US5040192A
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Method and apparatus for optimally autocorrelating an FSK signal
Assignee: Telogy Networks Inc
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Filing: 1990-02-06
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Granted: 1991-08-13
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Expires: 2010-02-06
Abstract
Abstract An autocorrelator for FSK signals. An FSK signal, incoming on a telephone line is filtered by a bandpass filter (13) and sampled by an A/D converter (14). A sample clock (15) provides a fixed sampling frequency, FS. A first interpolating filter (20B) provides selectable delays which are non-integer multiples of 1/FS, and an integer delay (25) provides selectable delays which are integer multiples of 1/FS. The delayed signals are multiplied by a multiplier (26) and then filtered by a low pass filter (27) to provide a filtered autocorrelated signal. A second interpolating filter (20A) provides for reduced jitter in the baud timing by increasing the number of samples provided to the decision logic (23). The decision logic (23) provides the decoded data output.
Inventors
- 👤 Taruna Tjahjadi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 22:53
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/14; H04L27/144; H04L27/152; H04L27/1525; H04L7/00; H04L7/0016; H04L7/002; H04L7/0029
Claims Analysis
Total Claims: 81
Claim 1
Independent Claim
191 words
An apparatus for receiving a frequency shift keyed (FSK) signal, said FSK signal comprising a first signal at a first frequency and a second signal at a second frequency comprising: filtering means for providing a filtered FSK signal by filtering said FSK signal said filtering means attenuating said first signal more than said second signal; an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said filtered FSK signal; first delay means for providing a first delayed signal by delaying said sampled signal by a first delay time; second delay means for providing a second delayed signal by delaying said sampled signal by a second delay time; a multiplier for providing an autocorrelated signal by multiplying said first delayed signal by said second delayed signal; a low pass filter for providing a filtered autocorrelated signal by filtering said autocorrelated signal; and decision logic for recovering data represented by said FSK signal by decoding said filtered autocorrelated signal; wherein the difference between said first delay time and said second delay time optimizes recovery of data represented by said FSK signal by at least partially compensating for said filtering means.
Claim 2
Independent Claim
191 words
An apparatus for receiving a frequency shift keyed (FSK) signal, said FSK signal comprising a first signal at a first frequency and a second signal at a second frequency comprising: filtering means for providing a filtered FSK signal by filtering said FSK signal said filtering means attenuating said first signal more than said second signal; an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said filtered FSK signal; first delay means for providing a first delayed signal by delaying said sampled signal by a first delay time; second delay means for providing a second delayed signal by delaying said sampled signal by a second delay time; a multiplier for providing an autocorrelated signal by multiplying said first delayed signal by said second delayed signal; a low pass filter for providing a filtered autocorrelated signal by filtering said autocorrelated signal; and decision logic for recovering data represented by said FSK signal by decoding said filtered autocorrelated signal; wherein the difference between said first delay time and said second delay time optimizes recovery of data represented by said FSK signal by at least partially compensating for said filtering means.
Claim 3
Dependent Claim
13 words
The apparatus of claim 1 wherein said filtering means comprises a bandpass filter.
Claim 4
Dependent Claim
58 words
The apparatus of claim 1 wherein said filtered autocorrelated signal comprises a filtered autocorrelated first signal and a filtered autocorrelated second signal, and said difference between said first delay time and said second delay time causes said filtered autocorrelated first signal to have a value which is the negative of the value of said filtered autocorrelated second signal.
Claim 5
Dependent Claim
21 words
The apparatus of claim 1 wherein said A/D converter samples and converts said FSK signal at a fixed sampling frequency, FS.
Claim 6
Dependent Claim
16 words
The apparatus of claim 4 wherein said first delay time is an integer multiple of 1/FS.
Claim 7
Dependent Claim
16 words
The apparatus of claim 5 wherein said second delay time is a non-integer multiple of 1/FS.
Claim 8
Dependent Claim
23 words
The apparatus of claim 1 wherein at least one of said first delay means and said second delay means comprises an interpolating filter.
Claim 9
Independent Claim
169 words
An apparatus for receiving a frequency shift keyed (FSK) signal, comprising: an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said FSK signal; first delay means for providing a first delayed signal by delaying said sampled signal by a first delay time; second delay means for providing a second delayed signal by delaying said sampled signal by a second delay time; a multiplier for providing an autocorrelated signal by multiplying said first delayed signal by said second delayed signal; a low pass filter for providing a filtered autocorrelated signal by filtering said autocorrelated signal; decision logic for recovering data represented by said FSK signal by decoding said filtered autocorrelated signal; and selection means for providing a delay selection signal to said first delay means; wherein said first delay means provides a first plurality of delay times; and said first delay means is responsive to said delay selection signal for providing a selected one of said first plurality of delay times as said first delay time.
