| 摘要 |
A frequency modulator is provided for generating an output signal with a frequency that is a function of a modulation signal, wherein the modulation signal can assume N>=2 different discrete modulation values, and a predetermined frequency value of the output signal is associated with each modulation value, containing: a) a closed phase locked loop with a loop filter for providing a first control voltage, with a voltage controlled oscillator for generating the output signal, and with a switchable frequency divider for deriving a frequency-divided signal, and b) a modulation unit that is designed to provide, at a first output, values of a divisor that are a function of the modulation signal, and at a second output, a second control voltage that is a function of the modulation signal, c) wherein the oscillator has a first control input connected to the loop filter and has a second control input connected to the second output of the modulation unit, and is designed to generate the output signal as a function of the first control voltage and the second control voltage, d) and wherein the frequency divider is connected to the first output of the modulation unit and is designed to derive the frequency-divided signal in such a manner that it has instantaneous frequencies that are a function of the divisor values. According to the invention, the modulation unit has a capacitive voltage divider with a center tap and is designed to provide the second control voltage at the center tap. The invention further concerns a transmitting/receiving device and an integrated circuit having such a frequency modulator.
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