Adaptive envelope extracting apparatus, signal decoding apparatus and short-distance contactless communication apparatus applying the adaptive envelope extracting apparatus, and method thereof

1. A signal decoding apparatus, comprising:

an envelope extracting apparatus, arranged to extract an envelope signal of a received modulation signal, and to generate a clock signal of the received modulation signal;

a phase-locked loop, arranged to receive the clock signal and the envelope signal as inputs directly from the envelope extracting apparatus and generate a continuous clock signal based on the clock signal and the envelope signal; and

a decoding device, arranged to generate digital output data according to the envelope signal and the continuous clock signal.

2. The signal decoding apparatus of claim 1 , wherein when the envelope extracting apparatus outputs a falling edge of the envelope signal, the phase-locked loop keeps the continuous clock signal oscillating under a latest oscillating frequency of the continuous clock signal.

3. The signal decoding apparatus of claim 1 , wherein when the envelope extracting apparatus outputs a rising edge of the envelope signal, the phase-locked loop uses the clock signal as a reference clock signal to generate the continuous clock signal.

4. The signal decoding apparatus of claim 1 , wherein the continuous clock signal is arranged to control the decoding device to count for the number of bit 0 in a predetermined time interval of the envelope signal to determine digital data of the envelope signal in the predetermined time interval.

5. The signal decoding apparatus of claim 1 , wherein the envelope extracting apparatus comprises:

a clock extracting device, arranged to extract the clock signal of the received modulation signal according to a first biasing voltage; and

an edge detecting device, arranged to generate a detecting signal to indicate the envelope edge of the received modulation signal according to a delayed clock signal of the clock signal and a second biasing voltage.

6. The signal decoding apparatus of claim 5 , further comprising:

a determining device, arranged to determine a delay time and an offset voltage according to the received modulation signal;

wherein the delayed clock signal is generated by delaying the clock signal by the delay time, and the second biasing voltage is generated by offsetting the first biasing voltage by the offset voltage.

7. A signal decoding method, comprising:

using an envelope extracting apparatus, extracting an envelope signal of a received modulation signal, and generating a clock signal of the received modulation signal;

using a phase-locked loop, generating a continuous clock signal based on the clock signal and the envelope signal received as inputs to the phase-locked loop directly from the envelope extracting apparatus; and

generating a digital output data according to the envelope signal and the continuous clock signal.

8. The signal decoding method of claim 7 , wherein when a falling edge of the envelope signal is outputted, the continuous clock signal is kept oscillating at a latest oscillating frequency of the continuous clock signal.

9. The signal decoding method of claim 7 , wherein when a rising edge of the envelope signal is outputted, the clock signal is used as a reference clock signal to generate the continuous clock signal.

10. The signal decoding method of claim 7 , wherein the continuous clock signal is arranged to count for the number of bit 0 in a predetermined time interval of the envelope signal to determine digital data of the envelope signal in the predetermined time interval.

11. The signal decoding method of claim 7 , wherein the step of extracting the envelope signal of the received modulation signal, and generating the clock signal of the received modulation signal comprises:

extracting the clock signal of the received modulation signal according to a first biasing voltage; and

generating a detecting signal to indicate the envelope edge of the received modulation signal according to a delayed clock signal of the clock signal and a second biasing voltage.

12. The signal decoding method of claim 11 , further comprising:

determining a delay time and an offset voltage according to the received modulation signal;

wherein the delayed clock signal is generated by delaying the clock signal by the delay time, and the second biasing voltage is generated by offsetting the first biasing voltage by the offset voltage.