Claim 10
Independent Claim
169 words
An apparatus for receiving a frequency shift keyed (FSK) signal, comprising: an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said FSK signal; first delay means for providing a first delayed signal by delaying said sampled signal by a first delay time; second delay means for providing a second delayed signal by delaying said sampled signal by a second delay time; a multiplier for providing an autocorrelated signal by multiplying said first delayed signal by said second delayed signal; a low pass filter for providing a filtered autocorrelated signal by filtering said autocorrelated signal; decision logic for recovering data represented by said FSK signal by decoding said filtered autocorrelated signal; and selection means for providing a delay selection signal to said first delay means; wherein said first delay means provides a first plurality of delay times; and said first delay means is responsive to said delay selection signal for providing a selected one of said first plurality of delay times as said first delay time.
Claim 11
Dependent Claim
46 words
The apparatus of claim 8 wherein: said second delay means provides a second plurality of delay times; and said second delay means is responsive to said delay selection signal for providing a selected one of said second plurality of delay times as said second delay time.
Claim 12
Dependent Claim
42 words
The apparatus of claim 9 wherein: said A/D converter samples and converts said FSK signal at a fixed sampling frequency, FS; said first delay time is an integer multiple of 1/FS; and said second delay time is a non-integer multiple of 1/FS.
Claim 13
Dependent Claim
28 words
The apparatus of claim 10 wherein the difference between said first delay time and said second delay time optimizes recovery of said data represented by said FSK signal.
Claim 14
Dependent Claim
69 words
The apparatus of claim 11 wherein said FSK signal comprises a mark signal and a space signal, said filtered autocorrelated signal comprises a filtered autocorrelated mark signal and a filtered autocorrelated space signal, and said difference between said first delay time and said second delay time causes said filtered autocorrelated mark signal to have a value which is the negative of the value of said filtered autocorrelated space signal.
Claim 15
Dependent Claim
23 words
The apparatus of claim 8 wherein at least one of said first delay means and said second delay means comprises an interpolating filter.
Claim 16
Independent Claim
161 words
A method for receiving a frequency shift keyed (FSK) signal, said FSK signal comprising a first signal at a first frequency and a second signal at a second frequency, comprising the steps of: filtering said FSK signal to provide a filtered FSK signal; sampling said filtered FSK signal to provide a sampled signal; delaying said sampled signal by a first delay time to provide a first delayed signal; delaying said sampled signal by a second delay time to provide a second delayed signal; multiplying said first delayed signal by said second delayed signal to provide an autocorrelated signal; filtering said autocorrelated signal to provide a filtered autocorrelated signal said step of filtering comprising attenuating said first signal more than said second signal; and decoding said filtered autocorrelated signal to recover data represented by said FSK signal; wherein the difference between said first delay time and said second delay time is selected to optimize recovery of data represented by said FSK signal.
Claim 17
Independent Claim
161 words
A method for receiving a frequency shift keyed (FSK) signal, said FSK signal comprising a first signal at a first frequency and a second signal at a second frequency, comprising the steps of: filtering said FSK signal to provide a filtered FSK signal; sampling said filtered FSK signal to provide a sampled signal; delaying said sampled signal by a first delay time to provide a first delayed signal; delaying said sampled signal by a second delay time to provide a second delayed signal; multiplying said first delayed signal by said second delayed signal to provide an autocorrelated signal; filtering said autocorrelated signal to provide a filtered autocorrelated signal said step of filtering comprising attenuating said first signal more than said second signal; and decoding said filtered autocorrelated signal to recover data represented by said FSK signal; wherein the difference between said first delay time and said second delay time is selected to optimize recovery of data represented by said FSK signal.
Claim 18
Dependent Claim
16 words
The method of claim 14 wherein said step of filtering comprises bandpass filtering said FSK signal.
Claim 19
Dependent Claim
61 words
The method of claim 14 wherein said filtered autocorrelated signal comprises a filtered autocorrelated first signal and a filtered autocorrelated second signal, and the difference between said first delay time and said second delay time is selected to cause said filtered autocorrelated first signal to have a value which is the negative of the value of said filtered autocorrelated second signal.
