High dynamic range receiver

Details High dynamic range receiver High dynamic range receiver

2002-06-04

2004-03-16

Pyo, Kevin (Department: 2878)

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

C250S2140LS, C330S278000

Reexamination Certificate

active

06707025

ABSTRACT:

BACKGROUND OF THE INVENTION
Many optical and electrical systems include high dynamic range receivers that detect and process signals having power levels that vary over a wide range. A high dynamic range receiver has enough sensitivity to detect and process an applied signal having a low power level, but avoids becoming overloaded when the applied signal has a high power level. A typical prior art receiver, shown in
FIG. 1
, includes a switched-gain amplifier having an input that is connected to a single terminal of a detector that receives an applied signal. The switched-gain amplifier has two alternative gain settings—a high gain setting for when the applied signal has a low power level, and a low gain setting for when the applied signal has a high power level. The switched-gain amplifier includes either a mechanical relay or a solid state switch to alternatively select gain-setting resistors in a feedback path of the switched-gain amplifier. A solid state switch has the benefit of fast switching of the gain-setting resistors, but has the disadvantages of introducing leakage current and noise in the feedback path of the switched-gain amplifier, degrading the low-level sensitivity of the receiver. A mechanical relay has the benefits of low noise and low leakage, but provides for slow switching of the gain-setting resistors, which results in switching delay periods during which the receiver is inoperable for detection and processing of the applied signals. Accordingly, there is a need for a high dynamic range receiver that avoids the switching of gain-setting resistors in an amplifier feedback path and that overcomes the shortcomings of this type of prior art receiver.
SUMMARY OF THE INVENTION
A high dynamic range receiver constructed according to the embodiments of the present invention has enough sensitivity to detect and process applied signals having low power, avoids becoming overloaded when the applied signal has high power, and does not rely on switching in the feedback path of an amplifier. The receiver includes a detector or other current source that produces a current at a pair of terminals. A first gain element, implemented as a current-to-voltage converter for example, is coupled to the first terminal, receiving the current and generating a first output signal corresponding to the current. A second gain element, implemented as a current-to-voltage converter for example, is coupled to the second terminal, receiving the current and generating a second output signal corresponding to the received current. A switch selectively couples the first output signal or the second output signal to a port based on a comparison of at least one of the first output signal and the second output signal to a threshold.


REFERENCES:
patent: 5138149 (1992-08-01), Cadet et al.
patent: 5471049 (1995-11-01), Cain
patent: 5786730 (1998-07-01), Hadley

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