Patent ID: 8509714

Claim:
A signal transmitting apparatus comprising: a polar coordinate converter that separates and outputs an envelope curve signal which is size information and a phase signal which is phase information from a signal to be transmitted; an up-converter in communication with the polar coordinate converter that up-converts and outputs the phase signal received form the polar coordinate converter; a power amplifier in communication with the up-converter that amplifies and outputs the phase signal output from the up-converter; and a bias modulation unit in communication with the polar coordinate converter and the power amplifier, the bias modulation unit comprising: a first comparator in communication with the polar coordinate converter to compare an analog form of the envelope curve signal received from the polar coordinate converter with a predetermined voltage; and a second comparator in communication with the first comparator and the power amplifier, the bias modulation unit configured to amplify and output the envelope curve signal according to different driving voltages based on a comparison result; wherein the power amplifier amplifies the phase signal output using the envelope curve signal output from the bias modulation unit as a bias voltage, wherein if the analog form of the envelope curve signal is larger than the predetermined voltage, the bias modulation unit amplifies the envelope curve signal according to a first driving voltage, and if the analog form of the envelope curve signal is smaller than the predetermined voltage, the bias modulation unit amplifies the envelope curve signal according to a second driving voltage, the first driving voltage larger than the second driving voltage.