Burst-mode TIA (trans-impedance amplifier)
View Patent ↗Devices and methods for processing signals using a Burst-Mode TIA that meets EPON and GPON specifications are disclosed herein. A signal provided by a power detector is processed with the appropriate gain by using a gain selector which includes a feedback circuit to choose the gain internally, thereby eliminating the need for an external control. Further embodiments of the invention include power detectors featuring a low-pass filter, a peak detector, and/or an envelope detector. Further embodiments of the invention include a Freeze function circuit for maintaining a current gain. Further embodiments of the invention apply appropriate gains when bursts with substantially different power levels are received consecutively, and prevent the gain from being changed during a burst. In this method, a two-pole low-pass filter with an undamped response function is used.
1. A Trans-Impedance Amplifier (TIA) for processing signals, the TIA comprising:
(a) a TIA core for providing an appropriate gain to a detector output signal;
(b) a coupler for transferring a part of a TIA output signal without introducing distortion or noise;
(c) a power detector for obtaining a desired signal level from said signal part provided by said coupler;
(d) a feedback circuit operative on a gain selector for choosing said appropriate gain internally based on said desired signal level from said power detector;
(e) a gain control for setting said appropriate gain obtained from said gain selector; and
(f) a freeze function circuit for controlling said gain selector.
2. The TIA of claim 1 , wherein said power detector includes a low-pass filter for filtering said signal part provided by said coupler.
3. The TIA of claim 2 , wherein said power detector includes a peak detector for detecting and measuring a peak of said signal part provided by said coupler.
4. The TIA of claim 2 , wherein said power detector includes an envelope detector for detecting and measuring an envelope of said signal part provided by said coupler.
5. The TIA of claim 1 , wherein said gain selector includes a multiplexer for selecting an input signal based on said desired signal level from said power detector.
6. The TIA of claim 5 , wherein said gain selector includes a logic unit for selecting a gain, by said feedback circuit, for both said TIA core and said input signal of said multiplexer.
7. The TIA of claim 1 , wherein said TIA core includes a high-gain amplifier and at least one feedback resistor for setting said appropriate gain.
8. The TIA of claim 7 , wherein said TIA core further includes at least one switch for engaging or disengaging said feedback resistor.
9. The TIA of claim 1 , wherein the TIA operates in a burst mode.
10. The TIA of claim 1 , wherein said freeze function circuit is operative to maintain a current gain of said gain selector.
11. The TIA of claim 1 , wherein said freeze function circuit includes an interface for remotely activating or deactivating said freeze function circuit.
12. The TIA of claim 6 , wherein said freeze function circuit is operative to override said logic unit.
13. A Trans-Impedance Amplifier (TIA) for processing signals comprising:
(a) a TIA core for providing an appropriate gain to a detector output signal;
(b) a coupler for transferring a part of a TIA output signal without introducing distortion or noise;
(c) a power detector for obtaining a desired signal level from said signal part provided by said coupler;
(d) a feedback circuit operative on a gain selector for choosing said appropriate gain internally based on said desired signal level from said power detector; and
(e) a gain control for setting said appropriate gain obtained from said gain selector; and
(f) a freeze function circuit for controlling said gain selector.
14. The TIA of claim 13 , wherein said freeze function circuit is operative to maintain a current gain of said gain selector.
15. The TIA of claim 13 , wherein said freeze function circuit includes a interface for remotely activating or deactivating said freeze function circuit.
16. The TIA of claim 13 , wherein said power detector includes a low-pass filter for filtering said signal part provided by said coupler.
17. The TIA of claim 13 , wherein said power detector includes a peak detector for detecting and measuring a peak of said signal part provided by said coupler.
18. The TIA of claim 13 , wherein said power detector includes an envelope detector for detecting and measuring an envelope of said signal part provided by said coupler.
19. The TIA of claim 13 , wherein said gain selector includes a multiplexer for selecting an input signal based on said desired signal level from said power detector.
20. The TIA of claim 19 , wherein said gain selector includes a logic unit for selecting a gain, by said feedback circuit, for both said TIA core and said input signal of said multiplexer.
21. The TIA of claim 20 , wherein said freeze function circuit is operative to override said logic unit.
22. The TIA of claim 13 , wherein said TIA core includes a high-gain amplifier and at least one feedback resistor for setting said appropriate gain.
23. The TIA of claim 22 , wherein said TIA core further includes at least one switch for engaging or disengaging said feedback resistor.
24. The TIA of claim 13 , wherein the TIA operates in a burst mode.
25. A method for processing a signal using a Trans-Impedance Amplifier (TIA), comprising the steps of:
(a) obtaining a pre-processed signal from a power detector at an input of the TIA;
(b) using a gain selector of the TIA to choose an appropriate nominal gain Gain i ;
(c) setting a nominal input gain G i to a multiplexer of the TIA;
(d) controlling values of each said Gain i and each said G i through a mathematical relation of said Gain i to said G i ; and
(e) regulating said gain selector via a freeze function circuit by maintaining a current gain when said freeze function circuit is activated, thereby providing a desired processing of the signal.
26. The method of claim 25 , wherein said step of controlling values of each said Gain i and each said G i through a mathematical relation of said Gain i to said G i includes prescribing a product of said Gain i and said G i to equal a constant.
27. The method of claim 25 , wherein said step of controlling values of each said Gain i and each said G i through a mathematical relation of said Gain i to said G i includes prescribing a product of said Gain i and said G, to equal an i-dependent nominal constant.
28. The method of claim 25 , performable by the TIA operating in a burst mode.
29. A method for processing signals using a Trans-Impedance Amplifier (TIA), comprising the steps of:
(a) providing a consecutive pair of burst signals from a detector output, said consecutive signals having substantially different power levels;
(b) filtering each said burst signal with a filter, having an under-damped impulse response function to provide an output signal with an appropriate gain amplification; and
(c) using said output signal to obtain an accurate signal peak for each said burst signal, thereby providing a desired processing of said burst signals.
30. The method of claim 29 , wherein said step of filtering includes filtering each said burst signal using a two-pole low-pass filter with a specific response function as follows:
H
(
s
)
=
a
s
+
b
ξ
2
+
2
ξω
n
s
+
s
2
,
where ξ is the damping factor, ω n is the natural frequency, a and b are constants, s is an arbitrary complex variable, and H(s) is the Laplace transform of the response of said detector, which is defined as follows:
H
(
s
)
=
∫
0
∞
ⅇ
-
st
h
(
t
)
ⅆ
t
,
where h(t) is the impule response of said filter.