Signal correlation means

• US 4,224,679 A
• Filed: 10/16/1978
• Issued: 09/23/1980
• Est. Priority Date: 10/16/1978
• Status: Expired due to Term

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: RCA Corporation (General Electric Company)
• Inventors: Haber, Conrad H., Nossen, Edward J.
• Primary Examiner(s): Smith, Jerry
• Application Number:
  US05/951,381
• Time in Patent Office: 708 Days
• Field of Search: 364/728, 364/819-824
• US Class Current: 708/422
• CPC Class Codes: G06F 17/15 Correlation function computation including computation of convolution operations arithmetic circuits for sum of products per se, e.g. multiply-accumulators G06F7/5443; digital filters, e.g. FIR, IIR, adaptive filters H03H17/00

Abstract

A means for reducing side lobe signals and noise signals generated in a correlator in N chip positions for correlating a received input signal with a reference signal. The coincidence and non-coincidence indicating signals of first and second halves of the chip positions of the correlator are added together separately and then subtracted one from the other, with the resulting difference signal then being rectified. Such rectified difference signal which contains the side lobe signals and the noise signals but not the desired correlator indicating signal, is subtracted from the total summed and rectified signals generated by all of the N chip positions of said correlator to produce a resultant signal with much of the side lobe signals and the noise signals cancelled out.

Claims

1. Means for reducing side lobe signals and noise signals generated in a correlator having N chip (bit) positions for comparing a received coded input signal with a stored reference signal and comprising:

adding means for producing a total summed and rectified signal consisting of all the signals generated by said correlator in each chip position thereof;

first differencing means for producing a total differenced signal consisting of the rectified difference of the total summed signals generated in a first half of the N chip positions of said correlator from the total summed signals generated in the second half of N chip positions of said correlator; and

second differencing means for taking the difference between said total differenced signal and said total summed and rectified signal to produce enhanced output signals.

2. A side lobe signal reudcing means as in claim 1 and further comprising:

integrating means for integrating said total differenced signal to produce a mean noise level signal; and

gating means responsive to said mean noise level signal to pass therethrough said enhanced output signals from said second differencing means whose magnitudes exceed that of said mean noise level signal.

3. In a system for identifying a received coded signal by a correlator means of N chip (bit) positions which compare the received signal with a reference signal to produce coincidence and non-coincidence indicating signals, a side lobe signal reduction means comprising:

logic means for adding together and rectifying all of the correlator output signals to produce a total summed and rectified correlator output signal;

first differencing means for subtracting the summed individual coincidence and non-coincidence indicating output signals from one half of the correlator chip positions from the summed individual coincidence and non-coincidence indicating output signals from the other half of correlator chip positions to produce a total difference correlator output signal;

means for rectifying said total difference correlator output signal; and

second differencing means for subtracting the rectified total difference correlator signal from said total summed correlator output signal to produce an enhanced output signal.

4. A side lobe reducing circuit as in claim 3 and further comprising:

integrating means for integrating the said rectified total difference correlator output signal to produce a mean noise level signal; and

gating means responsive to said mean noise level signal to pass therethrough said enhanced output signals from said second differencing means whose magnitudes exceed that of said mean noise level signal.

5. Means for reducing side lobe signal and noise signals generated in a dual correlation circuit comprising first and second correlators each having N chip positions for comparing first and second input signals with a reference signal and comprising:

means for producing a total summed and rectified signal consisting of all of the signals generated by said first and second correlators in each chip position thereof;

first differencing means for producing a total difference signal consisting of the rectified difference between the total summed signals generated in a first half of the N chip positions of each of said first and second correlators and the total summed signals generated in each of the second half of N chip positions of said first and second correlators; and

second differencing means for taking the difference between said total difference signal and said total summed and rectified signal to produce an enhanced output signal.

6. A side lobe reducing circuit as in claim 5 and further comprising:

integrating means for integrating the said total difference signal to produce a mean noise level signal; and

gating means responsive to said mean noise level signal to pass therethrough said enhanced output signal from said second differencing means whose magnitudes exceed that of said means noise level signal.