Noise discriminator for passive optical network burst mode receiver
View Patent ↗A noise discriminator circuit and a noise discrimination method in a burst mode receiver is configured to determine the validity of an incoming burst signal by analyzing the timing of the signal edges of incoming signal to look for a time duration conforming to the preamble data bits of a valid burst signal. In one embodiment, the noise discriminator circuit and method analyze the time duration between signal edges of the same pulse of an incoming signal. In another embodiment, the noise discriminator circuit and method analyze the time duration between a first set of pulses of an incoming signal and the time duration between signal edges of a second set of pulses of the incoming signal. When the time durations are within a given time range relating to a predetermined timing separation of a valid burst signal, the incoming signal is validated as a valid burst signal.
1. A method in a burst mode receiver to determine the validity of an incoming burst signal, comprising:
receiving pulses of an input signal;
assessing a time duration between a first signal edge and a second signal edge of the same pulse or of different pulses;
determining if the time duration is within a time range of a predetermined timing separation of a valid burst signal; and
in response to the time duration being within the time range of the predetermined timing separation, generating a signal to indicate that the input signal is a valid burst signal.
2. The method of claim 1 , wherein the signal edges of the pulses comprise rising edges, falling edges, or a combination of rising and falling edges.
3. The method of claim 1 , wherein the assessing and the determining steps comprise:
assessing the time duration between the first signal edge and the second signal edge of the same pulse; and
determining if the time duration between the first signal edge and the second signal edge of the same pulse is within a time range of a predetermined pulse width of a valid burst signal.
4. The method of claim 1 , wherein the assessing and the determining steps comprise:
assessing the time duration between the first signal edge being a signal edge of one pulse and the second signal edge being a signal edge of another pulse; and
determining if the time duration between the first signal edge and the second signal edge is within a time range of a predetermined timing separation of a valid burst signal.
5. The method of claim 4 , wherein the assessing and the determining steps comprise:
assessing the time duration between the first signal edge being a signal edge of a first pulse and the second signal edge being a signal edge of a second pulse consecutive to the first pulse of the input signal; and
determining if the time duration between the first signal edge of the first pulse and the second signal edge of the second pulse is within the time range of a predetermined timing separation of a valid burst signal.
6. The method of claim 1 , wherein the assessing and the determining steps comprise:
assessing a first time duration associated with signal edges of a first pulse or a first set of pulses of the input signal; and
determining if the first time duration is within the time range of a predetermined timing separation of a valid burst signal.
7. The method of claim 6 , further comprising:
assessing a second time duration associated with signal edges of a second pulse or a second set of pulses of the input signal; and
determining if the second time duration is within the time range of a predetermined timing separation of a valid burst signal,
wherein the signal to indicate that the input signal is a valid burst signal is generated when the first time duration and the second time duration are both within the time range of a predetermined timing separation of a valid burst signal.
8. The method of claim 7 , wherein the first pulse and the second pulse comprise consecutive pulses and the first set of pulses and the second set of pulses comprise consecutive pulses of the input signal.
9. The method of claim 8 , wherein the predetermined timing separation of a valid burst signal comprises the predetermined timing separation of the signal edges in the preamble data bits of the burst signal.
10. The method of claim 9 , wherein the predetermined timing separation of the signal edges in the preamble data bits of the burst signal comprises a timing separation being twice the period of the data rate of the burst signal.
11. The method of claim 1 , further comprising
determining if a signal level of the input signal is above a signal threshold; and
generating a signal to indicate that the input signal is a valid burst signal in response to the time duration being within the time range of the predetermined timing separation and the signal level being above a signal threshold.
12. A limiting amplifier for a burst mode receiver, comprising:
an amplifier configured to receive and amplify an input signal representative of an incoming burst signal;
a buffer configured to receive the amplified input signal and to generate an output signal;
a noise discriminator circuit configured to receive the amplified input signal, to assess a time duration between a first signal edge and a second signal edge of the same pulse or of different pulses, and to generate a valid output signal in response to the time duration being within a time range of a predetermined timing separation of a valid burst signal; and
a signal detect generator circuit configured to generate a signal detect signal in response to the valid output signal being asserted.
13. The limiting amplifier of claim 12 , further comprising:
a signal level detector circuit configured to receive the amplified input signal and to generate a detected data signal in response to the amplified input signal having a signal amplitude greater than a signal threshold,
wherein the signal detect generator circuit is configured to generate a signal detect signal in response to both the detected data signal being asserted and the valid output signal being asserted.
14. The limiting amplifier of claim 13 , wherein the noise discriminator circuit is configured to receive either the amplified input signal or the detected data signal and to generate the valid output signal in response to the time duration between a first signal edge and a second signal edge of the same pulse or of different pulses of either the amplified input signal or the detected data signal being within the time range of a predetermined timing separation of a valid burst signal.
15. The limiting amplifier of claim 12 , wherein the signal edges of the pulses comprise rising edges, falling edges, or a combination of rising and falling edges.
16. The limiting amplifier of claim 12 , wherein the noise discriminator circuit is configured to generate the valid output signal in response to a time duration between a signal edge of a first pulse and a signal edge of a second pulse consecutive to the first pulse of the input signal being within the time range of a predetermined timing separation of a valid burst signal.
17. The limiting amplifier of claim 12 , wherein the noise discriminator circuit is configured to generate the valid output signal in response to a first time duration associated with signal edges of a first pulse or a first set of pulses of the input signal being within the time range of a predetermined timing separation of a valid burst signal.
18. The limiting amplifier of claim 17 , wherein the noise discriminator circuit is configured to generate the valid output signal in response to the first time duration associated with signal edges of the first pulse or the first set of pulses of the input signal being within the time range of a predetermined timing separation of a valid burst signal and in response to a second time duration associated with signal edges of a second pulse or a second set of pulses of the input signal being within the time range of a predetermined timing separation of a valid burst signal.
19. The limiting amplifier of claim 18 , wherein the first pulse and the second pulse comprise consecutive pulses and the first set of pulses and the second set of pulses comprise consecutive pulses of the input signal.
20. The limiting amplifier of claim 19 , wherein the predetermined timing separation of a valid burst signal comprises the predetermined timing separation of the signal edges in the preamble data bits of the burst signal.
21. The limiting amplifier of claim 20 , wherein the predetermined timing separation of the signal edges in the preamble data bits of the burst signal comprises a timing separation being twice the period of the data rate of the burst signal.