Disclosed herein is a signal processing apparatus including: a frequency multiplier configured to carry out an N-times frequency multiplication process on a modulated signal obtained as a result of an N phase shift keying modulation process in order to generate a multiplied frequency signal; and an oscillator configured to oscillate the multiplied frequency signal as an injected signal in order to generate a signal obtained by carrying out a by-N frequency division process on the multiplied frequency signal to serve as a reproduced carrier which is a carrier reproduced from the modulated signal.