Wide dynamic range optical receiver
First Claim
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1. An arrangement for discriminating a high frequency, incident light radiation information analog signal of variable amplitude from a low frequency background analog signal over a wide dynamic range in a receiver, comprising:
- optical sensor means sensitive to both the information and the background analog signals, for generating a sensing analog signal containing both the information and the background analog signals;
differential amplifier means having first and second inputs, a gain and an output;
low pass filter means having a low frequency passband;
means for directly connecting the sensing analog signal to the first input of the differential amplifier means and to the low pass filter means, andmeans for directly connecting the low pass filter means to the second input of the differential amplifier means;
said low pass filter means being operative for passing only the low frequency background analog signal to the second input of the differential amplifier means; and
said differential amplifier means being operative for subtracting the background analog signal from the sensing analog signal to generate a differential output analog signal whose amplitude is directly proportional to the variable amplitude of the information analog signal, and whose signal-to-noise ratio is high, both said signal-to-noise ratio and said dynamic range increasing in value as the difference between the sensing analog signal and the background analog signal at the inputs of the differential amplifier means increases in value.
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Abstract
Ambient light and temperature fluctuations are suppressed in an optical receiver system by feeding the output of a photodiode directly to one input of a differential amplifier and, via a low pass filter, to another input of the amplifier. Reductions in amplitude in an optical information signal are automatically compensated.
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Citations
13 Claims
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1. An arrangement for discriminating a high frequency, incident light radiation information analog signal of variable amplitude from a low frequency background analog signal over a wide dynamic range in a receiver, comprising:
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optical sensor means sensitive to both the information and the background analog signals, for generating a sensing analog signal containing both the information and the background analog signals; differential amplifier means having first and second inputs, a gain and an output; low pass filter means having a low frequency passband; means for directly connecting the sensing analog signal to the first input of the differential amplifier means and to the low pass filter means, and means for directly connecting the low pass filter means to the second input of the differential amplifier means; said low pass filter means being operative for passing only the low frequency background analog signal to the second input of the differential amplifier means; and said differential amplifier means being operative for subtracting the background analog signal from the sensing analog signal to generate a differential output analog signal whose amplitude is directly proportional to the variable amplitude of the information analog signal, and whose signal-to-noise ratio is high, both said signal-to-noise ratio and said dynamic range increasing in value as the difference between the sensing analog signal and the background analog signal at the inputs of the differential amplifier means increases in value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of discriminating a high frequency, incident light radiation information analog signal of variable amplitude from a low frequency background analog signal over a wide dynamic range in a receiver, comprising the steps of:
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generating an optical sensing analog signal containing both the information and the background analog signals; extracting the background analog signal frown the sensing analog signal by directly connecting the sensing analog signal to a first input of a differential amplifier and also to an input of a low pass filter, and by directly connecting an output of the low pass filter to a second input of the differential amplifier; and subtracting the extracted background analog signal from the sensing analog signal to generate a differential output analog signal whose amplitude is directly proportional to the variable amplitude of the information analog signal, and whose signal-to-noise ratio is high, both said signal-to-noise ratio and said dynamic range increasing in value as the difference between the sensing analog signal and the background analog signal at the inputs of the differential amplifier increases in value. - View Dependent Claims (11, 12)
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13. A system for detecting an object in an area subject to environmental variations, comprising:
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optical sensor means sensitive to high frequency, incident light radiation and to low frequency, ambient light, and for respectively generating information and background analog signals; means for discriminating the information analog signal from the background analog signal, and for attenuating the background analog signal; and means for automatically compensating for a change in amplitude of the information analog signal by generating an adjustable scaled amplitude of the information analog signal, and by comparing the information analog signal against said adjustable scaled amplitude.
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Specification