Apparatus and method for suppressing side lobe response in a digitally sampled system
First Claim
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1. A decoder circuit for detecting the presence of a signal exhibiting a predetermined frequency, comprising:
- timing means for generating observation interval signals;
sampling means, responsive to said timing means, for sampling a first signal to produce samples thereof including a first sample during a substantially rectangular observation interval, said sampling means including means for ignoring a portion of said samples occurring near the beginning of said observation interal and after said first sample, andcorrelation means, electrical coupled to said sampling means, for correlating said samples with a predetermined pattern to detect the presence of a signal exhibiting said predetermined frequency within said first signal.
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Abstract
A decoder circuit is provided which employs digital sampling and correlation apparatus to detect the presence of a received tone signal exhibiting a predetermined frequency. Samples of received tone signals are taken and, in effect, multiplied by a substantially rectangular observation window which includes a bite interval of selected duration and location therein. A correlator correlates the windowed samples to detect samples corresponding to the predetermined frequency (main lobe frequency). A significant decrease in undesired side lobe response is thus achieved.
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Citations
59 Claims
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1. A decoder circuit for detecting the presence of a signal exhibiting a predetermined frequency, comprising:
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timing means for generating observation interval signals; sampling means, responsive to said timing means, for sampling a first signal to produce samples thereof including a first sample during a substantially rectangular observation interval, said sampling means including means for ignoring a portion of said samples occurring near the beginning of said observation interal and after said first sample, and correlation means, electrical coupled to said sampling means, for correlating said samples with a predetermined pattern to detect the presence of a signal exhibiting said predetermined frequency within said first signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A decoder circuit for detecting the presence of a signal exhibiting a predetermined frequency comprising:
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timing means for generating observation interval signals; sampling means, responsive to said timing means, for sampling a first signal to produce samples thereof including a last sample during a substantially rectangular observation interval, said sampling means including means for ignoring a portion of said samples occurring prior to said last sample and near the end of said observation interval, and correlation means, electrically coupled to said sampling means, for correlating said samples with a predetermined pattern to detect the presence of a signal exhibiting said predetermined frequency within said first signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A decoder circuit for detecting the presence of a a predetermined frequency within a signal, comprising:
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timing means for generating observation intervals; sampling means, responsive to said timing means, for sampling a first signal to produce samples thereof including a first sample during said obseration intervals; sample inhibiting means, coupled to said sampling means, for inhibiting said sampling means from sampling for a predetermined portion of said observation interval, said predetermined portion of said observation interval occurring after said first sample and near the beginning of said observation interval; and correlation means, electrically coupled to said sampling means, for correlating said samples with a predetermined pattern to detect the presence of said predetermined frequency within said first signal. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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28. A decoder circuit for detecting the presence of a a predetermined frequency within a signal, comprising:
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timing means for generating observation intervals; sampling means, responsive to said timing means, for sampling a first signal to produce samples thereof including a last sample during said observation intervals; sample inhibiting means, coupled to said sampling means, for inhibiting said sampling means from sampling for a predetermined portion of said observation interval, said predetermined portion of said observation interval occurring prior to said last sample and near the end of said observation interval; and correlation means, electrically coupled to said sampling means, for correlating said samples with a predetermined pattern to detect the presence of said predetermined frequency within said first signal. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
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37. A decoder for detecting the presence of a signal exhibiting a predetermined frequency comprising:
microcomputer means for processing sampled signal information, said microcomputer including a random access memory and a read only memory for storing information therein, and including a plurality of registers for facilitating processing of such information, said microcomputer means further including sampling means for sampling a first signal to produce samples thereof including a first sample during a substantially rectangular observation window, ignoring means, responsive to said sampling, for ignoring a portion of said samples occuring after said first sample and near the beginning of said observation window, and correlation means for correlating said samples with a predetermined pattern to detect the presence of said predetermined frequency within said first signal. - View Dependent Claims (38, 39, 40, 41, 42, 43, 45)
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44. A decoder for detecting the presence of a signal exhibting a predetermined frequency comprising:
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microcomputer means for processing digital signal information including a random access memory and a read only memory for storing information therein, and including a plurality of registers for facilitating processing of such information, said microcomputer means further including sampling means for sampling a first signal to produce samples thereof including a last sample during a substantially rectangular observation window, ignoring means, responsive to said sampling means, for ignoring a portion of said samples occurring prior to said last sample and near the end of said observation window, and correlating means for correlating said samples with a predetermined pattern to detect the presence of a signal exhibiting said predetermined frequency within said first signal. - View Dependent Claims (46, 47, 48, 49, 50)
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51. A method of processing a particular signal to determine if said particular signal exhibits a predetermined frequency comprising the steps of:
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generating an observation interval signal;
sampling said particular signal during the observation window established by said observation interval signal, to produce samples of said particular signal including a first sample;ignoring a portion of the samples of said particular signal occurring in time after said first sample and near the beginning of said observation window, and correlating the samples of said particular signal which are not ignored with a predetermined pattern to detect the presence of said predetermined frequency. - View Dependent Claims (52)
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53. A method of processing a particular signal to determine if said particular signal exhibits a predetermined frequency comprising the steps of:
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generating an observation interval signal; sampling said particular signal during the obsevation window established by said observation interval signal, to produce samples of said particular signal including a last sample; ignoring a plurality of the samples of said particular signal occurring in time prior to said last sample and near the end of said observation window, and, correlating the samples of said particular signal which are not ignored with a predetermilned pattern to detect the presence of a signal exhibiting said predetermined frequency. - View Dependent Claims (54)
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55. A method of providing a computer with processing time for performing other tasks when said computer is functioning as a correlator for correlating a sampled signal with a predetermined pattern to determine the presence of a predetermined frequency, said method comprising the steps of:
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sampling a first signal to produce samples thereof including a first sample during a first time segment of a predetermined observation window; interrupting said sampling for a second time segment of said predetermined observation window to enable said computer to perform said other task thereby effectively ignoring said first signal during said second time segment; sampling said first signal for the remainder of said predetermined observation window to produce samples thereof including a last sample; and correlating said samples with said predetermined pattern to determine the presence of said predetermined frequency for a first time segment of said observation window. - View Dependent Claims (56, 57, 58, 59)
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Specification