A conductor is mounted on a circuit board parallel to its side along which a radiation of a radio frequency signal is generated. The proximal end of the L-shaped conductor is electrically connected to a ground pattern formed on the rear surface of a circuit board 1 , and the distal end of the L-shaped conductor is open. The position at which the conductor is connected to the ground pattern is set to be a position spaced apart by a quarter-wavelength of a radio-frequency signal from a feed point of an antenna. The total length of the conductor is set to be a half-wavelength of the radio-frequency signal.
1. A radio module in which a radio circuit is mounted on a circuit board having a ground pattern, the radio module comprising:
an antenna connected to the radio circuit; and
a conductor located at a position facing a second surface opposing a first surface facing a user or a side surface of the circuit board, in which a radiation of a radio frequency signal is generated, and configured to partially shunt a current flowing to the ground pattern of the circuit board,
wherein a proximal end of the conductor is connected to the ground pattern at or near a position spaced apart by a quarter-wavelength of a radio-frequency signal by the antenna from a connection point between the radio circuit and the antenna.
2. The radio module according to claim 1 , further comprising an impedance adjustment circuit located between the proximal end of the conductor and the ground pattern of the circuit board, and configured to adjust an impedance of the conductor from the viewpoint of the connection point between the radio circuit and the antenna.
3. The radio module according to claim 2 , wherein the impedance adjustment circuit includes an inductor which connects the proximal end of the conductor with the ground pattern of the circuit board in series.
4. The radio module according to claim 2 , wherein the impedance adjustment circuit includes a variable reactance element which connects the proximal end of the conductor with the ground pattern of the circuit board in series.
5. The radio module according to claim 1 , further comprising a switch located between the proximal end of the conductor and the ground pattern of the circuit board, and configured to switch between a state in which the conductor is connected to the ground pattern and a state in which the conductor is disconnected from the ground pattern, in accordance with an operation mode required by the radio module.
6. The radio module according to claim 5 , wherein the switch is closed in a communication mode to connect the proximal end of the conductor with the ground pattern of the circuit board, and opened in a data communication mode to disconnect the proximal end of the conductor from the ground pattern of the circuit board.
7. The radio module according to claim 1 , wherein the conductor is at least partially meander line or zigzag over a total length.
8. A radio module in which a radio circuit is mounted on a circuit board having a ground pattern, the radio module comprising:
an antenna connected to the radio circuit; and
a conductor located at a position facing a second surface opposing a first surface facing a user or a side surface, along a side of the circuit board, in which a radiation of a radio frequency signal is generated, and configured to partially shunt a current flowing to the ground pattern of the circuit board,
wherein a distal end of the conductor is open, and a proximal end of the conductor is connected to the ground pattern at a position at which an effective electrical length from a connection point between the radio circuit and the antenna to the distal end is set to be a half-wavelength of a radio-frequency signal by the antenna or an approximate value of the half-wavelength.
9. The radio module according to claim 8 , further comprising an impedance adjustment circuit located between the proximal end of the conductor and the ground pattern of the circuit board, and configured to adjust an impedance of the conductor from the viewpoint of the connection point between the radio circuit and the antenna.
10. The radio module according to claim 9 , wherein the impedance adjustment circuit includes an inductor which connects the proximal end of the conductor with the ground pattern of the circuit board in series.
11. The radio module according to claim 9 , wherein the impedance adjustment circuit includes a variable reactance element which connects the proximal end of the conductor with the ground pattern of the circuit board in series.
12. The radio module according to claim 8 , further comprising a switch located between the proximal end of the conductor and the ground pattern of the circuit board, and configured to switch between a state in which the conductor is connected to the ground pattern and a state in which the conductor is disconnected from the ground pattern, in accordance with an operation mode required by the radio module.
13. The radio module according to claim 12 , wherein the switch is closed in a communication mode to connect the proximal end of the conductor with the ground pattern of the circuit board, and opened in a data communication mode to disconnect the proximal end of the conductor from the ground pattern of the circuit board.
14. A radio module in which a first radio circuit and a second radio circuit are mounted on a circuit board having a ground pattern, the radio module comprising:
a first antenna connected to the first radio circuit;
a second antenna connected to the second radio circuit; and
a connection circuit located between the second radio circuit and the second antenna,
wherein the second antenna is located along a side of the circuit board, in which a radiation of a radio frequency signal is generated, if performing radio transmission using the first antenna, and located at or near a position spaced apart by a quarter-wavelength of a radio-frequency signal by the first antenna from a connection point between the first antenna and the first radio circuit.
15. The radio module according to claim 14 , wherein the connection circuit includes a variable reactance element.
16. A radio module in which a first radio circuit operating in a first period and a second radio circuit operating in a second period different from the first period are mounted on a circuit board having a ground pattern, the radio module comprising:
a first antenna connected to the first radio circuit;
a second antenna located at a position facing a second surface opposing a first surface facing a user or a side surface, along a side of the circuit board, in which a radiation of a radio frequency signal is generated, in the first period, and connected to the second radio circuit; and
a connection switching circuit inserted between the second radio circuit and the second antenna,
wherein the connection switching circuit connects, in the second period, the second antenna to the second radio circuit, and connects, in the first period, the second antenna to the ground pattern at or near a position spaced apart by a quarter-wavelength of a radio-frequency signal by the first antenna from a connection point between the first radio circuit and the first antenna.
17. The radio module according to claim 16 , wherein
the connection switching circuit includes a switch and an inductor, and
the switch directly connects, in the second period, the second antenna to the second radio circuit, and connects, in the first period, the second antenna to the ground pattern via the inductor at or near a position spaced apart by the quarter-wavelength of the radio-frequency signal by the first antenna from the connection point between the first radio circuit and the first antenna.