US4412181A
Expired / Lapsed
US
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Process for the demodulation of an amplitude modulated signal and demodulator performing this process
Assignee: Thales SA
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Filing: 1981-03-27
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Granted: 1983-10-25
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Expires: 2001-03-27
Abstract
Abstract A process for the demodulation of an amplitude modulated signal composed of two suppressed carriers, at a same frequency F and in phase quadrature, which are respectively modulated by two modulation signals, the modulated signal being preceded by a reference signal at frequency F, by sampling the reference signal and the modulated signal, according to a frequency m.F (m being an integer); determining a polar angle ψ t of a rotating vector representing the reference signal, at time t, by calculating: ##EQU1## where x(t) and x(t-(1/4F)) are the values of two successive samples of the reference signal; determining polar coordinates (ρ t , θ t ) of a rotating vector representing the modulated signal, at time t, by calculating: ##EQU2## where y(t) and y(t-(1/4F)) are values of two successive samples of the modulated signal, calculating γ=θ t -ω t -φ o , where φ o is the phase displacement between the reference signal and one of the carriers, calculating α=ρ t .cos γ β=ρ.sub.t.sin γ and generating two signals whose instantaneous amplitudes are α and λβ.
Inventors
- 👤 Andre Marguinaud
- 👤 Gerard Sorton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 18:41
CPC Classifications
H; H03; H03D; H03D1/00; H04; H04N; H04N11/00; H04N11/06; H04N11/12; H04N11/14; H04N11/16; H04N11/165
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
141 words
A process for the demodulation of an amplitude modulated signal composed of two suppressed carriers, at a same frequency F and in phase quadrature, which are respectively modulated by two modulation signals, comprising the steps of: determining polar coordinates (ρ t , θ t ) of a rotating vector representing the modulated signal, at time t, by calculating: ##EQU20## where y(t) and y(t-(1/4F) are values of two successive samples of the modulated signal; calculating a value γ of the difference between the polar angle θ t of the rotating vector representing the modulated signal and the polar angle of a rotating vector representing a reference signal at a frequency F; calculating values α and β of the instantaneous amplitudes of the modulation signals according to the formulas: α=ρ.sub.t.cos γ β=ρ.sub.t.sin γ generating two signals whose instantaneous amplitudes are α and β.
Claim 2
Dependent Claim
141 words
A process for the demodulation of an amplitude modulated signal composed of two suppressed carriers, at a same frequency F and in phase quadrature, which are respectively modulated by two modulation signals, comprising the steps of: determining polar coordinates (ρ t , θ t ) of a rotating vector representing the modulated signal, at time t, by calculating: ##EQU20## where y(t) and y(t-(1/4F) are values of two successive samples of the modulated signal; calculating a value γ of the difference between the polar angle θ t of the rotating vector representing the modulated signal and the polar angle of a rotating vector representing a reference signal at a frequency F; calculating values α and β of the instantaneous amplitudes of the modulation signals according to the formulas: α=ρ.sub.t.cos γ β=ρ.sub.t.sin γ generating two signals whose instantaneous amplitudes are α and β.
Claim 3
Dependent Claim
101 words
A process for the demodulation according to claim 1, the modulated signal being preceded by a reference signal at frequency F, comprising furthermore the steps of: sampling the reference signal according to the frequency m.F (m being an integer); determining a polar angle ψ t of a rotating vector representing the reference signal, at time t, by calculating: ##EQU21## where x(t) and x(t-(1/4F) are the values of two successive samples of the reference signal; calculating γ by the formula: γ=θ t -ψ t -φ o where ψ o is the phase displacement between the reference signal and one of the carriers.
Claim 4
Dependent Claim
133 words
A demodulator, using the process according to claim 2, comprising: a sampler, for sampling the modulated signal at a frequency m.F, having an output; an analog-digital converter having an input connected to the output of the sampler; a delay element, of delay equal to 1/m.F, having an input connected to the output of the converter and having an output; first calculating means for calculating the polar coordinates (ρ t , θ t ), having two inputs respectively connected to the output of the converter and to the output of the delay element, and having two outputs; and second calculating means, for calculating the values α and β of the amplitudes of the two modulation signals, having two inputs respectively connected to the two outputs of the first calculating means and having two outputs.
Claim 5
Dependent Claim
73 words
A demodulator according to claim 3, wherein m is equal to 4; wherein the first calculating means comprise a first and a second calculating device each having two inputs respectively connected to the two inputs of the first calculating means and receiving respectively values y(t) and y(t-1/4F), and having two outputs, for calculating the values ρ t and θ t according to formulas: ##EQU22## and supplying these values at the two outputs respectively.
Claim 6
Dependent Claim
163 words
A demodulator according to claim 4, comprising furthermore means for detecting a reference signal preceding the modulated signal, having two inputs respectively connected to the outputs of the first calculating means and having an output; and wherein the second calculating means comprise: a first calculating device having a first input connected to the output of the means for detecting a reference signal, a second input connected to the output of the first calculating means supplying the value θ t , and an output, for calculating a value γ in accordance with the formula γ=θ t -ψ t -φ o ; a second calculating device having a first input connected to the output of the first calculating means supplying the value ρ t , a second input connected to the output of the first calculating device of the second calculating means and receiving the value γ, and having two outputs, for calculating α and β in accordance with the formulas: α=ρ.sub.t.cos γ β=ρ.sub.t.sin γ.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1986-10-24 | 1987-04-25 | 1987-10-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-10-24 | 1991-04-25 | 1991-10-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-10-24 | 1995-04-25 | 1995-10-25 | $7700.00 | Window Closed / Lapsed |