Circuit for compensating temperature of automatic gain control circuit

1. A circuit for compensating temperature of an automatic gain control (AGC) circuit, comprising:

a low noise amplifier (LNA) configured to amplify a radio frequency (RF) signal;

an attenuation control unit configured to generate an attenuation control signal by sensing the amplified RF signal;

a PIN diode attenuator configured to attenuate the RF signal inputted to the LNA by driving a first PIN diode with the attenuation control signal; and

a temperature compensation unit configured to compensate a change in an amount of attenuation of the PIN diode caused by a temperature change,

wherein the temperature compensation unit comprises:

a first voltage divider to divide a power supply voltage;

a first operational (OP) amplifier to amplify the divided voltage of the first voltage divider;

a second voltage divider to divide an output voltage of the first OP amplifier with a second PIN diode having a same characteristic as the first PIN diode; and

a second OP amplifier to amplify an output of the second voltage divider and output the amplified voltage to the PIN diode attenuator.

2. The circuit of claim 1 , wherein the second voltage divider comprises two PIN diodes and a resistor coupled in series.

3. A PIN diode attenuator having a temperature compensation unit, in an automatic gain control (AGC) circuit including a low noise amplifier (LNA) for amplifying a radio frequency (RF) signal distributed from a duplexer and an attenuator for generating an attenuation control signal by sensing the RF signal amplified in LNA, comprising:

a first resistor coupled to receive the attenuation control signal;

a first PIN diode in which a cathode is coupled to the first resistor and an anode is coupled with an input terminal of the LNA in parallel;

a second PIN diode in which a cathode is coupled to the input terminal of the LNA in parallel;

a second resistor coupled between a first node and the anode of the second PIN diode;

a capacitor which is coupled between the first node and a ground; and

a temperature compensation unit is configured to compensate a voltage change between the first and second PIN diodes caused by a temperature change,

wherein the temperature compensation unit comprises:

a first voltage divider coupled to divide a power supply voltage;

a first operational (OP) amplifier coupled to amplify the divided voltage of the first voltage divider;

a second voltage divider including third and fourth PIN diodes having a same function as the first and second PIN diodes, and a resistor to divide an output voltage of the first OP amplifier; and

a second OP amplifier coupled to amplify an output voltage of the second voltage divider and output the amplified voltage to the first node.

4. The attenuator of claim 3 , wherein the temperature compensation unit applies a same voltage as in the voltage change of the first and second PIN diodes according to a temperature change to the first node.

5. A temperature control unit, comprising:

a first voltage divider configured to divide a power supply voltage;

a first operational (OP) amplifier coupled to amplify the divided voltage of the voltage divider;

a second voltage divider having first and second PIN diodes and a resistor configured to divide an output voltage of the first OP amplifier; and

a second OP amplifier coupled to amplify an output voltage of the second voltage divider and output the amplified voltage to a first node of the AGC, wherein the first and second PIN diodes have temperature characteristics substantially identical to corresponding PIN diodes of an automatic gain control (AGC) circuit that is being compensated.

6. The temperature control unit as claimed in claim 5 , wherein the AGC circuit comprises a low noise amplifier (LNA) configured to receive and amplify a radio frequency (RF) signal.

7. The temperature control unit as claimed in claim 6 , wherein the AGC circuit further comprises an attenuation control unit configured to generate an attenuation control signal by sensing the amplified RF signal.

8. The temperature control unit as claimed in claim 7 , wherein the AGC circuit further comprises a PIN diode attenuator configured to attenuate the RF signal inputted to the LNA by driving a first PIN diode with the attenuation control signal.

9. A method of compensating temperature in an automatic gain control (AGC) circuit, comprising:

dividing a power supply voltage by a first voltage divider;

amplifying the divided voltage of the first voltage divider to generate a first amplified signal;

dividing the first amplified signal by a second voltage divider having a first and a second PIN diodes and a resistor; and

amplifying the divided voltage of the second voltage divider to generate a compensation voltage, wherein the first and second PIN diodes have temperature characteristics substantially identical to corresponding PIN diodes of an automatic gain control (AGC) circuit that is being compensated.

10. The temperature compensating method as claimed in claim 9 , further comprising utilizing a low noise amplifier (LNA) to amplify a radio frequency (RF) signal in the AGC circuit.

11. The temperature compensating method as claimed in claim 10 , further comprising generating an attenuation control signal by an attenuation control unit that is configured to sense the amplified RF signal in the AGC circuit.

12. The temperature compensating method as claimed in claim 11 , further comprising driving a first PIN diode with the attenuation control signal by a PIN diode attenuator configured to attenuate the RF signal inputted to the LNA in the AGC circuit.

13. The temperature compensating method as claimed in claim 9 , further comprising applying the compensation voltage to the AGC circuit to compensate for temperature related voltage fluctuations in the AGC circuit.

14. A method of controlling an automatic gain control (AGC) circuit, comprising:

driving a first attenuator circuit with a first control signal so as to attenuate a signal input to the first attenuator circuit;

determining a change in an amount of attenuation of the first attenuator caused by a temperature difference by driving a second attenuator circuit coupled to the first attenuator circuit and having substantially a same temperature characteristic as the first attenuator circuit; and

driving the first attenuator circuit with a second control signal in addition to the first control signal to offset the determined change in the amount of attenuation of the first attenuator.

15. The method as claimed in claim 14 , wherein the first attenuator circuit includes first and second PIN diodes and the second attenuator circuit includes third and fourth PIN diodes have a same temperature characteristic as the first and second PIN diodes.

16. The method as claimed in claim 14 , wherein driving the second attenuator circuit comprises:

dividing a power supply voltage by a first voltage divider;

amplifying the divided voltage of the first voltage divider to generate a first amplified signal;

dividing the first amplified signal by a second voltage divider having a first and a second PIN diodes and a resistor; and

amplifying the divided voltage of the second voltage divider to generate a compensation voltage,

wherein the first and second PIN diodes have temperature characteristics substantially identical to corresponding PIN diodes of the first attenuator circuit.

17. The method as claimed in claim 14 , wherein the second attenuator circuit comprises:

a first voltage divider to divide a power supply voltage;

a first operational (OP) amplifier to amplify the divided voltage of the first voltage divider;

a second voltage divider to divide an output voltage of the first OP amplifier with a PIN diode having a same characteristic as a PIN diode of the first attenuator circuit; and

a second OP amplifier to amplify an output of the second voltage divider and output the amplified voltage to the PIN diode attenuator.

18. The method as claimed in claim 17 , wherein the second voltage divider comprises two PIN diodes and a resistor coupled in series.