Claim 20
Dependent Claim
18 words
The method of claim 14 wherein said step of sampling comprises sampling at a fixed sampling frequency, FS.
Claim 21
Dependent Claim
16 words
The method of claim 17 wherein said first delay time is an integer multiple of 1/FS.
Claim 22
Dependent Claim
16 words
The method of claim 18 wherein said second delay time is a non-integer multiple of 1/FS.
Claim 23
Dependent Claim
45 words
The method of claim 14 wherein at least one of said steps of delaying said sampled signal comprises using an interpolating filter to provide a delay which is a non-integer multiple of the period of a sampling frequency used to perform said step of sampling.
Claim 24
Independent Claim
106 words
A method for receiving a frequency shift keyed (FSK) signal, comprising the steps of: sampling said FSK signal to provide a sampled signal; selecting one of a first plurality of delay times for a first delay time; delaying said sampled signal by said first delay time to provide a first delayed signal; delaying said sampled signal by a second delay time to provide a second delayed signal; multiplying said first delayed signal by said second delayed signal to provide an autocorrelated signal; filtering said autocorrelated signal to provide a filtered autocorrelated signal; and decoding said filtered autocorrelated signal to recover data represented by said FSK signal.
Claim 25
Independent Claim
106 words
A method for receiving a frequency shift keyed (FSK) signal, comprising the steps of: sampling said FSK signal to provide a sampled signal; selecting one of a first plurality of delay times for a first delay time; delaying said sampled signal by said first delay time to provide a first delayed signal; delaying said sampled signal by a second delay time to provide a second delayed signal; multiplying said first delayed signal by said second delayed signal to provide an autocorrelated signal; filtering said autocorrelated signal to provide a filtered autocorrelated signal; and decoding said filtered autocorrelated signal to recover data represented by said FSK signal.
Claim 26
Dependent Claim
25 words
The method of claim 21 and further comprising the step of: selecting one of a second plurality of delay times for said second delay time.
Claim 27
Dependent Claim
39 words
The method of claim 22 wherein: said step of sampling comprises sampling at a fixed sampling frequency, FS; said first delay time is an integer multiple of 1/FS; and said second delay time is a non-integer multiple of 1/FS.
Claim 28
Dependent Claim
29 words
The method of claim 23 wherein the difference between said first delay time and said second delay time optimizes the recovery of said data represented by said FSK signal.
Claim 29
Dependent Claim
45 words
The method of claim 21 wherein at least one of said steps of delaying said sampled signal comprises using an interpolating filter to provide a delay which is a non-integer multiple of the period of a sampling frequency used to perform said step of sampling.
Claim 30
Independent Claim
215 words
An apparatus for receiving a frequency shift keyed (FSK) signal, said FSK signal comprising a first signal at a first frequency and a second signal at a second frequency, comprising filtering means for providing a filtered FSK signal by filtering said FSK signal, said filtering means attenuating said first signal more than said second signal: an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said filtered FSK signal at a fixed sampling frequency, FS; first delay means for providing a first delayed signal by delaying said sampled signal by a first delay time; second delay means for providing a second delayed signal by delaying said first delayed signal by a second delay time, the sum of said first delay time and said second delay time being a non-integer multiple of 1/FS; a multiplier for providing an autocorrelated signal by multiplying said second delayed signal by said sampled signal; a low pass filter for providing a filtered autocorrelated signal by filtering said autocorrelated signal; and decision logic for recovering data represented by said FSK signal by decoding said filtered autocorrelated signal; wherein said sum of said first delay time and said second delay time optimizes recovery of data represented by said FSK signal by at least partially compensating for said filtering means.
Claim 31
Independent Claim
215 words
An apparatus for receiving a frequency shift keyed (FSK) signal, said FSK signal comprising a first signal at a first frequency and a second signal at a second frequency, comprising filtering means for providing a filtered FSK signal by filtering said FSK signal, said filtering means attenuating said first signal more than said second signal: an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said filtered FSK signal at a fixed sampling frequency, FS; first delay means for providing a first delayed signal by delaying said sampled signal by a first delay time; second delay means for providing a second delayed signal by delaying said first delayed signal by a second delay time, the sum of said first delay time and said second delay time being a non-integer multiple of 1/FS; a multiplier for providing an autocorrelated signal by multiplying said second delayed signal by said sampled signal; a low pass filter for providing a filtered autocorrelated signal by filtering said autocorrelated signal; and decision logic for recovering data represented by said FSK signal by decoding said filtered autocorrelated signal; wherein said sum of said first delay time and said second delay time optimizes recovery of data represented by said FSK signal by at least partially compensating for said filtering means.
