Ask receiver with signal delay and stretching
First Claim
Patent Images
1. An amplitude-shift keyed (ASK) receiver for receiving ASK modulated signals and detecting ASK modulation formed of pulses representative of one binary digit, comprising:
- means for detecting ASK modulated signals and producing a modulation signal representative of the ASK modulation thereof with pulses representative of said one binary digit;
means for producing a delayed version of the modulation signal;
means for producing a stretched version of the modulation signal wherein trailing edges of pulses decay at a rate selected so that the trailing edges thereof overlap in time the delayed version of the modulation signal; and
means for comparing the delayed version of the modulation signal with the stretched version thereof to produce a high bit level data signal representative of said one binary digit during the time that said delayed version effectively exceeds said stretched version.
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Abstract
An amplitude-shift-keyed (ASK) receiver is described for use in receiving infrared ASK modulated carrier signals wherein a delayed version of a demodulated pulse os compared with a stretched version and a dynamic threshold signal to reproduce binary data pulses. The dynamic threshold signal is further compared with the stretched version to derive an indication of the amplitude of the incident optical carrier. An embodiment illustrating use of the ASK receiver in an infrared communication system is described.
49 Citations
17 Claims
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1. An amplitude-shift keyed (ASK) receiver for receiving ASK modulated signals and detecting ASK modulation formed of pulses representative of one binary digit, comprising:
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means for detecting ASK modulated signals and producing a modulation signal representative of the ASK modulation thereof with pulses representative of said one binary digit; means for producing a delayed version of the modulation signal; means for producing a stretched version of the modulation signal wherein trailing edges of pulses decay at a rate selected so that the trailing edges thereof overlap in time the delayed version of the modulation signal; and means for comparing the delayed version of the modulation signal with the stretched version thereof to produce a high bit level data signal representative of said one binary digit during the time that said delayed version effectively exceeds said stretched version. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In an ASK receiver for receiving ASK modulated carrier signals and detecting ASK modulation formed of pulses representative of one binary digit and wherein the incident carrier signals are amplified, passed through a bandpass filter, and applied to a logarithmic amplifier and detector, the output of which presents an ASK modulation signal, the improvement comprising:
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a delay circuit, responsive to the ASK modulation signal and having an output; a pulse stretcher responsive to the ASK modulation signal and having an output; a threshold generator responsive to the ASK modulation signal and having an output; first comparator means for producing an output data pulse during the time that the output from the delay circuit exceeds the output from the pulse stretcher; and second comparator means for producing an enabling signal during the time that the output from the delay circuit exceeds the output from the threshold generator. - View Dependent Claims (10, 11, 12, 13)
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14. An amplitude-shift-keyed (ASK) infrared receiver for receiving ASK modulated infrared carrier signals and detecting ASK modulation formed of pulses representative of one binary digit and an absence of pulses representative of the other binary digit, comprising:
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means for detecting infrared ASK modulated carrier signals and producing a modulation signal representative of the ASK modulation thereof with pulses representative of said one binary digit; means for producing a delayed version of the modulation signal; means for producing a stretched version of the modulation signal wherein trailing edges of pulses decay at a rate selected so that the trailing edges thereof overlap in time the delayed version of the modulation signal; means for comparing the delayed version of the modulation signal with the stretched version thereof to produce a high bit level data signal representative of said one binary digit during the time that said delayed version effectively exceeds said stretched version; means for generating a threshold signal whose amplitude is a function of the noise level in the modulation signal; and means for comparing the threshold signal with the delayed version of the modulation signal for enabling generation of a bit signal indicative of said one binary digit.
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15. An amplitude-shift-keyed (ASK) infrared communication system wherein a plurality of ASK transmitters send repeated bursts of information, which includes identification codes associated with respective transmitters, and is carried by ASK modulated infrared carrier signals which are incident on one or more ASK infrared receivers for demodulation by the receivers so that they can transmit binary data signals, represented by the ASK modulation, to a base station having data representative of locations of the infrared receivers, comprising:
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a plurality of ASK infrared receiver means for detecting ASK modulated carrier signals and producing data signals representative of the ASK modulation of infrared carrier signals from the infrared transmitters; said plurality of receiver means further each including; means for deriving, from incident ASK modulated infrared carrier signals a level signal indicative of the intensity of incident infrared carrier signals; and means for transmitting said data signals, said level signal and said identification code to said base station; wherein said base station includes; means for comparing level signals representative of infrared carrier levels from the same infrared transmitter but at different infrared receivers and producing an indication representative of the approximate location of the transmitter associated with the compared level signals. - View Dependent Claims (16)
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17. An amplitude-shift-keyed (ASK) infrared communication system wherein a plurality of ASK transmitters send repeated bursts of information, which includes identification codes associated with respective transmitters, and is carried by ASK modulated infrared carrier signals which are incident on one or more ASK infrared receivers for demodulation by the receivers so that they can transmit binary data signals, represented by the ASK modulation, to a base station having data representative of locations of the infrared receivers, comprising:
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a plurality of ASK infrared receiver means for detecting ASK modulated carrier signals and producing data signals representative of the ASK modulation of infrared carrier signals from the infrared transmitters; said plurality of receiver means further each including; means for deriving, from incident ASK modulated infrared carrier signals a level signal indicative of the intensity of incident infrared carrier signals; and means for producing an identification code representative of the identification of the receiver means; and means for transmitting said data signals, said level signal and said identification code to said base station; wherein said base station includes; means for comparing level signals representative of infrared carrier levels from the same infrared transmitter but at different infrared receivers and producing an indication representative of the approximate location of the transmitter associated with the compared level signals.
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Specification