Apparatus and method for determining signal power

1. An apparatus for determining signal power of a to-be-detected signal, comprising:

a first oscillator, for generating a first oscillating signal, with the first oscillating signal having a first frequency when the signal power of the to-be-detected signal is greater than a threshold, and the first oscillating signal having a second frequency when the signal power of the to-be-detected signal is smaller than the threshold; and

a determining circuit, for determining whether the first oscillating signal has either the first frequency or the second frequency, and generating a determination result accordingly.

2. The apparatus for determining signal power as claimed in claim 1 , wherein the determining circuit comprises:

a second oscillator, for providing a second oscillating signal;

a mixer, for mixing the first oscillating signal and the second oscillating signal to generate a mixed signal; and

a determining unit, for determining whether the first oscillating signal has either the first frequency or the second frequency according to the mixed signal.

3. The apparatus for determining signal power as claimed in claim 2 , wherein the second oscillating signal has the first frequency, and the determining unit determines that the first oscillating signal has the first frequency when the mixed signal comprises a direct current (DC) signal.

4. The apparatus for determining signal power as claimed in claim 2 , wherein the determining unit comprises:

a filter, for filtering the mixed signal to generate a filtered signal; and

a frequency detector, for detecting a frequency of the filtered signal, and determines that the first oscillating signal has the either the first frequency or the second frequency according to the filtered signal.

5. The apparatus for determining signal power as claimed in claim 1 , further comprising:

a calibrating circuit, for generating a calibration signal according to the determination result and transmits the calibration signal to a to-be-calibrated apparatus for providing the to-be-detected signal.

6. The apparatus for determining signal power as claimed in claim 5 , wherein the to-be-calibrated apparatus is a signal transmitter, the to-be-detected signal is a carrier leakage signal, and the calibration signal is for calibrating an input voltage of the signal transmitter.

7. The apparatus for determining signal power as claimed in claim 5 , wherein when the determination result indicates that the first oscillating signal has the first frequency, the calibrating circuit adjusts the calibration signal, and when the determination result indicates that the first oscillating signal has the second frequency, the calibrating circuit stops adjusting the calibration signal.

8. The apparatus for determining signal power as claimed in claim 7 , wherein the calibrating circuit selects one of a plurality of compensation voltages as the calibration signal when the determination result indicates that the first oscillating signal has the first frequency, and selects another one from the compensation voltages as the calibration signal when the determination result indicates that the first oscillating signal has the second frequency.

9. The apparatus for determining signal power as claimed in claim 1 , further comprising:

an attenuator, for processing the to-be-detected signal before the to-be-detected signal is inputted to the first oscillator.

10. The apparatus for determining signal power as claimed in claim 1 , wherein the second frequency is determined according to the first frequency and a signal power upper limit of the to-be-detected signal.

11. The apparatus for determining signal power as claimed in claim 1 , wherein the to-be-detected signal has the first frequency, and the second frequency is a free running frequency of the first oscillator.

12. The apparatus for determining signal power as claimed in claim 1 , wherein the to-be-detected signal has a third frequency, and the first frequency is 1/N of the third frequency, where N is an integer greater than 1.

13. The apparatus for determining signal power as claimed in claim 1 , wherein the to-be-detected signal has the first frequency, and the first oscillator comprises:

an injection-lock frequency multiplier, for generating a frequency-multiplied signal having a frequency that is N times the first frequency when the signal power is greater than the threshold, and the frequency-multiplied signal having a frequency that is N times the second frequency when the signal power is smaller than the threshold, where N is an integer greater than one; and

a frequency divider, for frequency dividing the frequency-multiplied signal by N to generate the first oscillating signal.

14. A method for determining signal power of a to-be-detected signal, comprising:

(a) providing the to-be-detected signal to an oscillator for generating an oscillating signal, with the oscillating signal having a first frequency when the signal power of the to-be-detected signal is greater than a threshold, and the oscillating signal having a second frequency when the signal power is smaller than the threshold; and

(b) determining whether the oscillating signal has either the first frequency or the second frequency, and generating a determination result accordingly.

15. The method as claimed in claim 14 , further comprising:

generating a calibration signal according to the determination result, and transmitting the calibration signal to a to-be-calibrated apparatus for providing the to-be-detected signal.

16. The method as claimed in claim 15 , further comprising:

attenuating the signal power of the to-be-detected signal to prompt the oscillating signal has the second frequency;

determining a positive test value and a negative test value, and respectively regarding the positive test value and the negative test value as the calibration signal that is provided to the to-be-calibrated apparatus;

determining a first determination result using the positive test value as the calibration signal, and determining a second determination result using the negative test value as the calibration signal; and

determining an initial calibration signal according to the first determination result and the second determination result.

17. The method as claimed in claim 16 , wherein when the first determination result indicates that the oscillating signal has the second frequency, and the second determination result indicates that the oscillating signal has the first frequency, the initial calibration signal is a positive calibration signal.

18. The method as claimed in claim 16 , wherein when the first determination result indicates that the oscillating signal has the first frequency, and the second determination indicates that the oscillating signal has the second frequency, the initial calibration signal is a negative calibration signal.