Claim 32
Dependent Claim
13 words
The apparatus of claim 26 wherein said filtering means comprises a bandpass filter.
Claim 33
Dependent Claim
58 words
The apparatus of claim 26 wherein said filtered autocorrelated signal comprises a filtered autocorrelated first signal and a filtered autocorrelated second signal, and said sum of said first delay time and said second delay time causes said filtered autocorrelated first signal to have a value which is the negative of the value of said filtered autocorrelated second signal.
Claim 34
Dependent Claim
25 words
The apparatus of claim 26 wherein a selected one of said first delay time and said second delay time is an integer multiple of 1/FS.
Claim 35
Dependent Claim
25 words
The apparatus of claim 29 wherein the non-selected one of said first delay time and said second delay time is a non-integer multiple of 1/FS.
Claim 36
Dependent Claim
23 words
The apparatus of claim 26 wherein at least one of said first delay means and said second delay means comprises an interpolating filter.
Claim 37
Independent Claim
193 words
An apparatus for receiving a frequency shift keyed (FSK) signal, comprising: an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said FSK signal at a fixed sampling frequency, FS; first delay means for providing a first delayed signal by delaying said sampled signal by a first delay time; second delay means for providing a second delayed signal by delaying said first delayed signal by a second delay time, the sum of said first delay time and said second delay time being a non-integer multiple of 1/FS; a multiplier for providing an autocorrelated signal by multiplying said second delayed signal by said sampled signal; a low pass filter for providing a filtered autocorrelated signal by filtering said autocorrelated signal; decision logic for recovering data represented by said FSK signal by decoding said filtered autocorrelated signal; and selection means for providing a delay selection signal to said first delay means; wherein said first delay means provides a first plurality of delay times; and said first delay means is responsive to said delay selection signal for providing a selected one of said first plurality of delay times as said first delay time.
Claim 38
Independent Claim
193 words
An apparatus for receiving a frequency shift keyed (FSK) signal, comprising: an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said FSK signal at a fixed sampling frequency, FS; first delay means for providing a first delayed signal by delaying said sampled signal by a first delay time; second delay means for providing a second delayed signal by delaying said first delayed signal by a second delay time, the sum of said first delay time and said second delay time being a non-integer multiple of 1/FS; a multiplier for providing an autocorrelated signal by multiplying said second delayed signal by said sampled signal; a low pass filter for providing a filtered autocorrelated signal by filtering said autocorrelated signal; decision logic for recovering data represented by said FSK signal by decoding said filtered autocorrelated signal; and selection means for providing a delay selection signal to said first delay means; wherein said first delay means provides a first plurality of delay times; and said first delay means is responsive to said delay selection signal for providing a selected one of said first plurality of delay times as said first delay time.
Claim 39
Dependent Claim
46 words
The apparatus of claim 32 wherein: said second delay means provides a second plurality of delay times; and said second delay means is responsive to said delay selection signal for providing a selected one of said second plurality of delay times as said second delay time.
Claim 40
Dependent Claim
28 words
The apparatus of claim 33 wherein the sum of said first delay time and said second delay time optimizes recovery of said data represented by said FSK signal.
Claim 41
Dependent Claim
23 words
The apparatus of claim 32 wherein at least one of said first delay means and said second delay means comprises an interpolating filter.
Claim 42
Independent Claim
185 words
A method for receiving a frequency shift keyed (FSK) signal, said FSK signal comprising a first signal at a first frequency and a second signal at a second frequency, comprising the steps of: filtering said FSK signal to provide a filtered FSK signal, said step of filtering comprising attenuating said first signal more than said second signal; sampling said filtered FSK signal at a fixed sampling frequency, FS, to provide a sampled signal; delaying said sampled signal by a first delay time to provide a first delayed signal; delaying said first delayed signal by a second delay time to provide a second delayed signal, the sum of said first delay time and said second delay time being a non-integer multiple of 1/FS; multiplying said second delayed signal by said sampled signal to provide an autocorrelated signal; filtering said autocorrelated signal to provide a filtered autocorrelated signal; and decoding said filtered autocorrelated signal to recover data represented by said FSK signal; wherein the difference between said first delay time and said second delay time is selected to optimize recovery of data represented by said FSK signal.
