Device and method for signal synthesis compensating the frequency offset of open loop

A signal synthesis apparatus configured to correct an offset between a closed loop and an open loop to output a frequency-modulated signal, the signal synthesis apparatus comprising:

• a voltage-controlled oscillator (VCO) configured to generate an output signal having a frequency corresponding to an input voltage;
• an energy storage unit configured to store energy using an input voltage and to output a voltage based on the stored energy;
• a VCO input selector configured to connect an input unit of the VCO to input of the energy storage unit when an operation mode is a closed loop mode, and to connect the input unit of the VCO to output of the energy storage unit when the operation mode is an open loop mode;
• and
• a digital controller configured to control the operation mode of the VCO input selector and to transmit an offset control signal for adjusting an offset voltage of a voltage output from the energy storage unit to the energy storage unit, wherein the digital controller comprises:
• a frequency offset calculator configured to calculate a frequency offset based on a difference between a closed loop mode frequency of a VCO output signal output from the VCO when the VCO input selector operates in the closed loop mode and an open loop mode frequency of the VCO output signal output from the VCO when the VCO input selector operates in the open loop mode;
• and
• an offset control signal determinator configured to determine an offset control signal to compensate for the frequency offset based on a frequency change value according to a predetermined offset control signal.