CODE DIVISION MULTIPLEX SYSTEM

• US 3,789,149 A
• Filed: 06/09/1972
• Issued: 01/29/1974
• Est. Priority Date: 07/30/1969
• Status: Expired due to Term

• Current Assignee: Adrian Percy Clark
• Original Assignee: Adrian Percy Clark
• Inventors: Clark, Adrian Percy
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Stewart, David L.
• Application Number:
  US05/261,454
• Time in Patent Office: 599 Days
• Field of Search: 179/15BC,15BW,15FS,15FO,1.5A 325/320,321,42,65,473 333/18R,28R
• US Class Current: 370/342
• CPC Class Codes: H04L 5/02 Channels characterised by the type of signal

Abstract

In digital transmission systems for use over H.F. radio links, the effects of multi-path propagation can be reduced by limiting the minimum duration of a signal element. The invention is concerned with a system for use when a transmission rate much greater than that which can be accommodated on a single channel if this minimum element duration is maintained. A code-division multiplex system is used. A first plurality of multi-level signals each represents a plurality of elements of the incoming signal. An orthogonal transformation matrix produces a second plurality of multi-level signals, the level of each of which is dependent on all said first plurality of multi-level signals. A time-division-multiplex signal is then produced from said second plurality of multi-level signals and used to modulate a carrier signal.

Claims

1. For use in a code division multiplex electrical signalling system in which digital signals are transmitted at a lower element rate than that of the signals to be transmitted, a receiver comprising sampling means for sampling the received signal once during each element thereof to produce a first plurality of multi-level signals, matrix means comprising at least one orthogonal transformation matrix responsive to said sampling means for producing a second plurality of multi-level signals from said first plurality thereof and decoding means responsive to said matrix means for producing a plurality of signal elements from each multi-level signal of said second plurality thereof, wherein said decoding means comprises polarity detection and level detection means adapted to produce a respective first binary signal and a respective second binary signal for each multi-level signal of said second plurality thereof, each of said first binary signals having the same polarity as the corresponding multilevel signal and each of said second binary signals having a first polarity when the corresponding multi-level signal has a magnitude greater than a predetermined level and a second polarity when said corresponding multi-level signal has a polarity less than said predetermined level.

2. A receiver as claimed in claim 1, including demodulation means comprising a phase-locked oscillator and a switched inverter.

3. A receiver as claimed in claim 1, in which said matrix means comprises a single transformation matrix.

4. A receiver as claimed in claim 1, in which said matrix means comprises first and second transformation matrices, the first transformation matrix being arranged to be responsive to signals modulating a first carrier signal and the second transformation matrix being arranged to be responsive to signals transmitted by a second carrier signal having the same frequency as the first carrier signal but being in phase-quadrature thereto.