Patent ID: 7180385

Claim:
A frequency modulation system, comprising: a first input connection configured to supply modulation data; a second input connection configured to supply a channel pre-selection signal; a linking element comprising two inputs coupled to the first and second input connections of the frequency modulation system, and an output, and configured to provide a division control signal that is a function of the modulation data and the pre-selection signal; and a phase locked loop, comprising: an oscillator having a control input configured to control an output carrier frequency signal of the oscillator, and an output providing the output carrier frequency signal; a step-up frequency mixer comprising a first input coupled to the first input connection and configured to receive the modulation data, and a second input coupled to the output of the oscillator, wherein the step-up frequency mixer is configured to output a modulation signal at a transmission frequency that is a function of the modulation data and the output carrier frequency signal; a phase comparator configured to compare a reference frequency signal to a feedback frequency signal that is a function of the transmission frequency modulation signal, and having an output coupled to the control input of the oscillator, wherein the phase comparator is configured to compare the reference frequency signal and the feedback frequency signal and output a control signal in response thereto at an the output thereof to control the output carrier frequency of the oscillator; and a feedback path connected to an output of the step-up frequency mixer and to an input of the phase comparator, the feedback path comprising a frequency divider having a control input coupled to the output of the linking element, wherein the frequency divider is configured to divide down the transmission frequency modulation signal based on the division control signal to produce the feedback frequency signal.