Antenna tuner and method for adjusting antenna impedance

1. A tuner of an antenna comprising:

a reference impedance resistor;

a first coupler having an isolated port connected to one end of the reference impedance resistor;

a second coupler having an input port connected to an output port of the first coupler and an output port connected to the antenna;

an impedance adjusting device group connected to the second coupler to adjust impedance of the antenna; and

an impedance controller generating an impedance adjustment control signal according to a first voltage, which is proportional to a first power detected in a coupled port of the first coupler, and a second voltage which is proportional to a second power detected in a coupled port of the second coupler, to provide the impedance adjustment control signal to the impedance adjusting device group.

2. The tuner of claim 1 , wherein the impedance adjusting device group comprises:

a transmission line;

a first switch having one end connected to one end of the transmission line and an opposite end connected to the input port of the second coupler;

a second switch having one end connected to an opposite end of the transmission line and an opposite end connected to the output port of the second coupler;

a first variable capacitor having one end connected to the one end of the transmission line; and

a second variable capacitor having one end connected to the opposite end of the transmission line.

3. The tuner of claim 2 , wherein the impedance controller turns on the first and second switches if an absolute value of a difference between the first and second voltages is greater than a first threshold voltage.

4. The tuner of claim 3 , wherein the impedance controller generates a control signal to adjust the first and second variable capacitors based on a third voltage, which corresponds to the absolute value of the difference between the first and second voltages, if the third voltage is smaller than a second threshold voltage in a state that the first and second switches are turned on, and applies the control signal to the first and second variable capacitors. 15

5. The tuner of claim 2 , wherein the impedance adjusting device group further comprises:

a third switch having one end connected to the input port of the second coupler;

a fourth switch having one end connected to the output port of the second coupler;

a third variable capacitor having one end connected to an opposite end of the third switch and an opposite end connected to the coupled port of the second coupler; and

a fourth variable capacitor having one end connected to an opposite end of the fourth switch and an opposite end connected to an isolated portion of the second coupler.

6. The tuner of claim 5 , wherein the impedance controller turns on the first to fourth switches if an absolute value of a difference between the first and second voltages is greater than a first threshold voltage.

7. A method for adjusting antenna impedance by an antenna tuner including a reference impedance resistor, a first coupler having an isolated port connected to one end of the reference impedance resistor, a second coupler having an input port connected to an output port of the first coupler and an output port connected to the antenna, and an impedance adjusting device group connected to the second coupler to adjust impedance of an antenna, the method comprising:

detecting a first voltage which is proportional to a first power detected in a coupled port of the first coupler;

detecting a second voltage which is proportional to a second power detected in a coupled port of the second coupler;

generating an impedance adjustment control signal according to the first and second voltages; and

providing the impedance adjustment control signal to the impedance adjusting device group.

8. The method of claim 7 , wherein the impedance adjusting device comprises:

a transmission line;

a first switch having one end connected to one end of the transmission line and an opposite end connected to the input port of the second coupler;

a second switch having one end connected to an opposite end of the transmission line and an opposite end connected to the output port of the second coupler;

a first variable capacitor having one end connected to the one end of the transmission line; and

a second variable capacitor having one end connected to the opposite end of the transmission line.

9. The method of claim 8 , wherein, in the providing of the impedance adjustment control signal to the impedance adjusting device group, the first and second switches are turned on if an absolute value of a difference between the first and second voltages is greater than a first threshold voltage.

10. The method of claim 8 , wherein the impedance adjusting device group further comprises:

a third switch having one end connected to the input port of the second coupler;

a fourth switch having one end connected to the output port of the second coupler;

a third variable capacitor having one end connected to an opposite end of the third switch and an opposite end connected to the coupled port of the second coupler; and

a fourth variable capacitor having one end connected to an opposite end of the fourth switch and an opposite end connected to an isolated portion of the second coupler.

11. The method of claim 10 , wherein, in the providing of the impedance adjustment control signal to the impedance adjusting device group, the first to fourth switches are turned on if an absolute value of a difference between the first and second voltage is greater than a first threshold voltage.