Pulse or digital communications – Transmitters – Angle modulation
Patent
1994-03-04
1996-09-10
Chin, Stephen
Pulse or digital communications
Transmitters
Angle modulation
375376, 332100, 332128, H03C 300, H04L 2712
Patent
active
055552765
ABSTRACT:
A programmable apparatus is disclosed for generating a frequency modulated signal all 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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"Service Manual, LTR 8800 Mobile and Control Station 5-20 Channel, 816-821 MHz, Transmit, 861-866 MHz Receive 25 Watts RF Output"; Copyright 1980, E. F. Johnson Company pp. 1-1 through 8-10.
Frede William W.
Koenck Steven E.
Mahany Ronald L.
Chin Stephen
Gable R. Lewis
Norand Corporation
Vo Don
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