Antenna
An antenna for wireless communication via a lossy medium, a structure thereof is optimized to improve transmission characteristics such as a transmission coefficient. The antenna includes at least one pair of electrodes and a sheath portion. The sheath portion includes a wiring electrically connecting each of the at least one pair of electrodes and a corresponding power supply terminal. The sheath portion is also referred to as a sheath. In this antenna, a minimum diameter of the electrode is larger than a width of the wiring included in the sheath portion. A shape of each of the at least one pair of electrodes is, for example, substantially spherical.
1 . An antenna comprising:
a first pair of electrodes, and
a first sheath portion enclosing first wiring that electrically connects each of the first pair of electrodes and a corresponding first pair of power supply terminals;
wherein a minimum diameter of each of the first pair of electrodes is larger than a width of the first wiring, and
wherein a center point of each of the first pair of electrodes and a center axis of a part of the first wiring are arranged on a first common line, and
wherein the first sheath portion is configured to extend substantially along the first common line.
2 . The antenna according to claim 1 , wherein
a distance between the first pair of electrodes is longer than a minimum diameter of each of the first pair of electrodes.
3 . The antenna according to claim 1 , wherein
each of the first pair of electrodes has a substantially spherical shape.
4 . The antenna according to claim 1 , wherein
each of the first pair of electrodes has a spheroidal shape.
5 . The antenna according to claim 1 , wherein
each of the first pair of electrodes has a polyhedral shape.
6 . The antenna according to claim 1 , wherein
the first sheath portion includes air therein.
7 . The antenna according to claim 1 , wherein
the first sheath portion includes pure water therein.
8 . The antenna according to claim 1 , wherein
the first sheath portion includes a material therein having conductivity of less than 1 S/m.
9 . The antenna according to claim 1 , wherein
each of the first pair of electrodes includes a coating film on a surface thereof.
10 . The antenna according to claim 9 , wherein
a magnitude of impedance at an operating frequency between each of the first pair of electrodes and an external medium is smaller than an impedance in a case where the coating film is not included.
11 . The antenna according to claim 1 , wherein
each of the first pair of electrodes includes a material therein having conductivity of less than 1 S/m.
12 . The antenna according to claim 1 , wherein
each of the first pair of electrodes includes a cavity therein.
13 . The antenna according to claim 12 , wherein
each of the first pair of electrodes includes at least one hole penetrating the cavity.
14 . The antenna according to claim 1 , further comprising a transformer in which a number of windings of a coil connected to the first pair of power supply terminals is smaller than a number of windings of another coil.
15 . The antenna according to claim 1 , further comprising a switching-type power amplifier connected to the first pair of power supply terminals.
16 . The antenna according to claim 1 , wherein a center axis of the first wiring is arranged on the first common line.
17 . The antenna according to claim 1 , further comprising
a second pair of electrodes; and
a second sheath portion enclosing second wiring that electrically connects each of the second pair of electrodes and a corresponding second pair of power supply terminals,
wherein a minimum diameter of each of the second pair of electrodes is larger than a width of the second wiring,
wherein a center point of each of the second pair of electrodes and a center axis of the second wiring are arranged on a second common line that is orthogonal to the first common line,
wherein the second sheath portion is configured to extend substantially along the second common line,
wherein a distance between the second pair of electrodes is longer than a minimum diameter of each of the second pair of electrodes, and
wherein each of the second pair of electrodes has one of a substantially spherical shape, a spheroidal shape or a polyhedral shape.
18 . The antenna according to claim 17 , wherein a center axis of the second sheath portion is arranged on the second common line.