US4675882A
Expired / Lapsed
US
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FM demodulator
Assignee: Motorola Solutions Inc
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Filing: 1985-09-10
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Granted: 1987-06-23
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Expires: 2005-09-10
Abstract
Abstract A digital FM demodulator is described. According to the principles of the present invention, a digital FM signal is demodulated by processing sampled input vectors of a quadrature FM digital signal centered approximately zero frequency. The sampled quadrature input vectors are quantized to lie within a predetermined magnitude range. The quantized vectors are coupled to a phase accumulator which generates a current coarse phase value related to input vectors of the quadrature FM signal. The output of the phase accumulator is also coupled to a vector rotation means which rotates the input vector to a predetermined quadrant to determine a fine phase value based on said rotated input signal vector. The fine and coarse values are then summed and output as a composite phase value, and digitally filtered by subtracting the value of the previous composite phase angle sample from the value of the current composite phase angle sample to produce a demodulated message sample.
Inventors
- 👤 Ross J. Lillie
- 👤 Steven C. Jasper
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 08:55
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/10; H04L27/14; H04L27/156; H04L27/1566
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
191 words
A method of digitally demodulating a received angle-modulated signal, said method comprising the steps of: (a) inputting digitized quadrature samples of a signal centered approximately at zero frequency, said samples indicating a composite signal vector; (b) scaling said samples to a desired magnitude within a predetermined range; (c) calculating the nearest octant within which the scaled composite signal vector lies, said nearest octant comprising a coarse phase range value; (d) rotationally scaling the scaled composite signal vector to lie within a range between -π/4 to +π/4 radians; (e) calculating a second value equal to the tangent of the phase of the rotationally scaled signal vector; (f) calculating a third value equal to the phase angle of said signal vector by deriving the arctangent of said second value, said third value comprising a fine phase angle value; (g) summing the fine phase angle and coarse phase angle values to produce a composite phase angle sample equivalent to the phase angle of the input signal vector; (h) filtering said composite of phase angle samples to produce a sequence of demodulated message samples; and (i) outputting said demodulated message samples to an output register.
Claim 2
Independent Claim
191 words
A method of digitally demodulating a received angle-modulated signal, said method comprising the steps of: (a) inputting digitized quadrature samples of a signal centered approximately at zero frequency, said samples indicating a composite signal vector; (b) scaling said samples to a desired magnitude within a predetermined range; (c) calculating the nearest octant within which the scaled composite signal vector lies, said nearest octant comprising a coarse phase range value; (d) rotationally scaling the scaled composite signal vector to lie within a range between -π/4 to +π/4 radians; (e) calculating a second value equal to the tangent of the phase of the rotationally scaled signal vector; (f) calculating a third value equal to the phase angle of said signal vector by deriving the arctangent of said second value, said third value comprising a fine phase angle value; (g) summing the fine phase angle and coarse phase angle values to produce a composite phase angle sample equivalent to the phase angle of the input signal vector; (h) filtering said composite of phase angle samples to produce a sequence of demodulated message samples; and (i) outputting said demodulated message samples to an output register.
Claim 3
Dependent Claim
131 words
A digital demodulator apparatus having improved linearity, said apparatus comprising: (a) means for inputting a sampled input vector comprising a quadrature signal centered approximately zero frequency; (b) scaler means for quantizing said inputted sampled quadrature signal within a predetermined range; (c) phase accumulator means for generating a current coarse phase value related to input vectors of the quadrature signal; (d) vector rotation means for rotating said input vector to a quadrant within a range between -π/4 to +π/4 radians; (e) means for determining a fine phase value based on said rotated input signal vector; (f) summing means for summing said fine and coarse phase values and outputting a composite phase value; and (g) filtering means for filtering said composite of phase angle samples to produce a sequence of demodulated message samples.
Claim 4
Dependent Claim
131 words
A digital demodulator apparatus having improved linearity, said apparatus comprising: (a) means for inputting a sampled input vector comprising a quadrature signal centered approximately zero frequency; (b) scaler means for quantizing said inputted sampled quadrature signal within a predetermined range; (c) phase accumulator means for generating a current coarse phase value related to input vectors of the quadrature signal; (d) vector rotation means for rotating said input vector to a quadrant within a range between -π/4 to +π/4 radians; (e) means for determining a fine phase value based on said rotated input signal vector; (f) summing means for summing said fine and coarse phase values and outputting a composite phase value; and (g) filtering means for filtering said composite of phase angle samples to produce a sequence of demodulated message samples.
