Reciprocal mode saw correlator method and apparatus

• US 5,355,389 A
• Filed: 01/13/1993
• Issued: 10/11/1994
• Est. Priority Date: 01/13/1993
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Omnipoint Corp. (Deutsche Telekom AG)
• Inventors: Vanderpool, Jeffrey S., O'Clock, George D.
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US08/004,071
• Time in Patent Office: 636 Days
• Field of Search: 364/728.06, 364/824, 375/1, 375/96
• US Class Current: 375/151
• CPC Class Codes: G06F 17/15 Correlation function computation including computation of convolution operations arithmetic circuits for sum of products per se, e.g. multiply-accumulators G06F7/5443; digital filters, e.g. FIR, IIR, adaptive filters H03H17/00
• CPC Class Codes: G06G 7/195 using electro- acoustic elements
• CPC Class Codes: H04B 1/70712 with demodulation by means of convolvers, e.g. of the SAW type SAW convolvers in general G06G7/195
• CPC Class Codes: H04B 1/709 Correlator structure

Abstract

A surface-acoustic-wave correlator for decoding a spread-spectrum signal having a data signal modulated with a plurality of chip sequences and reciprocal-chip sequences. A tapped-delay-line has a plurality of taps defining a tapped-delay-line structure matched to the chip sequence. In response to a plurality of first chips and second chips embedded in the spread-spectrum signal, the tapped-delay line generates TDL-chip sequences and inverse-TDL-chip sequences. A first transducer is acoustically coupled to the tapped-delay-line. In response to the spread-spectrum signal modulated by the chip sequence, the first transducer correlates a first group of the plurality of TDL-chip sequences and inverse-TDL-chip sequences and outputs a first correlation pulse. A second transducer is acoustically coupled to the tapped-delay-line. In response to the spread-spectrum signal modulated by the reciprocal-chip sequence, the second transducer correlates a second group of the plurality of TDL-chip sequences and inverse-TDL-chip sequences and outputs a second correlation pulse. In response to the first'"'"' correlation pulse and the second correlation pulse, a decision circuit outputs the first bit and the second bit, respectively.

Claims

1. A correlator for decoding a spread-spectrum signal having a data signal modulated with a plurality of chip sequences and reciprocal-chip sequences, comprising

a tapped-delay-line having a plurality of taps defining a tapped-delay-line structure matched to the chip sequence, responsive to a plurality of first chips and second chips embedded in the spread-spectrum signal, and capable of generating a plurality of first chip sequences and a plurality of second chip sequences, said second chip sequences being reciprocal forms of said first chip sequences, respectively;

a first transducer, responsive to the spread-spectrum signal modulated by the chip sequence, capable of correlating a first group of the plurality of first chip sequences and second chip sequences generated by said tapped-delay-line and capable of outputting a first correlation pulse;

a second transducer, responsive to the spread-spectrum signal modulated by the reciprocal-chip sequence, capable of correlating a second group of the plurality of first chip sequences and second chip sequences generated by said tapped-delay-line and capable of outputting a second correlation pulse; and

a decision circuit responsive to the first correlation pulse and the second correlation pulse.