Dedicated message matched filter

• US 4,755,983 A
• Filed: 03/01/1983
• Issued: 07/05/1988
• Est. Priority Date: 03/01/1983
• Status: Expired due to Fees

• Current Assignee: Hazeltine Corporation (BAE Systems Plc)
• Original Assignee: Hazeltine Corporation (BAE Systems Plc)
• Inventors: Masak, Raymond J., Torre, Frank M.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Scutch, III, Frank M.
• Application Number:
  US06/471,549
• Time in Patent Office: 1,953 Days
• Field of Search: 370/6, 370/19, 455/63, 455/303, 375/1, 375/96
• US Class Current: 375/152
• CPC Class Codes: H04B 1/7093 Matched filter type

Abstract

In order to recover the original audio modulation samples when using a continuous code change, sampled data, spread spectrum waveform structure, a dedicated message matched filter is used to process data from multiple emitters within the same range interval. The dedicated message matched filter is matched to an incoming signal only at the precise time of the message epoch. The matched filter coding corresponding to the arrival time of message epochs as derived from synchronization acquisition circuitry is rapidly switched so that one dedicated message matched filter can be used to process data from multiple users simultaneously.

Claims

1. An apparatus for detecting information encoded in a spread spectrum waveform comprising:

(a) means having a waveform output for supplying the encoded, spread spectrum waveform;

(b) first means having an input connected to the waveform output for determining the starting point of the particular code sequence of the spread spectrum waveform provided by the supplying means and having code output providing a signal corresponding to the determined code;

(c) a matched filter having a filter input connected to the waveform output to which the waveform is applied, a control input responsive to the first means for determining the code to which the filter is matched, the control input being connected to the code output, and an output providing continuous wave signals corresponding to the waveform; and

(d) second means for demultiplexing and detecting the information in the continuous wave signal.

2. The apparatus of claim 1 wherein said matched filter comprises a tapped delay line having an input for receiving the waveform connected to the waveform output and an output providing a delayed signal corresponding to the waveform;

and

programmable tap weights having inputs for receiving the delayed signal and connected to the delay line output, a control input connected to the control output for receiving the one particular code signal representative of the one particular code of the waveform and an output providing continuous wave signals corresponding to the delayed signal, said tap weights set in accordance with the code signal received by the control input from the code input.

3. The apparatus of claim 2 wherein said first means comprises code select control means for determining the start of each coded waveform message, said code select control means having an input corresponding to the first means input and having an output, and code storage means supplying the code of a particular message to the control input in response to the code select control means, said code storage means having an input connected to the code select control means output and having an output corresponding to the code output.

4. The apparatus of claim 3 wherein said demultiplexer has an input connected to the matched filter output, a plurality of outputs for supplying the continuous wave signals and a control input for controlling the switching of signals between the demultiplexer input and a selected demultiplexer output, said control input connected to the coded select control means output, said demultiplexer being responsive to the first means.