Claim 5
Independent Claim
201 words
A method of digitally demodulating a received frequency modulated signal, said method comprising the steps of: (a) inputting digitized quadrature samples of a signal centered approximately at zero frequency, said samples indicating an input signal vector; (b) scaling said samples to a desired magnitude within a predetermined range; (c) calculating the nearest octant within which the scaled signal vector lies, said nearest octant comprising a coarse phase value range; (d) rotationally scaling the scaled signal vector to lie within a range between -π/4 to +π/4 radians; (e) calculating a second value equal to the tangent of the phase of the rotationally scaled signal vector; (f) calculating a third value equal to the phase angle of said signal vector by deriving the arctangent of said second value, said third value comprising a fine phase angle value; (g) summing the fine phase angle and coarse phase angle values to produce a composite phase angle sample equivalent to the phase angle of the input signal vector; (h) subtracting the value of the previous composite phase angle sample from the value of the current composite phase angle sample to produce a demodulated message sample; and (i) outputting said demodulated message sample to an output register.
Claim 6
Independent Claim
201 words
A method of digitally demodulating a received frequency modulated signal, said method comprising the steps of: (a) inputting digitized quadrature samples of a signal centered approximately at zero frequency, said samples indicating an input signal vector; (b) scaling said samples to a desired magnitude within a predetermined range; (c) calculating the nearest octant within which the scaled signal vector lies, said nearest octant comprising a coarse phase value range; (d) rotationally scaling the scaled signal vector to lie within a range between -π/4 to +π/4 radians; (e) calculating a second value equal to the tangent of the phase of the rotationally scaled signal vector; (f) calculating a third value equal to the phase angle of said signal vector by deriving the arctangent of said second value, said third value comprising a fine phase angle value; (g) summing the fine phase angle and coarse phase angle values to produce a composite phase angle sample equivalent to the phase angle of the input signal vector; (h) subtracting the value of the previous composite phase angle sample from the value of the current composite phase angle sample to produce a demodulated message sample; and (i) outputting said demodulated message sample to an output register.
Claim 7
Dependent Claim
149 words
A digital frequency modulation demodulator apparatus having improved linearity, said apparatus comprising: (a) means for inputting a sampled input vector comprising a quadrature of frequency modulation digital signal centered approximately zero frequency; (b) scaler means for quantizing said inputted sampled quadrature signal within a predetermined range; (c) phase accumulator means for generating a current coarse phase value related to input vectors of the quadrature FM signal; (d) vector rotation means for rotating said input vector to a quadrant within a range between -π/4 to +π/4 radians; (e) means for determining a fine phase value based on said rotated input signal vector; (f) summing means for summing said fine and coarse phase values and outputting a composite phase value; and (g) filtering means for subtracting the value of the previous composite phase angle sample from the value of the current composite phase angle sample to produce a demodulated message sample.
Claim 8
Dependent Claim
149 words
A digital frequency modulation demodulator apparatus having improved linearity, said apparatus comprising: (a) means for inputting a sampled input vector comprising a quadrature of frequency modulation digital signal centered approximately zero frequency; (b) scaler means for quantizing said inputted sampled quadrature signal within a predetermined range; (c) phase accumulator means for generating a current coarse phase value related to input vectors of the quadrature FM signal; (d) vector rotation means for rotating said input vector to a quadrant within a range between -π/4 to +π/4 radians; (e) means for determining a fine phase value based on said rotated input signal vector; (f) summing means for summing said fine and coarse phase values and outputting a composite phase value; and (g) filtering means for subtracting the value of the previous composite phase angle sample from the value of the current composite phase angle sample to produce a demodulated message sample.
References Cited (Backward Citations)
US3949301A
Cited
US4311964A
Cited
US4379284A
Cited
US4317210A
Cited
US4506228A
Cited
US4514697A
Cited
US4577157A
Cited
US4539524A
Cited
US4563650A
Cited
US4560941A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-06-22 | 1990-12-22 | 1991-06-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-06-22 | 1994-12-22 | 1995-06-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-06-22 | 1998-12-22 | 1999-06-23 | $7700.00 | Window Closed / Lapsed |