Claim 43
Independent Claim
185 words
A method for receiving a frequency shift keyed (FSK) signal, said FSK signal comprising a first signal at a first frequency and a second signal at a second frequency, comprising the steps of: filtering said FSK signal to provide a filtered FSK signal, said step of filtering comprising attenuating said first signal more than said second signal; sampling said filtered FSK signal at a fixed sampling frequency, FS, to provide a sampled signal; delaying said sampled signal by a first delay time to provide a first delayed signal; delaying said first delayed signal by a second delay time to provide a second delayed signal, the sum of said first delay time and said second delay time being a non-integer multiple of 1/FS; multiplying said second delayed signal by said sampled signal to provide an autocorrelated signal; filtering said autocorrelated signal to provide a filtered autocorrelated signal; and decoding said filtered autocorrelated signal to recover data represented by said FSK signal; wherein the difference between said first delay time and said second delay time is selected to optimize recovery of data represented by said FSK signal.
Claim 44
Dependent Claim
16 words
The method of claim 36 wherein said step of filtering comprises bandpass filtering said FSK signal.
Claim 45
Dependent Claim
61 words
The method of claim 36 wherein said filtered autocorrelated signal comprises a filtered autocorrelated first signal and a filtered autocorrelated second signal, and the difference between said first delay time and said second delay time is selected to cause said filtered autocorrelated first signal to have a value which is the negative of the value of said filtered autocorrelated second signal.
Claim 46
Dependent Claim
25 words
The method of claim 36 wherein a selected one of said first delay time and said second delay time is an integer multiple of 1/FS.
Claim 47
Dependent Claim
25 words
The method of claim 39 wherein the non-selected one of said first delay time and said second delay time is a non-integer multiple of 1/FS.
Claim 48
Dependent Claim
45 words
The method of claim 36 wherein at least one of said steps of delaying said sampled signal comprises using an interpolating filter to provide a delay which is a non-integer multiple of the period of a sampling frequency used to perform said step of sampling.
Claim 49
Independent Claim
144 words
A method for receiving a frequency shift keyed (FSK) signal, comprising the steps of; sampling said FSK signal at a fixed sampling frequency, FS, to provide a sampled signal; delaying said sampled signal by a first delay time to provide a first delayed signal; selecting one of a first plurality of delay times for said first delay time; delaying said first delayed signal by a second delay time to provide a second delayed signal, the sum of said first delay time and said second delay time being a non-integer multiple of 1/FS; selecting one of a second plurality of delay times for said second delay time; multiplying said second delayed signal by said sampled signal to provide an autocorrelated signal; filtering said autocorrelated signal to provide a filtered autocorrelated signal; and decoding said filtered autocorrelated signal to recover data represented by said FSK signal.
Claim 50
Independent Claim
144 words
A method for receiving a frequency shift keyed (FSK) signal, comprising the steps of; sampling said FSK signal at a fixed sampling frequency, FS, to provide a sampled signal; delaying said sampled signal by a first delay time to provide a first delayed signal; selecting one of a first plurality of delay times for said first delay time; delaying said first delayed signal by a second delay time to provide a second delayed signal, the sum of said first delay time and said second delay time being a non-integer multiple of 1/FS; selecting one of a second plurality of delay times for said second delay time; multiplying said second delayed signal by said sampled signal to provide an autocorrelated signal; filtering said autocorrelated signal to provide a filtered autocorrelated signal; and decoding said filtered autocorrelated signal to recover data represented by said FSK signal.
Claim 51
Dependent Claim
45 words
The method of claim 42 wherein at least one of said steps of delaying said sampled signal comprises using an interpolating filter to provide a delay which is a non-integer multiple of the period of a sampling frequency used to perform said step of sampling.
