Signal receiving apparatus and signal processing method thereof

1. A signal processing apparatus, comprising:

a phase recovery loop, performing a phase recovery process on an input signal according to a bandwidth setting;

a phase estimation circuit, generating an estimated phase associated with the input signal;

a phase noise detection circuit, determining a phase noise amount according to the estimated phase; and

a bandwidth setting circuit, calculating an average and a variance of the phase noise amount, and adjusting the bandwidth setting of the phase recovery loop according to the average and the variance,

wherein the bandwidth setting circuit comprises:

a detection circuit, detecting a channel quality of a communication channel where the signal processing apparatus is located to acquire a channel quality indicator;

a threshold setting circuit, determining a first threshold and a second threshold according to the channel quality indicator;

a first comparison circuit, comparing the average with the first threshold to generate a first comparison result;

a second comparison circuit, comparing the variance or a value associated with the variance with the second threshold to generate a second comparison result;

a control circuit, generating a control signal according to the first comparison result and the second comparison result; and

a selection circuit, selecting one bandwidth setting from a plurality of bandwidth settings and providing the one bandwidth setting to the phase recovery loop.

2. The signal processing apparatus according to claim 1 , wherein the channel quality indicator is a signal-to-noise ratio (SNR).

3. The signal processing apparatus according to claim 1 , wherein the value associated with the variance is a ratio of the variance and the average.

4. The signal processing apparatus according to claim 1 , wherein the control circuit comprises:

an accumulation circuit, increasing an accumulation result each time the second comparison result indicates that the variance or the value associated with the variance is higher than the second threshold, and reducing the accumulation result each time the second comparison result indicates that the variance or the value associated with the variance is not higher than the second threshold;

a third comparison circuit, generating a third comparison result according to whether the accumulation result is higher than a predetermined threshold; and

a first logic circuit, generating the control signal according to the first comparison result and the third comparison result.

5. The signal processing apparatus according to claim 4 , wherein the plurality of bandwidth settings comprise a large bandwidth setting and a small bandwidth setting; only when the first comparison result shows that the average is lower than the first threshold and the third comparison result shows that the accumulation result is not higher than the predetermined threshold, the first determination logic circuit causes the control signal to select the small bandwidth setting.

6. The signal processing apparatus according to claim 1 , wherein:

the threshold setting circuit further determines a fourth threshold lower than the first threshold, according to the channel quality indicator;

the bandwidth setting circuit further comprises a fourth comparison circuit, generating a fourth comparison result according to whether the average is higher than the fourth threshold; and

the control circuit comprises a second logic circuit, generating the control signal according to the first comparison result, the second comparison result and the fourth comparison result.

7. The signal processing apparatus according to claim 6 , wherein the plurality of bandwidth settings comprise a large bandwidth setting and a small bandwidth setting; when the fourth comparison result shows that the average is lower than or equal to the fourth threshold, the second logic circuit causes the control signal to select the small bandwidth setting.

8. A signal processing method, applied to a signal receiving apparatus, comprising:

(a) generating an estimated phase associated with an input signal;

(b) determining a phase noise amount according to the estimated phase;

(c) calculating an average and a variance of the phase noise amount; and

(d) adjusting, according to the average and the variance, a bandwidth setting of a phase recovery process performed on the input signal,

wherein step (d) comprises:

(d1) detecting a channel quality of a communication channel where the signal receiving apparatus is located to acquire a channel quality indicator;

(d2) determining a first threshold and a second threshold according to the channel quality indicator;

(d3) comparing the average with the first threshold to generate a first comparison result;

(d4) comparing the variance or a value associated with the variance with the second threshold to generate a second comparison result;

(d5) generating a control signal according to the first comparison result and the second comparison result; and

(d6) selecting one bandwidth setting from a plurality of bandwidth settings and providing the one bandwidth setting to the phase recovery process to use.

9. The signal processing method according to claim 8 , wherein the channel quality indicator is a signal-to-noise ratio (SNR).

10. The signal processing method according to claim 8 , wherein the value associated with the variance is a ratio of the variance and the average.

11. The signal processing method according to claim 8 , wherein step (d5) comprises:

increasing an accumulation result each time the second comparison result shows that the variance or the value associated with the variance is higher than the second threshold;

reducing the accumulation result each time the second comparison result shows that the variance or the value associated with the variance is not higher than the second threshold;

generating a third comparison result according to whether the accumulation result is higher than a predetermined threshold; and

generating the control signal according to the first comparison result and the third comparison result.

12. The signal processing method according to claim 11 , wherein the plurality of bandwidth settings comprise a large bandwidth setting and a small bandwidth setting; and the step of generating the control signal according to the first comparison result and the third comparison result comprises:

only when the first comparison result shows that the average is lower than the first threshold and the third comparison result shows that the accumulation result is not higher than the predetermined threshold, causing the control signal to select the small bandwidth setting.

13. The signal processing method according to claim 8 , wherein step (d) further comprises:

determining a fourth threshold lower than the first threshold according to the channel quality indicator; and

generating a fourth comparison result according to whether the average is higher than the fourth threshold;

and step (d5) comprises:

generating the control signal according to the first comparison result, the second comparison result and the fourth comparison result.

14. The signal processing method according to claim 13 , wherein the plurality of bandwidth settings comprise a large bandwidth setting and a small bandwidth setting; and the step of generating the control signal according to the first comparison result, the second comparison result and the fourth comparison result comprises:

when the fourth comparison result shows that the average is lower than or equal to the fourth threshold, causing the control signal to select the small bandwidth setting.