Passive relay device and passive relay method
A passive relay device ( 100 ) relays radio communication between the inside of a radio wave shielding structure ( 200 ) and the outside of the radio wave shielding the structure ( 200 ), and the device includes an internal antenna ( 10 ) which connects with the inside, an external antenna ( 20 ) which connects with the outside, and a connection part ( 30 ) which connects the internal antenna ( 10 ) and the external antenna ( 20 ).
1. A passive relay device which relays wireless communication between an inside of a radio wave shielding structure and an outside of the radio wave shielding structure, the inside of the radio wave shielding structure defining a first enclosure with an outer edge and a height measured perpendicular to the outer edge, and a second enclosure adjacent to the first enclosure, the passive relay device comprising:
an internal antenna which connects with the inside, the internal antenna including a directional antenna disposed in the first enclosure and directed toward the second enclosure located farther from the internal antenna than the first enclosure, the directional antenna having a directionality with respect to a radio wave reception angle that is adjustable based on a distance from the passive relay device to the outer edge of the first enclosure and the height of the first enclosure;
an external antenna which connects with the outside; and
a connection part which connects the internal antenna and the external antenna.
2. The passive relay device according to claim 1 , wherein
the radio wave shielding structure is a manhole buried underground,
the manhole has an iron cover provided with a through hole,
the connection part is provided at the through hole,
the internal antenna is provided in the vicinity of one end side of the through hole,
the external antenna is provided in the vicinity of the other end side of the through hole, and
the connection part has a length at least equal to the thickness of the iron cover.
3. The passive relay device according to claim 2 , wherein the radio wave shielding structure is made of a material including metal and concrete or resin concrete.
4. The passive relay device according to claim 2 , wherein the connection part is a coaxial cable or a waveguide.
5. The passive relay device according to claim 1 , wherein the radio wave shielding structure is made of a material including metal and concrete or resin concrete.
6. The passive relay device according to claim 1 , wherein the connection part is a coaxial cable or a waveguide.
7. The passive relay device according to claim 1 , wherein the second enclosure has a greater volume than the first enclosure.
8. The passive relay device according to claim 1 , wherein the radio wave reception angle (θ) is calculated using an expression:
θ
=
cos
-
1
b
2
+
c
2
-
a
2
2
bc
a
=
x
1
+
x
2
,
b
=
x
1
2
+
y
2
,
c
=
x
2
2
+
y
2
,
wherein x 1 is a first distance from the passive relay device to the outer edge of the first enclosure, x 2 is a second distance from the passive relay device to the outer edge of the first enclosure located opposite from the first distance, and y is the height of the first enclosure.
9. The passive relay device according to claim 8 , wherein the radio wave shielding structure is a manhole buried underground, and a sum of x 1 and x 2 equals a diameter of the manhole measured at ground level.
10. A passive relay method for relaying wireless communication between an internal device inside a radio wave shielding structure and an external device outside the radio wave shielding structure, the radio wave shielding structure defining therein a first enclosure with an outer edge and a height measured perpendicular to the outer edge, and a second enclosure adjacent to the first enclosure, the method comprising:
receiving data from the internal device located in the second enclosure;
transmitting the data to an external antenna through the connection part by an internal antenna, the internal antenna including a directional antenna disposed in the first enclosure and directed toward the second enclosure located farther from the internal antenna than the first enclosure, the directional antenna having a directionality with respect to a radio wave reception angle that is adjustable based on a distance from the passive relay device to the outer edge of the first enclosure and the height of the first enclosure, wherein the internal antenna transmits/receives radio waves to/from the internal device, the external antenna transmits and receives the radio waves to/from the external device, and the connection part connects the internal antenna and the external antenna;
receiving the data from the internal antenna through the connection part; and
transmitting the data to the external device by the external antenna.
11. The passive relay method according to claim 7 , wherein
the radio wave shielding structure is a manhole buried underground,
the manhole has an iron cover provided with a through hole,
the connection part is provided at the through hole,
the internal antenna is provided in the vicinity of one end side of the through hole,
the external antenna is provided in the vicinity of the other end side of the through hole, and
the connection part has a length at least equal to the thickness of the iron cover.
12. The passive relay method according to claim 10 , wherein the radio wave shielding structure is made of a material including metal and concrete or resin concrete.
13. The passive relay method according to claim 10 , wherein the connection part is a coaxial cable or a waveguide.
14. The passive relay method according to claim 10 , wherein the second enclosure has a greater volume than the first enclosure.
15. The passive relay method according to claim 10 , wherein the radio wave reception angle (θ) is calculated using an expression:
θ
=
cos
-
1
b
2
+
c
2
-
a
2
2
bc
a
=
x
1
+
x
2
,
b
=
x
1
2
+
y
2
,
c
=
x
2
2
+
y
2
,
wherein x 1 is a first distance from the passive relay device to the outer edge of the first enclosure, x 2 is a second distance from the passive relay device to the outer edge of the first enclosure located opposite from the first distance, and y is the height of the first enclosure.
16. The passive relay method according to claim 15 , wherein the radio wave shielding structure is a manhole buried underground, and a sum of x 1 and x 2 equals a diameter of the manhole measured at ground level.