Method of reconstructing an analog signal, particularly in digital telephony applications, and a circuit device implementing the method
First Claim
1. A method of reconstructing an analog signal previously converted by pulse code modulation to a digital signal, comprising the steps:
- a. subjecting the received digital signal to a digital-to-analog conversion process to produce a first reconstruction of the analog signal, said digital-to-analog conversion process introducing into the frequency spectrum of the first reconstruction a distortion component whose amplitude decreases with increasing frequency,b. subjecting the first reconstruction of the analog signal to low-pass filtering by means of a reconstruction filter including only four integrators with a cut-off frequency Ft to produce a second reconstruction of the analog signal, said four integrators present in said reconstruction filter functioning to remove the distortion component of the first reconstruction, the frequency response of the introduced amplitude distortion component functioning to attenuate the signal above the cut-off frequency Ft.
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Abstract
A method of reconstructing an analog signal, particularly for digital telephony, comprises a first step of digital-to-analog conversion, wherein a first reconstruction of the analog signal is provided by introducing a distortion component into the frequency spectrum whose amplitude decreases with the signal frequency, and a second step of filtering carried out by means of a reconstruction filter provided with integrators and having a cut-off frequency Ft. That attenuating distortion component is utilized instead of one of the integrators in the reconstruction filter, to afford a reduction of the overall design of the circuit device operating in accordance with this method, and bring about, as a result, decreased occupation of the integrated circuit and power dissipation.
104 Citations
8 Claims
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1. A method of reconstructing an analog signal previously converted by pulse code modulation to a digital signal, comprising the steps:
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a. subjecting the received digital signal to a digital-to-analog conversion process to produce a first reconstruction of the analog signal, said digital-to-analog conversion process introducing into the frequency spectrum of the first reconstruction a distortion component whose amplitude decreases with increasing frequency, b. subjecting the first reconstruction of the analog signal to low-pass filtering by means of a reconstruction filter including only four integrators with a cut-off frequency Ft to produce a second reconstruction of the analog signal, said four integrators present in said reconstruction filter functioning to remove the distortion component of the first reconstruction, the frequency response of the introduced amplitude distortion component functioning to attenuate the signal above the cut-off frequency Ft. - View Dependent Claims (2, 3)
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4. A circuit for reconstructing an analog signal previously converted by pulse code modulation to a digital signal in digital telephony, comprising:
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a digital-to-analog converter having an input for receiving the digital signal and producing at an output a first reconstruction of the analog signal, said digital-to-analog converter introducing into the frequency spectrum of the first reconstruction a distortion component whose amplitude decreases with increasing frequency, a low-pass reconstruction filter having an input for receiving the analog signal from the converter, said reconstruction filter having only four integrators with a cut-off frequency Ft producing at an output a second reconstruction of the analog signal, the integrators present in said reconstruction filter functioning to remove the distortion component in the first reconstruction, the frequency response of the introduced amplitude distortion component functioning to attenuate the signal above the cut-off frequency Ft. - View Dependent Claims (5, 6, 7, 8)
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Specification