Wireless alarm system

CAFC
  • US 4,977,577 A
  • Filed: 11/02/1988
  • Issued: 12/11/1990
  • Est. Priority Date: 11/02/1988
  • Status: Expired due to Term
First Claim
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1. A spread spectrum transmitter comprising:

  • modulation means having an enable input and a moduation input, for modulating an RF signal with spread spectrum for reducing interference and providing code division multiple access in response to a modulating voltage being applied at the modulation input and an enable signal being applied at the enable input;

    an RF power amplifier coupled to said modulating means, and having a keying input;

    a bandpass filter coupled to said RF power amplifier;

    an antenna coupled to said bandpass filter;

    a microprocessor coupled to said modulation means and said RF power amplifier for controlling said modulation means and said RF power amplifier, respectively, said microprocessor including,chip-code-generation means coupled to the modulation input of said modulation means for storing a spread spectrum chip code, and outputting, during a transmitting interval, the spread spectrum chip code as a modulating voltage to the modulation input of said modulating means;

    a preamble register coupled to the modulation input of said modulation means for storing a preamble, and outputting, during the transmitting interval, the preamble as a modulating voltage to the modulation input of said modulation means;

    an address register coupled to the modulation input of said said modulation means through said preamble register for storing a device address and a type code, and outputting, during the transmitting interval, the device address and type code as a modulating voltage to the modulation input of said modulation means;

    a data register coupled to a data input and to the modulation input of said modulation means through said preamble register and said address register, for storing information data received from the data input, and outputting, during the transmitting interval, the information data as a modulating voltage to the modulation input of said modulation means;

    error detection means coupled to said data register for generating error detection data from the preamble, device address and type code and the information data, wherein said error detection means is initialized with a value unique to each installation using said spread spectrum transmitter;

    wherein said preamble register, said address register, said data register and said error detection means sequentially output the preamble, device address and type code, error detection data and information data to the modulation input and the spread spectrum chip code from said chip code generating means spreads the preamble, device address and type code, error detection data and information data to generate the spread spectrum of the RF signal, and wherein the preamble provides acquisition for spread spectrum synchronization for demodulating the spread spectrum of the RF signal;

    a timing circuit coupled to the enable input of said modulation means and to the keying input of said RF power amplifier for enabling said modulation means and said RF power amplifier, by outputting an enable signal to the enable input of said modulation means and a keying signal to the keying input of said RF power amplifier, respectively, during the transmitting interval; and

    a pseudorandom sequence generator coupled to said timing circuit for generating a random number for modifying the timing duration between each transmitting interval.

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