Signal generating device

A signal generating device comprising:

• a first digital filter that outputs a first interpolated signal by interpolating an input signal;
• a second digital filter that outputs a second interpolated signal by interpolating the first interpolated signal;
• a phase calculation unit that calculates a phase of a digital signal that changes for each output sampling cycle of the first and second digital filters;
• a phase-accuracy conversion unit that calculates a first phase signal and a second phase signal on a basis of the phase of the digital signal;
• a first memory that stores therein a first filter coefficient of the first digital filter;
• a first coefficient readout unit that reads out the first filter coefficient from the first memory on a basis of the first phase signal and switches the first filter coefficient of the first digital filter;
• a phase-error calculation unit that calculates a phase error signal on a basis of the second phase signal;
• a second memory that stores therein a second filter coefficient of the second digital filter;
• a second coefficient readout unit that reads out the second filter coefficient from the second memory on a basis of the phase error signal;
• and
• a gain normalization unit that switches the second filter coefficient of the second digital filter on a basis of the second filter coefficient read out from the second memory in the second coefficient readout unit.