Patent ID: 7508276

Claim:
A frequency modulator for generating an output signal with a frequency that is a function of a modulation signal, wherein the modulation signal assumes N≧2 different discrete modulation values and a predetermined frequency value of the output signal is associated with each modulation value, the frequency modulator comprising: a closed phase locked loop with a loop filter for providing a first control voltage; a voltage controlled oscillator for generating the output signal; a switchable frequency divider for deriving a frequency-divided signal; a modulation unit that provides, 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, 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 generates the output signal as a function of the first control voltage and the second control voltage, wherein the frequency divider is operatively connected to the first output of the modulation unit and derives the frequency-divided signal so manner that it has substantially instantaneous frequencies that are a function of the divisor values, and wherein the modulation unit has a capacitive voltage divider with a center tap and provides the second control voltage at the center tap.