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Adaptive frequency touchscreen controller using intermediate-frequency signal processing

  • US 6,396,484 B1
  • Filed: 09/29/1999
  • Issued: 05/28/2002
  • Est. Priority Date: 09/29/1999
  • Status: Expired due to Fees
First Claim
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1. A touchscreen system, comprising:

  • a touchscreen substrate, said substrate capable of propagating acoustic waves;

    at least one transmitting transducer coupled to said substrate, said transmitting transducer initiating an acoustic wave of a first burst length in response to an input signal;

    a reflective array pattern comprised of a plurality of acoustic wave reflectors coupled to said substrate, said reflective array stretching said first burst length to form a second burst length acoustic wave;

    at least one receiving transducer coupled to said substrate, said receiving transducer receiving said acoustic wave of said second burst length; and

    an adaptive controller coupled to said at least one transmitting transducer and to said at least one receiving transducer, said adaptive controller comprising;

    a reference oscillator outputting a frequency;

    a first mixer coupled to said at least one receiving transducer and to said reference oscillator, said first mixer outputting a first mixer output signal;

    an IF bandpass filter coupled to said first mixer;

    a feedback loop circuit coupled to said IF filter and to said reference oscillator, said feedback loop circuit modifying said reference oscillator frequency;

    a second mixer coupled to said reference oscillator;

    an IF oscillator coupled to said second mixer;

    a microprocessor; and

    a burst circuit coupled to said second mixer, said microprocessor, and said at least one transmitting transducer, said burst circuit outputting said input signal to said at least one transmitting transducer.

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