US 6,674,823 B2 · Variable rate modulator

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.

Claims9

Dependent claims

A signal processing system for converting a variable frequency input signal to an interpolated signal at a fixed sampling frequency, comprising:

a recipient clock providing a recipient clock signal at a recipient clock frequency;
a numerically controlled oscillator responsive to a frequency control signal representing baud rate of the variable frequency input signal and the recipient clock signal for providing a second clock signal at a fixed second clock frequency representing the baud rate of said variable frequency input signal, and a phase offset signal representing an offset in phase between the recipient clock signal and the second clock signal, and
an interpolator that offsets a pair of variable frequency input signals in accordance with the phase offset signal to provide the interpolated signal at the fixed sampling frequency.

Dependencies are inferred from the claim text.

Variable rate modulator

Life of this patent

Variable rate modulator

Life of this patent

Abstract

Claims9