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Digitally-controlled pyroelectric signal sampling circuit

  • US 7,019,295 B2
  • Filed: 09/05/2003
  • Issued: 03/28/2006
  • Est. Priority Date: 12/25/2002
  • Status: Expired due to Fees
First Claim
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1. A digitally-controlled pyroelectric signal sampling circuit, which comprises:

  • a trigger-signal generating unit for generating a trigger signal, a first sampling signal, and a second sampling signal, which are substantially fixed in frequencies and timings irrespective of temperature changes in the ambient environment;

    a light source module, which is triggered by the trigger signal from the trigger-signal generating unit to emit an alternating light beam;

    a pyroelectric sensor module for sensing the emitted alternating light beam from the light source module to thereby generate an alternating pyroelectric signal;

    a first sample-and-hold circuit, which is clocked by the first sampling signal generated by the trigger-signal generating unit, to sample each upper peak of the alternating pyroelectric signal from the pyroelectric sensor module and thereby generate a first sampled signal;

    a second sample-and-hold circuit, which is clocked by the second sampling signal generated by the trigger-signal generating unit, to sample each bottom peak of the alternating pyroelectric signal from the pyroelectric sensor module and thereby generate a second sampled signal; and

    a subtraction circuit for performing a subtraction operation on the first sampled signal generated by the first sample-and-hold circuit and the second sampled signal generated by the second sample-and-hold circuit to thereby obtain a difference signal;

    wherein the difference signal from the subtraction circuit is substantially a direct current (DC) output and serves as an output of the digitally-controlled pyroelectric signal sampling circuit.

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