Low cost digital FM modulator
AssigneeSTMicroelectronics S.r.l.
InventorPascal Mellot
Life of this patent
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Abstract
A modulator including a noise shaper receiving the input signal and providing a signal coded over one bit, a phase loop including an adder and a shift register. The adder receives the signal coded over one bit, the output of the shift register, and a constant. The input of the shift register receives the adder output. A sinusoidal shaper is coupled to the output of the shift register to provide a signal modulated in frequency by the input signal. The present invention also relates to a modulation chain including a modulator.
Claims17
A modulator to implement a frequency modulation by means of a digital input signal coded over a first predetermined number of bits and sampled at a first frequency, including:
- a noise shaper receiving the digital input signal and providing, based thereon, a signal coded over one bit,
- a phase loop including an adder and a shift register, the adder receiving said signal coded over one bit, an output of the shift register, and a constant, the shift register receiving the adder output, and
- a sinusoidal shaper coupled to the output of the shift register to provide a signal modulated in frequency by the input signal.
A method of frequency modulating a carrier signal with a first digital signal having a first frequency and coded over a first plurality of bits, the method comprising acts of:
- noise shaping the first digital signal coded over the first plurality of bits into a second digital signal coded over one bit;
- summing together a feedback signal, a constant signal and the second digital signal to provide a summed signal;
- shifting the summed signal at a drive frequency to provide the feedback signal and a first modulated signal;
- and
- shaping the first modulated signal into a frequency modulated signal modulated in frequency by the first digital signal.
Dependencies are inferred from the claim text.