A frequency translating coherent analog to digital conversion system for modulated signals.

摘要

An analog to digital (A/D) conversion system (10 or 20) receives a modulated analog signal, translates the frequency of the signal to a lower frequency, and converts the analog signal to a filtered digital signal. In one form, the conversion system (10) has an analog signal multiplier (16), an A/D converter (18), an oscillator (12), and a frequency divider (14). Frequency multiplier (16) translates the frequency of the analog signal, and A/D converter (18) converts the analog signal to digital form. Frequency divider (14) receives a clock signal from oscillator (12) and divides the frequency of the clock signal. Because the same clock signal is used for frequency translation and analog to digital conversion, a phase error is not introduced in the output digital signal. Additionally, the frequency divider (14) forces the frequencies of the analog and digital signals to be an integer ratio for subsequent demodulation.