Spread spectrum receiver and carrier sense circuit therefor

• US 5,111,479 A
• Filed: 10/26/1990
• Issued: 05/05/1992
• Est. Priority Date: 11/02/1989
• Status: Expired due to Fees

• Current Assignee: Clarion Co., Ltd. (Faurecia SA)
• Original Assignee: Clarion Co., Ltd. (Faurecia SA)
• Inventors: Akazawa, Shigeo
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US07/605,258
• Time in Patent Office: 557 Days
• Field of Search: 375/1, 375/80, 375/82, 375/94, 375/106, 380/34, 380/46, 380/48, 329/311
• US Class Current: 375/130
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

A carrier sense circuit for sensing a carrier component of a received signal in a spread spectrum system includes a multiplier which produces a squared signal by multiplying the received signal by itself, a filter which extracts from the squared signal a carrier component of a spread spectrum signal included in the squared signal, and a detecting circuit which detects the level of the carrier component and which outputs a carrier sense signal when the level of the carrier component is greater than a predetermined level. The filter is a band pass filter having a central frequecny of 2f_c where f_c is the central frequency of the spread spectrum signal. Where the spread spectrum system includes an initial synchronization circuit, and a correlation arrangement which correlates the received signal with a reference signal to produce correlation pulses, a circuit can be provided to start the initial synchronization circuit in response to simultaneous occurrence of the carrier sense signal and one of the correlation pulses.

Claims

1. A carrier sense circuit used in a spread spectrum receiver for sensing a carrier component of a received signal, comprising:

operating means for outputting a squared signal which is a received signal multiplied by itself;

a filter for extracting from said squared signal a carrier component of a spread spectrum signal included in said squared signal, said filter outputting said carrier component; and

a detecting circuit for detecting the level of said carrier component and for outputting a carrier sense signal when the level of said carrier component is greater than a predetermined level.

2. A carrier sense circuit according to claim 1 wherein said filter is a band pass filter having a central frequency of 2f_c, f_c being the central frequency of said spread spectrum signal.

3. A carrier sense circuit according to claim 1 wherein said operating means includes a multiplier, which multiplies said received signal by itself.

4. A circuit for use in a spread spectrum receiver, said circuit comprising:

operating means for outputting a squared signal which is a received signal multiplied by itself;

a filter for extracting from said squared signal a carrier component of a spread spectrum signal included in said squared signal, said filter outputting said carrier component;

a detecting circuit for detecting the level of said carrier component and for outputting a carrier sense signal when the level of said carrier component is greater than a predetermined level; and

means for starting an initial synchronization circuit of a spread spectrum receiver in response to said carrier sense signal and a correlation pulse.

5. A circuit according to claim 4 wherein said filter is a band pass filter having a central frequency of 2f_c, f_c being the central frequency of said spread spectrum signal.

6. A spread spectrum receiver according to claim 4 wherein said operating means includes a multiplier, which multiplies said received signal by itself.