Method of and apparatus for controlling modulation of digital si

Details Method of and apparatus for controlling modulation of digital si Method of and apparatus for controlling modulation of digital si

1996-09-10

1999-06-15

Chin, Stephen

Pulse or digital communications

Transmitters

375295, 375302, 375303, 375219, 375223, 375376, 331 9, 331 10, 332100, 332123, 332127, 332128, H04L 2704, H04L 2712, H04L 2720

Patent

active

059129263

ABSTRACT:
A programmable apparatus is disclosed for generating a frequency modulated signal at a selected center frequency in accordance with digital data of at least first and second data levels. The modulating apparatus comprises a modulator having an input and an output and is responsive to an input modulation signal applied to its input for generating at its output the frequency modulated signal at a center frequency dependent on a quiescent voltage appearing at its input. A circuit is provided for sampling and storing a value of the quiescent voltage. An addressable memory stores a plurality of offsets. A programmable adding circuit adds a downloaded offset voltage to the stored value of the quiescent voltage to output a high modulation voltage. A programmable subtracting circuit subtracts a downloaded offset voltage from the stored value of the quiescent voltage to provide a low modulation voltage. An addressing circuit addresses the memory in accordance with a data transmission parameter for downloading a corresponding offset to the adding and subtracting circuits. A switch or multiplexor is coupled to the subtracting and adding circuits and to receive the digital data for generating and applying to the modulator input an input modulation signal comprising a sequence of the high and low modulation voltages in accordance respectively with the first and second data levels of the digital data.

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