Patent ID: 7595702

Claim:
A modulation apparatus for modulating a phase of an output signal that is output from a voltage controlled oscillator by changing a signal transmitted through a PLL circuit before and after a low-pass filter in the PLL circuit, the modulation apparatus comprising: a monitoring section operable to monitor, after the low-pass filter, control voltage information about a control voltage applied to the voltage controlled oscillator, during any period, when a test signal having a frequency lower than or equal to a frequency band in which a loop gain of the PLL circuit is 0 dB is input at least before the low-pass filter; a correction table storing section operable to associate control voltage information after correction and control voltage information before correction, and store corresponding control voltage information after correction and control voltage information before correction in a correction table, wherein the control voltage information after correction is the control voltage information monitored by the monitoring section and the control voltage information before correction is information about a control voltage applied to the low-pass filter; and a correction section operable to correct the control voltage applied to the voltage controlled oscillator based on the correction table stored in the correction table storing section.