Asymmetric spread spectrum correlator

• US 5,016,255 A
• Filed: 08/07/1989
• Issued: 05/14/1991
• Est. Priority Date: 08/07/1989
• Status: Expired due to Term

• Current Assignee: Intel Corporation
• Original Assignee: Omnipoint Data Company, Incorporated
• Inventors: Dixon, Robert C., Vanderpool, Jeffrey S.
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US07/389,914
• Time in Patent Office: 645 Days
• Field of Search: 375/1, 380/34
• US Class Current: 375/151
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 1/7093 Matched filter type

Abstract

An apparatus for decoding a received spread spectrum signal having a data signal modulated with a pseudo-noise code and transmitted as an RF spread spectrum signal. A reference-sequence-storage device holds a reference-pseudo-noise signal, and a receive-sequence storage device holds a received spread spectrum signal. A chip comparator adds each chip of the received spread spectrum signal by each respective chip of the pseudo-noise signal, thereby generating a plurality of chip comparison signals. A summer adds the plurality of chip comparison signals, generating a correlation signal. The comparator compares the correlation signal to a statistically predetermined threshold level, and generates a first data-symbol signal.

Claims

1. An apparatus for decoding a received spread spectrum signal having a data signal modulated with a PN code, comprising:

threshold setting means for analyzing the pattern and application of the data signal, noise environment, and amount of error correction, and determining a threshold level;

reference-sequence-storage means for storing a reference pseudo-noise signal;

receive-sequence-storage means for storing the received spread spectrum signal;

chip-comparison means coupled to said reference-sequence-storage means and said receive-sequence-storage means, and responsive to the received spread spectrum signal for comparing each chip of the received spread spectrum signal with each respective chip of the reference pseudo-noise signal to generate a plurality of chip-comparison signals;

summer means coupled to said chip-comparison means and responsive to the plurality of chip-comparison signals for adding the plurality of chip-comparison signals to generate a correlation signal; and

correlation-comparison means coupled to said summer means and responsive to the correlation signal being greater than the threshold level for generating a first data symbol, and for generating a second data symbol in response to the correlation signal not being greater than the threshold level.

2. The apparatus as set forth in claim 1 wherein said reference-sequence-storage means and said receive-sequence-storage means includes a surface-acoustic-wave device.

3. The apparatus as set forth in claim 2 wherein said surface-acoustic-wave device includes said chip-comparison means and said summer means.

4. An apparatus for demodulating a received spread spectrum signal having a data signal modulated with a PN code, comprising:

threshold setting means for analyzing the pattern and application of the data signal and determining a threshold level;

reference-sequence-storage means for storing a reference pseudo-noise signal;

receive-sequence-storage means for storing the received spread spectrum signal;

chip-comparison means coupled to said reference-sequence-storage means and said receive-sequence-storage means, and responsive to the received spread spectrum signal for comparing each chip of the received spread spectrum signal with each respective chip of the reference pseudo-noise signal to generate a plurality of chip-comparison signals;

summer means coupled to said chip-comparison means and responsive to the plurality of chip-comparison signals for adding the plurality of chip-comparison signals to generate a correlation signal; and

correlation-comparison means, coupled to said threshold setting means, and responsive to the correlation signal being greater than the threshold level for generating a first data-symbol signal.

5. The apparatus as set forth in claim 4 wherein said reference-sequence-storage means and said receive-sequence-storage means includes a surface-acoustic-wave device.

6. The apparatus as set forth in claim 5 wherein said surface-acoustic-wave device includes said chip-comparison means and said summer means.

7. An apparatus for decoding a received spread spectrum signal having a data signal modulated with a PN code, comprising:

threshold setting means for setting a threshold level;

reference-sequence-storage means for storing a reference pseudo-noise signal;

receive-sequence-storage means for storing the received spread spectrum signal;

chip-comparison means for comparing each chip of the received spread spectrum signal with each respective chip of the reference pseudo-noise signal to generate a plurality of chip-comparison signals;

summer means for adding the plurality of chip-comparison signals to generate a correlation signal; and

correlation-comparison means responsive to the correlation signal being greater than the threshold level for generating a first data-symbol signal.

8. The apparatus as set forth in claim 7 wherein said reference-sequence-storage means and said receive-sequence-storage means include a surface-acoustic-wave device.

9. The apparatus as set forth in claim 8 wherein said surface-acoustic-wave device includes said chip-comparison means and said summer means.

10. An apparatus for decoding a received spread spectrum signal having a data signal modulated with a PN code, comprising:

threshold setting means for analyzing the pattern and application of the data signal, noise environment, and amount of error correction, and determining a threshold level;

means for repetitively generating a plurality of reference pseudo-noise signals;

reference-sequence-storage means for storing one of the reference pseudo-noise signals;

receive-sequence-storage means for storing the received spread spectrum signal;

chip-comparison means coupled to said reference-sequence-storage means and said receive-sequence-storage means, and responsive to the received spread spectrum signal for comparing each chip of the received spread spectrum signal with each respective chip of the reference pseudo-noise signal to generate a plurality of chip-comparison signals;

summer means coupled to said chip-comparison means and responsive to the plurality of chip-comparison signals for adding the plurality of chip-comparison signals to generate a correlation signal; and

correlation-comparison means coupled to and said summer means and responsive to the correlation signal being greater than the threshold level for generating a first data symbol, and for generating a second data symbol in response to the correlation signal not being greater than the threshold level.

11. The apparatus as set forth in claim 10 wherein said reference-sequence-storage means and said receive-sequence-storage means includes a surface-acoustic-wave device.

12. The apparatus as set forth in claim 11 wherein said surface-acoustic-wave device includes said chip-comparison means and said summer means.

13. A method using a correlator for decoding a received spread spectrum signal having a data signal modulated with a PN code, comprising the steps, using said correlator, of:

determining a threshold level;

storing a reference pseudo-noise signal;

storing the received spread spectrum signal;

comparing each chip of the received spread spectrum signal with each respective chip of the reference pseudo-noise signal to generate a plurality of chip-comparison signals;

adding the plurality of chip-comparison signals to generate a correlation signal; and

generating a first data symbol in response to the correlation signal being greater than the threshold level.

14. A method using a correlator for decoding a received spread spectrum signal having a data signal modulated with a PN code, comprising the steps, using said correlator, of:

determining a threshold level;

generating repetitively a plurality of reference pseudo-noise signals;

storing one of the reference pseudo-noise signals;

storing the received spread spectrum signal;

comparing each chip of the received spread spectrum signal with each respective chip of the reference pseudo-noise signal to generate a plurality of chip-comparison signals;

adding the plurality of chip-comparison signals to generate a correlation signal; and

generating a first data symbol in response to the correlation signal being greater than the threshold level.

15. A method, using a correlator, for decoding a received spread spectrum signal having a data signal modulated using a PN code, comprising the steps of:

determining a detection threshold level;

generating a correlation signal representing the degree of match between the received spread spectrum signal and a reference pseudo-noise signal corresponding to said PN code; and

generating, at selected clock times, a first data symbol dependent upon a comparison of said correlation signal and said threshold level, and a second data symbol at said clock times when said first data symbol is not generated.

16. An apparatus, using a correlator, for decoding a received spread spectrum signal having a data signal modulated using a PN code, comprising:

means for determining a detection threshold level;

means for generating a correlation signal representing the degree of match between the received spread spectrum signal and a reference pseudo-noise signal corresponding to said PN code; and

means for generating, at selected clock times, a first data symbol signal dependent upon a comparison of said correlation signal and said threshold level, and a second data symbol signal at said clock times when said first data symbol is not generated.