Automatic gain control apparatus and method
View Patent ↗An automatic gain control apparatus includes a first comparing module, a counting module, a second comparing module, and a control module. The first comparing module compares an input signal with a first threshold level and a second threshold level to generate a first compared output signal and a second compared output signal respectively. The counting module performs counting operations upon the first compared output signal and the second compared output signal to generate a first counting number and a second counting number respectively. The second comparing module compares the first counting number with a first threshold number to generate a first detection signal and compares the second counting number with a second threshold number to generate a second detection signal. The control module controls the gain of a radio frequency amplifier or an intermediate frequency amplifier according to the first detection signal and the second detection signal.
1. An automatic gain control apparatus for controlling a radio frequency amplifier and an intermediate frequency amplifier, comprising:
a first comparing module, for comparing an input signal with a first threshold level and a second threshold level to generate a first compared output signal and a second compared output signal respectively;
a counting module, coupled to the first comparing module, for performing a first counting operation upon the first compared output signal to generate a first counting number, and performing a second counting operation upon the second compared output signal to generate a second counting number;
a second comparing module, coupled to the counting module, for comparing the first counting number with a first threshold number to generate a first detection signal, and comparing the second counting number with a second threshold number to generate a second detection signal; and
a control module, coupled to the second comparing module, the radio frequency amplifier and intermediate frequency amplifier, for controlling the gain of the radio frequency amplifier or the intermediate frequency amplifier according to the first detection signal and the second detection signal.
2. The automatic gain control apparatus of claim 1 , wherein the first threshold level is greater than the second threshold level, the first detection signal is utilized to decrease the gain of the radio frequency amplifier or the intermediate frequency amplifier, and the second detection signal is utilized to increase the gain of the radio frequency amplifier or intermediate frequency amplifier.
3. The automatic gain control apparatus of claim 2 , further comprising:
a timer module, coupled to the second comparing module, for counting a first predetermined period of time and a second predetermined period of time;
wherein the second comparing module outputs the first detection signal and the first counting number is reset each time when the first predetermined period of time counted by the timer module expires; and outputs the second detection signal and the second counting number is reset each time when the second predetermined period of time counted by the timer module expires.
4. The automatic gain control apparatus of claim 3 , wherein the first predetermined period of time is not longer than the second predetermined period of time.
5. The automatic gain control apparatus of claim 4 , wherein when the first detection signal is first asserted, the control module sends a gain control signal to decrease the gain of the radio frequency amplifier or the intermediate frequency amplifier by a first gain decrease rate, and when consecutive first detection signals are asserted, the control module sends the gain control signal to decrease the gain of the radio frequency amplifier or the intermediate frequency amplifier by a second gain decrease rate, in which the second gain decrease rate is greater than the first gain decrease rate.
6. The automatic gain control apparatus of claim 4 , wherein when the second detection signal is first asserted, the control module sends a gain control signal to increase the gain of the radio frequency amplifier or the intermediate frequency amplifier by a first gain increase rate, and when consecutive second detection signals are asserted, to increase the gain of the radio frequency amplifier or the intermediate frequency amplifier by a second gain increase rate, in which the second gain increase rate is greater than the first gain increase rate.
7. The automatic gain control apparatus of claim 1 , further comprising:
an absolute value extracting unit, coupled to the first comparing model, for receiving a signed digital signal and generating the input signal with positive amplitude level.
8. An automatic gain control method for controlling a radio frequency amplifier and an intermediate frequency amplifier, comprising:
(a) comparing an input signal with a first threshold level and a second threshold level to generate a first compared output signal and a second compared output signal respectively;
(b) performing a first counting operation upon the first compared output signal to generate a first counting number and a second counting operation upon the second compared output signal to generate a second counting number;
(c) comparing the first counting number with a first threshold number to generate a first detection signal and the second counting number with a second threshold number to generate a second detection signal; and
(d) controlling the gain of the radio frequency amplifier or the intermediate frequency amplifier according to the first detection signal and the second detection signal.
9. The automatic gain control method of claim 8 , wherein the first threshold level is greater than the second threshold level, the first detection signal is utilized to decrease the gain of the radio frequency amplifier or the intermediate frequency amplifier, and the second detection signal is utilized to increase the gain of the radio frequency amplifier or the intermediate frequency amplifier.
10. The automatic gain control method of claim 9 , further comprising:
counting a first predetermined period of time and a second predetermined period of time;
wherein the first counting number is reset each time when the first predetermined period of time expires; and the second counting number is reset each time when the second predetermined period of time counted by the timer module expires.
11. The automatic gain control method of claim 10 , wherein the first predetermined period of time is not longer than the second predetermined period of time.
12. The automatic gain control method of claim 11 , wherein when the first detection signal is first asserted, decreases the gain of the radio frequency amplifier or the intermediate frequency amplifier by a first gain decrease rate, and when consecutive first detection signals are asserted, decreases the gain of the radio frequency amplifier or the intermediate frequency amplifier by a second gain decrease rate, in which the second gain decrease rate is greater than the first gain decrease rate.
13. The automatic gain control method of claim 11 , wherein when the second detection signal is first asserted, increases the gain of the radio frequency amplifier or the intermediate frequency amplifier by a first gain increase rate, and when consecutive second detection signals are asserted, increases the gain of the radio frequency amplifier or the intermediate frequency amplifier by a second gain increase rate, in which the second gain increase rate is greater than the first gain increase rate.