Wireless alarm system

• US 5,095,493 A
• Filed: 08/20/1990
• Issued: 03/10/1992
• Est. Priority Date: 11/02/1988
• Status: Expired due to Term

• Current Assignee: NorthPeak Wireless, LLC
• Original Assignee: Axonn LLC (Globalstar Incorporated)
• Inventors: Rouquette, Robert E., Sanderford, H. Britton Jr., Arthur, James D.
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US07/569,682
• Time in Patent Office: 568 Days
• Field of Search: 375/1, 380/34, 371/65
• US Class Current: 375/130
• CPC Class Codes: G08B 25/10 using wireless transmission systems G08B25/009 takes precedence
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/70756 Jumping within the code, i.e. masking or slewing H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/70757 with increased resolution, i.e. higher than half a chip H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A wireless alarm system using spread spectrum transmitters, fast frequency shift keying, spread spectrum receivers and computer with a display. The spread spectrum transmitter includes an oscillator coupled to a microprocessor with chip code generation means, preamble register, address register and data register. The spread spectrum receiver acquires synchronization of the spread spectrum signal using a microprocessor coupled to the quieting, signal strength or baseband output of the receiver, with a two step algorithm. The steps comprise achieving a coarse lock and a fine lock to the spread spectrum signal.

Claims

1. An apparatus for achieving spread spectrum chip code synchronization using a two step algorithm in a processor coupled to a receiver having an output, comprising:

means coupled to the output of said receiver for correlating a first signal from the output of said receiver within one chip of said spread spectrum chip code by comparing the first signal to an adaptive average to determine whether the first signal achieves coarse correlation; and

means coupled to the output of said receiver for correlating a second signal, in response to the first signal achieving coarse correlation, from the output of said receiver within a portion of one chip of said spread spectrum chip code by comparing the second signal to the adaptive average to determine whether the second signal achieves coarse correlation.

2. The apparatus as set forth in claim 1 further including means coupled to said correlating means for computing the adaptive average, in response to the first signal not exceeding the preset margin, for adding the first signal to the previously computed adaptive average.

3. A spread spectrum chip code synchronization method using a two step algorithm in a processor coupled to a receiver having an output, comprising the steps, performed by said processor, of:

correlating a first signal from the output of said receiver within one chip of said spread spectrum chip code by comparing the first signal to an adaptive average to determine whether the first signal exceeds the preset margin;

computing the adaptive average, in response to the first signal not exceeding the preset margin, by adding the first signal to the previously computed adaptive average; and

correlating a second signal, in response to the first signal exceeding the preset margin, from the output of said receiver within a portion of one chip of said spread spectrum chip code by comparing the second signal to the adaptive average to determine whether the second signal exceeds the preset margin.

4. A method of using a processor for synchronizing the timing acquisition of a spread spectrum signal received by a receiver, the spread spectrum signal having a plurality of information bits with each information bit including a plurality of chips from a spread spectrum chip code, comprising the steps, performed by said processor, of:

sampling and digitizing a first signal at the end of one information bit time from the output of said receiver to generate a first data signal;

comparing the first data signal during the one information bit time to an adaptive average to determine whether coarse correlation has been achieved;

computing the adaptive average by adding a first portion of the first data signal to a second portion of previously computed adaptive average in response to tee first data signal not achieving coarse correlation;

shifting a chip code phase shifter by a third portion of one information bit time in response to the first data signal achieving coarse correlation;

sampling and digitizing a second signal from the output of said receiver to generate a second data signal;

comparing the second data signal during one information bit time to the adaptive average to determine whether fine correlation has been achieved;

shifting a chip code phase shifter by a fourth portion of one information bit time in response to the second data signal not achieving fine correlation; and

initiating a data capture algorithm in response to the second data signal achieving fine correlation.

5. A method of using a process for synchronizing timing acquisition of a spread spectrum signal received by a receiver, the spread spectrum signal having a plurality of information bits with each information bit including a plurality of chips from a spread spectrum chip code, comprising the steps, performed by said processor, of:

sampling and digitizing a first signal at the end of one information bit time from the output of said receiver to generate a first data signal;

comparing the first data signal during the one information bit time to an adaptive average to determine whether coarse correlation has been achieved;

computing the adaptive average by adding a first portion of the first data signal to a second portion of previously computed adaptive average in response to the first data signal not achieving coarse correlation; and

initiating a data capture algorithm in response to the second data signal achieving fine correlation.