Communication apparatus

1. A communication apparatus, comprising:

a substrate provided with a reference potential electrode;

a first communication unit provided on a first principal surface of the substrate and configured to transmit and receive;

a first signal line provided on the first principal surface of the substrate and having one end connected to the first communication unit;

a first terminal provided on the first principal surface of the substrate and connected to the other end of the first signal line;

a second signal line having one end connected to the first terminal, the second signal line being connected to the first signal line through the first terminal;

a variable capacitance portion having one end connected to the other end of the second signal line; and

an inductor portion having one end connected to the other end of the variable capacitance portion, wherein

the communication apparatus executes communication through a living body.

2. The communication apparatus according to claim 1 , wherein

the variable capacitance portion includes first and second conductors,

each of the first and second conductors has a plate shape,

the first conductor is connected to the other end of the second signal line, and

the second conductor is provided at a predetermined distance apart from the first conductor and is connected to the inductor portion.

3. The communication apparatus according to claim 2 , wherein communication is executed when the first and second conductors are close to or in contact with the living body.

4. The communication apparatus according to claim 2 , further comprising a box-shaped housing covering and accommodating inside the substrate, the first communication unit, the first signal line, the first terminal, the second signal line, the variable capacitance portion, and the inductor portion.

5. The communication apparatus according to claim 2 , further comprising a box-shaped housing covering and accommodating inside the substrate, the first communication unit, the first signal line, the first terminal, the second signal line, and the inductor portion.

6. The communication apparatus according to claim 5 , wherein

the first conductor is provided on an outer surface of a first sidewall of the housing, the second conductor is provided on an outer surface of a second sidewall of the housing that is opposite to the first sidewall, and the inductor portion is provided on an inner surface of the second sidewall of the housing.

7. The communication apparatus according to claim 5 , wherein

the first conductor is provided on an outer surface of a first sidewall of the housing, the second conductor is provided on an outer surface of a second sidewall of the housing that is adjacent to the first sidewall, and the inductor portion is provided on an inner surface of the second sidewall of the housing.

8. The communication apparatus according to claim 1 , further comprising a chip inductor between the first terminal and the one end of the second signal line.

9. The communication apparatus according to claim 1 , wherein

the variable capacitance portion includes first and second conductors,

the first conductor is connected to the other end of the second signal line,

the second conductor is connected to the inductor portion, and

the first and second conductors constitute a growth ring structure with the first conductor located inside and the second conductor located a predetermined distance outside of the first conductor.

10. The communication apparatus according to claim 9 , wherein the first conductor has a circular shape, and the second conductor has a ring shape.

11. The communication apparatus according to claim 9 , wherein the first conductor has a rectangular shape, and the second conductor has a frame shape.

12. The communication apparatus according to claim 9 , wherein the first conductor has an elliptical shape, and the second conductor has a toroidal shape.

13. The communication apparatus according to claim 1 , wherein the substrate is a multi-layer substrate including a dielectric on the reference potential electrode.

14. The communication apparatus according to claim 1 , wherein each of the first and second conductors is composed of any one of an electrode, a conductive sheet, a conductive ink, and a transparent conducting material.

15. The communication apparatus according to claim 1 , wherein

the inductor portion includes a third signal line, a core, and a winding wire,

one end of the third signal line is connected to the other end of the variable capacitance portion,

the core is composed of a magnetic body, and

the winding wire is a conductor wound around the core, and one end of the winding wire is connected to the other end of the third signal line.

16. The communication apparatus according to claim 1 , further comprising: a fourth signal line, a second terminal, a fifth signal line, and a capacitor, wherein

one end of the fourth signal line is connected to the other end of the inductor portion,

the second terminal is provided on the first principal surface of the substrate,

the second terminal is connected to the other end of the fourth signal line,

the fifth signal line is provided on the first principal surface of the substrate,

one end of the fifth signal line is connected to the second terminal,

the fifth signal line is connected to the fourth signal line through the second terminal,

the capacitor is provided on the first principal surface of the substrate,

one end of the capacitor is connected to the other end of the fifth signal line while the other end of the capacitor is electrically connected to the reference potential electrode.