Claim 52
Dependent Claim
384 words
A modem receiver for receiving frequency shift keyed (FSK), phase shift keyed (PSK), and phase and amplitude modulated (PAM) signals, comprising: first filtering means for providing a filtered signal by filtering said FSK, PSK, and PAM signals; an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said filtered signal; a demodulator for demodulating said PSK and PAM signals to provide in-phase (I) and quadrature phase (Q) signals; a first interpolating filter, responsive to a first predetermined one of said I and Q signals for providing a first interpolated signal when said modem receiver is operating in a PSK mode or a PAM mode, and for providing a first delayed signal by delaying said sampled signal by a first delay time when said modem receiver is operating in an FSK mode; a second interpolating filter, responsive to a second predetermined one of said I and Q signals for providing a second interpolated signal when said modem receiver is operating in said PSK mode or said PAM mode; delay means for providing a second delayed signal by delaying said sampled signal by a second delay time when said modem receiver is operating in said FSK mode; adaptive equalizer means responsive to said first interpolated signal and said second interpolated signal for providing an equalized signal and equalization coefficients; filter control means responsive to said equalization coefficients for controlling the operation of said first interpolating filter and said second interpolating filter when said modem receiver is operating in said PSK mode or said PAM mode; multiplier means for providing an autocorrelated signal by multiplying said first delayed signal by said second delayed signal; second filtering means for providing a filtered autocorrelated signal by filtering said autocorrelated signal; decision logic means, responsive to said equalized signal for recovering data represented by said PSK signal when said modem receiver is in said PSK mode, responsive to said equalized signal for recovering data represented by said PAM signal when said modem receiver is in said PAM mode, and responsive to said filtered autocorrelated signal for recovering data represented by said FSK signal when said modem receiver is in said FSK mode; and control means for causing said modem receiver to operate in a selected one of said FSK mode, said PSK mode, or said PAM mode.
Claim 53
Dependent Claim
384 words
A modem receiver for receiving frequency shift keyed (FSK), phase shift keyed (PSK), and phase and amplitude modulated (PAM) signals, comprising: first filtering means for providing a filtered signal by filtering said FSK, PSK, and PAM signals; an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said filtered signal; a demodulator for demodulating said PSK and PAM signals to provide in-phase (I) and quadrature phase (Q) signals; a first interpolating filter, responsive to a first predetermined one of said I and Q signals for providing a first interpolated signal when said modem receiver is operating in a PSK mode or a PAM mode, and for providing a first delayed signal by delaying said sampled signal by a first delay time when said modem receiver is operating in an FSK mode; a second interpolating filter, responsive to a second predetermined one of said I and Q signals for providing a second interpolated signal when said modem receiver is operating in said PSK mode or said PAM mode; delay means for providing a second delayed signal by delaying said sampled signal by a second delay time when said modem receiver is operating in said FSK mode; adaptive equalizer means responsive to said first interpolated signal and said second interpolated signal for providing an equalized signal and equalization coefficients; filter control means responsive to said equalization coefficients for controlling the operation of said first interpolating filter and said second interpolating filter when said modem receiver is operating in said PSK mode or said PAM mode; multiplier means for providing an autocorrelated signal by multiplying said first delayed signal by said second delayed signal; second filtering means for providing a filtered autocorrelated signal by filtering said autocorrelated signal; decision logic means, responsive to said equalized signal for recovering data represented by said PSK signal when said modem receiver is in said PSK mode, responsive to said equalized signal for recovering data represented by said PAM signal when said modem receiver is in said PAM mode, and responsive to said filtered autocorrelated signal for recovering data represented by said FSK signal when said modem receiver is in said FSK mode; and control means for causing said modem receiver to operate in a selected one of said FSK mode, said PSK mode, or said PAM mode.
Claim 54
Dependent Claim
16 words
The modem receiver of claim 44 wherein said second filtering means is a low pass filter.
Claim 55
Dependent Claim
22 words
The modem receiver of claim 44 wherein said A/D converter samples and converts said filtered signal at a fixed sampling frequency, FS.
Claim 56
Dependent Claim
17 words
The modem receiver of claim 46 wherein said first delay time is a non-integer multiple of 1/FS.
Claim 57
Dependent Claim
17 words
The modem receiver of claim 47 wherein said second delay time is an integer multiple of 1/FS.
Claim 58
Dependent Claim
28 words
The modem receiver of claim 48 wherein the difference between said first delay time and said second delay time optimizes recovery of data represented by said FSK signal.
Claim 59
Dependent Claim
90 words
The modem receiver of claim 44 and further comprising: selection means for providing a delay selection signal; wherein said first interpolating filter provides a first plurality of delay times and is responsive to said delay selection signal for providing a selected one of said first plurality of delay times as said first delay time; and said delay means provides a second plurality of delay times and is responsive to said delay selection signal for providing a selected one of said second plurality of delay times as said second delay time.
