Signal synthesis apparatus and method capable of correcting 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 by comprising a modulation cap bank having a plurality of capacitors of the same capacitance and an inductor, and to modulate a frequency of the output signal according to a connection state of the capacitors of the modulation cap bank and the inductor to output a frequency-modulated signal;
• 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 control the operation mode of the VCO input selector and to transmit a modulation control signal for adjusting the connection state of the capacitors of the modulation cap bank to the VCO, 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
• a modulation control signal offset determinator configured to determine an offset of the modulation control signal to compensate for the frequency offset based on a frequency change value according to a predetermined modulation control signal.