Digital modulator and demodulator system for FDM telephony

Details Digital modulator and demodulator system for FDM telephony Digital modulator and demodulator system for FDM telephony

1975-07-07

1977-01-04

Claffy, Kathleen H.

H04J 104

Patent

active

040015106

ABSTRACT:
A modulating and demodulating system for converting a plurality of baseband space division signals to a frequency division multiplexed signal. The baseband signals are sequentially sampled and converted in an analog-to-digital converter to a series of digital words. Predetermined mathematical algorithms incorporating digital filters, multipliers and shift registers are used to convert the series of digital words to a frequency division multiplexed digital signal. Aliasing of the baseband signals provides the required dispersion through a predetermined frequency range. A digital to analog converter coupled to a conventional balanced mixer and oscillator is then used to up convert the resulting signal to the desired frequency range. A high pass filter is used to remove the image frequencies. The resulting frequency division multiplexed signal may be transmitted by conventional means to a remote location where demodulation is accomplished essentially by reversal of the modulation process.

REFERENCES:
patent: 3605019 (1971-09-01), Cutter
patent: 3773979 (1973-11-01), Kirk
patent: 3875340 (1975-04-01), Roy
patent: 3912870 (1975-10-01), Roy

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