Claim 60
Dependent Claim
43 words
The modem receiver of claim 50 wherein: said A/D converter samples and converts said filtered signal at a fixed sampling frequency, FS; said first delay time is a non-integer multiple of 1/FS; and said second delay time is an integer multiple of 1/FS.
Claim 61
Dependent Claim
28 words
The modem receiver of claim 51 wherein the difference between said first delay time and said second delay time optimizes recovery of data represented by said PSK signal.
Claim 62
Dependent Claim
15 words
The modem receiver of claim 44 wherein said first filtering means is a bandpass filter.
Claim 63
Dependent Claim
61 words
The modem receiver of claim 44 wherein said FSK signal comprises a first signal at a first frequency and a second signal at a second frequency, said first filtering means attenuates said first signal more than said second signal, and the difference between said first delay time and said second delay time optimizes recovery of data represented by said FSK signal.
Claim 64
Dependent Claim
59 words
The modem receiver of claim 54 wherein said filtered autocorrelated signal comprises a filtered autocorrelated first signal and a filtered autocorrelated second signal, and the difference between said first delay time and said second delay time causes said filtered autocorrelated first signal to have a value which is the negative of the value of said filtered autocorrelated second signal.
Claim 65
Dependent Claim
67 words
The modem receiver of claim 44 wherein: said second filtering means provides a predetermined number of samples of said filtered autocorrelated signal per unit of time; said second interpolating filter is interposed between said second filtering means and said decision logic means and said second interpolating filter increases the number of samples per unit of time of said filtered autocorrelated signal provided to said decision logic means.
Claim 66
Dependent Claim
20 words
The modem receiver of claim 56 wherein said second interpolating filter doubles said number of samples per unit of time.
Claim 67
Dependent Claim
415 words
A modem receiver for receiving frequency shift keyed (FSK), phase shift keyed (PSK), and phase and amplitude modulated (PAM) signals, comprising: first filtering means for providing a filtered signal by filtering said FSK, PSK, and PAM signals; an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said filtered signal; a demodulator for demodulating said PSK and PAM signals to provide in-phase (I) and quadrature phase (Q) signals; a first interpolating filter, responsive to a first predetermined one of said I and Q signals for providing a first interpolated signal when said modem receiver is operating in a PSK mode or a PAM mode, and for providing a delayed signal by delaying said sampled signal for a first delay time when said modem receiver is operating in said FSK mode; a second interpolating filter, responsive to a second predetermined one of said I and Q signals for providing a second interpolated signal when said modem receiver is operating in said PSK mode or said PAM mode; delay means for providing said delayed signal by delaying said sampled signal for a second delay time when said modem receiver is operating in said FSK mode, said delay means being connected in series with said first interpolating filter for providing a net delay time, said net delay time being the sum of said first delay time and said second delay time; adaptive equalizer means responsive to said first interpolated signal and said second interpolated signal for providing an equalized signal and equalization coefficients; filter control means responsive to said equalization coefficients for controlling the operation of said first interpolating filter and said second interpolating filter when said modem receiver is operating in said PSK mode or said PAM mode; multiplier means for providing an autocorrelated signal by multiplying said sampled signal by said delayed signal; second filtering means for providing a filtered autocorrelated signal by filtering said autocorrelated signal; decision logic means, responsive to said equalized signal for recovering data represented by said PSK signal when said modem receiver is in said PSK mode, responsive to said equalized signal for recovering data represented by said PAM signal when said modem receiver is in said PAM mode, and responsive to said filtered autocorrelated signal for recovering data represented by said FSK signal when said modem receiver is in said FSK mode; and control means for causing said modem receiver to operate in a selected one of said FSK mode, said PSK mode, or said PAM mode.
