US 4,964,138 A · Differential correlator for spread spectrum communication system

Abstract

A spread spectrum communications system includes an encoder for differentially encoding a spread spectrum spreading code sequence in accordance with an input data signal. Each chip of the spreading code sequence is inverted, or not inverted, relative to the polarity of a corresponding chip of the spreading code sequence a fixed time delay previously, depending on whether the input data is a logic one or zero, respectively. At the receiver, the data is recovered in a differential data decoder wherein the presently received chip of the spread spectrum signal and a corresponding previously received chip of spread spectrum signal, received a fixed time delay previously, are compared one chip at a time. Since it is the spreading code sequence that is differentially encoded and differentially decoded, there is no need for a synchronized code sequence generator at the receiver, and data synchronization is achieved after one cycle time of the received spread spectrum spreading code sequence has elapsed.

Claims9

Dependent claims

In a spread spectrum communication system including a spread spectrum signal having a spreading code sequence differentially encoded in accordance with an input data signal, a data correlator comprising:

an input terminal for receiving said spread spectrum signal;
an output terminal;
differential decoding means, coupled to said input terminal for determining whether at least one chip of the presently received spread spectrum spreading code sequence at said input terminal and at least one chip of a previously received spread spectrum spreading code sequence are substantially equal;
said differential decoding means further providing a first logic level output at said output terminal when said chip of said presently received spread spectrum spreading code sequence and said chip of said previously received spread spectrum spreading code sequence are substantially equal;
and
said differential decoding means further providing a second logic level output at said output terminal when said chip of said presently received spread spectrum spreading code sequence and of said chip of
said previously received spread spectrum spreading code sequence are substantially not equal.

4 more elements

an input terminal for receiving said spread spectrum signal;
an output terminal;
differential decoding means, coupled to said input terminal for determining whether at least one chip of the presently received spread spectrum spreading code sequence at said input terminal and at least one chip of the previously received spread spectrum spreading code sequence are of the same polarity;
said differential decoding means further providing a first analog signal output indication at said output terminal when said chip of said presently received spread spectrum spreading code sequence and said chip of said previously received spread spectrum spreading code sequence are of the same polarity;
and
said differential decoding means further providing a second analog signal output indication at said output terminal when said chip of said presently received spread spectrum spreading code sequence and said chip of said previously received spread spectrum spreading code sequence are of opposite polarity.

3 more elements

determining whether at least one chip of the presently received spread spectrum spreading code sequence and at least one chip of the previously received spread spectrum spreading code sequence are substantially equal;
providing a first output signal indication when said chip of said presently received spread spectrum spreading code sequence and said chip of said previously received spread spectrum spreading code sequence are substantially equal;
and
providing a second output signal indication when said chip of said presently received spread spectrum spreading code sequence and said chip of said previously received spread spectrum spreading code sequence are substantially not equal.

1 more element

Dependencies are inferred from the claim text.

Differential correlator for spread spectrum communication system

Life of this patent

Differential correlator for spread spectrum communication system

Life of this patent

Abstract

Claims9