol g42 is the θ- ₂ mode, symbol g43 is the θ- ₃ mode, and symbol g44 is the θ- ₄ mode.

As shown in FIG. 24, radiation occurs in both the 2.4 GHz band and the 5 GHz band. However, the 2.4 GHz band cannot be used because the resonance frequency of the θ- ₁ mode matches 2.4 GHz as indicated by reference numeral g41. Thus, it is necessary to set the second pitch Ps between the slot groups while avoiding the resonance frequency.

As shown in FIG. 24, when the second pitch Ps between the slot groups is set avoiding the resonance frequency, for example, when the second pitch Ps between the slot groups is 85 mm or more and 114 mm or less, the 2.4 GHz band Then, the θ- ₁ mode contributes to radiation. In the 5 GHz band, the θ- ₁ mode, the θ- ₂ mode, the θ- ₃ mode, and the θ- ₄ mode contribute to radiation. Thus, in this embodiment, the leaky coaxial cable 10 is radiated in both the 2.4 GHz band and the 5 GHz band by setting the second pitch Ps between the slot groups to be 85 mm or more and avoiding the resonance frequency. Can do. In addition, when the second pitch Ps between the slot groups is 114 mm or more, the number of radiation modes contributing to the 5 GHz band increases as shown in FIG. For this reason, the second pitch Ps between the slot groups is 114 mm in which the radiation mode contributing to the 5 GHz band, for example, the θ ₋₁ mode, the θ ₋₂ mode, the θ ₋₃ mode, and the θ ₋₄ mode contributes depending on the application. The following may be used.

  As described above, the range condition of the second pitch Ps between the slot groups for radiating in both the 2.4 GHz band and the 5 GHz band is the following expression (18).

  Further, as described above, the condition of the second pitch Ps between the slot groups for radiating in both the 2.4 GHz band and the 5 GHz band is to avoid the resonance frequency due to the first pitch between the slots.

As described above, the leaky coaxial cable 10 of the present embodiment is formed as follows.
(I) A slot group 101 ′ composed of two or more slots 101 having a long hole shape is periodically provided on the outer conductor at the second pitch Ps in the lengthwise direction of the leaky coaxial cable.
(Ii) The first slot length in which the coupling loss is a value within a predetermined range (60 ± 5 dB) in the first band (for example, 2.4 GHz band) and the second band (for example, 5 GHz band). In this case, the coupling loss is between the second slot length where the value is within a predetermined range (60 ± 5 dB).
(Iii) The second pitch Ps between the slot groups radiates using at least a first radiation mode (for example, θ- ₁ mode) in the first band, and at least the first radiation mode in the second band. Radiation is performed using (for example, the θ- ₁ mode) and the second radiation mode (for example, the θ- ₂ mode).
(Iv) The relationship among the slot angle θs (°), the number of slots Ns (pieces), and the slot length Ls (mm) is Ls = (0.01θs−2) Ns−0.1θs + 21.
(V) The second pitch Ps between the slot groups is larger than λo / (1 + √ (εr)).

  Since the leaky coaxial cable 10 of the present embodiment is formed as described above, radio waves can be radiated in both the first band and the second band, and the first band and the second band can be radiated. It is possible to obtain a characteristic in which the coupling loss is a value within a predetermined range on both sides.

DESCRIPTION OF SYMBOLS 1 ... Wireless communication system, 10 ... Leaky coaxial cable, 30 ... Access point, 41, 42 ... Terminal, 101, 101 (12), 101 (12), 101 (13), 101 (21), 101 (22), DESCRIPTION OF SYMBOLS 101 (23) ... Slot, 101 '... Slot group, 102 ... Center conductor, 103 ... High foaming insulator (insulator), 104 Outer conductor, 105 ... Sheath, 41, 42 ... Terminal, 411, 412 ... Antenna

Claims (11)

A slot comprising a center conductor, an insulator that concentrically covers the center conductor, a core that covers the insulator concentrically, and two or more slots in the length direction of the leaky coaxial cable A group comprising outer conductors periodically provided at a pitch Ps (mm),
The slot length Ls (mm), which is the length in the longitudinal direction of the slot, is a first slot length in which the coupling loss has a value within a predetermined range in the first band, and a second frequency that is higher in frequency than the first band. The leaky coaxial cable is between the second slot length in which the coupling loss is a value in a predetermined range in the band. A central conductor, an insulator covering the central conductor concentrically, and covering the insulator concentrically, the number of leaking coaxial cables in the length direction is Ns (where Ns is an integer of 1 or more). A slot group composed of slots having a long hole shape and an outer conductor provided periodically with a pitch Ps,
A slot length Ls which is a length in the longitudinal direction of the slot, and the resonance frequency of the slot is a first resonance frequency by a slot length in which a coupling loss is a value in a predetermined range in the first band; The leaky coaxial cable having the slot length Ls between the second resonance frequency due to the slot length in which the coupling loss has a value in a predetermined range in the second band having a frequency higher than that of the first band.   The leaky coaxial cable according to claim 1 or 2, wherein a value of the predetermined range of the coupling loss is 60 ± 5 dB. The pitch Ps is
Radiating in the first band using at least a first radiation mode;
The leaky coaxial according to any one of claims 1 to 3, wherein the second coaxial waveguide is configured to radiate at least using the first radiation mode and the second radiation mode in the second band. cable. The slot is inclined at an angle θs (°) in the longitudinal direction of the leaky coaxial cable, and is the number Ns of the slots (where Ns is an integer of 1 or more),
The slot length Ls (mm) is expressed by the following equation: Ls = (0.01θs−2) Ns−0.1θs + 21
The leaky coaxial cable according to any one of claims 1 to 4, which has a relationship of:   The leaky coaxial cable according to claim 5, wherein the slot length Ls is in a range of ± 10% of the relational expression.   The leaky coaxial cable according to claim 6, wherein the slot length Ls is in a range of ± 5% of the relational expression.   The leaky coaxial cable according to any one of claims 4 to 7, wherein an angle θs of the slot is between 5 ° and 90 °.   The leaky coaxial cable according to any one of claims 1 to 8, wherein the first band is a 2.4 GHz band, and the second band is a 5 GHz band. λo is the free space wavelength for the frequency used, εr is the dielectric constant of the insulator,
The leaky coaxial cable according to any one of claims 1 to 9, wherein the pitch Ps is larger than λo / (1 + √ (εr)). An antenna that receives or transmits radio waves transmitted or received by the leaky coaxial cable according to any one of claims 1 to 10 in a first frequency band and a second frequency band;
A terminal having the antenna;
A wireless communication system comprising:

Images