Claim 68
Dependent Claim
415 words
A modem receiver for receiving frequency shift keyed (FSK), phase shift keyed (PSK), and phase and amplitude modulated (PAM) signals, comprising: first filtering means for providing a filtered signal by filtering said FSK, PSK, and PAM signals; an analog-to-digital (A/D) converter for providing a sampled signal by sampling and converting said filtered signal; a demodulator for demodulating said PSK and PAM signals to provide in-phase (I) and quadrature phase (Q) signals; a first interpolating filter, responsive to a first predetermined one of said I and Q signals for providing a first interpolated signal when said modem receiver is operating in a PSK mode or a PAM mode, and for providing a delayed signal by delaying said sampled signal for a first delay time when said modem receiver is operating in said FSK mode; a second interpolating filter, responsive to a second predetermined one of said I and Q signals for providing a second interpolated signal when said modem receiver is operating in said PSK mode or said PAM mode; delay means for providing said delayed signal by delaying said sampled signal for a second delay time when said modem receiver is operating in said FSK mode, said delay means being connected in series with said first interpolating filter for providing a net delay time, said net delay time being the sum of said first delay time and said second delay time; adaptive equalizer means responsive to said first interpolated signal and said second interpolated signal for providing an equalized signal and equalization coefficients; filter control means responsive to said equalization coefficients for controlling the operation of said first interpolating filter and said second interpolating filter when said modem receiver is operating in said PSK mode or said PAM mode; multiplier means for providing an autocorrelated signal by multiplying said sampled signal by said delayed signal; second filtering means for providing a filtered autocorrelated signal by filtering said autocorrelated signal; decision logic means, responsive to said equalized signal for recovering data represented by said PSK signal when said modem receiver is in said PSK mode, responsive to said equalized signal for recovering data represented by said PAM signal when said modem receiver is in said PAM mode, and responsive to said filtered autocorrelated signal for recovering data represented by said FSK signal when said modem receiver is in said FSK mode; and control means for causing said modem receiver to operate in a selected one of said FSK mode, said PSK mode, or said PAM mode.
Claim 69
Dependent Claim
16 words
The modem receiver of claim 58 wherein said second filtering means is a low pass filter.
Claim 70
Dependent Claim
22 words
The modem receiver of claim 58 wherein said A/D converter samples and converts said filtered signal at a fixed sampling frequency, FS.
Claim 71
Dependent Claim
17 words
The modem receiver of claim 60 wherein said first delay time is a non-integer multiple of 1/FS.
Claim 72
Dependent Claim
17 words
The modem receiver of claim 61 wherein said second delay time is an integer multiple of 1/FS.
Claim 73
Dependent Claim
28 words
The modem receiver of claim 62 wherein the sum of said first delay time and said second delay time optimizes recovery of data represented by said FSK signal.
Claim 74
Dependent Claim
90 words
The modem receiver of claim 58 and further comprising: selection means for providing a delay selection signal; wherein said first interpolating filter provides a first plurality of delay times and is responsive to said delay selection signal for providing a selected one of said first plurality of delay times as said first delay time; and said delay means provides a second plurality of delay times and is responsive to said delay selection signal for providing a selected one of said second plurality of delay times as said second delay time.
Claim 75
Dependent Claim
43 words
The modem receiver of claim 64 wherein: said A/D converter samples and converts said filtered signal at a fixed sampling frequency, FS; said first delay time is a non-integer multiple of 1/FS; and said second delay time is an integer multiple of 1/FS.
Claim 76
Dependent Claim
28 words
The modem receiver of claim 65 wherein the sum of said first delay time and said second delay time optimizes recovery of data represented by said PSK signal.
Claim 77
Dependent Claim
15 words
The modem receiver of claim 58 wherein said first filtering means is a bandpass filter.
Claim 78
Dependent Claim
61 words
The modem receiver of claim 58 wherein said FSK signal comprises a first signal at a first frequency and a second signal at a second frequency, said first filtering means attenuates said first signal more than said second signal, and the sum of said first delay time and said second delay time optimizes recovery of data represented by said FSK signal.
Claim 79
Dependent Claim
59 words
The modem receiver of claim 68 wherein said filtered autocorrelated signal comprises a filtered autocorrelated first signal and a filtered autocorrelated second signal, and the sum of said first delay time and said second delay time causes said filtered autocorrelated first signal to have a value which is the negative of the value of said filtered autocorrelated second signal.
Claim 80
Dependent Claim
67 words
The modem receiver of claim 58 wherein: said second filtering means provides a predetermined number of samples of said filtered autocorrelated signal per unit of time; said second interpolating filter is interposed between said second filtering means and said decision logic means and said second interpolating filter increases the number of samples per unit of time of said filtered autocorrelated signal provided to said decision logic means.
Claim 81
Dependent Claim
20 words
The modem receiver of claim 70 wherein said second interpolating filter doubles said number of samples per unit of time.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-08-12 | 1995-02-11 | 1995-08-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-08-12 | 1999-02-11 | 1999-08-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-08-12 | 2003-02-11 | 2003-08-13 | $7700.00 | Window Closed / Lapsed |