Detector for detecting information carried by a signal having a sawtooth-like shape

1. A detector for detecting information carried by a signal having a sawtooth-like shape, the detector comprising:

a filter for receiving a wobble signal and filtering the wobble signal to generate a filtered signal;

a comparator for comparing the wobble signal with the filtered signal and generating a compared signal; and

a detecting unit for receiving the compared signal and generating a bit signal according to a duty cycle of the compared signal;

wherein the bit signal is set to a first value when the duty cycle of the compared signal is greater than a predetermined value, and the bit signal is set to a second value when the duty cycle of the compared signal is smaller than the predetermined value.

2. The detector according to claim 1 , wherein the filter is a first low-pass filter with a 3 dB frequency roughly close to an inverse of a time period during which the wobble signal carries a bit information.

3. The detector according to claim 1 , wherein the predetermined value is 50%.

4. The detector according to claim 1 , wherein the detecting unit comprises:

an averaging unit for receiving the compared signal and generating an average signal; and

a level detecting unit for receiving the average signal and generating the bit signal;

wherein the bit signal is set to the first value when the level of the average signal is greater than a reference voltage, and the bit signal is set to the second value when the level of the average signal is smaller than the reference voltage.

5. The detector according to claim 4 , wherein the first value represents a logic one and the second value represents a logic zero.

6. The detector according to claim 4 , wherein the averaging unit is a second low pass filter.