Variable rate modulator
First Claim
1. A signal processing system for converting a variable frequency input signal to a fixed frequency output signal comprising:
- means for generating a first clock signal at a first clock frequency;
means for receiving a frequency control signal that corresponds to a second frequency;
means for generating a second clock signal at the second frequency as a function of said frequency control signal;
means for generating a phase offset signal representing an offset in phase between the first clock signal and the second clock signal; and
means for converting the variable frequency input signal to an interpolated signal at a fixed sampling frequency in accordance with said phase offset signal, wherein the interpolated signal is interpolated by a value of M/N where M and N are integers.
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Abstract
Digital data signals at a variable input frequency are converted by a numerically controlled oscillator and an interpolator to a signal at a fixed output sampling frequency. The conversion of the variable input frequency to the fixed output sampling frequency may be by a factor other than an integer. The interpolated digital data signals at the fixed output sampling frequency are then modulated into a pair of trigonometric signals at a programmable carrier frequency, one signal having a cosine function and the other signal having a sine function. The modulated signals at the fixed output sampling frequency are then combined to create a modulated signal at a carrier frequency determined by the frequency of the sine and cosine signals. The modulated signal is sampled at the fixed output sampling frequency and converted to a corresponding analog signal using a digital-to-analog converter.
29 Citations
12 Claims
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1. A signal processing system for converting a variable frequency input signal to a fixed frequency output signal comprising:
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means for generating a first clock signal at a first clock frequency;
means for receiving a frequency control signal that corresponds to a second frequency;
means for generating a second clock signal at the second frequency as a function of said frequency control signal;
means for generating a phase offset signal representing an offset in phase between the first clock signal and the second clock signal; and
means for converting the variable frequency input signal to an interpolated signal at a fixed sampling frequency in accordance with said phase offset signal, wherein the interpolated signal is interpolated by a value of M/N where M and N are integers. - View Dependent Claims (2, 3, 4)
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5. A signal processing system for converting a variable frequency input signal to an output signal having a fixed output frequency, comprising:
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means for generating a clock signal at a clock frequency equal to baud rate of said variable frequency input signal as a function of a frequency control signal;
means for generating a phase offset signal representing an offset in phase between a recipient clock signal and the clock signal; and
means for converting the variable frequency input signal to an interpolated signal at a fixed sampling frequency in accordance with said phase offset signal, wherein the interpolated signal is interpolated by a value of M/N where N and N are integers.
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6. A signal processing system, comprising:
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means for providing a first clock signal at a first clock frequency;
oscillator means, responsive to a frequency control signal and the first clock signal for providing an output clock signal at a fixed second clock frequency and a phase offset signal representing an offset in phase between the first clock signal and the second clock signal, and interpolation means for offsetting a pair of variable frequency input signals in accordance with the phase offset signal to provide an interpolated signal at a fixed output sampling frequency, wherein the interpolated signal is interpolated by a value of M/N where M and N are integers. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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Specification