EP0262842A2
Expired / Lapsed
EP
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FSK Modem
Assignee: HYCOM Inc
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Filing: 1987-09-17
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Granted: —
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Expires: 2007-09-17
Abstract
Abstract The number of multiplies per second required in a digital FSK modem receiver using a tracking phase lock loop demodulator (20) is greatly reduced by using an 800 Hz sampling rate band pass filter (16) to isolate the carrier and its sidebands, operating the phase lock loop demodulator (20) at the 800 Hz sample rate which is just sufficient to satisfy Nyquist's theory for the frequency band passed by the filter, and interpolating the detected data samples by using 7200 Hz sampling low pass filter (36) in the output.
Inventors
- 👤 David M. Motley
- 👤 John F. Stockman
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 05:35
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/14; H04L27/144; H04L27/152
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
143 words
A digital FSK modem, comprising: (a) band pass filter means (16) for retrieving, from a digitized input signal, the frequency band containing the carrier and its sidebands, said band pass filter means (16) having a real input at an up sample rate, and a complex output at a lower down sample rate; (b) demodulator detector means (20) connected to said band pass filter means (16) for demodulating the output of said band pass filter means (16) and deriving therefrom data signals representative of the logic level of data contained in said input signal, said demodulator/detector means (20) being operated at said down sample rate; and (c) low pass filter means (36) connected to said demodulator/detector means (20) for interpolating said data signals, said low-pass filter means (36) having an input at said down sample rate and an output at said up sample rate.
Claim 2
Dependent Claim
143 words
A digital FSK modem, comprising: (a) band pass filter means (16) for retrieving, from a digitized input signal, the frequency band containing the carrier and its sidebands, said band pass filter means (16) having a real input at an up sample rate, and a complex output at a lower down sample rate; (b) demodulator detector means (20) connected to said band pass filter means (16) for demodulating the output of said band pass filter means (16) and deriving therefrom data signals representative of the logic level of data contained in said input signal, said demodulator/detector means (20) being operated at said down sample rate; and (c) low pass filter means (36) connected to said demodulator/detector means (20) for interpolating said data signals, said low-pass filter means (36) having an input at said down sample rate and an output at said up sample rate.
Claim 3
Dependent Claim
19 words
A modem according to claim 1, characterised in that said demodulator/detector means (20) include a tracking phase lock loop.
Claim 4
Dependent Claim
36 words
A modem according to claim 1 or 2, characterised in that said demodulator/detector means further includes means (22,24) for deriving from said band pass filter output a carrier signal representative of the presence of the carrier.
Claim 5
Dependent Claim
26 words
A modem according to claim 2, characterised in that said tracking phase lock loop includes a complex multiplier (18) to produce said carrier and data signals.
References Cited (Backward Citations)
No citation records indexed.
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